The Middle Permian (Capitanian) carbonate platform evolution and stratigraphic architecture of aNeo‐Tethysrim basin, Central Pakistan

Abstract

Here we present the stratigraphic architecture and carbonate platform evolution of the Middle Permian (Capitanian) succession (Wargal Formation) of Trans‐Indus Ranges, central Pakistan. The exposed carbonate sequence consists of thin‐ to thick‐bedded bioclastic, nodular, fine‐grained, and sandy limestone. Based on detailed petrographic studies, seven microfacies assemblages have been recognized, suggesting diverse depositional environments including mudflats, lagoon, sand shoal, and middle shelf. The identified age‐diagnostic larger benthic foraminiferal species enabled to assign a Middle Permian (Capitanian) age to the studied section of the Wargal Formation. Based on the vertical arrangements of depositional environments in time, three Transgressive Systems Tracts (TSTs), two Regressive Systems Tracts (RSTs), and 11 high‐resolution fourth/fifth‐order parasequences were delineated. The depositional and sequence stratigraphic analyses of the studied section inferred evolution of the Middle Permian carbonate platform in three stages: (i) marginal marine facies development in the lower part followed by (ii) transitional stage in the middle part, and (iii) finally, aggrading shallow marine facies stage in the upper part. The evolution of carbonate platform can be linked with the cessation of major rifting followed by thermal cooling and establishment of marine Tethyan settings at the margin of the rift flank basin. The diverse facies variation in the second stage of platform evolution argues strongly for the local intra‐plate stresses. Based on petrographic, SEM, and EDS studies, it is concluded that the studied section of Wargal Formation carries porosity values from a range of 2–8% with an average of 5% and can be called a low to moderate hydrocarbon reservoir in the study area.

Microfacies analysis of the Palaeocene Lockhart limestone on the eastern margin of the Upper Indus Basin (Pakistan): Implications for the depositional environment and reservoir characteristics

“…The presence of a high micrite concentration indicates deposition in a low‐energy environment. Micritisation, cementation and spar are common in a middle shelf environment (Wadood et al, 2021). Deposition on the middle shelf is suggested in conjunction with the fossil content of these facies.…”

Dating and tectonostratigraphy of the Early Jurassic rift delta at the northwestern margin of the Indian Plate, Pakistan

“…The continental settings of Early Permian have deposited glacial to fluvial and lacustrine sediments over the Cambrian strata (Ghazi, Mountney, Butt, & Sharif, 2012). The Middle Permian climatic transition has replaced the continental setting with a carbonate platform, while the platform demise is attributed to the Permo- Triassic Boundary (Wadood et al, 2021a). The onsets of dominant marine to marginal marine settings were established during the Triassic and have deposited the Mianwali, Tredian, and Kingriali formations (Shah, 2009).…”

The Late Permian clastic–dominated carbonate shelf, Northwestern Pakistan: Implications for palaeoenvironments, palaeoclimate, and reservoir modelling

“…However, in each section, variation in distribution and thicknesses of the siliciclastic bioclastic wackestone microfacies is recorded. Furthermore, the carbonate contents including skeletal and non-skeletal components were domi- , Mertmann, 2003;Shah, 2009;Wadood et al, 2021c). However, an increase in the terrigenous input has subsequently changed the depositional facies of the overlying Chhidru Formation, where the carbonate factory was gradually dormant in the lower and middle part of the rock unit.…”