Geobiology of a palaeoecosystem with Ediacara-type fossils: The Shibantan Member (Dengying Formation, South China)

摘要: Abstract Despite the importance of palaeoecosystems with Ediacara-type fossils for early evolution metazoans, only little is known about interplay geological and biological processes in these environments. The reason that sedimentary structures, biogenic structures (bio-) geochemical signatures (e.g. hydrocarbon biomarkers) are commonly not well preserved due to predominance volcanic siliciclastic lithologies. Shibantan Member (Dengying Formation, South China) one few carbonate settings organisms worldwide its lithology promises an excellent preservation facies signatures. Here we provide first comprehensive geobiological characterisation order reconstruct between assess microbial activities palaeoecosystem fossils. Facies analyses revealed organic matter were autochthonously formed by linked mats. However, material was frequently reworked re-deposited within same setting (i.e. para-autochthonous) as evidenced small-scale (hummocky-) cross stratification, erosional contacts, lenticular bedding load casts. Negative Ce anomalies (Ce/Ce*) low V/Cr ratios demonstrate molecular O 2 present water column, whereas characteristic Ni/Co-, V/(V + Ni), V/Sc suggest contemporaneous presence sub- anoxic water. Taken together, observations imply a temporarily stratified body mixed ventilated storms. 13 C-enrichments carbonates (δ C = +3.29 +3.98‰, VPDB) together C-depletions syngenetic n -alkanes cleaved from extraction residue using catalytic hydropyrolysis (HyPy; δ C = −31.7 −36.3‰, could indicate significant withdrawal 12 C primary producers thrived At time, sulphurised biomarkers bitumen HyPy-pyrolysate hint at decomposition concomitant sulphide production sulphate reducing bacteria. When oxygen available sediment–water interface mixing storms, oxidising bacteria possibly favoured. results demonstrated palaeoenvironmental conditions dynamically changed through complex abiogenic processes.