Bei′an Formation—A new lithostratigraphic unit of Carboniferous in the Liuzhou area, Guangxi, China

Around the Liuzhou area of Guangxi, China, the so-called “Huangjin Formation” refers to the strata between Carboniferous Luzhai Formation and "Simen Formation", while they are remarkably different to the typical Huangjin Formation in the type area in terms of lithology, lithofacies and paleo-geographic position. Based on our study as well as published literature, Bei′an Formation, a new lithologic unit is established to denote the sediments that were assigned to the “Huangjin” Formation. This Bei′an Formation is widely exposed in the areas of Liuzhou, Liujiang, Luzhai, Liucheng, Huanjiang in northern and central Guangxi. The Bei′an Formation represents a succession of basin and slope sediments, and mainly comprises gray or dark gray, thin to thick-bedded packed biomicrites and fossiliferous biomicrites, with intercalations of siliceous rocks, mudstones and sandstones, it can be subdivide into three sedimentary cycles. Underlying strata are Luzhai Formation and they underly below Xinyu Formation with conformity contact. Besides, their age is late Visean to Serpukhovian.