Division and Correlation of the Upper-Middle Cambrian Evaporate Platform Facies Dolomite Formation in Tarim Basin

Abstract

The Cambrian strata in Tarim basin is mainly evaporate platform facies dolomite. Due to the lack of trilobite fossils, it is hardly to achieve isochronous stratigraphic division and correlation. The Xiaoerbulake outcrop and Fang 1 well are typical surface and subsurface Cambrian sections in Tarim Basin respectively. Shayilike, Awatage and Xiaqiulitage Groups were regarded as the complete Upper -Middle Cambrian previously which composed of dolomite. The carbon isotope values range from –15.5 to 2‰, and three negative excursions are found (N1, N2 and N3). Comparing with the Global Standard Chronostratigraphic Scale for the Middle and Upper Cambrian System, the fifth stage and the Drumian of the third Series, the ninth and the tenth Stage of Furongian Series can be recognized, while the Guzhangian and Paibian are lost. As a result, the Cambrian Formation in Tarim Basin can be divided accurate to stage scale.