Late Pleistocene-Holocene glacier fluctuations in the Las Leñas and Salado valleys (35ºS), Argentina

ESPIZUA, L. E.; ADAMIEC, G; PITTE, P.; FERRI HIDALGO, L

Valdivia, Chile

Conferencia; Ice and Climate Change: A view from the south; 2010

CECS

The late Pleistocene and Holocene record in this part of the Andes is mostly unknown, so this research is an important step towards obtaining paleoclimatic information of climate changes in South America. In the Central Andes of Argentina between 33º-35º S, paleoclimatic records with reliable chronologies are scarce. Some radiocarbon-dated glacial deposits (minimum ages), morphological and stratigraphical studies, permit the reconstruction of glacier fluctuations during the middle Holocene and late Pleistocene in the Las Leñas and Salado valleys located at 35ºS. A well defined lateral-terminal moraine indicates a glacial activity that probably occurred during the last glacial maximum. This moraine delimits an independent ice stream that flowed about  7, 7 km down Las Leñas valley to 2193 m asl reaching the junction of the Rio Salado. Rhytmically-laminated lacustrine sediments are exposed immediately up-valley from Las Leñas terminal moraine in the Salado valley. These sediments have been sampled in two profiles and dated by radiocarbon and OSL methods as 12.3 ka BP and 8.4 ka BP, respectively. A lateral moraine not well defined could be related with a re-advance or a stand-still that occurred at c. 14.0 or between 11.0 - 10.0 ka BP. The oldest recognized Holocene glacial advance deposited the outermost Eros moraine in Las Leñas valley probably at c. 4.0 - 5.0 ka BP. The second glacial advance is indicated by the Neptuno moraine which reached its maxima at c. 2.2 ka BP. The late-Pleistocene and Holocene moraine sequence is compared with those studied previously in the neighbouring Río Grande basin.