Movement of Subsurface Waters Under the Sabkha, Abu Dhabi, UAE, and its Relation to Evaporative Dolomite Genesis *
Judith Ann McKenzie, Kenneth J. Hsü, Jean F. Schneider, 1980. "Movement of Subsurface Waters Under the Sabkha, Abu Dhabi, UAE, and its Relation to Evaporative Dolomite Genesis ", Concepts and Models of Dolomitization, Donald H. Zenger, John B. Dunham, Raymond L. Ethington
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The hydrology and geochemistry of subsurface waters from a Holocene area of dolomitization, the coastal sabkhas of Abu Dhabi, have been investigated. The origins of the waters (lagoon, open marine, continental and mixed) were defined by their K: Br ratios and stable isotope values. Downward movement of Hood recharge waters was established by decreasing tritium contents with depth under the sabkha. Further, evaporation from the capillary zone imprinted a distinctive δD ratio upon waters from the intermediate sabkha. Measurements established the hydrologie framework under the sabkha. Two aquicludes separate the near surface sediments from the underlying aquifers. The presence of these aquicludes enabled us to measure vertical hydrauuc gradients. The gradient is locally directed downward for a short time after supratidal flooding, but for the most part is directed upward, especially in the area of Holocene dolomitization. Together, the data were synthesized into a hydrologie model for the intermediate sabkha, the area where dolomitization occurs. A single hydrologie cycle was defmed by three sequential stages; flood recharge, capillary evaporation and “evaporative pumping.” The processes involved in the evolution of a dolomitizing solution and the driving forces required to move the solutions through the sediments being dolomitized are inherent in the model.
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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.