HOLOCENE DENUDATION IN A SOUTHERN PATAGONIA TIDEWATER GLACIER SYSTEM; RESPONSE TO CLIMATE VARIABILITY, MARINELLI FJORD, CHILE

This research is a part of a large international study of glacial erosion and continental denudation in six tidewater glaciers across a latitudinal transect from central Chile (40°S) to the Antarctic Peninsula (70°S). The current climatic and basal thermal regimes vary considerably from the northern most fjord in Chile being temperate and the southern most fjord in the Antarctic Peninsula being polar. The objective is to relate continental denudation to climate by examining sediment flux of tidewater glaciers. Marinelli Fjord, located at 54°20′S, 69°35′W, is fed from the Cordillera Darwin Icefield, via the Marinelli and Ainsworth Glaciers. It is the most southern of the Patagonian fjords being studied. This fjord is currently in a temperate climatic regime, but may represent a more transitional system between temperate and sub-polar during the Last Glacial Maximum.

Data collected in Marinelli Fjord during NBP0505 includes a dense grid of CHIRP sub-bottom profiles and nine single channel seismic profiles, along with 15 kasten cores and 15 jumbo piston cores throughout the fjord. Lithostratigraphy, high-resolution seismic stratigraphy and radiocarbon stratigraphy are being integrated to relate climate variability to erosion and sediment flux. Preliminary data shows three main lithofacies - till, ice proximal glaciomarine, and ice distal glaciomarine, and 4 seismic units. Two outer basin cores provide a relatively continuous record for Holocene climate change, going back to 13,150 ybp. These cores yield an average linear sedimentation rate of 0.065cm/yr. Inner basin cores yield radiocarbon dates younger than 315 ybp, with a linear sedimentation rate of 2.60cm/yr. Integration of sedimentation rates and high resolution seismic stratigraphy in Marinelli Fjord indicate that this is a nearly closed system, efficiently trapping the high volume of sediments that are being shed from the continent.