Late Cenozoic Dolomites of the Bahamas: Metastable Analogues for the Genesis of Ancient Platform Dolomites

  1. Bruce Purser,
  2. Maurice Tucker and
  3. Donald Zenger
  1. V. C. Vahrenkamp1 and
  2. P. K. Swart2

Published Online: 14 APR 2009

DOI: 10.1002/9781444304077.ch9

Dolomites: A Volume in Honour of Dolomieu

Dolomites: A Volume in Honour of Dolomieu

How to Cite

Vahrenkamp, V. C. and Swart, P. K. (1994) Late Cenozoic Dolomites of the Bahamas: Metastable Analogues for the Genesis of Ancient Platform Dolomites, in Dolomites: A Volume in Honour of Dolomieu (eds B. Purser, M. Tucker and D. Zenger), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304077.ch9

Author Information

  1. 1

    Shell Research, Volmerlaan 6, 2288 GD Rijswijk ZH, Netherlands

  2. 2

    Marine Geology and Geophysics, RSMAS, University of Miami, Rickenbacker Cswy, Miami, Florida 33149, USA

Publication History

  1. Published Online: 14 APR 2009
  2. Published Print: 25 MAY 1994

ISBN Information

Print ISBN: 9780632037872

Online ISBN: 9781444304077

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Keywords:

  • Late Cenozoic dolomites of Bahamas - metastable analogues for genesis of ancient platform dolomites;
  • shallow-burial Late Cenozoic dolomites from Little Bahamas Bank (LBB), northern Bahamas;
  • metastable dolomites, Bahamas;
  • lithological and geochemical characteristics of LBB dolomites;
  • middle Miocene to Pliocene section of LBB - predominantly skeletal, carbonate platform sediments;
  • mixing zone-induced seawater circulation;
  • possible future diagenesis

Summary

The petrographic and geochemical characteristics of a more than 80 m thick sequence of shallow-burial Late Cenozoic dolomites from Little Bahamas Bank (LBB), northern Bahamas, indicate that these dolomites are seawater-derived and partially metastable. Dolomites range in composition between calcian and stoichiometric (Ca.60Mg.40 CO3–Ca.51Mg.49CO3). Strontium content and oxygen isotopes covary with the major element composition. It is suggested that part of the 2‰ spread in oxygen isotopic composition is a result of natural and laboratory isotope fractionation. After correction for these effects oxygen isotopes are in equilibrium with seawater at 20–22°C. Iron and manganese content of the dolomites is essentially precursor-controlled. The geometry of one of the dolomite bodies suggests that dolomitization occurred in the seawater phreatic zone. Seawater circulation through LBB was probably driven by an overlying freshwater/mixing zone system during (partial?) platform exposure.

Maturation of the metastable dolomites from LBB during future diagenesis may cause evolution of petrographic and geochemical signatures to those typical of many ancient dolomite sequences. Hence, Late Cenozoic dolomites of the Bahamas can be used as analogues for the genesis of many ancient platform dolomites. Their diagenetic potential permits the prediction of secondary diagenesis and the understanding of its impact seen in older platform dolomites.