Taphonomic study of Ediacaran organic-walled fossils confirms the importance of clay minerals and pyrite in Burgess Shale−type preservation

Abstract

Stratigraphic Information Chuaria and Vendotaenia fossils used in this study came from the Ediacaran Doushantuo and Denying formations, respectively, in the Yangtze Gorges area of South China (Fig. DR1). The Doushantuo Formation includes four informal lithostratigraphic members (McFadden et al., 2009): in ascending order, Member I (~5m-thick cap dolostone atop the Nantuo diamictite), II (70-100 m of argillaceous/dolomitic pelletal packstone and calcareous mudstone/siltstone with chert nodules), III (50-80 m of dolomitic pelletal packstone and ribbon rock with scours, microbial laminations, and sheet cherts), and IV (up to 20 m of black shale or organic-rich mudstone). Previous studies have shown that abundant silicified microfossils are present in Member II chert nodules (Xiao et al., 2010), and carbonaceous compressions (including Chuaria fossils) are found in black shales of Member II (Tang et al., 2006) and Member IV (Xiao et al., 2002). We analyzed 16 Chuaria specimens collected at the Jiulongwan, Sixi, and Sifangtang sections (Fig. DR1) from Member II argillaceous packstone and calcareous siltstone/mudstone, which were deposited in lower subtidal environment in a semi-restricted basin (Ader et al., 2009). Available geochronological data constrain the analyzed Chuaria fossils between 632.5±0.5 Ma (Condon et al., 2005) and 593±17 Ma (Zhu et al., 2010).

A reexamination of Yuknessia from the Cambrian of British Columbia and Utah

“…Similar elemental compositions have been documented for non-biomineralizing fossils from Burgess Shale-type deposits, the material being preserved as carbonaceous compressions but including replication by clay minerals and overprinting by pyrite (e.g., Orr et al, 1998Orr et al, , 2009Gabbott et al, 2004;Hu, 2005;Zhu et al, 2005;Butterfield et al, 2007;Gaines et al, 2008;Page et al, 2008;Anderson et al, 2011;Cai et al, 2012;Meyer et al, 2012;Schiffbauer et al, 2014). The Utah material, however, seems to show a stronger iron overprint than non-biomineralized Burgess Shale material.…”

A unifying model for Neoproterozoic–Palaeozoic exceptional fossil preservation through pyritization and carbonaceous compression

“…While numerous other palaeoenvironmental and diagenetic considerations have been invoked for kerogenization, such as interactions with clays 6,16 or ferrous iron 17 , high alkalinity 15,18 and oxidant restriction (that is, lack of sulfate for BSR) through early diagenetic sealing 18 (though see also ref. 19), the common association of kerogenized fossils with pyrite 1,6,12,16,[20][21][22][23][24] bolsters the interrelationship of these taphonomic processes.…”

Beyond the stony veil: Reconstructing the Earth’s earliest large animal traces via computed tomography X-ray imaging

“…However, they do not appear on the microCT imagery though they are within the resolution of the detector. This could be due to low contrasting densities between the fossils and the matrix, especially if they are clay imprints rather than fully carbonaceous fossils (Anderson et al, 2011;Meyer et al, 2012Meyer et al, , 2016.…”

“…This is the most fossiliferous member of the Dengying Formation and contains numerous body and trace fossils. Body fossils include Vendotaenia (Anderson et al, 2011), Paracharnia (Sun, 1986), Yangtziramulus Xiao et al, 2005), Curviacus (Shen et al, 2017), Pteridinium and Rangea , as well as trace fossils such as Palaeophycus/Planolites, Helminthoidichnites, and Torrowangea (Weber et al, 2007;Zhao et al, 1988). The Shibantan Member at the collection site ( Fig.…”