A quantitative midge-based reconstruction of thermal conditions in central Colorado during marine isotope stage 5

Subfossil chironomid analysis was used to establish the efficacy of adding chironomid assemblages from Colorado to the Great Basin (GB) midge calibration set. The most robust inference model was developed using a 2-component weighted averaging-partial least squares and the calibration set was incorporated into the GB training set. It was used to develop a midge-based mean July air temperature (MJAT) inference model with a robust jack-knifed r2 (0.61) and root mean square error of prediction (0.97C). This inference model was applied to a midge stratigraphy and enabled the development of a quantitative reconstruction of MJAT from ~70 140 ka for the Ziegler Reservoir fossil site near Snowmass Village, Colorado. Reconstructed temperatures ranged from 8.9 13.2C. The transition from MIS 6 to MIS 5e was characterized by an increase in the MJAT of ~1.5C (9.0-10.5C). MIS 5 exhibited increasing midge-inferred MJAT, culminating in a MJAT of 13.2C during MIS 5a.