Large-Scale Cement Stratigraphy in Cavern Porosity, Mallorca, Spain

Luis Pomar

Rapid precipitation of carbonate cements occurs at the air-water interface in the zone of mixed fresh and marine waters in karstic caverns near the coast of Mallorca, Spain. These cements, which have been precipitating at least since the middle Pleistocene, occur as fibrous calcite, rhombic calcite, and fibrous aragonite, which have accumulated in superimposed bands reaching total thicknesses of a few centimeters to a few meters. Calcite overgrown on aragonite without evidence of aragonite dissolution is common, although in some places the calcite shows later dissolution.

Recent fibrous calcite with rapid rates of growth is precipitated in the few-decimeters-thick zone of tidal fluctuation (atmospheric pressure tides). Carbon-14 dating of these cements gives growth rates of 72.5 mm/1,000 years. Extensive coatings of these cements extend 55 m vertically, from 40 m above to 15 m below the water table. Uranium-thorium and SER dating of some of the coatings shows that the cycles of precipitation recorded in the cements over the last 700,000 years are on the order of 100,000 years (Milankovich cyclicity). Precipitation of these cements occurred in the upper phreatic zone, whose position was tied to sea level changes during the Pleistocene-Holocene. The stratigraphy of these cements therefore provides an excellent record of late Quaternary sea level history n the western Mediterranean.

From the horizontal distribution of facies it is possible to construct the probable sequence of lithofacies, which would characterize carbonates accumulating on a temperate-climate carbonate shelf. Many of these lithofacies are recognized in upper Miocene limestones on the Balearic Islands.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.