Use of strontium isotopes to constrain the timing and mode of dolomitization of Upper Cenozoic sediments in a core from San Salvador, Bahamas.

The ⁸⁷ Sr/ ⁸⁶ Sr ratios and the activity ratios of ²³⁴ U/ ²³⁸ U and ²³⁰ Th/ ²³⁸ U have been measured on dolomites from a 168 m deep core taken on the island of San Salvador, Bahamas. These data suggest 2 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 favoured either as a result of mixing-zone development during the large Pleistocene sea-level changes or by movement of seawater through the platform.-Authors