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This article describes a study which examined the microfacies and depositional environments of the Margalla Hill Limestone from the Kohala-Bala area in Haripur in Hazara, Pakistan. The Margalla Hill Limestone is characterized by a wide variety of faunal and floral assemblages. The microfacies identified include Miliolid Lockhartia Mud-Wackstone Microfacies, Nummulitic Wack-Packstone Microfacies and Benthic Foraminiferal Wack-Packstone Microfacies.

In this paper we have used the outcrop data and utilized facies analysis techniques for the dynamic depositional modeling of Chhidru Formation, exposed in the Nammal Gorge and the Chhidru Nala sections in the Salt Range, Upper Indus Basin of Pakistan. Based on the integrated field and petrographic criteria, five different facies types i.e., CHF-1-CHF-5 are recognized. The CHF-1 corresponds to the sandy limestone interbedded with clays facies while CHF-2 is a medium bedded sandy limestone facies. The CHF-3 is represented by the massive sandy limestone facies. The CHF-4 (calcareous sandstone facies) and CHF-5 (thick bedded to massive white sandstone facies) have been identified in the upper part of the two stratigraphic sections. The depositional characteristics of these facies are consistent with the proximal inner shelf to distal middle shelf settings of a siliciclastic-carbonate mixed platform. Based on the integration of the outcrop data, facies information and fusulinid biostratigraphy the dynamic depositional model of the Chhidru Formation is presented. The new data enabled identification of two (02) 3rd order Transgressive-Regressive depositional sequences. The first Transgressive Sequence consists of the Transgressive Systems Tract (TST 1) that further constitutes six parasequences. The second transgressive depositional sequence constitutes the second Transgressive Systems Tract (TST 2) with no significant parasequence. The chronologic calibration fusulnid biostratigraphic age of the Chidru Formation suggest that deposition of the at the base TST 1 started at 252.5 Ma and the topmost beds of TST 2 corresponds to 253.8 Ma, respectively. The global comparison of the relative sea level during 252.5-253.8 Ma shows prominent eustatic signatures, however the flooding surfaces bounding the parasequences are ascribed to the local tectonics. [ABSTRACT FROM AUTHOR]

The southeast Hazara forms a part of Himalayan fold and thrust belt of Pakistan. The study area is covered by Mesozoic-Cenozoic age rocks that have undergone severe deformation and is characterized by the formation of complex fold and thrust assemblages. The structures include northwest and southeast verging thrust systems with associated folds. Two deformational events separate the structures in the area. The structures in the northwestern quadrant display southeast facing direction whereas the southeastern quadrant is dominated by structures that dip towards southeast. The general trend of the structures is northeast- southwest and that attributes to the northwest-southeast contractile deformation. The trend of the structures depicts that stresses were directed from northwest. The folds are found to be tight to overturned and the cores of the folds are usually occupied by competent Samana Suk Formation. The organic rich horizons were observedin the field within the Formation, the TOC of which was calculated as 0.28%. Microfacies analysis reveals well sorted and well-rounded ooidal-peloidal grainstones and packstones as well as dolomitized and fractured wackestones and mudstones. The diagenetic signatures include fracturing and dolomitization depicting its source and reservoir quality for a hydrocarbon prospect. [ABSTRACT FROM AUTHOR]

The diagenetic fabric and its implications for the thin section porosity in carbonate facies of the Margala Hill Limestone in the Haripur area of North Pakistan is documented here. The facies analysis suggests deposition of the unit in a carbonate shelf platform setting having characteristic sediments of the inner shelf lagoon to middle shelf subtidal environments. The diagenetic overprinting of these facies includes micritization, neomorphism (microspar, aragonite calcite transformation, dolomitization) and compaction (disorientation of biocalst, pressure dissolution fabric). The inner shelf facies have an enhanced porosity due to transformation of calcite to dolomite and micritization of skeletal fragments. The occlusion of the effective porosity in the middle shelf and sub-tidal distal shelf facies is related to the stylonodular, stylobrecciated fabric and calcite filled veins. The overall assessment of the unit suggests that the middle part of rock intervals have fair porosity (8-13%), in contrast to the lower and upper part which has negligible porosity (0-5%). [ABSTRACT FROM AUTHOR]

In this paper a detailed stratigraphic analysis of the Middle to Late Permian Wargal Limestone in the Western Salt Range area of the Potwar Basin in north Pakistan is presented. The outcrop data and microfacies analysis suggested that deposition of the Wargal Limestone occurred in the inner shelf to middle shelf-lagoon setting. A regional sequence stratigraphic model of the study unit, with a particular emphasis on the diagenetic fabric of different microfacies has been developed. In this study four, third order depositional sequences (1-4) are recognized. These sequences constituted three Transgressive Systems Tracts (TST 1-3) and four Regressive Systems Tract (RST 1-4). Based on the facies criteria a relative sea level curve is constructed and a comparison with the global sea level curves is made. The relative sea level fall at the 259.6 Ma and 254 Ma in the study area have a global signature, while the 263 Ma fall might be related to the interplay of the local tectonics and sediment supply. The synergy of the diagenetic fabric, results of the XRD, porosity/permeability analysis revealed that best hydrocarbon reservoir qualities exists in the dolomite facies in the middle and upper part of the study unit. The overall hydrocarbon reservoir potential of the Wargal Limestone is moderate to high. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]