Article

Late Triassic reefs from the Northwest and South Tethys: Distribution, setting, and biotic composition

November 2005
Facies 51(1):442-453

November 2005
51(1):442-453

Authors:

German University of Technology in Oman

The paleolatitudinal distribution patterns during Ladinian and Carnian time are characterized by an increasing expansion of reefs from the northern to the southern hemisphere. The optimum of reef diversity and frequency in the Norian is associated with the development of extended attached or isolated carbonate platforms. Norian-Rhaetian sponge and coral reefs of the Northern Calcareous Alps developed (1) as reef belt composed of patch reefs in platform-edge positions facing the open-marine northwestern Tethys basins and (2) as patch reefs in intraplatform basins as well as in ramp positions. Carnian and Norian-Rhaetian sponge and coral reefs of the Arabian Peninsula are formed (1) as reef complexes at the margins of carbonate platforms on the tops of volcanic seamounts in the southern Tethyan ocean, as small biostromes on these isolated platforms, and (2) as transgressive reef complexes on the attached platform of the Gondwana margin. The Norian Gosaukamm reefal breccia of the NW Tethys is a counterpart of Jabal Wasa reefal limestone of the Gondwana margin with similarities in geological setting and biotic composition. Rhaetian coral biostromes of low diversity known from the Austrian Koessen basin resemble to the time equivalent Ala biostromes of the isolated Kawr platform in the southern Neo-Tethys by forming a discontinuous layer in shallow intraplatform basin setting.

Paleogeographic map of the Late Triassic (simplified after Scotese and Golonka 1992): the arrows show the approximate loca- tion of the Dachstein platform in the NW Tethys and the Arabian platform at the Gondwana margin

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Late Triassic lithology of the Northern Calcareous Alps, Austria ( A ) (Zankl 1971) and the Oman Mountains ( B ) (Glennie et al. 1974) from platform to basin

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Palinspastic reconstruction of the Northern Calcareous Alps, Austria ( A ) and the Oman Mountains ( B ) from platform to basin

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Model of the Dachstein platform, Austria with the position of reefs ( A ) (modified after Zankl 1971) and the Arabian platform margin with the Sumeini slope ( B ) (modified after Watts and Garrison 1986)

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Triassic reef types and dominant reef builders (defined by Flügel 2002) and their occurrences in the southern Tethys (S)

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Facies character and evolution of a mixed carbonate–siliciclastic shelf: Upper Triassic–Lower Jurassic succession in the eastern Northern Calcareous Alps (Stumpfmauer, Austria)

Article

Full-text available

Jun 2023

Western Tethys sedimentary successions constitute fundamental archives of Late Triassic–Early Jurassic environmental, carbonate production and tectonic changes. During the Late Triassic, the Northern Calcareous Alps (Austria) belonged to the Western Tethys passive margin, characterised by the deposition of the early-dolomitized peritidal Hauptdolomit (Norian) adjacent basinward to the Dachstein carbonate shelf and passing upward to the mixed carbonate–siliciclastic Kössen Formation (Upper Norian–Rhaetian). The Kössen Fm. was subdivided into the lower shallow-water Hochalm Member and the upper Eiberg Member, accumulated in an intraplatform basin coeval to shallow-water carbonates (Upper Rhaetian Limestone). The Eiberg Mb. and overlying Jurassic strata were extensively studied as a continuous marine record across the Triassic/Jurassic boundary. In contrast, shallow-water successions, time-equivalent to the Eiberg Mb. and Upper Rhaetian Limestone, located North of the Eiberg Basin, are poorly investigated. This study focusses on the approximately 350 m thick Norian to Lower Jurassic succession cropping out in the eastern Northern Calcareous Alps (Stumpfmauer). The 32 distinguished lithofacies compose seven, vertically superimposed, sedimentary units (A–G), belonging to the Hochalm Mb. of the Kössen Fm. (Unit A peritidal cyclothems, Unit B claystone/marlstone with fossiliferous beds, Unit C coral boundstone to floatstone), Upper Rhaetian Limestone (Unit D subtidal cyclothems with claystone), shallow-water carbonate strata transitional to Lower Jurassic (Unit E ooidal coated grain peloidal grainstone with basal transgressive lag, Unit F bivalve-rich, microbialite and oncoidal lithofacies, previously attributed to the Upper Rhaetian Limestone) and Hettangian–Sinemurian Kalksburg Fm. (Unit G cross-laminated coated grain peloidal grainstone with quartz and chert). The detailed lithofacies characterisation presented in this study contributes to the knowledge on the Northern Calcareous Alps stratigraphy and depositional environments across the Triassic/Jurassic boundary. The identified sedimentary units can be framed in the evolution of Western Tethys and share similarities with depositional systems from the Western Carpathians, Transdanubian Range, Southern Alps and Dinarides suggesting coherent sedimentary response and environmental, climate and tectonic controls in different palaeogeographic domains.

A glimpse of the lost Upper Triassic to Middle Jurassic architecture of the Dinaric Carbonate Platform margin and slope

Article

Full-text available

Dec 2022

In the southernmost outcrops of the Slovenian Basin the Middle Jurassic coarse-grained limestone breccia (mega)beds are interstratified within a succession that is otherwise dominated by hemipelagites and distal turbidites. In this paper, these beds are described as the Ponikve Breccia Member of the Tolmin Formation. We provide descriptions of the studied sections with detailed geological maps and analysis of the breccia lithoclasts. From the latter, a non-outcropping margin of the Dinaric Carbonate Platform is reconstructed. In the Late Triassic the platform margin was characterized by a Dachstein-type marginal reef. After the end-Triassic extinction event, the platform architecture remained, but the reefs were replaced by sand shoals characterized by ooids. In the late Early Jurassic and/or early Middle Jurassic a slope area might have been dissected by normal faults and a step-like paleotopography was formed. In the Bajocian, during a period of major regional geodynamic perturbations, extensional or transtensional tectonic activity intensified and triggered the large-scale collapses of the Dinaric Carbonate Platform margin producing the limestone breccias described herein. This may in turn have caused a backstepping of the platform margin, as is evident from the occurrence of Late Jurassic marginal reefs that are installed directly above the Upper Triassic and Lower Jurassic inner platform successions.

Upper Triassic Carbonate Records: Insights from the Most Complete Panthalassan Platform (Lime Peak, Yukon, Canada)

Article

Full-text available

Jul 2022

Upper Triassic carbonate platforms from the Panthalassa Ocean remain less-understood and less-studied than their Tethyan equivalents. This imbalance is largely due to the poorer preservation state of Panthalassan carbonate rock successions in terms of rock quality and depositional geometries, which prevents good appreciation of depositional systems. In this context, carbonate exposures from Lime Peak (Yukon, Canada) represent an outstanding exception. There, the remains of an Upper Norian Panthalassan carbonate platform are well-exposed, show remarkably preserved depositional geometries and overall superior rock preservation. In this work, we analyse the carbonates from the Lime Peak area with particular attention to the vertical and lateral distribution of biotic assemblages and microfacies at the platform scale. Results demonstrate that the Lime Peak platform was surrounded by a basin with an aphotic sea bottom. The carbonate complex developed in warm waters characterized by high carbonate saturation. The area was also defined by moderate to high nutrient levels: this influenced the type of carbonate factory by favouring microbialites and sponges over corals. During its growth, Lime Peak was influenced by tectono-eustatism, which controlled the accommodation space at the platform top, primarily impacting the internal platform environments and the stability of the slope. Gaining better knowledge of the spatial distribution and dynamics of Upper Triassic organisms and sedimentary facies of Panthalassa in relation to tectono-eustatism lays the first foundations for reconstructing more robust platform models and understanding the evolution of other, more dismantled Upper Triassic Panthalassan carbonate systems through time.

Paleoecology, biogeography, and evolution of reef ecosystems in the Panthalassa Ocean during the Late Triassic: Insights from reef limestone of the Sambosan Accretionary Complex, Shikoku, Japan

Article

May 2016
PALAEOGEOGR PALAEOCL

From fore reef to lagoon: Evolution of the upper triassic dachstein carbonate platform on the tennengebirge (Salzburg, Austria)

Article

May 2014

Carnian and Norian (Upper Triassic) limestones and dolostones along the Eisriesenwelt trail on the Tennengebirge (Salzburg, Austria) reveal a progression from fore-reef to lagoonal environments, including a small Norian reef with both Carnian and Norian characteristics. Here, we provide high-resolution biostratigraphic age constraints of the Tennengebirge platform carbonates and describe an early Norian patch reef that is built by large Retiophyllia corals and encrusted by ''Tubiphytes,'' sponges, and microbial fabrics. The tall (up to 4 m), narrow phaceloid Retiophyllia coral colonies exhibit phototropic growth patterns—coral branches that are at the top of the colony grew longer than those on the side of the colony— thus, we suggest that these corals had a symbiotic association with photoautotrophs (most likely zooxanthellae). The well-constrained ammonoid and conodont biostratigraphy presented here establish that the Tennengebirge patch reef was deposited in the early Norian, nevertheless, it contains features typically associated with Carnian reefs (small, encrusting sponges, Carnian-style microbial crusts, and ''Tubiphytes''). The Carnian traits of the Norian reef emphasize the importance of accurate biostratigraphic dating; obtaining independent age estimates for reef outcrops is crucial to correctly determine the timing and magnitude of transitions in Triassic reef ecology. INTRODUCTION

Rhaetian foraminiferal assemblage from the Dachstein Limestone of Mt. Begunjščica (Košuta Unit, eastern Southern Alps)

Article

Full-text available

Jun 2012

Luka Gale

Mt. Begunjščica (Karavanke Mts., northern Slovenia) structurally belongs to the Košuta Unit (eastern Southern Alps). The Dachstein Limestone, building the northern side of the mountain and its main ridge, was deposited on the Julian Carbonate Platform, while grey and red nodular Jurassic limestones of the southern slope represent sedimentation on the Julian High. The massive Dachstein Limestone contains a rich assemblage of benthic foraminifera. Typical representatives of the reef and back-reef area were recognized. The age of the assemblage is dated as Rhaetian, based on the co-presence of species with a Norian and Rhaetian time span, such as Galeanella tollmanni, "Sigmoilina" schaeferae, Alpinophragmium perforatum, Aulotortus tumidus, Variostoma catilliforme, Variostoma cochlea and Variostoma helicta, together with the Rhaetian to Lower Jurassic Involutina turgida.

Kaeveria fluegeli (Zaninetti, Altiner, Dager et Ducret, 1982) (Foraminifera) from Upper Triassic of the South-East Pamirs. Korchagin O.A.

Article

Full-text available

Feb 2009

O. A. Korchagin

Foraminifers representing species Kaeveria fluegeli have been found in the Zorkaradjilga Formation (Sagenites quinquepunctatus Zone) of the upper Norian (or lower Rhaetian) in the central structural-facies zone of the South-East Pamirs. Their occurrence here is an additional criterion substantiating age and correlation of host deposits and an evidence in favor of fauna migration from the southern Tethys during the respective time span not only in northwestern areas of that ocean (Northern Calcareous Alps), but also in its central part (the South-East Pamirs).

Upper Triassic reef-limestone blocks of southwestern Japan: New data from a Panthalassan seamount

Article

Jul 2010
PALAEOGEOGR PALAEOCL

Sedimentology and biostratigraphy of upper Triassic atoll-type carbonates from the Dalnegorsk area, Taukha terrane, far East Russia

Article

Nov 2019
GLOBAL PLANET CHANGE

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.

Biotic composition and microfacies distribution of Upper Triassic build-ups: new insights from the Lower Carnian limestone of Lesno Brdo, central Slovenia

Article

Jul 2018

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.

The start-up of the Dolomia Principale/Hauptdolomit carbonate platform (Upper Triassic) in the eastern Southern Alps

Article

Sep 2017
SEDIMENTOLOGY

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.

Paleogeographic trends in Late Triassic reef ecology from northeastern Panthalassa

Article

Dec 2014
EARTH-SCI REV

The Late Triassic was a pivotal period in reef evolution, but the majority of information about reef ecology during this time comes from buildups in the Alps (e.g., the Tethys Ocean). Recent studies of reefs in western North America have recognized unique ecologies along the eastern margin of the Panthalassa Ocean. Although there are numerous (twenty-five) localities with putative reef builders, only four buildups had syndepositional relief and a rigid framework (i.e. true reefs). The most paleo-northern true reefs were microbial patch reefs with only a few large skeletal bioconstructors; hypercalcified sponges and spongiomorphs built the mid-latitude reefs, with secondary microbial encrustation and branching, phaceloid Retiophyllia corals. Corals are the primary bioconstructors in Panthalassa’s most paleo-equatorial reefs and calcareous microbes are sparse. When all reefal deposits are analyzed, the N-S gradient is also present, with microbial and bivalve deposits in the north, sponge-coral deposits in the mid latitudes, and coral deposits near the equator. This ecological gradient is not apparent in the Tethys Ocean. Tethyan reefs thrived in oligotrophic, tropical waters without strong latitudinal gradients; by contrast, paleoceanographic considerations suggest that cool, nutrient-rich waters swept south along the western North American borderlands in the Late Triassic. The eastern boundary current is interpreted to have created a strong north-south differentiation of environments in northeastern (NE) Panthalassa that was manifested in both the biotic and abiotic characteristics of eastern Panthalassic reefs. Reefs from equatorial Panthalassa are similar to Tethyan reefs (warm-water, photozoan, coral reef structures), whereas higher paleo-latitude reefs from Panthalassa are interpreted as cool-water (heterozoan) buildups, with abundant calcareous microbes, diminutive biocalcifiers, and few large, framework-building corals.

Microbialite fabrics and diminutive skeletal bioconstructors in lower norian summit point Reefs, Oregon, United States

Article

Jul 2012

Microfacies analysis of five patch reefs from the Martin Bridge Formation (Upper Triassic/Norian, Summit Point, Oregon, United States) reveals that microbialite fabrics dominate reef construction versus corals or other large metazoans. Other reef bioconstructors include characteristic Late Triassic branching corals and diminutive calcifiers (solenoporacean red algae, foraminifera, and sponges). The patch reefs exhibit dense growth fabrics and had elevation above the seafloor, making them ecological reefs or true reefs. Robust binding and encrusting organisms inhabited higher-energy areas, whereas red algae, followed by phaceloid coral colonies, inhabited zones of decreasing water energy, defining a subtle zonation consistent with wave energy in the paleoenvironment. The dominance of microbial fabrics and diminutive bioconstructors make the Summit Point reefs distinct among Upper Triassic reefs from northeastern Panthalassa. Summit Point was originally identified as a Dachstein-type reef (e.g., high diversity, dominated by corals and sponges, massive bedding, large reef cavities). However, the dominance of microbial fabrics over larger metazoans, the (comparatively) modest faunal diversity, and lack of abundant, multigenerational epibionts or cements clearly differentiates the Summit Point reefs from the Dachstein reefs of northern Europe. The Summit Point reefs do, however, bear a striking resemblance to some Middle Triassic (Anisian) reefs from the Tethys, particularly with the abundance of microbialite fabrics and diminutive, binding or encrusting bioconstructors.

Bioerosion and encrustation in Late Triassic reef corals from Iran

Preprint

Full-text available

May 2024

Hard substrate communities can impact coral reef growth by adding or removing calcium carbonate when they act as encrusters or bioeroders, respectively. Although such sclerobiont communities are known across the Phanerozoic, the Triassic saw a substantial increase in reef macrobioerosion. This study provides the first quantitative assessment of sclerobionts in a Late Triassic (Norian) reef coral community from the Nayband Formation in central Iran and establishes some post-Paleozoic trends in reef bioerosion. Sclerobionts were common on the dominant coral Pamiroseris rectilamellosa and covered between 0 and 26.4% of total coral surface area among the 145 colonies investigated. Encrustation was significantly more prevalent (1.78% of total area) than bioerosion (0.36% of total area). The underside of corals was 3.5 times more affected by sclerobionts than the surfaces. This suggests that the sclerobionts preferentially colonized dead parts of corals. The main encrusting taxa were polychaeta worms (76.2%), followed by bivalves (11.9%). The main bioeroders were of Polychaeta (51.4%), Porifera (22.2%), and Bivalvia (20.7%). The lack of a correlation between encrustation and bioerosion intensity suggests that the amount of sclerobionts is not simply a function of exposure time before final burial. Our review of the published literature suggests a declining trend in the relative importance of bivalves, polychaetas and cirripeds in reefs, whereas sponges increased in importance from the Triassic until today.

End-Triassic crisis and “unreefing” led to the demise of the Dachstein carbonate platform: A revised model and evidence from the Transdanubian Range, Hungary

Article

Full-text available

Jan 2021
GLOBAL PLANET CHANGE

The Dachstein platform was an extensive carbonate platform developed on the westernmost shelf of the Neotethys during the Late Triassic, now preserved in various tectonic units disrupted during the Alpine orogeny. Despite being the focus of a multitude of sedimentological, paleontological and other studies, the demise of this platform remains controversial, with contrasting views on the timing and causes of cessation of its growth, the duration of the gap above, which at many places includes the Triassic-Jurassic boundary (TJB), and the depositional environment of overlying strata. Here we present new carbonate sedimentological, stable isotope and cyclostratigraphic data from sections in the Transdanubian Range (Hungary) which capture the termination of uppermost Triassic Dachstein Limestone and the onset of Hettangian (Early Jurassic) sedimentation following a hiatus. Previously, the TJB in the Transdanubian Range was regarded as a textbook case of a tectonically-driven platform drowning event or, alternatively, cessation of carbonate production due to emergence caused by a significant sea level fall at the TJB. However, recognition of global biotic change and environmental perturbations at the TJB calls for an assessment of their possible role in the demise of the Dachstein platform. Oxygen and carbon isotopic composition of bulk carbonates were measured in sections at Kőris-hegy (Bakony Mts.), Tata (Tata Horst), and Vöröshíd (Gerecse Mts.) Paleogeographically, these three sections represent a proximal to distal platform transect. Other sections at Pisznice and Tölgyhát (Gerecse Mts.) yielded additional sedimentological data. The sharp surface separating the Dachstein Limestone from the overlying Jurassic formations carries no or only minimal relief at outcrop scale. Thin section studies reveal small-scale irregularities, stylolites, microborings with ferruginous filling, or a thin clay-rich layer at the TJB, indicative of a submarine, or perhaps polygenetic, hardground. In the first meters of the lowermost Jurassic beds abundant ooids occur, and crinoids become common. In each of the studied sections, an abrupt negative carbon isotope shift is recorded at the TJB, and a gradual rebound to more positive values characterizes the lowermost Jurassic strata. Chemostratigraphy allows correlation with sections elsewhere. In the Transdanubian Range, the initial carbon isotope excursion and at least the first part of the purported main carbon isotope excursion are not preserved due to the gap at the TJB. Combined bio- and cyclostratigraphy of lowermost Jurassic strata permits an astrochronologic duration estimate of the early Hettangian hiatus that was not longer than a few hundreds of thousand years. Our results highlight the role of submarine erosion, perhaps partly related to acidification, and point to an abrupt change in carbonate production related to the end-Triassic extinction of several groups in the platform system. “Unreefing”, the ecological collapse of reefs, led to a regime shift, the transformation of the rimmed platform to a carbonate ramp, with a significant gap in production and preservation of carbonate sediment. This model is not uniformly applicable to Late Triassic platforms as several of them, unlike the Dachstein platform, survived with unrimmed architecture in the Early Jurassic elsewhere on the Neotethyan shelf. However, the model may explain features of the carbonate platform sedimentary record across other events with reef collapse.

Sedimentology, biostratigraphy and diagenesis of Upper Triassic shallow–water carbonates from Japan and Russian Far East: New investigations on the Panthalassa Ocean

Thesis

Full-text available

Jul 2020

Giovan Peyrotty

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.

Upper Triassic calcareous algae from the Panthalassa Ocean

Article

Jul 2020

Upper Triassic calcareous algae, abundant and well-diversified in Tethyan deposits, have rarely been described in rocks of Panthalassan origin. Over the past ten years, several studies were performed on Upper Triassic carbonate deposits of Panthalassan affinity in North America, Japan and Far East Russia, revealing unexpectedly rich and diversified assemblages. The samples were collected from nine localities situated on both sides of the Pacific Oce- an. The identified algal assemblage consists of green and red algae, including fourteen dasycladaleans, rare bryopsida- leans, and several rhodophyceans. This paper describes the main algal taxa, including six new species: Holosporella? ros- sanae Bucur & Del Piero n. sp., Holosporella magna Bucur & Fucelli n. sp., Griphoporella minuta Bucur & Peybernes n. sp., Patruliuspora pacifica Bucur, Del Piero & Peyrotty n. sp., Patruliuspora oregonica Bucur & Rigaud n. sp. and Collarecodium? nezpercae Bucur & Rigaud n. sp. Rivulariacean-like cyanobacteria and thaumatoporellacean algae are also present. The whole Panthalassan algal assemblage comprises both unknown (?endemic) and common taxa of the Tethyan domain. To explain the cosmopolitan distribution of various Upper Triassic benthic organisms (scleractinian corals, calcified sponges, foraminifera), a close connection with the Tethys Ocean was hypothesized by different authors. During the Late Triassic, the Tethys was open to the east on the Western Panthalassa but not to the west, suggesting that Triassic calcareous algae were able to efficiently colonize environments that are estimated to be more than 10’000 km apart. An adventitious transport of calcareous algae and/or their spores is proposed to explain this long-range algal dispersal.

Upper Triassic calcareous algae from the Panthalassa Ocean

Article

Full-text available

Jul 2020

δ18O, δ13C, trace elements and REE in situ measurements coupled with U–Pb ages to reconstruct the diagenesis of upper triassic atoll-type carbonates from the Panthalassa Ocean

Article

Full-text available

Jun 2020
MAR PETROL GEOL

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.

Upper Triassic (Carnian) sponge reef mounds from South Canyon, central Nevada

Article

Full-text available

Jul 2020

An important interval for reef evolution occurs in the Triassic Period. However, Late Triassic reefs along the edge of the Panthalassa Ocean receive much less attention than their Tethys region counterpart. To improve our understanding of reef evolution along the Panthalassa, we present a quantitative microfacies analysis to characterize reef facies types from a central Nevada locality. We point counted thin sections to quantitatively assess the relative abundance of reef and interstitial components from six Carnian reef mounds. Reef mound formation occurs at three different stratigraphic intervals. Each interval records a different reef mound size and shape. The oldest stratigraphic interval consists of four separate reef mounds; each mound is approximately 3–12 m wide and 2–4 m high. The second youngest stratigraphic interval consists of one large ~ 10-m wide and 15.5-m high domal reef mound. The third, and youngest, reef mound is smaller in comparison (i.e., 1-m wide and 1.5-m high). We recognize two reef facies types within these reef mounds. Different calcareous sponges, bound together by microproblematica and clotted micrite, form the overall reef framework. We suspect that changes in relative sea level affect the initial colonization, different growth capacities, and overall preservation of the South Canyon reef mounds. When South Canyon reefs are compared to other Panthalassa reefs, it seems that “Wetterstein-type” reef–sponge bindstone facies containing biogenic crusts dominate and corals are less abundant and persist generally in both shallow and deeper water environments. However, significant differences in primary and secondary framebuilder abundances exist due to differences in where the reefs grew in relation to fair-weather wave base (FWWB). Thus, changes in relative sea level may affect the initial colonization, different growth capacities, and overall preservation of reef but water depth may also control the primary and secondary reef builders. Consequently, quantitative assessment of reef ecosystems within a sequence stratigraphic framework undoubtedly facilitates fewer problematic comparisons between reefs but it also enhances our understanding of reef development.

Sedimentology and carbon isotope stratigraphy of the Rhaetian Hochalm section (Late Triassic, Austria)

Article

May 2020
GLOBAL PLANET CHANGE

The Rhaetian (201–209 Ma, the latest stage of the Triassic) is an important time-interval for the study of environmental changes preceding the End-Triassic Mass extinction. A detailed sedimentological and chemostratigraphic study was conducted in the lower Kössen Formation at Hochalm (Austria), the type-section of the Hochalm Member (Mb). This section exposes mid-Rhaetian sediments deposited in an intraplatform shallow marine basin on the north-western margin of the Tethys. The study highlights eight apparent shallowing-upward sequences from the middle of Unit 2 to Unit 4 of the Hochalm Mb stacked within the long-term transgression that characterizes the Kössen Formation. Both the bulk carbonate and the bulk organic matter δ¹³C records indicate the presence of a distinct increase in carbon isotope values in the lower part of the lower Hochalm Mb. This excursion might represent a new chemostratigraphic marker that could be used for refining the Rhaetian stratigraphy and represents another important Late Triassic carbon-cycle perturbation prior to the major disturbance associated with the End Triassic biotic crisis.

Development of an equatorial carbonate platform across the Triassic-Jurassic boundary and links to global palaeoenvironmental changes (Musandam Peninsula, UAE/Oman)

Article

Full-text available

Dec 2016
GONDWANA RES

The Triassic-Jurassic boundary is marked by one of the ‘big five’ mass extinctions of the Phanerozoic. This boundary event was accompanied by several carbon cycle perturbations, potentially induced by the opening of the Central Atlantic and associated volcanism, and accompanied by an ocean acidification event. Continuous carbonate successions covering this interval of environmental change are however rare. Here data from a shallow-marine equatorial mixed carbonate-siliciclastic succession is presented, that was studied on a regional scale. Four sections that are 48 km apart were examined on the Musandam Peninsula (United Arab Emirates and Sultanate of Oman). The system was analysed for its sedimentology, vertical and lateral facies changes, and stable carbon and oxygen isotopes. Strontium isotope analysis was used to determine the position of the Triassic-Jurassic boundary horizon. The studied ramp experienced an episode of demise during the Late Triassic, followed by a restricted microbialite dominated ramp, containing large amounts of siliciclastic facies. During the Latest Triassic the diverse carbonate factory revived and flourished across the Triassic-Jurassic boundary. No clear evidence for a biocalcification crisis or an ocean acidification event across the Triassic-Jurassic boundary is visible. Lateral facies heterogeneities can be observed across the studied interval, attributed to hydrodynamic activity, including tropical storms, crossing the extensive shelf area. Although evidence for synsedimentary tectonic activity is present, the vertical stacking pattern is largely controlled by changes in relative sea level. The refined chronostratigraphy accompanied by the detailed environment of deposition analysis allows for a refinement of the regional palaeogeography. The neritic equatorial carbonate ramp has archived a negative carbon isotope excursion preceding the Triassic-Jurassic boundary that has also been reported from other study sites. The lack of evidence for a biocalcification crisis across the equatorial Triassic-Jurassic boundary indicates that the Tethys did not experience a distinct global acidification event.

Global, regional and local controls on the development of a Triassic carbonate ramp system, Western Balkanides, Bulgaria

Article

Full-text available

Oct 2016
GEOL MAG

Athanas Chatalov

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.

Reefs Through Time: An Evolutionary View

Chapter

Full-text available

Jul 2016

Although reef-like structures formed in the Neoproterozoic, reefs built by metazoans did not appear until the early Paleozoic. From then until the Recent, reefs diversified, underwent extinctions many times and then diversified again. Reef-inhabiting organisms included many different groups from algae to vertebrates as well as enigmatic, extinct suprageneric taxa. Evolution of these groups continued unabated and sometimes resulted in significant changes in the communities making up reefs. These reef groups varied over geologic time with extinction events commonly marking dramatic changes in the biotas. Paleozoic reefs consisted of sponges, corals, foraminifera, algae, bryozoans, and brachiopods, among others. The major extinction event at the end of the Paleozoic eliminated these forms as reef constituents and new groups (e.g., the first scleractinian corals) appeared in the Triassic. The Mesozoic was dominated by sponges, corals, rudist bivalves, and algae, most of which were eliminated in the end-Cretaceous extinction event. The Cenozoic reef biotas included red algae, foraminifera, sponges, corals, various invertebrates, and fish.

Palaeoecology of new fossil associations from the Cipit boulders, St. Cassian Formation (Ladinian–Carnian, Middle–Upper Triassic; Dolomites, NE Italy)

Article

Full-text available

Mar 2016

Six fossil associations from 59 thin sections obtained out of 23 Cipit boulders of the Middle-Late Triassic St. Cassian Formation are described. Grouping and obtainment of these associations were performed considering all biomorpha and microbialites contained in the thin sections by means of cluster analysis in Q-mode using three algorithms and two indices. Further microfacial categories observed in the thin sections were allochthonous components, cements and microsparite, although they do not represent a significant fraction in any case. The associations include the following: Dendronella–Hexactinellida Association, Cassianothalamia Association I, Cassianothalamia Association II, Patch Reef Association I (Balatonia-microencruster Association), Patch Reef Association II (Solenopora–Dendronella Association) and Patch Reef Association III (Spongiomorpha ramosa Association). The possible palaeoenvironmental settings, from which each association is derived, are discussed individually. These settings were elucidated based on each fossil contained in the associations, since many of them are diagnostic for establishing specific environmental criteria. Although most associations are described here for the first time, some of them may be related to the “Cassian Patch Reefs”, while one of them (“Cassianothalamia-Gemeinschaft”) is reviewed.

Stromatolitic biotic systems in the mid-Triassic of Israel - A product of stress on an epicontinental margin

Article

Sep 2015
PALAEOGEOGR PALAEOCL

Paleogeographic significance of Upper Triassic basinal succession of the Tamar Valley, northern Julian Alps (Slovenia)

Article

Full-text available

Aug 2015

The Julian Alps (western Slovenia) structurally belong to the eastern Southern Alps. The Upper Triassic succession mostly consists of shallow water platform carbonates of the Dolomia Principale-Dachstein Limestone sys- tem and a deep water succession of the Slovenian Basin outcropping in the southern foothills of the Julian Alps. In addition to the Slovenian Basin, a few other intraplatform basins were present, but they remain poorly researched and virtually ignored in the existing paleogeographic reconstructions of the eastern Southern Alps. Herein, we describe a deepening-upward succession from the Tamar Valley (north-western Slovenia), belonging to the Upper Triassic Tarvisio Basin. The lower, Julian-Tuvalian part of the section comprises peritidal to shallow subtidal carbonates (Conzen Dolo- mite and Portella Dolomite), and an intermediate carbonate-siliciclastic unit, reflecting increased terrigenous input and storm-influenced deposition (Julian-lowermost Tuvalian shallow-water marlstone and marly limestone of the Tor For- mation). Above the drowning unconformity at the top of the Portella Dolomite, Tuvalian well-bedded dolomite with claystone intercalations follows (Carnitza Formation). The latter gradually passes into the uppermost Tuvalian—lower- most Rhaetian bedded dolomite with chert and slump breccias, deposited on a slope and/or at the toe-of-slope (Bača Dolomite). Finally, basinal thin-bedded bituminous limestone and marlstone of Rhaetian age follow (Frauenkogel For- mation). The upper part of the Frauenkogel Formation contains meter-scale platform-derived limestone blocks, which are signs of platform progradation. The Tarvisio Basin may have extended as far as the present Santo Stefano di Cadore area, representing a notable paleogeographic unit at the western Neotethys margin.

A Triassic homoclinal ramp from the Western Tethyan realm, Western Balkanides, Bulgaria: Integrated insight with special emphasis on the Anisian outer to inner ramp facies transition

Article

Sep 2013
PALAEOGEOGR PALAEOCL

Athanas Chatalov

Norian To Rhaetian Scleractinian Corals In the Ferdows Patch Reef (Nayband Formation, East Central Iran)

Article

Full-text available

Sep 2012

The Nayband Formation is one of the best known sedimentary units in central Iran. The type section consists of a thick succession of shale, siltstone, reef limestone and sandstone that is subdivided into five distinct members: Gelkan, Bidestan, Hoz-e-Sheykh, Howz-e- Khan and Qadir. Abundant and well-preserved framework-building scleractinian corals are included among the macrofossils of the Nayband Formation; these corals characterize the formation and are the subject of this study. The Hassan-Abad section, located in northeast Iran in Lute Block (northwest of Ferdows city), was chosen for detailed study and sampling. Analysis of sedimentary lithofacies and faunal assemblages in the Bidestan and the Howz-e-khan members indicate both biostromal and biohermal characters for the former shallow-water patch reefs and support a Norian to Rhaetian age. The useful biostratigraphic hydrozoan Heterastridium conglobatum was studied along with 14 taxa of scleractinian corals: Stylophyllopsis rudis, Distichophyllia norica, Paradistichophyllum dichotomum, Retiophyllia frechi, Retiophyllia norica, Retiophyllia robusta, Chondrocoenia schafhaeutli, Chondrocoenia ohmanni, Astraeomorpha crassisepta, Astraeomorpha confusa, Astraeomorpha minor, Procyclolites triadicus, Pamiroseris rectilamellosa, and Eocomoseris ramosa. These fossils clarify the stratigraphy of the Nayband Formation, as well as provide new information on the patch reefs and the framework constructors of these reefs.

Biogeochemical and redox record of mid-late Triassic reef evolution in the Italian Dolomites

Article

Apr 2014
PALAEOGEOGR PALAEOCL

Depth transect of an Upper Triassic (Rhaetian) reef from Gosau, Austria: Microfacies and community ecology

Article

Apr 2013
PALAEOGEOGR PALAEOCL

In the Late Triassic (~ 235–201.3 Ma) scleractinian corals and hypercalcified sponges built large, diverse reef ecosystems, the most famous of which are the Dachstein reefs. This study presents a depth transect along an Upper Triassic (lower Rhaetian) Dachstein reef from the Gosausee margin of the Dachsteingebirge (Gosau, Austria). The Gosausee microbial-sponge-coral reef is a complete barrier reef with an almost continuous fore reef to lagoon transect preserved (a very rare occurrence for the Triassic), and thus provides a window into depth zonation of Dachstein-type reef facies and biotic succession. The Gosausee reef facies exhibit strong depth control and five classic reef facies or zones are identified: the fore reef, reef front, reef crest, back reef, and lagoon facies. Thin, rare microbial fabrics and a high abundance of fine-grained, mud-rich skeletal wackestones (transported reef debris) characterize the deepest fore reef. As the reef shallows, muddy sediments decrease in abundance and are replaced by microbial fabrics, corals, and cements. Abundant sponges, microbial crusts, and thick, marine cements typify the reef crest, whereas microbialite-coated phaceloid corals are dominant in the back reef facies. Heavily cemented oncoids or microbial-sponge bindstones are characteristic of the lagoon. Based on their compositional and biotic similarities, the Gosausee reef was likely part of the same barrier reef systems as the source reef for the Gosaukamm reef breccia (one of the classic Norian–Rhaetian Dachstein reefs). The reef zones of the Gosausee margin can be used to interpret the depth or reef zone of less well preserved reef fragments, can inform models of community ecology and niche utilization in the Late Triassic, and highlight the need for additional research into the environmental factors that controlled biotic distribution in Upper Triassic reefs.

Platy coral patch reefs from eastern Panthalassa (Nevada, USA): Unique reef construction in the Late Triassic

Article

Jan 2011
PALAEOGEOGR PALAEOCL

Upper Triassic (Lower Norian) reefal buildups near Mina, Nevada, represent some of the earliest scleractinian coral reefs from eastern Panthalassa. The small patch reefs (~20–40m high and ~50–150m wide, obvious meter-scale elevation above the surrounding sediments) are from the Luning Allochthon and grew on an inner to middle ramp or in a deep lagoon. The Mina patch reefs were constructed by several different coral ecomorphotypes (platy, tabular, domal/massive, and branching corals) interpreted to have had zooxanthellate symbionts, and record subtle coral zonation within the reefs. Based on modern coral ecomorphotypes, platy to tabular corals at Mina grew in the lower euphotic zone (stressed by low light conditions), and the massive or domal corals inhabited shallower water (possibly above fair weather wave base) and were stressed by wave energy.Unlike most other Upper Triassic reef ecosystems where phaceloid branching corals or calcareous sponges constitute the principal bioconstructors, the platy to tabular corals were the primary builders in the Mina patch reefs. The Mina reefs are also unique because cryptic and cavernous internal environments, epibionts, cryptobionts, and thick microbial crusts are rare or absent. The combination of platy coral dominance with the lack of epibionts/cryptobionts/microbial crusts suggests that the Norian reefs from Mina, Nevada represent a unique form of scleractinian reef construction from the Late Triassic.

Causal or casual link between the rise of nannoplankton calcification and a tectonically-driven massive decrease in Late Triassic atmospheric CO 2 ?

Article

Mar 2008
EARTH PLANET SC LETT

On the basis of a global carbon-climate numerical model, we reconstructed atmospheric carbon dioxide concentrations over the first 60 million years of the Mesozoic. Our analysis indicates that pCO 2 declined from more than 3000 ppmv to less than 1000 ppmv, with a drastic drop during the Late Triassic. The fast northward drift of Pangea exposed a large continental surface to warm and humid equatorial climate, thus promoting CO 2 consumption through weathering. This massive drawdown of atmospheric CO 2 is consistent with sedimentological and geochemical data of the rock record and correlates with the primary radiation of calcareous nannoplankton, a biological revolution shifting the global carbonate sink from shallow water environments to the open oceans. Our numerical model shows that at time, tectonics, via weathering, increased the pH of the oceanic surface waters by 0.3 units, corresponding to a 50% decrease in H + concentration. This may have provided the ultimate environmental trigger which unlocked the newly oxidized Mesozoic open oceans to pelagic nannobiocalcification.

Aulotortus friedli from the Upper Triassic Gravitational Flow Deposits of the Kumagawa River (Kyushu, Southwest Japan)

Article

Full-text available

Jul 2010

The benthic foraminifer Aulotortus friedli is reported from the Upper Triassic carbonates (capped seamount) of the Sambosan Accretionary Complex in Kyushu, Southwest Japan. Specimens were collected from shallow-water limestone clasts in a debris flow sequence near the Ose locality along the Kumagawa River. The limestone clasts mainly represent shoal facies where the benthic foraminifer is extremely abundant. Because of the remarkable preservation of the Japanese specimens, they allow further description of the involutinid A. friedli. In addition, a detailed sedimentary and environmental analysis of the gravitational deposits where A. friedli occurs is given. Using microfacies analysis together with the biostratigraphic range of A. friedli and associated foraminifers, a new interpretation is proposed of a seamount collapse process that occurred during the Norian-Rhaetian and preceded the major collapse event of the Sambosan seamount, which has been placed in the Middle to Late Jurassic.

Extinction, survival and recovery of corals from the Triassic to Middle Jurassic time

Article

Jan 2009
TERRA NOVA

Recognizing extinction events and determining their cause at the Triassic/Jurassic (T/J) transition and near the Pliensbachian–Toarcian (Lower Jurassic) boundary is a field of growing interest. We provide arguments for these events through a literature based new evaluation of coral diversity from Triassic to Dogger and a new palaeobiogeographical map. The T/J extinction of corals is clearly related to the breakdown of reef environments. Origination curves show that Hettangian (the lowest Jurassic stage) was not only a survival phase but already rather a recovery phase. Post-extinction evolution of reefs and their survival only in the northernmost margin of the Tethys support the hothouse hypothesis for the T/J extinction event. During Pliensbachian, many new taxa appear, but mostly solitary corals, not really framebuilders. Many of these taxa do not occur anymore during the following stages. The new increase in diversity is related to the development of Bajocian (Middle Jurassic) reefs.

Facies architecture of an isolated carbonate platform in the Hawasina Basin: The Late Triassic Jebel Kawr of Oman

Article

Aug 2007
PALAEOGEOGR PALAEOCL

Michaela Bernecker

In the oceanic realm of the southern Tethys, carbonate production of isolated platforms ceased after the end-Permian mass extinction and did not recover until the Late Triassic.The Misfah Formation (MF) at Jebel Kawr in the Oman Mountains is interpreted as a relic of such an isolated Late Triassic platform of the Hawasina Ocean, a part of the Neo-Tethys. Correlation of three sections at Jebel Kawr points to a sequence architecture with four third-order sequences (MF1–MF4). The maximum flooding surface (mfs) of MF3 can be correlated to the attached Arabian platform.The shallow-water carbonates of Jebel Kawr comprise a platform rim reef facies and bedded inner-platform facies characterized by stacked high-frequency cycles with subtidal to intertidal carbonate sequences.The depositional profile of this Late Triassic isolated platform evolved during Carnian and Norian time from a low-relief carbonate bank to a high-relief platform rimmed by reefs. The onset of the carbonate sedimentation is characterized by an initial phase with volcaniclastic interruptions, followed by a carbonate bank stage with a shallow subtidal to peritidal interior and marginal oolite shoals. In the Norian vertical accumulation caused an increase of the platform height and developed a relief along the margins that progressively increased through the aggrading reef stage. The possibility that a reef rim existed and was later removed by erosion is suggested by the Sint reef and olistoliths of similar reef limestones in the surrounding areas.

Microfacies and depositional setting of the Upper Triassic mid-oceanic atoll-type carbonates of the Sambosan Accretionary Complex (southern Kyushu, Japan)

Article

Full-text available

Apr 2010

The Upper Triassic shallow-water limestones of the Sambosan Accretionary Complex are reconstructed as a remnant of a mid-oceanic atoll-type build-up upon a seamount in the Panthalassan Ocean. The Sambosan atoll-type carbonates and its pedestal were accreted along with deep-water ribbon-chert and related siliceous rocks to the eastern margin of Asia during the Late Jurassic to Early Cretaceous. Studied limestones crop out in southern Kyushu Island, southwest Japan. Although the prevailing and intense deformation during the accretionary process prevents measurement of sections in stratigraphic successions, and sedimentary structures are poorly preserved, microfacies description and foraminifers analysis allow us to speculate the depositional setting of the Sambosan limestones. Seventeen microfacies are distinguished and several foraminifers of Tethyan affinity are identified. Foraminifers indicate a Late Carnian to Rhaetian age. The Tethyan affinity of the macro- and microfaunas suggests that the Sambosan seamount was located presumably in a low- to middle-latitudinal zone of the southern hemisphere during the Late Triassic.

Patterns of extinction and recovery across the Triassic–Jurassic Boundary interval in three resilient Southern Tethyan carbonate platforms

Article

Full-text available

Jun 2024
PALAEOGEOGR PALAEOCL

Schnecken und Muscheln im Korallenriff - Neues aus obertriassischen Riffkalken von Österreich (Nördliche Kalkalpen).

Article

Full-text available

May 2023

Tropische Riffe gehören zu den vielfältigsten Ökosystemen der Erde. Die größte Diversität bzw. Artenzahl steckt allerdings weniger in den riffbildenden Organismen (z. B. Korallen, Schwämme) als in den riffbewohnenden Tieren und Pflanzen. Viele fossile Riffe hohen geologischen Alters sind massiv versteinert (lithifiziert) und ihre Ablagerungen stark verändert (Diagenese), was u. a. Lösungsprozesse und Mineralneu- bildungen (Kalzitisierung und/oder Dolomitisierung) beinhaltet. Aus diesem Grund sind riffbewohnende Organismen selten gut erhalten. Sie fehlen häufig in der Dokumentation bzw. ihnen wird in wissenschaftlichen Studien keine besondere Bedeutung beigemessen. Die Anwesenheit von Riffbewohnern in der Gesamtfauna findet dann nur kursorisch Erwähnung, die entsprechenden Arten werden in offener Nomenklatur, d. h. ohne genaue Artbestimmung, gelistet. Meistens werden solche riffbewohnenden Arten auch nicht abgebildet. Eine neue Studie, erarbeitet von Wissenschaftlern der Bayerischen Staatssammlung für Paläontologie und Geologie München (NÜTZEL, NOSE), der Mineralogischen Staatssamm- lung München (HOCHLEITNER) und dem Paläontologischen Institut und Museum der Universität Zürich (HAUTMANN), befasst sich mit fossilreichen obertriassischen Riffkalken des Rötelwand-Riffs, südöstlich Salzburg (Oberrhät-Riffkalk) und des Gosaukamms (Dachsteinkalk). Die mächtigen Kalke bauen dort, wie auch andernorts in den Nordalpen, wesentliche Teile des Gebirges auf. Neben den sedimentologischen Aspekten zielt die Arbeit vor allem auf die Dokumentation der Riff-Fauna und hier insbesondere auf die riffbewohnenden Mollusken. Schnecken (Gastropoden) sind besonders häufig, mit z. T. auffällig großen Arten (z. B. Purporoidea moosleitneri NÜTZEL et al., 2022). Die Molluskenfauna ist Teil einer grobkörnigen Riffschutt-Fazies assoziiert mit kleinen Fleckenriffen, die im Falle des Rötelwand-Riffs fast ausschließlich aus grobästigen Steinkorallen (Cycli- phyllia cyclica) aufgebaut sind. Gastropoden und Bivalven aus dem Oberrhät-Riffkalk finden sich in verschiedenen Museen und Privatsammlungen, wurden aber bislang noch nicht eingehend untersucht, mit Ausnahme der Arbeiten von ZAPFE (1963, 1967). Ein weiteres Ziel dieser Studie ist die Bewertung des evolutiven Schicksals der riffbewohnenden Mollusken über das große Massenaussterben an der Trias-Jura-Grenze hinweg. Die hier vorgestellten Ergebnisse stellen eine deutschsprachige Zusammenfassung der in NÜTZEL et al. (2022) ausführlich publizierten Daten dar.

Latest Triassic (Sevatian–Rhaetian) reef carbonates from the Northern Calcareous Alps (Austria), their mollusc dwellers, and their fate at the end-Triassic extinction event

Article

Full-text available

Dec 2022

A reef-associated mollusc fauna (gastropods and bivalves) and its facies context are described from latest Triassic (Sevatian–Rhaetian) reef carbonates of Austria (Rötelwand reef at Gaissau and Gosaukamm near Hallstatt). The studied carbonates from the Rötelwand reef consist of mollusc-rich rudstones, partly boundstones, which contain branched corals ( Cycliphyllia and Retiophylia, Pinacophyllum ), whereas coralline sponges are absent. The rich foraminiferid fauna that is associated with the reef builders consists of 11 genera; eight of these genera became extinct until the end of the Rhaetian. Associated with small patch reefs was a rich mollusc fauna with 19 gastropod species and 8 epifaunal bivalve species. The gastropod fauna is dominated by Microschiza rhaetica , Trochotoma praecursor , and the large growing Purpuroidea moosleitneri . Six gastropod species are new to science: Angulomphalus senowbarii sp. nov., Stuorella zapfei sp. nov., Hologyra callosa sp. nov., Microschiza rhaetica sp. nov., Angularia corallina sp. nov., and Purpuroidea moosleitneri sp. nov. Four Triassic gastropod species are placed in other genera (new combinations): Tylotrochus diversicostatus Wolff, 1967 and Eucycloscala epitoniformis Nützel and Senowbari-Daryan, 1999 are placed in Sadkia, Praelittorina sepkoskii Nützel and Erwin, 2004 in Microschiza , and Purpuroidea ? minioi Leonardi, 1935 in Angularia Koken, 1892. Reversal of precedence is proposed for Angularia Koken, 1892 (Gastropoda) and Angularia Busk, 1881 (Bryozoa) under ICZN Art. 23.9. Although reefs suffered a catastrophic decline at the end of the Triassic, most of the studied reef-associated bivalve and gastropod genera survived into the Jurassic, indicating a considerable ecological plasticity of these groups. Only 12 out of 47 reef-associated mollusc genera became extinct (25.5%). This observation is at variance with earlier suggestions that taxa that were associated with reefs and carbonate substrata had a significantly higher extinction risk than level-bottom dwellers. However, extinction at the species level appears more severe; only three bivalve species but no gastropod species recorded in this fauna have records from the Jurassic.

Photosymbiosis in Late Triassic scleractinian corals from the Italian Dolomites

Article

Full-text available

Mar 2021

During the Carnian, oligotrophic shallow-water regions of the western Tethys were occupied by small, coral-rich patch reefs. Scleractinian corals, which already contributed to the formation of the reef structure, owed their position most probably to the symbiosis with dinoflagellate algae (zooxanthellae). Using microstructural (regularity of growth increments) and geochemical (oxygen and carbon stable isotopes) criteria of zooxanthellae symbiosis, we investigated whether this partnership was widespread among Carnian scleractinians from the Italian Dolomites (locality Alpe di Specie). Although corals from this locality are renowned from excellent mineralogical preservation (aragonite), their skeletons were rigorously tested against traces of diagenesis Irrespective of their growth forms, well preserved skeletons of corals from the Dolomites, most frequently revealed regular growth bands (low values of coefficient of variation) typical of modern zooxanthellate corals. Paradoxically, some Carnian taxa ( Thamnasteriomorpha frechi and Thamnasteriomorpha sp.) with highly integrated thamnasterioid colonies which today are formed exclusively by zooxanthellate corals, showed irregular fine-scale growth bands (coefficient of variation of 40% and 41% respectively) that could suggest their asymbiotic status. However, similar irregular skeletal banding is known also in some modern agariciids (Leptoseris fragilis) which are symbiotic with zooxanthellae. This may point to a similar ecological adaptation of Triassic taxa with thamnasterioid colonies. Contrary to occasionally ambiguous interpretation of growth banding, all examined Carnian corals exhibited lack of distinct correlation between carbon ( δ ¹³ C range between 0.81‰ and 5.81‰) and oxygen ( δ ¹⁸ O values range between −4.21‰ and −1.06‰) isotope composition of the skeleton which is consistent with similar pattern in modern zooxanthellates. It is therefore highly likely, that Carnian scleractinian corals exhibited analogous ecological adaptations as modern symbiotic corals and that coral-algal symbiosis that spread across various clades of Scleractinia preceded the reef bloom at the end of the Triassic.

Upper Triassic-Middle Jurassic resedimented toe-of-slope and hemipelagic basin deposits in the Dinaridic Ophiolite Belt, Zlatar Mountain, SW Serbia

Article

Full-text available

Mar 2019
FACIES

In the Dinaridic Ophiolite Belt, small (m-scale) to large (km-scale) blocks of Middle to Upper Triassic, and Middle to Upper Jurassic, more or less silicified bedded limestone are widely present, both as parts of para-autochthonous successions and as redeposited blocks in ophiolitic mélanges. The studied, approximately 230-m-thick succession in the wider area of Zlatar Mountain, is one of the most important para-autochthonous sections in the Serbian part of the Dinaridic Ophiolite Belt. The succession is made up of an alternation of redeposited carbonate toe-of-slope deposits, sand to clay-sized siliciclastic rocks, hemipelagic mudstones and radiolarite-spongiolite basin facies. In the lower part of the sequence, the components of the siliciclastic beds were derived mostly from low-and medium-grade metamorphic rocks. Similar components, together with sand-sized fragments of ophiolitic rocks, were encountered in small amounts in some redeposited carbonate beds. The chronostratigraphic assignment of the succession is based mostly on foraminifers, but age-diagnostic radiolarians and other microfossil groups were also considered. In the lower part of the probably continuous succession, a Norian-Rhaetian assemblage was recognized; a Sinemurian-Pliensbachian assemblage was encountered up-section, whereas the upper part of the succession could be assigned to the Bajocian-Bathonian. Considering the paleogeographic reconstructions and the analogies of age-equivalent sections, the succession records the depositional history of the Bosnian Basin during the Late Triassic to Middle Jurassic period and may contribute to the understanding of the evolution of the Adriatic margin of the Neotethys Ocean in the transition interval from passive to active margin stages.

Carnian reefal blocks in the Slovenian Basin, eastern Southern Alps

Article

Oct 2016

The Carnian Amphiclina beds of the eastern Southern Alps mostly consist of shale and sandstone deposited in the deep-marine Slovenian Basin, which was located near the western margin of the Meliata Ocean. In the vicinity of Cerkno (Slovenia), blocks of massive or crudely bedded limestone crop out within a succession of clastic rocks that are several hundred meters thick. Sponge-microbialite boundstone and coral pillarstone are the predominant facies within these blocks. Oncoid floatstone-rudstone and moderately sorted peloid packstone form crudely layered parts of the blocks, whereas intraclast-cortoid packstone and poorly sorted peloid packstone occur locally in cross-stratified thin beds, truncated at block margins. Detailed mapping further shows that limestone blocks form units at discrete stratigraphic levels within shale and that these units are variable in thickness. Whereas the largest blocks mostly lie concordant to the bedding, smaller blocks are poorly sorted and randomly oriented. All of this evidence suggests that the limestone blocks are olistoliths, derived from an outer platform margin and/or uppermost slope.

Age of the Purported Zhanjin Formation in Gêrzê County, Tibet: A New Understanding and Its Significance

Article

Oct 2015
ACTA GEOL SIN-ENGL

The Upper Carboniferous Zhanjin Formation has attracted much attention from geoscientists for containing glacial-marine diamictite and cold-water fauna typified by the bivalve Eurydesma. The presence of this Formation has provided important evidence for determining the northern border of Gondwana. Previous researchers have classified those strata north of Niangrong Co in the Gêrzê region as part of the Zhanjin Formation based on the presence of glacial-marine diamictite, although the absence of biological fossil evidence has defied clear age determination. Our field investigations first discovered large quantities of corals, sponges and bryozoans. All coral fossils were identified as belonging to the Hexacorallia subclass including 13 genera and 25 species, primarily including Conophyllia guiyangensis Deng et Kong, Coryphyllia regularis Cuif, Cuifia columnaris Roniewicz, Distichophyllia norica Freeh, Distichophyllia gigas Vinassa de Regny, Pamiroseris rectilamellosa Winkler, Retiophyllia clathrata Emmrich, and Retiophyllia paraclathrata Roniewicz. Extensive biostratigraphic correlations show that the hexacorallia should belong to the Late Triassic, thereby negating the presence of the Zhanjin Formation in the study area. Based on analyses of sedimentary facies and detailed study of the glacial-marine diamictite as supposed by earlier researchers, the limestone blocks and gravels within the facies are slope facies olistostromes and waterway sediments from lime slurry debris flows in the submarine fan rather than primary sedimentary products. Among them, lenticular sandstone should be sequentially distributed waterway sand bodies, indicating that the strata have no glacial-marine diamictite. In addition, the rocks containing the mentioned fossils are just limestone blocks from olistostromes, and limestone gravels from waterways of submarine fans. Such a result further negates the presence of the Zhanjin Formation in the study area, and indicates that the age of the studied strata should be youner than the Late Triassic. Through regional stratigraphic comparisons and the study of tectonic settings of the strata, the sedimentary characteristics of the subject strata, including lithology, lithofacies and fossils, are confirmed to be similar to the widely distributed Sêwa Formation in this region. We thus infer that the strata belong to the Middle-Lower Jurassic Sêwa Formation. This finding is important for both studying paleogeography of Tibet and determining the northern boundary of Gondwana.

Upper Triassic (Ladinian?‑Carnian) reef biota from the Sambosan Accretionary Complex, Shikoku, Japan

Article

Oct 2015

The Middle and Late Triassic was a time of important reef development. This evolution, which is primarily documented in the Tethys realm, comprised several phases from the Anisian to the Rhaetian. To help elucidate the less constrained reef evolution in the Panthalassa domain, samples of reef limestone were collected from several localities along the Sambosan Accretionary Complex in Shikoku Island, southwest Japan. In this paper, we report a well-preserved and comprehensive reef biota, including several taxonomic groups, such as scleractinian corals, calcified sponges, calcareous algae, foraminifers, and microproblematica. Seventeen species are described for the first time in Japan among the 33 that are identified in this study. The assemblage-based biostratigraphy and index taxa indicate a Ladinian?-Carnian age. This new finding corresponds to an older reef limestone than has been previously identified in the Sambosan Accretionary Complex and may represent the initiation of shallow-water carbonate deposition on western Panthalassa seamounts. This work also provides valuable insights on reef ecosystem biodiversity in the Panthalassa domain during the Middle? to Late Triassic.

Upper triassic (Norian-Rhaetian) hypercalcified sponges from the lut block, East central Iran

Article

Full-text available

Dec 2014

In order to study the hypercalcified sponges in reefal deposits of the Nayband Formation in Lut Block, the Garm Ab section near the village of Mehran Kushk, located about 20 km northeast of Ferdows city, was sampled. Eight horizons of reefal limestone beds are exposed in this section. The most important reef builders are hypercalcified sponges with some representatives of hexactinellids, scleractinian corals and other reef organisms. The field and lab-observations on rock units, sedimentary facies and faunal assemblages indicate the middle Norian-Rhaetian as the age of the reef horizons. Twenty-three sponge taxa, including 15 of the chambered sphinctozoans, 2 of hexactinellids sponges and 8 non-chambered inozoan were identified. The majority of recognized sponges are reported from the Nayband Formation from the other localities in central Iran. One new species identified as Cryptocoelia maxima n. sp. was recovered and is described here.

Critical review of Pseudocucurbitidae (Miliolina, Foraminiferea) from the Late Triassic reef environments of the Tethyan area

Article

Full-text available

Jul 2012

The Late Triassic foraminiferal genera Amphorella, Spiriamphorella, Urnulinella, Pseudocucurbita, Paratintinnina, Costifera and Siculocosta are considered junior synonyms of the genus Cucurbita. Consequently, the number of families of the Milioliporacea (Miliolina) is significantly reduced. The valid species of the genus Cucurbita are considered to be Cucurbita infundibuliforme Jablonský, 1973, C. subsphaerica (Borza & Samuel, 1977a) comb. nov., C. longicollum Senowbari-Daryan, 1983, C. battagliensis (Senowbari-Daryan, 1983) comb. nov., C. cylindrica (Senowbari-Daryan, 1983) comb. nov. and C. floriformis (Altiner et al., 1992) comb. nov.

Upper Triassic (Norian) hypercalcified sponges from the Musandam Peninsula (United Arab Emirates and Oman)

Article

Full-text available

Aug 2008

Supercalcified sponges, including sphinctozoans, inozoans, chaetetids, spongiomorphids, occurring in Upper Triassic (Norian-Rhaetian) shallow-marine limestones of Musandam Mountains in United Arab Emirates (UAE), are described. The following taxa were determined: sphinctozoans: Hajarispongia osmani Senowbari-Daryan and Yancey, Nevadathalamia arabica n. sp., Nevadathalamia conica n. sp., Fanthalamia milahaensis n. sp., Iranothalamia incrustans (Boiko), Cinnabaria regularis n. sp.; inozoans: Cavsonella triassica n. sp., Molengraaffia regularis Vinassa de Regny, Peronidella? sp., Circopora cf. caucasica Moiseev, Circopora? sp.; spongiomorphids: Spongiomorpha sp.; chaetetids: Lovcenipora chaetetiformis Vinassa de Regny, Lovcenipora musandamensis n. sp., Lovcenipora sp., chaetetid sponge gen. et sp. indet. The most abundant sponge in the studied material is Nevadathalamia arabica n. sp. The described sponge association of the Arabian shelf (Musandam Mountains) shows close affinity to the sponge association known from age-equivalent terranes in the Panthalassa Ocean (Sonora Mountains in Mexico; Pilot Mountains in Nevada, USA), but is remarkably different from sponge associations in carbonates bordering the Tethys. This difference goes along with the biogeography of wallowaconchid bivalves and is most likely attributed to climatic, palaeogeographic or oceanographic factors.

Differential severity of Permian–Triassic environmental changes on Tethyan shallow-water carbonate platforms

Article

Jan 2007
GLOBAL PLANET CHANGE

Significantly different Guadalupian–Late Triassic patterns are observed in the evolution of attached and isolated carbonate platforms of the southwestern Tethys (Oman Mountains). Close to the rim of the attached Arabian platform, carbonates of the Saiq and Mahil Formations reveal an almost complete Permian–Triassic sedimentary record. Guadalupian–Changhsingian 3rd order sequences consist of fossiliferous transgressive systems tracts and monotonous highstand systems tracts with mud/wackestone and coral bafflestone. The youngest Changhsingian beds are bioturbated floatstone with crinoids, sponges and bryozoans. All sediments indicate a healthy, tropical carbonate production. Above, a unique facies change begins with a pyrite-encrusted omission surface. Greenish mudstone rich in authigenic pyrite infills the relief of the unconformity and is overlain by clastic sediment and by laminated, microbialite-bearing carbonate. Unfossiliferous sediments and seafloor cements indicate a change in carbonate production towards abiotic processes. Prevailing anoxic conditions were interrupted by seven oxic event beds, as indicated either by low-diversity and small-sized ichnotaxa or by shell beds with low-diversity bivalve and crinoid assemblages. By comparison with published data, the described sedimentary sequence can be assigned to the Changhsingian–earliest Griesbachian. Beginning probably with the Anisian, bioturbated Griesbachian–Dienerian recovery period and the unconformity below to the latest grain-supported sediment textures mark the return to biogenic tropical carbonate production under oxic conditions. The Middle–Late Triassic carbonate platform consists of stacked high-frequency shallowing upward cycles. By contrast, carbonate production of Neo-Tethyan isolated platforms was discontinuous and interrupted by a large gap. Guadalupian deposits of the Al Jil Formation consist of bioclastic limestone typical of a tropical carbonate production. The uppermost bed, an impoverished bioclastic packstone capped by an unconformity, marks the onset of platform drowning which resulted from the end-Guadalupian mass extinction. Above, a polymict breccia witnessed rift pulses of the Neo-Tethys. The overlying pelagic mud- and packstone contains radiolarians and rare foraminifera of Lopingian age, and overlying microbialites. In the Carnian, tropical shallow-water carbonate production restarted with a low-relief platform and culminated in a Norian–Rhaetian reef-rimmed platform. Stacked Lofer cycles dominated the inner platform of Jebel Kawr (Misfah Formation). We here propose a differential onset and severity of the Late Permian mass extinctions for carbonate platforms. On the Arabian Plate, tropical carbonate production collapsed after the end-Lopingian mass extinction and was replaced by microbialites and sea-floor cements during the earliest Triassic. After approximately six million years, tropical shallow-water carbonate production resumed in the Middle Triassic. Neo-Tethyan isolated platforms drowned shortly after the end-Guadalupian mass extinction and did not recover before the Late Triassic. Absence of shallow-water limestone suggests that carbonate production of isolated platforms ceased for about 30 million years, a period exceeding the recovery of most marine ecosystems.

Amblysiphonella agahensis nov. sp., and Musandamia omanica nov. gen., nov. sp. (Porifera) from the Upper Triassic of Oman

Article

Jan 2010

Two chambered sponges - A. agahensis nov. sp. and Musandamia omanica nov. gen., nov. sp. - from the Norian reefal limestones of Jebel Agah, southeast of the Musandam Mountains, Oman, are described. Both species are the first reported from the Triassic of the Arabian Peninsula. The fossil association is also mentioned.

Paleotectonic and paleoceanographic controls on microbial-serpulids communities in the Norian-Rhaetian carbonates of Italy: a synthesis

Book

Full-text available

Dec 1999

In this paper are presented sedimentological and paleontological data concerning the bioconstructed platform margin facies of many different Norian-Rhaetian carbonate successions on Italy. The paper mostly consists of an updating of already separately published data plus additional ones from Northern Calabria. This presentation is the result of a coordinated research project financed by the CNR, aimed tothe comparison of all the Upper Triassic microbial-serpulid dominated bioconstructions discovered in Italy in the last fifteen years. Final scope was to envisage the common paleotectonic and paleoceanographic factors controlling the genesis of these peculiar biofacies. The investigated areas comprise Southern Alps (Lombardy Basin to the west and Carnia Basin to the east), a limited sector of the Austroalpine (Ortles), Northern Apennines (Monte Cetona), Central Apennines (Monti Simbruini) and Southern Apennines (Monti Lattari, Monti Picentini, Monti di Praia and Monte Montea). For each area, the geological setting, the stratigraphy of the Upper Triassic successions and the bioconstructed facies are described. In the case of Monte Montea area (Northern Calabria) the stratigraphy evolution from the Ladinian-Carnian depositional system to the Norian-Rhaetian carbonate platform with microbial-serpulid-sponges biofacies is here presented for the first time. The comparated study of all the occurrences indicate that microbial communities associated with serpulids were the main constructors in most Norian-Rhaetian carbonate buildups in that part of the shallow western Tethys Gulf characterized, during the Norian, by the Dolomia Principale depositional system. The buildups developed on the margin of small-sized, relatively shallow intraplatform basins. More limited buildups are also found in the mixed carbonate-siliciclastic ramps that characterize the Upper Norian-Rhaetian of Northern Apennines and Lombardy. Two main kind of platform-basin transitions have been described: rimmed carbonate platform, developed in the Lower-Middle Norian in the Northern areas and possibly persisting up to the Upper Rhaetian in Central and Southern Apennines. This type of system can be further subdivided in progradational and aggradational/backstepping ones; homoclinal siliciclastic carbonate ramps in the Upper Norian – Rhaetian of Western Alps and Northern Apennines. These intraplatform basins developed along a belt, extending from Southern Alps through the Apennines until the Betic Cordillera, affected by extensional-transtensional tectonics since Lower Norian. Production of the carbonate platform areas occurred from Uppermost Norian, owing to climate change and tectonic dissection. These tectonics slightly predate the Jurassic Piedmont-Ligurian Ocean opening, which occurred immediately to the north and west of this belt. In all the localities the intraplatform sediments are represented by laminated and resedimented doloarenites and calcarenites, alternating with abundant breccia deposits. Dark basinal sediments characterize the most distal areas: they are often rich in organic matter and lack any evidence of benthic life. The mound complexes, up to several hundreds of meter thick, developed on the other platform margin-upper slope. They formed at a depth comprised from just above the wave-base level, to the very quiet water of the middle-lower slope, possibly down to a depth of some 200 meters. The main biomass of the buildups was largely dominated by microbialites, but their peculiarity is the widespread presence of serpulids. In the associated facies little sized organisms (bivalvs, brachiopods) are frequent, together with some dasycladacean algae. Only in northern Calabria little sphinctozoans become a significant builders group. The dominance of microbialites and serpulids was clearly related to marine conditions unsuitable for the development of coralgal reefs. The comparison of recent and past occurrence of microbial and serpulid buildups with the sedimentological characteristics common to all the studied occurrences, indicated that low oxigen concentration in sea water and mesosalinity appear the most reliable mechanism to explain the Norian buildups. Eutrophy of water mass, due to high particulate input, is more likely for less widespread Upper Norian to Rhaetian buildups. Microbial-serpulid bioconstructions formed a minor, yet significant ecological province in the shallow western Tethys, as opposed to the to highly diversified, sponges and coral dominated Dachstein reefs present in Eastern Alps and Sicily and widespread all along the southern Tethys margin as far as to Australia. While the latter developed in connection with open marine basins related to the oceanic areas of the Tethys, the microbial-serpulid buildups are systematically associated to narrow troughs with restricted circulation and limited exchange with open marine basins. Only in Eastern Carnia and Northern Calabria, the character of the observed marginal biofacies suggest a closer proximity to an open marine area. This is in agreement with those paleogeographical reconstructions which envisage a deep marine area separating Sicily from Southern Italy. Key Words: Upper Triassic, microbialites, serpulids, intraplatform basins, platform margin, mixed ramps, buildups, geodynamics, paleogeography, dysoxic environments, Italy, Alps, Apennines.

Carnian reef biota from a megabreccia of the Hawasina complex (Al Aqil, Oman)

Article

Full-text available

Dec 1999

Carnian reef biota and brachiopods of the Misfah Formation (Hawasina complex) from a locality near the town of Al Aqil in Oman are described. A new brachiopod species, Oxycolpella arabica n. sp. is described. The composition of the Carnian reef biota in Oman is similar to those known from the Alpine-Mediterranean region. However, differences exist in the microfauna of reef dwellers, e.g. foraminifers. New stratigraphic data based on reef organisms and conodonts are presented.

Rhaetian scleractinian corals in the Western Carpathians

Article

Full-text available

Dec 1998
GEOL CARPATH

The paper presents the distribution and taxonomy of the Rhaetian coral fauna in the Tatric, Fatric, Hronic and Silicic paleogeographical zones of the Western Carpathians. The taxonomic spectrum of the corals from the Fatric zone is the most typical of the Carpathians, and resembles that of the Alps in the abundance of reimaniphylliid corals and frequent phaceloid growth forms, but it differs from the Alpine spectrum in its lower generic diversity. The assemblage from the northernmost zone, formed by the Tatric Superunit, is closest to the Early Jurassic fauna from the British Isles. Two new species are described: Zardinophyllum carpathicum sp.n. and Stylophyllopsis bobrovensis sp.n.

Paleotectonic and paleoceanographic controls on microbial-serpulids communities in the Norian-Rhaethian carbonates of Italy: a synthesis.

Article

Full-text available

Jan 1999

Slide Set of Paleogeographic Atlas

Technical Report

Full-text available

Jun 1992

1992.12

Lofer cyclothems revisited (Late Triassic, Northern Alps, Austria)

Article

Full-text available

Dec 1998
FACIES

Fischer's classic study (1964) of the Upper Triassic “Lofer” cyclothems in the Dachstein Limestone of the Northern Calcareous Alps was seminal to many studies of the Dachstein and to carbonate cycles globally.Fischer's idealized cycle is deepening upward, ABC in his terminology, where member A is a surface or interval of subaerial exposure, B is tidal deposits, and C is shallow subtidal. Studies of the Dachstein from the elsewhere in the northern Alps have substantiatedFischer's upward-deepening ABC cycle, butGoldhammer et al. (1990) andSatterley (1996a) reinterpreted the type Lofer cycles as shoaling upward. We measured 139 m of Dachstein Limestone incorporating 25 cycles at Steinernes Meer, Austria, nearFischer's most extensive section. In this section we identified no A members. The section is punctuated by slightly reddish horizons (‘pink partings’) that in some cases may reflect brief subaerial exposure, but generally appear to be pressure-solution zones that have concentrated iron oxides but lack a distinctive isotopic signature. B members are readily distinguished by fenestral porosity, stromatolitic lamination, partial dolomitization, intraclasts, or desciccation cracks. They are relatively thin (5 to 155 cm; median thickness is 38 cm.) and in some cases laterally variable or discontinuous. C members are characterized by molluscan wackestones and packstones with diverse biota. C intervals are 25 cm to 26 m thick (median 4.1 m) and comprise 91% of the interval measured. Pervasive bright-red internal sediment, which appears commonly within the B and C members, does not derive from any interval observed within the measured section, but from sources, possibly paleosols, much higher in the section. It is spatially associated with near-vertical, ENE-trending (62o) fractures filled with the sediment, brachiopods, and cement. Such fractures cut stratigraphic intervals as thick as 70 m without an exposed top or base.

Characteristics of peritidal facies and evidences for subaerial exposures in Dachstein-type cyclic platform carbonates in the Transdanubian Range, Hungary

Article

Full-text available

Aug 2004

János Haas

In the Late Triassic, an extremely large carbonate platform system (Dachstein-type platforms) developed on the margin of the Neotethys. On the wide inner platform cyclic peritidal, lagoonal successions were deposited. In the Transdanubian Range (Hungary), the lower part of the 1.5–2-km-thick cyclic succession (Upper Tuvalian–mid-Norian) is pervasively dolomitised, the upper part (Upper Norian–Rhaetian) is non-dolomitised; there is a transitional interval between them made up of partially dolomitised cycles. The peritidal–lagoonal cycles are commonly bounded by well-developed disconformity surfaces reflecting subaerial erosion that punctuated the marine carbonate accumulation. Truncation of the cycles was preceded by pervasive cementation of the previously deposited cycle. In the early stage of the platform evolution, tidal flat dolomitisation under semi-arid conditions led to the consolidation of the previously deposited sediments. The truncation surfaces were commonly covered by dolocretes. During the more humid Late Norian–Rhaetian period, the early cementation was followed by karstification, accumulation of wind-blown dust and pedogenesis. Erosion during regularly recurring subaerial exposure that commonly reached the previously deposited subtidal beds suggests eustatic control of the cyclicity and supports the application of an allocyclic model, even if the Milankovitch signal is imperfect.

Rhaetian corals of the Tatra Mts

Article

Jan 1974

Ewa Roniewicz

Upper Triassic (Carnian-lowermost Norian) corals from the Pantokrator Limestone of Hydra (Greece)

Article

Jan 1994

Facies development and paleoecologic zonation of four Upper Triassic patch-reefs, northern Calcareous Alps near Salzburg, Austria.

Chapter

Jan 1981

Four Upper Triassic patch-reefs exposed in the Northern Limestone Alps of the Salzburg area of Austria were studied. Emphasis was placed on facies development and paleoecologic zonation. The Adnet Reef structure grew directly on a carbonate platform in a shallow water carbonate setting; the Rotelwand and Feichtenstein Reef complexes grew out of the Kossen Basin in 2 distinct stages. This study has demonstrated that calcareous algae, various microproblematica, and foraminifers show very distinct distributional patterns within the reef complexes, and can be used as facies indicators as well as differentiating different biotopes within the central reef areas.-from Authors

Rhät-Foraminiferen aus dem Kuta-Kalk des Gurumugl-Riffes in Zentral-Papua/Neuguinea

Article

Jan 1990

E. Kristan-Tollmann

Nachweis einiger Riff-Foraminiferen und Problematika in den norischen Dachsteinkalken des Gosaukammes (Österreich)

Article

Jan 1996

Geology of the Oman Mountains

Article

Jan 1974

Mikrofazielle und geochemische Gliederung eines obertriadischen Riffes der nördlichen Kalkalpen (Sauwand bei Gusswerk, Steiermark, Österreich)

Article

Jan 1963

PALEOECOLOGY AND FACIES OF UPPER TRIASSIC REEFS IN THE NORTHERN CALCAREOUS ALPS

Chapter

Jan 1981

ERIK FLÜGEL

Mikrofazielle und geochemische Gliederung eines obertriadischen Riffes der nordlichen Kalkalpen

Article

Jan 1962

Lofer cyclothems of the alpine Trias

Article

Jan 1964

A.G. Fischer

Tidal Deposits, Dachstein Limestone of the North-Alpine Triassic

Chapter

Jan 1975

Alfred G. Fischer

Late Triassic (Norian-Rhaetian) limestones, 1,000 to 1,500 meters thick, consist of interbedded lagoonal limestones (90 percent) and intertidal-supratidal dolomitic limestones (10 percent). The belt was originally some 20 km wide, extending some 250 km from the Loferer and Leoganger Steinberge in the west, through the region of Berchtesgaden and Salzburg, toward Vienna. It is bounded on the south by a belt of reefs defining the southern edge of the Dachstein bank, and on the north by the Hauptdolomit ultrabackreef facies. The deposit is well exposed in the many mountain faces and high plateaus of the region; lower and readily accessible exposures south of Salzburg include cuts and a quarry near Golling (Pass Lueg), and at Berchtesgaden, the road from Obersalzberg to Hitler’s “Eagle’s Nest” on Mt. Kehlstein. Rocks are moderately deformed, with primary porosity lost by cementation.

Zur Sphinctozoen-Fauna der obertriadischen Riffkalke ('Pantokratorkalke') von Hydra, Griechenland

Article

Jan 1983

Der Hohe Göll. Aufbau und Lebensbild eines Dachsteinkalk-Riffes in der Obertrias der nördlichen Kalkalpen

Article

Jan 1969

H. Zankl

Triassic reef patterns

Chapter

Jan 2002

ERIK FLÜGEL

Upper Triassic (Carnian-Lowermost Norian) Corals from the Pantokrator Limestone of Hydra (Greece)

Article

I Festschrift

Obertrias-Korallen (Karn-Unterstes Nor) aus dem Pantokrator-Kalk von Hydra (Griechenland) Zusammenfassung Aus dem Pantokrator-Kalk der Insel Hydra (Griechenland) werden 24 Korallenarten, zugehörig zu 14 Genera, beschrieben. Zwei Genera und 7 Arten sind neu: [Palaeastraea mandrakiensis n.sp., Stuoresiafluegeli n.sp., Conophyllia hellenica n.sp., Hydrasmilian.Q.: H. rhythmica n.sp., H. fossulata n.sp., H. ornamenta n.sp., Craspedophyllia graeca n.g.n.sp.). Die Korallen bestätigen das Alter der Lokalitäten als Kam bis unterstes Nor. Die Arten können meist mit südeuropäischen Lokalitäten (Italien, Slowenien, Südungarn, Rumänien, Türkei) verglichen werden und scheinen in südlichen Flachwasserberei-chen der Tethys vorzuherrschen. Trotzdem, beinahe ein Drittel der neuen Arten spricht für spezielle und etwas differenzierte Lebensbedingungen in Hydra während der karnischen Periode. Abstract From the Pantokrator limestone of the Island Hydra, Greece, 24 species of corals belonging to 14 genera are described. Two genera and seven speciesare new (Palaeastraeamandrakiensisn.sp., Stuoresiafluegelin.sp., Conophylliahellenican.sp., Hydrasmilian.g.: H, rhythmican.sp., H. fossulatan.sp., H. ornamenta n.sp., Craspedophyllia graeca n.g.n.sp.). Corals confirm Carnian to lowermost Norian age of localities. Coral species can mostly be compared with south European localities (Italy, Slovenia, south Hungary, Romania, Turkey), and seem to predominate in southern shallows of Tethys. Nevertheless, almost one third of the new species indicate special and somewhat different environments in Hydra during the Carnian period.

Problems with reef models: the Late Triassic Steinplatte" reef"(Northern Alps, Salzburg/Tyrol, Austria)

Article

Dec 1989
FACIES

Summary The Late Triassic limestones of the Steinplatte near Waidring at the Austrian/German boundary have become a classical example of an ancient reef, formed at a carbonate shelf margin (“framebuilt reef rim”). Evaluation of the stratigraphic framework and the investigation of cliff wall sections, together with the analysis of microfacies, paleontological and geochemical data, result in a very different interpretation of the depositional history. A “non-reef” model is favoured: Bioclastic deposition on a carbonate ramp grading into a slope. The Steinplatte is made up of three depositional units: 1) Kössen facies; 2) mound facies, the apparently massive carbonates of the Oberrhätkalk; 3) capping facies, the upper-most strata of the Oberrhätkalk. The Kössen facies comprises predominantly fine-grained lithobioclastic packstones. Changes in microfacies types and in sedimentary structures indicate an increase in water energy trough time. Local biostromal “mounds” (“A-, B-, and C-reefs”; mounds at the base of the Steinplatte cliff) were formed at the same stratigraphical level. Influence of these low relief mounds on the sedimentation in adjacent areas was subordinate except for a mound at the southwestern corner of the Steinplatte acting as a mounding nucleus on the carbonate ramp of the Kössen facies. The mound facies makes up the bulk of the Oberrhätkalk of the Steinplatte. It consists predominantly of fine- and medium-grained bioclastic carbonate sands, shell coquinas and some thin, small-scaled autochthonous boundstone structures (predominantly calcisponge limestones). Patches of dendroid corals occur in the lowermost mound facies. The source of most coral bioclasts and fine-grained coral debris, occurring within various levels of the mound facies, probably were coral patches high on the slope or on a platform. Several shell beds as well as a conspicuous “White Bed” can be used as time lines in the reconstruction of the depositional events. Sedimentation on a depositional slope is indicated by the predominance of northward dipping beds in the area of the western cliff wall. To the south (west of Wieslochsteig) horizontal bedding becomes more evident, pointing to a change from ramp to platform edge type sedimentation. The capping facies comprises thick-bedded strata dipping off and wrapping around the northern and eastern sides of the mound-shaped surface of the mound facies. These strata were deposited sobsequent to a change in sea level on the moundshaped surface of the mound facies. The capping facies differs from the mound facies in attidude, increase in bioclastic coated grainstones with abundant algae and in the occurrence of “coral gardens” representing a veneer on parts of the mound facies. Sea-level fluctuations are indicated by repeated vadose diagenesis and by distinct upslope-down-slope zonations of the biota. The general facies model of the Steinplatte is shown in Fig. 33. It corresponds to a development from a carbonate ramp (prior to the deposition of Shell Bed III) to a slope, probably grading into a platform to the south. The non-reef character of the mound facies of the Steinplatte limestone is accentuated by the lack of organic frames (in the coral thickets), the lacking influence of calcisponge frames on adjacent sediments, lack of ecological successions, and by the predominance of skeletal sediment consisting of mollusk, echinoderm and allochthonous coral debris, in contrast to only small amounts of frameworks. General implications of the Steinplatte study to the investigation of ancient “reefs” concern the interpretation of “potential frame-building” organisms as actual frame-builders and the interpretation of so-called “reef-detritus”.

Fazielle und paläontologische Untersuchungen in oberrhätischen Riffen (Feichtenstein- und Gruberriff bei Hintersee, Salzburg, Nördliche Kalkalpen)

Article

Dec 1980
FACIES

Baba Senowbari-Daryan

Zusammenfassung Im Hangenden der Kössener Schichten sind in den Nördlichen Kalkalpen zahlreiche kleine Riffe (“patch-reefs”) eingeschaltet, die in der Literatur verschieden benannt werden und im allgemeinen als “Oberrhät”-Riffe bekannt sind (vgl. Fabricius 1966:20; Tollmann 1976:258). Mehrere dieser Riffe befinden sich im Land Salzburg (Osterhorngruppe). Vier nahe beieinander liegende Riffe bildeten das Thema von zwei Dissertationen im Paläontologischen Institut der Universität Erlangen-Nürnberg. P. Schäfer bearbeitete das Rötelwand-Riff im Mörtelbachtal und das Adnet-Riff bei der Ortschaft Adnet (beide nahe Hallein, vgl., P. Schäfer 1979). In der vorliegenden Arbeit werden die Untersuchungsergebnisse des Feichtenstein- und des ca. 3 km südlich gelegenen Gruber-Riffes vorgestellt (österreichische Topographische Karte 1∶25000, Bltt Hintersee, 94/2; 47° 42′, 25″;−13° 17′ 50″ bzw. 47° 41′ 10″;−13° 18′, 14″). Der Schwerpunkt der Untersuchungen liegt auf der paläontologischen Bearbeitung der riffbildenden Organismen. In Abschnitt 4.3.1 findet sich eine übersichtsliste der festgestellten Arten.

Facies and environment of the Leckkogel beds (Carnian;Alps)

Article

Dec 1982
FACIES

The Carnian Leckkogel beds represent a carbonate sequence, which was deposited in front of an actively spreading carbonate platform. The typical Leckkogel beds are characterized by highly diverse sponge buildups. Sphinctozoan sponges predominate together with rare bryozoans and hydrozoans as well as red algae and thin crusts of cyanophyceans. Foraminifera are very rare and dasycladaceans are missing altogether. Oncoidal limestones containing predominantly inozoans are coeval with the Leckkogel beds. They represent a short-lived colonization of the sea-floor within a basinal environment. In addition to this autochthonous development, allochthonous intercalations of debris-flow sediments occur. The basinal facies consists of shales and argillaceous schists. Towards the edge of the platform the Leckkogel beds interfinger laterally with the Tisovec limestone, which exhibits two main facies types, a reef facies and a lagoonal facies.

Depositional cycles, composite sea-level changes, cycle stacking patterns, and the hierarchy of stratigraphic forcing: Examples from Alpine Triassic platform carbonates

Article

May 1990

Carbonate platform deposits record a complex interplay of numerous geodynamic variables, of which eustasy, subsidence, and sediment accumulation are prime factors in determining both the kilometer-scale (depositional sequence scale) and meter-scale (depositional cycle scale) stratigraphic packaging. In this study, we looked particularly at composite eustasy, that is, superimposed sea-level fluctuations with different frequencies (defined as orders) and different amplitudes, and the role it plays in the linkage between meter-scale cyclic stratigraphy and kilometer-scale sequence stratigraphy. Specifically, we have investigated the relationship between low-frequency, third-order (1-10 m.y. period) depositional cycles and their component high-frequency, fourth-(0.1-1 m.y.) and fifth-(0.01-0.1 m.y.) order cycles through detailed stratigraphic analyses of Alpine Triassic platforms, complemented by computer modeling. On the basis of our results, we suggest that in general, there exists a hierarchy of stratigraphic forcing driven by composite eustasy that results in organized stacking patterns (thickness, subfacies character, early diagenetic attributes) of high-frequency, typically fourth- and fifth-order, shallow-water carbonate cycles dictated by low-frequency, third-order relative sea-level effects. We suggest that systematic vertical changes in stacking patterns of high-frequency cycles across a larger depositional sequence are due to systematic and predictable differences in depositional space available during the rising and falling stages of a relative third-order sea-level change. We also suggest that these systematic variations in cycle stacking patterns will exist regardless of the mechanism responsible for generating the high-frequency cycles, be it an autocyclic or allocyclic mechanism. This approach has major implications for the use of high-frequency, fourth- and fifth-order cycle characteristics to identify third-order cycles in outcrops and cores of shallow-water carbonates, where stratigraphic control may be less than desirable. This would constitute a valuable bridge between cyclic stratigraphy at the meter scale and sequence stratigraphy at the seismic scale. We present two examples from Triassic buildups of the Alps (the Ladinian Latemar buildup and the Norian Dolomia Principale) where a systematic succession of high-frequency cycle stacking patterns and early diagenetic features exists within an overriding third-order cycle (sequence) reflecting the interplay of short-term, high-frequency (fourth, fifth order) eustasy and long-term, low-frequency (third order) eustasy in accordance with the hierarchy of stratigraphic forcing. Central to the interpretation of these examples is the demonstration that true eustatic rhythms are recorded in the high-frequency cyclicity, as verified by time-series analyses and the use of "Fischer plots." These examples can be modeled by computer under conditions of lag-depth-constrained sedimentation, uniform subsidence, and composite eustasy. We also present two examples, one from the Alpine Triassic (the Norian Lofer cyclothems) and one from the Pleistocene of south Florida, that lack both a systematic succession of high-frequency cycle stacking patterns and identifiable composite rhythms in the stratigraphic record, despite the existence of composite high-frequency eustasy. In these examples, we call upon (1) local tectonic forcing in the form of short-term deviations in subsidence via faulting (Lofer example) and (2) large differences in the relative amplitudes of different orders of high-frequency sea-level oscillations (Pleistocene example) to explain the lack of composite rhythms, and we present computer simulations to illustrate the concepts. An understanding of composite relative sea-level changes and the potential for a hierarchy of stratigraphic forcing provides the link between cyclostratigraphy and sequence stratigraphy and also has important implications regarding the stratigraphy of early diagenesis.

An accretionary distally steepened ramp at an intrashelf basin margin: an alternative explanation for the Upper Triassic Steinplatte “reef” (Northern Calcareous Alps, Austria)

Article

Mar 1995
SEDIMENT GEOL

The Upper Triassic massive limestone (the Oberrhdtkalk) at the Steinplatte, Austria, formed along the edge of an intrashelf basin that was situated within a shallow-marine to supratidal shelf approximately 40 km wide. This transition from shelf to intrashelf basin is marked by a distinct slope break that has been widely cited as an example of a reef-rimmed shelf. It is, instead, a distally steepened ramp. The Oberrhdtkalk consists of the ramp sediments lying between the Dachsteinkalk of the shelf and the Kössen Formation of the intrashelf basin. The ramp interpretation is based on the geometry and lateral facies progression in the profile from the shallow-marine to peritidal shelf, across the ramp, and into the basin, and on the absence of reef or grainstone deposits at the slope break typical of a rimmed shelf.The Oberrhdtkalk at the Steinplatte is an important example of shelf-margin deposition because: 1.(1) It formed in a protected and low-energy intrashelf basin setting, thus expanding the range of distally steepened ramps that have been used to develop a general model.2.(2) It differs from previously described examples of distally steepened ramps, largely from open-ocean shelf-margin settings, in that: (a) it evolved constructionally from a homoclinal ramp rather than forming at a drowned shelf edge or an antecedent tectonic structure; (b) the sediments of the distal slope are largely autochthonous; (c) slumping and breccia deposits on the distal slope are of minor importance; turbidites on the basin floor are absent; and (d) skeletal packstone and grainstone characterize the outer ramp and slope rather than mudstone and wackestone.3.(3) It provides an alternative ramp model for other Upper Triassic shelf and platform margins in the Northern Calcareous Alps, which have commonly been interpreted as reef or sediment rimmed.

Erratum to “Supersequence and composite sequence carbonate platform growth: Permian and Triassic outcrop data of the Arabian platform and Neo-Tethys” [Sediment. Geol. 158 (2003) 87–116]

Article

Aug 2003
SEDIMENT GEOL

Upper Triassic reefs and reef biota in Sicily

Article

Jan 1982
FACIES

Paläontologie, Fazies und Geochemie der Dachstein-Kalke (Ober-Trias) im südwestlichen Gesäuse, Steiermark, Österreich

Article

Dec 1980
FACIES

Wolf-Christian Dullo

The Upper Triassic (predominantly Norian) Dachstein limestones in the southwestern Gesäuse Mountains (Styria, Austria) exhibit different facies types characterized by significant distributional patterns of organisms and nonskeletal grains. Most valuable facies-diagnostic organisms are foraminifera and calcareous algae. The quantitative distribution patterns of the foraminifera can be used to separate facies units and local biotopes within the reef-complex. Thecentral reef facies (widespread in the Kalbling reef and Schildmauer reef) is defined by an autochthonous reef-framework (composed of corals, calcisponges, algae, and many epizoans), which interfingers with quantitatively prevailing reef debris. The reef-framework consists of various biocoenoses (high growing corals, low growing corals, calcisponges, hydrozoa and bryozoa, solenoporacean algae). Within the organic framework the foraminiferaAlpinophragmium perforatum, Ophthalmidium sp.,Agathammina sp. as well as sessile miliolids and arenaceous forms are most typical. In small cavities of the framework internal micritic sediments with peloids can be found, together with a characteristic association of microfossils (foraminifera:Ophthalmidium martanum, O. leischneri, Sigmoilina sp.,Galeanella sp., “Lituosepta”; microproblematica:Baccanella floriformis, Muranella sphaerica). Thefore-reef facies can be studied south of the Kalbling reef. This facies type is characterized by sparry rudstones composed of angular litho- and bioclasts which have been derived from the central reef. In some parts an unusual interfingering of the fore-reef facies and lagoonal sediments can be seen indicating the existence of channels within the reef-complex. North of the central reef area thegrapestone facies of the back reef environment is developed: Non-skeletal particles are grapestones, algal lumps, and coated grains. The algal flora is characterized byDiplopora, Heteroporella and some porostromate cyanophyceans (type “Cayeuxia”). Among the foraminiferaAulotortus communis, A. tumidus, Duostomina sp. and “Tetrataxis” are frequent elements. With increasing distance from the central reef area the grapestone facies interfingers with the “algal-foraminifera facies” showing similar nonskeletal components but different associations of algae and foraminifera.Griphoporella andGyroporella are the prevailing algal genera. The foraminifera fauna is characterized byAulotortus sinuosus, A. communis andQuinqueloculina sp.. This facies is found also in small depressions and channels within the grapestone facies. The “pelletal-mud facies” and the “mud facies” represent the lagoonal environments of the reef-complex. Both facies types occur in greater distance from the central reef area than the algal-foraminifera facies and the grapestone facies. In the limestones of the pelletal-mud facies peloids, fecal pellets, coated grains and a specialized foraminifera association (Aulotortus friedli, A. tenuis, Endothyra sp.,Endothyranella sp.,Trochammina sp.,Agathammina sp.) are common. Peloids and fecal pellets are found also in the rocks of the mud facies, together with small, often thin-shelled foraminifera (Aulotortus friedli, A. tenuis, lagenids). The “loferite facies” interfingers with both facies units. Pelletal loferites and stromatolithic algal loferites can be distinguished. The distributional patterns of thegeochemical data (CaCO3, MgCO3, SrCO3, rare elements like Fe, Mn, Zn and Cu, insoluble residues) show no correlations with the facies types of the limestones except strontium which seems to be concentrated in micritic limestones rather than in sparitic grainstones and rudstones.

Facies and biota of Anisian to Carnian carbonate platforms in the Northern Calcareous Alps (Tyrol and Bavaria)

Article

Dec 1997
FACIES

Summary During the Middle and early Late Triassic carbonate ramps and rimmed platforms developed at the northwestern margin of the Tethys ocean. In the Northern Calcareous Alps, Anisian stacked homoclinal ramps evolved through a transitional stage with distally steepened ramps to huge rimmed platforms of Late Ladinian to Early Carnian age. Middle Triassic to early Late Triassic facies and biota of basin, slope and platform depositional systems are described. Special emphasis is given to foraminifers, sponges, microproblematic organisms and algae. The Ladinian to early Carnian reef associations are characterized by the abundance of segmented sponges, microproblematica, biogenic crusts and synsedimentary cements. Among the foraminifers, recifal forms likeHydrania dulloi andCucurbita infundibuliformis (Carnian in age) are reported from the Northern Calcareous Alps for the first time. Some sphinctozoid sponges likeParavesicocaulis concentricus were known until now only from the Hungarian and Russian Triassic.

Fazielle Entwicklung und Palökologische Zonierung Zweier Obertriadischer Riffstrukturen in den Nördlichen Kalkalpen (“Oberrhät”-Riff-Kalke, Salzburg)

Article

Dec 1979
FACIES

Priska Schäfer

Susammenfassung Die obertriadischen Reffstrukturen von Adnet und der Rötelwand bei Hallein eatwickelten sich als kleine patch-reefs in einer Lagunen- bzw. Beckensituation in geschützter lage im Norden einer ausgedehnten Plattform mit karbonatischer Flachwasserfazies. DasRötelwand-Riff liegt vollständig isoliert innerhalb des Kössener Beckens, welches sich im Norden an die Dackstein-Plattform anschlie\t und durch kontinuierliche Absenkung eines Wattengebietes mit Hauptdolomit-Plattenkalk-Sedimentation in Norden hervorgegeangen war. Es ist allseitig von Kössener Beckensedimenten umgeben. Die Entwicklung der Rötelwand-Riffstruktur erfolgte aus dem Kössener Becken heraus in mehreren, deutlich voneinander unterscheidbaren Stadien. Die Entwicklung wird in erster Linie durch das Wechselspiel von Wasserenergie und Sedimentation gesteuert. Sie beginnt mit einem Tiefer-Wasser-Stadium mit zunächst rein mechanischer, dann mechanisch-biologischer Sedimentanhäufung und Ausbildung eines Karbonatschlammhügels (mud mound-Stadium). Hierauf folgt ein Flachwasser-Stadium mit der Ausbildung mächtiger Lumachellenbänke, welche die Basis für das Wachstum eines echten, ökologisch definierten Riffes bilden (Riff-Stadium). Durch lokale Sedimentanhäufung wächst die Riffstruktur kontinuierlich aus dem Bereich Schwächerer Strömungen am Grunde eines Beckens in eine Zone mit verstärkter Wasserbewegung hinein, so da\ sich zuletzt in einem Bereich mit Turbulenzen ein echtes Riffgerüst ausbilden kann. Eine vergleichbare Entwicklung aus Kössener Beckensedimenten heraus ist imAdneter Riffkomplex nicht zu beobachten. Die das Riff unmittelbar unterlagernden Sedimente sind nur in randlichen Teilen der Riffstruktur aufgeschlossen. Aus der abweichenden Ausbildung und räumlichen Verteilung der Sedimenttypen im basalen und in oberen Riff-Stadium und aus den Unterschieden im Aufbau des Riffgerüstes wird geschlossen, da\ sich der Adneter Riffkomplex auf einer Plattform mit Dachstein-Fazies (Algen-Foraminiferen-Detritus-Fazies) entwickelte. Die Plattform tauchte nach N und E allmählich ab, und die Flachwasser-Sedimente verzahnen sich in einer detritischen Übergangsfazies (MF-Typ III/C) mit den Kössener Beckensedimenten. Aufgrund der tektonischen Isolation der aufgeschlossenen obertriadischen Gesteine kann die Frage nicht beantwortet werden, ob die dem Riffkomplex unterlagernden und sich mit ihm lateral verzahnenden Flachwassersedimente des Sockels mit der ausgedehnten Dachstein-Plattform in Süden in Verbindung standen. Das Fehlen einer deutlichen, durch einheitliche Strömungsverhältnisse bedingten, horizontalen Zonierung der Fazies-Einheiten im Riffstadium der Entwicklung zeigt aber, da\ die Ausbildung der Adneter Riffstuktur sehr viel stärker durch die schützende Nähe der Dachstein-Plattform beeinflu\t wurde als diejenige der Rötelwand. Diefazielle Gliederung der beiden Riffstrukturen lä\t im Reifestadium ihrer Entwicklung 5 sich lateral miteinander verzahnende Fazies-Einheiten erkennen, die im Rötelwand-Riffkomplex eine deutliche Zonierung, im Adneter Riffkomplex dagegen eine zwar ebenfalls gesetzmä\ig angeordnete, aber eher fleckenhafte Verteilung aufweisen. Jede Fazies-Einheit entspricht einem Ablagerungsraum, welcher durch bestimmte mikrofazielle, biologische und sedimentologische Merkmale typisiert ist. Die übergeordnete Fazies-Einheiten können aufgrund des Vorherrschens einzelner Organismen und Sedimenttypen noch weiter differenziert werden, so da\ sich insgesamt15 Mikrofazies-Typen (MF-Typen) ergeben. Während die Gültigkeit der Fazies-Einheiten über einen regional und zeitlich gesteckten Rahmen hinaus geht und an keine Riffstruktur gebunden ist, nimmt ihre Untergliederung in Mikrofazies-Typen ausschließlich Bezug auf die beiden untersuchten Riffgebiete. 1. Die Biolithit-Fazies des zentralen Riffareales ist auf den Bereich der Riffknospen mit organisch gewachsenem Rifgerüst beschränkt. Dieses ist durch in-situ stehende Riffgerüstbildner und eine starke biogene Anlagerung gekennzeichnet. 2. Die onkoidische Riffdetritus-Fazies (Onkoid-Fazies) dringt mit parautochthonem Riffschutt zwischen den Riffknospen in den zentralen Riffbereich vor. Ihr Hauptbildungsraum liegt aber in exponierter Lage am oberen Riffhang in unmittelbarer Nähe zur Biolithit-Fazies. Im Rötelwand-Riff ist sie auf die Süd-Seite des Riffes beschränkt und zeight damit seine Luv-Seite und die isolierte position der Riffstruktur an. Im Adner-Riff sind die Riffknospen allseitig von der Onkoid-Fazies umgeben. Die Sedimente dieser Fazies entstehen unter hochenergetischen, flachmarinen Bedingungen. 3. Die Algen-Formainiferen-Detritus-Fazies entwickelt sich im Rötelwand-Riff im Süden aus der Onkoid-Fazies und leitet in die Kössener Beckenfazies über. Im Adneter Riffkomplex nimmt sie ein ausgedehntes Areal ein und stellt vermutlich das Fundament dar, auf welchem sich die Riffknospen entwickelten. Im Süden verzahnt sie sich mit den Onkoidkalken als zeitgleicher Ausbildung zur Biolithit-Fazies. Die Ablagerungen könen mit ähnlichen, in Subtidalen Bereich entstandenen Sedimenten der riffernen Dachsteinkalk-Fazies verqlichen werden. 4. Die Detritus-Schlamm-Fazies kennzeichnet den strömungsgeschützten Riffhang in unmittelbarer Nachbarschaft zur Biolithit-Fazies und verzahnt sich im Rötelwand-Riff allseitig mit der Kössener Becken-Fazies. Im Adnet-Riff besitzt die Fazies nur fleckenhafte Verbreitung im Norden des Gebietes. 5. Die Kössener Becken-Fazies weist eine Fülle verschiedener Faziestypen auf, deren Ausbilding und Verteilung in Bezug steht zum Relief des Meeresbodens. In nahezu allen Sedimenten (eine Ausnahme bilden die Ooidkalke) überwiegt der Anteil an Kalkschlamm. Die Fazies umgibt das Rötelwand-Riff allseitig und verzahnt sich im N und E mit den Adneter Riffkomplex. Daszentrale Riffgebiet des Rötelwand-Riffes bildet ein weites Areal mit lockerem, aber gesetzmä\ig angeordnetem Bestand von Riffbildnern. Es können nur wenige Riffknospen, von einander getrennt durch Riffschuttareale, unterschieden werden. Innerhalb der Riffknospen sind Teilbereiche durch das Vorherrschen bestimmter Assoziationen von Riffgerüstbildnern charakterisiert. ImAdneter Riffkomplex setzt sich das zentrale Riffareal aus zahlreichen Riffknospen zusammen, deren jede eine eigene Interngliederung erkennen lä\t. Im Zentrum der Struktur stehen sie derartig dicht nebenund aufeinander, da\ der reine Riffschutt zwischen ihnen vollständig fehlen kann. Korallen, Kalkschwämme (überwiegend Spinctozoen), Hydrozoen (Disjectoporen und Spongiomorphiden), Tabulozoen und Kalkalgen sind mit rund 60 Arten, darunter zahlreichen neuen Formen, an der Korstruktion des Riffgerüstes beteiligt. Während das Adnet-Riff als echtes Korallen-Riff bezeichnet werden kann, in welchem eine Art, die gro\kelchige Varietät vonTheocosmilia clathrata EMMRICH, dominiert und alle anderen Riffbildner nur eine sekundäre Rolle spielen, besitzen im Rötelwand-Riff Korallen und Sphinctozoen nahezu die gleiche Bedeutung bei der Besiedlung des zentralen Riffareales. Die Diversität der Rifforganismen des Rötelwand-Riffes übertrifft deutlich diejenige des Adneter Riffes. ImRötelwand-Riff überwiegen heterotypische Organismengemeinschaften. Im Adnet-Riff sind dagegen in allen grö\eren, stets polymikten Riffknospen auffallend häufig auch homotypische Riffgemeinschaften an ihrem Aufbau beteiligt. Fassen wir die wichtigstenRiff-Assoziationen in beiden Riffgebieten zusammen, so lassen sich insgesamt9 Vergesellschaftungen unterscheiden. Jede von ihnen ist charakterisiert: 1. durch die Assoziation der Riffgerüstbildner, 2. durch ihren Sekundärbewuchs von Epi- und Endobionten, 3. durch eine signifikante Foramineferen-Assoziation, und 4. durch einen speziellen Sedimenttyp (MF-Typ I/A bis D) als Füllsediment in den Zwischenräumen des Riffgerüstes. Die Anordnung der Riffknospen im zentralen Riffareal und ihre Interzonierung werden durch ökologische Faktoren gesteuert. Der Grad der Wasserenergie nimmt deutlichen Einflu\ auf die Verteilung der Rifforganismen und des Sedimentes. Das gesetzmä\ige Auftreten der Rifforganismen in bestimmten Arealen des Riffbereiches gibt Hinweise auf die physiologischökologischen Anforderungen welche die Organismen an ihren Lebensraum und an die Teilglieder ihrer Assoziationen stellen. Als sehr brauchbar haben sich die vagilbenthonischen Foraminiferen nicht nur zur Typisierung der übergeordeneten Fazies-Einheiten (d.h. Ablagerungsbereiche), sondern auch als begleitende Fauna einzelner Riff-Assoziationen erwlesen. Ihre quantitative Verteilung zeigt, da\ diese in stärkerem Ma\e von der Sedimentverteilung als von der Art der Riff-Assoziationen abhängig ist.

Upper Triassic reefs of the Oman Mountains: Data from the South Tethyan margin

Article

Dec 1996
FACIES

Michaela Bernecker

The Upper Triassic reefal limestones of the Oman Mountains were investigated with respect to their microfacies, palaeontology and community structure. The reef fauna described and figured for the first time occurs in parautochthonous slope deposits of the Arabian platform (Sumeini Group) and in allochthonous reefal blocks (‘Oman Exotics’, Hawasina Complex). The ‘Oman Exotics’ are tectonically dislocated blocks, derived from isolated carbonate platforms on seamounts in the Hawasina basin or in the South Tethys Sea. The lithofacies and fauna of these blocks comprise a cyclic platform facies with megalodonts, reef and reef debris facies. The reefal limestones are dated as Norian/Rhaetian by benthic foraminiferal associations (Costifera, Siculocosta, Galeanella) and typical encrusting organisms (Alpinophragmium, Microtubus). Some small ‘Oman Exotics’ are of Carnian age. The shallow-marine organisms include scleractinian corals of different growth forms, ‘sphinctozoans’, ‘inozoans’ chaetetids, spongiomorphids, disjectoporids and solenoporacean algae as the main reef builders, various encrusters like microbes, foraminifers, sponges and many different problematical organisms for the stabilisation of the reef framework and a group of dwellers including benthic foraminifers, gastropods, bivalves and a few dasycladacean algae. The reef communities are characterized by the coverage of organisms and distributional pattern. Analogies with the coeval reef deposits from the European part of the Tethys have been recognized. Some species, now collected in Oman, were also reported from American and Asian localities.

Microfacies, paleontology and palecology of the Dachstein Reef Limestones (Norian) of the Gosaukamm Range, Austria

Article

Jan 1982
FACIES

Detlef Wurm

Facies and paleoecology of two Upper Triassic reef-complexes of the northern calcareous alps (“upper Rhaetian” reef Limestones, Salzburg, Austria)

Article

Jan 1979
FACIES

Priska Schäfer

Sumeini group, Oman—evolution of a Mesozoic carbonate slope on a South Tethyan continental margin

Article

Jun 1986
SEDIMENT GEOL

Deposition of the mostly Mesozoic Sumeini Group occurred on the slope between the shallow-marine, Arabian carbonate platform and the deep-oceanic Hawasina Basin or South Tethys Sea. These strata record the evolution of the northeast Arabian continental margin from Permian(?) and Triassic rifting to ocean basin closing with the Late Cretaceous obduction of the Semail Ophiolite. Platform margin type and its evolution can be inferred from exposures of these slope sediments at Jebel Sumeini in the Western Oman Mountains.

Evolution of Triassic reefs: Current concepts and problems

Article

Dec 1982

Erik Flügel

The paper is concerned with some key questions resulting from current studies of Triassic reefs and reef biota. A survey of the distribution of the reefs in time and space (Figs. 1–2) indicates the existence of Anisian buildups (starting in the Pelsonian), and significantly restricted to the southern part of Europe. Ladinian and Carnian reefs exhibit a larger distribution pattern, including Europe, Asia and western North America as well as Peru. Even broader is the distribution of Norian and Rhaetian reefs, which are known from many parts of the Tethys but have been studied in detail only in Europe, Central Asia and in western North America, The exact age of many Triassic reefs is controversial because of the strong facies control of reef biota. The composition of the framebuilding fauna (especially calcisponges and corals) can only differentiate an Anisian to Carnian time interval from a Late Upper Triassic interval. The current state of research is characterized geographically by strongly biased information (more than 75 % of the Triassic reefs studied in more detail are situated in the Alpine-Mediterranean region and in the Cordilleran of western North America). Information about the composition of the framebuilding and binding communities as well as about facies types is generally good, but there is a strong need for more study of the reef-dwelling organisms and especially of the diagenetic history of reef carbonates. Triassic reefs exhibit five principal reef categories, which are distinguished by morphology and paleogeographical setting: 1. Carbonate ramps with biostromes, 2. Mud Mounds. 3. Reef Mounds, differentiated into knoll reefs and patch reefs. 4. Atolls. 5. Barrier Reef Complexes. Fig. 4 may be used to classify Triassic reefs with respect to morphology and paleogeographical location of the buildups. Most Triassic reefs described up to now are situated in a shelfedge position and in back-platform positions. Foreslope positions and platform margin settings were formed prior to platform and back-platform settings. The palecological interpretation of the reef biota is made more difficult by the rarity of systematic paleontological studies of many Triassic reefs. Difficulties arise even for the main reefbuilding groups: Calcisponges (only the European sphinctozoans have been studied in detail), corals (the problem of the beginning of coralzooxanthellae symbiosis should be clarified), and algal crusts as secondary framebuilders (without Recent counterpartsl). The relative importance of reefbuilders changes throughout time (Figs. 5–6); this is indicated by the different abundances of primary and secondary framebuilders, and also by different reef communities. Upper Triassic reefs seem to be characterized by at least six main communities, whereas Anisian to Carnian reefs exhibit eight communities. Only a few associations may be regarded as long-lived units. Reef communities reflect ecological successions characterizing various stages in the formation of organic buildups (stabilization, colonization, diversification, and domination). A general trend can be seen in the existence of a vertical sequence showing predominantly encrusting and low-diverse biota at the base of the reef formation, and more diverse but vertically zoned biota within the higher levels. Numerical and faunal diversity of reef biota indicate the existence of regular gradients over different parts of Triassic reef complexes. Diversity seems to be different in coeval reefs of different paleogeographical position (Fig. 7) and also changes over time (higher diversities during the Norian and Rhaetian). The provinces of Triassic framebuilders can be inferred only for Late Triassic reefs, and seem to be better expressed by non-coral associations (calcisponges, hydrozoans, tabulozoans) than by rather cosmopolitan coral faunas. The evolution of Triassic reefs seems to have been triggered by the co-operation of some major biological innovations, which include the development of binding organisms (necessary for the stabilization phase of reef formation); reinstatement of colony building and special growth types which were lost during the Upper Permian; increase of diversity of reefbuilders over time; rapid evolution of secondary framebuilders during the Norian and Rhaetian; and development of hermatypic corals during the Triassic. Die ältesten triadischen Riffe sind aus dem Anis (Pelson) bekannt; anisische Riffe sind bisher nur aus den Alpen und aus den Westkarpathen beschrieben worden. Ladinische und karnische Riffe besitzen eine weitaus größere Verbreitung (Europa, Asien, westliches Nordamerika, Peru); noch größer ist die Verbreitung norischer und rhätischer Riffe. Die biostratigraphische Einstufung vieler Riffe ist schwierig; die riffbildenden Organismen (insbesondere Kalkschwämme und Korallen sowie Mikroproblematika und auch Foraminiferen) gestatten nur die Trennung von Anis bis Karn und Nor-Rhät. Der gegenwärtige Untersuchungsstand ist durch eine Konzentration der Arbeiten Uber Trias-Riffe im alpin-mediterranen Raum und im westlichen Nordamerika gekennzeichnet. Die Information über die Zusammensetzung der gerüstbildenden und sedimentbindenden Faunen sowie über die Riffbildner-Assoziationen ist im allgemeinen gut; es fehlen jedoch neue Untersuchungen über die Riffbewohner. Das gleiche gilt für dringend notwendige Arbeiten über die diagenetische Entwicklung der Riffkarbonate. Die triadischen Riffe lassen sich fünf, durch Gestalt und paläogeographische Position unterschiedenen Riff-Typen zuordnen: 1. Biostrome auf Karbonatrampen. 2. Stillwasserbioherme (Mud Mounds). 3. Riffhügel-strukturen (Reff Mounds), differenziert in Knollenriffe (Knoll Reefs) und Fleckenriffe (Patch Reefs). 4. Atolle. 5. Barrier-Riffkomplexe. Fig. 4 bietet eine Möglichkeit, triadische Riffe im Hinblick auf die paläogeographische Lage und die Gestalt der Riffkörper zu klassifizieren. Die meisten bis jetzt beschriebenen Riffe entstanden in einer Schelfrandposition oder im Rücken ausgedehnter Plattformen (back-platform position). Am oberen Schelfhang und am Plattformrand gebildete Riffe treten früher (bereits im Ladin) auf als Plattformriffe und Riffe in Becken hinter der Plattform. Die palökologische Interpretation der Rifforganismen wird durch die Seltenheit von genauen paläontologischen untersuchungen vieler Riffe erschwert; auch bei den wichtigsten riffbildenden Gruppen treten ungeklärte Probleme auf: Kalkschwämme (bisher wurden nur die Sphinctozoen der europäischen Vorkommen genauer untersucht), Korallen (die Frage der Entstehung der Korallen-Zooxanthellen-Symbiose) und Algen-Krusten als sekundäre Gerüstbildner (keine rezenten Vergleichsmöglichkeiten!). Die relative Bedeutung der Riffbildner (Fig. 5–6) hat sich in der Zeit geändert; dies wird auch in den, in der Mehrzahl auf die Zeitbereiche Anis-Karn oder Nor-Rhät beschränkten “Riffbildner-Assoziationen” deutlich, die teilweise verschiedene Stadien der Riffentwicklung repräsentieren. Eine allgemeine, sowohl in der Mitteltrias als auch in der Obertrias erkennbare Entwicklungsrichtung ist dadurch gekennzeichnet, daß in der vertikalen Folge der Riffe ein durch inkrustierende und geringdiverse Organismen charakterisiertes Anfangsstadium durch höher diverse aber vertikal und lateral zonierte Assoziationen abgelöst wird. Bei Berücksichtigung der numerischen und der Faunen-Diversität der Riffbildner wird die Existenz von Diversitätsgradienten innerhalb der Riff-Komplexe deutlich. Innerhalb von gleichalten Riffen unterschiedlicher paläogeographischer Position (Fig. 7) scheinen Diversitätsunterschiede aufzutreten, desgleichen bei Riffen gleicher Position aber von unterschiedlichem Alter. Die Existenz von “Provinzen” innerhalb der triadischen riffbildenden Gruppen kann nur für die Zeit der oberen Trias vermutet werden; Kalkschwämme, Hydrozoen und Tabulozoen scheinen hier bessere Hinweise zu liefern als die weitgehend kosmopolitischen Korallen. Die Entwicklung der Trias-Riffe wurdeaußer durch großräumige paläogeographische Veränderungen während der Mitteltrias (Beginn des Rifting)—im wesentichen durch das Zusammenwirken eimger, von der Evolution der Rifforganismen abhängiger Neuerungen beeinflußt, zu denen die Entstehung von sedimentbindenden Assoziationen (erforderlich als Pioniergemeinschaften in der Stabilisierungsphase), die Wiederherstellung der im oberen Perm verlorenen Fähigkeit zur Ausbildung von Kolonien und von bestimmten Wuchsformen, die Zunahme der Diversität in der Zeit, die rasche Entwicklung der sekundären Gerüstbildner während des Nor und des Rhät, und schließlich die Entstehung von hermatypen Korallen gehören.

The Upper Triassic Pantokrator Limestone of Hydra (Greece): An example of a prograding reef complex

Article

Dec 1982

The Pantokrator Limestones from the Island of Hydra and the Didymi Mountains (southern Argolis, Greece) form a heterogenous complex up to 1000 m thick, with lateral and vertical interfingerings of different facies units (Fig. 3). Sedimentation in the Didymi Mountains (Fig. 1) was dominated by the deposition of lagoonal to tidal shallow-water platform limestones of Carnian to Liassic age. The vertical section of the Upper Triassic rocks exposed on Hydra (Fig. 2) shows a variety of facies units: Laminated cherty mud-limestones (“Hornsteinplattenkalke”) occur at the base of the complex and dominate the southern portion of the island. The thickness of the shallow-water carbonates (Pantokrator Limestones) increases towards the north. Sedimentation started with the deeper-water deposition of biodetrital mud-limestones, which are overlain by reef-limestones and finally by lagoonal to tidal carbonates. According to the faunal and floral associations, the laminated cherty mud-limestones and the biodetrital mud-limestones are thought to be of Carnian age, the reef limestones of Carnian/Norian age, and the loferites and lagoonal sediments of Norian/Rhaetian age. The biota of the reef-limestones on Hydra shows a vertical zonation (Fig. 4), which first starts with a coral-sponge-association followed by a sponge-(coral-) association and finally, a coral-association. This sequence is believed to have been caused by the continuous shallowing of the marginal platform and reef areas. The environmental analysis and interpretation of the facies units are based mainly on the occurrence and distribution of calcareous algae as well as their roles in carbonate production (Figs. 6–7). Reconstruction of the depositional environment was carried out by a study of the relationship between the facies units, indicating a basinward progradation of the platform margin towards the south (Fig. 5).

Mikrofazies, Paläontologie und Palökologie der Dachsteinriffkalke (Nor) des Gosaukammes, Österreich

Article

Dec 1982

Detlef Wurm

The paper deals with the microfacies and palecology of the Upper Triassic (Norian) Dachstein Reef Limestones of the Gosaukamm Range, situated about 60 km southeast of Salzburg, Austria. Additional studies are devoted to the coral-bearing Zlambach Beds adjacent to the western Gosaukamm. The Gosaukamm may be regarded as anexample of a continuous synsedimentary degradation of shelf margin areas with isolated reefs. More than 70% of the Dachstein limestone samples studied are bioclastic and lithoclastic rudstones and bioclastic grain/packstones composed of reworked and encrusted reef biota. Low-growing frame-building organisms (predominantly calcisponges) were responsible for the formation of primarily non-rigid frameworks situated at the margin or on protected parts of the foreslope. Stabilization of the reef framework was possible due to the very strong biogenous encrustation (mainly by algal crusts) and by a rapid submarine cementation. Destruction of the marginal reefs by hurricanes and mass flows was influenced by eustatic changes of sea level. Therefore, no clear distinction can be made with regard to various parts of a “reef-complex” (back-reef, central reef area, fore-reef) even though the bulk of the sediment can be compared with “fore-reef breccia”. TheDachstein Reef Limestones of the Gosaukamm Range are underlain by well-bedded micritic cherty limestones (Chapter 3) rich in radiolarians, filaments, planktonic crinoids, sponge spicula and pelecypods (Norian species ofMonotis). The upper part of this sequence is represented by high-diversity bioclastic grainstones showing inverse grading. The biota are characterized by coated echinoderms, shells, dasycladaceans and some recrystallized calcisponges, together with microproblematica (predominantlyTubiphytes) and foraminifera (“Sigmoilina”, Reophax, Galeanella, Endothyra, Trochammina); micritic lithoclasts with thin shells and withMuranella are rather common. These carbonates seem to represent platform carbonates (Fig. 25) redeposited within a basinal environment. The sequence is overlain by well-sorted micritic bioclastic limestones of the “fore-reef” facies. Theframe-building organisms of the Gosaukamm reef (Chapter 4.2) are represented by similar species as in other Upper Triassic reef limestones of the Northern Alps: Calcisponges (sphinctozoans common, inozoans rare), corals (relatively high-diversity but quantitatively subordinate as compared to calcisponges), “bryozoans” (Cyclostomata) and tabulozoans (probably sclerosponges), hydrozoans (spongiomorphids, disjectoporids,Lamellata; Heterastridium) and chaetetids. Calcareous algae are known by dasycladaceans (Diplopora, Heteroporella, Griphoporella) and solenoporaceans (Solenopora, Parachaetetes). Spongiostromate crusts are of major importance within the organic framework (see Fig. 7 and Plate 31). Foraminifera are abundant in the bioclastic grain/packstones and in bio- and lithoclastic rudstones (Fig. 8); the species and genera correspond to those known from other Upper Triassic reef limestones (see Chapter 4.3) but no distinct distributional patterns can be recognized because of large amounts of allochthonous sediments. The same holds true for most of the microproblematica (Chapter 4.4). Reef-dwelling organisms are represented by pelecypods, gastropods, rare small ammonoids, brachiopods, ostracods (especially in reef-cavities), crinoids, echinoids, serpulids and crustaceans (exclusively fecal pellets). Most of these groups can be found in all facies types. Themicrofacies types of the Dachstein reef limestones (Chapter 5) were defined by quantitative and semi-quantitative analyses of more than 1100 large thin-sections. Important criteria for the differentiation of the microfacies types are the amount of micrite, sparite, particles and porosity; packing, size and roundness of detrital particles; types of fossils; and encrustation sequences. 10 microfacies types can be separated: (Chapter 5.2); this rather broad spectrum reflects the existence of very well diversified platform and reef environments which were simultaneously reworked by storms and by mass transport at the edge of the platform. Thediagenesis of the Dachstein reef limestones (Chapter 6) is characterized by submarine and vadose cementation. Submarine cements are represented by fibrous and also radiaxial cements (see Plate 40); vadose diagenesis is indicated by crystal silt occurring in all microfacies types but most abundant within the bioclastic grain/packstones (microfacies 2), rud/floatstones (microfacies 1), and boundstones (microfacies 6), see Figs. 16 and 22. Most Dachstein reef limestones exhibit a high interparticle and framework porosity which is generally much reduced by early diagenetic cementation (see Fig. 23). Secondary porosity is represented by irregular vugs and fissures filled with vadose silt. Theinterpretation of the biota and the microfacies (Chapter 7) points to the existence of agitated, shallow environments. Because of the lack of high-growing frame-builders only small and rather scattered reef structures seem to have grown at the platform margin. Indicators of platform environments are: high-diveristy shallow-marine biota (microfacies 6), predominance of “reef breccia” and bioclastic detritus (microfacies 1 and 2), abundance of coated grains (microfacies 4), aggregate grains (microfacies 9), multiple resedimentation (within almost all microfacies types), and vadose diagenesis. Structural and textural data (grain-size distribution, sorting, roundness, energy-index) verify this interpretation. Thefacies model (Chapter 8) postulates the existence of a differentiated platform margin which is continuously eroded by wave energy and storms; the allochthonous material is deposited on the foreslope and in different parts of the platform. Small reefs are built in protected parts of the slope and the margin by calcisponges, algal crusts and various epizoans, in conjunction with a rapid submarine cementation. The biota and facies types are similar to other Upper Triassic reefs but the facies model of the Gosaukamm (Fig. 25) exhibits distinct differences caused by a stronger influence of eustatic sea level fluctations. Themicrofacies of the Zlambach Limestones (Chapter 9) is characterized by coral bafflestones; bioclastic packstones with densely packed corals, solenoporaceans, pelecypod shells, echinids and foraminifera; medium-grained pack/grainstone with micritic lithoclasts and echinoderms or with coated grains; graded, densely packed bioclastic packstones with broken corals, tabulozoans, crinoids, and foraminifera; bioclastic wackestones with echinoderms; and burrowed wacke/packstones with sponge spicula. Theenvironment of the Zlambach Beds adjacent to the Dachstein Reef Limestones of the Gosaukamm (Chapter 9.5, Fig. 32) can be interpreted as morphologically differentiated shallow-marine areas with shoals (coral bafflestones) and depressions (allochthonous carbonates). Shallowing-up sequences might have developed (indicated by vadose silt). In comparison to the Dachstein reef limestones of the Gosaukamm, there are distinct differences in the microfacies types, the importance of the corals, and in the encrustation sequences: these factors indicate a depositional environment of the Zlambach Beds which was not primarily influenced by the development of the Dachstein platform.

The Cassian patch reefs (Lower Carnian, Southern Alps)

Article

Jan 1982

Jobst Wendt

The fauna of the upper Cassian Formation is composed mainly of reef-building and reef-dwelling organisms which occur as reeeposited material in basinal sediments, but have not been found as original reef bodies. Such bodies have now been discovered in the uppermost Cassian Formation of the central Dolomites from the Sella Group in the west to the Monti Cadini in the east. Generally they are small-scale patch reefs, not exceeding a few metres in thickness and lateral extent, which are intercalated in well-bedded detrital and micritic limestones. locally, larger biostromes spread out from the margins of the Cassian Dolomite buildups. Four types of faunal communities have been encountered in these reefs:1. The thrombolite-calcareous algae community, composed of small patchy cryptalgal structures binding poorly sorted debris and associated with other Cyanophyta, sessile formainifera and scattered calcareous sponges and corals. This type is the most common within the calcareous and marly-tuffaceous facies of the Cassian Formation. 2. The calcareous sponge-coral community, composed mostly of calcareous sponges (stromatoporoids, some pharetronids) and, to a lesser extent, colonial corals and thrombolites. This community corre-sponds well to the Cassian reef fauna, best known from erratic blocks at Alpe di Specie, but has been found in situ only at one locality. 3. The Spongiomorpha-Solenopora community, associated with scattered calcareous sponges and colonial corals, forming a thin biostrome at one locality. 4. Coral communities, composed predominantly of colonial Scleractinia; found only in small or stratigraphically illdefined outcrops and in erratic blocks. The Cassian patch reefs and biostromes mark the end of a basinal evolution which began in the Lower Ladinian, and the onset of newly expanding carbonate buildups of Cassian Dolomite. These buildups and the sponge-coral patch reefs might have been the source for the allochthonous reef fauna of the Cassian Formation which interfingers with both shallow water environments.

Combined quantitative analysis and microfacies studies of ancient reefs: An integrated approach to Upper Permian and Upper Triassic reef carbonates (Sultanate of Oman)

Article

Dec 1993

The internal architecture of Upper Permian calcisponge reefs, Upper Triassic coral thickets, and Upper Triassic coral reef communities of the Oman Mountains have been investigated. In order to gain comparable data sets, investigations were carried out at different scales comprising quantitative data from outcrops and descriptions from thin-sections. Methods of quantitative outcrop investigations were modified with reference to standard investigation techniques used in the study of communities of modern reefs. Data evaluation comprises mapping of reef fabric in natural scale on plastic sheets in the field. Data calculation was carried out utilizing the digitized image analysis system Vidas. Measurement parameter are the total detrital framework coverage, coverage of reefbuilder taxa, mean diameter of taxa, and mean distance. In addition, measured plastic sheets were printed for paleoecological interpretation. Thin-section analysis reveal microfacies types, sedimentological criteria and taxonomic inventory of reef organisms. Based on quantitative field data five Upper Permian and four Upper Triassic communities were differentiated. Late Permian communities are represented by a: (1) Low-diverse sphinctozoan community, (2)Radiotrabeculopora Archaeolithoporella community, (3) Cerioid coral community, (4) Solitary coral community, and (5) Waagenophyllid coral community. Upper Triassic communities comprise: (1) Diverse coral community, (2) CoralSpongiostromata community, (3) Solenoporacean dendroid coral community, and (4) Crinoid community. The synthesis of both quantitative field data (plot technique with quadrats as sampling units) and the study of thinsections (microfacies analysis, taxonomy) is believed to result in data sets which could be used in comparative reef research with a higher degree of reliability than up to now.

Faziesentwicklung in proximalen Intraplattform-Becken: Sedimentation, Palökologie und Geochemie der Kössener Schichten (Ober-Trias, Nördliche Kalkalpen)

Article

Dec 1983

Hans-Joachim Kuss

Microfacies studies of the carbonates of the Kössen Beds (Salzburg-Tyrol, Austria) show that the deposition took place within a protectedintraplatform basin. Three facies units can be differentiated within the profiles: I Marl Carbonate sequence; II Coral Limestones; III Carbonate Marl Bed sequence. A diachronous development of 14 microfacies types and also of the facies units (alternating within one profile) becomes evident when the sections are compared; facies unit III indicates a subsidence of the basin. The seven microfacies types of theMarl Carbonate sequence (I) represent shallow water carbonates, formed in protected areas or surf zones. Episodic higher-energy events together with differences in the salinity can be inferred from the distribution of the organisms and the facies types: Laminated Algal Bindstone (I/1), Pelmicrite (I/2), Mudstone (I/3), Lumachelle facies (I/4), Bioclastic Grainstone (I/5), Onkoid facies (I/6), Oolitic Grainstone (I/7). Two genetic types occur within theCoral Limestone facies unit II: The“Shallow Coral Limestone” was formed in agitated water; flora and fauna are reminiscent of those in the Rhaetian reefs and the Dachstein Reef Limestones. The“Deeper-Marine Coral Limestone” was formed below the photic zone, but still within the influence of episodic storms. Five microfacies types are developed, sometimes only in the outcrops: Reefdetritus-Mud facies (II/1), Biostromal facies (II/2), Mud Mound Facies (II/3). Coated Grain Facies (II/4), Formaminiferal grainstones (II/5)—the latter occurs in the “Shallow Coral Limestones” only. Monotonous Carbonate/Marl intercalations consisting of the Echinoderm-Detritus-Mud facies (III/1) and the Detritus-Mud facies (III/2) characterizefacies unit III. Low-diversity fauna and high-diversity trace fossils point to a deposition in greater depths. The presence ofChoristoceras marshi indicates, this sequence is of Rhaetian age. Corals, echinoderms, foraminifera and microproblematika are common within the shallow-marine carbonates; sponges, hydrozoans and algae are rare; in contrast to the Rhaetian reefs, the flora and fauna are of rather low-diversity. Brachiopods, mollusks, ophiurids and ammonites are important for facies and stratigraphic interpretations. Of special interest is the distribution of the benthic foraminifera: Facies-controlled associations can be recognized.Agathammina austroalpina, Glomospira sp. and thin-walled nodosariids adapted to high salinity.Agathammina austroalpina is the only foraminiferal species, found within the tempestites formed by coquinas.Aulotortus gaschei is a typical species of the oncoid carbonates, it is the only foraminifera within the oolitic grainstones. Involutinids and textulariids are missing within facies unit III;Tetrataxis, Planiinvoluta and small miliolid foraminifera were adapted to this deeper water environment. The “Shallow-water Coral Limestones” are characterized by highly diverse involutinids. The foraminiferal distribution within the “Deeper Coral Limestones” shows a maximum of individuals and species within the Mud Mound Facies. The lowest number of individuals occurs within the Coated Grain Facies. The deposition of the “Shallow-water Coral Limestones” was influenced by episoidc storm events, as shown by densely packed shell (or coral) layers. The thickness of these tempestites depends on sedimentation energy. Sea level fluctuations, which caused the “Deeper Coral Limestones” to stop developing are indicated by vadose/marine and vadose leaching and cementation processes, probably due to temporary subaerial exposure (perhaps connected with early Cimmerian epeirogenetic movements). Blocky cements were formed under freshwater/phreatic conditions, as confirmed by Mn-enrichment and Sr-depletion of these cements. The distribution of trace elements (Fe, Mn, Mg, Sr) and insoluble residues was interpreted with the help of cluster analysis and factor analysis. The variability of the parameters is due to the primary mineralogical composition and diagenetic alterations (R-technique); water energy and micrite content are restrictive factors, as shown by the Q-technique. Sr and Mn distributions within the different profiles exhibit different patterns: different diagenetic stages are reflected by Sr values. The different intensities of the freshwater/phreatic diagenesis are expressed by different Mn values.

Response of Triassic reef coral communities to sea-level fluctuations, storms and sedimentation: Evidence from a spectacular outcrop (Adnet, Austria)

Article

Dec 1999

The Upper Rhaetian coral limestone of Adnet, southeast of Salzburg Austria has been repeatedly referred to as one of the most spectacular examples of an ancient ‘autochthonous’ coral reef structure. The ‘Tropfbruch’ quarry is probably the best outcrop for interpreting the distributional patterns of biotic successions and communities of a late Triassic patch reef. Our study is based on the interpretation of a) outcrop photographs, b) reef maps resulting from quadrat transects, and c) the analysis of quantitative data describing the distribution and frequency of reef organisms and sediment. A new methodological approach (combination of reef mapping and photo-transects) is used to obtain quantitative field data which can be compared in greater detail with data from modern coral reefs investigated by corresponding quantitative surveys. Three unconformities and three well-defined ‘reef growth stages’ reflecting the vertical and lateral development of the reef structure were differrentiated using transects: Stage 1, representing the reef growth optimum, is characterized by laterally differentiated coral reef knobs with corals in growth position. Criteria supporting this interpretation are the extraordinary size of the corals, their preservation in situ and the great thickness of this interval. The massive coralPamiroseris grew under higher energy conditions at the rim of the reef knob, whereas branchingRetiophyllia colonies preferred less agitated water in the center. Vertical changes are reflected by an increase in frequency of the dasycladacean algaDiplopora adnetensis and by the decreasing size ofRetiophyllia. These sedimentological and biological criteria together with the unconformity above indicate a fall in the sea level as a major control mechanism. Stage 2, separated from stage 1 by an unconformity caused by partial subaerial exposure and karstification, is characterized by vertically stacked coral successions with diverse reef debris. Facies heterogeneity is reflected by differences in the diversity, taphonomy and packing density of reef-building organisms as well as by differences in sediment input from the platform. Water depths and accommodation space were lower, therefore minor sea level fluctuations had a stronger effect on the biotic composition. The high percentage of coral debris and corals reworked by storms and the increase in the input of platform sediment led to a reduction of reef growth. Stage 3, again separated at the base by an unconformity associated with karstification, is characterized by bioclastic sediments with isolated reefbuilders forming a level-bottom community. The distribution of different coral morphotypes suggests that sea level fluctuations were not the only controlling factor. Variations in the substrate were caused by differences in the input of platform sediment. The three-step development seen in Adnet documents the response of low-diverse coral associations to variations caused by small-scale sea level changes, storm activity and sedimentation. The vertical changes in reef community structures correspond to a sequence of ‘allogenic replacements’. The Adnet reef structure should not be regarded as a general model of Alpine Upper Rhaetian reefs, because of the particular setting of the patch reef. Only the ‘capping beds’ of the Upper Rhaetian Reef Limestone of the Steinplatte exhibit criteria similar to Adnet. Potential modern analogues of features seen in the coral communities of Adnet are the internal structure of theRetiophyllia thickets, the key role of branching corals within the communities, the scattered distribution and low and even diversity of corals subsequent to breaks in settlement, segration patterns of corals indicating ‘contact avoidance’, toppling of large coral colonies by intensive boring, and decreasing coral coverage from deeper and sheltered settings to more shallower water depths.

Obertriadische Riffe und Rifforganismen in Sizilien (Beiträge zur Paläontologie und Mikrofazies obertriadischer Riffe im alpin-mediterranen Raum, 27)

Article

Dec 1982

In Nordwest- und Zentralsizilien (Panormide-Gebirge westlich Palermo; Madonie-Gebirge) sind am Rand ausgedehnter Karbonatplattformen obertriadische Riffe entwickelt, deren norisches Alter durch Heterastridien und Ammoniten belegt ist. Es handelt sich um Schwamm-Bryozoen-Riffe, deren Faunen- und Florenbestand weitgehende Übereinstimmung mit etwa gleich alten Riffen in den Nördlichen Kalkalpen (Dachsteinkalkriffe) besitzt. Es sind folgende Organismengruppen vertreten (Die im Rahmen dieser Arbeit als Bryozoen bezeichneten Organismen stellen höchstwahrscheinlich keine Bryozone dar. Alle diese Organismen sind vermutlich zu den Chaetetiden oder Sclerospongien zu stellen): lien und Astraeomorphen); 3. Hydrozoen (selten bis auf Disjectoporiden); 4. Bryozoen/Tabulozoen (häufig und hochdivers; bei Chaetetiden-ähnlichen Fossilien dürfte es sich um Sclerospongien handeln); 5. Algen (überwiegend an den Lagunenbereich und an den Übergangsbereich Lagune/Riff gebunden; es treten Dasycladaceen, Solenoporaceen sowie porostromate und spongiostromate Cyanophyceen auf; von Interesse ist das Vorkommen von Dasycladaceen-Sporen (Taf. 23/11)); 6. Foraminiferen (im Artenbestand mit den Foraminiferen-Assoziationen der nordalpinen Obertrias übereinstimmend; hierzu tretenFoliotortus PILLER & SENOWBARI-DARYAN sowie vasenförmige Gehäuse, die unter den NamenCucurbita, Amphorella etc. bisher nur aus der Obertrias der Westkarpaten sowie von der Hohen Wand bei Wien bekannt (wurden); 7. Problematika (ähnlich wie in der Riff-Fazies der alpinen Obertrias). Am Cozzo di Lupo, W Palermo können die Faziestypen des Riffes und der Lagune lateral verfolgt werden: An eine durch Schwamm-Bryozoen-Biolithite mit zahlreichen, zementerfüllten Hohlräumen gekennzeichnete Zone schließt sich eine durch Korallen (Thecosmilien), Algen (Dasycladaceen, Solenoporaceen, Cayeuxien), Gastropoden und Megalodonten charakterisierte Zone an (Korallen-Algen-Biolithit), in welcher sich Bänke mit Korallen und Bänke mit Megalodonten vertikal ablösen. Vereinzelt treten kleine Riffknospen auf, deren Fazies derjenigen der Schwamm-Bryozoen-Biolithite entspricht. Die Korallen-Algen-Biolithit-zone geht in eine zone mit Stromatolithen und Fenstergefügen über (Loferit-Fazies). Die Verteilung der Organismen innerhalb der Faziesbereiche kann mit ähnlichen Assoziationen in der nordalpinen Obertrias verglichen werden (Abb. 3): 1. Korallen sind jedoch im Gegensatz zu vielen alpinen Riffen in der Schwamm-Bryozoen-Biolithit-Fazies als Gerüstbildner nur von geringer Bedeutung. Thecosmilien treten insbesondere im Übergangsbereich zwischen Riff und Lagune sowie in der Lagune auf, wo sie Biostrome bilden.—2. Kalkschwämme, Hydrozoen, sowie Bryozoen/Tabulozoen waren auf geringenergetische, tiefere Wasserbereiche beschränkt. Epi- und Endofauna dieser Assoziationen entspricht der von Kalkschwamm-Biozönosen aus der nordalpinen Obertrias.—3. Algen zeigen stark differenzierte Verbreitungsmuster; Spongiostromen sind auf die Schwamm-Bryozoen-Biolithit-Fazies beschränkt, Cayeuxien finden sich in der Lagune zusammen mit Thecosmilien und Megalodonten. Ebenfalls in der Lagune sind Dasycladaceen (insbesondereHeteroporella undDiplopora) weit verbreitet. Solenoporaceen sind vor allem in der Riff-Fazies sehr häufig.—4. Foraminiferen sind mitGaleanella, Ophthalmidium und “Lituosepta” auf die Schwamm-Bryozoen-Biolithit-Fazies beschränkt, während eine zweite, durchAlpinophragmium, Aulotortue, Glomospira und andere Gattungen gekennzeichnete Gruppe in der Korallen-Algen-Biolithit-Fazies der Lagune auftritt. In Riffhöhlen der Schwamm-Bryozoen-Biolithit-Fazies finden sich als wichtige FaziesindikatorenFoliotortus, Cucurbita und ähnliche Mikrofossilien, die wahrscheinlich als Foraminiferen anzusehen sind.—5. Auch die Mikroproblematika weisen bestimmte Verteilungen auf (Microtubus, Radiomura, Baccanella in der Schwamm-Bryozoen-Biolithit-Fazies;Bacinella, Thaumatoporella, Aeolisaccus undTubiphytes häufig in der Lagunenfazies). Der Ablagerungsraum des Cozzo di Lupo-Riffes (Abb. 4) ist durch eine, in etwas tieferem Wasser liegende Riffzone (Schwamm-Bryozoen-Biolithit-Fazies) gekennzeichnet, an welche sich in Richtung zur Lagune eine relativ hochenergetische Übergangszone anschloß. In der gut durchlichteten, flachen Lagune entstanden Korallen-Siedlungen, Dasycladaceen-Rasen und Megalodonten-Bänke. In geschützten, lagunären Bereichen konnten durch Schwämme und Bryozoen/Tabulozoen kleine Riffknospen gebildet werden. Die Lagune dürfte sich gegen Norden und Nordosten verflacht haben (angedeutet durch Stromatolithen, Fenstergefüge, geringe Diversität). Grundsätzlich ergeben sich auffallende Ähnlichkeiten mit dem Faziesmodell der Steinplatte (PILLER & LOBITZER 1979). Upper Triassic reefs were built at the margins of carbonate platforms in north-western and central Sicily (Panormide Mountains west of Palermo; Madonie Mountains). The Norian age of these reefs is evidenced by ammonites and the occurrence ofHeterastridium. The reefs are represented by Sponge-Bryozoan reefs; fauna and flora are very similar to those of Upper Triassic reefs of the Northern Calcareous Alps (Dachsteinkalk reefs). The biota consists of: 1. Calcisponges (especially sphinctozoans; more than 30 species); 2. Corals (of minor importance, low-diverse, predominantlyThecosmilia andAstraeomorpha); 3. Hydrozoans (rare, except disjectoporids): 4. Bryozoans/Tabulozoans (abundant, high-diverse; some chaetetid-like fossils may represent sclerosponges); 5. Algae (common within the transition area between the reef and the lagoon and in the lagoon; dasycladaceans, solenoporaceans as well as porostromate and spongiostromate cyanophyceans occur; of special interest is the occurrence of dasycladacean spores (P1. 23/11); 6. Foraminifera (the same species as in the Alpine Upper Triassic; in additionFoliotortus PILLER & SENOWBARI-DARYAN and amphora-like tests (Cucurbita, Amphorella etc., until now only known from the Upper Triassic of the Western Carpathians and from the Hohe Wand near Vienna, Austria); 7. Problematica (similar to the species found in Alpine reef limestones). A lateral transition of the facies types can be followed at the Cozzo di Lupo, west of Palermo: (1) Sponge-Bryozoan Biolithite-zone (central reef area) characterized by low-growing framebuilders and abundant cement infillings in cavities; (2) Coral-Algal Biolithite-zone (lagoon) withThecosmilia, algae (dasycladaceans, solenoporaceans,Cayeuxia), gastropods and megalodontid pelecypods; some small reef patches (similar in facies with the sponge-bryozoan-biolithite facies) may occur within this zone; (3) Loferite zone (lagoontidal flat) with stromatolites and fenestral fabrics. The distributional patterns of the fossils within the facies units can be compared with those of the reefs in the Northern Calcareous Alps (Fig. 3): 1. Corals are of minor importance within the spongebryozoan facies, but occur predominantly in the transitional area between the reef and the lagoon, and within the lagoon (biostromes withThecosmilia).—2. Calcisponges, hydrozoans and bryozoans/tabulozoans were restricted to somewhat deeper, low-energy environments. Epi- and endofauna of these associations are similar to those of calcisponge biocoenoses of the Alpine Upper Triassic.—3. Algae exhibit strongly differentiated distributional patterns: Spongiostromate algae and solenoporaceans occur predominantly within the sponge-bryozoan biolithite. The lagoonal environment is characterized byCayeuxia (together withThecosmilia and with megalodontid pelecypods) and dasycladaceans (Heteroporella, Diplopora).—4. Foraminifera are useful facies fossils: The association withGaleanella, Ophthalmidium and “Lituosepta” is restricted to the sponge-bryozoan biolithite facies, whereas the association withAlpinophragmium, Aulotortus, Glomospira and other genera occurs in the coral-algal biolithite facies. A third association, characterized byFoliotortus, Cucurbita and similar microfossils, is typical of biotopes within reef cavities.—5. Microproblematica show special distributional pattens:Microtubus, Radiomura, andBaccanella in the sponge-bryozoan biolithite facies;Bacinella, Thaumatoporella, Aeolisaccus andTubiphytes in the lagoonal facies. The environment of the Cozzo di Lupo reef complex (Fig. 4) is characterized by a reef zone, which developed in a slightly deeper area (sponge-bryozoan biolithite facies), bordered by a moderate to high-energetic transitional zone. The shallow, well-lighted lagoon was characterized by coral biostromes, dasycladaceans and megalodontids flourishing on the mud bottoms. Small reef patches were formed by calcisponges and bryozoans/tabulozoans in more protected areas of the lagoon. A shallowing of the lagoon might have occurred to the north and northeast, as indicated by stromatolites, fenestral fabrics and a generally low-diversity. The facies model of the Cozzo di Lupo reef is similar in many respects to that of the Upper Rhaetian Steinplatte reef near Waidring, Austria (PILLER & LOBITZER 1979).

Palecology of Upper Triassic Reefs in the Northern Calcareous Alps: reef communities

Article

Dec 1987

The community is the standard unit of analysis in ecology because through it both physical and biological aspects of the ecosystem can be determined. It offers the same potential in paleoecology. The communities of the upper Triassic reefs are analyzed from the literature and our own field work in order to determine their characteristics and to assess their usefulness. Six communities are recognized on the basis of R-mode cluster analysis of the do minant frame-builders in Rötelwand reef and from descriptions and our observations in other reefs. TheThecosmilia or High-growing coral, the Hydrozoan-tabulozoan and the Sponge communities are most widespread. The High-growingAstraemorpha, Low-growing coral andSolenopora communities are less common. Each community is characterized by a few dominant taxa and a larger number of associated taxa. The fidelity of the dominant taxa to their community is generally high; the fidelity of many of the associated taxa are typically lower and these taxa occur in a number of communities. Consequently, there is considerable overlap in composition between stands of different communities. In addition, the communities typically occur in patches only a few meters in diameter, and particularly in the Hydrozoan-tabulozoan community, the composition may differ considerably between adjacent patches. Differences in diversity between the communities are explained in several ways. Parameter of the physical environment can be correlated with diversity. Competition between members of the community probably had a strong effect on community composition and diversity. Different geologic longevity of the communities, which may have led to differences in community evolution and niche structure does not seem to be an important factor. Succession is poorly documented in these reef communities, either in encrustation sequences or in the development of individual reef patches. Community replacement, well developed only at Rötelwand, is assumed to reflect variations in water depth. The communities within several reefs are not sharply delimited geographically but have broad and overlapping distributions. The reef patches were widely and apparently randomly scattered in the reef tract, reflecting a generally uniform environment there. The depositional surface was not deeper than perhaps 10 m. The constraints on water depth are that it was shallow enough for the depositional surface to be within the photic zone for the growth of abundant algae, and above wave base for the production and multiple reworking of biogenic debris, but deep enough for a uniform environment with low gradients to be maintained across the reef tract. The reef patches did not have the capability to build up to sea level nor to construct a platform-edge reef dividing sharply reef and fore-reef tracts. The dominant organisms in the reef patches did not have the ability to construct wave-resistant framework. Consequently, these reefs do not fit the definition of ecologic reefs but do correspond to stratigraphic reefs.

Supersequence and composite sequence carbonate platform growth: Permian and Triassic outcrop data of the Arabian platform and Neo-Tethys

Article

May 2003
SEDIMENT GEOL

Permian and Triassic carbonate platforms of the Arabian Peninsula (Gondwana) and seamounts of the Neo-Tethys (Hawasina and Batain basins) are characterized by distinctive supersequences (second order, duration 5–20 million years, my) and composite sequences (third order, duration 0.5–5 my). The presented sequence stratigraphic framework will be compared with existing sea level curves to discuss the validity of different regional oscillations during the dispersal of Pangea.The carbonate succession of the Haushi and Akhdar Groups of the Arabian platform is composed of four Permian (P1–P4) and four Triassic supersequences (Tr1–Tr4). Isolated platforms of the Hawasina and Batain basins comprise two Permian supersequences and one Triassic supersequence. In contrast to the continuous development of the Arabian shield, carbonate platform growth of the seamounts was restricted to the Guadalupian–Lopingian and to the Middle–Upper Triassic, and ceased after drowning events.Composite sequences exhibit a well-developed stacking pattern during the Guadalupian–Lopingian (Saiq Formation). Lowstand systems tracts (LSTs) occur during the Cisuralian (Gharif Formation, Haushi Group) and Triassic (Mahil Formation, Akhdar Group). Open-marine depositional environments prevail during transgressive systems tracts (TSTs) with diverse biota including rugose and scleractinian corals, chaetetids, bryozoans, and crinoids. Highstand system tracts (HSTs) exhibit a twofold pattern: During the transgressive phase of supersequences, composite sequence highstands are dominated by reef or level-bottom communities with corals. Cyclic platform deposits or monotonous mud- and wackestone accumulated during the turnaround or late second-order highstand of a supersequence.Correlation of maximum flooding surfaces with published data suggests that supersequences P1, P2, and Tr4 can be traced across the Arabian platform into the Neo-Tethys basins, while supersequences P3, P4, and Tr1–Tr3 resulted from local tectonic events at the margin of the Arabian platform (Hulw half-graben). The presented sea level curve corresponds therefore to the Tethyan sea level curve during the Cisuralian and Guadalupian, but differs significantly during the Lopingian, as a result of the dispersal of Pangea. The Middle and Upper Triassic sea level curve from Oman is again in good correlation with published data. The Permian and Triassic sequence architecture on the Arabian plate and adjacent Neo-Tethys was predominantly triggered by the global warming after the Permian–Carboniferous glaciation, the initial rifting of Neo-Tethys, and subordinately by eustatic sea level changes.

Les blocs exotiques du Sultanat d'Oman: évolution paléogéographique d'une marge passive flexurale

Article

Jan 1993

Alain Pillevuit

At head of title: Université de Lausanne. Faculté des sciences. Institut de géologie et de paléontologie. Thesis (Ph. D.)--Université de Lausanne. Includes bibliographical references (p. 235-244) and index. Text in French; summary in English and French.

Upper Triassic reefs and reef communities of Iran Global and regional controls on biogenic sedimentation

Senowbari
Daryan
J Reitner
F Neuweiler
Gunkel

Triassic reefs of the Tethys In: Stanley GD (ed) The history and sedimentology of ancient reef systems

E Flügel
Senowbari
Daryan

Becken und Riffe der alpinen Obertrias: Lithostratigraphie und Biofazies der Kössener Formation Exkursionen im Jungpaläozoikum und Mesozoikum von Österreich

Golebiowski

Late Triassic reefs from the Northwest and South Tethys: Distribution, setting, and biotic composition

Abstract and Figures

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