@article{WangFosterYanetal.2019, author = {Wang, Xiaoxi and Foster, William J. and Yan, J. and Li, A. and Mutti, Maria}, title = {Delayed recovery of metazoan reefs on the Laibin-Heshan platform margin following the Middle Permian (Capitanian) mass extinction}, series = {Global and planetary change}, volume = {180}, journal = {Global and planetary change}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0921-8181}, doi = {10.1016/j.gloplacha.2019.05.005}, pages = {1 -- 15}, year = {2019}, abstract = {Following the Middle Permian (Capitanian) mass extinction there was a global 'reef eclipse', and this event had an important role in the Paleozoic-Mesozoic transition of reef ecosystems. Furthermore, the recovery pattern of reef ecosystems in the Wuchiapingian of South China, before the radiation of Changhsingian reefs, is poorly understood. Here, we present a detailed sedimentological account of the Tieqiao section, South China, which records the only known Wuchiapingian reef setting from South China. Six reef growing phases were identified within six transgressive-regressive cycles. The cycles represent changes of deposition in a shallow basin to a subtidal outer platform setting, and the reefal build-ups are recorded in the shallowest part of the cycles above wave base in the euphotic zone. Our results show that the initial reef recovery started from the shallowing up part of the 1st cycle, within the Clarkina leveni conodont zone, which is two conodont zones earlier than previously recognized. In addition, even though metazoans, such as sponges, do become important in the development of the reef bodies, they are not a major component until later in the Wuchiapingian in the 5th and 6th transgressive-regressive cycles. This suggests a delayed recovery of metazoan reef ecosystems following the Middle Permian extinction. Furthermore, even though sponges do become abundant within the reefs, it is the presence and growth of the encrusters Archaeolithoporella and Tubiphytes and abundance of microbial micrites that play an important role in stabilizing the reef structures that form topographic highs.}, language = {en} } @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} }