Elevated Marine Dissolved Silica Levels Explain a Wide Range of Ediacaran–Cambrian Ediacara-Style Fossil Deposits

Abstract

The processes responsible for the fossilization of the Ediacara Biota—Earth's earliest fossil record of communities of complex, multicellular organisms—have long been debated. On the basis of both geologic and experimental investigations, recent studies have proposed that early diagenetic silica cementation may have been pivotal to the moldic preservation in sandstone (“Ediacara-style preservation”) of fossil assemblages from the eponymous Ediacara Member of South Australia. However, the extent to which early silica cementation can explain other instances of Ediacara-style fossilization in units recording disparate depositional environments, paleogeographies, and geologic ages has not been previously constrained. Herein, we present new paleontological, petrographic, and geochemical data from a range of Ediacara-style fossil assemblages, encompassing a variety of Ediacaran and Cambrian macroorganism morphologies, ecologies, and taxonomic affinities, as well as sedimentary records of organic substrates and the macrofaunal interactions they record. These data indicate that the early diagenetic formation of silica cements was a widespread phenomenon in Ediacaran and Cambrian sandy seafloor environments and likely played a pivotal role in the preservation of these exceptional fossil assemblages. Moreover, the persistence of Ediacara-style fossilization linked to authigenic silica cementation into Cambrian strata provides new evidence that the end-Ediacaran disappearance of the Ediacara Biota was due to evolutionary rather than taphonomic phenomena.