Facies and evolution of the carbonate factory during the Permian-Triassic crisis in South Tibet, China
Facies and evolution of the carbonate factory during the Permian-Triassic crisis in South Tibet, China
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DOI：
10.1111/sed.12619
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发表时间：
2019-12-01
期刊：
影响因子：
3.5
通讯作者：
Wignall, Paul B.
中科院分区：
文献类型：
--
作者：
Li, Mingtao;Song, Haijun;Wignall, Paul B.
古生代碳酸盐工厂的性质强烈地受碳酸盐生产动物群的组成所控制。在二叠纪-三叠纪生物大灭绝期间，热带浅台地相发生了重大变化：上二叠统生物碎屑灰岩的特征是底栖生物群落丰富，例如，钙质藻类，fusulinids，腕足动物，珊瑚，软体动物和海绵，而最低的三叠纪碳酸盐岩在二叠纪-三叠纪生物大灭绝之后立即转变为以细菌为主的微生物岩。然而，高纬度地区碳酸盐岩分布的时空格局，以响应二叠纪-三叠纪生物大绝灭很少受到关注。本文根据藏南地区二叠纪-三叠纪界线剖面近缘、内远缘和外斜坡剖面，研究了冈瓦纳周北方边缘（古纬度约40 ° S）碳酸盐岩工厂的沉积相和演化模式。结果表明，藏南晚二叠世发育一个以冷水苔藓虫和棘皮动物为主的碳酸盐岩斜坡。这是突然取代后，立即二叠纪-三叠纪大规模灭绝，底栖automicrite工厂与少量的钙化后生动物开发的内/中斜坡设置，伴随着短暂的陆上曝光。随后，在藏南早三叠世发育了一个广泛的同斜碳酸盐斜坡，主要由均匀的绿泥质灰泥岩/砂岩组成，缺乏后生动物框架建造者的证据。从冷水，异源动物占主导地位的碳酸盐斜坡的突然过渡到温水，后生动物，同温层碳酸盐斜坡以下的二叠纪-三叠纪大规模灭绝是后生动物礁/丘建设者的损失，整个二叠纪-三叠纪大规模灭绝和深刻的全球变暖在早三叠世的快速海平面变化的组合的结果。
The nature of Phanerozoic carbonate factories is strongly controlled by the composition of carbonate-producing faunas. During the Permian-Triassic mass extinction interval there was a major change in tropical shallow platform facies: Upper Permian bioclastic limestones are characterized by benthic communities with significant richness, for example, calcareous algae, fusulinids, brachiopods, corals, molluscs and sponges, while lowermost Triassic carbonates shift to dolomicrite-dominated and bacteria-dominated microbialites in the immediate aftermath of the Permian-Triassic mass extinction. However, the spatial-temporal pattern of carbonates distribution in high latitude regions in response to the Permian-Triassic mass extinction has received little attention. Facies and evolutionary patterns of a carbonate factory from the northern margin of peri-Gondwana (palaeolatitude ca 40 degrees S) are presented here based on four Permian-Triassic boundary sections that span proximal, inner to distal, and outer ramp settings from South Tibet. The results show that a cool-water bryozoan-dominated and echinoderm-dominated carbonate ramp developed in the Late Permian in South Tibet. This was replaced abruptly, immediately after the Permian-Triassic mass extinction, by a benthic automicrite factory with minor amounts of calcifying metazoans developed in an inner/middle ramp setting, accompanied by transient subaerial exposure. Subsequently, an extensive homoclinal carbonate ramp developed in South Tibet in the Early Triassic, which mainly consists of homogenous dolomitic lime mudstone/wackestone that lacks evidence of metazoan frame-builders. The sudden transition from a cool-water, heterozoan dominated carbonate ramp to a warm-water, metazoan-free, homoclinal carbonate ramp following the Permian-Triassic mass extinction was the result of the combination of the loss of metazoan reef/mound builders, rapid sea-level changes across Permian-Triassic mass extinction and profound global warming during the Early Triassic.