Abstract A total of 92 representative sandstone samples of the Bredasdorp Basin in boreholes E-AH1, E-AJ1, E-BA1, E-BB1 and E-D3 have been investigated for their grain size characteristics. Grain size textural parameters and their cross plots, linear discriminate functions (LDFs), C–M (C = first percentile and M = median) diagram and log–probability plots were calculated and interpreted to understand the mode of transportation and hydrodynamic conditions and also to unravel the depositional environments of the sediments. The grain size textural parameters revealed that the Bredasdorp sandstones are unimodal, predominantly fine-grained, moderately well-sorted, mesokurtic and near symmetrical. The bivariate plots of grain size textural parameters indicate that the depositional environments had been influenced mainly by river/beach/coastal dune conditions. The LDF plots show that the sediments are turbidity current deposits in a shallow marine environment. The C–M diagram revealed that the studied sandstones were mainly deposited by traction currents and beach process. In addition, the grain size log–probability curves and C–M diagram show the predominance of suspension and saltation modes of sediment transportation. Based on the inter-relationship of the various statistical parameters, it is deduced that the Bredasdorp Basin are mainly shallow marine deposits with signature of beach and coastal river processes.

中文翻译：

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南非南海岸 Bredasdorp 盆地白垩纪砂岩的构造特征、运输方式和沉积环境：来自粒度分析的证据

摘要 对布雷达斯多普盆地E-AH1、E-AJ1、E-BA1、E-BB1和E-D3钻孔共92个代表性砂岩样品的粒度特征进行了研究。计算并解释了粒度纹理参数及其交会图、线性判别函数 (LDF)、C-M（C = 第一百分位数和 M = 中位数）图和对数概率图，以了解运输模式和水动力条件以及揭示沉积物的沉积环境。粒度结构参数表明 Bredasdorp 砂岩是单峰的，主要是细粒，中等分选，中峰岩，近乎对称。粒度结构参数的双变量图表明沉积环境主要受河流/海滩/沿海沙丘条件的影响。LDF 图显示沉积物是浅海环境中的浊流沉积物。C-M图显示，研究的砂岩主要由牵引流和海滩过程沉积。此外，粒度对数-概率曲线和C-M图显示了沉积物运输的悬浮和跃移模式的优势。根据各统计参数之间的相互关系，推导出Bredasdorp盆地主要是浅海沉积，具有海滩和沿海河流过程的特征。C-M图显示，研究的砂岩主要由牵引流和海滩过程沉积。此外，粒度对数-概率曲线和C-M图显示了沉积物运输的悬浮和跃移模式的优势。根据各统计参数之间的相互关系，推导出Bredasdorp盆地主要是浅海沉积，具有海滩和沿海河流过程的特征。C-M图显示，研究的砂岩主要由牵引流和海滩过程沉积。此外，粒度对数-概率曲线和C-M图显示了沉积物运输的悬浮和跃移模式的优势。根据各统计参数之间的相互关系，推导出Bredasdorp盆地主要是浅海沉积，具有海滩和沿海河流过程的特征。