Sequence stratigraphic framework of the Maastrichtian shelfal to deep marine strata of Lower Indus Basin, Pakistan: implications for the petroleum potential

摘要

The present study integrates the facies and planktonic foraminiferal biostratigraphic data to construct a sequence stratigraphic model of the Mughal Kot Formation of Maastrichtian age in the Lower Indus Basin, Pakistan. The Mughal Kot Formation is comprised of 1000-m-thick sequence of hemipelagic sediments, interrupted by random influxes of coarse-grained sandy turbidites. The petrographic details revealed six sub-microfacies, indicating deposition in the middle shelf, slope and deep marine basin. The sequence stratigraphic model is based on the integration of biostratigraphic age and local depositional signals in the study area. The studied sedimentary succession is divided into one second-order and two third-order cycles while ten parasequences are identified within the complete cycles of transgressive, highstand and lowstand systems tracts. The depositional trends within the relative sea level curve of the Maastrichtian strata of the study area and the global sea level charts are quite dissimilar, which suggest a sustained transgression with pulsated tectonics in Lower Indus Basin. The integrated results of plug porosity/permiability and petrography reveal poor reservoir potential for the sandy turbidites and pelagic carbonates of the Mughal Kot Formation.