2009 Portland GSA Annual Meeting (18-21 October 2009)

Paper No. 16
Presentation Time: 9:00 AM-6:00 PM


SAGREDO, Esteban A., Department of Geology, University of Cincinnati, 500 Geology Physics Bldg, Cincinnati, OH 45221-0013, MORENO, Patricio I., Department of Ecological Science, Institute of Ecology and Biodiversity. University of Chile, Las Palmeras 3425. Casilla 653. Ñuñoa, Santiago, 7800024, Chile, KAPLAN, Michael R., LDEO, Columbia University, Palisades, NY 10964 and VILLA-MARTÍNEZ, Rodrigo P., Centro de Estudios del Cuaternario (CEQUA), Avenida Bulnes 01890, Casilla 113-D, Punta Arenas, 6213029, Chile, sagredea@mail.uc.edu

Determining the timing and direction of paleoclimate changes in the southern mid-latitudes is a prerequisite for understanding the mechanisms involved in the generation and propagation of abrupt climate changes at hemispheric and global scales. Of particular interest is the sequence of paleoclimate events through the Last Glacial Termination (=T1), during which occurred an abrupt transition from glacial maximum to interglacial climate, rapid withdrawal of excess continental ice, reorganizations of the coupled ocean-atmosphere system, a sustained deglacial sea level rise, and large increases in atmospheric greenhouse gases. We present a new record from the Última Esperanza region (51°25’-52°25’S), SW Patagonia, to unravel the temporal and spatial structure of glacial fluctuations during T1, in the only windward-facing continental landmass in the Southern Hemisphere that intersects the core of the southern westerly wind belt.

Geomorphic, stratigraphic and geochronological evidence indicate the following stages since the Last Glacial Maximum (LGM): (i) deposition of prominent moraine complexes during two advances dated at ~33 and >17.5 cal kyr BP; (ii) development of an ice-dammed proglacial lake accompanying ice recession; (iii) active deposition of moraine complexes at intermediate positions followed by recession at ≥15.2 cal yr BP; (iv) lake level drop and subsequent stabilization between 15.2-12.8 cal kyr BP; (v) a glacial readvance within the proglacial lake between 14.6-12.8 cal kyr BP; (vi) ice recession, stabilization, and lowering of the proglacial lake level between 12.8-10.3 cal yr BP; and (vii) glacial withdrawal and disappearance of the proglacial lake prior to10.3 cal kyr BP.

By comparing our results with the chronologies from neighboring regions we explore whether there is a consistent temporal/geographic pattern of glacial fluctuations during the LGM and T1, and examine their implications at regional, hemispheric, and global scales.