Petrological study of the Kaimur Group sediments, Vindhyan Supergroup, Central India: implications for provenance and tectonics

Abstract

The Mesoproterozoic Kaimur Group (1.1 Ga) belongs to the upper part of the Vindhyan Supergroup, which overlies the carbonate-rich sequence of the Semri Group (Lower Vindhyan), conformably in the Son Valley, Central India. The Kaimur Group consists predominantly of sandstones. On the basis of the present study they are classified as subarkose, sublitharenite, and quartz arenite in the Quartz (Q)-Feldspar (F)-Rock fragment (R) triangular diagram. The XRD patterns indicate that illite is the most prominent clay mineral. The Kaimur sequence can be divided into the Lower and Upper Kaimur Groups. The modal analyses data and the mineralogical ratios [Quartz/Feldspar (Q/F), Quartz/Lithic fragments (Q/L), Monocrystalline Quartz/Polycrystalline Quartz (Qm/Qp), Quartz/(Feldspar + Rock fragment) (Q/(F + R))] suggest that the Lower Kaimur Group has a fining upward sequence characterized by a decrease in textural and compositional maturity. In contrast, the Upper Kaimur terrigenous rocks have a coarsening upwards sequence with an increase in compositional and textural maturity. Monocrystalline Quartz-Feldspars and granite fragments-Lithics plus quartzose varieties (Qm-F-Lt) and total Quartz-Feldspar-Lithics (Qt-F-L) ternary plots, Polycrystalline Quartz-Non-undulose Quartz-Polycrystalline Quartz-Undulose Quartz ((Qp)-Q(nu)-(Qp)-Q(u)) diamond diagram and the types of lithic fragments suggest that the Lower Kaimur was derived mainly from a craton interior plutonic provenance (uplifted Bundelkhand craton that lies to the north of the basin). The Upper Kaimur terrigenous rocks are dominantly product of a recycled orogen composed of medium-to high-grade metamorphic rocks from the south (Mahakoshal metasediments and Chhotanagpur Gneissic Complex (CGC) of the Central Indian Tectonic Zone (CITZ)). The Polycrystalline Quartz/(Feldspar + Lithics) (Qp/(F + L)) vs. Quartz total/(Feldspar + Lithics) (Qt/(F + L)) ratios represent the deposition of Kaimur sandstones in the warm humid climate.