title: A unifying model for Neoproterozoic-Palaeozoic exceptional fossil preservation through pyritization and carbonaceous compression.
abstract: Soft-tissue fossils capture exquisite biological detail and provide our clearest views onto the rise of animals across the Ediacaran-Cambrian transition. The processes contributing to fossilization of soft tissues, however, have long been a subject of debate. The Ediacaran Gaojiashan biota displays soft-tissue preservational styles ranging from pervasive pyritization to carbonaceous compression, and thus provides an excellent opportunity to dissect the relationships between these taphonomic pathways. Here geochemical analyses of the Gaojiashan fossil Conotubus hemiannulatus show that pyrite precipitation was fuelled by the degradation of labile tissues through bacterial sulfate reduction (BSR). Pyritization initiated with nucleation on recalcitrant tube walls, proceeded centripetally, decelerated with exhaustion of labile tissues and possibly continued beneath the BSR zone. We propose that pyritization and kerogenization are regulated principally by placement and duration of the decaying organism in different microbial zones of the sediment column, which hinge on post-burial sedimentation rate and/or microbial zone thickness.
authors.affiliation: Department of Geological Sciences, University of Missouri, Columbia, Missouri 65211, USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Schiffbauer
authors.affiliation: Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061, USA.
authors.forename: Shuhai
authors.initials: S
authors.lastname: Xiao
authors.affiliation: Early Life Institute, State Key Laboratory of Continental Dynamics, and Department of Geology, Northwest University, Xi'an 710069, China.
authors.forename: Yaoping
authors.initials: Y
authors.lastname: Cai
authors.affiliation: Department of Geological Sciences, University of Delaware, Newark, Delaware 19716, USA.
authors.forename: Adam F
authors.initials: AF
authors.lastname: Wallace
authors.affiliation: Early Life Institute, State Key Laboratory of Continental Dynamics, and Department of Geology, Northwest University, Xi'an 710069, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Hua
authors.affiliation: Nanoscale Characterization and Fabrication Laboratory, Institute of Critical Technology and Applied Science, Virginia Tech, Blacksburg, Virginia 24061, USA.
authors.forename: Jerry
authors.initials: J
authors.lastname: Hunter
authors.affiliation: NASA Astrobiology Institute, Department of Geoscience, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Huifang
authors.initials: H
authors.lastname: Xu
authors.affiliation: Department of Geological Sciences, Indiana University, Bloomington, Indiana 47405, USA.
authors.forename: Yongbo
authors.initials: Y
authors.lastname: Peng
authors.affiliation: Department of Geology and Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20742, USA.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Kaufman
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002254:Carbonates / Q000737:chemistry*; D002681:China; D005580:Fossils; D019015:Geologic Sediments / Q000032:analysis; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction; D011309:Preservation, Biological; D011312:Pressure; D013440:Sulfides / Q000737:chemistry*; D016999:Sulfur-Reducing Bacteria / Q000502:physiology
chemical_list: D002254:Carbonates; D013440:Sulfides; C011342:pyrite; D007501:Iron