广东南雄盆地白垩-第三系界线地层岩性特征及环境分析

<正> 1983年底至1984年初,科学院陆相白垩-第三系界线研究队在广东南雄盆地杨梅坑—逆龙坑及风门坳两条剖面上进行了野外观察、剖面测试及化石(介形类、轮藻、腹足类及叶肢介)、岩石标本的系统采集工作。笔者对其岩性、地球化学特征及沉积环境等方面进行了初步分析,并认为白垩-第三纪地层间可能存在沉积间断。兹论述如下:

The petrographic characters and environmental analysis of the Cretaceous-Tertia-ry Boundary strata at the Nanxiong Basin Guangdong

The purpose of this paper is to investigate compositional and Mxtural characteristics, and elemental geochemistry o?the red beds in the Yangmeikeng-Nilongkeng and Fengmenao sections in the Nanxiong Basin by analyses of petrographic microscopes, grain size parameters, X-ray, infrared-spectrum, spectrometry, and electronic microscope. Based on petrographic characters and analytical data, we divided the Cretaceous-Tertiary boundary strata into three parts: The Shanghu Formation, the middle and upper members of the Nanxiong Formation and have come to the following conclusions: 1. During the latest Cretaceous and earlist Tertiary, a suite of red piedmont plain-lake facies clastic sediments was deposited there, the climate was arid and hot during that time, indicating a water medium condition salinization of rich magnesium. 2. The mineralogical characters and geochemical data show that a clear change tooks place between the middle and upper of the Nanxiong Formation, and between the Nanxiong Formation and the Shanghu Formation, which might have bearing on the depositional interval between them.