@article{FosterLehrmannYuetal.2019, author = {Foster, William J. and Lehrmann, Daniel J. and Yu, Meiyi and Martindale, Rowan C.}, title = {Facies selectivity of benthic invertebrates in a Permian/Triassic boundary microbialite succession: Implications for the "microbialite refuge" hypothesis}, series = {Geobiology}, volume = {17}, journal = {Geobiology}, number = {5}, publisher = {Wiley}, address = {Hoboken}, issn = {1472-4677}, doi = {10.1111/gbi.12343}, pages = {523 -- 535}, year = {2019}, abstract = {Thrombolite and stromatolite habitats are becoming increasingly recognized as important refuges for invertebrates during Phanerozoic Oceanic Anoxic Events (OAEs); it is posited that oxygenic photosynthesis by cyanobacteria in these microbialites provided a refuge from anoxic conditions (i.e., the "microbialite refuge" hypothesis). Here, we test this hypothesis by investigating the distribution of ~34, 500 benthic invertebrate fossils found in ~100 samples from a microbialite succession that developed following the latest Permian mass extinction event on the Great Bank of Guizhou (South China), representing microbial (stromatolites and thrombolites) and non-microbial facies. The stromatolites were the least taxonomically diverse facies, and the thrombolites also recorded significantly lower diversities when compared to the non-microbial facies. Based on the distribution and ornamentation of the bioclasts within the thrombolites and stromatolites, the bioclasts are inferred to have been transported and concentrated in the non-microbial fabrics, that is, cavities around the microbial framework. Therefore, many of the identified metazoans from the post-extinction microbialites are not observed to have been living within a microbial mat. Furthermore, the lifestyle of many of the taxa identified from the microbialites was not suited for, or even amenable to, life within a benthic microbial mat. The high diversity of oxygen-dependent metazoans in the non-microbial facies on the Great Bank of Guizhou, and inferences from geochemical records, suggests that the microbialites and benthic communities developed in oxygenated environments, which disproves that the microbes were the source of the oxygenation. Instead, we posit that microbialite successions represent a taphonomic window for exceptional preservation of the biota, similar to a Konzentrat-Lagerstatte, which has allowed for diverse fossil assemblages to be preserved during intervals of poor preservation.}, language = {en} } @article{FosterHeindelRichozetal.2019, author = {Foster, William J. and Heindel, Katrin and Richoz, Sylvain and Gliwa, Jana and Lehrmann, Daniel J. and Baud, Aymon and Kolar-Jurkovsek, Tea and Aljinovic, Dunja and Jurkovsek, Bogdan and Korn, Dieter and Martindale, Rowan C. and Peckmann, J{\"o}rn}, title = {Suppressed competitive exclusion enabled the proliferation of Permian/Triassic boundary microbialites}, series = {The Depositional Record : the open access journal of the International Association of Sedimentologists}, volume = {6}, journal = {The Depositional Record : the open access journal of the International Association of Sedimentologists}, number = {1}, publisher = {Wiley}, address = {Hoboken}, issn = {2055-4877}, doi = {10.1002/dep2.97}, pages = {62 -- 74}, year = {2019}, abstract = {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 Earlandia. 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.}, language = {en} }