GEOMORPHOLOGY AND SURFICIAL GEOLOGY OF THE LAGO ARGENTINO MAP SHEET, SANTA CRUZ PROVINCE, ARGENTINA

The Lago Argentino 1:200,000 map sheet is located on the eastern edge of the Andes in southern Patagonia. Physiographically the map sheet is dominated by Lago Argentino, a 20 x 80 km finger lake. The western third of the map area is dominated by complexly deformed Paleozoic and Mesozoic sedimentary rocks of the eastern Andes. The geomorphology of the area has been shaped by active tectonism, uplift and fluvial erosion. Additionally glacial deposition and erosion, mass wasting and eolian processes have helped to shape the modern landscape.

Glacial events in particular have profoundly influenced the geomorphic evolution of the area. The major glaciation, termed the “Grand Patagonian Glaciation” (GPG) by Rabassa and Coronato (2002) is 1.0 to 1.1 my in age. Older, pre GPG glacial deposits were dated by Mercer (1969) and are bracketed between 2.08 and 1.03 my. Rabassa and Coronato (2002) have identified three mid-Pleistocene events that they term Post GPG 1-3. Lastly two Upper Pleistocene (Wisconsinan) events have been identified with ages between 20,000 and 10,000 years.

Within the map area Pre GPG deposits have elevations of 600-1,000 m above sea level, GPG deposits occur at elevations of 380-400 m. Post GPG 1 deposits occur at 280 m while post-GPG 2 and 3 deposits occur at elevations of about 200 meters. Post-GPG 3 deposits are especially well preserved and continuous along both lateral margins of Lago Argentino. Upper Pleistocene age moraines are well developed near Punta Banderas near the western end of Lago Argentino and enclose the eastern end of Lago Rico to the south.