Paper No. 1
Presentation Time: 08:30
KEYNOTE: MAKING SENSE OF THE LAST DEGLACIATION BETWEEN CLIMATOLOGICALLY DIVERSE REGIONS: A VIEW FROM LAKE ELSINORE IN THE COASTAL SOUTHWEST UNITED STATES TO THE INTERIOR SOUTHWEST UNITED STATES AND NORTHERN MEXICO
Lake Elsinore is the largest natural lake in the coastal southwest United States. Building on cores taken in 2003, a new 20-meter core (LEDC10-1) spanning 9ka to 30ka was acquired in 2010. Twenty-one AMS 14C dates, mostly on discrete organic material (e.g. seeds, charcoal), provide an initial age model between 9 and 25ka. On average 1 cm equals 13 years of sedimentation making this new core the highest resolution, most complete glacial-age terrestrial archive yet obtained from the region. We present initial multi-proxy results including magnetic susceptibility, organic and carbonate content, grain size, CN ratios, and δD plant leaf waxes to infer past climate state and change. The deglacial sequence (18-9ka) is characterized by large amplitude hydrologic change: from a very wet full glacial to a dry Holocene. A deglacial δD change of 70 per mil indicates a dramatic shift in either P:E ratio or changes in storm tracks/moisture sources. Percent sand is highest from 18ka to 15ka indicating wetter-than-modern glacial conditions. Abrupt decreases in sand content at 15ka and then again at 12.8ka suggest a two-tiered deglaciation sequence in the coastal southwest United States. Superimposed on the latter changes is high amplitude sand variability at centennial-to-millennial scales indicating a highly dynamic deglacial climate. Comparisons of the Elsinore deglaciation sequence to high latitude records show coherence with various well-documented climate features such as the Bølling-Allerød and the Younger Dryas. For this presentation, we will also compare the Elsinore record to that from the American southwest (e.g., Cave of Bells and Fort Stanton speleothems) and northern Mexico (e.g., Babicora Basin) with the objective to deconvolve changing climate regimes and moisture sources during the last deglaciation.