ACRITARCH BIOSTRATIGRAPHY OF THE EDIACARAN DOUSHANTUO FORMATION IN AN UPPER SLOPE FACIES

The Doushantuo Formation of South China is one of the few stratigraphic units in the world where it is possible to sample a rich early to middle Ediacaran fossil record from rocks that also record proxies for global ocean chemistry. Integrated studies of geochemical proxies and the microfossil record have led to the development a biostratigraphic and chemostratigraphic framework for correlating between sections of the Doushantuo Formation. However studies of acritarch biostratigraphy and chemostratigraphy in the Doushantuo Formation have mostly focused on shelf-lagoon facies in the Yangtze Gorges area, and these facies may have been partly decoupled from the global ocean. Sediments from upper slope environments have received less attention from chemostratigraphers but have been interpreted to be geochemically more representative of the global ocean. Acanthomorphic acritarchs, morphologically complex microfossils which form the basis of biostratigraphic correlation within the Doushantuo Formation, have not been studied from slope sections. It is therefore not clear whether the correlative framework developed in shelf-lagoon facies can be extended to slope sections. We present data on acanthomorphic acritarchs from early diagenetic cherts from an upper slope section at Siduping, northwestern Hunan Province. Several acritarch species have been identified including the biostratigraphically useful species Hocosphaeridium anozos. These results demonstrate the presence of an Ediacaran acritarch record in the Doushantuo Formation outside of the Yangtze Gorges area, emphasize the potential of integrated bio- and chemostratigraphy in the correlation of Ediacaran strata in South China, and highlight the importance of the Doushantuo Formation for understanding the relationship between Ediacaran biological and environmental evolution.