SPELEOTHEM STRONTIUM CONCENTRATIONS IN EOGENETIC CARBONATES

The presence of strontium (Sr) in carbonate rocks has long been long documented and recognized as a contributor to the trace element content of speleothems. Sr in speleothems can originate from multiple sources, although the majority of current research assumes the Sr infiltrates from a surface source. In younger, eogenetic carbonates, the mineralogy is often aragonite and the aragonite crystal structure accommodates Sr in replacement of Ca. Over time aragonite will invert to the stable polymorph calcite. This inversion releases Sr to the vadose zone, as the Sr cannot be accommodated in the calcite crystal lattice.

Three questions were asked during this research: 1) does the Sr content of Caribbean speleothems have a direct relationship with the age of the host rock at the time of speleothem precipitation?; 2) do older speleothems contain less Sr than younger speleothems in the same climatic setting?; and 3) will speleothems record the change in Sr concentration of eogenetic carbonates as a faster depletion in climates of higher precipitation as opposed to drier climates?

The speleothems and cave rocks in this study were analyzed with various methods in an attempt to understand the rock processes that affect speleothem Sr concentrations. Evidence to support the hypothesis that younger host rock contributes higher concentrations of Sr to speleothems was found in the stalagmites of Curacao while Bahamian stalagmites indicated climatic variations. The results have implications for using stalagmites from relatively young, eogenetic limestone as a proxy for Sr-related paleoclimate data.