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Title: | Study of Depositional Environment, Diagenesis and Source Potential of Early to Middle Jurassic Sarobi Formation, North Waziristan, N.W. Pakistan |
Authors: | NAVEED IQBAL |
Keywords: | Earth Sciences |
Issue Date: | 2022 |
Publisher: | Quaid I Azam University |
Abstract: | The Early to Middle Jurassic Sarobi Formation of North Waziristan comprised of two rock units, the lower one has thin-bedded grey to dark-grey color limestone constituting its dominant lithology, while the upper one is composed of black color shale. Dolomite rock is also found within the formation, forming a contact with limestone and shale. The formation has a thrusted lower contact with the underlying Spalga Formation and the upper contact is gradational with Isha Formation. Covering the north-western portion of the Indo-Pakistani plate, the formation is originally evolved as a remnant of shelf-slope sediments of Neo-tethys Ocean thrusted along Bela-Zhob-Waziristan and Khost Ophiolitic Complex. Locally, the formation has also tectonic associations with three of the nappes of the study area, the Vezhda Sar Nappe, Boya Nappe and Datta Khel Nappe. The detailed petrographic studies of the formation has yielded total of 10 different microfacies covering parts of three major facies associations i.e. Tidal Flat, Lagoonal and Carbonate Sand Shoal and Bank facies associations. The Tidal Flat Facies include; Dolomudstone (MF1) and Peloidal Wackestone (MF2). The Lagoon settings include; Mudstone (MF3), Bioclastic-Mudstone (MF4), Bioclastic-Peloidal Wackestone (MF5), Peloidal Grainstone (MF6) and Peloidal Packstone (MF7). The rest of facies cover part of Carbonate Sand Shoal and Bank Facies association and include Ooidal Grainstone (MF8), Peloidal-Ooidal Grainstone (MF9) and Bioclastic-Peloidal Packstone (MF10). Petrographic studies also reveal various diagenetic phenomena which have altered the rocks of the formation. The major diagenetic features exhibited by the formation include various types of cements such as equant or blocky calcite cements, drusy calcite cements and isopachous cements. Some of the facies have highly deformed and closely packed grains and a saw-tooth like features known as Stylolite both of which are representing the diagenetic phenomena of physical compaction and dissolution respectively. The deep burial or subsurface diagenesis can be illustrated via phenomena of dolomitization and pyritization within these rocks. The presence of calcite veins gave indication for late-stage diagenesis, telogenesis or telodiagenesis. The geochemical analyses of these rocks were done for evaluating its source potential. For this purpose there total 6 different representative samples were subjected to TOC (wt %) and Rock-Eval pyrolysis analysis. The results obtained from these analyses gave determination for the Kerogen type-III of formation and categorizing the formation as poor in organic matter and source potential. |
URI: | http://hdl.handle.net/123456789/25851 |
Appears in Collections: | M.Phil |
Files in This Item:
File | Description | Size | Format | |
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EAR 1986.pdf | EAR 1986 | 2.8 MB | Adobe PDF | View/Open |
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