The effect of strontium on the aragonite-calcite ratios of Pleistocene corals [Florida

Abstract

ABSTRACT The Pleistocene coral reefs which form the upper Florida Keys are in a state of alteration from aragonite to calcite. A quantitative relationship between the strontium content of the corals and their aragonite-calcite ratios was found. Strontium and calcium determination were made with a Zeiss flame photometer. Aragonite-calcite ratios were determined qualitatively with Meigen stains and quantitatively using X-ray techniques. Where the stains showed that aragonite was high relative to calcite, the strontium content was correspondingly high. Where the stains indicated that calcite was dominant, the strontium content was low. X-ray analyses confirmed these results. In several cases it was noted that within a single sample there were distinct areas which were aragonite and others which w re calcite. These sections were separated and analyzed. In all such cases the aragonite portion of a sample contained about twice as much strontium as did the calcite portion of the same sample. It is suggested that strontium content is a factor which inhibits the alteration of aragonite to calcite under natural geologic conditions, and only when much of the strontium is removed may the alteration take place.