AN ISOTOPIC INVESTIGATION OF A PARTIALLY RECRYSTALLIZED ARAGONITE STALAGMITE FROM CENTRAL NEW YORK

High-precision Uranium-Thorium dating and stable isotope (δ¹⁸O and δ¹³C) analysis of a predominantly aragonite stalagmite from Gage Caverns in Schoharie, New York have been investigated as a local paleoclimate record covering the past ~ 1.25 ka. This speleothem (Gage02) has undergone partial diagenesis from aragonite to calcite, producing observable δ¹⁸O and δ¹³C isotopic differences between the original aragonite versus the altered calcite. U/Th samples taken from the diagenetic calcite also produce anomalous isotope results and U/Th dates when compared to the unaltered aragonite samples, providing evidence of how diagenetic processes can alter the reliability of data collected for speleological climate studies. While data from calcite regions may be suspect, unaltered aragonite regions of the speleothem provides presumably reliable data with clear trends. Aragonite δ¹⁸O and δ¹³C values range between -4.0‰ to -5.0‰ and -9.0‰ to -6.5‰, respectively, showing minor variability in the paleoclimate record of the area. Calcite sections of the speleothem have much lower and variable δ¹³C values (-11.0‰ to -9.0‰), while δ¹⁸O values of the calcite are extremely stable, hovering between -5.2‰ to -5.6‰. Considering both the irregular stable isotope results and drastically different U/Th dates, we believe that diagenetic calcite sections from this sample provide unreliable proxy records and should not be included in climate reconstruction. Data from aragonite sections will be compared with another speleothem record (Gage01) from the same cave system.