CADIC   02618
CENTRO AUSTRAL DE INVESTIGACIONES CIENTIFICAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
TERRESTRIAL AND LACUSTRINE EVIDENCE OF HOLOCENE GLACIER ACTIVITY IN TIERRA DEL FUEGO (SOUTHERNMOST SOUTH AMERICA)
Autor/es:
MAURER, M.; MENOUNOS, B.; CLAGUE, J.; OSBORN, G.; RABASSA, J. O.; PONCE, J. F.; BUJALESKY, G.; FERNADEZ, M. ; CORONATO, A.
Lugar:
Mar del Plata
Reunión:
Congreso; International Geological Congress on the Southern Hemisphere; 2010
Institución organizadora:
ISTITUTO NAZIONALE DI OCEANOGRAFIA E DI GEOFISICA SPERIMENTALE - OGS, TRIESTE, ITALY; INSTITUTO DE GEOFÍSICA DANIEL A. VALENCIO,
Resumen:
The synchronicity of Holocene glacier fluctuations in the northern and southern hemispheres is a
subject of debate. Our research addresses this issue by examining the lacustrine and terrestrial
evidence of glacier activity in Tierra del Fuego. In April 2009, we performed a bathymetric survey of
glacier-fed Lago Roca (S 54º 48, W 68º 38) and recovered four percussion cores from the lake floor.
The cores are 1-2 m in length and consist of inorganic, rhythmically laminated silt and clay. Laminae
are 1-2 mm thick, silt-clay couplets that appear to be clastic varves. Magnetic susceptibility generally
increases upward to a peak 1.5 m below the top of the longer cores. The uppermost 20 cm of the cored
sediments are the least clastic-rich and have the lowest magnetic susceptibility. Organic content is
inversely related to magnetic susceptibility, with low values near the top and bottom of the cores.
A field study at Stoppani Glacier, 25 km northeast of Lago Roca, in December 2009 provided
evidence of several advances of the glacier during the past 4000 years. The left lateral moraine of the
glacier is composed of multiple tills separated by glaciofluvial and glaciolacustrine sediments.
Radiocarbon ages of stumps in growth position, detrital wood in till units, and vegetation mats
indicate that the glacier repeatedly advanced between 3510 ± 15 and 184 ± 15 14C yr BP (3830150
cal yr BP). The advances broadly coincide with documented intervals of glacier expansion in the
Northern Hemisphere.
Additional work on the Lago Roca sediment record is underway. Those data will supplement the
discontinuous terrestrial record preserved at Stoppani Glacier. The work includes analysis of pollen,
diatom, and phytoliths recovered from the sediment cores. The results will be compared with
palynologic records from Holocene peat bogs, which are abundant on Tierra del Fuego. These new
lake and terrestrial records will help constrain the age and magnitude of past glacier advances in
Patagonia, allowing an assessment of inter-hemispheric synchronicity of climate events during the
Holocene.