Near-Surface Shrinkage and Carbonate Replacement Processes, Arran Cornstone Formation, Scotland

  1. V. Paul Wright3 and
  2. Maurice E. Tucker4
  1. S. K. Tandon1 and
  2. Peter F. Friend2

Published Online: 8 APR 2009

DOI: 10.1002/9781444304497.ch16

Calcretes

Calcretes

How to Cite

Tandon, S. K. and Friend, P. F. (1991) Near-Surface Shrinkage and Carbonate Replacement Processes, Arran Cornstone Formation, Scotland, in Calcretes (eds V. P. Wright and M. E. Tucker), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304497.ch16

Editor Information

  1. 3

    Postgraduate Research Institute of Sedimentology (PRIS), University of Reading, UK

  2. 4

    Department of Geological Sciences, University of Durham, UK

Author Information

  1. 1

    Department of Geology, University of Delhi, Delhi 110007, India

  2. 2

    Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK

Publication History

  1. Published Online: 8 APR 2009
  2. Published Print: 13 JUN 1991

ISBN Information

Print ISBN: 9780632031870

Online ISBN: 9781444304497

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Keywords:

  • near-surface shrinkage and carbonate replacement processes - Arran Cornstone Formation;
  • Late Devonian or Early Carboniferous Cornstone Formation of Arran, overlying non-marine Upper Old Red Sandstone;
  • Arran Cornstone carbonates;
  • carbonate concretions occur between the fissures;
  • micromorphological interpretation, indicating growth of micrite

Summary

A 47 m thick succession of conglomerates, sandstones and mudstones, of Late Devonian or Early Carboniferous age, outcrops at Fallen Rocks in northeast Arran (western Scotland). It is defined here as the type section of the Arran Cornstone Formation. At numerous levels in the succession, varieties of fissures and carbonate concretions formed during the accumulation of the Formation. The fissures opened as a result of drying-shrinkage, and were closed again either by filling with different sediment, or by wetting and expansion of the fissure wall sediment. Carbonate concretions form complete beds, discontinuous, bedding-concordant sheets, or bedding-discordant nodules or rods (the rod cornstones). These concretions formed close enough to the surface to be incorporated, after erosion and redeposition, as clasts into overlying beds. The concretions were formed by growth of micrite, mainly by replacement, but shrinkage displacement played an important role in subsequently fracturing and reworking the micrite. The micrite was also locally replaced by microspar and spar, and this involved dissolution and precipitation. No independent evidence of biological influence in any of these processes has been found.