GSA Annual Meeting in Indianapolis, Indiana, USA - 2018

Paper No. 182-4
Presentation Time: 9:00 AM-6:30 PM


KATZ, Sarah A.1, GILLIKIN, David P.2, RODBELL, Donald T.2 and CHENG, Hai3, (1)Earth and Environmental Sciences, University of Michigan, 1100 North University Avenue, Ann Arbor, MI 48109-1005, Ann Arbor, MI 48109-1005, (2)Geology Department, Union College, Schenectady, NY 12308, (3)Institute of Global Environmental Change, Xi’an Jiaotong University, Xi'an, 710075, China

Stable isotope analysis of a central New York speleothem provides a unique opportunity to study terrestrial climate and local hydrology in the northeast US. The U/Th-dated 7.9 ka speleothem records stable carbon (δ13C) and oxygen (δ18O) isotope variability at a precisely dated, sub-centennial resolution over the mid- to late-Holocene. This study investigates short duration, regional climate events recorded by high resolution δ13C and δ18O values in speleothem Gage1, potentially providing an enhanced understanding of rapid hydroclimate shifts, which may be muted or absent in lower resolution terrestrial proxy records (i.e., lake sediment records). As an in situ dripwater study was not possible, the speleothem record was compared to historical and proxy records to constrain some of the variables which control the stable isotope signatures preserved in carbonates. δ13C trends, interpreted as an indication of epikarst vegetation type and density, are largely in agreement with local pollen and archaeological records. Interpretations of the oxygen record are decidedly more complicated by nature; oxygen variations in speleothem carbonates are controlled by the net effect of a variety of factors primarily including temperature, effective precipitation, precipitation seasonality, and moisture source, among other controls. Parsing out the respective impacts of these controls in any given speleothem is challenging, especially in the mid-latitudes where stable isotope signatures of these different factors may be overprinted and vary on differing time frames. The δ18O record in Gage1 is particularly interesting as δ18O values seem to be out of phase with accepted regional temperature during the late Holocene over short-duration events such as the Little Ice Age, Medieval Climate Anomaly, and Dark Ages Cold Period. This suggests, that over the late Holocene, dynamic changes in climate were occurring in additional to temperature which masked the temperature signal. A lack of extreme aridity or wet/dry seasonality reported in other regional climatic studies suggests that moisture source may be the dominant control on the observed δ18O record in Gage1. Continued work seeks to refine our understanding of Holocene atmospheric variability and air mass patterns in central New York, as well as timing of these events.