江西会昌盆地晚白垩世周田组砂岩粒度分析和沉积环境

Grain Size Analysis and Depositional Environments of Late Cretaceous Zhoutian Formation Sandstones in Huichang Basin of Jiangxi Province

江西赣州会昌盆地是我国东南地区晚中生代众多陆相断陷盆地之一,盆地红层记录了重要的沉积环境信息。采用野外剖面观测、岩石样品偏光显微镜观察和粒度分析等方法,分析会昌盆地晚白垩世周田组的沉积环境。野外观察和镜下薄片鉴定结果表明周田组主要由紫红色、砖红色中粒砂岩至泥岩组成,发育水平层理,砂岩粒径范围为0.02~0.84 mm,碎屑颗粒呈次棱角状-次圆状,分选性较好。偏度多数对称少数呈微正偏态,峰度平坦接近正态分布,概率累积曲线以两跳一悬式为主。因此,周田组主要为水动力较弱的浅湖沉积环境。

The Huichang basin in Ganzhou city of Jiangxi province is one of many continental fault basins formed during Late Mesozoic in southeastern China.The red beds with the basins recorded important information of depositional environments.In order to systematically study the characteristics of the sedimentary environment of late cretaceous Zhoutian formation in the Huichang basin,we measured the outcrop section and analyzed sandstone samples by using a microscope and grain size analysis.The field observation and microscopic thin-section identification results show that the Zhoutian formation is mainly composed of purplish red and brick red medium-grained sandstone to mudstone,with horizontal bedding.The particle size of sandstone ranges from 0.02 mm to 0.84 mm,and the detrital particles are sub-angular to sub-rounded and well sorted.The skewness is mostly symmetrical and a few are slightly positive skewed,the kurtosis is flat and close to the normal distribution,and the probability accumulation curve is dominated by two jumps and one suspension.The Zhoutian formation was mainly deposited in a shallow lake environment with weak water energy.