Dating and tectonostratigraphy of the Early Jurassic rift delta at the northwestern margin of the Indian Plate, Pakistan

Abstract

The study aims to establish the palynostratigraphy, tectonostratigraphy, and palaeoclimate of early Jurassic deltaic strata of the Datta Formation deposited on the northwestern margin of the Indian Plate, Eastern Tethys. Two palynomorph Oppel Biozones namely Quadraeculinaanellae formis-Chasmatosporites cf. elegans and Callialasporites turbatus were erected which suggest an Hettangian-Bajocian age for the Datta Formation. The palynofacies integrated with established lithofacies data indicate the dominance of delta plain settings in the western Salt Range and Trans-Indus Ranges. Such clastic dominated facies truncated along palaeohighs and marine settings in its surroundings, offer good chances of stratigraphic traps within the unit.The literature review suggests that the deposition of deltaic sediments occurred in rift settings, which dominated Gondwana during the Early Jurassic. Such synchronous rift settings with associated continental and deltaic sediments are recorded in almost all continents of Gondwana affinity, thus the Datta Formation is part of a regional delta system. The dominance of Araucariaceae in association with Cycadaceae, as well as the evergreen trees of Cyatheaceae and Matoniaceae within the Datta Formation, indicates warm humid conditions during the deposition of the studied unit.