Lithofacies and Palynostratigraphy of Some Cretaceous and Paleocene Rocks, Surghar and Salt Range Coal Fields, Northern Pakisatan

摘要

The stratigraphic relation between the Cretaceous generally noncoal-bearing Lumshiwal Formation (64 to 150 mthick) and the Paleocene coal-bearing Hangu Formation (5to 50 m thick) in the Surghar Range of north-central Pakistan is complex. Both formations contain remarkably similar lithofacies: one or two types of sandstone lithofacies; a combined lithofacies of mudstone, claystone, carbonaceous shale, and coal beds; and a rare carbonate lithofacies. Ananalysis of pollen data from rock samples collected from various stratigraphic positions indicates that the formations are separated by a disconformity and that the age of the Lumshiwal Formation is Early Cretaceous and the age ofthe Hangu is Paleocene. Previous workers had suggested that the age of the Lumshiwal is Late Cretaceous. An analysis of sedimentologic, stratigraphic, and pale-ontologic data indicates that both the Lumshiwal and Hangu Formations probably were deposited in shallow-marine and deltaic environments. The rocks of the Lumshiwal become more terrestrial in origin upward, whereas the rocks of the Hangu become more marine in origin upward. The contact between the two formations is associated with a laterally discontinuous lateritic paleosol (assigned to the Hangu For-mation) that is commonly overlain by the economically important Makarwal coal bed. This coal bed averages 1.2 min thickness.