Abstract—This article presents the results of the petrographic and mineralogical study of the sandstones of the Algan Formation. Sandstones are represented by ultrafine-, fine-, and medium-grained quartz–feldspar greywackes according to the classification of (Shutov et al., 1972). Two tectonically juxtaposed sandstone lithotypes were distinguished. These lithotypes were deposited in two basins of different ages from high- and medium-velocity turbidity currents off the coast in moderately deep marine environments. Sedimentation conditions are typical of areas near river deltas and prodeltas. The provenance areas of these basins were different, being associated with volcanic areas of different-ages in the north of the studied region.

摘要—本文介绍了Algan组砂岩的岩石学和矿物学研究结果。根据（Shutov et al。，1972）的分类，砂岩以超细，细和中等粒度的石英-长石灰泥为代表。区分了两种构造并置的砂岩岩性。这些岩型是在中等深度的海洋环境中，从沿海高中速混浊流沉积在两个不同年龄的盆地中的。沉积条件是三角洲和三角洲附近地区的典型特征。这些盆地的物源区不同，与研究区域北部不同年龄的火山区有​​关。