6533b838fe1ef96bd12a4e4c

RESEARCH PRODUCT

Early Triassic proliferation of microbial deposit

subject

description

International audience; In modern examples of well-developed microbial-dominated deposits associated with metazoan organisms can be currently found in various environments including but not restricted to lagoons in Polynesia (Sprachta et al., 2001), the warm water of the Cuba (e.g., Bouton et al., 2016; Pace et al., 2018), the hypersaline lakes of the Great Salt Lake (USA; e.g., Bouton et al., 2016; Vennin et al., 2019; Vanden Berg, 2019), or the alkaline Satonda Crater Lake in Indonesia (Arp et al., 2003; Satuyana et al., 2010). In Early Triassic, several authors indicated that microbial deposits are frequently associated with sponges, bivalves, brachiopods, ostracods and echinoderms and developed in normal marine conditions (Schubert and Bottjer, 1992; Brayard et al., 2011; Oliver et al., 2014, 2018; Collin et al., 2015; Vennin et al., 2015; Fang et al., 2017; Jeffrey et al., 2019). The environmental significance of the Early Triassic microbial deposits and the controlling factors behind their presence thus remains an open question (e.g., Vennin et al., 2015 and Olivier et al., 2016). Therefore, microbial deposits are not always characteristic of deleterious and/or post-crisis environments as commonly previously thought (e.g., Flügel, 2002; Riding, 2006). Microbial systems have been present throughout most of the Phanerozoic, either associated or not with metazoan organisms (e.g., Riding, 2006). Their development may follow mass extinction events (e.g., Late Ordovician or end-Permian), but this is not always observed (Riding et al., 2019). Deciphering interactions between microbial deposits and their environments is therefore crucial to understand the Early Triassic recovery dynamics. We aim (1) to document an extensive Lower Triassic microbial and associated metazoans development across the Sonoma Foreland basin (USA); (2) to propose a stratigraphical framework documenting changes in the relative seawater, and (3) to interpret regional environmental influences on microbial deposits.