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

By Peter D. Warwick, Shahid Javed, S. Tahir A. Mashhadi, Tariq Shakoor, Asrar M. Khan, and A. Latif Khan

CONCLUSIONS

The Lumshiwal and Hangu Formations of the Surghar Range of north-central Pakistan are lithologically similar and were deposited in what we interpret to have been similar depositional environments of shallow-marine and deltaic settings. The two formations are separated by a disconformity and possible sequence boundary that represent a hiatus of approximately 30 million years (from Aptian or Albian to Paleocene). Palynological data (Frederiksen and others, in press; Khan, appendix III) indicate that the age of the Lumshiwal is Early Cretaceous, not Late Cretaceous as previously reported by Danilchick and Shah (1987). A middle Paleocene age is confirmed in this study for the Hangu Formation. The contact between the formations is commonly associated with possibly Paleocene lateritic paleosols that developed on exposed Early Cretaceous Lumshiwal rocks. This disconformity, which has been defined stratigraphically by palynological studies, is graphically displayed on a cross section of the Surghar Range (figure 4). The peat deposits that later formed the Makarwal coal bed (average thickness 1.2 m) developed on these lateritic deposits probably in response to a rise in the relative ground-water base level. The rise in base level probably was driven by tectonic influences, but climatic and eustatic influences are not excluded. The Makarwal coal bed represents a transitional lithology that formed in a depositional setting that changed from laterite formation associated with the unconformity to mires associated with deltaic environments of the Hangu Formation. The upper part of the Hangu Formation and the Lockhart Limestone represent the culmination of marine transgression. The rapid change in the thickness of the Lumshiwal and Hangu Formations, over a distance of about 20 km, suggests that tectonic forces such as active basement faulting may have influenced deposition of both formations.

Analytical data from the Makarwal coal bed indicate that the apparent rank of the coal bed ranges from high-volatile B to high-volatile C bituminous (Landis and others, 1971). Averaged, as-received results from analytical tests indicate that Hangu coal deposits in the Surghar Range contain 5.4 percent moisture, 12.5 percent ash, and 5 percent total sulfur and have an average calorific value of 11034 Btu/lb. Trace-element analyses indicate that Hangu Formation coal beds contain concentrations of the environmentally sensitive element selenium (average 13.4 ppm); these concentrations are relatively high when compared to concentrations from similar United States coals. Structural complications and a significant overburden have prevented major development of the coal deposits and have limited mining to the outcrop area of the Hangu in the Surghar Range.

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