A speleothem record of climate variability in Southwestern North America during Marine Isotope Stage 3

• Main Author: Peinado, Justin G
• Format: Text
• Language: unknown
• Published: UNM Digital Repository 2018
• Subjects: Climate; Speleothem; Oxygen; Carbon; DO-event; Moisture; Geology; Kya; ice core; NGRIP
• Online Access: https://digitalrepository.unm.edu/eps_etds/237; https://digitalrepository.unm.edu/cgi/viewcontent.cgi?article=1233&context=eps_etds

During Marine Isotope Stage 3 (MIS-3) of the last glacial period, there were rapid transitions between warm and cold climates referred to as Dansgaard-Oeschgerr (DO) events. In Southwestern North America (SWNA), two speleothem paleoclimate records document changes in moisture source delivery in response to DO-events during MIS-3, but do not address potential changes in effective moisture for the region. In this study, we introduce a new high-resolution speleothem paleoclimate record from Carlsbad Cavern in the Guadalupe Mountains. The speleothem, sample BC-5, grew continuously from 46-31 kya during the latter half of MIS-3, based on U-Th dating. We also tied stable isotope (δ18O and δ13C) and trace element (Sr/Ca, Mg/Ca, and Ba/Ca) analysis to the U-series chronology to produce multiple high-resolution time-series. Our data further strengthens the shifting westerly storm-track hypothesis and suggest that DO-events led to changes in effective moisture. The stable isotope time-series displays DO-events and are clearly tied to other speleothem records from SWNA and the NGRIP ice core record. When compared to a Holocene speleothem record (BC-11) and a speleothem Asian Monsoon record, it becomes apparent that δ13C is a record of local changes in effective moisture and vegetation. δ13C also suggests an atmospheric pCO2 control on vegetation and speleothem calcite during the last glacial as has been suggested in other studies. Trace element analysis of BC-5 further supports the stable isotope interpretations. Sr/Ca, Mg/Ca, and Ba/Ca all strongly covary, indicating that they are controlled by similar processes, and are likely connected to changes in effective moisture and local karst processes.