Biochronological continuity of the Paleogene sediments of the Himalayan Foreland Basin: paleontological and other evidences

Abstract

The paleontological and field evidences presented in the paper demonstrate a biochronological continuity from the marine Subathu (Late Thanetian to Middle Lutetian) through the Passage Beds (Late Lutetian to Middle Bartonian) to the Dagshai and equivalent formations (Late Bartonian to Rupelian) of the Himalayan Foreland Basin, east of Hazara–Kashmir syntaxis. A similar continuity has also been demonstrated in the Sulaiman Range based on an assignment of Oligocene age to the Bugti vertebrate fauna, hitherto considered to be of Early Miocene age. Thus, the concept of a >10 Ma hiatus in the foreland basin based on 40Ar/ 39Ar dates of single detrital muscovite grains from the supposed basal Dagshai arenite is no longer tenable. While the occurrence of Cr-spinel and K–T boundary nannoplanktons in the Subathu Formation and Passage Beds indicate a westerly–northwesterly provenance, that of the radiolarian chert in the Dagshai and coeval formations indicates a northerly provenance from the Indus Suture Zone, coinciding with the first influx of the Himalayan detritus around 40 Ma.