Microfacies Analysis And Depositional Environment Of Jurassic Samana Suk Formation, Township Section Abbottabad, Pakistan

Abstract

The present study deals with the microfacies and depositional environment of the Jurassic Samana Suk Formation Township section of Abbottabad. The Samana Suk Formation consists of a carbonate unit deposited in Attock-Hazara Fold and Thrust belt of the north-western Himalayas and represents a region with well-developed stratigraphic and structural geological exposure. Field observations demonstrate that the Samana Suk Formation is widely distributed in the studied section with thin to thick-bedded, oolitic, bioclastic, and dolomitic limestone unit having skeletal and non-skeletal grains. The studied section that is the Township section was logged and sampled in detail for the petrographic analyses in an attempt to reveal the microfacies analysis, depositional and diagenetic settings. Thirty-seven thin sections were prepared for microscopic analysis resulting in the identification of nine microfacies (MF1-MF9). These microfacies are Mudstone (MF1), Dolomudstone (MF2), Bioclastic peloidal wackestone (MF3), Peloidal packstone (MF4), Ooidal grainstone (MF5), Bioclastic ooidal grainstone (MF6), Peloidal grainstone (MF7), Bioclastic intraclastic grainstone (MF8) and Intraclastic bioclastic peloidal grainstone (MF9) that are deposited in different environmental settings. Diagenetic processes including Micritization, Bioturbation, Neomorphism, Compaction, Fractures and veins, Dissolution, Cementation, Dolomitization and Pyritization have been observed in the petrographic study of the samples. Based on the microfacies analysis, the Mudstone (MF1), Bioclastic peloidal wackestone (MF3) and Peloidal packstone (MF4) deposited in lagoonal while Ooidal grainstone (MF5), Bioclastic ooidal grainstone (MF6), Peloidal grainstone (MF7), Bioclastic intraclastic grainstone (MF8) and Intraclastic bioclastic peloidal grainstone (MF9) reveal deposition on carbonate shoal settings of inner ramp. The deposition of Dolomudstone (MF2) directly belongs to the inner ramp. It is concluded that the Jurassic Samana suk Formation in the Studied section is characterized by nine microfacies reflected deposition in the lagoon, shoal, and inner ramp of homoclinal carbonate ramp affected by different dig