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Dongjin Lee - One of the best experts on this subject based on the ideXlab platform.
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Late Ordovician stromatoporoids from the xiazhen formation of south china paleoecological and paleogeographical implications
Geological Journal, 2020Co-Authors: Juwan Jeon, Kun 梁昆 Liang, Jino Park, Suk Joo Choh, Dongjin LeeAbstract:The Upper Ordovician Xiazhen Formation, which crops out in Zhuzhai, near the Jiangshan-Changshan-Yushan region of southeast China, consists of a variety of carbonate-siliciclastic lithofacies representing a shallow-water platform environment. A total of eleven stromatoporoid genera in two orders, comprising three clathrodictyid genera (Clathrodictyon, Ecclimadictyon, and Labyrinthodictyon) and eight labechiid genera (Cystostroma, Rosenella, Pseudostylodictyon, Aulacera, Stylostroma, Pachystylostroma, Labechia, and Labechiella), are recognized from 18 stratigraphic units representing a wide range of depositional environments in the formation. Clathrodictyon is the most abundant stromatoporoid genus, occupying a long stratigraphic range and a wide range of lithofacies. It also occurs as a major component of patch reefs throughout the formation. The labechiids, in contrast, are highly diverse but most genera have restricted stratigraphic distributions, occurring in a narrow range of depositional environments. The size and growth form of stromatoporoids in the formation are considered to be primarily intrinsic characteristics of each genus but in some cases also seem to be reLated to lithofacies: clathrodictyids exhibit a wide spectrum of growth forms and have broader ecological plasticity and more flexible growth strategies than do labechiids. The Late Ordovician stromatoporoids of the Xiazhen Formation exhibit close biogeographic affinities to those of central New South Wales and the Tasmanian shelf of Australia. The discovery herein of Labyrinthodictyon and Stylostroma from the Upper Ordovician of South China further supports this close relationship. The stromatoporoids from South China exhibited one of the highest diversities of all paleocontinents during the Late Ordovician, suggesting that South China, together with Australia, was a locus of Late Ordovician stromatoporoid diversification.
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tetradiid siliceous sponge patch reefs from the xiazhen formation Late katian southeast china a new Late Ordovician reef association
Sedimentary Geology, 2012Co-Authors: Sung Wook Kwon, Jino Park, Suk Joo Choh, Dongjin Lee, Dongchan LeeAbstract:Decimetre-scale domal to tabular patch reefs consisting of dendroid tetradiids are found in the Late Ordovician (Late Katian) Xiazhen Formation, southeast China. It is intriguing to observe that siliceous sponges occur together with the tetradiids in many patch reefs, as this has not been previously reported. The tetradiid Rhabdotetradium jiangshanense are preserved in situ and the siliceous sponges, where present, as spicule networks. Calcimicrobe Ortonella encrusting tetradiid tubes and burrows filled with faecal pellets also constitute as subordinate components of the patch reef. The tetradiid tubes are regarded as frame-builders that are commonly surrounded and encrusted by the siliceous sponges. The sponges, wherever observed, form the bulk of the patch reef and are regarded as a primary constructor as well as binder of the patch reef. Burrows filled with faecal pellets often penetrate the area between tetradiids and sponge spicule networks in the boundstone and these are considered to be the loci of dweller. Where the sponges and tetradiids co-occur, the tetradiid tubes are sparsely distributed and commonly display non-quadripartite fission (i.e., bipartite or tripartite). In contrast, where the sponges are rare in the patch reef, the tetradiid tubes are densely spaced and predominantly display quadripartite fission. This indicates that the tetradiid growth was influenced by the presence of siliceous sponges. This finding of the new Late Ordovician reef association and their mutual interplay extend our understanding of the Early Palaeozoic carbonate reefs. It reaffirms the need for multidisciplinary studies of carbonate buildups where similar interactions with siliceous sponges might have been overlooked.
Mark E Patzkowsky - One of the best experts on this subject based on the ideXlab platform.
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effects of mass extinction and recovery dynamics on long term evolutionary trends a morphological study of strophomenida brachiopoda across the Late Ordovician mass extinction
Paleobiology, 2018Co-Authors: Judith A Sclafani, Curtis R Congreve, Andrew Z Krug, Mark E PatzkowskyAbstract:Mass extinctions affect the history of life by decimating existing diversity and ecological structure and creating new evolutionary and ecological pathways. Both the loss of diversity during these events and the rebound in diversity following extinction had a profound effect on Phanerozoic evolutionary trends. Phylogenetic trees can be used to robustly assess the evolutionary implications of extinction and origination.We examine both extinction and origination during the Late Ordovician mass extinction. This mass extinction was the second largest in terms of taxonomic loss but did not appear to radically alter Paleozoic marine assemblages. We focus on the brachiopod order Strophomenida, whose evolutionary relationships have been recently revised, to explore the disconnect between the processes that drive taxonomic loss and those that restructure ecological communities.Apossible explanation for this disconnect is if extinction and origination were random with respect to morphology. We define morphospace using principal coordinates analysis (PCO) of character data from 61 Ordovician–Devonian taxa and their 45 ancestral nodes, defined by a most parsimonious reconstruction in Mesquite. A bootstrap of the centroid of PCO values indicates that genera were randomly removed from morphospace by the Late Ordovician mass extinction, and new Silurian genera were clustered within a smaller previously unoccupied region of morphospace. Diversification remained morphologically constrained throughout the Silurian and into the Devonian. This suggests that the recovery from the Late Ordovician mass extinction resulted in a long-term shift in strophomenide evolution. More broadly, recovery intervals may hold clues to understanding the evolutionary impact of mass extinctions.
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reconstructing Late Ordovician carbon cycle variations
Geochimica et Cosmochimica Acta, 2013Co-Authors: Richard D Pancost, Mark E Patzkowsky, Katherine H Freeman, Achim D Herrmann, Leho Ainsaar, Tonu MartmaAbstract:Abstract The role of carbon dioxide in regulating climate during the early Paleozoic, when severe glaciations occurred during a putative greenhouse world, remains unclear. Here, we present the first molecular carbon isotope proxy-based estimates for Late Ordovician (early Katian) pCO2 levels, and explore the limitations of applying this approach to the reconstruction of Paleozoic pCO2. Carbon isotope profiles from three sites in Laurentia (Iowa, Ontario and Pennsylvania) and one site in Baltica (Estonia) exhibit overall low isotope fractionation between organic and inorganic carbon during photosynthesis (ep) and these values declined during the early Katian carbonate carbon isotope excursion (or Guttenberg Carbon Isotope Excursion, GICE). Algal ep values are sensitive to changes in CO2 concentrations, algae cell morphologies, and cell growth rates. To constrain these factors, we present molecular evidence that a decrease in the relative abundance of cyanobacteria and a change in the eukaryotic algae community co-occurred with the GICE. Regardless of local biotic or oceanographic influences, a decline in ep values indicates photosynthesis was sensitive to carbon concentrations, and via analogy with modern taxa, constrains pCO2 to below ∼8× pre-industrial levels (PIL), or about half of previous estimates. In addition, the global, positive carbon isotope excursions expressed in a wide variety of sedimentary materials (carbonate, bulk organic matter, n-alkanes, acyclic and cyclic isoprenoid hydrocarbons), provide compelling evidence for perturbation of the global carbon cycle, and this was likely associated with a decrease in pCO2 approximately 10 million years prior to the Hirnantian glaciations. Isotopic records from deeper water settings suggest a complex interplay of carbon sources and sinks, with pCO2 increasing prior to and during the early stages of the GICE and then decreasing when organic carbon burial outpaced increased volcanic inputs.
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diversity partitioning of a Late Ordovician marine biotic invasion controls on diversity in regional ecosystems
Paleobiology, 2007Co-Authors: Mark E Patzkowsky, Steven M HollandAbstract:Biotic invasions are a common feature of the fossil record, yet remarkably little is known about them, given their enormous potential to reveal the processes that reguLate local and regional diversity over long time scales. We used additive diversity partitioning to examine how diversity structure changed as a result of a marine biotic invasion in tropical, shallow and deep subtidal environments spanning approximately 4 Myr in the Late Ordovician. The biotic invasion increased richness in the regional ecosystem by nearly 40%. Within-habitat turnover diversity accounts for most of the increase in richness, with between-habitat turnover diversity contributing a lesser amount. Increases in these components of diversity were accommodated by increased packing of species along a depth gradient and increased habitat heterogeneity. Diversity metrics that incorporate taxon abundance (Shannon information, Simpson's D) show similar patterns and reveal that many invading taxa were locally abundant and widespread in their occurrence. Extinction of incumbent taxa did not foster the invasion; rather the invasion appears to be linked to a regional or global warming event. Taken together, these observations indicate that these Late Ordovician marine communities were open to invasion and not saturated with species. Moreover, the increase in species diversity caused by the invasion was not ephemeral; instead it lasted for at least 1 Myr. Similar studies of other biotic invasions in the fossil record are necessary to determine (1) the factors, such as extinction of incumbents or resource limitation, that may facilitate or inhibit invasion in ancient ecosystems; (2) how local and regional ecosystems respond to invasion; and (3) the extent to which biotic invasions play a substantial role in ecosystem change through geologic time.
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response of Late Ordovician paleoceanography to changes in sea level continental drift and atmospheric pco2 potential causes for long term cooling and glaciation
Palaeogeography Palaeoclimatology Palaeoecology, 2004Co-Authors: Mark E Patzkowsky, Achim D Herrmann, Bernd J Haupt, Dan Seidov, Rudy SlingerlandAbstract:Abstract We performed sensitivity experiments using an ocean general circulation model at two stages of the Late Ordovician (Caradoc, ∼454 Ma; Ashgill, ∼446 Ma) under a range of atmospheric pCO2 values (8–18× PAL; pre-industrial atmospheric level) at high and low sea level. The model results indicate that the long-term cooling trend during the Late Ordovician can be explained by progressive cooling of the global ocean in response to falling levels of atmospheric pCO2, sea level change, and paleogeographic change. These results also explain the occurrence of low latitude cool-water carbonates in North America. In all simulations, a drop in sea level led to a reduction in poleward ocean heat transport. This indicates a possible positive feedback that could have enhanced global cooling in response to sea level drop during the Late Ordovician. Alterations in poleward ocean heat transport linked to changes of atmospheric pCO2 also indicate that there is a threshold of 10× PAL, above which ocean current change cannot be responsible for glaciation in the Late Ordovician. Continental drift could explain the observed global cooling trend in the Late Ordovician through a combined poleward ocean heat transport feedback and increased ice-albedo effect if atmospheric pCO2 was low during the entire Late Ordovician. The model results further indicate that the response of meridional overturning to changes in paleogeography, atmospheric pCO2, and sea level is stronger than the response of surface circulation to these perturbations. Because the overturning circulation is so strong, meridional overturning was the dominant mechanism for described changes in heat transport in the Late Ordovician.
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a weathering hypothesis for glaciation at high atmospheric pco2 during the Late Ordovician
Palaeogeography Palaeoclimatology Palaeoecology, 1999Co-Authors: Lee R Kump, Mark E Patzkowsky, Michael A Arthur, M T Gibbs, D S Pinkus, Peter M SheehanAbstract:New paired carbonate and organic-carbon isotope analyses from Nevada, USA, together with a consideration of the effects of mountain-building and ice-sheet coverage of the continents on atmospheric pCO2, lead to a new hypothesis for the cause of the Late Ordovician glaciation. We suggest that the Taconic orogeny, which commenced in the Late-middle Ordovician, caused a long-term decline in atmospheric pCO2 through increased weatherability of silicate rocks. Ice-sheet growth was triggered when pCO2 decreased to a threshold of ∼10× present atmospheric level and proceeded by positive ice-albedo feedback. In the midst of glaciation, atmospheric pCO2 began to rise as continental silicate weathering rates declined in response to coverage of weathering terrains by ice sheets. At first, this enhanced greenhouse effect was overcompensated for by ice-albedo effects. Ultimately, however, atmospheric pCO2 reached a level which overwhelmed the cooling effects of ice albedo, and the glaciation ended. The isotope results can be interpreted to indicate that atmospheric pCO2 rose during the glaciation, consistent with other proxy information, although alternative interpretations are possible. The large, positive carbonate isotope excursion observed in Late Ordovician rocks around the world is explained as the expected response to increased carbonate-platform weathering during glacioeustatic sea-level lowstand, rather than as a response to increased organic-carbon burial.
Xiaosong Wei - One of the best experts on this subject based on the ideXlab platform.
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spatial variation of carbon isotopic compositions of carbonate and organic matter from the Late Ordovician sedimentary succession in the yangtze platform south china implications for sea level eustacy and shoaling of marine chemocline
Journal of Asian Earth Sciences, 2020Co-Authors: Xiangrong Yang, Detian Yan, Daizhao Chen, Mu Liu, Xiaohui She, Junfeng Zhang, Xiaosong WeiAbstract:Abstract Spatial correlation of isotopic chemostratigraphy across ancient epeiric basins is of particular interest in the field of geology. This study examines the carbon isotopic compositions of carbonate and organic matter from the Late Ordovician sedimentary succession in the Yangtze Platform, including the Linxiang (LX) Formation deposited in the bottom and the Tiezufeike (TZFK)/Daduhe (DDH)/Wufeng (WF) formations in the top. Paired δ13Ccarb and δ13Corg analyses of the Upper Ordovician strata on the Yangtze Platform were recorded, and the results show that the rocks in the LX Formation have high δ13Ccarb and δ13Corg values relative to those in the DDF/TZFK/WF formations. Additionally, a variation of ~ 2‰ was found between shallow- and deep- water settings during the Late Ordovician: heavier δ13Ccarb and δ13Corg values are observed at the Wukemuchang (WKMC) and Wanhe (WH) sections, representing the shallow regions of the Yangtze Platform, relative to the Tianjiawan (TJW) and Tianba (TB) sections representing the deeper margin of the Yangtze Platform. We suggest that the variations of δ13C in carbonate and organic matter are reLated to the sea - level eustacy and shoaling of marine chemocline: (1) sea - level rise driven decrease in local scale carbonate weathering; (2) decreased decomposition of organic matter under anoxic conditions; and (3) incorporation of non - photosynthetic chemoautorophic bacteria living in deeper waters. The △13C (△13C = δ13Ccarb – δ13Corg) values in both the WH and WKMC sections display an increasing trend upward from the LX Formation to the overlying strata, varying from 27.8‰ to 31.2‰ and from 28.1‰ to 31.1‰, respectively. These increased △13C values are reLated to the enhanced nutrients and correspondingly high primary productivity, and thus that, the anoxic water conditions and high primary productivity may be the significant factors in the deposition of Late Ordovician black shales.
Renbin Zhan - One of the best experts on this subject based on the ideXlab platform.
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altaethyrella brachiopoda from the Late Ordovician of the tarim basin northwest china and its significance
Journal of Paleontology, 2018Co-Authors: Colin D Sproat, Renbin ZhanAbstract:Altaethyrella tarimensis, a new species of rhynchonellide brachiopod, is described from the Late Katian (Late Ordovician) Hadabulaktag Formation in the Kuruktag region of Xinjiang, Northwest China on the northeastern edge of the Tarim Basin. Serial sections of the shell clearly show no dorsal median septum or septalium in the dorsal valve, and no spiralia or atrypide-style crura. Like other species of the genus, A. tarimensis n. sp. exhibits a high degree of intraspecific variation, including variations in shell shape and size, number of ribs in the sulcus at the anterior, and degree of asymmetry. The discovery of Altaethyrella in Tarim has important paleogeographic implications, indicating a close relationship between the Late Ordovician brachiopod faunas of Tarim and those of the Kazakh terranes and North and South China paleopLates, supporting a recently published paleogeographic projection that places Tarim near the Chu-Ili terrane during the Late Ordovician. The abundant large biconvex shells of A. tarimensis n. sp. would have provided a firm substrate for encrusting filter feeders like bryozoans to establish on the Kuruktag Platform.
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Late Ordovician deep-water brachiopod fauna from Raheen, Waterford Harbour, Ireland.
'Royal Irish Academy', 2017Co-Authors: Harper, David A.t., Parkes, Matthew A., Renbin ZhanAbstract:The Raheen Formation at Newtown Head in Waterford Harbour is a small isoLated section of Ordovician rocks, dominated by volcanics of the Duncannon Group, but with interbedded fossiliferous shales. Although a brachiopod and trilobite dominated fauna has been known since the mid-nineteenth century, only the trilobites and cystoids have been assessed in modern terms. This paper describes the brachiopod fauna for the first time. The assemblage from Raheen is overwhelmingly dominated by the dalmanelloid Onniella, with the small plectambonitoid Sericoidea comprising the second most numerous species; both are represented by new species. This revision has also identified a wide range of other genera, but all in very small numbers. These include an obolid, a paterulid, Paracraniops and Orthisocrania divaricata (M'Coy) amongst the non-articuLated brachiopods. ArticuLated genera present include the orthoids Nicolella, Ptychopleurella, Sulevorthis, Skenidioides and the plectambonitoid Leptestiina. Very rare forms include Idiospira? and Palaeostrophomena, together with possibly Biscuspina and Sowerbyella. The brachiopod revision supports the Late Caradoc (early Katian) age indicated by the trilobite fauna. The trilobite fauna generally indicates a probable deeper-water environment and the brachiopod assemblage confirms an outer-shelf environment. Although elements of the assemblage indicate affinity with the well-defined Late Ordovician Foliomena fauna, it probably occupied a more shoreward position
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perturbation of the marine nitrogen cycle during the Late Ordovician glaciation and mass extinction
Palaeogeography Palaeoclimatology Palaeoecology, 2016Co-Authors: Thomas J Algeo, Junhua Huang, Genming Luo, Renbin Zhan, Detian Yan, Jiangsi Liu, Shucheng XieAbstract:Abstract The Late Ordovician was a critical interval in geologic history, during which both the biosphere and marine environments underwent severe perturbations, including one of the ‘Big Five’ Phanerozoic mass extinctions and the massive but short-term (~ 0.5-Myr) Hirnantian glaciation. The onset and termination of the Hirnantian glaciation have been widely accepted as the triggers for the two extinction pulses that comprise the Late Ordovician biocrisis, but the mechanisms that caused the Hirnantian glaciation itself remain poorly known. Here, we analyze the nitrogen isotope composition (δ 15 N) of two sections in South China (Wangjiawan and Nanbazi) in order to better understand nitrogen cycle perturbations in the Late Ordovician ocean and their relationship to contemporaneous climatic and biogeochemical changes. Low δ 15 N (~ 1‰) in the upper Katian and lower Rhuddanian of both sections suggests intensive (i.e., near-quantitative) denitrification and, thus, nitrogen fixation as the main source of biologically available nitrogen for primary producers. A positive δ 15 N excursion in both sections during the Hirnantian indicates weaker (i.e., non-quantitative) denitrification, possibly as a result of more vigorous thermohaline circulation and improved ocean ventilation. Weaker denitrification would have reduced the flux of N 2 O, an intermediate product of denitrification, to the atmosphere. N 2 O is a potent greenhouse gas, and a major decline in its production would have led to cooler climatic conditions and, ultimately, the Hirnantian glaciation. A global survey of published nitrogen isotope records suggests that similar processes operated broadly within the Late Ordovician global ocean.
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large perturbations of the carbon and sulfur cycle associated with the Late Ordovician mass extinction in south china
Geology, 2009Co-Authors: Tonggang Zhang, Renbin Zhan, Yanan Shen, Shuzhong Shen, Xu ChenAbstract:High-resolution δ 13 C data of organic carbon from a continuous section of the Late Ordovician–Early Silurian reveal two positive δ 13 C excursions that are associated with the mass extinction in South China. The fi rst stratigraphic δ 34 S measurements on pyrite tied to well-established biostratigraphy indicate a large perturbation of the sulfur cycle, consistent with major sea-level changes reLated to the glaciation. The elevated δ 34 S values of pyrites and a large, short-lived negative δ 34 S excursion of ~20‰ associated with the decay of the glaciation suggest deep-water anoxia during the Hirnantian Stage, in contrast to the conventional view that the global oceans were oxygenated. We suggest that deep-water anoxia may have contributed to the Late Ordovician mass extinction in South China and possibly elsewhere.
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epipunctae and phosphatized setae in Late Ordovician plaesiomyid brachiopods from anticosti island eastern canada
Journal of Paleontology, 2007Co-Authors: Jisuo Jin, Renbin Zhan, Paul Copper, W G E CaldwellAbstract:Abstract Epipunctae, a new type of shell perforation, are well developed in typical taxa of the family Plaesiomyidae, a group of common orthide brachiopods from Laurentia and some other tropically located tectonic pLates of Late Ordovician age. These minute, prominently elongate, tubular structures are similar to endopunctae in size and density, but differ in being oblique, intersecting the shell surface at a relatively low angle, and being confined largely to the outer portion of the shell wall. The tubules are similar in orientation to aditicules within the same shells but are much smaller and denser, usually aligned along fine growth lines and arranged in crude longitudinal columns. Exceptionally preserved phosphatic molds of bundled setal canals inside epipunctae and aditicules, described for the first time in this paper, are direct evidence that these two types of tubular structures of different sizes had the same function of housing sensory setae along the shell margin, but both the setae and the tu...
Zhang Bao - One of the best experts on this subject based on the ideXlab platform.
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climatic and oceanic controlled deposition of Late Ordovician early silurian black shales on the north yangtze platform south china
Marine and Petroleum Geology, 2019Co-Authors: Yan Detian, Chen Daizhao, Wang Zhuozhuo, Li Jing, Yang Xiangrong, Zhang BaoAbstract:Abstract Black shales deposited across the Late Ordovician and Early Silurian transition are considered to be the most important source rock and shale gas reservoirs in the Yangtze region of South China. However, the origin of these sediments remains contentious. In this study, we investigated the systematic changes in total organic carbon (TOC), organic carbon isotopes (δ13Corg), major elements and trace elements on the Ordovician-Silurian boundary strata from Qiaoting, North Yangtze Sea, to reconstruct the climatic conditions, redox changes, primary productivity, and other factors there, promoting the understanding for the formation mechanism of the organic-rich black shales. Element compositions and their ratios suggest that the black shales studied here were dominantly sourced by the felsic igneous rock, which is similar to granodiorite in composition. Paleoclimatic proxies (CIA, CIW, δ13Corg) suggest that the global climate system experienced significant changes from warm-humid to cold-dry and then to warm-humid climates during the Ordovician-Silurian transition. Paleoredox indices (S/C, U/Th, Ni/Co and V/(V + Ni) ratios) also demonstrate fluctuating redox variations from anoxic to oxygenated, and then to anoxic states during this interval in the Yangtze Sea, which describe an oxygenated Guanyinqiao strata sandwiched between the stagnant and anoxic Wufeng and Longmaxi black shales. Paleoproductivity parameters (TOC, Babio contents and P/Al ratio) suggest that the organic-rich Wufeng and Longmaxi black shales, were deposited with a high biological productivity, while the organic-lean Guanyinqiao sediments were deposited with a low biological productivity. These data demonstrate large climatic and oceanic fluctuations during the Ordovician-Silurian transition, providing essential controlling factors on the oceanic anoxia, primary productivity, and subsequent organic-rich black shale depositions in the Yangtze region during the Late Ordovician and Early Silurian intervals.
