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Proposed paleogeographic reconstruction of the Late Ordovician showing a continuous subduction zone along the Laurentian and Siberian Platform margins.
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Ordovician K-bentonite beds have a long history of investigation all around the world. They have been reported from Gondwana, the Argentine Precordillera, the Yangtze Platform, Laurentia, Baltica, and numerous terrains between Gondwana and Baltica, which now constitute a part of Europe. In recent years several K-bentonite beds have also been discov...
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... K-bentonite beds from the Upper Ordovician Mangazea Formation of the southwestern part of the Tungus basin in Siberia seem to be derived from the alteration of volcanic ash falls. Their appearance points to the intensive explosive volcanism on or near the western (in present-day orientation) margin of the Siberian craton in Late Ordovician time (Fig. 4). The timing of volcanism in the Ordovician of Siberia is surprisingly close to the period of volcanic activity of the Taconic arc near the eastern margin of Laurentia. It looks like both arcs were activated by the same plate tectonic reorganization. Similar to the situation in North America, the Upper Ordovician K-bentonite beds in ...
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... During the Ordovician Period, a series of important biological and tectonic events and environmental perturbations occurred on Earth (Fig. 1), including the Great Ordovician Biodiversification Event (GOBE; Webby et al., 2004;Harper, 2006;Servais et al., 2010;Servais and Harper, 2018) and the Late Ordovician Mass Extinction (LOME; Sheehan, 2001;Harper et al., 2014), as well as sea-level changes (Haq and Schutter, 2008), multiple volcanisms (Huff et al., 1992(Huff et al., , 2014Su et al., 2009), continuous cooling and Hirnantian glaciation (Saltzman and Young, 2005;Ghienne et al., 2007;Trotter et al., 2008;Finnegan et al., 2011), and Caledonian Orogeny (Mckerrow et al., 2000). South China is one of the most important regions for studying Ordovician geology because of its well-developed and widely distributed strata, abundant fossils of different ecological types (including benthic, nektonic, and planktonic), diverse sedimentary types, and obvious paleogeographical differentiation. ...
... Regional compilations provide the most comprehensive documentation of Ordovician tephra distributions (e.g. Kolata et al. 1996;Huff et al. 1998Huff et al. , 2014Astini et al. 2007;Su et al. 2009;Kiipli et al. 2015). ...
... . Goldman et al. (2020) recently summarized advances in geochronologic refinement of the Ordovician time scale from CA-ID-TIMS U-Pb zircon analysis. The new Ordovician ages include three from the Tremadocian (Normore et al. 2018), four ages each in the Floian and Dapingian (Thompson et al. 2012; Normore et al. 2018), 12 ages in the Darriwilian (Sell et al. 2011; Leslie et al. 2012; Lindskog et al. 2017; Macdonald et al. 2017; Liao et al. 2020), 18 ages in the Sandbian(Sell et al. 2013;Svensen et al. 2015;Oruche et al. 2018;Ballo et al. 2019;Metzger et al. 2020), eight ages in the Katian(Huff et al. 2014;Macdonald et al. 2017;Ling et al. 2019) and one age in the Hirnantian(Ling et al. 2019). ...
The study of Ordovician tephras yields a wealth of valuable information about regional tectonism, sedimentation, stratigraphic correlation, and process rates. As such, these layers are prized by geologists and are the subject of a rich literature. Ordovician tephra studies were pioneering, particularly in development of chemical fingerprinting, to improve precision in tephrochronology. Modern radioisotope geochronology utilizes zircons and other phenocrysts from these layers to generate eruption ages with uncertainty on the order of a hundred thousand years. When integrated with biostratigraphy, chemostratigraphy and astrochronology, tephra ages provide unparalleled opportunity to constrain process rates. Fifty such Ordovician tephra ages have been published over the last decade from CA-IDTIMS U-Pb analysis of individual zircon phenocrysts, providing geochronological coverage across all stages of the Ordovician. Laurentia dominates this coverage (24) followed by the Baltic Basin (12), North Gondwana (11), Cuyania (4) and the Siberian Tungus Basin (1). Future tephra studies should seek to fill the numerous remaining gaps in the Ordovician time scale.
... The Wufeng-Longmaxi formations were formed during the turbulent geological history (Katian to Aeronian) and were affected by global and regional geological events, including volcanic eruptions (Su et al., 2009;Huff et al., 2014), Kwangsian Orogeny (Yu et al., 2015;Xie et al., 2020), glaciation (Nardin et al., 2011;Melchin et al., 2013), biological extinction (Chen et al., 2000;Bambach, 2006) and sudden changes in sea level (Haq and Schutter, 2008;Lu et al., 2020). Previous studies have mostly focused on one problem, and there is still a lack of analysis of the shale sedimentary process. ...
The Wufeng-Longmaxi Formations are the focus of shale gas exploration in China. Their sedimentation is affected by global and regional geological events, and the resulting heterogeneity hinders the expansion of exploration results. This study combines logging, mineralogy, and geochemistry to reconstruct the sedimentary mechanisms of shale in the southern Sichuan Basin and discusses its implications for exploration. The shale can be divided into third-order sequences, in which the Wufeng Formation and lower Long-1 Member are transgressive systems tracts (TST1 and TST2), and the Guanyinqiao Member and the middle-upper Long-1 Member are highstand systems tracts (HST1 and HST2). Volcanic eruption and glaciation evolution are the driving factors of the sedimentary environment during the TST. The area is in a cold-warm climate, characterized by anoxic conditions, slow sedimentation, booming productivity, and low terrigenous influx, thereby depositing four types of siliceous shale. The siliceous shale is rich in biogenic microcrystalline quartz and high TOC, which are the keys to becoming the “sweet spot” of shale gas. Microcrystalline quartz fills the intergranular pores to support the entire pore network framework. The organic matter undergoes thermal evolution to produce abundant organic matter pores, which constitute the main place for adsorbed gas and free gas. For the highstand systems tract, HST1 is the product of the peak of glaciation, mainly composed of calcareous shale and carbonate rocks. The sedimentation of HST2 is affected by turbidity currents and violent orogeny. The area is in a warm climate, characterized by high terrigenous influx, dysoxic-oxic conditions, medium productivity and rapid sedimentation rates. The lithofacies gradually changed from siliceous shale to mixed shale and argillaceous shale. Excessive clay minerals and low TOC make it difficult for HST2 to realize the commercial development of shale gas.
... Therefore, study of bentonite layers in sedimentary sequences is essential for accurate constraints on regional stratigraphy which could be further applied to regional paleogeographic and tectonic reconstructions. Moreover, bentonite horizons are often indicative of global volcanic activities that can be linked with environmental and climate changes, and related mass extinctions during earth's history (Huff et al., 1992(Huff et al., , 2014Delano et al., 1994;Su et al., 2003Su et al., , 2009Beauchamp and Grasby, 2012;Jones et al., 2017;Yang et al., 2019Yang et al., , 2022. Several bentonite layers have been recently recognized at the northern slope of the Borohoro Range along the northern Yili Block (Figs. 1B, 2 and 3). ...
... Its occurrence as interlayered horizons within siliceous shales indicates a semi-abyssal marine environment (Melchin et al., 2013). Thus, as a product of volcanic activities, bentonite layers preserved in sedimentary sequences have been widely used as isochronous event markers to represent large-scale regional or global volcanic eruptions (e.g., Huff et al., 1992Huff et al., , 2014Yang et al., 2019). ...
... Silurian transition remains hotly debated, it is suggested that the worldwide intensive volcanism was one of the most important factors (e. g., Huff et al., 2014;Deng et al., 2021), as it has been well documented by volcanic ashes in the major continents throughout the world, such as in Russia (Siberia; Huff et al., 2014), European (Baltica; Huff et al., 1992), North America (Laurentia; Kolata et al., 1996), and South China (Gondwana; Rong and Shen, 2002;Su et al., 2009;Yang et al., 2019). These volcanic ashes are considered to have originated from subduction -accretion orogenies related to the closure of the Panthaniassic Ocean and proto-Tethys Ocean (e.g., Yang et al., 2019). ...
The Yili Block is located at the Chinese western Tianshan and is a constituent of the Kazakhstan microcontinent. It played an important role in the evolution of the SW Central Asian Orogenic Belt (CAOB). The Yili Block underwent the Paleozoic orogeny during the subduction and closure of the Junggar Ocean. Late Paleozoic arc-type magmatic rocks have been widely recorded in the Yili Block; however, it is poorly constrained when and how the Junggar Ocean started to subduct beneath the Yili Block. In this study, we report new results of zircon LA-ICP-MS UPb dating and LuHf isotopic analysis on a series of bentonite beds in tightly folded upper Ordovician siliceous black shales of the Guozigou Section in the northern Yili Block. The occurrence of bentonite layers and associated sulfides within graptolite-bearing siliceous black shales indicates multiple marine volcanic eruptions. Magmatic zircons separated from seven representative bentonite samples yielded consistent UPb ages ranging from 449.5 ± 2.4 Ma to 444.8 ± 2.0 Ma (Katian). In situ zircon LuHf isotopic analyses show mostly positive εHf(t) values (−0.01 and 1.31 to 11.7) and Neoproterozoic single-stage Hf model ages (TDM1 = 0.6– 1.0 Ga). A linear correlation between the εHf(t) and TDM1 suggests that these zircons likely crystallized from a common magma originated from a depleted mantle source with variable involvement of Precambrian continental crust. Our new zircon ages and Hf isotopic data are comparable with those of the Middle-Late Ordovician continental arc-type magmatic rocks in the nearby Wenquan area, both indicating that the subduction of the Junggar Ocean beneath the northern Yili Block started in the Middle-Late Ordovician, and are therefore important for early Paleozoic paleogeographic and tectonic reconstruction of the Paleo-Asian Ocean domain. In addition, the Late Ordovician marine bentonites and black shales coincide with the worldwide intensive volcanic activities and related climate/environment changes during late Katian to Hirnantian. Thus, these new data also provide further arguments for possible causes of the global climate change and mass extinction during the Ordovician-Silurian transition.
... The available methods of isotopic dating of the sediments provided so far diminutive but important additional information. The 206 Pb/ 238 U zircon date obtained for the ash (bentonite) interlayer of the upper part of the Upper Ordovician Mangazei Formation (5 m below its top) exposed in the middle reaches of the Podkamennaya Tunguska River (near the mouth of the right tributary of the Stolbovaya River) allowed the age of the rocks to be established at 450.58 ± 0.27 Ma (Huff et al., 2014). According to the absolute dating of chronostratigraphic units in the updated ISS version (Goldman et al., 2020), the boundary between the Sandbian and Katian stages is 453 Ma, which suggests that the upper part of the Mangazei Formation (at least the upper 5 m of its stratum) belongs to the Katian Stage. ...
... There were 180 specimens of satisfactory and good preservation. (Huff et al., 2014), it can be assumed that the deposits stratigraphically above the dated layer are obviously related to the Katian Stage. No ash layers were found in the section of the Mangazei Formation studied in the cliffs of the Bolshaya Nirunda River. ...
... No ash layers were found in the section of the Mangazei Formation studied in the cliffs of the Bolshaya Nirunda River. However, comparison of a series of outcrops in the middle reaches of the Podkamennaya Tunguska (Huff et al., 2014) suggests that the uppermost part of the Mangazei Formation is exposed in the section of the Bolshaya Nirunda River (Fig. 2). E.? williereae was found only in the uppermost samples of the formation, while the ten samples analyzed collected from the lower part of the section were devoid of this species. ...
The morphology of acritarch species Elektoriskos? williereae (G. & M. Deflandre, 1965) Vanguestaine, 1979, previously considered as a Silurian index of the Llandovery, has been clarified, the diagnosis emended, and the stratigraphic distribution expanded. According to new data, the first appearance of E.? williereae was confined to the upper part of the Baksan Horizon near the boundary of the Sandbian and Katian stages of the Upper Ordovician. Co-occurrence of E.? williereae with representatives of the genera Gordonirundum , Nirundella , Peteinosphaeridium , and Sacculidium is a distinct, well-recognizable palynological characteristic of the Katian deposits of the Siberian Platform which can serve for identification, dating, and correlation of the acritarch-bearing strata. Morphological variations in E.? williereae are a stable diagnostic feature of the species that distinguishes it from other taxa. It is possible that the species was sensitive to paleoenvironments and, probably, highly adaptive, which allowed it, remaining almost unchanged, to overcome the global Late Ordovician cooling, which became fatal for many other groups of organisms.
... The basin-wide lithologic changes are clearly tied in time and space to those eruptive events (Quinton et al., 2017), yet no consensus exists about the tectonic setting for eastern Laurentia at the time of these super-eruptions. Constraints include (1) regional paleogeographic relations of Laurentia and Baltica during this time (e.g., Huff et al., 2014); (2) the mineralogy and petrology of the most widespread K-bentonites (Haynes, 1994;(Haynes et al., 1995); , and (3) the geologic and tectonic conditions that result in caldera-producing eruptions (Gregg et al., 2012), thus several tectonomagmatic settings could have produced this explosive and likely caldera-forming volcanism (Fig. 3). These different settings include: (1) a continental magmatic arc above a subduction zone, analogous to the Andes arc (e.g., Caffe et al., 2012); (2) an island microcontinent with continental-crust basement, above a subduction zone consuming oceanic and/or continental crust, with analogies in Sumatra, Timor and the Banda Arc, the Luzon Arc, and New Guinea, (e.g., Chesner, 2012;Koulakov et al., 2016); (3) a continental hot spot caldera complex, such as Yellowstone in Wyoming (e.g., Stelten et al., 2015), or the Valles Caldera in New Mexico (e.g., Wilcock et al., 2013); (4) part of a more tectonically complex area, for example a region undergoing extension and transpression, like the Long Valley Caldera in California (e.g., Chamberlain et al., 2015), or parts of Papua New Guinea (e.g., Large et al., 2018). ...
We evaluate competing hypotheses regarding tectonic models of the early Taconic Orogeny in the Southern Appalachians during the Blountian tectophase with new geochemical data obtained from analyses of apatite and zircon phenocrysts, and melt and mineral inclusions therein, from the Ordovician Deicke K-bentonite (453.35 ± 0.10 Ma). Apatite geochemistry confirms that samples from different locations represent the same eruptive event, and zircon geochemistry and UPb geochronology (including several Grenville-age inherited detrital cores) confirm an evolved magma of continental-arc composition, with the trace-metal geochemistry of magmatic Taconic-age rims on Deicke zircons pointing to a provenance of continental crustal igneous rock melts, specifically a granitic melt with a high level of differentiation, rather than a melt that was mantle-derived, or strongly mantle-influenced. Melt inclusions within Deicke phenocrysts are dacitic (apatite) to rhyolitic (zircon), differences that imply an evolving Deicke magma during its eruption.
Our data 1) indicate multiple crustal events, and 2) are tectono-chemical evidence supporting an arc-trench subduction system where subducting preexisting sedimentary rocks were subsequently incorporated into the melt during or prior to collision. Indonesia provides modern analogs: the Banda Arc system, where Australian continental crust is jamming the subduction zone in association with the development of a foreland basin and a sedimentary wedge; the New Guinea – western Melanesian region, with its orogenic highlands and associated foredeep; and the Sumatra –Toba system, where subduction-related explosive volcanism has generated enormous caldera-forming eruptions above continental crust basement. Thus, a model for closure of the Iapetus Ocean involving subduction of older passive margin sediments as part of an island-arc collision with the Laurentian passive margin is acceptable, but models based on a back-arc basin are not compatible with our data.
... In the Late Ordovicianearly Silurian, extensive volcanic eruptions occurred in Laurentia, Baltica, Siberia and Gondwana (Kolata et al., 1996;Huff, 2008aHuff, ,b, 2014Su et al., 2009, Fig. 1B). During this period, voluminous volcanic ash layers (transformed into bentonite) were widely distributed on the Yangtze Platform (Fig. 4), accompanied by the deposition of shales and limestones (Su et al., 2009;Yang et al., 2019;Du et al., 2020). ...
The organic-rich black shales from the Late Ordovician and early Silurian were identified as essential source rocks for shale gas exploration and development in South China. To investigate the influence of volcanic activity on the deposition of organic-rich shales in the Wufeng and Longmaxi formations, this study presents the carbon isotope and geochemical compositions of the Upper Ordovician-lower Silurian succession of the Yangtze Platform. The organic-rich Wufeng and lower Longmaxi shales are characterized by isotopically negative carbon shifts; however, obviously high δ13Corg values are shown in the organic-poor shales of the upper Longmaxi Formation. The negative δ13Corg excursion is attributed to 12C-depleted CO2 sourced from volcanic activity. Furthermore, the positive δ13Corg excursion in the upper Longmaxi Formation occurs because a large amount of 12C was removed from the ocean-atmosphere system through continuous burial of organic carbon. The biogenic silica (Sibio) contents and (Cu + Ni)/Al ratios in the lower Longmaxi Formation display higher values than those in the upper Longmaxi Formation, suggesting that the primary productivity gradually decreased from the Wufeng Formation to the Longmaxi Formation. This study proposes that high primary productivity was related to accelerated chemical weathering and release of micro-nutrients. The former emphasizes that high pCO2 and globally high temperatures can enhance chemical weathering, so that more nutrients are transported from continents to oceans (Yan et al., 2010, 2019). The latter highlights that volcanic material input can act as fertilizer by releasing many nutrients. Moreover, the values of UEF and MoEF are higher in the Wufeng and lower Longmaxi formations than in the upper Longmaxi Formation, suggesting that the oxygen concentration increased upward through the section. Given the positive correlations between indicators of productivity and redox conditions, the constantly high primary productivity would consume much O2, resulting in anoxic conditions in the Wufeng and lower Longmaxi formations. Overall, this study considers that volcanic activity-driven primary productivity is the first-order control for organic matter (OM) enrichment.
... Tens of VABs have also been found in Late Ordovician strata in other areas of the world, such as North America, England Wales, Sweden, East Baltic, Poland, and the Carnic Alps (Huff, 2008;Huff et al., 2014;Yang et al., 2019). Some researchers think that the volcanic activity during the OST period probably had a global influence (Kolata et al., 1996;Huff, 2008;Huff et al., 2014). ...
... Tens of VABs have also been found in Late Ordovician strata in other areas of the world, such as North America, England Wales, Sweden, East Baltic, Poland, and the Carnic Alps (Huff, 2008;Huff et al., 2014;Yang et al., 2019). Some researchers think that the volcanic activity during the OST period probably had a global influence (Kolata et al., 1996;Huff, 2008;Huff et al., 2014). Du et al. (2020) used zircon U-Pb ages to deduce that the volcanic activity during the OST in SC was part of this global phenomenon. ...
Whether volcanic activity in South China (SC) was synchronous with global volcanism during the Ordovician-Silurian transition (OST) has long been an interesting topic. In recent years, an increasing number of volcanic ash beds (VABs) have been identified in outcrops and individual wells, thereby providing more evidence to explore this issue. Here, we used 12 outcrops and 3 wells to investigate the VABs distribution in SC and compared it with the distribution of VABs in other parts of the world. Detailed analysis reveals that the volcanism in SC was not only a part of the global volcanic activity but also had unique characteristics. In SC, the volcanic activity may have been stronger than that in other areas, because more VABs have been discovered. Additionally, the VABs in SC primarily formed during the Late Ordovician Katian and Hirnantian stages and the early Silurian Rhuddanian stage, while in other areas, they mainly formed during the Late Ordovician Sandbian and Katian stages. These characteristics may indicate that the volcanic activity in SC occurred slightly later than that in other areas. Furthermore, the interval with a dense VAB distribution corresponds to the organic-rich shale section, indicating that volcanic activity influenced the formation of the organic-rich shale to some degree by changing the paleoproductivity and paleoredox conditions. These results provide some insight into the relationship between volcanic activity in SC and global volcanism during the OST, and information on the impact of volcanic activity on the formation of organic-rich shale.
... The Central and Upper Yangtze regions of SC are dominated by the Sichuan basin, including parts of Yunnan, Guizhou, Chongqing, Hubei and Hunan provinces, covering an area of approximately 35 × 10 4 km 2 (Yan et al., 2015a(Yan et al., ,2015bChen et al., 2016). During the Late Ordovician-early Silurian period, SC was located near the paleoequator and belonged to the tropical and subtropical zone on the western margin of Gondwana ( Fig. 1A) (Cocks, 2001;Huff et al., 2014). Due to the continuous expansion of the Qianzhong uplift, Kangdian uplift, Chuanzhong uplift, and Hannan uplift after the Middle Ordovician, the Yangtze platform gradually became a semiconfined shallow sea basin (Sun et al., 2018). ...
... Global geological events include mass extinction (Sheehan 2001), widespread volcanism (e.g. Huff et al. 1998Huff et al. , 2010Huff et al. , 2014 and intensive orogeny (e.g. Murphy et al. 2011;Torsvik and Cocks 2017;Li et al. 2018;Zhao et al. 2018). ...
... These K-bentonites have been documented from Gondwana, Siberia, the Yangtze Platform, Laurentia, Baltica etc. (Fig. 1a; e.g. Bergström et al. 1998;Huff et al. 1998Huff et al. , 2010Huff et al. , 2014. ...
Numerous K-bentonites from the Ordovician–Silurian (O–S) transition in South China record important information about the geodynamics of volcanic activity in the northern margin of Gondwana. A series of K-bentonite beds have been identified in the Zhoujiaxi Group (Early Silurian) in foreland basins from central Hunan Province, China. They are dominantly composed of illite with minor kaolinite. Volcanogenic minerals include quartz, feldspar, biotite, and lesser apatite and zircon. U–Pb zircon ages from three beds, 442.8 ± 1.8, 442.2 ± 1.9 and 441.6 ± 2.0 Ma are compatible with the age of the O–S global boundary. Geochemical results indicate calc-alkaline felsic magmas derived from continental crust and erupted in a subduction-related collisional environment. Isopach schemes and grain size reveal that the volcanic ashes were sourced from a volcanic event likely with a volcanic explosivity index of 8, and transported 300 – 1000 km away from the palaeo SSE. The volcanism was associated with northwestern subduction of the Zhenghe-Dapu Ocean beneath the southeastern South China Block (SCB) on the northern margin of Gondwana. The Zhenghe-Dapu fault might be a suture zone, implying the consumption of the Zhenghe-Dapu Ocean during collision between the Nanhai terrane and the SCB. This study supports that the Wuyi-Yunkai Orogenic Belt is a collision-type orogen rather than an intraplate belt.
Supplementary material: Plots and geochemical data are available at https://doi.org/10.6084/m9.figshare.c.5027096
