Evidence for Pleistocene periglaciation in the lowlands of central Argentina (36–39°S)

Abstract

AbstractPleistocene permafrost has been recognized in the lowlands of extra-Andean Argentina from Tierra del Fuego to the Rio Negro valley at 40°S, and to the Sierras Australes at 38°S. Features that could have formed only by cryogenic activity at elevations between 230–400 m above sea level in surficial deposits and in the bedrock beneath are described here as far north as 36°S. These features are not as pronounced as they are farther south because most of central Argentina was a cold desert during the glacial episodes, and therefore little ice formed. Calcareous dust, formerly considered as pedogenic and now known to be glaciogenic, is closely associated with these features. Secondary precipitates, such as lamellar crystals of calcite and gypsum, and other microscopic features like those observed in perpetually frozen ground also confirm that this region experienced permafrost at some time. These new findings mean that the area affected by periglaciation is much larger than previously thought and expanded more than 200 km farther to the north. Stratigraphic evidence and geomorphological features place both deposits and cryogenic features within them as early–middle Pleistocene age.