This interval (Moty Group) comprises a transgressive succession with red-coloured alluvial to deltaic siliciclastic deposits (Shaman Formation) and overlying shallow-marine carbonates (Irkut Formation). We analyse the taxonomy and stratigraphic distribution of small skeletal fossils and trace fossils, the carbonate carbon and oxygen isotope composition, and U-Pb detrital zircon age in the Ediacaran-Cambrian transitional interval of the Irkutsk Cis-Sayans Uplift (southwestern Siberian Platform). However, the strong linkage of biostratigraphic and chemostratigraphic methods with lithofacies makes the localization of the Precambrian-Cambrian boundary and its correlation with lithologically contrasting sections highly debatable. The exceptional record of mat surfaces preserved in the Flinders Ranges area demonstrates that, in addition to the apparent ecological role played by mat surfaces in Ediacaran communities, they were also likely a significant component of the Ediacara Member biomass and were integral to community function.Ī number of ecological and geochemical transformations occurred during late Ediacaran and early Cambrian time, the effects of which are difficult to overestimate. However, we do observe that large Dickinsonia are more likely to occur on surfaces recording mature matgrounds. We additionally find that the sessile taxa Obamus and Coronacollina are restricted to surfaces with mature mats whereas all other Ediacaran macrobiota show no connection to mat occurrence and maturity. Using a ranked Mat Maturity Index, we find that although density of macroscopic body fossils and genus diversity correlate with mat maturity, evenness does not. We find that mat maturity, rather than the mat type itself, more strongly influenced the distribution of taxa and the development of Ediacara macroorganism communities. Based on the assumption that mat maturity represents an indicator of the duration of time between burial events, we can test predictions about the relationship between mat maturity and community development. Excavation of 33 fossiliferous beds with varying types and extents of organosedimentary surface textures provide the opportunity to utilize this record to develop criteria to evaluate the maturity or extent of growth of Ediacaran matgrounds and, using these characteristics, to examine the relationship between mat type, mat maturity and Ediacara Biota community structure. This succession unambiguously demonstrates that heterogenous mats coexisted with and were central to the ecology and biology of the Ediacara Biota. The greatest diversity and complexity of organic mat textures occur in the Ediacaran fossil record as exemplified by the Ediacara Member of the Rawnsley Quartzite, which crops out in and around the Flinders Ranges, South Australia. In the absence of complex, bioturbating organisms, the seafloor during the Precambrian was covered in widespread organic matgrounds. Here our aim is to use this record to develop criteria to evaluate the maturity or extent of growth of Ediacaran matgrounds and, using these characteristics, to examine the relationship between mat type and maturity and Ediacara Biota community structure. Many of the bedding-plane features that are central to defining MISS and TOS (e.g., preservational variability, bed-scale diversity, associated macrobiota, grain size, mineralogy, chemical composition, and sedimentary structures) have previously been described (e.g., Bottjer et al., 2007 Bouougri and Porada, 2007 Carbone and Narbonne, 2014 Corenbilt et al., 2019 Elliott et al., 2011 Hill et al., 2016 Kumar and Ahmad, 2014 Laflamme et al., 2012 Liu et al., 2013 Nettle et al., 2014 Nofke, 2015 Noffke et al., 2002 Noffke, 2009 Sarkar et al., 2008, Sarkar et al., 2016Tarhan et al., 2017 Vago et al., 2017). At the Nilpena Ediacara National Park (NENP), excavation of 40 bedding planes, 33 of which preserve >10 individual macroscopic body fossils, reveals an unprecedented abundance and diversity of in situ macroorganism communities and associated microbial mats.
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