MIDDLE TO LATE HOLOCENE CLIMATE TRANSITION IN SOUTHWESTERN NORTH AMERICA FROM STALAGMITE PROXIES, GUADALUPE MOUNTAINS, NEW MEXICO

A definable transition in climate around 4.2 ka is observed in proxy records from many locations around the world but is not well represented by terrestrial proxies from southwestern North America. Recognizing these subtle changes requires long, continuous, highly resolved records, and stalagmites are ideal for this as they host several climate proxies suitable for construction of high-resolution climate records. We report here the results of three U-series dated, multi-proxy speleothem records from two caves (stalagmite PD3 from a forest service cave and stalagmites X2 and X3 from a Carlsbad Caverns National Park cave) in the Guadalupe Mountains of southeastern New Mexico covering a period from 6500-900 yr BP. A total of 21 U-series ages show that stalagmite PD3 grew continuously from 6200 to 2000 yr BP. Stalagmite PD3 δ¹⁸O and δ¹³C time-series exhibits decadal- to centennial-scale variability, but do not demonstrate a distinct difference between Middle and Late Holocene climate. Elemental, δ²³⁴U, and grayscale time-series better define this transition. A distinct shift from higher trace element (Sr, Ba, and Mg) concentrations to lower concentrations in stalagmite PD3 defines the transition at ~4.2 ka and is supported by δ²³⁴U, and grayscale analysis, with the grayscale time-series showing greater variability in the Late Holocene. A high-resolution segment of the Middle and Late Holocene are represented by δ¹⁸O and δ¹³C time-series from stalagmites X2 and X3 that also show a shift from heavier values during the Middle Holocene to lighter values during the Late Holocene. These data suggest a transition from a slightly warmer and drier Middle Holocene to a cooler, wetter, and more variable Late Holocene climate that could be due to an increase in the winter precipitation component, which is demonstrated by comparison with other published data. Spectral and wavelet analyses on high resolution proxy data from stalagmites X2 and X3 further suggest enhanced ENSO/PDO activity during the Late Holocene as possible driving mechanisms for the observed increase in winter moisture.