Research / 2019 / Article / Fig 6

Research Article

Clay Mineral and Geochemical Proxies for Intense Climate Change in the Permian Gondwana Rock Record from Eastern India

Figure 6

Photomicrographs of sandstones from the Talchir and Barakar Formations. (a) Typical immature Talchir sandstone. Note the common presence of both plagioclase (PI) and K-feldspar (K-f) grains, cross-polarized light. (b) Clayey epimatrix-rich Barakar sandstone with fresh to partly altered feldspar, cross-polarized light. (c) Barakar sandstone showing various stages of K-f alterations, cross-polarized light. (d) Grain-replacive kaolinite cement in the Barakar sandstone, cross-polarized light. (e) Early diagenetic quartz cement in the Talchir sandstone. Note the common occurrence of fusion and interpenetration of overgrowths, cross-polarized light. SEM images for the fabric and morphology of the clay minerals in the mudstones. (f) Illite and mixed layer illite/smectite exhibiting typical bent sheet or detrital plate-like shapes. Note the poor crystallinity of the clays. (g) Warping of the clay particles along the outlines of the adjacent coarser detrital grain.