Lithofacies Depositional Environments And Regional Stratigraphy Of The Lower Eocene Ghazij Formation Balochistan Pakistan

Author : Ahmad Khan
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (133 download)

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Download or read book Lithofacies Attributes, Depositional Environments, Biostratigraphy and Cyclicity of the Lockhart Limestone, Upper Indus Basin, Northern Pakistan written by Ahmad Khan and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Indian Subcontinent contained a wide shallow marine continental shelf during most of the Paleocene and Eocene epochs before its collision with Eurasia. The Indus Basin formed the Pakistani portion of the subcontinent where carbonate deposition was prominent. The Lockhart Limestone is among the carbonate-dominated lithologic units developed in the Indus Basin. The latter has been divided into sub-basins due to the tectonic disturbance related to the Indian-Eurasian collision. In the northern part of the Indus Basin, the sub-basins Kohat, Potwar and Hazara constitute the upper Indus Basin. The study area is located in the Potwar and Hazara sub-basins. The Lockhart Limestone overlies early Paleocene Hangu Formation and is overlain by latest Paleocene to early Eocene Patala Formation, both with confirmable contacts. The Lockhart Limestone is 50 meters thick in the Potwar Sub-basin and 85 meters thick in the Hazara Sub-basin. Seven sections, three from Hazara area and four from Potwar area were studied for lithofacies characteristics, depositional environment, biostratigraphy, cyclicity and sequence stratigraphy of the Lockhart Limestone. The different lithofacies occur in different stratigraphic horizons that constitute the formation; they include fossiliferous calcareous shale (Lf1), planktonic-bearing mudstone (Lf2), Discocyclina-Ranikothalia wackestone (Lf3), mixed benthic foraminiferal wackestone-packstone (Lf4), Lockhartia-Miscellanea wackestone-packstone (Lf5) algal-foraminiferal wackestone-packstone (Lf6) and milliolid-bearing mudstone (Lf7). These lithofacies accumulated in subtidal conditions as suggested by their lithologic properties, fossil content and absence of intertidal and supratidal signatures. However, the vertical arrangement of these facies make cyclicity, as each cycle contains different lithofacies that change from deeper to shallower facies ii (A, B, C& D). The depositional setting is a ramp-type platform in which Lf1, Lf2 and Lf3 represent the deepest facies (outer ramp) followed by Lf3, Lf4 and Lf5 accumulated in the middle ramp, and finally by Lf6 and Lf7 of the inner ramp setting. Some of the larger benthic foraminifera are good index fossils that are useful for biostratigraphic age determination. These index fossils include Lockhartia conditi, L. haimei, Miscellanea miscella, Ranikothalia sindensis, and Discocyclina sp, which indicate Thanatian SBZ 3 & 4 (58 -56.5 Ma) age for the formation. Nine meter-scale shallowing-upward (Milankovitch) cycles were recognized from the Lockhart Limestone. In conjunction with the underline Hangu Formation and overlying Patala Formation, two transgressiveregressive cycles (TR-1 and TR-2) divide the HLP cycle in two parts. The Lockhart Limestone with the upper part of underlying Hangu Formation and the lower to middle part of overlying Patala Formation were deposited in a single 3rd order cycle (the HLP cycle).