Ghazi, S, Mountney, NP and Sharif, S (2015) Lower Permian fluvial cyclicity and stratigraphic evolution on the northern margin of Gondwanaland: Warchha Sandstone, Salt Range, Pakistan. Journal of Asian Earth Sciences, 105. 1 - 17. ISSN 1367-9120
Abstract
During the Lower Permian (Artinskian), fluvial conditions prevailed in what is now the Salt Range of northern Pakistan. Deposits of the Warchha Sandstone are characterised by a range of fluvial facies and architectural elements that together record both the proximal and distal parts of a meandering river system that drained the northern margin of Gondwanaland. Stratigraphic units are arranged into vertically stacked fining-upward cycles represented by thin accumulations of channel-lag deposits at their bases, and sandstone-dominated channel fill and thicker accumulations of overbank mudstone at their tops. Sedimentary cyclicity records fluvial system development on a variety of spatial and temporal scales. Overall, the Warchha Sandstone preserves a series of three to ten vertically stacked fining-upward cycles that form part of a larger-scale, third-order sequence that is itself bounded by regionally extensive and laterally correlatable unconformities that were generated in response to combined tectonic and eustatic changes. The sequence-stratigraphic architecture reflects regional palaeogeographic development of the Salt Range region. The small-scale fluvial cycles originated through autogenic mechanisms, predominantly as a result of repeated channel avulsion processes that occurred concurrently with on-going subsidence and the progressive generation of accommodation. Each erosively based fining-upward fluvial cycle is divided into three parts: a lower part of trough cross-bedded conglomerate and coarse sandstone; a middle part of tabular cross-bedded, ripple cross-laminated and horizontally laminated sandstone; and an upper part of predominantly horizontally laminated and massive mudstone. Overall, the Warchha Sandstone records the progradation of a wedge of non-marine strata into a previously shallow-marine depositional setting. The underlying marine Dandot Formation is terminated by a major unconformity that represents a type-I sequence boundary associated with a regional relative sea-level fall and a significant regression of the Tethyan shoreline. The overlying Warchha Sandstone represents the onset of the subsequent lowstand systems tract in which a northward-flowing meandering river system redistributed clastic detritus derived from a tectonically-active source area (the Aravalli and Malani ranges) that lay to the south. This episode of fluvial sedimentation was terminated by a widespread marine transgression recorded by an abrupt upward transition to estuarine and shallow-marine deposits of the overlying Sardhai Formation. This change marks the transition from lowstand deposits to a transgressive system tract.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2015, Elsevier. This is an author produced version of a paper published in Journal of Asian Earth Sciences. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Fluvial; Cyclicity; Stratigraphic evolution; Gondwanaland; Lower Permian; Warchha Sandstone; Salt Range |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Institute for Applied Geosciences (IAG) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 05 Nov 2015 12:36 |
Last Modified: | 31 Mar 2016 13:06 |
Published Version: | http://dx.doi.org/10.1016/j.jseaes.2015.03.001 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.jseaes.2015.03.001 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:89056 |