Early Triassic Chaohusaurus Fauna's Paleoenvironment

Microfacies characteristics of the Lower Triassic containing Chaohusaurus fauna in Chaohu area, Anhui Province and its palaeoenvironment.

Authors:

Zhang et al

Abstract:

The Early Triassic Chaohusaurus fauna was found at No.598-630 layers at the top of the Middle Member-the bottom of the Upper Member of the Nanlinghu Formation in Majiashan section of Chaohu area,Anhui Province. Based on the microfacies characteristics and the carbon and oxygen isotope analysis,the sedimentary environment of the fossil beds where the Chaohusaurus fauna had occurred was studied. 4microfacies types were recognized from the studied layers,which contained the red-grey thick nodular limestone with spicules-bivalves,the gray bioclastic-argillaceous micrite limestone,the gray laminated argillaceous micrite limestone,and the light gray micrite limestone, respectively. It was indicated that the sedimentary environment of the fossil beds was from the foot of the outer ramp-abyssal basin to the outer ramp. The values of the δ13C and δ18O are generally low in the whole of fossil beds. Combined with the above characteristics,it might be inferred that the Chaohusaurus fauna was living in the outer ramp zone with low-energy,less numbers and types of the biocoenose,and high seawater temperature.