Date of this Version
QUATERNARY OF SOUTH AMERICA AND ANTARCTIC PENINSULA, v. 6. Ed. Jorge Rabassa (ROTTERDAM /BROOKFIELD: A.A.BALKEMA, 1990), pp. 9-31
Both the sediments and the geomorphic setting of the diamictons along Rio Blanco on the piedmont east of the Cordon del Plata indicate that they could not have been deposited there by a glacier tongue, as I and several earlier observers have suggesred Rather, they must have been deposits of long-runout debris flows, as argued by Polanski. Below 2600m, which is the altitude of the most extensive moraines of the last major glaciation, a late Pleistocene debris-flow fan fills the valley. From 2,200 m to the mountain front the narrow, V-shaped valley could not have been scoured by glacial ice. The debris flows that deposited these piedmont diamictons incorporated glacially transported clasts, so some of the flows recognized along the Rio Blanco trench may have taken place when glacier ice lay in the cirques and upper valleys. Others, however, probably are unrelated to glacial events.