大别山北缘早白垩世黑石渡组沉积体系研究

分布于大别山北缘晓天-磨子潭断裂以北和金寨-响洪甸-西汤池断裂以南呈东西向延伸的早白垩世黑石渡组,厚达千米,岩相主要有角砾岩、砾岩、砂岩、粉砂岩、泥岩等,包括冲积扇、河流、扇三角洲和湖泊沉积体系,其中河流沉积主要由洪泛平原和决口扇组成。黑石渡组属于向上变细层序,早期为冲积扇沉积,中期为洪泛平原、决口扇和扇三角洲沉积,晚期为深湖浊流沉积。冲积扇和湖相浊流沉积主要发育于盆地东段舒城晓天地区,洪泛平原和决口扇沉积主要发育于盆地西段霍山地区,扇三角洲在两地都比较发育。这是一个不对称的断陷盆地,晓天-磨子潭断裂可能对盆地的发育具有控制作用。

Depositional System of Early Cretaceous Heishidu Formation in the North Margin of the Dabie Mountains

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.