Abstract

Clay-rich and siliceous sedimentary rocks of earliest Cambrian age on the Yangtze Platform, China, contain abundant siliceous microfossils. The black cherts and black shales in this sequence, of earliest Cambrian age, contain sponge spicules (both macroscleres and microscleres), derived from lithistid demosponges and hexactinellids. These spicule associations are useful for biostratigraphic correlation, and indicate that Porifera played an important role in the geochemical cycling of silica at the beginning of the Phanerozoic. Phosphatic microfossils also contributed to the deep-sea ecology of this region during the earliest Cambrian.