This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
This grant supports a collaborative project between the University of New Mexico, Northern Arizona University and the University of Minnesota, Duluth which will conduct detailed analyses of a unique 82-m long lacustrine sediment core (VC-3) from the Valles Caldera, in northern New Mexico. This core represents a critical time interval in the past that is similar to the modern. As such, an understanding of climatic changes observed in the core will lead to the most detailed assessment of expected future climate variability in the southwest ever recorded.
Intellectual Merit: In May 2004, the GLAD5 drilling project recovered an 82-m deep lacustrine sediment core from the Valles Caldera, New Mexico. Ar-Ar age estimates from a tephra near the base of the core (552±3 ka), two distinct glacial terminations (VI and V) in multiple proxies, and the identification of a two geomagnetic polarity "events", correlated to globally recognized events (14a; and 11a) constrain these lake sediments to the middle Pleistocene (MIS 14 to MIS 10). Initial work by this group shows an intriguing relationship between temperature and hydroclimate during the two long interglacials present in the core (MIS 11 and MIS 13). Peak interglacial temperatures (MBT proxy, pollen) correlate well with extended dry periods in the core (mudcrack intervals). This is consistent with recent predictions of extended drought in SW North America in response to global warming by a marked reduction in winter precipitation. To better understand this critical relationship, the team will conduct more detailed sampling of the VC-3 core at intervals of ~10 cm or less to analyze for temperature (MBT proxy, pollen), lake productivity (organic carbon, Si/Ti ratios, biogenic silica), hydroclimate (del-18O of diatom silica, core sedimentologic characteristics, and pollen and charcoal). Specifically, they will test the hypothesis that during long interglacials, warming leads to extended dry climates with reduced winter frontal precipitation. Additional analyses to be conducted include remanence and rock magnetic properties, major and minor element geochemistry, XRD, XRF scanner analyses, carbon and nitrogen stable isotopes and C/N ratios, and plant macrofossils, all of which will aid in refining paleoclimate proxies. In conjunction with this work, LANL collaborators will conduct compound specific del-D analyses and obtain U‐series dates to improve the chronology at no cost to NSF. Results from this work will shed light on two important paleoclimate questions: the relationship between peak interglacial temperatures and extended dry conditions, and the nature of orbital- to millennial-scale climate change during the middle Pleistocene.
Broader Impacts: This study will further our understanding about the nature of climate change in southwestern North America and its impact on montane ecosystems. This project involves collaborations between four research institutions, UNM, NAU, UMD, and Los Alamos National Lab. Both graduate students and faculty will benefit from interactions with the other institutions and the different expertise that collaborators at each institution bring to bear on the project. The results of this study will be available to the general public using displays and outreach programs through the newly created Valles Caldera National Preserve. This information will include not only the timing of lakes forming in the Valles Caldera and the paleoclimatic records derived from them, but also information about the materials preserved at depth in the Valles Caldera and the nature of the interactions between volcanic processes in the caldera and surficial processes. The project will involve education and training of several graduate students at UNM, NAU and UMD. UNM graduate students include a female Hispanic pursuing a PhD and another female graduate student. The results of this study will be integrated into several courses offered at the participating institutions.
