Petrographic and Geochemical Analysis of Caliche Profiles in a Bahamian Pleistocene Dune
- V. Paul Wright2 and
- Maurice E. Tucker3
Published Online: 8 APR 2009
Copyright © 1991 The International Association of Sedimentologists
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
Postgraduate Research Institute of Sedimentology (PRIS), University of Reading, UK
Department of Geological Sciences, University of Durham, UK
- Published Online: 8 APR 2009
- Published Print: 13 JUN 1991
Print ISBN: 9780632031870
Online ISBN: 9781444304497
- 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
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.