OXYGEN ISOTOPIC ANALYSES OF HOLOCENE METEORIC PHREATIC SIDERITES & CALIBRATION OF A PALEOCLIMATE PROXY

Theoretical calculations of the latitudinal d¹⁸O variations of modern meteoric phreatic siderites (shown in Ludvigson et al, 1998, Geology, 26:1039-1042) are based on IAEA/WMO data in Rozanski et al.(1993, AGU Monog. 78:1-36), and have yet to be empirically tested. Donated Holocene samples from Louisiana (32°N; Aslan, A., and Autin, W.J., 1999, Jour. Sed.Research, Part B, 69:800-815), Korea (37°N; Choi, K.S., 2000, Marine Geology, 167:231-241), Belgium (51°N; Stoops, G., 1983, Geoderma, 30:179-186) and Finland (64°N; Virtanen, K., 1994, Geological Survey of Finland Bulletin 375) have been collected for this purpose. Reliable data from Louisiana (d¹⁸O ranging from –7.3 to –5.5‰ VPDB) and Korea (d¹⁸O ranging from –5.6 to 1.3‰ VPDB) are already in hand, but results from the Belgian and Finnish localities have been problematic owing to the high labile organic content in the hosting histosols. Optimal procedures for these problematic samples are still under development. When all four locations have yielded reliable d¹⁸O values, a Holocene latitudinal d¹⁸O gradient will be synthesized and compared with the theoretical gradient.