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Sequence stratigraphy after the demise of a high-relief carbonate platform (Carnian of the Dolomites): Sea-level and climate disentangled
Abstract
Sedimentary facies analysis aided by quantitative 3D georeferenced field data are applied to constrain the sequence stratigraphy of a complex stratigraphic interval in the Late Triassic of the Dolomites. This multidisciplinary approach was the key to disentangle the timing of climatic change vs. sea-level fluctuation and their effects on shallow water carbonate depositional systems. The “Carnian Pluvial Event”, a global episode of climate change worldwide documented at low latitudes, involved increased rainfall and possibly global warming. This climatic event begins before a drop of sea-level and caused the demise of microbial-dominated high-relief carbonate platforms that dominated the Dolomites region, and was followed by a period of coexistence of small microbial carbonate mounds and arenaceous skeletal-oolitic grainstones. A subsequent sea-level fall brought to the definitive disappearance of microbialites and shallow water carbonates switched to ramps dominated by oolitic-bioclastic grainstones. The crisis of early Carnian shallow water carbonate systems of the Dolomites generated a geological surface similar to a drowning unconformity, although no transgression occurred. As the high-relief microbial carbonate systems characterized by steep slopes switched to gently inclined oolitic-skeletal-siliciclastic ramps, basins were rapidly filled. The change of carbonate depositional systems was associated with an increase in siliciclastic input, in turn triggered by the onset of a humid climatic event and only later to a sea-level drop. This evolution of carbonate systems cannot be interpreted in the light of sea-level changes only: climate change, and consequent ecological changes in the main carbonate producing biotas, induced significant modifications in depositional geometries. This case study may serve as a conceptual model for the sedimentary evolution of carbonate systems subject to ecological crisis that do not evolve in platform drowning because, despite a drop in shallow water carbonate production, a combination of low subsidence and/or sea level drop maintains the platform top at shallow depth.
... 1B). While in this basinal succession the evidence of a crisis of the carbonate factories (Cassian Platforms) at the NCIE-1 is evident in a sharp change in the composition of shallow water carbonates (Stefani et al., 2010;Dal Corso et al., 2015;Gattolin et al., 2015;Jin et al., 2020), a coeval sedimentological evidence of an intensification of the hydrological cycle is less obvious, and it actually appears to have been slightly delayed, being clearly visible only higher up in the sequence with the deposition of coarse siliciclastic material between the first and the second NCIEs, and the formation of "humid" paleosols containing amber (Borca Mb; Breda et al., 2009). Moreover, the interplay of different processes (e.g., sea-level changes and changes in the sediment-source) could have controlled siliciclastic sedimentation during different phases of the CPE (cf., Franz et al., 2014;Gattolin et al., 2015;Jin et al., 2022). ...
... While in this basinal succession the evidence of a crisis of the carbonate factories (Cassian Platforms) at the NCIE-1 is evident in a sharp change in the composition of shallow water carbonates (Stefani et al., 2010;Dal Corso et al., 2015;Gattolin et al., 2015;Jin et al., 2020), a coeval sedimentological evidence of an intensification of the hydrological cycle is less obvious, and it actually appears to have been slightly delayed, being clearly visible only higher up in the sequence with the deposition of coarse siliciclastic material between the first and the second NCIEs, and the formation of "humid" paleosols containing amber (Borca Mb; Breda et al., 2009). Moreover, the interplay of different processes (e.g., sea-level changes and changes in the sediment-source) could have controlled siliciclastic sedimentation during different phases of the CPE (cf., Franz et al., 2014;Gattolin et al., 2015;Jin et al., 2022). These observations are possible in the Dolomites because of increasing resolution of the stratigraphy and extensive detailed geological mapping of the entire area in recent years, which have led to the definition of the Alpe di Specie Mb of the Heiligkreuz Fm , and better understanding of the Carnian stratigraphy (e.g., Russo et al., 1991;De Zanche et al., 1993;Keim et al., , 2006Neri et al., 2007;Stefani et al., 2010;Roghi et al., 2010;Dal Corso et al., 2012, 2018Gattolin et al., 2015). ...
... Moreover, the interplay of different processes (e.g., sea-level changes and changes in the sediment-source) could have controlled siliciclastic sedimentation during different phases of the CPE (cf., Franz et al., 2014;Gattolin et al., 2015;Jin et al., 2022). These observations are possible in the Dolomites because of increasing resolution of the stratigraphy and extensive detailed geological mapping of the entire area in recent years, which have led to the definition of the Alpe di Specie Mb of the Heiligkreuz Fm , and better understanding of the Carnian stratigraphy (e.g., Russo et al., 1991;De Zanche et al., 1993;Keim et al., , 2006Neri et al., 2007;Stefani et al., 2010;Roghi et al., 2010;Dal Corso et al., 2012, 2018Gattolin et al., 2015). ...
A higher precipitation regime during the early Late Triassic Carnian Pluvial Episode (CPE; 232–234 Ma) in many marine basins is evidenced by thick siliciclastic deposits, which are coeval with C-cycle perturbations and global warming. However, the mechanisms driving higher siliciclastic deposition are still not fully explored and could be linked to different effects of the climate change on depositional environments. Here, we present the first major, minor and trace elements, and mineralogical data from fine-grained sediments across the CPE in the Dolomites (Southern Alps, Western Tethys). Combining weathering indices (CPA and Rb/K2O), and qualitative and quantitative mineralogical analysis, we recognize two main phases during the CPE. Pre-CPE conditions show no significant weathering variations and some peaks of clay minerals referable to the weathering of Ladinian igneous material. The first C-isotope excursion of the CPE is coincident with an increase of CPA, Rb/K2O and kaolinite, with no change in the sediment-source and depositional setting, that indicate an enhancement of chemical weathering and confirm a shift to more humid conditions at the onset of the CPE. Such a signal from the Dolomites can be correlated with other similar observations from marine and terrestrial settings worldwide. After this first phase, a major sea level fall, probably linked to aquifer-eustasy and/or limno-eustatism, and following important transgression led to the erosion and recycling of older rocks marked by a decoupling of CPA and Rb/K2O and a substantial increase of K-feldspar from older volcanic rocks. The eustatic signal overwhelmed the humid climatic signal that is inferred by independent palynological and paleosol data within the same interval. After the CPE, data show high physical weathering under arid climate. Our results are compatible with the general view that the CPE was linked to injections of volcanic CO2 from Large Igneous Province activity and consequent global warming and enhanced hydrological cycle, which first intensified rock chemical weathering at the onset of the CPE, then promoted higher storage of freshwater on land and a substantial increase of erosion and transport of unweathered material into the basins of the western Tethys that were rapidly infilled.
... This suggests multiple injections of 13 C-depleted carbon into the Carnian atmosphere-ocean system that repeatedly enhanced the hydrological cycle, leading to the massive transport of siliciclastic material into the basins . At the CPE, a sudden reduction of carbonate precipitation in shallow water environments of western Tethys is also observed (Schlager and Schöllnberger, 1974;Simms and Ruffell, 1989;Preto and Hinnov, 2003;Keim, Spötl, and Brandner, 2006;Hornung, Krystyn, and Brandner, 2007;Stefani, Furin, and Gianolla, 2010), and is accompanied by a Tethys-wide switch from microbial to metazoan factories (Gattolin et al., 2015;Dal Corso et al., 2015Jin et al., 2020). Preto, Willems, Guaiumi, and Westphal (2013) proposed that the rise of calcispheres, which they observed after the CPE, could have been triggered by increasing seawater alkalinity and supersaturation due to enhanced supply of bicarbonate from rivers, coupled to reduced shallow-water carbonate precipitation. ...
... This could point to an important external causal factor, like profound changes in the global biogeochemistry of the ocean, that drove dinoflagellates first, and then other planktonic organisms, to secrete calcium carbonate tests/walls. The CPE is marked by massive changes in the carbonate cycle: a sudden reduction of carbonate precipitation in shallow water environments, widespread change in the platform carbonate factories from microbial-dominated to metazoan-dominated (Schlager and Schöllnberger, 1974;Simms and Ruffell, 1989;Preto and Hinnov, 2003;Keim, Spötl, and Brandner, 2006;Hornung, Krystyn, and Brandner, 2007;Stefani, Furin, and Gianolla, 2010;Gattolin et al., 2015;Dal Corso et al., 2015Jin et al., 2019), widespread and abundant ooids formation, and abundant cement precipitation (Gattolin et al., 2015). This pattern suggests modifications in the carbonate saturation state of the Ocean. ...
... This could point to an important external causal factor, like profound changes in the global biogeochemistry of the ocean, that drove dinoflagellates first, and then other planktonic organisms, to secrete calcium carbonate tests/walls. The CPE is marked by massive changes in the carbonate cycle: a sudden reduction of carbonate precipitation in shallow water environments, widespread change in the platform carbonate factories from microbial-dominated to metazoan-dominated (Schlager and Schöllnberger, 1974;Simms and Ruffell, 1989;Preto and Hinnov, 2003;Keim, Spötl, and Brandner, 2006;Hornung, Krystyn, and Brandner, 2007;Stefani, Furin, and Gianolla, 2010;Gattolin et al., 2015;Dal Corso et al., 2015Jin et al., 2019), widespread and abundant ooids formation, and abundant cement precipitation (Gattolin et al., 2015). This pattern suggests modifications in the carbonate saturation state of the Ocean. ...
It has been argued that the beginning of significant pelagic calcification could have been linked to the Carnian Pluvial Episode (CPE), a climate change in the Late Triassic (~234–232 Ma) that was marked by C-cycle disruption and global warming. Nevertheless, abundant calcareous nannofossils have been described so far only in post-CPE rocks, and therefore no conclusive hypotheses can be drawn on possible causal links with it. Here we show that in deep-water successions of the Western Tethys, Orthopithonella calcispheres interpreted as calcareous dinocysts became an important component of carbonate sedimentation from the onset of the CPE, and could constitute up to 8% of hemipelagic limestones. Before the CPE, in similar depositional environments, calcispheres are rare or absent, and never constitute a significant part of the sediment. This change in the deep-water carbonate sedimentation, is mirrored in the shallow water environments by the rise of the reefs built by Scleractinia corals. These important innovations in Earth's carbonate systems may indicate a deep modification in the ocean biogeochemistry during the CPE.
... During the CPE, a major change in shallow carbonate systems saw the shift from microbially dominated carbonate-producing ecosystems (carbonate factories) to less productive metazoan-dominated ecosystems, with the appearance of modern-style scleractinian coral reefs (see also the discussion below on the CPE marine biological changes). This coincided with the first C-isotope excursion at the onset of the CPE (5,23). The crisis of the Middle Triassic-early Carnian carbonate factories during the CPE was at least Tethys wide (2,7,20,24). ...
... For the 13 C and T records, refer to Fig. 1. where reefs from the Middle Triassic to early Carnian were constructed by microbes that formed up to 70% of framework carbonate (23). This microbial carbonate production reduced abruptly at the onset of the CPE, and the carbonate factory was replaced by carbonate ramps that hosted metazoan patch reefs with abundant scleractinian corals (5,23,55). ...
... where reefs from the Middle Triassic to early Carnian were constructed by microbes that formed up to 70% of framework carbonate (23). This microbial carbonate production reduced abruptly at the onset of the CPE, and the carbonate factory was replaced by carbonate ramps that hosted metazoan patch reefs with abundant scleractinian corals (5,23,55). This change in the carbonate factory is best seen in the Italian Dolomites, but it occurred worldwide, with evidence of similar changes from China (7), Turkey (56), and northern India (20). ...
The Carnian Pluvial Episode (Late Triassic) was a time of global environmental changes and possibly substantial coeval volcanism. The extent of the biological turnover in marine and terrestrial ecosystems is not well understood. Here, we present a meta-analysis of fossil data that suggests a substantial reduction in generic and species richness and the disappearance of 33% of marine genera. This crisis triggered major radiations. In the sea, the rise of the first scleractinian reefs and rock-forming calcareous nannofossils points to substantial changes in ocean chemistry. On land, there were major diversifications and originations of conifers, insects, dinosaurs, crocodiles, lizards, turtles, and mammals. Although there is uncertainty on the precise age of some of the recorded biological changes, these observations indicate that the Carnian Pluvial Episode was linked to a major extinction event and might have been the trigger of the spectacular radiation of many key groups that dominate modern ecosystems.
... The CPE is mainly characterized by continental siliciclastic input and by a crisis of shallow-water carbonate production in the margins of Tethys (Schlager and Schöllnberger, 1974;De Zanche et al., 2000;Keim et al., 2001Keim et al., , 2006Berra and Jadoul, 2002;Hornung and Brandner, 2005;Hornung, 2007;Hornung et al., 2007aHornung et al., , 2007cBreda et al., 2009;Roghi et al., 2010;Stefani et al., 2010;Sýkora et al., 2011;Haas et al., 2012;Bialik et al., 2013;Soua, 2014;Dal Corso et al., 2015, 2018bGattolin et al., 2015;Mueller et al., 2016;Sun et al., 2016). The carbonate sedimentation crisis and siliciclastic input can also be observed in hemipelagic and pelagic settings (Hornung et al., 2007b;Rigo et al., 2007;Rostási et al., 2011;Preto et al., 2013;Nakada et al., 2014). ...
... 7-Locations in the Alpine area: Northern Calcareous Alps (NCA), Austria (Schlager and Schöllnberger, 1974;Hornung and Brandner, 2005;Hornung, 2007;Hornung et al., 2007aHornung et al., , 2007cRoghi et al., 2010;Dal Corso et al., 2015;Mueller et al., 2016), Southern Alps and Northern Karawanken, Slovenia (Celarc and Kolar-Jurkovšek, 2008;Roghi et al., 2010;Sýkora et al., 2011), Transdanubian Range, Hungary (Rostási et al., 2011;Haas et al., 2012;Dal Corso et al., 2015, 2018bBaranyi et al., 2019b); Southern Alps, Northern Italy (Julian Alps: De Zanche et al., 2000;Gianolla et al., 2003;Roghi, 2004;Dal Corso et al., 2018b. Dolomites: De Zanche et al., 1993Gianolla et al., 1998;Preto and Hinnov, 2003;Breda et al., 2009;Stefani et al., 2010;Dal Corso et al., 2012Gattolin et al., 2015. Lombardy: Berra and Jadoul, 2002); Lagonegro Basin, Southern Italy (Furin et al., 2006;Rigo et al., 2007;Preto et al., 2013). ...
... More recently, it was highlighted that changes in carbonate production mode seem to have occurred across the CPE. In the carbonate platforms of the Dolomites, Western Tethys (Northern Italy in Fig. 1A), prolific microbial carbonate production came to an end at the onset of the CPE, and was replaced by skeletal carbonate production (Dal Corso et al., 2015;Gattolin et al., 2015). This evidence seems to contradict the more established belief that microbialites represent crisis facies testifying to the opportunistic proliferation of bacteria after crises of reef building organisms (Schubert and Bottjer, 1992;Martini et al., 2004;Hornung and Brandner, 2005;Lukeneder et al., 2012;Haas et al., 2014;Peybernes et al., 2015). ...
... A relationship between the climate episode supposed by Simms & Ruff ell (1989) and the common occurrence of amber in the Dolomites and globally was suggested by Gianolla et al. (1998a). Researchers in Padova and Ferrara then studied the stratigraphic signature of the Gianolla et al. (1998a) and Preto & Hinnov (2003); distribution of scleractinian reefs from Gattolin et al. (2015). Tropitid ammonoids and the conodont Carnepigondolella are taken here as representative for Tuvalian taxa that radiated during the CPE among ammonoids and conodonts. ...
... The crisis of high-relief carbonate platforms during the Carnian is one of the most evident effects of the CPE, and was associated with a sea level drop and consequent sudden increase of siliciclastics, noted in earlier works (e.g., Bosellini, 1984;De Zanche et al., 1993;Gianolla et al., 1998b;Neri & Stefani, 1998). Only later, did the role of climate change on the evolution of carbonate platforms became obvious (Keim et al., 2001;Bosellini et al., 2003;Hornung et al., 2007b;Neri et al., 2007;Stefani et al., 2010) and when the effects and timing of the forcing were more clearly described by Gattolin et al. (2015). ...
... Along this km-scale platform-basin transect, the relationships between high-relief carbonate platforms and basins, the basin infilling and levelling of the palaeotopography and then the establishment of a thick Upper Triassic continental to shallow water succession are exposed continuously. The stratigraphic succession of Rifugio Dibona (Fig. 3), on the eastern end of the transect, has been the most studied in relation to the CPE (e.g., Preto & Hinnov, 2003;Breda et al., 2009;Dal Corso et al., 2012;Gattolin et al., 2015;Maron et al., 2017), but is only one of many studied sections in the Dolomites that encompass the CPE; a correlation scheme with other locations of the Dolomites is available, e.g., in the explanatory notes of the national geological map of the area (Neri et al., 2007). Among these sections, the one near Heiligkreuz is notable because it was correlated early on with the "Lunz" Event of Austria (Koken, 1913;Fig. ...
The Carnian Pluvial Episode (CPE) was a perturbation of the Late Triassic climate that had a strong impact on marine and terrestrial ecosystems. The CPE is still a relatively neglected episode if compared to the other global ecosystem turnovers of the Mesozoic. Nevertheless, the CPE is synchronous with a major biological turnover, with both extinction among many marine and terrestrial groups and, remarkably, one of the most important evolutionary phases in the entire history of Life. The first significant radiation of dinosaurs, the spread of conifers and bennettitaleans, the first common occurrence of calcareous nannofossils, and the first reefs built by scleractinian corals all occurred during or soon after the CPE. Furthermore, the first common occurrence of amber dates to the CPE. Ammonoids and conodonts, the two most important groups for the biostratigraphy of the Triassic, were also subject to a significant turnover. Many localities in Italy had a primary role for the understanding of the CPE, and still represent benchmarks for new studies. Some of these localities are paradigmatic examples of the geological and biotic processes that were occurring during this interval of geologic time, and should be designated as geosites. While recent studies on the CPE focused on identifying the episode globally, and far from the best studied regions of Western Tethys and the European continent, the Italian CPE localities could still provide a wealth of information on this event, especially concerning the evolution of shallow marine and terrestrial groups. Indeed, the best deep-water record of the CPE (Pignola, Basilicata), the most expanded and complete shallow water successions (Raibl area, Friuli-Venezia Giulia), the most prolific amber sites and the best preserved reef associations (Dolomites, Veneto) all occur in Italy. RIASSUNTO-[L'Evento Pluviale Carnico in Italia: storia delle ricerche e prospettive]-L'Evento Pluviale Carnico (CPE) è stato un evento climatico e di crisi biologica che ebbe luogo a metà dell'età Carnica (tardo Triassico) e che ebbe un impatto notevole sugli ecosistemi marini e terrestri. Rispetto ad altri eventi di crisi biologica del Mesozoico, il CPE è stato finora trascurato. Eppure, si può provare come allo stesso tempo si sia verificata l'estinzione di numerosi taxa in gruppi marini e terrestri, ma soprattutto la radiazione di molteplici gruppi tassonomici, al punto che il CPE dovrebbe essere considerato uno dei passaggi evolutivi più importanti della storia della vita. Tra i gruppi che hanno avuto una importante radiazione durante o immediatamente dopo il CPE, vanno annoverati i dinosauri, le conifere e le bennettitali, i nannofossili calcarei. Anche i primi reef con un contributo significativo dei coralli Scleractinia e la prima apparizione diffusa e abbondante di ambra vanno datate al CPE. Infine, i due principali gruppi di fossili di mare aperto, che sono anche i principali strumenti biostratigrafici per il Triassico, sono stati soggetti ad un forte turnover durante il CPE. Le località italiane che contengono una documentazione del CPE sono numerose, hanno rappresentato e rappresentano tuttora degli affioramenti irrinunciabili per la comprensione e lo studio degli effetti del CPE sulla sedimentazione e sulla vita sulla Terra. Proprio per il loro ruolo nella storia della comprensione di questo evento, e per la loro importanza nel documentare il CPE, si propone che i principali siti che documentano questo evento siano riconosciuti come geositi. Gli studi più recenti sul CPE si sono concentrati nel riconoscere questo episodio di cambiamento climatico a scala globale, e in particolare lontano dalle regioni più intensamente studiate della Tetide occidentale e dell'Europa continentale. Ci si potrebbe quindi chiedere se esista ancora uno scopo nell'indagare le caratteristiche del CPE in Italia. Si osserva qui che le serie di ambiente marino profondo meglio documentate (ad esempio nel Bacino di Lagonegro della Basilicata), le successioni di mare basso più continue ed espanse (Cave del Predil in Friuli-Venezia Giulia), i giacimenti più prolifici di ambra triassica ed i reef meglio preservati (Bacino di Cortina nelle Dolomiti) sono tutti localizzati in Italia. Queste località possono ancora fornire una notevole quantità di informazioni inedite, soprattutto per quanto riguarda l'evoluzione degli organismi di mare basso e terrestri.
... However, the opposite was observed for the CPE in the Southern Alps where platforms consisting primarily of microbial carbonates were temporarily replaced by ramps with ooids and skeletal grains (Dal Corso et al., 2015;Gattolin et al., 2015). ...
... The study of the sedimentary succession of the Southern Alps offers the interesting opportunity to compare the evolution of two carbonate systems that occupied a rather similar paleogeographic position across times of major perturbations of the global carbon cycle and may help understanding this conundrum. Evidence of changes in the carbonate factory across the CPE has been provided (Gattolin et al., 2015), while the carbonate factory evolution across the S-P Event has not been investigated until now. ...
... Moreover, both for the S-P Event (this study) and the CPE (Dal Corso et al., 2015;Gattolin et al., 2015), the isotope shifts correspond to a drop in the microbial component produced on shallow water carbonate systems (Fig. 8). Such a response is peculiar because it is opposite to that documented for other perturbations of the carbon cycle, where microbialite development was favored by crises of other carbonate producers like scleractinian corals (e.g., Webb, 1996;Schubert and Bottjer 1992;Whalen et al., 2002). ...
Early Jurassic shallow water carbonate environments of Tethys experienced important changes in a context of rifting that climaxed with the final break-up of Pangea. This time was also characterized by major perturbations of the global carbon cycle, some of which likely linked to the emplacement of large igneous provinces. At the Sinemurian–Pliensbachian (Early Jurassic) transition a globally recognized carbon isotope perturbation named “S–P Event” was found. In the western Tethys, this coincided with important architectural changes in the carbonate platforms which switched from peritidal flats to subtidal rimmed lagoons. A similar evolution in carbonate systems was observed during the Carnian Pluvial Episode (Late Triassic) when a global carbon isotope perturbation coincided with the demise of microbial carbonate platforms in the Tethys. In this paper, new carbonate and organic carbon isotope records and quantitative petrography data (modal analysis) from the deep- and shallow-water Sinemurian–Pliensbachian sedimentary successions exposed in the central Southern Alps of Italy are presented. Data show that across two negative carbon isotope excursions the carbonate factory abruptly changed and a drop in the microbial fraction of the carbonate occurred. This suggests that environmental modifications associated with these isotope excursions impacted the type of carbonate production and were a key-factor in determining the evolution of Tethyan carbonate platforms. New results and a comparison between the S–P Event and the Carnian Pluvial Episode highlight striking commonalities and imply that the demise of microbial carbonate systems coincident to isotope perturbations is not an isolated event in geologic history. Microbialites, therefore, do not necessarily represent “crisis facies” following extinction events. Rather, their development or demise appears linked to yet poorly understood mechanisms governing the interaction between global climate changes and shallow-water carbonate sedimentation.
... The onset of the CPE was coincident with a major negative δ 13 C perturbation (CIE), which has been reported in a few bulk organic carbon and n-alkane records (Dal Corso et al. 2012Mueller et al. 2015Mueller et al. , 2016Sun et al. 2016;Miller et al. 2017; Baranyi et al. 2018). The CIE coincides with humid climate (Roghi 2004;Roghi et al. 2010;Mueller et al. 2016), global warming (Trotter et al. 2015;Sun et al. 2016), carbonate compensation depth rise (Rigo et al. 2007), demise of microbial carbonate platforms and input of siliciclastics (e.g., Hornung et al. 2007a;Breda et al. 2009;Kozur & Bachmann 2010;Preto et al. 2013;Dal Corso et al. 2015;Gattolin et al. 2015;Sun et al. 2016). The emplacement of Wrangellia large igneous province was suggested as the trigger of the CPE (e.g., Furin et al. 2006;Dal Corso et al. 2012Sun et al. 2016Sun et al. , 2018. ...
... In the marine sedimentary basins of the Western Tethys realm, the CPE is always accompanied with a demise of microbial carbonate platforms and sudden arrival of siliciclastics (e.g., Simms & Ruffell 1989;Hornung et al. 2007a, b;Rigo et al. 2007;Preto et al. 2010;Dal Corso et al. 2015;Gattolin et al. 2015;Mueller et al. 2015Mueller et al. , 2016. This relationship between the CPE, the type of carbonate factories and siliciclastic input is particularly clear in the Dolomites, where high-relief, strongly productive microbial carbonate platforms entered a crisis and were substituted by carbonate or mixed depositional systems with mostly ooids and skeletal grains (Dal Corso et al. 2015;Gattolin et al. 2015). ...
... In the marine sedimentary basins of the Western Tethys realm, the CPE is always accompanied with a demise of microbial carbonate platforms and sudden arrival of siliciclastics (e.g., Simms & Ruffell 1989;Hornung et al. 2007a, b;Rigo et al. 2007;Preto et al. 2010;Dal Corso et al. 2015;Gattolin et al. 2015;Mueller et al. 2015Mueller et al. , 2016. This relationship between the CPE, the type of carbonate factories and siliciclastic input is particularly clear in the Dolomites, where high-relief, strongly productive microbial carbonate platforms entered a crisis and were substituted by carbonate or mixed depositional systems with mostly ooids and skeletal grains (Dal Corso et al. 2015;Gattolin et al. 2015). ...
New biostratigraphic (ammonoids and conodonts) and geochemical data (carbonate carbon and oxygen stable isotopes, and organic carbon stable isotopes) are presented for the Carnian (Upper Triassic) marine succession of Ma’antang, Jiangyou County, in the Upper Yangtze Block (NW margin of the Sichuan Basin, China). In this locality, the Ma’antang Formation lies on top of the Tianjingshan Formation, which is identified by the occurrence of peritidal cycles with stromatolite layers, and includes a distinct karst surface in its upper part. Below the karst surface, negative trends in carbonate carbon and oxygen isotopes can be interpreted as the result of meteoric diagenesis. Above, the Ma’antang Formation is subdivided into five units. The lower part (Units 1–3) mostly consists of bioclastic limestones with thin clayey siltstone intercalations, but at least three intervals of terrigenous deposits are present. A lithological change from mainly carbonates to terrigenous clastic rocks occurs between Units 3 and 4. This interval is biostratigraphically well constrained by the occurrence of ammonoids from the clayey siltstone of Unit 4, suggesting a Julian 2 age (Early Carnian), and conodont associations allow us to place the Julian– Tuvalian boundary at 195 m, the upper part of Unit 4. A wide negative carbon isotope oscillation of about 2‰ occurs in Units 1 and 2, which should be dated to the early Carnian and could be correlated to similar perturbations in western Tethys and in the Nanpanjiang Basin, South China. These correlated carbon isotopic oscillations were attributed to the onset of the Carnian Pluvial Episode (CPE). The two known Chinese records of the CPE both display a broad negative carbon isotopic excursion that encompasses a significant part of the Carnian, whereas the western Tethys records feature possibly multiple, short-lived isotopic excursions. The present isotopic data show that the CPE began roughly contemporaneously with the first terrigenous input at Ma’antang. It is unclear whether the minor siliciclastic intervals within Units 1–3 at Ma’antang could be correlated to similar terrigenous episodes in the western Tethys region. So far, Ma’antang is the only locality of the Sichuan Basin where the carbon isotopic perturbation related to the Carnian Pluvial Episode has been documented.
... Benton 1991;Krystyn 1991;Simms et al., 1995;Gianolla et al., 1998;Roghi, 2004;Hornung and Brandner, 2005;Furin et al., 2006;Keim et al., 2006;Hornung et al., 2007;Rigo et al., 2007;Breda et al., 2009;Preto et al., 2010;Balini et al., 2010;Roghi et al., 2010;Stefani et al., 2010;Arche and López-Gómez, 2014;Martinez-Peréz et al., 2014;Lukeneder and Lukeneder, 2015;Franz et al., 2014;Chen et al., 2015;Dal Corso et al., 2015Gattolin et al., 2015;Ruffell et al., 2016;Mueller et al., 2016a,b;Sun et al., 2016;Miller et al., 2017;Dunhill et al., 2017;Kustatscher et al., 2018;Seyfullah et al., 2018;Bernardi et al., 2018). The onset of the CPE coincided with a perturbation of the carbon cycle characterized by a sharp 2-4‰ negative carbon-isotope excursion (NCIE). ...
... Such microbial-dominated composition abruptly changes in the uppermost part of the San Cassiano Formation-lowermost Heiligkreuz Formation, in correspondence with the negative carbon-isotope excursion that marks the onset of the CPE. Ooids and skeletal grains become the most abundant components, and the microbial carbonates reduce to < 10% of rock volume (Gattolin et al., 2015). This change in facies is interpreted as evidence for the crisis of the highly productive early Carnian microbially dominated platforms, which were replaced by less productive metazoan ramps (Gattolin et al., 2015;Dal Corso et al., 2015). ...
... Ooids and skeletal grains become the most abundant components, and the microbial carbonates reduce to < 10% of rock volume (Gattolin et al., 2015). This change in facies is interpreted as evidence for the crisis of the highly productive early Carnian microbially dominated platforms, which were replaced by less productive metazoan ramps (Gattolin et al., 2015;Dal Corso et al., 2015). Above the San Cassiano Formation, the coarse silicislastics, clays, and marls mixed with skeletal and oolitic carbonates of the Heiligkeuz Formation were deposited (Neri et al., 2007;Breda et al., 2009;Stefani et al., 2010). ...
The Carnian Pluvial Episode was a phase of global climatic change and biotic turnover that occurred during the early Late Triassic. In marine sedimentary basins, the arrival of huge amounts of siliciclastic sediments, the establishment of anoxic conditions, and a sudden change of the carbonate factory on platforms marked the Carnian Pluvial Episode. The sedimentary changes are closely associated with abrupt biological turnover among marine and terrestrial groups as, for example, an extinction among ammonoids and conodonts in the ocean, and a turnover of the vertebrate fauna and the flora on land. Multiple negative carbon-isotope excursions were recorded during the Carnian Pluvial Episode in both organic matter and marine carbonates suggesting repeated injection of 13C-depleted CO2 into the ocean–atmosphere system, but their temporal and causal links with the sedimentological and palaeontological changes are poorly understood. We here review the existing carbon-isotope records and present new data on the carbon-isotope composition of organic carbon in selected sections of the western Tethys realm that record the entire Carnian Pluvial Episode. New ammonoid, conodont and sporomorph biostratigraphic data were collected and coupled to an extensive review of the existing biostratigraphy to constrain the age of the sampled sections. The results provide biostratigraphically constrained composite organic carbon-isotope curves for the Carnian. This sheds light on the temporal and causal links between the main carbon-isotope perturbations, and the distinct environmental and biotic changes that mark the Carnian Pluvial Episode. The carbon-isotope records suggest that a series of carbon-cycle perturbations, possibly recording multiple phases of volcanic activity during the emplacement of the Wrangellia Large Igneous Province, disrupted Carnian environments and ecosystems repeatedly over a remarkably long time interval of about 1 million years.
... The onset of the CPE is very well constrained in many stratigraphic sections (e.g., in the Southern Alps of Italy, Northern Calcareous Alps of Austria, Transdanubian Range of Hungary, and in the Nanpanjiang Basin of the South China block) and is placed at the Julian 1 -Julian 2 boundary (i.e., Trachyceras -Austrotrachyceras austriacum ammonoid zones boundary; sensu Gallet et al. 1994). In the marine sedimentary basins of the Tethys realm, the sudden arrival of huge amounts of siliciclastic material, the establishment of anoxic conditions in the restricted basins, and an abrupt change of carbonate factories mark the beginning of the climate change (e.g., Simms and Ruffell 1989;Hornung et al., 2007a,b;Rigo et al., 2007;Preto et al., 2010;Dal Corso et al., 2015;Gattolin et al., 2015;Mueller et al., 2016;Sun et al., 2016;Shi et al., 2017). On the continents and at different latitudes, palaeobotanical evidence shows a shift of floral associations towards elements more adapted to humid conditions (e.g., Roghi et al., 2010;Preto et al., 2010;Mueller et al., 2016b), and increased resin production Roghi et al., 2006;Schmidt et al., 2012). ...
... The CIE is also coincident with the abrupt demise of high-relief microbial carbonate factories. Sequence stratigraphic analysis of sections from the Dolomites shows that a significant sea level fall followed the onset of the CPE (Gattolin et al., 2015) with a delay not yet resolvable in terms of time. This sea-level fall was probably driven by the formation of vast endorheic basins as a consequence of increasing precipitations. ...
... Palynological and sedimentological evidence shows distinct humid pulses interrupted by arid periods (e.g., Roghi et al., 2010;Stefani et al., 2010;Mueller et al., 2016). Moreover, the CPE is not only a time interval of increased humidity, but also a major and complex carbon-cycle perturbation (Dal Corso et al., 2012, 2015Mueller et al., 2016aMueller et al., , 2016bSun et al., 2016;Miller et al., 2017), a time of global warming (e.g., Trotter et al., 2015;Sun et al., 2016), a widespread platform carbonate precipitation crisis and rise of the CCD (Schlager & Scöllnberger, 1974;Hornung et al., 2007a;Rigo et al., 2007;Dal Corso et al., 2012, 2015Gattolin et al., 2015), a time of reduced oxygen availability in many marginal basins of the Tethys (Hornung & Brandner, 2005;Keim et al., 2006;Hornung et al., 2007aHornung et al., , 2007bWang et al., 2008;Rostasi et al., 2011;Soua, 2014;Dal Corso et al., 2015), an interval of increased resin production that yields the oldest significant amber deposits Roghi et al., 2006), a time of extinctions (Simms & Ruffell, 1989;Benton 1991) but also a time of incredible evolutionary innovation (Benton, 1983(Benton, , 1991Preto et al., 2013), and possibly many other still un-described phenomena. Therefore, emphasizing only one aspect of the CPE, i.e. the increase in humidity, could be reductive. ...
In the late early Carnian (Late Triassic) an important, but yet poorly understood, phase of global climate
change occurred. This is roughly coincident with a time of major biological turnover. Many important groups
diversified or spread during the Carnian, e.g., dinosaurs, calcareous nannofossils, and modern conifers. Abrupt
environmental changes are observed in the geological record worldwide during this interval. These phenomena were roughly synchronous with a carbon-cycle perturbation and could be linked to Large Igneous Province volcanism. Palaeoclimatologists, stratigraphers, geochemists, carbonate sedimentologists, palaeontologists, and modellers met at the Hanse-Wissenschaftskolleg, Institute for Advanced Study in Delmenhorst (Germany), to discuss this intriguing episode of climate change, and the associated effects on the environments and biota. The main aims of the workshop was to summarise the current understanding of the Carnian Pluvial Episode, and discuss future research directions.
... One of these halts in carbonate production is related to a major climate change and carbon isotope excursion, the Carnian Pluvial Event (CPE; Simms & Ruffell, 1989;Dal Corso et al., 2015). During the CPE, microbial carbonates were replaced by skeletal grains and ooids, and carbonate platforms could not achieve a substantial depositional relief (Stefani et al., 2010;Gattolin et al., 2015). At the end of this event, a single, continental-scale carbonate platform developed nearly everywhere in Western Tethys during the Late Carnian and Norian/Rhaetian. ...
... The margin to slope facies associations of the Tuvalian Dolomia Principale are similar to those of Palaeozoic and Triassic microbial platforms, and the platform grew steep slopes and a depositional relief of hundreds of metres on the sea floor (for example, Fig. 5). Microbialites occurred in the skeletal factory of late Julian to early Tuvalian ramps of the Dolomites only as minor components (<10%; Dal Gattolin et al., 2015) and were unable to build up significant relief. The Late Carnian emplacement of the Dolomia Principale carbonate platform thus represents the return, in the western Tethys, to high-relief build-ups after a late Julian demise (Schlager & Schollnberger, 1974;Fl€ ugel, 2002;Gianolla et al., 2003;Keim et al., 2006;Stefani et al., 2010;Lukeneder et al., 2012;Gattolin et al., 2015) and may be viewed, in terms of shallow-water carbonate systems, as marking the end of the prolonged environmental perturbation known as the Carnian Pluvial Event. ...
... Microbialites occurred in the skeletal factory of late Julian to early Tuvalian ramps of the Dolomites only as minor components (<10%; Dal Gattolin et al., 2015) and were unable to build up significant relief. The Late Carnian emplacement of the Dolomia Principale carbonate platform thus represents the return, in the western Tethys, to high-relief build-ups after a late Julian demise (Schlager & Schollnberger, 1974;Fl€ ugel, 2002;Gianolla et al., 2003;Keim et al., 2006;Stefani et al., 2010;Lukeneder et al., 2012;Gattolin et al., 2015) and may be viewed, in terms of shallow-water carbonate systems, as marking the end of the prolonged environmental perturbation known as the Carnian Pluvial Event. The margin to slope microbial-dominated carbonate factory of the earlystage Dolomia Principale carbonate platform fits well with other coeval reef communities of Western Tethys (Bernecker, 2005;Martindale et al., 2015) and slightly precedes the Late Carnian-Early Norian biological turnover (Fl€ ugel, 2002;Kiessling, 2009) that caused the microbialites to occur only as accessories in coralsponge-dominated reefs. ...
Wide carbonate platform environments developed on the western passive margin of the Tethys during the Late Triassic, after a major climate change (Carnian Pluvial Episode) that produced a crisis of high-relief microbial carbonate platforms. The peritidal succession of this epicontinental platform (Dolomia Principale/Hauptdolomit, Dachstein Limestone) is widespread in the Mediterranean region. However, the start-up stage is not fully understood. The original platform to basin depositional geometries of the system have been studied in the north-eastern Southern Alps, close to the Italian/Slovenian boundary where they are exceptionally preserved. Sedimentological features have been investigated in detail by measuring several stratigraphic sections cropping out along an ideal depositional profile. The analysis of the facies architecture allowed reconstruction of the paleoenvironments of the Dolomia Principale platform during its start-up and early growth stages in the late Carnian. The carbonate platform was characterized by an outer platform area, connected northward to steep slopes facing a relatively deep basin. Southward, the outer platform was connected to inner sheltered environments by a narrow, often emerged shelf crest. Behind this zone, carbonate sedimentation occurred in shallow lagoons and tidal flats, passing inward to a siliciclastic mudflat. The Dolomia Principale platform was initially aggrading and able to keep pace with a concomitant sea-level rise, and then prograding during the late Carnian. This stratigraphic interval was correlated to the Tuvalian succession of the Dolomites, allowing depiction of the depositional system on a wide scale of hundreds of kilometrew. This large-scale depositional system presents features in common with some Palaeozoic and Mesozoic carbonate buildups (fo example, the Permian Capitan Reef complex, Anisian Latemar platform), both in terms of architecture and prevailing carbonate producers. A microbial-dominated carbonate factory is testified in the outer platform and upper slope. The recovery of high relief microbial carbonate platforms marks the end of the Carnian Pluvial Episode in the Tuvalian of Tethys.
... However, in a recent study of this episode, Wignall (2015) reported that its effects seem to be masked in some places. Although the origins of the CHE are not yet clearly understood (Gattolin et al., 2015), most observations suggests it relates to the Wrangelia large igneous province (Furin et al., 2006;Nakada et al., 2014;Ruffell et al., 2016;Mueller et al., 2016, among others). Synchroneity between this igneous province and the CHE was also noted by Xu et al. (2014). ...
... As a result, limestone ceased formation due to swamping of carbonate-producing organisms, and fluvial and marine sandstone deposits covered vast extensions of the marine platforms. Gattolin et al. (2015) interpret this climate episode as a first step, just before a second one, also before the drop in sea-level that caused microbialites to vanish and gave rise to shallow water carbonates in the Dolomites, Italy. In the Calcareous Alps in Austria, this episode even saw a change from limestone to siliciclastics (Mueller et al., 2016). ...
... The short-lived period of heavy rainfall recorded in many basins that developed during the Julian-Tuvalian of the Carnian age would have increased rock weathering, and so, accelerated the rate of CO 2 removed from the atmosphere resulting in the beginning of a cooling trend (Wignall, 2015). The onset and cessation of this humid episode appears to be broadly synchronous with significant biotic changes Ruffell, 1989, 1990;Benton, 1991;Gattolin et al., 2015). In continental deposits, it was basically reflected by abundant fluvial deposits, while in some marine environments, rivers shed vast amounts of siliciclastic sediments around Pangea causing the demise of carbonate platforms (e.g. ...
This case-study examines correlations in the continental-marine sedimentary record for the Late Triassic Carnian Humid Episode in the western Tethys domain of present-day E Spain and islands of Majorca and Minorca.
... Differently from siliciclastic systems, the geometry and facies architecture of shallow water carbonate platforms are controlled by a complex variety of factors, which include e among others e the chemistry of seawater, the availability of nutrients, temperature, and the type and amount of terrigenous sediment input (e.g., Mutti and Hallock, 2003;Pomar et al., 2004;Schlager, 2005;Pomar and Hallock, 2008). Furthermore, it was shown how changes in facies and geometry of carbonate systems can often be interpreted as a consequence of ecological crises associated to global perturbations of the carbon cycle (e.g., Wissler et al., 2003;Parente et al., 2007;F€ ollmi and Gainon, 2008;Dal Corso et al., 2015;Gattolin et al., 2015). ...
... This is, however, not always the case. Under conditions of reduced accommodation (e.g., Bosellini et al., 1999;Gattolin et al., 2015), or if the ecological crisis is reduced in duration or intensity (e.g., F€ ollmi and Gainon, 2008), carbonate platforms may experience significant facies changes, but then recover and eventually rebound to their initial state (in terms of overall facies architecture and carbonate production potential). ...
... In the Carnian (Upper Triassic) of the Dolomites (Northern Italy), the growth of high-relief microbial carbonate platforms was suddenly interrupted by an episode of climate change, the Carnian Pluvial Event or CPE (Simms and Ruffell, 1989), which was associated with a negative carbon isotope excursion (Dal Corso et al., 2012Mueller et al., 2016a,b). Microbial carbonate production was nearly completely terminated, microbialites were substituted by skeletal grains and ooids in the carbonate platforms of the Dolomites, Northern Italy (Dal Corso et al., 2015;Gattolin et al., 2015), and an ocean-wide crisis of carbonate production is documented (e.g., Hornung et al., 2007;Rigo et al., 2007;Preto et al., 2010). Gattolin et al. (2013) showed that, after a short time interval when mixed siliciclasticcarbonate sediments filled relict basins, the deposition of ooids was widespread over former microbial platforms of the Dolomites, and took place in tidal sedimentary environments. ...
... However, the opposite was observed for the CPE in the Southern Alps where platforms consisting primarily of microbial carbonates were temporarily replaced by ramps with ooids and skeletal grains (Dal Corso et al., 2015;Gattolin et al., 2015). ...
... The study of the sedimentary succession of the Southern Alps offers the interesting opportunity to compare the evolution of two carbonate systems that occupied a rather similar paleogeographic position across times of major perturbations of the global carbon cycle and may help understanding this conundrum. Evidence of changes in the carbonate factory across the CPE has been provided (Gattolin et al., 2015), while the carbonate factory evolution across the S-P Event has not been investigated until now. ...
... Moreover, both for the S-P Event (this study) and the CPE (Dal Corso et al., 2015;Gattolin et al., 2015), the isotope shifts correspond to a drop in the microbial component produced on shallow water carbonate systems (Fig. 8). Such a response is peculiar because it is opposite to that documented for other perturbations of the carbon cycle, where microbialite development was favored by crises of other carbonate producers like scleractinian corals (e.g., Webb, 1996;Schubert and Bottjer 1992;Whalen et al., 2002). ...
In the Early Jurassic, the paleogeography of the western Tethys was that of a series of fault-bounded highs and lows. On one of these highs, the Trento Platform, now exposed in the Southern Alps, the shelf carbonate succession of the Calcari Grigi Group deposited from the Hettangian to the late Pliensbachian. The Trento Platform records a first deepening of the sedimentary environments in correspondence of a δ13C negative perturbation, the so-called “arnioceras event”, occurred in the middle part of the Sinemurian (Masetti et al., 2016). After that, the depositional system in the inner platform switches from a peritidal flat (Monte Zugna and Loppio Oolitic Limestone Formations) to a lagoon (Rotzo Formation). This change occurs around the Sinemurian-Pliensbachian boundary when a major negative δ13C shift recorded globally by marine carbonates and wood, named S-P Event, is documented (Korte and Hesselbo, 2011). In this contribution a new δ13C isotope record from the deep-water sediments deposited in the Lombardian basin, whose age is constrained with nannoplankton biostratigraphy, is presented. Quantitative petrography (modal analysis) has been carried on calciturbidites. A prominent negative carbonate carbon-isotope shift that can be referred to the S-P Event is highlighted. Across the δ13C spike, a decrease of the material exported from the platform and a change in the composition of calciturbidites, from microoncoids-dominated to skeletal grains-dominated, are observed. On the platform, the first part of the S-P Event is elided by a subaerial exposure surface, followed by the deposition of marly limestones that testify for an increase of terrigenous input into the lagoon, and by the onset of meso-eutrophic conditions. We interpret this evolution as the expression of a crisis in the carbonate production of the Trento Platform across the S-P Event, coupled with a climate change towards more humid conditions. The sedimentary evidences recorded in correspondence of the S- P carbon-cycle perturbation on the Trento Platform are also compared to those documented at the Carnian Pluvial Event (early Late Triassic) in the Dolomites, with whom they share close similarities.
... In the marine environment, the climate transformed from dry to humid, leading to an increase in siliciclastic input (Arche and López-Gómez 2014), which may have suppressed carbonate production. Microbes constructed up to 70% of framework carbonate during the Middle Triassic (Gattolin et al. 2015). This microbial carbonate production was suddenly reduced during the CPE, with carbonate ramps replacing the carbonate factory (Hornung et al. 2007;Dal Corso et al. 2012;Lukeneder et al. 2012;Gattolin et al. 2015;Sun et al. 2016Sun et al. , 2020. ...
... Microbes constructed up to 70% of framework carbonate during the Middle Triassic (Gattolin et al. 2015). This microbial carbonate production was suddenly reduced during the CPE, with carbonate ramps replacing the carbonate factory (Hornung et al. 2007;Dal Corso et al. 2012;Lukeneder et al. 2012;Gattolin et al. 2015;Sun et al. 2016Sun et al. , 2020. ...
The Late Triassic Carnian pluvial event (CPE) was an interval marked by global climatic and environmental changes that occurred simultaneously with enhancement of the hydrologic cycle. This event is characterized by multiple negative carbon isotope excursions (NCIEs). However, the driving mechanism behind these multiple NCIEs remains elusive because each of the NCIEs had different magnitudes in different geological settings. In this study, we present a high-resolution record of carbonate carbon isotope (δ ¹³ C carb) and major-trace element data from Well QZ-8 in the Qiangtang Basin, eastern Tethys. The carbon-isotope profile from Well QZ-8 in the Qiangtang Basin, eastern Tethys displays a similar trend to contemporaneous strata in the NW Tethys and South China. This trend is characterized by a distinct negative excursion during the CPE, supporting a global event. Interestingly, our results reveal five NCIEs for the first time in the marine sedimentary succession. Furthermore, each of these NCIEs corresponds well to changes in Ti/Al, Sr/Al, and Sr/Ba, suggesting a regional effect of the hydrologic cycle on carbon isotope excursions. This study emphasizes that each of the NCIEs was influenced by regional hydrological cycles although long carbon-isotope excursion during the CPE was driven by global carbon cycle.
Supplementary material: https://doi.org/10.6084/m9.figshare.c.6805266
... The onset of the Heiligkreuz formation marks the demise of the high-rimmed carbonate platforms, corresponding to a Tethys-scale crisis of the carbonate factories and a significant increase in the siliciclastic input [19,35,36]. According to several authors, this crisis was caused by a global episode of climate change, the "Carnian Pluvial Event" (CPE, [37,38]), which consists of a switch to humid conditions and increased rainfall and runoff at low latitudes, triggered by a major perturbation of the global carbon cycle [39][40][41][42][43][44]. The Heiligkreuz was deposited in a ramp environment that progressively filled the intraplatform basins, onlapping the platform slopes and leveling the paleotopography. ...
... As shown by [67] for the 2D datasets, the 'effective' fracture mapping resolution is at least twice that of the orthoimage resolution, and for the 3D dataset, fractures under 2 m size were considered not important for the 3D analysis of the fracture attitude. 40), and a mode ranging between 10 and 20 m. While the maximum sizes of the 2D and 3D fracture datasets are conditioned by the extension of the Lastoni di Formin outcrop of the orthoimage and the height of the cliffs, respectively, the minimum size of both fracture datasets is due to the resolution and the fracture sampling strategies. ...
In this study, we analyze the fault and fracture network of the Middle Triassic carbonate platform of the Lastoni di Formin (Italian Dolomites, Italy). The reconstruction of the deformation history is of primary importance for a full comprehension of the present structural setting of this carbonate platform. The huge dimensions of the carbonate body and superb exposure of its vertical cliffs and gently dipping top plateau make the Lastoni di Formin platform an ideal outcrop to integrate traditional fieldwork with Digital Outcrop Modelling analysis. The results of the structural studies partially confirm that the present-day fracture pattern is the result of differential compaction-induced deformation that generated WNW-ESE-trending extensional fractures and normal faults, perpendicular to the direction of progradation of the platform. Successively, extensional tectonics, likely related to the Jurassic rifting phase, led to the formation of NNW-SSE striking fractures and westward-dipping normal faults. A Neogene compressional tectonic event, characterized by N-S to NW-SE crustal shortening, deformed the platform, essentially with strike-slip structures.
... is well documented. (see Dürrenstein Fm. in Bosellini, 1984;De Zanche et al., 1993;Gianolla et al., 1998a;Gianolla et al., 1998b;Neri et al., 2007;Gattolin et al., 2015) ( Figure 3). The lower portion of the Heiligkreuz Fm., also known as Borca Mb. (Neri et al., 2007;Breda et al., 2009;Gattolin et al., 2015;Dal Corso et al., 2018) consists of terrigenous-carbonate facies with well-stratified dolomitic limestones, arenaceous dolomites and hybrid arenites with frequent pelitic intervals. ...
... (see Dürrenstein Fm. in Bosellini, 1984;De Zanche et al., 1993;Gianolla et al., 1998a;Gianolla et al., 1998b;Neri et al., 2007;Gattolin et al., 2015) ( Figure 3). The lower portion of the Heiligkreuz Fm., also known as Borca Mb. (Neri et al., 2007;Breda et al., 2009;Gattolin et al., 2015;Dal Corso et al., 2018) consists of terrigenous-carbonate facies with well-stratified dolomitic limestones, arenaceous dolomites and hybrid arenites with frequent pelitic intervals. At the base of the Heiligkreuz Fm. there are biostromes with diversified colonial corals, stromatoporoids and sponges, often well preserved in aragonite both in the Alpe di Specie/Seelandalpe and Dibona areas (Scherer, 1977;Russo et al., 1991;Senowbari-Daryan et al., 2001;Neri et al., 2007;Gianolla et al., 2018). ...
The Carnian Pluvial Episode (CPE) has been recognized as a time of plant radiations and originations, likely related to observed swift changes from xerophytic to more hygrophytic floras. This suggests that the increasing humidity causally resulting from LIP volcanism was the trigger for these changes in the terrestrial realm. Understanding the cause and effects of the CPE on the plant realm, requires study of well-preserved floras that are precisely aligned with the CPE. We therefore focus on the best age-constrained section within the CPE for the terrestrial to marginal marine environment to understand the floristic composition at the early CPE. This is found in the Dolomites, Italy, and is remarkable for the preservation of the oldest fossiliferous amber found in the rock record. An integrated study of palynomorphs and macro-remains related to the conifer families of the fossil resin bearing level brings together the floral components from this section. This observed mixture of different taxa of extinct and modern conifer families underlines firmly the effects of the LIP-induced CPE on the evolution and radiation of conifers.
... The following three hypotheses can be proposed for the origin of the unconformity and the coal-bearing sediments at the base of the continental deposits of the Miankuhi Formation: (1) The slight expressed unconformity represents the oldest effects of the Eo-Cimmerian collision, followed by a subsequent strong deformation affecting the whole Triassic succession related to the progressive propagation of the deformation front across the arc region within the upper plate (Zanchi et al., 2016). This may have caused a vertical uplift of the Kopeh-Dagh basement resulting in erosion and accumulation of continental sediments due to the balance between active tectonic regimes and surface processes; (2) The northward movement of Laurasia and the latitudinal shift towards a more humid belt resulted in a zonal climate control on the sedimentary facies, increasing noticeably the sedimentation and precipitation along the whole southern margin of Laurasia; (3) A local record of the so-called Carnian Pluvial Episode (CPE), a global climatic disturbance with a short duration (Simms and Ruffell, 1989;Ruffell et al., 2016;Miller et al., 2017;Dal Corso et al., 2018, 2020Colombi et al., 2021), influenced the marginal marine to continental setting increasing the runoff, sudden input of immature siliciclastics, stream rejuvenation and fluvial incision, development of paleosols typical of humid climates (Breda et al., 2009;Kozur and Bachmann, 2010), and a marked sea-level fall (Roghi et al., 2010;Stefani et al., 2010;Arche and López-Gómez, 2014;Gattolin et al., 2015;Shi et al., 2017;Barrenechea et al., 2018;Klausen et al., 2020). ...
... In addition, the unconformity at the base of the Miankuhi Formation could represent a time gap of about two million years at most (see the Biostratigraphy section), which is not such a large time gap as reported in other studies (Ruttner, 1991;Seyed-Emami, 2003;Zanchi et al., 2016;Balini et al., 2019;Liaghat et al., 2021). A significant sealevel drop during the CPE is documented worldwide (e.g., Roghi et al., 2010;Stefani et al., 2010;Arche and López-Gómez, 2014;Mueller et al., 2016a;Gattolin et al., 2015;Franz et al., 2014;Zhang et al., 2015;Shi et al., 2017;Barrenechea et al., 2018;Davies and Simmons, 2018;Klausen et al., 2020) and this enhanced erosion could be associated with this global sea-level fall. After the flattening of the basin, a general transgressive trend is documented by the Miankuhi Formation: this marginal marine interval is the only unit of the Aghdarband Group that can be found outside the Aghdarband tectonic window. ...
The Middle–Upper Triassic Aghdarband Basin, NE Iran, consists of a strongly deformed marine and non-marine stratigraphic succession, deposited along the southern margin of Asia in a highly complex tectonic context related to a back-arc setting. The youngest deformed units of the Aghdarband area consist of a rather monotonous sequence of brown-colored shales, with intercalations of siltstones and fine-grained sandstones forming the Miankuhi Formation. The shale-dominated Miankuhi Formation rests on an unconformity surface, separating it from the underlying Sina Formation. A multidisciplinary study based on sedimentological, palynological, and paleobotanical data permits to reconstruct the depositional environments, sedimentary evolution, and paleoclimate conditions of the upper Sina and the lowermost Miankuhi formations. The palynological association of the lowermost part of the Miankuhi Formation yielded sporomorphs of the latest early Carnian to early late Carnian age. Qualitative and quantitative analyses document a shift from xerophytic associations in the upper Ladinian (upper Sina Formation) to hygrophytic assemblages in the Carnian (lower Miankuhi Formation). This increase in hygrophytic elements is also observed in coeval Tethyan outcrops at the same latitudinal belt, suggests a more humid climate in the lower part of the Miankuhi Formation, and correlates this part of the succession with a record of the Carnian Pluvial Episode. The sedimentological and stratigraphical analyses show an evolution from prodelta to delta setting in the upper Sina Formation, then an unconformity enhanced by an interval of fluvial deposits with histosol levels in the basal Miankuhi Formation, in correspondence with the hygrophytic assemblages. The unconformable boundary between the Miankuhi and the Sina formations is, consequently, interpreted as a result of the sea-level fall associated with the humid climate shift, occurring in close association with the first effects of the Eo-Cimmerian Orogeny along the suture zone, taking to a regional reorganization of the basins architecture and the end of volcanic activity in the back-arc region. The main deformations related to the Eo-Cimmerian event thus, correspond in the Aghdarband Basin to the tectonic event that deformed the Miankuhi Formation. This event is probably older than the middle Norian (217.1 ± 1.7 Ma) but younger than the late Carnian, testifying to a diachronicity in the record of collision along the Iranian Cimmerian blocks and Southern Laurasia according to the different considered structural positions.
... The Travenanzes Fm. lies unconformably above the Heiligkreuz Fm. and is overlain by the Dolomia Principale (Hauptdolomit) along a transgressive boundary (Fig. 1b). Large amounts of siliciclastic material were deposited during the Carnian, presumably as a result of a change in climate and increasingly humid episodes, and led to filling of basins that were more than 100 m deep that existed between the carbonate platforms of the Cassian dolomite (Gattolin et al., 2013(Gattolin et al., , 2015. These basin-filling deposits formed a coastal succession or mixed carbonate-siliciclastic ramp, that includes large clinoforms made up of sandstones and conglomerates (Heiligkreuz Fm.; see Preto and Hinnov, 2003;Gattolin et al., 2013Gattolin et al., , 2015. ...
... Large amounts of siliciclastic material were deposited during the Carnian, presumably as a result of a change in climate and increasingly humid episodes, and led to filling of basins that were more than 100 m deep that existed between the carbonate platforms of the Cassian dolomite (Gattolin et al., 2013(Gattolin et al., , 2015. These basin-filling deposits formed a coastal succession or mixed carbonate-siliciclastic ramp, that includes large clinoforms made up of sandstones and conglomerates (Heiligkreuz Fm.; see Preto and Hinnov, 2003;Gattolin et al., 2013Gattolin et al., , 2015. The topography was entirely evened out and overlain by the Travenanzes Fm., a ca. 100 m thick and laterally extensive succession of red and green claystone with intercalated dolomites, evaporites, and siliciclastic beds Brack et al. (1999;modified (Brack et al., 1996;modified) showing the sampling location at Rifugio Dibona. ...
The geochemical conditions conducive to dolomite formation in
shallow evaporitic environments along the Triassic Tethyan margin are still
poorly understood. Large parts of the Triassic dolomites in the Austroalpine
and the southern Alpine realm are affected by late diagenetic or
hydrothermal overprinting, but recent studies from the Carnian Travenanzes
Formation (southern Alps) provide evidence of primary dolomite. Here a
petrographic and geochemical study of dolomites intercalated in a
100 m thick Carnian sequence of distal alluvial plain deposits is presented
to gain better insight into the conditions and processes of dolomite
formation. The dolomites occur as 10 to 50 cm thick homogeneous beds,
millimetre-scale laminated beds, and nodules associated with palaeosols. The
dolomite is nearly stoichiometric with slightly attenuated ordering
reflections. Sedimentary structures indicate that the initial primary
dolomite or precursor phase consisted largely of unlithified mud. Strontium
isotope ratios (87Sr∕86Sr) of homogeneous and laminated dolomites
reflect Triassic seawater composition, suggesting precipitation in
evaporating seawater in a coastal ephemeral lake or sabkha system. However,
the setting differed from modern sabkha or coastal ephemeral lake systems by
being exposed to seasonally wet conditions with significant siliciclastic
input and the inhibition of significant lateral groundwater flow by
impermeable clay deposits. Thus, the ancient Tethyan margin was different
from modern analogues of primary dolomite formation.
... It is expected that the composition and facies architecture of these build-ups varies somewhat according to the specifics of the setting, but they are usually dominated by microbial carbonate (microbialites) and microproblematica, with subordinate amounts of sponges, corals, and soleporacean red algae (e.g., Russo et al. 1997;Flügel 2002;Russo 2005;Tosti et al. 2011;Senowbari-Daryan et al. 2012;Peybernes et al. 2016). In the Dolomites, the growth of extensive microbial platforms ended late in the Early Carnian with the shift towards the warmer, more humid climate known as the "Carnian Pluvial Event" (Dal Corso et al. 2012;Gattolin et al. 2015;Ogg 2015). ...
... As mentioned in the introduction, important changes in carbonate platforms and platform-building organisms took place during the Carnian, the most significant of which is the late Julian-early Tuvalian "Carnian Pluvial Event" (Simms and Ruffel 1989;Dal Corso et al. 2012;Ogg 2015). After the change in climate and the subsequent increase in siliciclastic input (the "Raibl", "Reingraben" or "Lunz event" in Keim et al. 2006), extensive platforms in the Dolomites region stopped growing and were replaced by carbonate-siliciclastic ramps on which only small microbial carbonate mounds grew, before finally disappearing during a drop in sea-level (Gattolin et al. 2015). The onset of the "Carnian Pluvial Event" in the Slovenian Basin is at this moment unrecognized, thus it is not possible to put more precise stratigraphic constraints on the Cerkno olistoliths. ...
The architecture and composition of Middle to lower Upper Triassic platforms is often obscured by dolomitization. Hence, comparatively little is known about their architectures compared to their size and geographic extent. An active quarry near Lesno Brdo (central Slovenia) offers an excellent exposure of Lower Carnian (Julian) massive limestone, which is diagenetically little altered. A detailed microfacies analysis along a 15.5-m log revealed the presence of three facies types: fine-grained limestone as a groundmass, blocks and globular masses of sponge-microbialite boundstone, and lens-like aggregations of polychaete (terebellid) tubes. Sponge-microbialite boundstone contains a rather small number of cosmopolitan sponge taxa, solenoporacean red algae, microproblematica, bryozoans, and a small proportion of dwelling fauna. Instead, stromatolites represent the main constituent. While some blocks appear to have truncated margins, others show mammillary-like protrusions of microbialites into the surrounding sediment, suggesting active growth of microbialite-producing organisms. Aggregations of terebellid worm tubes show a highly irregular relief, with tubes placed sub-parallel to the ancient sea floor. The presence of fibrous rim cement, crystal silt, and in some cases fragmentation of the tubes, suggest at least moderately energetic waters. Aggregations are thus interpreted as preserved in situ, but not in toto. The entire complex was probably deposited at the margin or upper slope of a carbonate platform. Although the presence of a large number of terebellids associated with microbialites boundstone may indicate some sort of environmental stress, such a stress remains to be identified.
... Terrigenous clay and breccia are found on top of these Early Carnian platforms, and filled karst cavities (Gianolla et al., 1998a, b;Preto and Hinnov, 2003;Stefani et al., 2010;Lein et al., 2012). This termination of the platforms was followed during the CPP by a transgression accompanied by an exceptional input of coarse siliciclastics and the deposition of carbonates only in ramp settings (e.g., Hornung et al., 2007a;Preto et al., 2010;Gattolin et al., 2015). In the Transdanubian Range of western Hungary, this influx of clay-rich terrigenous material during the CPP coincided with the demise of carbonate platforms, and there is abundant kaolinite (about 10-20%) in the clay components (e.g., Rostási et al., 2011;Haas et al., 2012). ...
... In our interpretation, the onset of CPP is recorded in the western Sichuan Basin by the karst surface that was coeval with the exposure surface in the Dolomite region of southern Europe, followed by sea-level rise and the first input of siliciclastic sediments at the Lower/ Upper Carnian boundary which played a major role in the permanent drowning of the carbonate platform during the early Tuvalian. We do not discount the other possibility that this uplift and later drowning of this platform in the western Sichuan Basin through this middle part of the Carnian coincided with independent tectonic activity, therefore may not exactly correlate to the carbonate platform crisis in western Tethys of late Early Carnian (e.g., Hornung et al., 2007a;Breda et al., 2009;Gattolin et al., 2015). Indeed, the succession in the western Sichuan Basin may record a simultaneous and complex interaction of both global climate and regional tectonics. ...
Upper Triassic (Carnian) marine successions in the northwestern margin of Upper Yangtze Region (Sichuan Basin, China) show a lithological change from grey oolitic into a sponge-mound limestone (Units 1 and 2 of the lower member of the Ma'antang Formation), then overlain by greyish black to dark grey sandy shale and siltstone (Units 3 and 4 of the upper member of the Ma'antang Formation). Siliceous sponge mounds were built by Hexactinellida, and this succession was examined in three localities: Jushui section in Anxian (JS), and Guanyinya (HWG) and Qingyangou sections (HWQ) in Hanwang, Mianzhu. The conodont Quadralella polygnathiformis confirms a Carnian age for the biolithite and oolitic limestone of the lower Ma'antang Formation. Abundant ammonoids identified as belonging to the Discotropitid and Juvavitid families suggest a Tuvalian 1 (early Late Carnian) age for the lowermost part of the greyish black sandy shale that overlies the sponge mound at the Jushui Section. Field investigations and microfacies analysis suggest that sponge mounds had two stages of growth in relatively deeper water with low energy. The first sponge-growth mound stage ended in a regional karstified omission surface, and was followed by a sudden increase of siliciclastic input. Greyish black shales containing plant fossils cover a second Upper Carnian sponge mound stage, which is mainly recorded in HWG. The onset of these shales may be related to the Carnian Pluvial Phase (CPP) documented in the western Tethys region (e.g., in Italy, Austria and Hungary). The demise of the sponge mounds at all three sections may have been triggered by the joint effect of climatic changes associated with the fresh water input caused by CPP and with a relative sea-level change caused by local tectonic movements in the course of the Indosinian orogeny.
... Any of the acquisition methods tested herein can be used to generate textured models of the scene, and to orthographically project the resulting model over a panel, thus generating an orthomosaic (or orthopanel) of the scene [30,31,[72][73][74]. This procedure finds considerable applications in structural geology, stratigraphy, geoarchaeology and geomorphology, as well as other earth science disciplines, where orthomosaics are generated by orthogonally projecting the model towards a direction that minimizes geometry distortion of the targeted features observable in the model (e.g., geologic structures, bedding planes, clasts, etc. [75][76][77]). In the case of the three SfM models, the orthomosaic construction is a trivial additional step in the SfM-MVS reconstruction workflow, available within photogrammetric reconstruction software tools (e.g., Metashape [73]). ...
We are witnessing a digital revolution in geoscientific field data collection and data sharing, driven by the availability of low-cost sensory platforms capable of generating accurate surface reconstructions as well as the proliferation of apps and repositories which can leverage their data products. Whilst the wider proliferation of 3D close-range remote sensing applications is welcome, improved accessibility is often at the expense of model accuracy. To test the accuracy of consumer-grade close-range 3D model acquisition platforms commonly employed for geo-documentation, we have mapped a 20-m-wide trench using aerial and terrestrial photogrammetry, as well as iOS LiDAR. The latter was used to map the trench using both the 3D Scanner App and PIX4Dcatch applications. Comparative analysis suggests that only in optimal scenarios can geotagged field-based photographs alone result in models with acceptable scaling errors, though even in these cases, the orientation of the transformed model is not sufficiently accurate for most geoscientific applications requiring structural metric data. The apps tested for iOS LiDAR acquisition were able to produce accurately scaled models, though surface deformations caused by simultaneous localization and mapping (SLAM) errors are present. Finally, of the tested apps, PIX4Dcatch is the iOS LiDAR acquisition tool able to produce correctly oriented models.
... The Carnian Pluvial Episode (CPE) was a time of global environmental perturbations with significant biological turnover both in the ocean and on land (e.g., Simms and Ruffell, 1989;Dal Corso et al., 2020). The CPE was initially recognized in many European sedimentary basins as drastic lithologic changes, such as the demise of carbonate platforms and increased siliciclastic input (e.g., Gattolin et al., 2015). Multiple negative shifts of δ 13 C are recognized across the CPE, suggesting a link with volcanic activity of Wrangellia LIPs (e.g., Dal Corso et al., 2018). ...
In the Late Triassic, a global environmental change called the Carnian Pluvial Episode (CPE) emerged, causing major biological turnover. The CPE has been recognized by siliciclastic input to sedimentary basins, multiple carbon isotope perturbations, and climate proxies for humidification. The CPE is considered to have been associated with increased atmospheric pCO2 from eruptions of large igneous provinces. However, the nature of this global environmental perturbation on the continents is still not well understood. Here we present a geochemical analysis of a pelagic deep-sea bedded chert sequence across the CPE in the Jurassic accretionary complex of Mino terrane, central Japan. Fluctuations in terrigenous material supply were reconstructed using Principal Component Analysis of major element compositions. The first principal component positively correlates with elements enriched in clay minerals such as Al2O3, whereas it negatively correlates with CaO, P2O5, and MnO, derived from apatite and manganese. A sudden increase in terrigenous supply was detected around the Julian/Tuvalian boundary, suggesting that CPE-related siliciclastic input also occurred in the abyssal plain environment. The terrigenous supply returned to the pre-CPE state in the Tuvalian. Since the terrigenous material supplied to the abyssal plain is thought to be derived from eolian dust blown from continental arid regions, the increasing terrigenous supply detected in the pelagic deep-sea chert succession may indicate extensive aridification. This result seems to conflict with the common view of the CPE as a humidification event. This contradiction possibly suggests that the extensive aridification occurred within the interior of the supercontinent Pangea, while hydrological circulation enhanced on the coastal region during the CPE.
... The Late Triassic Carnian Stage witnessed major global climatic changes and biotic turnover during the late Early to Late Carnian (Julian 2-Tuvalian), known as the "Carnian Pluvial Episode/Event" (CPE) (Simms and Ruffell, 1989;Roghi et al., 2010;Zhang et al., 2015;Miller et al., 2017;Dal Corso et al., 2018). The CPE is characterized by increased rainfall, humid and warmer climate (Simms and Ruffell, 1989;Hornung et al., 2007;Preto et al., 2010;Ruffell et al., 2016), carbon cycle perturbations (Hornung et al., 2007;Dal Corso et al., 2012Sun et al., 2016;Miller et al., 2017;Li et al., 2021), demise of carbonate platforms and enhanced terrigenous clastic input (Rigo et al., 2007;Hornung et al., 2007;Stefani et al., 2010;Gattolin et al., 2015;Shi et al., 2017Shi et al., , 2019Jin et al., 2018). This episode is also accompanied by high biotic extinction rates (including ammonites, bryozoa, conodonts, and crinoids) as well as diversifications (e.g. ...
The prevailing arid Late Triassic climate was interrupted by a humid Carnian Pluvial Episode (CPE) during the mid-Carnian period. In this study, a palynological study was conducted for the Ma'antang Formation (Carnian) from the northwestern Sichuan Basin, SW China, in the eastern Tethys. The study reveals dominance of terrestrial palynomorphs, and two palynological assemblage zones were identified. Palynofloras are well-presented by dominant ferns (especially Dipteridaceae/Matoniaceae), with less abundant lycopsids, conifers, cycadophytes/ginkgophytes and seed ferns. Overwhelming predominance of wet Lowland SEG and hygrophyte elements, and increased Lowland/Hinterland as well as hygrophyte/xerophyte ratios observed in Units 2–4 of the Ma'antang Formation, suggesting intensified humidity during the Julian 2 in this area. This study presents the first palynological evidence for vegetation changes in South China during the CPE, and correlates well with observations from North China as well as western Tethys, thus further supports worldwide impact of humid climate associated with the CPE.
... The use of UAVs allows shooting remote or inaccessible portions of the outcrops (Sturzenegger and Stead, 2009;Menegoni et al., 2018;Inama et al., 2020), reducing occlusions and vertical orientation biases. In addition, the processing of high-resolution DOMs can produce orthorectified images collected from different points of view (Gattolin et al., 2015;Tavani et al., 2016;Corradetti et al., 2017;Inama et al., 2020). ...
Among the several Triassic carbonate platforms of the Dolomites, the high and vertical cliff of the Gusela del Nuvolau Cassian carbonate platform provides one of the best exposures of a platform - basin transition. However, its analysis using traditional filed surveys can often be limited and distorted due to the difficult and often impossible accessibility of its walls and the lack of optimal observation points. For this reason, in this study an analysis based on the Digital Outcrop Model (DOM) developed by Uncrafted Aerial Vehicle (UAV) digital photogrammetry technique was used. The 3D DOM analysis allowed to properly determine the stratal geometry and the fracture network of the carbonate platform and underlying basinal deposits (San Cassiano Formation) and to identify the presence of early deformation structures. These structures were probably driven by the differential compaction of the basinal facies that is due the differential load of the carbonate platform as confirmed by the numerical 2D models. These structures are generally orthogonal to the NE progradation direction of the carbonate platform, as in the nearby Lastoni di Formin platform.
... 6 Myrs, in the late Julian-early Tuvalian of the Carnian [12][13][14] (Fig. 1), and was marked by repeated carbon-cycle perturbations, as evidenced by multiple negative carbon-isotope excursions (NCIEs) [6][7][8]13,[15][16][17][18][19][20][21][22] . The NCIEs indicate large injections of 13 C-depleted carbon into the exogenic C-cycle reservoirs, each of which just precedes increases of continental runoff, as chiefly observed in the successions of the Western Tethys, and changes in carbonate sedimentation 7,8,21,23,24 . Understanding the triggers of the CPE is crucial given its important juncture in Earth history and the parallels with the cascade of events associated with other mass extinctions. ...
The Late Triassic Carnian Pluvial Episode (CPE) was a time of biological turnover and environmental perturbations. Within the CPE interval, C-isotope and sedimentary records indicate multiple pulses of depleted carbon into the atmosphere–ocean system linked to discrete enhancements of the hydrological cycle. Data suggest a similar cascade of events to other extinctions, including being potentially driven by emplacement of a large igneous province (LIP). The age of the Wrangellia LIP overlaps that of the CPE, but a direct link between volcanism and the pulsed CPE remains elusive. We present sedimentary Hg concentrations from Western Tethys successions to investigate volcanic activity through the previously established CPE global negative C-isotope excursions (NCIEs). Higher Hg concentrations and Hg/TOC are recorded just before and during NCIEs and siliciclastic inputs. The depositional settings suggest volcanic Hg inputs into the basins over the NCIEs rather than increases of Hg drawdown or riverine transport. Differences in Hg and Hg/TOC signals between the basins might be linked to coeval LIP style or the temporal resolution of the sedimentary successions. Overall, our new data provide support for a link between pulses of Wrangellia LIP volcanism, NCIEs, and humid phases that mark the CPE in the Western Tethys.
... The palaeogeography was consequently characterized by large emerged areas to the south-southwest (Adige Valley; Vicentinian Prealps; Western Dolomites), bounded by attached and isolated carbonate platforms (Cassian Dolomite) in the northeastern Southern Alps. The regressive trend culminated in the late early Carnian (Car 2 depositional sequence), with a strong northeastward shift of the coastline and complete flattening of the palaeotopography matched with a climatically-driven increase in siliciclastic sediment supply into the basins and concomitant demise of the microbial carbonate platforms (Breda et al., 2009;Gattolin et al., 2015). This climatic perturbation, known as Carnian Pluvial Episode (CPE), is a phase of climate change (from arid to markedly humid conditions) recorded worldwide in the Carnian stratigraphic successions that had a strong impact on marine and terrestrial ecosystems (Bosellini et al., 2003;Preto et al., 2010Preto et al., , 2019Dal Corso et al., 2012, 2018Bernardi et al., 2018). ...
We provide here the most complete census of the Italian Triassic tetrapod ichnosites ever published based on an extensive literature review, integrated with previously unpublished data. Most ichnosites are located in the Southern Alps but track-bearing localities are also described in the Western Alps, in Northern Apennines, Maritime Alps and in Sardinia. The chronostratigraphic distribution of the tetrapod footprints can be framed in two macro-sets of ichnoassociations. A first set ranges from the upper Lower Triassic (Olenekian) to the Middle Triassic (upper Anisian, Illyrian) where ichnoassociations are dominated by lizard-like footprints (e.g. Rhynchosauroides isp.), with gradual increase through time of footprints referable to archosauriforms (e.g. chirotheriid footprints). After a hiatus extending up to the basal part of the Carnian (basal Julian), a second set of ichnoassociations spreads the whole Upper Triassic. This second set is dominated initially by chirotheriid footprints but, it shows a shift to dinosaur footprints dominance in correspondence with the abrupt global climate perturbation of the Carnian Pluvial Episode.
... In recent years, digital photogrammetry has emerged as an important source of data in many fields of geosciences (Hodgetts et al., 2004;Burnham and Hodgetts, 2018;Bistacchi et al., 2015;Casini et al., 2016;Cawood et al., 2017;Corradetti et al., 2017a;Menegoni et al., 2019), permitting the reconstruction of georeferenced high-resolution 3D surfaces, and avoiding the use the more expensive, complex and time-consuming LiDAR acquisitions and processing (James and Robson, 2012). The use of drones allows remote or inaccessible portions of the outcrops to be reached (Sturzenegger and Stead, 2009;Menegoni et al., 2018) and, with respect to terrestrial Digital Photogrammetry, overcome limitations of structure exposure, giving the possibility to orthorectify images and observe structures without perspective distortion (Gattolin et al., 2015;Tavani et al., 2016, Corradetti et al., 2017b, and significantly reducing occlusions and vertical orientation biases. ...
The recent rapid improvement of Unmanned Aerial Vehicles, together with advances in photogrammetry and Structure from Motion techniques, have enhanced the role of Digital Outcrop Models in many field of geology, due to the possibility to obtain quantitative information from large and inaccessible areas. In this study we integrated Digital Outcrop Modeling techniques and field survey to investigate the architecture of the Middle Triassic platform of Lastoni di Formin. (Italian Dolomites). The research highlighted the presence of two superimposed carbonate bodies. The lower unit (Cassian I) is dominated by low-angle clinoforms dipping north-northeastward and prograding over the basinal San Cassiano Fm. The upper unit (Cassian II) is characterized by a thick sequence of peritidal cycles connected northward to another generation of clinoforms. The inner platform beds of the upper unit display a lateral thickening that is particularly evident near the shelf break, and that has been interpreted as due to the increased subsidence and the consequent down-to-basin tilting of the outermost part of the platform. Moreover, the structural analysis performed on the Digital Outcrop Models and supported by field observations, highlighted the presence of an early generation of faults and joints that indicate an early gravitational deformation of the platform possibly caused by the platform progradation and compaction-induced subsidence of the San Cassiano basinal deposits. These WNW-ESE synsedimentary structures are formed by normal faults and extensional joints that are oriented nearly perpendicular to the direction of the carbonate platform.
... Due to their particular sensitivity to external forcing on depositional conditions, they are also excellent records of climatic, eustatic and geodynamic change. During the Late Triassic, numerous shallow-water carbonate platforms, both attached and isolated, developed in the Tethyan realm (Bernecker, 2005;Buser et al., 1982;Flügel, 1982;Gale et al., 2015;Gattolin et al., 2015;Jin et al., 2018;Krystyn et al., 2009;Martindale et al., 2014;Schäfer and Senowbari-Daryan, 1982;Tomašových, 2004). In the Panthalassean realm, Upper Triassic shallow-water carbonates are represented by atoll-type and attached systems, spread across the huge ocean ( Fig. 1), and later accreted in the circum-Pacific region (Chablais et al., 2010a(Chablais et al., ,b,c, 2011Basilone, 2020;Martini, 2018, 2020;Khalil et al., 2018;Onoue et al., 2009;Onoue and Stanley, 2008;Peybernes et al., 2015Peybernes et al., , 2016aPeybernes et al., ,b, 2020Peyrotty et al., 2020a,b;Rigaud et al., 2010Rigaud et al., , 2012Rigaud et al., , 2013bRigaud et al., , 2013aRigaud et al., , 2015bRigaud et al., , 2015aSano et al., 2012;Senowbari-Daryan et al., 2010). ...
Owing to their isolated oceanic setting, atoll-type carbonates are well suited for documenting carbonate deposition and diagenesis in oceanic environments away from continental influence. The atoll-type Dalnegorsk limestone (Taukha Terrane, Russian Far East), deposited in the gigantic but poorly-documented Panthalassa Ocean, preserves a complete record of the diagenetic evolution of an Upper Triassic system, out of the Tethyan domain. To study the diagenesis of this carbonate system, we developed a novel analytical workflow, combining cathodoluminescence petrography with high-resolution analyses of environmental proxies in calcitic cements (δ¹⁸O, δ¹³C, REEY, trace and minor/major elements) and in situ U–Pb dating of calcite cements to precisely reconstruct the chronology of the diagenetic events. We combined these lines of evidence to establish a model of atoll evolution, from deposition to dismantling, based on 10 identified diagenetic episodes. The Dalnegorsk limestone records emergence at the Norian-Rhaetian transition, marked by meteoric and evaporitic cements, followed by dismantling of the atoll edges after drawning in the Early Jurassic. Neomorphism of calcitic shells occurred at the onset of calcitic sea conditions during the Toarcian-Bajocian. The limestone was thoroughly cemented during the Middle/Late Jurassic, and accreted within the Taukha Terrane during the Late Jurassic/Early Cretaceous. Accretion resulted in fracturing, brecciation, and recrystallisation of the Dalnegorsk limestone. This model is potentially applicable to any similar atoll system, irrespective of age. The evidence presented here extends our knowledge of Late Triassic environments in the Panthalassa Ocean, and more generally, our understandingg of mid-oceanic limestone formation and evolution.
... Various phenomena are considered to be associated with the Mid-Carnian Episode; and at least some of them were coupled. Pronounced sea-level fluctuations and related oceanographic responses were described from marine basins of the Boreal to Tethyan realms (e.g., Hornung et al., 2007b;Gattolin et al., 2015;Franz et al., 2014Franz et al., , 2019Barrenechea et al., 2018). Shifts of marine habitats and input of terrigenous clastics triggered by these sea-level fluctuations contributed to turnovers of marine organisms on Tethyan shelves and beyond (e.g., Simms and Ruffell, 1989;Preto et al., 2013). ...
The Stuttgart Formation (traditionally called the Schilfsandstein) in the Germanic Basin (or Central European Basin) is a sand-rich episode representing the Mid-Carnian Episode within the gypsum-rich clayey semi-arid Keuper facies. That regional Mid-Carnian Episode is now recognized to be a manifestation of a significant global disruption of Earth's climate-ocean-biological system during the early Late Triassic. In order to provide an accurate time frame and means for high-resolution correlations among continental and marine records, we obtained a composite magnetostratigraphy spanning the entire Carnian from three boreholes in the Germanic Basin. This composite shows a good consistency with earlier published magnetostratigraphy results from South China and enables the construction of a complete Carnian polarity time scale. The upper Carnian (Tuvalian substage) portion implies that: (1) The lower quarter of the Tuvalian is dominated by a reversed-polarity magnetozone; (2) The termination of the Yangtze Platform is coeval with deposition of the Stuttgart Formation in the Germanic Basin; (3) The radiolarian-rich green-colored clay horizon of the Pignola-2 section in south Italy that is below a volcanic ash bed dated as ca. 231 Ma correlates with the D pulse of siliciclastics in Dibona section of north Italy in the middle of the Tuvalian; (4) The upper three-fourths of the Tuvalian is a major normal-polarity-dominated magnetozone; and this interval correlates with the basal E1-E6 portion of the Newark magnetic polarity reference series according to the favored correlation option; (5) The base of the Arnstadt Formation of the Germanic Basin, which had been traditionally assigned as the Carnian/Norian boundary, instead begins within the lower portion of Newark reversed-polarity zone E8r of earliest Norian according to the favored age model, although pending future verification; (6) The polarity patterns of portions of the upper Carnian from the western Tethys sections of Lower Trench at Silická Brezová in Austria and Pizzo Mondello in Italy are verified. This Carnian composite is an enhanced polarity time scale for calibration of other global Carnian successions and events, such as the appearance of the earliest dinosaurs in fossiliferous beds of South America.
... At some depth interval, there are some of dolomitization. Carbonate systems of dolomite generated surface similar to a drowning unconformity, although no transgression occurred (Gattoling et al., 2015). formation in this studied area (Figure 8). ...
A long depositional period of Papua limestone called Kais Formation, which is overlain by clastic sediments of Steenkool Formation, reflects an interesting stratigraphic architecture in the West Papua region. Using seismic stratigraphic method of five stacking patterns, forestepping, downstepping, upstepping, backstepping, and seismic facies (parallel, prograding clinoform, channel fill, mounded) have been observed. Chronostratigraphic reconstruction was completed to figure out the depositional units in space and time. This study reveals the lowstand deposit during Early to Middle Eocene (LST), transgressive-highstand carbonate deposit during Middle Eocene to Middle Oligocene, and transgressive-highstand silisiclastic (TST-HST) deposit during Middle Miocene - Late Pliocene.
... Cradles of life, shallow-water reefal carbonate systems, which represent a key archive for marine life evolution, extensively developed. The Upper Triassic, notably, is marked by the development of numerous widely studied reefal carbonate systems in the Tethyan realm (Bernecker, 2005;Buser et al., 1982;Flügel, 1982;Gale et al., 2015;Gattolin et al., 2015;Jin et al., 2018;Krystin et al., 2009;Martindale et al., 2014;Schäfer and Senowbari-Daryan, 1982;Tomašových, 2004). Their Panthalassan counterparts are in contrast poorly known and mostly preserved as isolated bodies within diverse tectonostratigraphic terranes, which accreted along the Circum-Pacific region (Chablais et al., , 2010bMartindale et al., 2015;Peybernes et al., 2016b;Stanley Jr., 1979;Stanley and Senowbari-Daryan, 1986;Zonneveld et al., 2007). ...
Contrary to their Tethyan counterparts, and despite substantial research, Upper Triassic shallow-water limestone from the Panthalassa Ocean remain poorly known. Their understanding is yet crucial to better constrain past depositional, ecologic, geographic and geodynamic conditions out of the Tethyan domain, and to better assess life evolution and recovery following the greatest Permo-Triassic biological crisis. The Taukha terrane, located in a poorly studied area of the Sikhote-Alin mountain range (Primorsky and Khabarovsk Kraya, Far East Russia) is a key Panthalassan terrane. Near Dalnegorsk City, North-East of Vladivostok, on the northern part of the Taukha terrane, Upper Triassic marine carbonates abound. They show a clear affinity with Panthalassan terranes of both Japan and North America. There, eleven new localities have been extensively sampled, described and inter- preted. Based on field observations and facies analysis, eight major facies, corresponding to specific depositional environments within a carbonate platform, have been established. A conceptual depositional model corre- sponding to a mid-oceanic atoll-type system composed of well-developed lagoon, fringing patch reefs and oolitic shoals is proposed. The foraminiferal assemblages allow refining the age of the carbonate system to the Norian, and locally, exclusively to the lower/middle and the middle parts of the Norian.
... However, this is not always the case. Either under reduced accommodation space [8,9] or reduction in the length or strength of the ecological crises [10], carbonate platforms may go through noteworthy facies change and ultimately return to their preliminary state in terms of entire facies architecture and carbonate production potential [4]. This kind of ooid-dominated facies occur throughout the rock record but appear to be particularly predominant in the Precambrian and Cambrian carbonates [2]. ...
According to the recent chronostratigraphic division of Cambrian, the Cambrian strata in the Kelan section can be subdivided into seven third-order sequences (DS1−DS7) based on cyclicity in sedimentary facies stacking patterns. The calcareous mudstone forming condensed section, micritic limestone comprising deep to middle ramp facies and the oolitic-grain bank facies in Series 3 and Furongian series represent the basic depositional fabric of Cambrian in northwestern part of Shanxi Province, North China Platform. These massive oolitic grainstones demonstrate that the oolitic-grain bank facies constitute the late-highstand systems tract or forced-regressive systems tract. The grains occupy upper parts of the third-order depositional sequences in response to relative sea-level fall. Furthermore, this forming pattern of oolitic-grain bank facies does not follow the standard model of sequence stratigraphy, in which deposition is believed to occur principally during sea-level rise, rather a continuous erosional unconformity develops during sea-level fall. Moreover, the microscopic analysis of oolitic grainstone shows the development of concentric and radial, rounded or elliptical, with or without nuclei, monocrystalline or polycrystalline, Girvanella or micritic ooids. The occurrence of diversified ooids in varying proportions provides a new dimension for studying evolution of the oolitic-grain bank in the North China Platform. The forming pattern of oolitic-grain bank controlled by their sequence-stratigraphic position in the Kelan section in the Shanxi province provides an important clue and a research direction for the regional correlation, as well as the paleogeographical reconstruction of the Cambrian Series 3 and Furongian series.
... These macroscopic facies-changes, resemble those characteristic of the CHE worldwide: increased terrigenous input and abrupt demise of shallow-water carbonate production (Simms and Ruffell, 1989;Hornung and Brandner, 2005;Keim et al., 2006;Hornung et al., 2007aHornung et al., , 2007bRigo et al., 2007;Kozur and Bachmann, 2010;Lukeneder et al., 2011;Sýkora et al., 2011;Gattolin et al., 2015). However, new conodonts from the HWQ section imply a late Tuvalian age for the demise of sponge mounds and the deposition of terrigenous sediments, i.e., well after the CHE. ...
During the Carnian, the Hanwang area in the northwestern Sichuan Basin (South China) was characterized by shallow water carbonate sedimentation that underwent an abrupt demise associated to a sudden input of terrigenous sediments. This major facies change was considered to be the expression of the onset of the Carnian Humid Episode, a most remarkable environmental crisis in Late Triassic that is well recognized in northwestern Tethys margins and coincides with a major global perturbation of the carbon stable isotope record. However, the lack of detailed biostratigraphic constraints have so far prevented a precise dating of the carbonate platform demise in western Sichuan Basin. In this work, the Qingyan Gou (HWQ) section, cropping out in Hanwang, was investigated for its facies and microfacies, carbonate carbon and oxygen isotopes on brachiopods, microbial grains and bulk matrix. Facies analysis shows a marine transgression from inner ramp oolitic shoal to middle ramp siliceous sponge mound, then overlain by shale and calcareous siltstone with interbedded silty mudstones. Refined biostratigraphic data from HWQ and Guanyin Ya (HWG) sections imply that the demise of sponge mounds occur in the late Tuvalian or later. A negative carbon isotope perturbation was found in the bulk matrix immediately below the sponge mounds demise, but it was not found on the isotope record from brachiopods. This suggests that the negative shift in the bulk carbonate was probably related to diagenesis. Given the late Tuvalian (last substage of Carnian) age attributed to the demise of the sponge mounds and the absence of a carbon isotopic excursion, we infer that the carbonate platform crisis and strong terrigenous input in Hanwang cannot be related to the onset of the Carnian Humid Episode. These the demise of the carbonate platform and the facies deepening trend could be rather due to the interplay between accelerating subsidence rates, environmental chants and enhanced siliciclastic input related to the formation of a foreland basin during Indosinian orogenesis.
... These three subunits broadly represent three genetic stratigraphic sequences, and the whole sedimentary record constitutes three regressivetransgressive (R-T) sequences in the Manuel Fm. Influence of sealevel oscillations was also reported from mid-Carnian equivalent units in the Alps and Central European basin (Franz et al. 2014;Gattolin et al. 2015). ...
This study examines rainfall variations of the Mid-Carnian Pluvial Episode (CPE) based on the continental fluvial sedimentology, palaeosol and clay mineralogy records of the Stable Meseta (eastern Spain). In the formation examined, the Manuel Fm or K2 Fm, the CPE is represented by three regressive–transgressive sequences, or subunits K2.1, K2.2 and K2.3, from base to top. Each subunit broadly consists of a genetic stratigraphic sequence bearing well-developed highstand, lowstand and transgressive systems tracts. Hydromorphic features in the palaeosols suggest changes in the activity of both groundwater and surface water. The clay mineral assemblage is dominated by illite, with a minor presence of kaolinite and traces of smectite in some samples. After ruling out tectonism in the study area, climate and eustatism emerge as the main allogenic controls in the sedimentary record. Differentiated sedimentary facies and architectural elements in the K2.2 subunit were probably controlled by both a more humid climate and source area, whereas K2.1 and K2.3 were more related to base-level changes and eustatic control. The presence of more waterlogged pedotypes and of kaolinite and traces of smectite in the clay mineral assemblage of K2.2 also indicates increased humidity. Notwithstanding, our data do not point to intense rainfall periods for the CPE in eastern Spain.
... Where these are negligible, single crystals with coherent lattice are common (Fig. 15D). The Carnian platform-derived boulders were deposited in a basin where interplay between climate and sealevel change resulted in periodic input of continentally-derived siliciclastics (Gattolin et al., 2015). It is reasonable to infer that HS entered the basin adsorbed onto siliciclastic colloids and preserve the initial products of crystallization. ...
... There is no one sequence model that is applicable to the entire range of case studies, and the sequence stratigraphic models were summarized based on the particular circumstances in different geological times of the study area (Catuneanu, 2006). The Exxon's classic sequence stratigraphic model is used to explain the carbonate sedimentary sequence evolution (Gattolin et al., 2015;Handford & Loucks, 1993), and we could use this model to explain sedimentary sequence evolution in the Early Carboniferous which are mainly composed of carbonate sediments. In many cases, the sequence model proposed by Haq, Hardenbol, and Vail (1988) are present, and the variety of clasts derived from metamorphic rocks and magmatic rocks ( Figure 2a). ...
The Wuwei Basin is one of the major coal- and hydrocarbon-bearing basins in northwestern China. Depositional environments, sequence stratigraphy, and palaeogeography of the Carboniferous to Early Permian coal measures in the Wuwei Basin were studied based on the data from outcrop sections and boreholes cores. The coal accumulation model is established within the sequence-stratigraphic context. Fourteen lithofacies were recognized with the lithologies ranging from conglomerates, sandstones, siltstones, mudstones, carbonates, to coals, which are arranged into five facies associations representing delta, tidal flats, barrier and lagoon, littoral and associated strand-plain, estuary, and carbonate ramp environments. These facies associations collectively revealed an overall marine-continental transitional basin setting. The key sequence bounding surfaces, such as the regional unconformity, the basal surface of incised valley fills, and the surface that mark the facies reversal from regression to transgression, have been identified. Based on these surfaces, the Carboniferous to Early Permian in the Wuwei Basin were subdivided into seven third-order sequences. The distribution of lithofacies and depositional facies in borehole sections, outcrop sections, and three correlation cross sections was investigated, and the sequence-based palaeogeographic maps were reconstructed. It is inferred from the coal thickness and palaeogeographic maps that the most favourable coal accumulation environments were tidal flat and barrier–lagoon, followed by delta. The sequence stratigraphic framework controls the vertical horizons of the coal seams, whereas the palaeogeographic units determine the lateral development of the coal seams. Tidal flat, barrier–lagoon, and delta in the late transgressive systems tract and early highstand systems tract are the most favourable coal accumulation palaeogeographic units. The main coal accumulation centres were mainly distributed in the Yingpan Sag in the south of the basin, followed by the Ermahu Sag in the north of the basin.
... Age: Metapolygnathus praecommunisti has been collected in the Santa Croce/ Heiligkreuz Formation (Dolomites- Maron et al. 2017), along with the ammonoid Shastites cf. pilari that is typical of the Tropites dilleri Zone (Gianolla et al. 1998;De Zanche et al. 2000;Breda et al. 2009;Gattolin et al. 2015;Maron et al. 2017). Thus, the base of the Me. ...
Conodonts are biostratigraphically very important microfossils in the Upper Triassic, occurring in different marine habitats, from deep-ocean to shallow-shelf waters. Because of their great abundance, worldwide distribution, strong resistance to rock metamorphism, and mineralogical composition that makes them reliable tools for biostratigraphic and geochemical studies, conodonts have proven to be important tools in defining the Geological Time Scale (GTS) and Global Stratotype Section and Points (GSSPs). We present here an original Upper Triassic conodont biozonation for the Tethyan Realm integrated, where possible, with ammonoid and radiolarian zones, providing also numerical ages for stages and substages. Based on the most recent conodont biostratigraphic and systematic studies, we propose a subdivision of the Upper Triassic interval into 22 conodont zones (nine for the Carnian, ten for the Norian, and three for the Rhaetian), correlated, where possible, with the most recent North American conodont zonations. Discussions on the most biostratigraphically important conodont taxa are also provided, in particular for the stratigraphic intervals around the base of the Norian and Rhaetian stages, the GSSPs of which have yet to be defined. In this view, we provide data supporting the validity of conodonts as reliable tools for global correlations, recommending two conodont biovents as possible primary biomarkers: the FAD (First Appearance Datum) of Metapolygnathus parvus for the base of the Norian and the FAD of Misikella posthernsteini for the base of the Rhaetian. The conodont species Norigondolella carlae n. sp. from the upper Tuvalian (Carnian) is also defined.
... The most distinctive climate change during the Triassic occurred in the late early Carnian when high temperatures (Hornung et al., 2007a;McKie, 2014;Trotter et al., 2015;Sun et al., 2016), along with increased humidity, favoured intensive weathering and erosion, development of large fluvial systems, and increased siliciclastic input into marine basins (Simms and Ruffell, 1989). The enhanced terrigenous runoff, freshwater influx and increased nutrient supply caused reduced carbonate productivity, reef crisis, and biotic turnover resulting in decline or demise of shallow marine carbonate systems across the Western Tethys (Simms et al., 1995;Hornung and Brandner, 2005;Hornung et al., 2007a;Gattolin et al., 2015). Karstification and lateritic palaeosols developed locally on subaerially exposed Western Tethyan carbonate platforms (Mutti and Weissert, 1995;Breda et al., 2009;Escudero-Mozo et al., 2014). ...
Quartz-rich sandstones and ironstone crusts occur in the lowermost part of the Upper Triassic Moesian Group exposed in the western Balkanides. On the basis of performed field studies, micropetrography, X-ray diffraction, and major-element chemistry, these deposits are defined as first-cycle quartz arenites and laterites, respectively. The former were deposited in an alluvial environment, while the latter developed in gravel-dominated fluvial sediments. The main control on their formation was warm to hot humid climate conditions combined with low relief, quiescent tectonic setting, mixed source area, and slow sedimentation rate. The decreasing compositional maturity of the sandstones forming the Glavatsi Member (quartz arenites→feldsarenites→litharenites), the disappearance of the lateritic crusts upwards in the continental succession, and the presence of thick overlying fluvial and playa deposits in the Komshtitsa Formation (or Chelyustnitsa Formation) reflect gradual transition from humid to subhumid climate, and then to persistent semi-arid climate regime. This irreversible trend correlates with other Upper Triassic strata deposited in the Western Tethys realm and adjacent areas. The coeval formation of quartz arenites and laterites must have been related to the most distinctive climate change during the Triassic, i.e., the global Carnian Humid Episode. The new results and interpretations appear to be the first geological record for the effect of pronounced mid-Carnian humidity reported from Eastern Europe. They also present indirect sedimentological evidence for the stratigraphical range of the Moesian Group in NW Bulgaria.
... The second negative d 13 C shift onset in the uppermost Sinemurian, is named Sinemurian-Pliensbachian boundary Event and is considered of global scale (Korte and Hesselbo, 2011). Across the SeP Event the Trento Platform shows relevant facies changes that share analogies with the evolution of other shallow water carbonate systems in the geologic record in correspondence of major negative C-isotope perturbations (Weissert et al., 1998;Morettini et al., 2002;Wissler et al., 2003;Marino and Santantonio, 2010;Dal Corso et al., 2015;Gattolin et al., 2015). The platform switches from an open marine subtidal (Monte Zugna and Loppio Oolitic Limestone Formations) to a lagoonal carbonate environment (Rotzo Formation), meso-eutrophic conditions onset and a sharp increase in the terrigenous fraction is observed in the Rotzo Formation with respect to the underlying units (Fig. 2B). ...
This work focuses on the 3D modeling and structural analysis of the Monte Testo syn-sedimentary structure, developed in the Early Jurassic Calcari Grigi Group of the Trento carbonate platform (Southern Alps, Italy). Significant changes in the facies architecture of the platform sedimentary units, occurred across a global perturbation of the Carbon cycle at the Sinemurian-Pliensbachian boundary, are associated with evidences of syn-sedimentary tectonics. In particular, an early cemented oolitic sedimentary body with a high initial porosity (Loppio Oolitic Limestone) was broken-up and tilted by a pulse of rifting and overlain by tight marls and marly limestones (lower Rotzo Formation) that display sharp changes in thickness across the syn-sedimentary faults. This complex setting creates conditions potentially favorable to hydrocarbon accumulation. In this work, the Monte Testo structure is presented as a conceptual analogue of a hydrocarbon reservoir that may develop thanks to the overlap of the effects of extensional tectonics and climate change-induced modifications in the carbonate platform facies. A 3D geo-model was realized to obtain information about the genesis and tectonic evolution of the structure. Hence, a potential porosity distribution in the 3D model was evaluated showing that such extensional structure, which has a vertical extent of 500 m and covers an area of 15 km², could have been associated to a total pore volume of 2.24 × 10⁷ m³ at the time of its formation. Results suggest that in rifting contexts the combined effect of syn-sedimentary faulting and facies variations related to perturbations in the global carbon cycle could generate potential reservoirs in carbonate platforms.
... The latter was also recorded in adjacent marginal marine, deep marine and continental environments (Rigo et al. 2007;Kozur & Bachmann, 2010;Roghi et al. 2010;Haas, Budai & Raucsik, 2012) and was controlled by a humid climate perturbation known as the 'Carnian Pluvial Episode' or under other names (Ruffell, Simms & Wignall, 2015, and references therein). The middle Carnian decline or demise of marine carbonate systems has been commonly explained by enhanced weathering, development of large fluvial systems and significant siliciclastic input which suffocated the carbonate factory (Hornung & Brandner, 2005;Gattolin et al. 2015) and led to the so-called 'Carnian Crisis' . While some researchers claim that the Carnian Pluvial Episode had only regional character, there is growing evidence for its global nature that affected vast areas of the northern hemisphere spanning from tropical to high latitudes (e.g. ...
The Early to Late Triassic development of a carbonate ramp system in the subtropical belt of the NW Tethys was controlled by the interplay of several global and regional factors: geotectonic setting (slow continuous subsidence on a passive continental margin), antecedent topography (low-gradient relief inherited from preceding depositional regime), climate and oceanography (warm and dry climatic conditions, storm influence), relative sea-level changes (Olenekian to Anisian eustatic rise, middle Anisian to early Carnian sea-level fall), lack of frame-builders (favouring the maintenance of ramp morphology), and carbonate production (abundant formation of lime mud, non-skeletal grains and marine cements, development of diverse biota controlled by biological evolution and environmental conditions). Elevated palaeorelief affected the ramp initialization on a local scale, while autogenic processes largely controlled the formation of peritidal cyclicity during the early stage of ramp retrogradation. Probably fault-driven differential subsidence caused a local distal steepening of the ramp profile in middle–late Anisian time. The generally favourable conditions promoted long-term maintenance of homoclinal ramp morphology and accumulation of carbonate sediments having great maximum thickness (~500 m). Shutdown of the carbonate factory and demise of the ramp system in the early Carnian resulted from relative sea-level fall and subsequent emergence. After a period of subaerial exposure with minor karstification, the deposition of continental quartz arenites suggests the possible effect of the Carnian Pluvial Episode.
... During the Late Triassic, wide carbonate platforms developed on the Tethys margins and constitute an important record of environmental changes. As a consequence, they have been extensively studied, especially in western Tethys (e.g., Schäfer 1979;Dullo 1980;Gaetani et al. 1981;Wurm 1982;Stanton and Flügel 1989;Enos and Samankassou 1998;Iannace and Zamparelli 2002;Gianolla et al. 2003;Stefani et al. 2010;Gattolin et al. 2015). Upper Triassic carbonate platforms also developed in relation with island arcs that are nowadays terranes accreted in the American Cordillera (Stanley and Senowbari-Daryan 1986;Reid and Tempelman-Kluit 1987;Stanley et al. 2008;Martindale et al. 2012). ...
During the Late Triassic, carbonate platforms expanded on continental shelves and island arcs. They have been studied in detail in the Tethys realm but coeval mid-oceanic shallow-water environments of the Panthalassa domain have received less attention. To fill this gap, we investigated the Upper Triassic limestone of the Sambosan Accretionary Complex (SAC), southwest Japan. A comprehensive sampling of the Upper Triassic limestone has been performed in 16 localities at Shikoku Island. Eight microfacies, ranging from pelagic to lagoonal settings, were identified, including two microfacies that are described in the SAC for the first time. Quantitative microfacies analysis assesses the composition of the SAC limestone and its biostratigraphy is refined. Finally, a speculative depositional model of the SAC carbonate platforms is proposed based on modern and ancient analogues. Instead of a true atoll-type platform with well-defined facies belts as suggested by previous studies, this new model suggests that the typical Sambosan platform was more probably a carbonate bank with submerged margins and a mosaic of microfacies in the platform interior. Special attention is given to the factors that have probably controlled the carbonate sedimentation at the top of the seamount(s).
The territory covered by the Sheet 046 – Longarone of the 1:50.000 Geologic Map of Italy basically consists of mountainous land, split into the catchment basins of the Piave River and of its tributary rivers (among which the Cordevole and Maè streams). Geographically, the mapped area mainly belongs to the Southeastern Alps, and particularly to the Dolomites, while only a small portion falls into the Carnian Prealps (e.g., M. Duranno and Col Nudo-M. Cavallo groups). Geologically, the mapped area entirely belongs to the Southern Alps domain. This is marked by lack of alpine metamorphism and is characterized by a fold-and-thrust, polyphase deformative structure, with major overthrusts verging south-eastward and south-westward. The main deformative feature in the sheet is given by a complex set of high-angle, transcurrent and/or reverse fault planes, and overthrusts, named as Valsugana Fault System, separating the Dolomites sector to northwest from the remaining eastern Southern Alps. Due to a crustal-scale pop-up structure, the northern successions are relatively less- deformed, and the Hercynian metamorphic basement crops out in the nearby of the Agordo village: it mainly consists of phyllites, metapelites and metapsammites, with intercalations of acid metavolcanites and also mylonites occurring in the main shear zones (on the whole, composing the Agordo-Cereda Metamorphic Core). The age of the protoliths spans from the Cambrian to the Silurian period. The sedimentary cover is marked at the base by a sharp unconformity on the metamorphic basement. The first deposits are Upper Permian continental sandstones and siltites (Val Gardena Sandstones), that gradually pass upward to marginal marine facies consisting of pelite and evaporite alternations, grading to dark lagoon limestones (Bellerophon Formation). The Lower Triassic is essentially represented by shallow marine to peritidal facies, with prevailing siliciclastic sediments organized in different transgressiveregressive cycles (Werfen Fm.), while the transition to Middle Triassic is dominated by peritidal carbonates (Lower Serla Dolomite) representing the onset of a low-angle, wide carbonate ramp on the whole area. The Anisian cover is marked by an extreme vertical and lateral variability, originated by the superimposing of an articulated paleogeography related to different pulses of sin-sedimentary tectonics, and to the evolution of depositional systems in response to relative sea-level oscillations: at least three transgressive-regressive cycles, with transition from alluvial to marginal marine (Piz da Peres, Voltago, Richthofen conglomerates and Morbiac Formation) and carbonate platform facies (Monte Rite, Upper Serla and Contrin formations), could develop on paleo- topographic highs, while basinal sedimentation persisted on down-lifted areas (Collalto, Dont, Bivera and Ambata formations). Likewise, the overlying Upper Anisian to Lower Carnian succession shows a high lateral and vertical variability, since it is strictly connected with the local nucleation and evolution of high-relief carbonate platform systems: by the latemost Anisian, microbial buildups nucleated and elevated up to 800 meters on the surrounding basins, in cases merging each other and forming relatively large platforms, eventually laterally prograding for few kilometres (Sciliar Formation). At the same time, in basinal areas a thick succession of carbonate, terrigenous and volcanoclastic sediments accumulated (Buchenstein Formation, Zoppè Sandstones, Acquatona and Fernazza formations). Effects of the Late Ladinian tectonovolcanic event affecting the Western Dolomites mainly occurred in the western part of the mapped area, where intra-platform depressions and partial collapses of slopes were formed. A similar paleogeographic framework persisted also in the early Carnian, but with carbonate platforms (Cassian Dolomites) prograding on basins that were progressively filling, with great accumulation of volcanoclastic and mixed terrigenous- carbonate deposits (Wengen and San Cassiano formations). During the early Carnian, an important change in environmental conditions (Carnian Pluvial Episode) led to a temporal reassessment of the carbonate production, disadvantaging reef builders, and to a sudden increase of siliciclastic input in the basin (Heiligkreuz Formation). This resulted in an almost flattened pale-topography in the whole region, that constituted the base for the development of a new, large-scale depositional system set after a regional sea-level fall: alluvial to evaporitic and marginal marine facies associations developed in the Late
Carnian (Travenanzes Fm.), gradually passing upward to peritidal cycles of dolostones, representing sedimentation in the inner part of a large epicontinental carbonate platform (Dolomia Principale). The thickness of the carbonate succession related to the Upper Carnian to Rhaetian interval exceeds in places 1000 metres. In the Dolomites and in the area south to the Valsugana Fault System but west to a NNW-SSE alignment crossing near M. Coro, the Lower Jurassic is mainly characterized by a thick succession of platform limestones (Calcari Grigi Group), subdivided in a lower portion organized in peritidal to subtidal cycles, and an upper portion characterized by oolithic limestones. In the remaining part of the mapped area, the platform evolution is instead marked by a premature fragmentation and drowning, strictly connected with the creation of the Belluno Basin and the opening of the Alpine Tethys: basinal limestones (Soverzene Fm.) were deposited on Upper Triassic platform deposits, often presenting intercalations of calcarenites shed from the nearby (westward) active platform and of breccia layers from instable slopes. Pelagic sedimentation persisted in the basin during the Toarcian-Bajocian time span, originating also black shale levels (Igne Formation). Since the late Middle Jurassic, the whole platform occupying the western part of the
mapped area was progressively covered by high-energy facies related to a pelagic plateau setting (Fanes Piccola Encrinite), while in the Belluno Basin a large calciturbiditic lobe aggraded resedimenting material from shallow environments persisting in the eastern Friuli Platform (Vajont Limestone). The depositional environment was definitively uniformed on the whole area covered by the sheet during the Late Jurassic, when pelagic limestones deposited almost everywhere (Fonzaso Formation and Rosso Ammonitico Veronese). The overlying Cretaceous succession is again characterized by pelagic units (Maiolica), but shedding from the nearby active Friuli Carbonate Platform significantly increased its thickness and the amount of carbonate sediment (Soccher formation) in the eastern part of the mapped area. The younger unit occurring in the sheet (Scaglia Rossa) represents flysch sedimentation in the basin, related to increased terrigenous input from areas uplifted during the early stages of Alpine orogenesis, and decreased input from the almost drowned Friuli Platform. The Quaternary cover in the whole mapped area consists of continental deposits, middle Pleistocene to Holocene in age. A significant part of these deposits has been originated during the Last Glacial Maximum (LGM) and the following withdrawal stage: they are hierarchized in different unconformity-bounded stratigraphic units belonging to the main synthem of the Piave River (PVI). The pre-
LGM deposits form a small percentage of the Quaternary cover and are grouped in the Cadola Super-synthem, while another important part is represented by postglacial deposits (PTG), both related to alluvial and mass-flow processes. Fluvial terraces along the Cordevole and Piave valleys are well developed. Also, some lacustrine deposits are present (Agordo). In the north-western part of the sheet, some deposits have been related to the Little Ice Age (Amola Sub-synthem). The mapped territory is also characterized by a relevant number of landslide processes and by some deep-seated gravitational slope deformations. Among the major landslides, the one that originated the Alleghe lake, the more recent Pontesei landslide and the catastrophic Vajont landslide must be mentioned. Some of the massifs occurring in the Sheet 046 - Longarone are part of the component sites (1,3 and 4) of the serial property Dolomiti UNESCO, listed as part of the World Natural Heritage since 2009, for natural criteria VII and VIII (natural beauty and geology).
Middle and Lower Ordovician series carbonate platform deposits develop well in the north-western Tarim Basin, Kalpin and Bachu outcrop. An integrated analysis of the outcrop, hand specimen, thin slice and geochemical data allows for interpreting the sequence framework, depositional architecture and the response to sea-level changes. The Middle and Lower Ordovician Yingshan and Yijianfang Formations comprise 2 composite sequences (CS1 and CS2) bounded by regional or major unconformities, 5 third-order sequences (Sq1–Sq5) defined by subaerial exposure unconformities or facies changing and 13–15 fourth-order sequences classified by the outcrop depositional cycle change. Twelve microfacies and seven microfacies associations are identified using hand specimens and thin sections. The primary depositional facies include platform margin reef–bank complexes, open platform intraclast or bioclast shoal, intra-shoal and restricted platforms shoal-dolomitic or intra-clastic tidal flats. The research indicates that the carbonate platform evolved from arid and semiarid ramps, restricted platform and dolomitic tidal flat (CS1) to the open and rimmed platform margins (CS2) and eventually was drowned at the end of the Middle Ordovician. The sea-level changes have been studied using the Fischer plot method, showing two sets of long-term shallow–deep–shallow trends. Large-scale transgressions occurred at the lower parts of Sq4, with a significant negative shift of δ¹³C and low-energy mudstone or wackestone depositional architectures. The Fischer plot, lithofacies cycle and the geochemical indicators correlate well and are comparable with Haq's global sea-level changes. Sea-level changes dominate the sequence framework and depositional evolution, and dual factors of sea-level change and tectonic subsidence constrain local Sq3-HST. The high-frequent fluctuation of sea-level changes has a noticeable control effect on the development of fourth-order depositional cycles of carbonate deposits.
In this paper, sea-level fluctuations during the Carnian Pluvial Episode (CPE) are investigated. A revision of published data from multiple successions worldwide indicates a sea-level drop that occurred in different geodynamic settings after the onset of the first of multiple carbon-isotope perturbations that characterize the CPE. New stable isotope data, zircon U-Pb geochronology, carbonate petrology, conodont and foraminifer biostratigraphy from the Carnian of the Sichuan Basin and comparison to the well-dated coeval successions of the Dolomites allow pinpointing with unprecedented precision this sea-level fall and determine that it occurred after the onset of the first, but prior to the third negative δ13C shift of the CPE. These lines of evidence indicate that such sea-level oscillation was eustatic. Facies analysis and sequence stratigraphy of units deposited during the ensuing sea-level rise in the Sichuan and Dolomites, further show that a Tethys-wide crisis of microbial carbonate production and drowning of carbonate platforms were followed by a recovery of marine calcification, widely testified by the deposition of oolitic bodies. Whereas a Tethys-wide recovery of microbial carbonate production is documented at the end of the Carnian, this increase in chemical calcification occurred earlier, at the beginning of the Tuvalian, and suggest that global transformations in carbonate systems coincident with the CPE were complex and share commonalities with other times in the geological record when a similar evolution was linked to ocean acidification.
Over the geological times, shallow–water carbonate environments have always been important ecosystems where marine life abounds, constantly developing and evolving. Carbonate rocks, best witnesses of this marine life, are consequently precious relics to better understand the evolution of life through time and many other environmental aspects directly related. Limestones are therefore essential to characterize with precision and the collection of all its hidden information, whether biological, environmental, climatic or even geographic, is essential. This thesis work thus focuses on the investigation of marine shallow–water Upper Triassic carbonates, some never been studied before. The Triassic is a particular geological period, ranging between two major biological crises, including the great Permian/Triassic one, where almost 95% of marine species disappear. During the Triassic, life therefore strove to rebuild and spread across the oceans, with the rise of many new species, especially within benthic communities. From the end of the Middle Triassic (Ladinian), we witness an extensive development of the reef’s ecosystems, leading to the formation of numerous carbonate platforms, together within the Tethyan domain, partially landlocked in Pangea, and in the gigantic Panthalassa Ocean surrounding the unique continent. The Tethyan carbonates today crop mostly from Europe to Asia while the Panthalassic carbonates occur on the Circum–Pacific region, within accretionary complexes or terranes. Until the late 2000s, the Triassic shallow carbonates developed in Panthalassa were still very little known and studied, unlike the large Tethyan platforms accurately characterized for decades. Faced with this difference in information, the REEFCADE project was therefore developed by Rossana Martini in the 2000s, with the aim of improving our knowledge of these Panthalassic systems and more generally of the evolution of shallow–water carbonates during the Triassic. This thesis work has therefore been conducted as a part of this project and constitutes the logical continuation of various studies initiated by other doctoral students in the frame of REEFCADE. Thus, the study presented in this manuscript has the overall objective of improving our knowledge of carbonate systems in Panthalassa, especially during the Upper Triassic. For such purpose, this work focuses on the very first sedimentological, biostratigraphic, paleontological and diagenetic characterization of carbonates located in two distinct study areas: i) Hokkaido Island, in the northern part of Japan, and ii) the Dalnegorsk area in Russian Far East. These two localities are defined as a west–east succession of Mesozoic accretionary complexes, extending north–south, among which the Taukha terrane (Russian Far East) and the Naizawa Accretionary Complex (Hokkaido, Japan), characterized as Early Cretaceous in age. Mentioned only in very rare scientific publications, numerous outcrops of Triassic carbonates, never precisely studied before, have been reported within these two tectonic elements. During three field missions, the two areas, in Russia and Japan, were therefore extensively explored, and each carbonate outcrop was widely sampled. A total of ten localities, represented by dozens of limestone blocks, were thus investigated during this study. The thesis work mainly focuses on three localities where remarkably well–preserved carbonates were sampled: the Pippu and Esashi districts in Hokkaido (Japan) and the Dalnegorsk area in Russian Far East. Thanks to the thin sections made from each sample, a detailed microfacies analysis was performed to precisely characterize the fossil and abiotic contents for each outcrop. The biological assemblage could thus be compared with similar and synchronous systems, whether of Tethyan or Panthalassic affinity, in order to identify the potential similarities or differences between these two oceans in the scope of paleoecological analysis. In addition, each identified microfacies has been interpreted in term of depositional environment within the carbonate system, on the basis of organism’s type, sedimentary structures, nature of the lithoclasts or the content in carbonate mud. Within the framework of a biostratigraphic approach, a particular attention was addressed to the identification of benthic foraminifers in order to define or specify the stratigraphic extension of the studied carbonates. The combination of all the sedimentological and biostratigraphic data made it possible to reconstruct precise, even speculative depositional models for each investigated system. The Dalnegorsk limestone (Russian Far East), was thus characterized as an atoll–type carbonate system, developed during the Norian on a basaltic seamount in the Panthalassa Ocean, and typified by a great abundance of lagoonal deposits. On the other hand, the outcrops of Pippu and Esashi (Hokkaido Island, Japan) show very strong similarities in age and bioclastic content, and have therefore been interpreted as belonging to the same carbonate system. This last was defined as developed on the flanks of a partially emerged volcanic seamount during the Carnian. The Dalnegorsk limestone was also the subject of an in–depth diagenetic study, supported by in–situ and high–precision geochemical analyzes, in order to characterize each event which impacted the carbonate system, from its deposit to its accretion. Such study, never performed before on Panthalassic carbonates, has indeed made it possible to highlight important diagenetic episodes linked to major environmental changes during the history of the carbonate depositional system and to establish a precise model of evolution of the Dalnegorsk limestone. Analyzes of stable isotopes on various carbonate cements, coupled with trace elements measurements have especially highlighted an emersion of the atoll at the Norian/Rhaetian transition, followed by a dismantling of the flanks of the system during the Lower Jurassic as well as the neomorphism of calcitic shells at the onset of calcitic seas in Toarcian–Bajocian. In total, ten diagenetic events were identified and precisely placed in time thanks to a new method of U–Pb dating applied directly on carbonate cements. Numerous monogenic carbonate breccias have been observed in the field or on thin sections. The geochemical analyzes highlighted two types of breccias, hitherto impossible to differentiate, linked to distinct sedimentary processes and occurring at different stages of the evolution of the carbonate system. This thesis has also been the subject of many scientific collaborations within the REEFCADE project. The compilation of different data from similar past or ongoing studies has indeed led to two major paleontological and sedimentary syntheses. The very first paleontological study of calcareous algae in Panthalassa was thus carried out, leading to results of capital importance both for our understanding of paleoecology and paleogeography of the Triassic oceans but also to better apprehend how the benthic communities were able to spread within the huge Panthalassa Ocean. This study also resulted in the description of six new species of algae. Triassic carbonates from the Sambosan Accretionary Complex (SAC), located in the southern part of Japan have been the subject of numerous studies within the REEFCADE project. During this thesis work, a new sampling campaign, at the Mont Sambosan type locality outcrop (Shikoku Island, Japan), associated with a precise diagenetic study, made it possible to document for the first time the complete history of a carbonate system developed in Panthalassa, since its establishment during the ?Ladinian–Carnian until its dismantling at the Triassic/Jurassic boundary. To conclude, this thesis work constitutes a new major progression for our understanding of the Triassic carbonate systems from the Panthalassa Ocean. This new sedimentological, diagenetic, biostratigraphic and paleontological data complete a rich panel of information obtained within the framework of the REEFCADE project and permit to better constrain the environmental conditions within this vast ocean. The pioneer diagenetic characterization and the fundamental resulting outcomes, open the way to a similar and systematic exploration of synchronous systems to better define the different major environmental events which occur during the Late Triassic and the Jurassic. The combination of all these new data is also of paramount importance for paleogeographic and paleoecological studies, still poorly focused on the Panthalassa Ocean.
Recently intensified research on the mid-Carnian episode stimulated discussions about the mid-Carnian climate and a supposed humid climate shift. This basin-scale study on the Schilfsandstein, the type-example of the mid-Carnian episode, applied sedimentological, palynological and palaeobotanical proxies of the palaeoclimate to a large dataset of cored wells and outcrops. The results demonstrate the primary control of circum-Tethyan eustatic cycles on the Central European Basin where transgressions contributed to basin-scale facies shifts. The palaeoclimate proxies point to a uniform arid to semi-arid Carnian climate with low chemical weathering and high evaporation. Consequently, transgressions into the Central European Basin led to increased evaporation forcing the hydrological cycle. The increased runoff from source areas resulted in high-groundwater stages on lowlands characterized by hydromorphic palaeosols and intrazonal vegetation with hygrophytic elements. During lowstands, reduced evaporation and runoff led to increased drainage and desiccation of lowlands characterized by formation of vertisols, calcisols and gypsisols and zonal vegetation with xerophytic elements. The proposed model of sea-level control on the hydrological cycle integrates coeval and subsequent occurrences of wet and dry lowlands, hydromorphic and well-drained palaeosols, and intrazonal and zonal vegetations. Thus, the Schilfsandstein does not provide arguments for a humid mid-Carnian episode.
Supplementary material: Datasets of Palynomorph Eco Group (PEG) and Macroplant Eco Group (MEG) analyses are available at https://doi.org/10.6084/m9.figshare.c.4182593
According to the recent chronostratigraphic division of Cambrian, the Cambrian strata in the Kelan section can be subdivided into seven third-order sequences (\(\hbox {DS}_{1}{-}\hbox {DS}_{7})\) based on cyclicity in sedimentary facies stacking patterns. The calcareous mudstone forming condensed section, micritic limestone comprising deep to middle ramp facies and the oolitic-grain bank facies in Series 3 and Furongian series represent the basic depositional fabric of Cambrian in northwestern part of Shanxi Province, North China Platform. These massive oolitic grainstones demonstrate that the oolitic-grain bank facies constitute the late-highstand systems tract or forced-regressive systems tract. The grains occupy upper parts of the third-order depositional sequences in response to relative sea-level fall. Furthermore, this forming pattern of oolitic-grain bank facies does not follow the standard model of sequence stratigraphy, in which deposition is believed to occur principally during sea-level rise, rather a continuous erosional unconformity develops during sea-level fall. Moreover, the microscopic analysis of oolitic grainstone shows the development of concentric and radial, rounded or elliptical, with or without nuclei, monocrystalline or polycrystalline, Girvanella or micritic ooids. The occurrence of diversified ooids in varying proportions provides a new dimension for studying evolution of the oolitic-grain bank in the North China Platform. The forming pattern of oolitic-grain bank controlled by their sequence-stratigraphic position in the Kelan section in the Shanxi province provides an important clue and a research direction for the regional correlation, as well as the paleogeographical reconstruction of the Cambrian Series 3 and Furongian series.
In an effort to improve the calibration of the Late Triassic time scale, two stratigraphic successions in Italy were investigated for magnetostratigraphy: the Pignola-2 (Southern Apennines) and the Dibona (Dolomites) sections. These sections reveal a sequence of biostratigraphically calibrated (conodonts and palynomorphs) magnetic polarity zones encompassing the Julian/Tuvalian boundary (Carnian). A total of 63 samples have been collected from the Pignola-2 section that helped defining 3 magnetozones. These data are constrained by a published radiometric U/Pb age of 230.91 0.33 Ma from the Aglianico ash-bed (Furin et al. 2006). From the Dibona section, 81 samples have been collected, revealing 2 magnetozones in the Heiligkreuz Fm. (lower part of the succession) and 2 magnetozones in the Travenanzes Fm. (upper part). The Dibona section provided only few high-quality paleomagnetic data in spite of the sampling effort, so we considered only the Pignola-2 section as suitable for the correlation with other Carnian sections from the literature, in order to define the magnetostratigraphy around the Julian/Tuvalian boundary in the Tethys realm. The correlation between the Pignola-2 and the Newark Astrochronological Polarity Time Scale (APTS) provides independent insights on the age of the base of the Newark basin APTS. We found that the U-Pb zircon-dated Pignola-2 level, magnetostratigraphically projected on the Newark APTS, falls within Chrons E5–E4 at around 231 Ma, in agreement with the (extrapolated) astrochronological ages of the Newark APTS.
Scleractinian corals first appeared during Triassic time in tropical shallow water environments. Controversy surrounds the paleoecology of scleractinian corals of the Late Triassic. Were they like their living counterparts, capable of supporting reefs, or had they not yet coevolved the important association with zooxanthellae that facilitated reef growth and construction? Indirect evidence suggests that some Upper Triassic corals from the Tethys played important constructional roles as reef builders within tropical carbonate complexes of the Tethys. To evaluate this idea, we have employed a geochemical approach based on isotope fractionation to ascertain if Late Triassic corals once possessed zooxanthellae.
We have determined evidence for the ancient presence of algal symbiosis in 13 species of Triassic scleratinians from reef complexes in Turkey and northern Italy. In contrast, two higher latitude Jurassic species used as a control group for isotope analysis, lacked isotopic indications of symbiosis. These findings, together with stratigraphic and paleoecologic criteria, support the contention that Late Triassic scleractinian corals inhabiting shallow-water carbonate complexes of the Tethys were predominantly zooxanthellate, like their living counterparts from present day reefs.
We view the zooxanthellate condition in calcifying reef organisms as a necessary prerequisite for constructional reef development. Our results emphasize the power of stable isotope studies in helping to answer paleobiological questions.
Inhalt Zusammenfassung 435 Summary 436 1. Einleitung 436 2. Der westliche Tethysraum zur Triaszeit 437 3. Zyklischer Sedimentationsablauf 440 3.1. Epikontinentale Triasfazies 440 3.2. Alpin-mediterrane Triasfazies 443 3.3. Orogenetisch beeinflußte Ablagerungsräume der Trias 446 3.3.1. Tethysnordrand 446 3.3.2. Der zirkumpazifische Raum 449 4. Isostatische und taphrogenetische Subsidenz 450 4.1. Subsldenz von der Sedimentationsrate kontrolliert (isostatische Subsidenz) 452 4.2. Beispiele für taphrogenetische Subsidenz 453 4.3. Subsidenz und zyklische ~edimentation im Wettersteinlagunenkalk und anderen cordevolischen Karbonatplattformen; Zusammenhänge zwischen Subsidenz und Regressionen 455 5. Bedeutende tektonische Ereignisse 460 5.1. Montenegrinische Phasen 460 5.1.1. Orogenese oder Taphrogenese? 460 5.1.2. Räumliche Verbreitung der anisischen Hebungszonen 463 5.2. Bemerkungen zu den tektonischen Bewegungen des Ladin-Karn (Labinische Phasen) und zum Vulkanismus 465 6. Korrelation relativer Meeresspiegelschwankungen und tektonischer Ereignisse im westlichen Tethysraum 467 6.1. Tektonisch induzierte Meeresspiegelschwankungen? 467 7. Schlußbetrachtung 470 Dank 471 Literatur 471 Zusammenfassung In der Trias des alpin-mediterranen Raumes und der epikon-tinentalen Randzonen konnten eine Reihe von synchronen Zyklen relativer Meeresspiegelhebungen und -senkungen fest-gestellt werden. Im tektonisch mobilen, alpin-mediterranen Raum war dies erst nach dem Studium der lokalen Faziesent-wicklungen, der Subsidenz und der triassischen Tektonik mög-lich. Überregionale Bedeutung haben die beiden langfristigen Transgressions-Regressionszyklen während der Mittel-und Obertrias. Diese werden vor allem am Beginn und am Ende von kurzfristigen Meeresspiegelschwankungen überlagert, wo-") Habilitationsschrift (geringfügig ergänzt) zur Erlangung der Lehrbefugnis an der Naturwissenschaftlichen Fakultät der Leo-pold-Franzens-Universität zu Innsbruck. "") Anschrift des Verfassers: Dr. RAINERBRANDNER, Institut für Geologie und Paläontologie der Universität Innsbruck, Univer-sitätsstraße 4/2, A-6020 Innsbruck.
This paper presents a detailed facies analysis
and paleo-depth reconstruction of a latest Early Carnian
platform drowning-sequence from the Anatolian terrane
(Turkey, Taurus Mountains). A total of eight sedimentary
microfacies zones were recorded. An open platform margin
passes through a deeper shelf margin setting into a basinal
environment influenced by more open-marine conditions.
The analysis demonstrates an unexpected, pure carbonate
depositional system through the so-called Carnian Pluvial
Episode (CPE), which has previously been associated with
dramatic climate changes throughout the Tethys region.
One main finding, based on sedimentological and paleontological
analyses, is a much later drowning of the carbonate
platforms in Turkey than in other places. The
termination of the Kartoz platform postdates the onset of
the CPE in the western Tethys by one ammonite zone,
corresponding to about 2 million years. The distinctly
earlier demise of (north)western Tethyan carbonate platforms
and reefs points to a diachrony of this event
throughout the Tethys. The decline of carbonate productivity
clearly occurs earlier at higher paleolatitudes and
later in equatorial areas. Interpreting the CPE as the result
of a global or at least Tethys-wide climatic event is
therefore highly ambiguous. The described facies changes
at As¸ag˘iyaylabel probably mirror different coupling effects
and, only minimally, the Tethyan-wide climate changes
during the Carnian Pluvial Episode.
Microbialites are organosedimentary deposits formed from interaction between benthic microbial communities (BMCs) and detrital or chemical sediments. Processes involved in the formation of calcareous microbialites include trapping and binding of detrital sediment (forming microbial boundstones), inorganic calcification (forming microbial tufa), and biologically influenced calcification (forming microbial framestones). Microbialites contrast with other biological sediments in that they are generally not composed of skeletal remains. -from Authors
Detailed geologic cross sections, augmented by laboratory calibration of lithology and acoustic impedance, have been used to produce synthetic reflection seismic sections of a carbonate foreslope-to-basin transition. Two areas from the Picco di Vallandro region of the Dolomite Alps were modeled: a progradational section and a retrogradational (backstepping) section. The resulting models show how these complex areas of strata interfingering might be displayed on conventional reflection seismic lines. In the area of progradation, rapid stratigraphic thinning below seismic detectibility, coupled with abrupt impedance changes, produces a reflection discontinuity between steeply dipping reflections of the foreslope and gently dipping paralle reflections of the basin section. This apparent downlap surface marks the toe-of-slope for successive clinoforms but dose not correspond to a discrete stratigraphic surface. In the backstepping example, similar stratigraphic thinning and impedance changes create an apparent onlap surface. Wavelet interference causes complications in both examples. These models indicate how stratigraphic complexity can be simplified by the seismic reflection process and suggest that caution should be exercised when using seismic data to construct general models in areas of complex depositional geometries and rapidly changing facies.
The Gulf of Mexico is a small ocean basin lying between the North American plate and the Yucatan block. Following initiation in the Middle Jurassic, sea-floor spreading continued approximately 25Myr. Spreading was asymmetric, creating a broad area of attenuated transitional continental crust beneath the northern basin. Initially, widespread, thick salt deposits accumulated across much of the basin; mobilization of this salt by subsequent sedimentary loading has created a complex suite of gravity tectonic structures. Most salt is now allochthonous, forming extensive stocks and canopies. By the end of the Mesozoic, thermal subsidence had created a deep basin floor, flanked by continental shelves. The resultant basin contains a succession of Late Jurassic through Holocene strata that is as much as 20km thick. Sediment supply from the North American continent has filled nearly one-half of the basin since its inception, primarily by offlap of the northern and northwestern margins. Depositional history can be generalized in seven phases: (1) Middle-Late Jurassic evaporite and carbonate deposition in a broad, shallow, restricted to open marine basin. (2) Latest Jurassic-Early Cretaceous sand-rich clastic progradation from the northern margins. (3) Late-Early Cretaceous development of a rimmed carbonate shelf. (4) Late Cretaceous mixed clastic and carbonate aggradation of the continental margins. (5) Resurgent Paleogene clastic progradation and filling centered in the NW basin. (6) Miocene progradation and basin filling centered in the central and NE Gulf. (7) Late Neogene climatically and eustatically influenced progradation along the central Gulf margin. In contrast to the broad, progradational sediment wedge of the northern Gulf, the Florida margin is a primarily aggradational carbonate platform.
Summary A 95 m long section (Lacke section) located in the Norther Calcareous Alps of Austria was analyzed in detail. Detailed field
measurements and point-counting of thin-sections revealed a distinct compositional variation of calciturbidites deposited
in the Triassic Hallstatt Basin (Pedata-Ptschen Schichten). After a pilot study seven point-count groups were developed distinguishing
input from different paleoenvironments. Statistical analysis of the point-count data using summary statistics, cluster-and
correspondence analysis assisted in describing the compositional variation within the calcuturbidites. Alternated flooding
and exposure of the platform as a result of sealevel fluctuations, creating and destroying shallow-water habitats on the flat
platform top, produced the variations in turbidite composition.
Facies analysis of the Durrenstein Formation, central-eastern Dolomites, northern Italy, indicates that this unit was deposited on a carbonate ramp, as evidenced by the lack of a shelf break, slope facies, or a reef margin, together with the occurrence of a ''molechfor'' biological association. Its deposition following the accumulation of rimmed carbonate platforms during the Ladinian and Early Carnian marks a major shift in growth mode of the Triassic shallow marine carbonates in the Dolomites. The Durrenstein Formation is characterized by a hierarchical cyclicity, with elements strongly suggestive of an allocyclic origin, including (a) subaerial exposure features directly above subtidal facies within meter-scale cyclothems, (b) purely subtidal carbonate cyclothems, (c) symmetric peritidal carbonate cyclothems, and (d) continuity of cyclothems of different orders through facies boundaries. The Durrenstein cyclothems are usually defined by transgressive and regressive successions, and so most of them probably originated from sea-level oscillations. Their allocyclic origin allows their use for high-resolution correlations over distances up to 30 km. A stratigraphic section in the Tre Cime di Lavaredo area, encompassing the upper part of the Durrenstein Formation and the lower part of the overlying Raibl Formation (Upper Carnian) was studied using time-frequency analysis. A strong Milankovitch signal appeared when interference arising from a variable sedimentation rate was estimated and removed by tuning the short precession line in a spectrogram. All of the principal periodicities related to the precession index and eccentricity, calculated for 220 Ma, are present: P1 (21.9 ky); P2 (17.8 ky); E1 (400 ky), E2 (95 ky), and E3 (125 ky), along with a peak at a frequency double that of the precession, which is a predicted feature of orbitally forced insolation at the equator. Components possibly related to Earth's obliquity at ca. 35 ky and ca. 46 ky are present as well. The recovery of Milankovitch periodicities allows reconstruction of a high-resolution timescale that is in good agreement with published durations of the Carnian based on radiometric ages. The recognition of a Milankovitch signal in the Durrenstein and lower Raibl formations, as well as in other Mesozoic carbonate platforms, strongly supports a deterministic and predictable-rather than stochastic-control on the formation of carbonate platforms. Carbonate platforms might thus be used in the future for the construction of an astronomical time scale for the Mesozoic.
Generally arid conditions that pervaded much of Europe and North America during the late Triassic were interrupted by a wet monsoonal climatic phase during Middle and Late Carnian times. Extensive fluviatile sandstones deposited at this time throughout the region, occur within a thick sequence of playa-lake mudstones. The sandstones occasionally contain kaolinite, suggesting a humid climate. An extreme δ ¹³ C depletion in a shallow marine sequence of this age in Israel has been interpreted as evidence for an influx of freshwater. A widespread change from carbonates to clastics in marine sequences at this time may also be climate-related. Water-course cave systems in limestone areas exposed during the late Triassic indicate high levels of runoff during the Middle and Late Carnian.
The marine invertebrate fauna shows a significant turnover at the end of the Early Carnian. The terrestrial fauna and flora were relatively unaffected at this time but subsequently diversified prior to a major biotic turnover at the Carnian-Norian boundary. These periods of biotic change appear to be synchronous with the onset and cessation of a Carnian humid phase.
The change to a monsoonal climate during this interval has been documented over more than 90° of longitude between 5° and 50° north of the Triassic equator. It may have been caused by rising atmospheric CO 2 levels due to volcanism associated with the incipient dispersal of Pangaea.
The Triassic time scale is poorly constrained due to a paucity of high-precision radiometric ages. We present a 206Pb/238U age of 230.91 ± 0.33 Ma (error includes all known sources) for zircon from an ash bed in the upper Carnian (Upper Triassic) of southern Italy that requires a major revision of the Triassic time scale. For example, the Norian stage is lengthened to more than 20 m.y. The section containing the ash bed is correlated with other Tethyan sections and, indirectly, with the Newark astronomical polarity time scale (APTS). The dating provides also a minimum age for some important climatic and biotic events that occurred during the Carnian. We note a coincidence between these events and the eruption of the large igneous province of Wrangellia, but the possible link between volcanism and climatic and biotic events requires further scrutiny.
The debate on the geometry and origin of shelf sandbodies has evolved from a discussion of how sands and gravels managed to move from shorelines far out onto muddy shelves to an acceptance that many of these sandbodies did not originate on the shelf but were simply resident there after a fall and subsequent rise of sea level. In the efforts to reinterpret these sandstones there has been some tendency to underestimate how varied they can be. Data from eight such shelf sandstone tongues (Campanian) in southeast Wyoming are used to illustrate how variable lowstand prograding wedges can be and how these should, in addition, be distinguished from forced-regressive wedges. The depositional environments encountered in these two types of wedges are surprisingly different, and the lowstand wedges, which are frequently tidally influenced, show a greater affinity with the overlying transgressive tract than with the preceding wave-dominated, forced-regressive shoreface deposits.
Although the Late Triassic was a time of widespread aridity, evidence
exists for a significant increase in rainfall during the middle to late
Carnian. Upper Triassic playa-lake sediments were interrupted by late
Carnian fluviatile sandstones with erosive bases and high
kao-linite/illite ratios. There was also an increase in the clastic
component of marine sequences during this interval. Middle and upper
Carnian marine carbonates show an extreme depletion in
δ13C values, consistent with increased fresh-water
influx. Large-scale karstic phenomena in limestone areas subaerially
exposed during the Late Triassic are a further indication of increased
rainfall. Important faunal and floral changes occurred during the
Carnian-Norian interval; marine invertebrate turnover was greatest at
the lower/middle Carnian boundary, and terrestrial extinctions were
concentrated at the Carnian/Norian boundary. The cause of this Carnian
pluvial episode may have been related to the rifting of Pangea, through
disruption of atmospheric and oceanic circulation patterns, eustatic
changes, or the effects of volcanism associated with rifting. A change
in surface ocean temperature, salinity or pH, or habitat loss may have
caused the decline of many shallow-marine invertebrates at the start of
the middle Carnian; a return to arid conditions at the Carnian/Norian
boundary would account for the turnover among terrestrial vertebrates
and plants.
The Global boundary Stratotype Section and Point (GSSP) for the base of the Carnian Stage (Late Triassic) is defined on the north flank of the Cordevole Valley, on the southern slopes of the crest separating the Badia/Abtei and the Cordevole valleys (46° 31' 37"N, 11° 55' 49"E) at an elevation of 1980 m, approximately 4.7 km south of San Cassiano/St. Kassian in the
Dolomites (Southern Alps). The Prati di Stuores/Stuores Wiesen section (Province of Belluno, Veneto Region, Italy) is located a few hundred meters east of Pralongià, a locality northeast of Arabba (Belluno). The section consists of hemipelagites and thin turbidite beds (both siliciclastic and carbonate intraclastic), deposited below storm wave-base with a high but variable sediment accumulation rate (San Cassiano Fm.). The GSSP boundary is located at the base of bed SW4, 45 m above the base of the San Cassiano Fm. Bed SW4 yielded ammonoids including Daxatina canadensis (Whiteaves), which is the primary global marker for identifying the base of the Carnian Stage. The secondary marker for the Carnian Stage, the conodont Paragondolella polygnathiformis (Budurov and Stefanov), appears 70 cm
above the first occurrence of Daxatina canadensis and at the base of a long normal-polarity magnetic zone (S2n) in close proximity to the boundary. Furthermore, the GSSP is located one ammonite subzone just above a level dated at 237.77 ± 0.14 Ma.
Introduction What happened at the end of the Early Carnian, some 235-230 million years ago? All over the Dolomites, the lower-upper Carnian transition is evident from the distance as a break between the majestic rock walls of the massive Cassian Dolomite and those of the well bedded Dolomia Principale. This morphological step is stri-kingly evident, for example, all around the Sella Platform, and locally evolved to extended plateaus, as below the Tre Cime di Lavaredo or at Lagazuoi, north of Passo Falzarego. Even the slopes of Col Gallina and Nuvolau, uniformly dipping northward toward Passo Falzarego, are structural surfaces representing the exhumed plat-form top of the demised lower Carnian Cassian Dolomite (Fig. 1). And here our excursion starts. The aim of this field trip is twofold. On the one hand, evidence will be shown of a climatic swing from arid, to humid, and back to arid climate in the Carnian of the Tofane area. We here denote the whole climatic episode, regardless of its polyphase nature, as the "Carnian Pluvial Event". On the other hand, the effects of this climatic event on sedimentation and biota will be illustrated, from the km scale of carbonate platform geometries to the smaller scale of facies associations and lithologies. The mor-phological features of famous mountain groups of the Dolomites, as depicted above, are a direct consequence of the sedimentary turnover triggered by the Carnian Pluvial Event.
The analysis of the type-sections of Tor Formation and Carnitza Formation in the neighbourhood of Raibl/Cave del Predil (Tarvisio area, Julian Alps, Italy) allows a better definition of the Carnian stratigraphic and sequence stratigraphic framework in this classical area. Ammonoids and palynomorphs confine the age of the Conzen Formation and of most of the Tor Formation to the Julian, while the uppermost Tor Formation, the Carniza Formation and the base of the Dolomia Principale are Tuvalian in age. In the Tarvisio area, a margin-foreslope system of the Dolomia Principale, interfingering with basinal sediments (Carnitza Formation) is exceptionally well preserved at a seismic-scale. This setting allows a better comprehension of the start-up of the Dolomia Principale carbonate platform.
The Dolomites region is a spectacularly exposed portion of the Southern Alps, a northern Italian chain derived from the comparatively gentle deformation of the Tethyan passive continental margin of Adria. The region had an active Permo-Jurassic tectono-magmatic evolution, leading from Permian magmatism, through a Middle Triassic episode of fast subsidence and volcanism, to the Jurassic oceanic break-up. Although the sedimentary succession ranges in age from Middle Permian to Cretaceous, the geological landscape is largely dominated by the majestic Triassic carbonates, making the area a classical one for the early Mesozoic stratigraphy. Particularly noteworthy are the Anisian to Carnian carbonate platforms, recording an evolution from regional muddy banks to isolated high-relief buildups. The filling of the various basins and the development of a last generation of regional peritidal platform followed. The carbonate platforms of the Dolomites bear witness to a remarkable set of changes in the carbonate production and to significant palaeoclimatic fluctuations, from arid to moist conditions and vice versa; a great range of margin and slope depositional styles is therefore recorded. Alpine tectonic shortening strongly affected the area, with a first Eocene deformation, followed by later Neogene overthrusting and strike-slip movements.
A redefinition of the lithostratigraphy is made, and the presence of three terrigenous units of different ages (Piz da Peres Conglomerate, Voltago Conglomerate and Richthofen Conglomerate), as well as two carbonate platforms (Upper Serla Formation and Contrin Formation), is documented. This stratigraphic setting correlates well with other Anisian sections outcropping in the Dolomites and in the Recoaro area. Using sequence stratigraphy as an intergrated approach, four Anisian depositional sequences are identified. Preliminary results indicate that these sequences can be recognized throughout the Dolomites and the Recoaro area, and might even extend to the Southern Alps. -Authors
Sequence boundaries were originally defined as bounding surfaces of conformably stratified units. Within this descriptive definition, two types of boundaries were specifically recognized and widely used—the boundary between highstand and lowstand systems tracts and that between highstand systems tract and shelf-margin wedge. A third type of boundary, the flooding surface between a highstand tract and an overlying transgressive tract, is increasingly used as a sequence boundary, particularly in carbonates. It should be formally recognized as a specific type of sequence boundary because it is prone to developing long submarine hiatuses, occurs commonly in the geologic record, particularly on drowned carbonate platforms, tends to be a pronounced reflector and unconformity in seismic images, and represents a logical third combination in the interplay of subsidence and eustasy—one in which the rate of subsidence exceeds even the most rapid fall of sea level during a particular eustatic cycle. Including type 3 unconformities as sequence boundaries has two advantages: (1) the general definition of sequence boundary remains descriptive and thus workable even where the boundary must be drawn solely on geometric grounds without supporting evidence for sea-level fall and exposure, and (2) the designation of boundary types 1 and 2 can be restricted to surfaces with reliable evidence for relative fall in sea level.
On drowned reefs and carbonate platforms, the hiatuses associated with type 3 unconformities frequently exceed 10 m.y., occasionally even 100 m.y. Relicts of pelagic cover in hardgrounds, along with marine diagenesis, attest to the submarine, erosional nature of these hiatuses. On rapidly flooded siliciclastic shelves, the effects are similar but less pronounced. The mechanism behind this persistent and powerful marine erosion is amplification of sluggish oceanic tides by the interaction with sharp topography. This process continues and expands the effects of marine shoreface erosion at greater water depth.
Over the past few years research on Triassic in the southern Alps has made it possible to collect a great number of ammonoids bed by bed from both known and new sections. A comparison of these data and their integration with known data throughout the Tethys has made it possible to elaborate a well documented frame of the ammonoid fauna in Middle Triassic. By applying the principle of major events, faunal turnovers not controlled by local factors were defined. The integration between the hierarchy of biological events and the hierarchy of chronostratigraphic units suggest a detailed and, as far as possible, not conjectural, biochronostratigraphic setting of ammonoids. A synthesis of the new standard scale due to be published soon, is presented. -from Authors
During Early and early Late Triassic times, the Northern Calcareous Alps (Austria, southern Germany) and the Dolomites (northern Italy) were situated at the margin of the western Tethys. In the Scythian, widespread clastic-carbonate deposition on the shelf prevailed. Carbonate ramps revived in the earliest Anisian. From the late Anisian to the early Ladinian, carbonate ramps evolved to rimmed carbonate platforms. The Dolomites comprise five Scythian sequences, controlled by low amplitude sea-level changes and progressively increasing tectonic subsidence rates. During the Anisian to Ladinian, the sea-level fluctuations increased in amplitude. Five Anisian, three Ladinian and two early Carnian depositional sequences developed. Tectonic subsidence rates changed significantly over intervals of 2–5 Ma in the northwestern Dolomites, but developed steadily in the northeastern Dolomites. The Northern Calcareous Alps comprise two Scythian, five Anisian, four Ladinian and two early Carnian depositional sequences. The completely marine succession were only weakly affected by early tectonics. A distinct increase in subsidence occurred in the late Ladinian, leading to the change from distally steepened ramps to rimmed platforms. Only during this time interval, a rapid tectonic subsidence signal overprinted the sea-level signal.
Excellent outcrops of the upper Pliocene-lower Pleistocene Calcarenite di Gravina around Matera (southern Italy) provide continuous exposure of coarse-grained, clastic basin-margin, shoreline to offshore facies. Among these facies, the most conspicuous and volumetrically important are the transition-slope deposits that form large-scale, high-angle, cross-bedded lithosomes. These are laterally extensive, parallel with the paleoshoreline, and show seaward progradation. We interpret them to represent avalanches of sediment swept out onto a depositional slope, below wave base, from the shoreface zone by storm waves and wind-driven currents. Three types of building blocks are recognized based on bedding patterns and facies architecture: embryonic parasequences, mature parasequences, and simple sequences. Parasequences formed during stillstands of sea level and simple sequences during high-frequency cycles of relative change of sea level. These building blocks are stacked in a backstepping configuration and onlap onto Cretaceous limestone substrate. Backstepping is believed to be due to a tectonically forced transgression that is punctuated by high-frequency cycles of sea level. Modern analogs for these building blocks are the Holocene prograding prisms detected in high-resolution seismic lines of the Mediterranean shelves. The reflection patterns of these seismic units resemble the bedding architecture of the Matera simple sequences and parasequences and show similarities of shape, size, position, and orientation of coastal setting, and direction of progradation. Comparison of the Holocene prisms and the Pliocene-Pleistocene accretional units in Matera indicates that they may represent the same genetic process, progradation of clastic prisms below the wave base level. The Matera accretional units also show similarities with other examples of laterally extensive, large-scale, cross-bedded sand bodies encased in offshore deposits, such as some sandbanks. Differentiating between these laterally extensive and seaward-prograding cross-bedded sand bodies and some coarse-grained Gilbert-type deltas is difficult, however, if interpretations are based only on two-dimensional (2-D) outcrops in dip section. Without high-resolution data it is also difficult to distinguish between transition-slope and prograding shoreface lithosomes. This difficulty may be acute where only seismic or well-log data are available; however, certain other architectural characteristics, such as stacking and preservation of facies belts and position of bounding surfaces, as well as differences in associated sedimentary structures and fossil content, may be used for interpretation. The Matera example provides a mechanism for emplacement in offshore settings of elongate and strandline-parallel sand and gravel deposits that prograde seaward and that preserve a coarsening-upward internal succession. This article offers an interpretation for other ancient examples of large-scale, cross-bedded lithosomes encased in offshore deposits.
Because rates of carbonate production and bioerosion are similar, even modest increases in nutrient avalability can shift a reef community from net production to net erosion. In the geologic record, drowned reefs and carbonate platforms typically exhibit evidence of nondeposition, bioerosion, and reduced redox potential, which indicate excess nutrient availability during drowning. -from Authors
The Carnian pluvial event (CPE) is considered as the drastic environmental change that occurred in the western Tethys during the Carnian (Late Triassic). Although some studies have suggested that the CPE was a global event, no studies have referred to pelagic environment related to the CPE. To reveal the pelagic environment during the Carnian, X-ray absorption fine structure (XAFS) analysis was used to determine the iron (Fe) species in chert samples collected from the Ladinian–Carnian strata in the Tamba–Mino–Ashio Belt, Japan. The X-ray absorption near-edge structure (XANES) analysis shows that all the red cherts contain hematite with a combination of clay minerals, such as illite, chlorite, and smectite. The existence of these minerals is identified using extended XAFS (EXAFS). The XANES analysis of the green and the white cherts does not show any hematite signatures, while the EXAFS analysis indicated increasing amounts of chlorite.
Earlier stratigraphic work had predicted that at the type section of the Castlegate Formation, the Castle Gate, near Price, Utah, the unit consists of two sequences separated by a sequence boundary representing approximately one million years of unrecorded time. Al- though the type section is well exposed, it consists of a monotonous succession of braided fluvial sandstones and no obvious boundary can be identified using facies criteria—this is a good example of a ''cryptic sequence boundary.'' Petrographic data indicate, however, a signifi- cant change in detrital composition 20 m above the base of the section, at a through-going erosion surface that is therefore interpreted as the sequence boundary. Revised sequence correlations, together with other petrographic data and regional paleocurrent patterns, provide the basis for a model of the paleogeographic evolution of the area. Rocks assigned to the Cas- tlegate Sandstone comprise two or possibly three sequences formed at times of slow regional subsidence. Erosional sequence boundaries and tilts in paleoslope between each sequence record thrust loading and unloading of the basin and the growing influence of intrabasinal up- warps, movement of which was beginning to be affected by Laramide movements toward the end of Castlegate sedimentation.
The Paleogene fill of the northwestern Gulf of Mexico basin consists of eight genetic stratigraphic, sequences bounded by regional marine flooding surfaces. Calculation of sediment accumulation rates along dip profiles through four subbasins shows that regional changes in accumulation rate---and by inference, rate of sediment supply---of fivefold to tenfold repeatedly occurred over time spans of 1 to 3 m.y. Major sequences record episodes of high supply and accommodation-limited accumulation. Periods of declining and low supply were characterized by short-term over-accommodation and consequent transgressive flooding of the basin margin. Within sequences, depositional rates varied with position relative to the contemporaneous shelf margin, with type of depositional system, and between subbasins. Normal patterns of load-induced basin-margin subsidence and creation of accommodation space were modified by perturbation of the crustal stress regime.
Upper Pliocene-lower Pleistocene shallow-marine temperate-water carbonates of the Calcarenite di Gravina Formation crop out in the Murge area of Puglia, SE Italy, and record a regional subsidence-driven transgression that was punctuated by higher-frequency forced regressions. Sedimentation occurred during the drowning of a complexly faulted island archipelago whose bedrock was exclusively composed of deformed Cretaceous platform carbonates. High-energy temperate-water bioclastic carbonate systems dominated marine environments, but bioclasts were locally mixed with carbonate lithoclasts derived from the Cretaceous limestones bedrock and supplied to the shoreline via ephemeral rivers. This setting allows us to compare the depositional response of bioclastic-dominated and mixed bioclastic-lithoclastic temperate-water carbonate systems to relative sea-level changes, and in particular to forced regressions within a long-term transgressive sequence set. Bioclastic dominated temperate-water carbonate systems are comprised of a nearshore non-depositional abrasion zone and an offshore accumulation zone; long-term subsidence led to erosional transgression through nearshore abrasion and bioerosion of the drowning archipelago. The bioclastic-dominated carbonate system was best developed during relative sea-level rises and highstands, with offshore cyclic subtidal carbonate successions interpreted to record higher-frequency relative sea-level fluctuations. Forced regressions and lowstands were associated with basinward migration of the abrasion zone and development of a subaerial exposure surface that passed basinward into marine rock- and softgrounds on the shelf; little additional sediment was supplied from updip karstic areas of the island archipelago where superficial drainage was limited. In contrast, mixed bioclastic-lithoclastic carbonate systems are characterized by reciprocal sedimentation, developed where ephemeral rivers supplied carbonate lithoclasts to the shoreline. In these systems, bioclastic sedimentation typified relative sea-level rises and highstands whereas forced regressions and lowstands were associated with the development of coarse lithoclastic deposits. Forced regressive-lowstand deposits are represented by narrow progradational gravel beaches in ramp settings whereas small coarse-grained deltas formed against steep fault-bounded coastlines; both lack an aggradational component. Lower surfaces of the forced regressive-lowstand units are sharp and record abrupt basinward facies shifts. However, these basal surfaces were largely inherited, formed in the nearshore abrasion zone of the preceding transgressive-highstand bioclastic-dominated carbonate system. Rockgrounds formed in this way were not substantially modified by marine shoreface erosion during sea-level fall. The upper bounding surfaces of the forced regressive/lowstand deposits are also marine in origin and developed in response to rapid sea-level rise and landward translation of the shoreline. These surfaces were associated with nearshore abrasion and ravinement so that subaerial exposure surfaces were reworked in the marine environment and have very low preservation potential. Accordingly, the forced regression/lowstand sediment bodies are bounded by marine erosion surfaces and enclosed within sediments and/or surfaces formed in offshore environments.