Lithofacies characteristics and depositional environment interpretations of the Middle Jurassic Fort Member rocks, Jaisalmer Formation, Western Rajasthan, India

Abstract

The present study is focused on the identification of lithofacies characteristics and depositional environments for the Middle Jurassic sediments of Fort Member, Jaisalmer Formation, Western Rajasthan (NW India). Three facies associations are documented as tidally influenced fluvial, tidal/inter-tidal flat and wave-dominated shoreface facies deposits. Facies association-1 contains matrix-supported clasts, planar and flaser cross-stratified sandstone, interbedded sandstone and horizontal laminated sandstones; indicative of tidally influenced fluvial deposits. Facies association-2 characterized by herringbone cross-stratified sandstones, horizontal laminated sandstones, planar and trough cross-stratified sandstones, the alternate band of sandstone and shale, mud-crack sandstone developed on a tidal/inter tidally influence deposits. Facies association-3 consists of wave-dominated shoreface facies association consisting of wavy and lenticular beds, interference ripples, horizontal laminated sandstone, small scale planar cross-stratified sandstone, trough, and hummocky cross-stratified sandstone as well as fossiliferous limestone. Palaeoflow patterns from unipolar to bipolar indicate a change from tidal influence fluvial to marine depositional environments. The overall lateral and vertical distribution of lithofacies shows that the depositional environment was tidal-dominated fluvial channel to the marine realm.