Examination of a possible environment of dolomite formation in the mixing zone, Yucatan, Mexico
Dolomite has been found in two flooded cave systems (cenotes) near Merida in the Yucatan Peninsula, Mexico. This dolomite occurs at or near to the fresh- and marine-water mixing zones of both cenotes. Petrographic analysis shows that at least some of the dolomite in each cave system was most probably formed by mixing-zone dolomitization. This dolomite must have formed following submergence of the cave systems, which, based upon radio-carbon dating of ash from a fire pit, could have occurred no earlier than 8250 ± 80 yr BP. Thermodynamic modeling, based on analyses of water samples from the cenotes, indicates that dolomite precipitation is probably favored in one or both cenotes, depending on the extent of ordering in the samples compared to that modeled. Chemical interactions; changes in the level of the interface; and influxes of meteoric water, occurring within one or both cave systems, may be creating conditions that would kinetically favor the precipitation of dolomite.