Facies characteristics and cyclicity of Lower Siwalik sediments, Jammu area: a new perspective

Abstract

The Lower Siwalik succession of the Jammu area has been distinguished into three major lithofacies associations: a sand-dominant association, a sandy-mud-dominant association, and a silty-heterolithic association. The sand-dominant association is made up of three lithofacies: cross-bedded sandstone, rippled silty sandstone and bioturbated sandy siltstone, which are organized in multi-storeyed sandbodies representing deposition in major river channels. The sandy-mud-dominant association is made up of two lithofacies, mottled clayey siltstone and interbedded sandstone, siltstone and mudstone, representing deposition in overbank areas of flood-plain and natural levee-crevasse splays. The sand-dominant association and sandy-mud-dominant association are grouped together as a channel-related succession and are products of processes in the river channel. The silty-heterolithic association consists of four lithofacies: mottled siltstone, mottled silty sandstone, bedded calcrete and mottled mudstone. They are considered to be deposits of Doab (upland interfluve) areas operating independently of present-day major river channels. These deposits have been formed in minor channels, sloping surfaces, and lakes and ponds of the interfluve regions. The cyclicity of both successions (channel-related and Doab-related) has been determined using a partial-independence statistical model.