Foster William J, Heindel Katrin, Richoz Sylvain, Gliwa Jana, Lehrmann Daniel J, Baud Aymon, Kolar-Jurkovšek Tea, Aljinović Dunja, Jurkovšek Bogdan, Korn Dieter, Martindale Rowan C, Peckmann Jörn
Museum für Naturkunde Leibniz Institute for Research on Evolution and Biodiversity Berlin Germany.
Institute for Earth and Environmental Sciences University of Potsdam Potsdam-Golm Germany.
Depos Rec. 2020 Feb;6(1):62-74. doi: 10.1002/dep2.97. Epub 2019 Nov 20.
During the earliest Triassic microbial mats flourished in the photic zones of marginal seas, generating widespread microbialites. It has been suggested that anoxic conditions in shallow marine environments, linked to the end-Permian mass extinction, limited mat-inhibiting metazoans allowing for this microbialite expansion. The presence of a diverse suite of proxies indicating oxygenated shallow sea-water conditions (metazoan fossils, biomarkers and redox proxies) from microbialite successions have, however, challenged the inference of anoxic conditions. Here, the distribution and faunal composition of Griesbachian microbialites from China, Iran, Turkey, Armenia, Slovenia and Hungary are investigated to determine the factors that allowed microbialite-forming microbial mats to flourish following the end-Permian crisis. The results presented here show that Neotethyan microbial buildups record a unique faunal association due to the presence of keratose sponges, while the Palaeotethyan buildups have a higher proportion of molluscs and the foraminifera . The distribution of the faunal components within the microbial fabrics suggests that, except for the keratose sponges and some microconchids, most of the metazoans were transported into the microbial framework via wave currents. The presence of both microbialites and metazoan associations were limited to oxygenated settings, suggesting that a factor other than anoxia resulted in a relaxation of ecological constraints following the mass extinction event. It is inferred that the end-Permian mass extinction event decreased the diversity and abundance of metazoans to the point of significantly reducing competition, allowing photosynthesis-based microbial mats to flourish in shallow water settings and resulting in the formation of widespread microbialites.
在三叠纪最早期，微生物席在边缘海的光合带中繁盛，形成了广泛分布的微生物岩。有人提出，与二叠纪末大灭绝相关的浅海缺氧环境限制了抑制微生物席的后生动物，从而使得这种微生物岩得以扩张。然而，来自微生物岩序列的一系列表明浅海海水氧化条件的多样指标（后生动物化石、生物标志物和氧化还原指标）对缺氧条件的推断提出了挑战。在此，对来自中国、伊朗、土耳其、亚美尼亚、斯洛文尼亚和匈牙利的格里斯巴赫阶微生物岩的分布和动物群组成进行了研究，以确定二叠纪末危机后使形成微生物岩的微生物席得以繁盛的因素。此处给出的结果表明，由于角质海绵的存在，新特提斯洋的微生物礁记录了独特的动物群组合，而古特提斯洋的礁体中软体动物和有孔虫的比例更高。微生物结构中动物群组分的分布表明，除了角质海绵和一些微壳类动物外，大多数后生动物是通过海浪洋流被带入微生物框架的。微生物岩和后生动物组合的存在都局限于氧化环境，这表明除缺氧之外的某个因素导致了大灭绝事件后生态限制的放松。据推断，二叠纪末大灭绝事件降低了后生动物的多样性和丰度，以至于竞争显著减少，使得基于光合作用的微生物席在浅水环境中繁盛，并导致了广泛分布的微生物岩的形成。
