Constraints

Abstract- Detailed petrographic analysis of Talchir sandstones of Lotma nala section has been used to ascertain tectonic setting, source area lithology and climatic conditions prevailing at the time of deposition. Quartz, feldspar and rock fragments are the dominant framework components of the studied specimens. These sandstones are mineralogically and texturally immature and have been classified as arkose and lithic arkose on the basis of QFR diagram. Quartz in these sandstone samples is of monocystalline and polycrystalline nature and feldspars are represented mainly by orthoclase and plagioclase. A wide variety of lithic fragments like granite, schist, shale, siltstone, quartzite, phyllite and gneiss have been recorded in these sandstones. QtFL and QmFLt plots indicate derivation mainly from transitional continental region of continental block provenance. The Precambrian granitic / gneissic basement has been established as a source for these sediments. The bivariant log-log Qt/F+R and Qp/F+R plot of the studied sandstone specimens indicate that semi humid climatic conditions prevailed at the time of deposition of these sandstones. The petrographic data thus suggests that the transitional continental region comprising of acid igneous, sedimentary, metasedimentary and metamorphic rocks may have been the source of these sandstones