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Depositional setting of the Lower Old Red Sandstone at Pantymaes Quarry, central South Wales: new perspectives on the significance and occurrence of ‘Senni Beds’ facies

By
Geraint Owen
Geraint Owen
1
Department of Geography, University of Wales Swansea, Singleton Park, Swansea SA2 8PP, UK (e-mail: g.owen@swansea.ac.uk)
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Duncan Hawley
Duncan Hawley
2
Department of Education, University of Wales Swansea, Hendrefoelan, Swansea SA2 7NB, UK
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Published:
January 01, 2000

Abstract

The 200 m long face of Pantymaes Quarry, central South Wales, exposes part of the upper (Dittonian) Red Marl Group (Lower Old Red Sandstone). A lower Sandstone Facies Association (up to 15m thick) comprises interbedded grey–green micaceous sandstones, pebbly intraformational conglomerates, and grey siltstones. Major bounding surfaces define stacked channel complexes, representing the deposits of braided river systems. An erosively overlying Mudstone Facies Association (up to 15 m thick) comprises tabular-bedded, bioturbated and calcretized red siltstones and fine sandstones representing overbank deposits, possibly from a meandering system. The change in fluvial style is interpreted as a local response to pulses of oblique-slip movement on nearby fault systems. The period of fault activity resulted in the braided Sandstone Facies Association, the Mudstone Facies Association recording a gradual return to a meandering system. Individual pulses of activity produced the stacked channels within the Sandstone Facies Association. The Sandstone Facies Association is similar in character to the overlying Senni Beds, suggesting that ‘Senni Beds’ may describe a recurring, possibly tectonically controlled, braided channel facies in the Lower Old Red Sandstone.

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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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