Duncan F. Sibley, 1980. "Climatic Control of Dolomitization, Seroe Domi Formation (Pliocene), Bonaire, N.A.", Concepts and Models of Dolomitization, Donald H. Zenger, John B. Dunham, Raymond L. Ethington
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Dolomitization of sediments may be controlled, in part, by their pre-dolomitization diagenetic history. The Seroe Domi Formation (Pliocene) dolomites on Bonaire underwent a period of minor fresh water diagenesis prior to dolomitization. During this initial stage of diagenesis, a small amount of low Mg-calcite cement formed. Unaltered high Mg-calcite and aragonite skeletal fragments were replaced during dolomitization and low Mg-calcite was, at first, inert and later occasionally dissolved. The indusion of calcite cement crystals and crystal molds in dolomite rhombs, the presence of calcite zones in dolomite rhombs, and the preservation of limestone fragments in dolomitized breccias demonstrate that low Mg-calcite was not replaced during the initial dolomitization. Cloudy centers and clear rims formed when the dolomitizing fluid changed from near saturation with respect to calcite (cloudy centers due to inclusions and molds) to undersaturation with respect to calcite (inclusion and mold-free rims).
The concentration of Na+ in these dolomites is approximately 280 ppm and the δ18O values range from +2.0 to +4.1% PDB. These data indicate that the dolomitizing fluid was low in Na+ (relative to seawater), but isotopically heavier than most ground water and, therefore, probably an evaporation concentrated fresh water.
The Seroe Domi Formation is dolomitized on Curaçao and Aruba as well as on Bonaire. The data suggest that dolomitization may be climatically controlled. In humid climates, a sediment in the fresh water-seawater phreatic mixing zone may undergo rapid calcification due to the high PCO2 in the ground water. In arid climates, the water will have a lower PCO2 due to limited soil development resulting in slower calcification and, therefore, increased chances for dolomitization.
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Concepts and Models of Dolomitization
Special Publication 28 has its roots in the 22nd Annual Research Symposium of SEPM entitled Concepts and Models of Dolomitization – Their Intricacies and Significance held on April 3,1979 in Houston, Texas as part of the joint annual meetings of AAPG and SEPM. The purpose of that symposium was to express the state-of-the-art of the study of the elusive process(es) of dolomitization. Most of the contributions in this volume are concerned with apparent early, nearsurface dolomitization, either by hypersaline brines, by the marine-meteoric mixing model or some variant thereof, or by both mechanisms where more than one phase or kind of dolomite exists, or where the origin of a particular dolomite is uncertain. Other models and aspects of dolomitization are treated here as well.