Abstract

The 87Sr/86Sr ratios and the activity ratios of 234U/238U and 230Th/238U have been measured in dolomites from a 168-m-deep core taken on the island of San Salvador, Bahamas. These data suggest two periods of dolomitization. The first episode dolomitized Miocene age sediments during the latest Miocene, and the second dolomitized the Pliocene portion of the core and was still active as recently as 150 ka. The late timing of the second episode argues against penecontemporaneous models of dolomitization for the Pliocene sediments. Instead, dolomitization is favored either as a result of mixing-zone development during the large Pleistocene sea-level changes or by movement of seawater through the platform.

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