青海曲麻莱一带三叠纪地层岩石粒度分析与沉积环境探讨

青海曲麻莱一带三叠纪地层主要是一套海相类复理石沉积，岩性组合为岩屑砂岩、长石石英砂岩、钙质砂岩、粉砂岩和板岩。通过实测地层剖面取样，采用薄片图像粒度法获取岩石的粒度参数，绘制了粒度频率分布曲线、概率累积频率曲线和C-M图，分析结果表明：岩石粒度正态频率分布曲线较为对称，峰态中等，概率累积频率曲线为较光滑的曲线，内部没有明显的突变点，在C-M图上呈平行C = M基线的矩形，显示出浊流沉积特征。结合地层基本层序和沉积构造特征，认为这套地层总体为半深海—深海浊流沉积环境，自下而上呈现出浅海陆棚—半深海浊积盆地—深海环境演化特点。

Rock Grain Size Analysis and Sedimentary Environment of Triassic Strata in Qumalai Area of Qinghai Province

The Triassic strata in the Qumalai area, Qinghai Province, are mainly a set of fine clastic rock deposits, with lithological association of fine lithic sandstone, feldspathic quartz sandstone, calcareous sandstone, siltstone and slate. The particle size parameters of rocks are obtained through the sampling of measured stratigraphic sections by using the particle size method of thin slices. Scatter plots of structural parameters, probability accumulation curves and C-M charts are drawn. The analysis results show that the normal frequency curves of rock particle size are relatively symmetrical, with moderate peak states. The probability accumulation curve is a smooth curve, without obvious mutation points inside. On the C-M chart, it is a rectangle parallel to the C = M baseline, showing the characteristics of turbidity deposition. Combined with the basic sequence of the strata and the characteristics of sedimentary structures, it is considered that this set of strata is generally a bathyal bathyal turbidity current sedimentary environment, showing the characteristics of deep-sea bathyal turbidite basin shallow sea shelf environment evolution from top to bottom.