Biostratigraphy and depositional environments of the Early Eocene Margalla Hill Limestone, Kohala-Bala area, Haripur, Hazara Fold-Thrust Belt, Pakistan
Keywords:
Eocene; Shelf carbonates; North PakistanAbstract
This research paper deals in biostratigraphy and depositional environments of the Early Eocene Margalla Hill Limestone found in Kohala-Bala area, Haripur from the southern Hazara Fold-Thrust Belt (north western Himalayan Fold-Thrust Belt). The stratigraphy ranges in age from Pre-Cambrian to Holocene. The Margalla Hill Limestone having limestone with thin inter-beds of claystone and marl is 136m thick, and has conformable lower contact with Patala Formation of the Palaeocene age. The upper contact (conformable) with Chorgali Formation of the Eocene age is not exposed here.
The Margalla Hill Limestone is described here as having a wide variety of faunal and floral assemblage; includes larger benthic forams, planktic forams, echinoderms, mollusks and dasycladacean algae. Their comparative studies suggest Middle Illerdian-2 age. There were three microfacies recognized; 1) Miliolid Lockhartia Mud-Wackstone Microfacies, inferred the deposition in a low energy, restricted circulation with slightly high salinity in a lagoonal environment of the inner shelf, 2) Nummulitic Wack-Packstone Microfacies, inferred to be deposited in a subtidal conditions of the carbonate shelf and 3) Benthic Foraminiferal Wack-Packstone Microfacies, representing deposition in the distal middle shelf area relatively further offshore. The microfacies are frequent in the section, which reveal changing sea level conditions.
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