18 results on '"Chenyi Tu"'
Search Results
2. Tracing the sedimentary provenance of the Mesoproterozoic rocks from Taoudeni Basin (∼ 1.1 Ga) Mauritania: Evidence from Sm/Nd and elemental geochemistry
- Author
-
Mohamed Ghnahalla, Olabode M. Bankole, Ahmed Abd Elmola, Marc Poujol, Claude Fontaine, Mohamed Salem Sabar, Alain Trentesaux, Chenyi Tu, Timothy W. Lyons, Abderrazak El Albani, Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université de Nouakchott Al-Aasriya (UNA), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Nord]), University of California [Riverside] (UC Riverside), University of California (UC), Region Nouvelle Aquitaine, French Embassy at Nouakchott (Mauritania), and Interdisciplinary Consortia for Astrobiology Research (ICAR) within NASA’s Astrobiology Program (T.W.L.)
- Subjects
Mesoproterozoic ,Elemental geochemistry ,Geochemistry and Petrology ,[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry ,Provenance ,Taoudeni Basin ,[SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy ,Mauritania ,Geology ,Nd isotope - Abstract
International audience; The Mesoproterozoic era is a crucial period in Earth history characterized by muted oxygen levels in the atmosphere–ocean system. This period is well represented in the non-metamorphosed sedimentary rocks from the Taoudeni Basin, Mauritania. Few studies have been carried out to trace the sources of these sedimentary archives. Here, we examined the sedimentary rocks from the Atar (S4 drill core) and El Mreiti groups (S2 and S3 drill cores). This study focuses on whole-rock elemental geochemistry and Sm/Nd isotope compositions to provide insights into the provenance of the fine-grained siliciclastic sediments from the basal part of the Mesoproterozoic Atar and El Mreiti groups. Paleoweathering indices reveal a moderate degree of chemical weathering in the source areas, consistent with the low compositional maturity of the studied samples. The concentrations of the relatively immobile trace elements suggest mixing sources of sediment provenance, which is dominated by felsic source rocks for the Atar sediments. However, distinctively positive ƐNd(t) values coupled with high 143Nd/144Nd and Sm/Nd ratios and high ƒSm/Nd values of the sediments from the El Mreiti Group indicate derivation from juvenile and less evolved sources rocks. Further, the depleted mantle model ages (TDM) of the provenance protolith (1.95–2.31 Ga) support the argument that the El Mreiti sediments are dominantly sourced from the Paleoproterozoic terrane exposed in the eastern Reguibat Shield while the Atar Group were predominantly from the Archean basement rocks in the western Reguibat Shield. Moreover, Sm/Nd isotope and mixing model results support the major contributions of the felsic Archean rocks of the Reguibat Shield for the Atar Group samples. Although these strata, separated by ∼1000 km, have been described as stratigraphic equivalent, our study demonstrates distinct sediment sources between the Atar Group strata and those of El Mreiti, therefore, reinforcing the importance of sediment provenance in understanding the evolution and reconstruction of modern and ancient sedimentary systems.
- Published
- 2023
3. Giving some tooth to Precambrian carbonates and the tales they tell about ancient oceans
- Author
-
Timothy W. Lyons, Chenyi Tu, and Leanne Hancock
- Subjects
Atmospheric Science ,Ecology ,Paleontology ,Soil Science ,Forestry ,Aquatic Science ,Water Science and Technology - Abstract
Enigmatic is a word that often comes up in discussions about Proterozoic molar tooth carbonate structures (MTS). But when unusual features such as these are common in rocks of a particular age, there is almost always an important message waiting to be discovered. In this case, the observed temporal patterns for MTS likely track first-order trends in evolving compositions in the oceans during Earth’s middle history when CO in the atmosphere and carbonate saturation in the ocean were high but declining and oxygen (O) in the ocean-atmosphere system was on the rise. A new paper by Tang et al. (this volume) gives us a new way to think about MTS origins, and nested within their model are wide ranging implicit and explicit linkages to Earth surface evolution as life was becoming more complex in a slow march toward the world we know today.
- Published
- 2023
4. Post-depositional transformations in sedimentary rocks and implications for paleoenvironmental studies: evidence from the Mesoproterozoic (∼1.1 Ga) of the Taoudeni Basin, Mauritania
- Author
-
Mohamed Ghnahalla, Abderrazak El Albani, Ahmed Abd Elmola, Olabode M. Bankole, Claude Fontaine, Mohamed Salem Sabar, Alain Trentesaux, Claude Laforest, Alain Meunier, Celine Boissard, Chenyi Tu, Timothy W. Lyons, Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Faculté des Sciences et Techniques [Nouakchott, Mauritania], Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Nord]), Department of Earth Sciences [University of Southern California], and University of Southern California (USC)
- Subjects
Redox ,Mesoproterozoic ,Geochemistry ,General Earth and Planetary Sciences ,Paleoenvironments ,Mineralogy ,[SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology ,Mauritania - Abstract
International audience; Understanding paleoenvironmental dynamics linked to biological evolution in Earth history is a major goal within the geological community. The difficulty of achieving this goal, at least in part, lies with the secondary transformations experienced by a majority of ancient rocks, especially through metamorphism and hydrothermal activity. The Mesoproterozoic (∼1.1 Ga) shallow-marine deposits from the Taoudeni Basin, Mauritania, have suffered a complex, multiphase tectonic, and thermal evolutionary history. Representative samples from two drill cores (a background site [S2] and a dolerite intrusion-bearing drill core [S1]) from the El Mreiti Group were evaluated for transformations and overprints of original mineralogies and geochemical compositions. Our results show that the drill core hosting the dolerite intrusion (S1) is characterized by a suite of minerals (that is, pyroxene, graphite, pyrrhotite, garnet, zeolite, and authigenic clay minerals) resulting from contact metamorphism and associated hydrothermal activity. However, compared to the S1, the S2 core shows no evidence of post-depositional transformation. The geochemical data obtained from S1 reveal a striking elevation of iron contents likely delivered from the hydrothermal fluids. Moreover, concentrations of redox-sensitive trace elements (molybdenum, uranium, and vanadium) increased dramatically during hydrothermal and metamorphic activity. This study demonstrates that need for caution when assessing paleoenvironmental conditions in ancient sedimentary rocks, particularly for iron and trace metal approaches commonly used in reconstructions of paleo-redox.
- Published
- 2022
5. Impact of post-depositional transformation on sedimentary rocks and implications for paleoenvironmental studies: Evidence from Mesoproterozoic (1.1 Ga) sediments from the Taoudeni basin, Mauritania
- Author
-
Mohamed Ghnahalla, Abderrazak El Albani, Ahmed Abd Elmola, Olabode M. Bankole, Claude Fontaine, Timothy W. Lyons, Chenyi Tu, Mohamed Salem Sabar, Alain Trentesaux, and Alain Meunier
- Abstract
Understanding and reconstruction of the paleo-condition dynamics linked to biological evolution in Earth history remain a big challenge because a majority of the ancient rocks have been affected by secondary modification processes, including tectonic, metamorphic, and hydrothermal activities. This study examines the influence of magmatic intrusion on sediment composition and paleo-environmental reconstruction from two drill cores (S1 and S2) drilled into the shallow-marine Mesoproterozoic (~1.1 Ga) El Mreiti Group of northeast Taoudeni Basin, Mauritania. Petrographic and mineralogical data show that the S1 drill core, intruded by dolerite sill, consists of a series of metamorphic minerals, including pyroxene, graphite, pyrrhotite, garnet, zeolite, talc, and saponite in sediments within the contact aureoles of the dolerite sill, indicating the influence of contact metamorphism and associated hydrothermal activities. The dominance of low-temperature minerals and the absence of metamorphic minerals in the S2 drill core sediments demonstrate that they are largely preserved and were only affected by high-grade diagenetic modifications. The anomalous enrichments of the Fe and redox-sensitive trace elements (RSTEs) in sediments within the vicinity of the dolerite sill coincide with increasing pyrrhotite contents, suggesting the transfer and remobilization of the RSTEs via thermal decomposition of pyrite to pyrrhotite during metamorphism and hydrothermal processes at elevated temperatures. This is supported by the absence of hematite, low Th/U ratios, and increasing Eu anomaly values in the dolerite sill and contact aureoles. This study reinforces the importance of screening and assessment of samples for post-depositional alteration effects before being used for the reconstruction of paleo-redox conditions in modern and ancient sedimentary rocks.
- Published
- 2022
6. Progressive expansion of seafloor anoxia in the Middle to Late Ordovician Yangtze Sea: Implications for concurrent decline of invertebrate diversity
- Author
-
Junpeng Zhang, Chao Li, Xiang Fang, Wenjie Li, Yiying Deng, Chenyi Tu, Thomas J. Algeo, Timothy W. Lyons, and Yuandong Zhang
- Subjects
Geophysics ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) - Published
- 2022
7. Co-evolving Redox and Ecosystem Structures in the Early Oceans: Probing the Earliest Environmental Controls and Consequences of Complex Life
- Author
-
Chenyi Tu, Mohamed Ghnahalla, Abderrazak El Albani, and Timothy Lyons
- Published
- 2022
8. Proterozoic sulfur isotope excursions driven by systematic changes in sulfur isotopic composition of volcanic outgassing
- Author
-
James Eguchi, Timothy Lyons, and Chenyi Tu
- Published
- 2022
9. Environmental drivers of the first major animal extinction across the Ediacaran White Sea-Nama transition.
- Author
-
Evans, Scott D., Chenyi Tu, Rizzo, Adriana, Surprenant, Rachel L., Boan, Phillip C., McCandless, Heather, Marshall, Nathan, Shuhai Xiao, and Droser, Mary L.
- Subjects
- *
BIOLOGICAL extinction , *EDIACARAN fossils , *ECOLOGICAL disturbances , *MASS extinctions , *COMMUNITIES - Abstract
The Ediacara Biota--the oldest communities of complex, macroscopic fossils--consists of three temporally distinct assemblages: the Avalon (ca. 575-560 Ma), White Sea (ca. 560-550 Ma), and Nama (ca. 550-539 Ma). Generic diversity varies among assemblages, with a notable decline at the transition from White Sea to Nama. Preservation and sampling biases, biotic replacement, and environmental perturbation have been proposed as potential mechanisms for this drop in diversity. Here, we compile a global database of the Ediacara Biota, specifically targeting taphonomic and paleoecological characters, to test these hypotheses. Major ecological shifts in feeding mode, life habit, and tiering level accompany an increase in generic richness between the Avalon and White Sea assemblages. We find that ~80% of White Sea taxa are absent from the Nama interval, comparable to loss during Phanerozoic mass extinctions. The paleolatitudes, depositional environments, and preservational modes that characterize the White Sea assemblage are well represented in the Nama, indicating that this decline is not the result of sampling bias. Counter to expectations of the biotic replacement model, there are minimal ecological differences between these two assemblages. However, taxa that disappear exhibit a variety of morphological and behavioral characters consistent with an environmentally driven extinction event. The preferential survival of taxa with high surface area relative to volume may suggest that this was related to reduced global oceanic oxygen availability. Thus, our data support a link between Ediacaran biotic turnover and environmental change, similar to other major mass extinctions in the geologic record. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
10. A late Paleoproterozoic microfossil community from siliceous granules, Dahongyu Formation, North China
- Author
-
Yinghao Jing, Zhong-Qiang Chen, and Chenyi Tu
- Subjects
Geochemistry and Petrology ,Geology - Published
- 2022
11. Biosedimentological features of major microbe-metazoan transitions (MMTs) from Precambrian to Cenozoic
- Author
-
Zhong-Qiang Chen, Yuheng Fang, Siqu Wu, Hao Yang, Yu Pei, Chenyi Tu, Yuangeng Huang, Xueqian Feng, James G. Ogg, and Zhen Guo
- Subjects
Sponge reef ,Extinction event ,geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Early Triassic ,social sciences ,010502 geochemistry & geophysics ,01 natural sciences ,Devonian ,Paleontology ,Phanerozoic ,Ordovician ,General Earth and Planetary Sciences ,Late Devonian extinction ,Reef ,Geology ,0105 earth and related environmental sciences - Abstract
Biotic activities are involved in almost all sedimentation processes throughout the evolutionary history of life on our planet. However, deep-time organism-induced sedimentation and biosedimentary records remain unclear in terms of lithologic types, strata stacking patterns and possible controlling factors. We document biosedimentary features of major transitions from microbe-dominated switching to metazoan-dominated biosedimentary systems based on the global distributions of both microbial and metazoan carbonates through Precambrian to Phanerozoic times, with emphasis on sedimentary records from China. The compilation of 150 and 180 well-documented metazoan and microbial reefs, respectively, from China, reveals that metazoan reefs proliferated during the Middle Ordovician, Middle Devonian and Middle Permian, whereas microbial reefs were well developed during the Cambrian, Late Devonian and Early–Middle Triassic, plus a moderate development during the early Silurian. These stratigraphic abundances of metazoan and microbial carbonates of China generally match the global patterns. The updated variation trends of microbial and metazoan carbonates throughout the late Precambrian and Phanerozoic reveal that there were five major microbe-metazoan transitions (MMTs): the late Ediacaran, the Cambrian, and the aftermaths of the mass extinctions of the end-Ordovician, Late Devonian, and end-Permian. The late Ediacaran MMT began with microbe-dominated oceans with occasional occurrences of metazoans. The presence of Cloudina-dominated reefs in the latest Ediacaran marks the completion of the switching of this microbe-dominated depositional system into a metazoan-dominated system. The Cambrian saw the expansion of skeletal microbes (i.e., Epiphyton, Renalcis) in the oceans; and the stratigraphic successions yield the most diverse biosedimentary deposits and/or structures of the entire Phanerozoic. The Cambrian MMT was the longest microbial-metazoan alternation period and is marked by two metazoan occurrence peaks marked by dominance of abundant archaeocyath buildups during its Epoch 2 and by maceriate and lithistid sponge reefs during the late Furongian Epoch. The early Silurian in China saw the deposition of a thick suite of organic-rich black shales followed by alternations of microbe-rich sediments (oil shales) and metazoan-bearing deposits, which are replaced by microbial and metazoan reefs during the late early Silurian. The Late Devonian MMT started during the late Frasnian and persisted into the early Mississippian, and thus extended slightly longer than the aftermath of the Frasnian–Famennian extinction interval. Alternating occurrences of microbial and metazoan reefs characterize this Late Devonian MMT. Almost all microbe-mediated sediments/structures observed in the Cambrian MMT reoccurred in the aftermath of the end-Permian mass extinction during the Early–Middle Triassic MMT, suggesting high similarities between those two MMTs. Cambrian and Early–Middle Triassic MMTs also share comparable carbon and sulfur isotopic perturbations, warming regimes, and generally oxygen-deficient seawaters. Some of these environmental and climatic extremes may also occur during other MMTs, but they usually did not occur synchronously. Most MMTs seem to have undergone four developmental stages. They initiated as microbe-dominated successions (Stage A), and then were characterized by alternations of microbe-dominated and of metazoan-bearing or bioturbated successions (Stage B). Both microbial and metazoan reefs co-occurred during Stage C; and a dominance of metazoan reefs marks the development of Stage D. Ediacaran and Cambrian MMTs seem to have undergone the first three development stages, whereas the three post-extinction MMTs experienced the full set of Stages A−D, corresponding to metazoan survival, initial recovery and full recovery. The majority of volatile-rich Large Igneous Provinces (LIPs), coupled with intensive acidification events, anoxia and global warming regimes, took place during the Mesozoic–Cenozoic. However, microbe-dominated sediments were only widely deposited during the Early Triassic, and greatly declined after that time. Therefore, it seems that microbial abundance in MMTs may not be directly related to these extreme LIP events. This is probably because a primary source of food for the metazoans might have shifted to phytoplankton (e.g., coccoliths, dinoflagellates, and radiolarians) in the marine waters since the Triassic. Certainly, the pre-Mesozoic oceans were not dominated by phytoplankton. Perturbations in the carbon isotope record characterize all MMTs, and thus may be reliable proxies indicating MMT biosedimentary systems.
- Published
- 2019
12. Unusual shallow marine matground-adapted benthic biofacies from the Lower Triassic of the northern Paleotethys: Implications for biotic recovery following the end-Permian mass extinction
- Author
-
Guang Rong Shi, Xueqian Feng, Yaling Xu, Yuangeng Huang, David J. Bottjer, Chenyi Tu, Siqi Wu, Zhong-Qiang Chen, Yuheng Fang, and Laishi Zhao
- Subjects
Diplocraterion ,010504 meteorology & atmospheric sciences ,biology ,Lower shoreface ,Early Triassic ,010502 geochemistry & geophysics ,biology.organism_classification ,01 natural sciences ,Rosselia ,Paleontology ,Benthic zone ,General Earth and Planetary Sciences ,Siliciclastic ,Microbial mat ,Geology ,Permian–Triassic extinction event ,0105 earth and related environmental sciences - Abstract
We report two shallow marine, ichnofauna-bivalve-microbial mat biofacies from the Lower Triassic Xiahuancang Formation of the southern Qilian area, Qinghai Province, northwestern China, which was located at moderate-high paleolatitudes on the northern margin of the Paleotethys Ocean. Paleoenvironmental analyses show that Members I and II of the Xiahuancang Formation represent a shoreface and a lower shoreface to offshore transition setting, respectively. Biofacies 1, recognized from Member I, is characterized by a diverse ichnofauna (including deep-tiers of Rosselia and Diplocraterion), Claraia-dominated bivalves, and microbially induced sedimentary structures (MISSs). Biofacies 2, in succeeding Member II, is dominated by a diverse ichnofauna, epifaunal and shallow infaunal bivalves, and wrinkle structures. Primary co-occurrences, preservational features, and palimpsest or crosscutting relationships of all components within the biofacies indicate that microbial mats, bivalves, and trace-makers actively interacted with one another during deposition. They largely represent contemporaneous biotic associations. Microbial mats are interpreted to have grown under well-oxygenated conditions after storm deposition due to the association of deep-tiering infauna and diverse epifauna as well as well-developed cross-stratification, and the top layer of microbial mats could serve as an oasis for metazoans. Microbial mats not only proliferated in harsh environments, but also coexist with epifauna and deep-tiering infauna in well-oxygenated settings following the end-Permian crisis. Their occurrences in the Early Triassic are unrelated to environmental stresses, which are coincident with their sedimentologic record from other geological time intervals. Apparently, the southern Qilian ichnofauna-bivalve-microbial mat biofacies with juxtaposed epifauna, infauna and MISS- or wrinkle-related microbial mats represents a matground-adapted benthic metazoan ecosystem in the earliest Triassic, which provided sufficient oxygen, food, and other hydrodynamic conditions hospitable for metazoans and ecosystems to recover and reached a fairly high level (recovery stage 3) in a tough time when most biotas suffered biotic depletion and environmental stress. The biotic components in unique biofacies may represent a phase shift community in siliciclastic settings during the Early Triassic.
- Published
- 2019
13. LOST IN TRANSITION: EXAMINING CAUSES OF BIOTIC TURNOVER IN THE EDIACARAN
- Author
-
Shuhai Xiao, Mary L. Droser, Nathan Marshall, Phillip Boan, Adriana Rizzo, Chenyi Tu, Rachel L. Surprenant, Scott D. Evans, and Heather McCandless
- Subjects
Chemistry ,Ecology - Published
- 2021
14. DYNAMIC EVOLUTION OF MARINE CHEMISTRY LINKED TO WAX AND WANE OF THE GLACIATIONS IN A RESTRICTED CRYOGENIAN BASIN
- Author
-
Charles W. Diamond, Eva Stueeken, Chenyi Tu, and Timothy W. Lyons
- Subjects
Paleontology ,Wax ,visual_art ,visual_art.visual_art_medium ,Structural basin - Published
- 2021
15. Proliferation of MISS-related microbial mats following the end-Permian mass extinction in the northern Paleo-Tethys: Evidence from southern Qilianshan region, western China
- Author
-
Xueqian Feng, Chenyi Tu, Yaling Xu, Zhong-Qiang Chen, Guang Rong Shi, and Siqi Wu
- Subjects
Extinction event ,Ripple marks ,010504 meteorology & atmospheric sciences ,Paleontology ,Trace fossil ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Sedimentary structures ,Clastic rock ,Siliciclastic ,Microbial mat ,Ecology, Evolution, Behavior and Systematics ,Geology ,Permian–Triassic extinction event ,0105 earth and related environmental sciences ,Earth-Surface Processes - Abstract
As a consequence of the end-Permian mass extinction, microbes proliferated in the post-extinction shallow marine ecosystems, in which they grew as various microbially induced sedimentary structures (MISSs) in siliciclastic settings. This paper reports, for the first time, the discovery of abundant MISSs from the lowest Triassic sandstones of shallow-water margin origin in the Zhihema sections of the southern Qilianshan region, West China. The sandstones are characterized by well-developed cross-beddings and ripple marks, and a Claraia-dominated bivalve assemblage of middle-late Griesbachian age. These sedimentary structures, together with the bivalves, suggest a high-energy peritidal zone of a shoreface setting in a clastic shallow sea environment. Seven types of MISSs are recognized and described here: pictograph-like sand cracks/crack-fills, polygonal sand crack-fills, erosional remnants, multidirectional linear grooves, sinuous crack-fills, fusiform sand cracks/crack-fills, and leveled ripple marks. Most of the newly found MISSs are morphologically comparable with their ancient and modern counterparts. Detailed optical microscope and scanning electron microscope (SEM) analyses reveal that thin clayey laminae and filamentous mica grains are aligned parallel to bedding plane, and that the matrix-supported quartz grains, overall, are oriented; both of which are interpreted to indicate biogenic origin. The biogenic origin of these MISSs is reinforced by the presence of copious putative nanoglobules and filamentous biofilm-like organic objects in the interspaces of clay minerals in laminated layers. These nanometer-scale objects are interpreted as bacterial bodies or remains that have been replaced with inorganic minerals upon fossilization. The presence of MISSs on the northern margins of Paleo-Tethys indicates that the post-extinction microbial mats had expanded their distributions from low-latitude to moderate-high latitude regions. Moreover, unlike some previously reported microbial mats that contain very rare body and trace fossils, the southern Qilianshan MISSs were found in association with abundant vertical burrows and bivalves, suggesting that the MISS-forming microbial mats may have served as oases for trace-making organisms and opportunistic bivalves to flourish in shallow-marine habitats immediately after the end-Permian mass extinction.
- Published
- 2017
16. Proliferation of MISS-related microbial mats following the end-Permian mass extinction in terrestrial ecosystems: Evidence from the Lower Triassic of the Yiyang area, Henan Province, North China
- Author
-
Gregory J. Retallack, Yuheng Fang, Yuangeng Huang, Chenyi Tu, and Zhong-Qiang Chen
- Subjects
Extinction event ,010506 paleontology ,Stratigraphy ,Early Triassic ,Geology ,010502 geochemistry & geophysics ,01 natural sciences ,Sedimentary structures ,Paleontology ,Sedimentary rock ,Marine ecosystem ,Siliciclastic ,Terrestrial ecosystem ,Permian–Triassic extinction event ,0105 earth and related environmental sciences - Abstract
Microbially induced sedimentary structures (MISSs) are commonly present in siliciclastic shallow marine settings following the end-Permian mass extinction, but have been rarely reported in the post-extinction terrestrial ecosystems. Here, we present six types of well-preserved MISSs from the upper Sunjiagou Formation and lower Liujiagou Formation of Induan (Early Triassic) age in the Yiyang area, Henan Province, North China. These MISSs include: polygonal sand cracks, worm-like structures, wrinkle structures, sponge pore fabrics, gas domes, and leveled ripple marks. Microanalysis shows that these MISSs are characterized by thin clayey laminae and filamentous mica grains arranged parallel to bedding plane as well as oriented matrix supported quartz grains, which are indicative of biogenic origin. Facies analysis suggests that the MISS-hosting sediments were deposited in a fluvial sedimentary system during the Early Triassic, including lake delta, riverbeds/point bars, and flood plain paleoenvironments. Abundant MISSs from Yiyang indicate that microbes also proliferated in terrestrial ecosystems in the aftermath of the Permian–Triassic (P–Tr) biocrisis, like they behaved in marine ecosystems. Microbial blooms, together with dramatic loss of metazoans, may reflect environmental stress and degradation of terrestrial ecosystems or arid climate immediately after the severe Permian–Triassic ecologic crisis.
- Published
- 2016
17. MAGNETOSTRATIGRAPHY OF THE CONTINENTAL REFERENCE SECTION FOR LATEST PERMIAN THROUGH EARLY TRIASSIC OF NORTH CHINA AT DAYULIN (HENAN PROVINCE)
- Author
-
Yang Wendy Zhang, Mingsong Li, Dao liang Chu, Zhong-Qiang Chen, Yan Chen, James G. Ogg, and Chenyi Tu
- Subjects
Paleontology ,Permian ,Section (archaeology) ,Early Triassic ,North china ,Geology ,Magnetostratigraphy - Published
- 2017
18. Permian–Triassic evolution of the Bivalvia : extinction-recovery patterns linked to ecologic and taxonomic selectivity
- Author
-
Zhong-Qiang Chen, Chenyi Tu, and David A. T. Harper
- Subjects
Extinction event ,010506 paleontology ,Extinction ,Permian ,Ecology ,Early Triassic ,Paleontology ,Ladinian ,social sciences ,Evolutionary fauna ,Biology ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Mesozoic marine revolution ,Origination ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences ,Earth-Surface Processes - Abstract
The Bivalvia is an important benthic clade that was relatively less affected than other benthos during the Permian–Triassic (P–Tr) biotic crisis, reporting losses of 85%, 64%, and 32% at the species, genus and family levels, respectively. This clade proliferated immediately after the P–Tr mass extinction (PTME) to become one of the key elements of the ‘Modern Evolutionary Fauna’ following the P–Tr ‘Great Dying’. Global bivalve occurrence data demonstrate that the initial recovery started in the Griesbachian, a substage immediately after the PTME, and are characterized by relatively high origination and low extinction rates. Thus, unlike other fossil groups, bivalves did not significantly engage in the survival interval. The initial Griesbachian recovery is followed by a stepwise recovery during the Dienerian to Spathian. Then, a remarkably rapid radiation occurred in the Anisian, indicated by extremely high proportional origination and extinction rates. Infaunalization has long been considered the most significant adaptation during the Mesozoic Marine Revolution (MMR), which was thought to have commenced in the Early–Middle Triassic. However, the proportion of infauna in communities remained virtually unchanged before and after the P–Tr biotic crisis; additionally there was no significant difference in proportional extinction/origination rates between infaunal and epifaunal taxa at the genus and family levels through the entire P–Tr transition, implying the absence of ecological selectivity, a conclusion that differs from some previous studies. Therefore, if escalating predatory pressure indeed played a crucial role in driving the initial phases of the MMR, infaunalization was not marked prior to the Ladinian. Alternatively, infaunalization may have played a minor role in facilitating the MMR during the entire era. If so, changes in the physical and chemical environment (‘Court Jester’ model) (i.e. amelioration of marine environments in late Early Triassic), rather than biotic processes (‘Red Queen’ model), may be crucial for the origination and initial phases of the MMR during the early Mesozoic.
- Published
- 2016
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.