New Mexico Geological Society Annual Spring Meeting — Abstracts

The effort to constrain past climate change depends on the availability of high-resolution records. This is especially true in continents, where datable material is scarce. Annual growth banding has been shown to occur in some speleothems; this, combined with U-Th ages that have an uncertainty of around 25 years (2-sigma) in clean Holocene samples, suggests that speleothems have the potential to provide robust, quantitative climate data. In moisture-limited regions such as the southwestern US, stalagmite growth and growth hiatuses, annual band thickness, and mineralogical, elemental, and isotopic variations in speleothems can be used as a record of regional effective moisture. From stalagmite growth in the Guadalupe Mountains of NM, this region is shown to have experienced greater than present-day moisture beginning ~4 ka, specifically between ~3 ka and 0.8 ka, following a dry middle Holocene. From the annual band thickness of multiple stalagmites, an indicator for growth rate, this region experienced distinct wet and dry events over this time period; for instance wet events (intervals of increased growth rate) are observed at 2.8 and 2.0 ka, and a dry event (hiatus) between 0.7 and 0.45 ka. A wet interval is also observed between 0.46 and 0.17 ka, correlating to the Little Ice Age. Calibration of the speleothem record to the historical climate record is currently in progress, along with analyses of these and other stalagmites for elemental variations. Ultimately this study will constrain specific relationships between physical, mineralogical, elemental and possibly isotopic variations in speleothems and changes in effective precipitation.