Petrography and heavy mineral assemblage of the Oligocene Barail sandstones exposed in and around Khonoma village, Kohima district Nagaland, India

Abstract

Barail sandstones exposed in and around Khonoma village, south- west of Kohima town, Nagaland, India have been studied for provenance interpretation using petrography and heavy minerals. Moderate to wellsorted Barail sandstones is mainly composed of both undulatory and non-undulatory monocrystalline quartz. However, polycrystalline quartz was also observed. Most common feldspar in these sediments is the plagioclase feldspar. Rock fragments are represented by chert, siltstones and schist. Constituent wise they are second in abundance. Euhedral, subrounded and rounded zircon, tourmaline, rutile, staurolite, sillimanite, and kyanite constitute the heavy mineral assemblage of the studied Barail sandstones. Rounded iron oxides represent opaques. Petrography studies and heavy minerals point towards a mixed provenance dominated by a sedimentary source. Petrography and heavy mineral studies also suggests that owing to changing plate interaction contributions might have come from the Karbi-Anglong massif and Naga metamorphics. In addition to that sediments formed under earlier tectonic regimes might have also supplied the sediments.