Biostratigraphic investigation and depositional model of the Late Thanetian Ranikot and the Ypresian Laki formations in the subsurface of the Southern Indus Basin, Pakistan

摘要

Biostratigraphic investigation of the subsurface-equivalent Ranikot and Laki formations from the Southern Indus Basin Pakistan was performed in this study. The biostratigraphic study of these formations indicates five shallow benthic zones (SBZ). These zones are characterized as SBZ5, SBZ6, SBZ7, SBZ10, and SBZ11. The biostratigraphic investigation of the Ranikot Formation suggests SBZ5. This particular zone is established based on the appearance of the index zonal marker Miscellanea miscella. Based on SBZ5, and Miscellanea miscella, the Late Paleocene (Late Thanetian) age is assigned to Ranikot Formation. Foraminiferal assemblage and microfacies analyses elucidate that Ranikot Formation was deposited in the outer ramp setting. Biostratigraphic evaluation of the Laki Formation indicates the presence of four shallow benthic zones. The zones are SBZ6, SBZ7, SBZ10, and SBZ11. These zones are assigned based on the presence of Alveolina pasticillata, Alveolina oblonga, Alveolina globosa, Alveolina elliptica, Nummulites globulus, and Alveolina elliptica nuttalli. The Early Eocene (Ypresian) age is assigned to Laki Formation based on recognized Alveolinids and shallow benthic zones. Foraminiferal assemblages and microfacies reflect that Laki Formation was deposited in the inner to outer ramp setting.