Last glacial and Holocene stable isotope record of fossil dripwater from subtropical Brazil based on analysis of fluid inclusions in stalagmites

TitleLast glacial and Holocene stable isotope record of fossil dripwater from subtropical Brazil based on analysis of fluid inclusions in stalagmites
Publication TypeJournal Article
Year of Publication2017
AuthorsMillo C, Strikis NM, Vonhof HB, Deininger M, da Cruz, Jr FW, Wang X, Cheng H, R Edwards L
JournalChemical Geology
Volume468
Pagination84-96
Date Published09/2017
Abstract

The stable isotope composition of fossil dripwater preserved in stalagmites fluid inclusions is a promising tool to reconstruct paleopluviosity in the tropics and subtropics. Here we present delta D and delta O-18 records of fossil drip water from two stalagmites collected in Botuvera Cave (subtropical Brazil), covering the last glacial period and the Holocene. The observed millennial-scale variability of fossil dripwater delta D and delta O-18 values is of the order of 10 to 20 parts per thousand and 1 to 3.5 parts per thousand (V-SMOW), respectively. Fluid inclusion delta D and delta O-18 values are higher than the weighted mean delta D and delta O-18 values of modern precipitation, suggesting a possible intensification of extratropical cold surges during both the last glacial period and the Early Holocene, followed by a progressive Late Holocene transition towards modern pluviosity conditions. Fluid inclusions delta O-18 values vary in parallel with stalagmite delta O-18 values during the Holocene but not during the last glacial period. This suggests that the delta O-18 value of precipitation may not be the only dominant factor controlling the delta O-18 values of the analyzed stalagmites. Isotope disequilibrium effects arising from Prior Calcite Precipitation (PCP) possibly affected stalagmites 8180 values to a greater extent than previously considered, though this effect does not bias non-quantitative paleopluviosity reconstructions based on stalagmite delta O-18 values. Isotope-based paleotemperature calculated for the Late Holocene matches modern cave temperature (19 degrees C) within +/- 2.4 degrees C. This encourages further application of isotope analyses of fluid inclusion for climatic reconstructions.

DOI10.1016/j.chemgeo.2017.08.018