Coral Ba/Ca molar ratios as a proxy of precipitation in the northern Yucatan Peninsula, Mexico

摘要

The Yucatan Peninsula consists of a karstic terrain that allows the aquifer to directly recharge from rainfall. Due to the various dissolution/precipitation reactions occurring during groundwater flow, the groundwater discharge in the coastal zone becomes a source of trace elements including Ba. The aim of this study was to use the coralline Ba/Ca record as a proxy of precipitation under the consideration that rainfall rates vary at inter-annual time scales. Annual Ba/Ca ratios, both the total content (Ba/Ca _(TC)) and the Ca-substitutive fraction (Ba/Ca _(CaF)), were quantified in a 52-a old coral colony of Montastraea annularis from the Punta Nizuc Reef, Mexican Caribbean. Average Ba/Ca _(TC) (5.90±0.56μmol/mol) was ~20% higher than Ba/Ca _(CaF) (4.85±0.33μmol/mol) indicating that Ba is also incorporated in other fractions. Correlation between annual precipitation and Ba/Ca _(TC) time-series is significant (r=0.77, p<0.05), allowing the use of the Ba/Ca _(TC) ratio as a proxy of precipitation, and hence, enabling the reconstruction of precipitation patterns through time. Likewise, the Ba/Ca _(CaF) ratio can be used for the reconstruction of dissolved Ba in coastal seawater.