BASAL CAMBRIAN ACRITARCHS BIOSTRATIGRAPHY OF THE YANGTZE PLATFORM, SOUTH CHINA

Acanthomorphic acritarchs are widely distributed in the lowermost Cambrian Strata of the Yangtze Platform, and have been suggested as a prospective biostratigraphic correlation tool between South China, Tarim Basin, and Southeastern Poland. However, variations in stratigraphic settings and taphonomic controls of each sedimentary basin make it difficult to understand the spatial and temporal distribution of acritarchs, as well as their temporal relationships with other major fossil groups (e.g., small shelly fossils) and carbon isotope chemostratigrpahy. A number of acritarchs and other microfossils indicative of the basal Cambrian age were recovered from the early diagenetic black chert of the pre-trilobites successions of the Yangtze Platform. Studied areas include the lower part of the Yanjiahe Formation, Yangtze Gorges area and the Daibu Member of the Zhujiaqing Formation, Yunnan Province. An acritarch assemblage of Asteridium-Heliosphaeridium-Comasphaeridium (AHC), which is synchronous to the lowermost small shelly fossil assemblages in South China (Anabarites trisulcatus-Protohertzina anabarica Zone), is spatially confirmed in the studied sections. Also, the temporal relationship between acritarchs and chemostratigraphic record of each section was reviewed. The new data indicates that the AHC assemblage is a useful biostratigraphic correlation tool in the lowermost Cambrian strata in the Yangtze Platform, and between South China and other areas.