For the first time a course on geocryology in South America: ‘Periglacial Phenomena, Determination and Application’ was held thanks to support of the Foundation ‘Miguel Lillo’ and the National University of Tucumán, NW Argentina. It was a one week postgraduate course, held in the month of June in San Miguel de Tucumán, by Dr. Dario Trombotto and Dr. Ana-Lía Ahumada with participants from different parts of Argentina.

 

Several members of the Argentine Association on Permafrost (AAP) participated in the 31st International Geological Congress 2000 in Rio de Janeiro, Brazil, particularly in the session ‘Modern and Ancient Sedimentary Environments Related to Glaciation’. Dario Trombotto was the convenor of this session, and the idea was to convene a South American meeting of the different experts on cold climate environments. In the two sessions ‘Modern and Ancient Sedimentary Environments Related to Glaciation’, the following South American posters were presented: Periglacial sedimentary structures, Central Andes, Argentina, by A.-L. Ahumada. Periglacial phenomena in the northwest of Argentina, by A.-L. Ahumada. Study of rock glacier ice, by L. Arena & G.M. Caranti. Review of permafrost measurements obtained eastward of the Antarctic Peninsula, by E. Borzotta, J. Venencia & M. Mamani. Freezing index and frequency in Patagonia and in the piedmont cordillera region, by E. Buk.

The permafrost on Seymour Island (Antarctica): temperatures and geophysical soundings, by E. Buk. Preliminary studies of Middle Pleistocene loess in the piedmont of Mendoza, Argentina at 33° S, by D. Trombotto & M. C. Regairaz.

South American Geocryological Inventory, by D. Trombotto. Abstracts from these posters can be found on the Congress CD-ROM. A pre-Congress field trip with the participation of Jerry Brown and Dario Trombotto to the Itatiaia Mountains, Serra da Mantiqueira, reaching almost 2800 m asl., was organised by the South American periglacial group together with Dr. May C. Modenesi-Gauttieri, Geological Institute of São Paulo, Brazil. Several possible periglacial deposits were observed in southeast Brazil. A small working group was created and possible joint projects between Argentina and Brazil were discussed in order to be able to analyse cryogenic indicators in the future. The geocryology of Mendoza was presented to the Argentine Working Group on Quaternary Research (Cadincua - INQUA) at the field workshop in Mendoza in November.

At present Dr. Ana-Lía Ahumada, Institute of Quaternary Geology and Palaeoclimate, is carrying out an inventory of rock glaciers in the northwest of Argentina. Knowing the distribution of cryogenic phenomena in this area may contribute to a better understanding of climate changes. Together with Dr. Lucía Arena, Department of Mathematics, Astronomy and Physics, National University of Córdoba, ice from the rock glacier ‘Morenas Coloradas’ of the ‘Cordón del Plata’ is being analysed, and the correlation of micromechanical characteristics and the natural conditions of ice from a sedimentary environment are studied. E. Borzotta has estimated the heat flow and the geothermal gradient based on magnetotelluric soundings on Seymour and Ross Islands. These data were used in conjunction with MAAT to estimate permafrost thickness under equilibrium condition.

María Camacho, University of Jujuy, is studying the sedimentology of the ‘Laguna de Pozuelos’ in northwest Argentina and has identified two humid stages: the Minchin Phase of 27 ka and Tauca Phase of 12 ka. Bernard Francou (Quito, Ecuador) continues monitoring a rock glacier in the ‘Cerro Caquella’ area, Bolivia. He is working particularly on Andean permafrost degradation caused by climatic changes. At the same time he is preparing a borehole drilling to a large depth at ‘Cerro Illimani’ (Bolivia, 6450 m asl.) and at ‘Cerro Chimborazo’ (Ecuador, 6310 m asl.). Trombotto and Regairaz, Mendoza, continue their studies of the loess profile at Las Carreras Valley at the foot of the ‘Cordón del Plata’, an eastern range of the Andes, at 2200 m asl. in Mendoza. The sedimentary characteristics of the analysed material correspond to an Andean loess. The studies of this loess therefore would be the first Argentine example. The loess was dated using TL technique to be 234 +/- 18 ka old, which assigns it to the Middle Pleistocene and to a period rarely mentioned for South America and the Southern Hemisphere. This profile constitutes a key element for the Quaternary stratigraphy in South America.

The Dr. Ricardo Villalba research group (Masiokas and others) from Department of Dendrochronology and Environmental History, at the Institute IANIGLA (Conicet), Mendoza, is working on the project PATAGON-1000. The study ‘Latitudinal differences in glacier fluctuations across Patagonia: A dendrogeomorphological approach to characterise climate variability in the southern Andes during the past 1000 years’ is conducted in collaboration with the Geocryology Unit (Trombotto) of the same institute. The major goal is to characterise the natural climatic variability in this region, with particular emphasis on long-term variability.

Dario Trombotto. (dtrombot@lab.cricyt.edu.ar)