广西柳州地区石炭系一个新的岩石地层单位——北岸组

在1∶5万地质测量中，广西柳州地区石炭系鹿寨组与“寺门组”之间的地层曾被称为“黄金组”，但其与典型地区的黄金组在岩性、岩相、古地理位置等方面均存在显著差异。根据新的研究与前人的资料综合分析，将柳州地区所谓的“黄金组”命名为一个新的组——北岸组。该组主要分布于广西中北部柳州市、柳江县、鹿寨县、柳城县、环江县等地，在古地理上位于黔南-桂中台槽的北缘。该组岩性以灰—深灰色薄—厚层生物碎屑粉晶灰岩、含生物碎屑泥晶灰岩为主，夹硅质岩、泥岩和砂岩，可划分为3个沉积旋回，属斜坡-盆地相沉积。下伏鹿寨组，上覆新圩组，均为整合接触。时代为石炭纪维宪期晚期—谢尔普霍夫期。

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 sedi-mentary cycles. Underlying strata are Luzhai Formation and they underly below Xinyu Formation with conformity contact. Besides, their age is late Visean to Serpukhovian.