Depositional System of Early Cretaceous Heishidu Formation in the North Margin of the Dabie Mountains
LI Shuang ying 1 LI Ren wei 2 WANG Dao xuan 1 LIU Yin 1 YUE Shu cang 1 MENG Qing ren 2 JIN Fu quan 1 1(College of Resource and Environment Engineering, Hefei University of Technology, Hefei 230009) 2(Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029)
The Early Cretaceous Heishidu Formation (HsdF), distributed between the southern Xiaotian Mozitang fault (XMF) and northern Jinzhai Xianghongdian Xitanchi fault in the north margin of the Dabie Mountains, elongates in east westward, and thickness is more than 1 km. The lithofacies are mainly composed of Bcm, Gcg, Gcm, Gm, Sg, Ss, Fc, Fm, Fr, C and so on, and depositional systems include alluvial fan, fluvial, fan delta and lacustrine deposits, and fluvial deposits are mainly composed of sediments of floodplain and crevasse splays. HsdF developed the fining upward sequences, and alluvial fan in the early stage, floodplain and crevasse splay and fan delta in the middle stage, and lacustrine turbidites in the late stage. Alluvial fan and lacustrine turbidites mainly developed in Xiaotian area on the eastern part of the basin, floodplain and crevasse splay in Huoshan area on the western, and fan delta on both parts. The basin might be attributed to an asymmetric down faulted lake, and its evolution might be controlled by XMF.