Abstract:
The Late Paleocene (Thanetian) Lockhart Limestone, exposed in the Nammal
Gorge, Salt Range and Harnoi section Abbottabad. It is composed of light to dark
grey and thin to medium bedded limestone. In total 32 samples were taken from the
Harnoi and Nammal Gorge section i-e 17 samples from Harnoi section and 15
samples from the Nammal Gorge. The samples were taken for the petroghraphy
analysis.The Formation is rich in larger benthic foraminifera, four microfacies were
established in the measured sections i.e. MLLN-1 Lockhartia Assilina Packstone
Microfacies and MLLN-2 Foraminiferal Wackstone Microfacies representing
microfacies of the Nammal Gorge and MLLH-1 Bioclastic Mud-Wackstone
Microfacies and MLLH-2 Planktonic Mudstone Microfacies representing the
microfacies of the Harnoi section. The depositional environment of both section
microfacies were also different.The MLLN-1 Lockhartia Assilina Packstone
Microfacies representing the inner ramp environmment, MLLN-2 Foraminiferal
Wackstone Microfacies indicates the middle ramp environment of the Nammal Gorge
and microfacies of the Harnoi section MLLH-1 Bioclastic Mud-Wackstone
Microfacies represents the outer ramp environment and MLLH-2 Planktonic
Mudstone microfacies representing open marine settings. The analysis further showed
that various diagenetic modifications observed in the Lockhart Limestone include
micritization, dissolution, compaction (chemical and mechanical), fractures and
calcite veins. The micritization, dissolution and unfilled fractures in the studied rock
unit enhance the porosity where as neomorphism and mechanical compaction lead to
porosity occlusion and thus impacts on the reservoir potential.
