Diagenetic analysis of the Early Eocene Margala Hill limestone, Pakistan: A synthesis for thin section porosity
Keywords:
Eocene; Diagenetic overprinting; North Pakistan.Abstract
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%).
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