Petrographic and Geochemical Analysis of Caliche Profiles in a Bahamian Pleistocene Dune

  1. V. Paul Wright2 and
  2. Maurice E. Tucker3
  1. J. A. Beier

Published Online: 8 APR 2009

DOI: 10.1002/9781444304497.ch10

Calcretes

Calcretes

How to Cite

Beier, J. A. (1991) Petrographic and Geochemical Analysis of Caliche Profiles in a Bahamian Pleistocene Dune, in Calcretes (eds V. P. Wright and M. E. Tucker), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304497.ch10

Editor Information

  1. 2

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

  2. 3

    Department of Geological Sciences, University of Durham, UK

Author Information

  1. Biogeochemical Laboratories, Department of Geology, Indiana University, Bloomington, Indiana 47405, USA

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:

  • petrographic and geochemical analysis of caliche profiles in Bahamian Pleistocene dune;
  • coated grains and pisolites, common in caliche profiles;
  • abundance of filaments and needle-like crystals, indicating formation of caliche pisolites;
  • samples from Bluff, revealing geochemical changes in aeolianite;
  • magnitude of geochemical alteration of host rock, function of caliche profile maturity

Summary

Two caliche profiles from a Pleistocene carbonate dune on San Salvador Island, Bahamas, were examined by petrographic and geochemical analysis. Profile A is an immature buried caliche profile characterized by caliche pisolites, a friable crust and abundant Cerion. Profile B is a more well-developed caliche profile at the top of the dune which contains abundant pisolites, rhizomorphs, laminated calcrete, a breccia and abundant Cerion.

Geochemical changes in caliche profiles relative to the host rock are an increase in Al2O3, Fe2O3 and total organic carbon, a decrease in Mg and Sr, and a decrease in δ13Ccarb, δ18Ocarb and δ13Corg. The magnitude of these changes is probably a function of the duration of subaerial exposure and resultant colonization by dune plants and associated microflora.

Abundance of calcified filaments and needle-fibre crystals in profile A attests to the importance of microbial processes in the early development of caliche profiles. Biogenic structures are largely destroyed in profile B due to recrystallization, but indirect evidence of biological activity is retained in the form of carbon isotope values.