Precambrian microfossils from the Sinian of South China

Abstract

The discovery of previously unknown microfossils from the Sinian of western Hubei Province, South China (Fig. 1) is reported here. The Sinian there, up to 1,000 m thick, is naturally divisible into four formations (Fig. 2) from the base upwards: (1) the Liantuo Formation comprising feldspar–quartz–sandstones with basal conglomerates; (2) the Nantuo Formation, which is a tillite; (3) the Doushantuo Formation, which has micro-dolomites intercalated with black shales and cherty beds with some siliceous or phosphatic nodules; and (4) the Dengying Formation, which is mainly dolomites. The rock sample in which the microfossils were found was collected from the lower part of the Doushantuo Formation near the highway side ∼500 m east of Liantuo, Yichang County (Fig. 1). The Doushantuo Formation has been dated as 693±66 Myr (Rb–Sr isochron age)1. Pseudomorphs after gypsum sometimes occur in the lower part. The microfossils are preserved in siliceous nodules, particularly in the cherty portions. The dark colour of the nodules is due to the high organic content.