Thesis: Recovery of marine ecosystems following the end-Permian mass extinction: Evidence from Early Triassic biogenic structures in South China
The Permian/Triassic (P/Tr) mass extinction was the largest Phanerozoic extinction that severely impacted biodiversity (Bambach et al., 2004), and profoundly degraded marine ecosystems to be characterized by high abundance, low diversity metazoan communities (Bottjer et al., 2008). Biotic recovery after the P/Tr crisis has been interpreted to have been slow due to devastating environmental conditions prevailing in Early Triassic oceans, e.g. anoxia and euxinia that spread across many marine basins (Isozaki, 1997; Wignall and Twitchett, 2002; Bottjer et al., 2008). Accordingly, the recovery of the devastated ecosystems has attracted an increasing number of multidisciplinary studies (Twitchett, 1999, 2006; Payne et al., 2004; Chen et al., 2010a, 2010b).
The use of biogenic structures, such as trace fossils, as proxies for marine ecosystem recovery has great utility. Trace fossils are morphologically recurrent structures resulting from the life activity of an individual organism modifying the substrate (Bertling et al., 2006). They are not able to be transported, and can, therefore be used to interprete depositional environments (Mata and Bottjer, 2011). Furthermore, post-extinction macrofaunas were unevenly distributed and are poorly preserved (Fraiser and Bottjer, 2005) during the Early Triassic, whereas trace fossils and various microbial mats are widely preserved in different depositional settings, especially in South China. During the previous 15years, several recent ichnological studies have greatly enhanced understanding of ecologic recovery following the P/Tr mass extinction (Twitchett and Wignall, 1996; Twitchett, 1999; Twitchett ana Barras, 2004; Pruss and Bottjer, 2004; Beatty et al., 2008; Fraiser and Bottjer, 2009; Zonneveld et al., 2010; Chen et al., 2011). However, most of the trace fossil-based studies concerning the Early Triassic ecologic recovery are based on studies from North America (Twitchett and Barras, 2004; Pruss and Bottjer, 2004; Fraiser and Bottjer, 2009), the western Tethys (Twitchett and Wignall, 1996; Twitchett, 1999), or northern high-latitute regions (Wignall et al., 1998; Beatty et al., 2008; Zonneveld et al., 2010). Less work has been published on the trace fossils from South China relating to their responses to extinctions and recovery (Luo et al., 2007; Zhao and Tong, 2010; Chen et al., 2011).
Thus, understanding the trace fossil assemblage rebounding patterns and the relationships between trace fossils and biosedimentary structures in different depostional settings in Early Triassic successions in South China will help evaluate marine ecosystem recovery following the P/Tr crisis and potential factors causing the long-delayed biotic recovery. Interpretation of the origin of these biosedimentary structures will give insight into the environmental conditions and oceanic chemistry of the recovery interval.
Why my research is important
This research will help document the recovery pattern of marine ecosystems following the end-Permian mass extinction and to test the role of post-extinction opportunistic organisms in rebuilding the food web by examing the fossil record in the Early Triassic successions in South China.