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Abstract: Tithonian to Danian Sedimentation in Hazara Basin, Northern Pakistan

AHSAN, N., Inst. of Geology, Punjab University, Lahore, Pakistan

Tithonian to Cenomanian in the Hazara basin of Northern Pakistan is characterized by quartz arenites (Lumshiwal Formation) which are cemented with quartz, clay, iron oxides or glauconite. They were deposited in mildly reducing environment in subtidal depositional regime. The average lithified rates of sedimentation were about 0.96mm/1000 years

In the Cenomanian due to rapid northwards flight of India from near Madagascar the Hazara basin started to sink gradually to deposit the Kawagarh Formation. The formation is composed of pelagic limestones and marls with globogerinids and oligostegina.

The study of the four sections of the Kawagarh Formation located in the Hazara basin shows that they are generally composed of glauconitic arenaceous mudstones, mudstones, packstones, dolomitic mudstones to dolomitic wackestones, dolomites and marls. The average lithified rates of sedimentation were about 9mm/1000 years which compares favorably with the American and European chalks.

On the basis of the microfacies and planktonic fauna it can be concluded that the depth of the Tethys Sea in the Late Cretaceous in the Hazara basin was not more than 250m. The base and top of the Kawagarh Formation were deposited at relatively shallower depths (up to 80-100m) with input of detrital quartz.

The top of the Kawagarh Formation exposed subaerially when the Indian Plate established its first contact with the Kohistan Island Arc at about 67 +/- 2 ma. This reworked the Maastrichtian sediments into pisolitic laterites, bauxites and fireclays now represented by Hangu Formation of Danian age.

AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid