Abstract

Dolomite, a carbonate mineral like calcite, is seen abundantly in the geologic record, but in recent millennia, the abundance of the mineral has decreased significantly. Dolomite formation is relatively scarce in the Holocene; one of the few locations where Holocene dolomitization has been described is Sugarloaf Key, Florida.

We sought to revisit work describing this dolomite and investigate changes in its spatial distribution and mineralogy after ~50 years of environmental and sea level change. We collected ~50 rock and sediment samples across the island and then analyzed them with X-ray diffraction to quantify the content of calcite and aragonite (CaCO3) vs. the content of dolomite (CaMg(CO3)2), which will determine each sample’s position on the dolomite to calcite spectrum. These range from 100% calcite to VHMC, or very high magnesium calcite, followed by poorly ordered dolomite, and finally stoichiometric dolomite, or perfectly ordered dolomite.

We will present these data along with water stable isotope measurements of waters from the site, which allow us to characterize the geochemistry of the environment. In the future we also intend to measure dolomite stable isotopes to estimate the temperature of the ocean at the time that the dolomite was formed.