Abstract:

Qilian-Zoulang-Helan Region developed into a large depressed basin in Carboniferous Period.The main sedimentary facies were delta,shore and shoal sea facies.The basin underwent considerable reformation in the late stage of Carboniferous,it shrank in the end of Variscan Period,but its tectonic framework didn't change much;in Indo- Chinese Epoch,the basin was denuded seriously,Permian System was completely denuded due to strong fold,and Carboniferous System was also denuded in different degrees;in Yenshen Period,the basin began to disintegrate,but the Mesozoic distribution areas were favourable for preservation of Carboniferous System.The residual basins were deeply buried in Himalayan Period,and the Carboniferous System was piecemeal distributed in the depressed belts of orogenic zone.In eastern and southern depressions of Bayanhott Basin,the remained Carboniferous System is larger and thicker,and has more types of hydrocarbon source rocks with higher hydrocarbon generation potential,it should be taken as target area for oil exploration.

Key words: favourable block, Carboniferous, post-reformation, Qilian-Zoulang-Helan Depression