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Age and provenance of limestone clasts in Lower Old Red Sandstone conglomerates: implications for the geological history of the Midland Valley Terrane

Howard A. Armstrong
Howard A. Armstrong
Department of Geological Sciences, University of Durham, South Road, Durham DH1 LE, UK (e-mail:
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Alan W. Owen
Alan W. Owen
Division of Earth Sciences, Department of Geography, University of Glasgow, Gregory Building, Lilybank Gardens, Glasgow G12 8QQ, UK
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January 01, 2000


Conodont-bearing limestone clasts in Lower Old Red Sandstone conglomerates in the Lanark and Strathmore basins and the Pentland Hills Inlier, Midland Valley, Scotland, indicate a source in a cryptic arc terrane with a mid-Ordovician (P. serraP. anserinus Biozone) limestone cover. Simpson coefficients of similarity indicate that the faunas from the limestone clasts are closer to conodont faunas from the Holy Cross Mountains, Poland, and the Wrae Limestone in the Northern Belt of the Southern Uplands, than to those in coeval strata from the Laurentian margin including Girvan. Conodont colour alteration index values indicate separate thermal histories for the limestone clasts and coeval strata in the Girvan Inlier. The cryptic arc was located to north of the Northern Belt of the Southern Uplands during Ashgill time and to south of the Midland Valley in Late Silurian–Early Devonian time and clearly had a complex tectonic history.

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Geological Society, London, Special Publications

New Perspectives on the Old Red Sandstone

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




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