Foreland basin unconformity, Western Himalaya, Pakistan: timing gap, regional correlation and tectonic implications

Abstract

This study estimates the timing of unconformity between marine–continental transitional sequence of the Kuldana Formation and continental sequence of the Murree Formation for the first time across the Hazara-Kashmir syntaxis, western Himalaya, Pakistan. The ages of the studied units are constrained using detrital zircon U–Pb geochronology. The maximum depositional ages constrained by weighted mean and youngest detrital zircon age are 37 ± 1.7 Ma and 22.5 ± 0.6 Ma for top of Kuldana and base of Murree formations, respectively. Based on this age, the duration of hiatus is estimated to be ~ 14.5 Ma. The comparison of this unconformity and sedimentation pattern along strike suggests that the initial collision occurred in the central segment causing its early uplift and erosion with development of the unconformity. The sedimentation in the central segment culminated at ~ 37 Ma and resumed at ~ 22.5 Ma. The wider gap in central segment becomes narrower at western and eastern margin suggesting discontinuous deposition due to gradually closure of western and eastern margin. This supports the diachronous collision of the Indian and Asian plates with initial contact at the central segment.