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Book Chapter

Sedimentology, cyclicity and floodplain architecture in the Lower Old Red Sandstone of SW Wales

By
Susan E. Love
Susan E. Love
1
Department of Geology and Petroleum Geology, University of Aberdeen, Meston Building, Aberdeen AB24 3UE, UK (e-mail: b.williams@abdn.ac.uk)
2
Present address: ExxonMobil International Ltd, Mobil Court, 3, Clements Inn, London WC2A 2EB, UK (e-mail: sue_love@email.mobil.com)
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Brian P. J. Williams
Brian P. J. Williams
1
Department of Geology and Petroleum Geology, University of Aberdeen, Meston Building, Aberdeen AB24 3UE, UK (e-mail: b.williams@abdn.ac.uk)
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Published:
January 01, 2000

Abstract

The high-quality, laterally continuous coastal exposures of the Moor Cliffs Formation have allowed a highly detailed 2D reconstruction of the floodplain sediments and their contained pedogenic horizons to be made. The thick siltstone packages were actively deposited as finely laminated and rippled sheets, or as intraformational clasts forming larger bedforms. It is proposed that the unusual sediment geometries preserved are intimately related to the timing of land plant colonization of the Old Red Sandstone continent. Channels were extremely broad with low relief and flow over interfluvial areas was common. Evidence for ephemerality and regular desiccation is also closely related to the lack of rooted vegetation and not to palaeoclimate, which is postulated to be warm and seasonally wet. The low net sandstone (< 10%) fluvial sediments are the product of deposition by shallow, high width to depth fluvial ‘channels’ flanked by broad, low-relief silty plains on which Vertisols formed. The reconstructions of this fluvial system reveal distinctive and systematic vertical and lateral variations in floodplain architecture and palaeosol development. Pedogenic maturity consistently increases with distance both vertically and laterally from channels. The vertical patterns of palaeosol development and maturity suggest that autocyclic processes of aggradation and avulsion predominated.

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Contents

Geological Society, London, Special Publications

New Perspectives on the Old Red Sandstone

Geological Society of London
Volume
180
ISBN electronic:
9781862394285
Publication date:
January 01, 2000

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