Date of this Version
Published in Palaeogeography, Palaeoclimatology, Palaeoecology 422 (2015), pp. 46–56
A high-resolution record of pollen, charcoal, diatom, and lithologic data from Dailey Lake in south-western Montana describes postglacial terrestrial and limnologic development from ice retreat ca. 16,000 cal yr BP through the early Holocene. Following deglaciation, the landscape surrounding Dailey Lake was sparsely vegetated, and erosional input into the lake was high. As summer insolation increased and ice recessional processes subsided, Picea parkland developed and diatoms established in the lake at 13,300 cal yr BP. Closed subalpine forests of Picea, Abies, and Pinus established at 12,300 cal yr BP followed by the development of open Pinus and Pseudotsuga forests at 10,200 cal yr BP. Increased planktic diatom abundance indicates a step-like warming at 13,100 cal yr BP, and alternations between planktic and tychoplankic taxa suggest changes in lake thermal structure between 12,400 and 11,400 cal yr BP. An increasingly open forest, in combination with increased benthic diatoms, indicates warm dry summers during the early Holocene after 11,400 cal yr BP, in contrast to nearby records in northern Yellowstone that register prolonged summer-wet conditions until ca. 8000 cal yr BP. Because of its low elevation, Dailey Lake was apparently sensitive to the direct effects of increased summer insolation on temperature and effective moisture, registering dry summers. In contrast, higher elevations in northern Yellowstone responded to the indirect effects of an amplified seasonal insolation cycle on atmospheric circulation, including elevated winter snowpack and/or in-creased summer convective storms as a result of enhanced monsoonal circulation.