EP029-0002
GUANACO Afloat: Large-lake Kullenberg Sediment Coring Informing the Dynamics of the Southern Patagonia Ice Sheet
Thursday, 10 December 2020
Poster
Mark Shapley1, Ryan OGrady1, Matias Romero2, Guido Brignone2, Anastasia Fedotova3, Cristina San Martín4, Guillermo Tamburini Beliveau5, Emi Ito6, Maximillian S. Van Wyk de Vries7 and Anders J Noren8, (1)National Lacustrine Core Facility/ CSDCO, Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN, United States, (2)Universidad Nacional de Córdoba, Centro de Investigaciones en Ciencias de la Tierra (CICTERRA-CONICET), Córdoba, Argentina, (3)Southern Methodist University, Dallas, TX, United States, (4)Centro Austral de Investigaciones Científicas (CADIC-CONICET), Ushaia, Argentina, (5)Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), El Calafate, Argentina, (6)University of Minnesota Department of Earth & Environmental Sciences and Limnological Research Center, Minneapolis, MN, United States, (7)University of Minnesota, Department of Earth and Environmental Sciences and Limnological Research Center, Minneapolis, MN, United States, (8)CSDCO, Department of Earth and Environmental Sciences, University of Minnesota, ESCI, Minneapolis, MN, United States
Abstract:
Closing the LIA lithostatic loading mass balance for the Southern Patagonia Ice Sheet required the recovery of high-quality sediment cores representing glaciolacustrine deposition across the very large (1415 km
2), stormy (maximum daily wind speeds frequently >40 km/hr) and bathymetrically complex Lago Argentino (Magnani et al (G004)). Field challenges for this coring campaign included 1) water depths locally exceeding 600 m, 2) operations in close proximity to calving glacier fronts and locally dense iceberg streams, 3) coarse ice-contact sediments near ice margins, and 4) project budget limitations dictating the use of a vessel of opportunity drawn from the limited fleet serving the Lago Argentino tourist industry.
To meet these technical challenges, we adapted the National Lacustrine Core Facility/ Continental Scientific Drilling Coordination Office (LacCore/ CSDCO) Kullenberg piston-coring kit for deployment and deep-water operations aboard the MV Janet, a 28m LOA landing-craft ferry used in support of tourist operations on remote areas of Lago Argentino. A launch and recovery system (LARS) was designed around the geometry of the Janet, allowing for over-the-side deployment and retrieval of the coring apparatus. Janet was refitted for coring within 48 hours of gear arriving on site. Mid-project, the winching system was re-tuned for the deeper-water settings encountered in the western arms of the lake by reducing wire rope diameter, necessitating shorter core lengths.
Using this customized and adaptable platform, 108 m of core were recovered from 45 sites during 16 non-consecutive (due to weather) coring days. Coring sites were identified based on the preceding seismic reflection survey and represent all major Lago Argentino depocenters and depositional environments (Fedotova and Magnani, (G004)). High-quality surface (MUC) and Kullenberg cores were raised from water depths in excess of 600 m, representing facies from annually laminated fine silt and clay with a linear sedimentation rate near 1-2 mm/yr, to coarse, crudely stratified ice-contact debris inferred to date from post-LIA time. Core recovery ranged up to 6.4m at shallow water (<275m) sites and to 5.5m at deep water (>275m) sites, interpreted to represent a maximum of ca. 4000 yrs of dominantly varved deposition (Van Wyk De Vries et al (EP010)).
