Paleogene carbonate ramp development in the Kohat Basin of northwestern Pakistan

Abstract

A series of well-exposed Paleogene sedimentary successions in the Kohat Basin of northwestern Pakistan (western Himalayas), are used to document the development of Paleogene sedimentary sequence deposited in a clastic–carbonate–evaporate distally steepened to a homoclinal ramp setting. Larger benthic foraminifer stratigraphy, sedimentology and microfacies were used to reconstruct the depth of deposition of the sediments and to aid in reconstructing the subsidence history of the sedimentary basin through the Paleogene. Based on the timing of the cessation of marine sedimentation and the subsidence analysis of the Paleogene rocks of the Kohat Basin, we conclude that a proto-closure of the basin occurred in the early Eocene (Ypresian) at ca 50–49.5 Ma, followed by return of marine sediments, with full closure of the Tethys seaway in the middle Eocene ca 40–41.2 Ma (Lutetian), potentially resulting in diachroneity of emergence of basins along strike of the orogen.

KEY POINTS

1. Paleogene Larger Benthic Foraminferal biostratigrphy and facies information in the Eastern Tethys segment of the Kohat Basin, Pakistan are presented.

2. Distally steepened-homoclinal ramp deposits were found.

3. The proto-closure of Tethys occurred around 49.5 Ma with complete closure at 41.2–40 Ma due to India-Asia collision.

Keywords:

• Paleogene
• Kohat Basin
• Tethys
• ramp
• benthic foraminifera
• sedimentology
• microfacies

Acknowledgements

JR acknowledges support by the College of Petroleum Engineering & Geosciences of the King Fahd University for Petroleum and Minerals (Dhahran, KSA).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The logistic and financial support by the Commonwealth Scholarship Commission (CSC), UK, and the Higher Education Commission (HEC) of Pakistan is highly acknowledged for the successful completion of this study.