A geological study on Upper Bhuban Formation in parts of Surma Basin, Aizawl, Mizoram

Abstract

Tertiary sediments are thickly deposited in most part of the northeast India attaining a maximum thickness of ±7 km sedimentary succession. Surma basin located in the eastern proximity of India is also characterized by a thick sedimentary column which can be considered as the northeastern extension of Greater Bengal basin. This basin was initiated due to the mutual collision between Indian and Burmese Plate. Due to this collision, the bed rocks have undergone folding which are oriented N-S trending hill ranges. The basin was also cut by a number of parallel to sub-parallel transverse faults and thrusts. The litho association is consisting of sandstone, siltstone, shale and their various proportions. The present study focused on the provenance of the sediments, tectonic settings of the basin and various paleoclimatic conditions prevailing during the time of deposition by using petrography, granulometric and heavy mineral analysis of representative rock samples which were collected from various parts of Aizawl district of Mizoram belonging to the Upper Bhuban Formation. Based on the various proxies it was confirmed that the sediments were primarily derived from surrounding orogens and deposited in a shallow marine basin under the influence of fluvial-deltaic conditions which were basically sourced from felsic provenance. The sediments were moderately weathered under semi-humid to humid climatic condition before they deposited into Surma basin. Sandstones samples are litharenite and wacke type which were deposited in an active continental margin to recycled orogen settings.