A quantitative midge-based reconstruction of mean July air temperature from a high-elevation site in central Colorado, USA, for MIS 6 and 5

作者：Haskett Danielle R^*; Porinchu David F

来源：Quaternary Research, 2014, 82(3): 580-591.

DOI：10.1016/j.yqres.2014.05.002

• Chironomids
• Midges
• Temperature reconstruction
• Paleoclimate
• Sangamon MIS 5
• Colorado Rockies
• Ziegler Reservoir fossil site
• Paleolimnology

Sediments recovered from the Ziegler Reservoir fossil site (ZRFS) in Snowmass Village, Colorado (USA) were analyzed for subfossil chironomids (or midges). The midge stratigraphy spans similar to 140-77 ka, which includes the end of Marine Oxygen Isotope Stage (MIS) 6 and all of MIS 5. Notable shifts in midge assemblages occurred during two discrete intervals: the transition from MIS 6 to MIS 5e and midway through MIS 5a. A regional calibration set, incorporating lakes from the Colorado Rockies, Sierra Nevada, and Uinta Mountains, was used to develop a midge-based mean July air temperature (MJAT) inference model (r(jack)(2) = 0.61, RMSEP = 0.97 degrees C). Model results indicate that the transition from MIS 6 to MIS 5e at the ZRFS was characterized by an increase in MJAT from similar to 9.0 to 10.5 degrees C. The results also indicate that temperatures gradually increased through MIS 5 before reaching a maximum of 13.3 degrees C during MIS 5a. This study represents the first set of quantitative, midge-based MJAT estimates in the continental U.S. that spans the entirety of MIS 5. Overall, our results suggest that conditions in the Colorado Rockies throughout MIS 5 were cooler than today, as the upper limit of the reconstructed temperatures is similar to 2 degrees C below modem July air temperatures.

• 出版日期2014-11