Permian-Triassic boundary microbialites (PTBMs) in soutwest China: implications for paleoenvironment reconstruction

Permian–Triassic boundary microbialites (PTBMs) are commonly interpreted to be a sedimentary response to upwelling of anoxic alkaline seawater and indicate a harsh marine environment in the Permian–Triassic transition. However, recent studies propose that PTBMs may instead be developed in an oxic environment, therefore necessitating the need to reassess the paleoenvironment of formation of PTBMs. This paper is an integrated study of the PTBM sequence at Yudongzi, northwest Sichuan Basin, which is one of the thickest units of PTBMs in south China. Analysis of conodont biostratigraphy, mega- to microscopic microbialite structures, stratigraphic variations in abundance and size of metazoan fossils, and total organic carbon (TOC) and total sulfur (TS) contents within the PTBM reveals the following results: (1) the microbialites occur mainly in the Hindeodus parvus Zone but may cross the Permian–Triassic boundary, and are comprised of, from bottom to top: lamellar thrombolites, dendritic thrombolites and lamellar-reticular thrombolites; (2) most metazoan fossils of the microbialite succession increase in abundance upsection, so does the sizes of bivalve and brachiopod fossils; (3) TOC and TS values of microbialites account respectively for 0.07 and 0.31 wt% on average, both of which are very low. The combination of increase in abundance and size of metazoan fossils upsection, together with the low TOC and TS contents, is evidence that the Yudongzi PTBMs developed in oxic seawater. We thus dispute the previous view, at least for the Chinese sequences, of low-oxygen seawater for microbialite growth, and question whether it is now appropriate to associate PTBMs with anoxic, harsh environments associated with the end-Permian extinction. Instead, we interpret those conditions as fully oxygenated.13th Five-Year Plan National Scientific and Technology Major Project (2016ZX05004002-001); National Natural Science Foundation of China (41602166)

Climate Change and Impacts on Biodiversity on Small Islands

The Pacific Islands region is a sensitive indicator of projected climate change in the twenty-first century. This chapter provides comprehensive information on climate change and how it impacts on biodiversity in the Pacific Island countries as it is ironically one of the most vulnerable regions in this regard. The islands of the Pacific region hold three of the 35 global biodiversity hotspots with large numbers of endemic species. The case study highlights the potential impacts of climate change on terrestrial vertebrate species found in 26 Pacific Island countries. The aim of this case study was to investigate the distribution of terrestrial vertebrate species across these countries and identify those species that were most at risk of extinction due to them being present on only one or a few islands that had previously been classified as being most susceptible to climatic change. The results show that 674 of the islands hosted at least one terrestrial vertebrate species that was either vulnerable, endangered, or critically endangered. A total of 84 terrestrial vertebrate species are endemic to this region, and many of them occupy one island only, increasing their chances of extinction