Degree Type

Dissertation

Date of Award

1981

Degree Name

Doctor of Philosophy

Department

Geological and Atmospheric Sciences

Abstract

The Cretaceous strata exposed in the southern Pab Range, southeast Baluchistan, Pakistan record the post-Gondwana, pre-collision depositional history of the Indo-Pakistani continental shelf. The strata comprise two depositional successions, namely, The Early to Late Cretaceous Sembar-Goru-Parh sequence and the Maestrichtian Mughal Kot-Pab sequence. The former began with deposition of black shales on the continential slope (Sembar Formation), succeeded by calcareous shale, marl and micstone of outer shelf origin (Goru Formation), and ended with inner shelf platform carbonates (Parh Limestone). These deep to shallow water lithofacies prograded westward over the continental shelf of the north-advancing Subcontinent;The Mughal Kot-Pab progradation contains the first significant influx of terrigenous sand reaching the western portion of the continental shelf. Depositional environments in the Mughal Kot Formation include inner shelf, prodelta, delta front and distributary channel. A thick succession of shoreface cycles comprises the Pab Sandstone. The coarsening upward cycles display lithofacies indicative of offshore marine, transitional marine and lower shoreface environments;Quartzarenites comprise the sandstones of the lower Mughal Kot. The quartz detritus was derived from the northern Indian Shield. An ultrastable heavy mineral suite, dominated by zircon, tourmaline and rutile indicates a high mineralogical maturity for the plutonic detritus transported to the Tethyan shoreline. In the upper Mughal Kot and persisting throughout the Pab Sandstone, a volcanic rock fragment admixture is present. The fragments were derived from fine-grained andesite/basalt flows that are believed to have been part of the Porali Volcanic Arc, postulated to have formed further west on continental margin. A back arc tectonic regime is proposed for mixing of plutonic and volcanic detritus. The setting initiated a narrow, rapidly subsiding shelf which is believed responsible for the cyclic Pab sedimentation.

DOI

https://doi.org/10.31274/rtd-180813-5705

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Howard James White

Language

en

Proquest ID

AAI8128867

File Format

application/pdf

File Size

177 pages

Included in

Geology Commons

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