The interactions of waters with carbonate rock in Yucatan, Mexico
Gmitro, Daniel Allen
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Northern Yucatan, Mexico, is characterized as a flat, pitted, karst platform. Contained within this platform is an unconfined aquifer. A simple mixing of meteoric and ocean waters occurs within this aquifer and due to density differences a freshwater lens floats above a saline water body from which it is separated by a zone of dispersion (mixing zone). Chemically, this zone of dispersion is characterized by continuous gradients in concentration of chemical species. The aquifer material is composed essentially of pure carbonate rocks. These sedimentary rocks have been diagenetically altered to a microspar fabric that approaches pure cal cite or dolomite. The original textures and structures of the sedimentary rocks are difficult to recognize within the diagenetic fabric and often must be inferred. The solution that diagenetically altered these sedimentary carbonates to calcite was meteoric water; the solution that produced dolomite was a mixture of meteoric and ocean waters, as seen by whole-rock stable isotopic evidence.