Biogenic Laminar Calcretes: Evidence of Calcified Root-Mat Horizons in Paleosols

  1. V. Paul Wright5 and
  2. Maurice E. Tucker6
  1. V. P. Wright1,5,
  2. N. H. Platt2,† and
  3. W. A. Wimbledon3

Published Online: 8 APR 2009

DOI: 10.1002/9781444304497.ch13



How to Cite

Wright, V. P., Platt, N. H. and Wimbledon, W. A. (1991) Biogenic Laminar Calcretes: Evidence of Calcified Root-Mat Horizons in Paleosols, in Calcretes (eds V. P. Wright and M. E. Tucker), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304497.ch13

Editor Information

  1. 5

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

  2. 6

    Department of Geological Sciences, University of Durham, UK

Author Information

  1. 1

    Department of Geology, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK

  2. 2

    Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK

  3. 3

    Geological Conservation Unit, Nature Conservancy Council, Northminster House, Peterborough, UK

  4. 5

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

  1. Geologisches Institut, Universität Bern, Baltzerstrasse 1, CH-3012 Bern, Switzerland

Publication History

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

ISBN Information

Print ISBN: 9780632031870

Online ISBN: 9781444304497



  • biogenic laminar calcretes - evidence of calcified root-mat horizons in paleosols;
  • surficial laminar calcretes;
  • lichen stromatolites;
  • pedogenic laminar calcretes;
  • capillary rise-zone laminar calcretes;
  • laminar calcretes, occurring in the alluvial Senora de Brezales Formation


Laminar calcretes are described from the Lower Carboniferous of South Wales, the Upper Jurassic of southern England and the Upper Jurassic–Lower Cretaceous of northern Spain. They are interpreted as calcified root-mats (horizontal root systems) and are compared with other examples in the geological record and with possible modern analogues. All three occurrences consist of virtually identical, centimetre to decimetre-thick, locally organic carbon-rich, laminar micrites containing up to 50% by volume of millimetre-sized typically calcite-filled, tubular fenestrae set in an irregular but very finely laminated matrix. It is suggested that root-mat calcretes are probably very common in the geological record in peritidal, lacustrine margin and floodplain deposits, but owing to their crudely biogenic microstructure, they more closely resemble cryptalgal laminites than do other laminar calcretes. The recognition of such root-mat calcretes in sedimentary sequences not only provides evidence of subaerial exposure and vegetation cover but can also indicate positions of palaeo-water-tables in certain circumstances.