PETROGRAPHY OF THE EARLY PERMIAN (ASSILIAN) TOBRA FORMATION, EASTERN SALT RANGE, POTWAR BASIN, PAKISTAN: IMPLICATIONS ON PROVENANCE, TECTONIC SETTINGS AND ENVIRONMENT OF DEPOSITION

  • SHAHID GHAZI Institute of Geology, University of the Punjab, Lahore-54600, Pakistan
  • HAFIZ JAWAD SOHAIL Institute of Geology, University of the Punjab, Lahore-54600, Pakistan
  • TANZEELA HANIF Institute of Geology, University of the Punjab, Lahore-54600, Pakistan
  • FARHAT RASS MASOOD Department of Botany, University of the Punjab, Lahore-54600, Pakistan

Abstract

The end of the Gondwana sedimentation in the Salt Range is represented by the glacio-fluvial Tobra Formation, which is composed of diamictite, tillite and fresh water facies. Clast supported and matrix supported conglomerates represent the basic lithology of the Tobra Formation. The sandstone is present as matrix in the conglomerate beds. An integrated petrographic study of the sandstone units of the Tobra Formation was carried out to interpret the provenance and tectonic settings. This analysis is based on the thin section study of samples collected from four different sections (Pidh, Tobar, Watli and Wahali Bala sections) of the Eastern Salt Range. On the basis of framework grains, the sandstone is classified as lithic arkose to feldspathic arenite or subarkosic to sublitharinite. Thin section study reveals that the sandstone of the Tobra Formation has quartz, feldspar and rock fragments along with some accessory minerals. Monocrystalline quartz is most abundant while polycrystalline quartz is also present. Feldspar in the form of albite, microcline and perthite is present in the sandstone. Rock fragments of igneous (granitic), metamorphic as well as sedimentary rocks are present. Accessory minerals such as mica, hematite and chlorite are also present. A few amount of cement in the form of ferruginous clay is present which indicates submature stage of sandstone. Grains are subrounded to subangular in shape and grain boundaries are mostly concavo convex and sutured which depict intermediate level of compaction. Varying population of moderately to poorly preserved palynomorphs were also observed at various horizons. The petrographic study suggests that the Tobra Formation has plutonic granitic (igneous) or metamorphic provenance. Petrographic point count data indicates that the tectonic settings are recycled orogeny. Paleogeographic history of Gondwanaland indicates that the Aravalli Range and Melani System are the main sediment source area of the Tobra Formation in the Salt Range of Pakistan.

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Published
2017-06-21
How to Cite
GHAZI, SHAHID et al. PETROGRAPHY OF THE EARLY PERMIAN (ASSILIAN) TOBRA FORMATION, EASTERN SALT RANGE, POTWAR BASIN, PAKISTAN: IMPLICATIONS ON PROVENANCE, TECTONIC SETTINGS AND ENVIRONMENT OF DEPOSITION. Arabian Journal of Earth Sciences, [S.l.], v. 4, n. 2, p. 6, june 2017. ISSN 2409-4730. Available at: <http://asrongo.org/journals/index.php/AJES/article/view/59>. Date accessed: 19 dec. 2018.

Keywords

Permian Sedimentation; Paleoclimate; Petrography; Depositional Model