Environmental Controls on the Taphonomy of Phosphatized Animals and Animal Embryos from the Neoproterozoic Doushantuo Formation, Southwest China

Phosphatized animals and animal embryos of the Neoproterozoic Doushantuo Formation of Southwest China provide what is likely the earliest fossil evidence for animals, including bilaterians. This research utilizes field and petrographic analyses of the animal-fossil-bearing interval of the Doushantuo Formation and general observations of animal and animal-embryo preservation in order to gain insight into the taphonomic processes involved in the preservation of these fossils. Results indicate that there are two genetically related phosphatic lithofacies within the animal- and animal-embryo-bearing Weng'an Phosphorite Member: a lower black facies and an upper gray facies. Within each of these facies, phosphogenesis and phosphatization took place under different environmental conditions. The black facies is a pyrite-rich bituminous phosphorite that lacks dolomite in its lowermost two meters and contains evidence for lower levels of reworking than the gray facies. Deposited on top of a karstic sequenc...