Average Pleistocene Climatic Patterns in the Southern Central Andes: Controls on Mountain Glaciation and Paleoclimate Implications

Abstract

Despite elevations of 5000-6800 m, modern glaciers occur along the southern Puna Plateau and the northern Sierras Pampeanas in the southern central Andes. The modern snowline rises from 5100 m in Sierra Aconquija to 5800 m in the Puna as a result of a westward decrease in precipitation from 450 to less than 100 mm/yr. During the Pleistocene these arid highlands experienced multiple cirque and valley glaciation that likely postdate the last interglacial period, although lack of age control prevents an absolute chronology. Glaciation in the Puna and along the eastern Puna edge produced a 300-m Pleistocene snowline (PSL) depression, while in the Sierras Pampeanas the PSL depression was at least 900 m. The greater PSL depression in the Sierras Pampeanas is best explained by a combination of cooling and increase of easterly moisture, whereas the PSL depression in the Puna appears more sensitive to moisture increases than temperature. Previously, glaciations in this region have been explained by increased precipitation, with a westward depression of the snowline caused by a northward shift of the Pacific anticyclone and equatorward shift of the westerlies. However, these PSL results require an increase of moisture from the east rather than from the west. Further, analysis of topographic data indicates that drainage-basin relief decreases north of 28ЊS. The regional landscape response suggests that the circulation patterns currently observed have persisted at least during the Pleistocene and perhaps during the past several million years.

Late Pleistocene Climate Change and Erosion in the Santa Maria Basin, NW Argentina

“…1). Compared to the present, this interval was characterized by increased humidity (Fox and Strecker 1991;van der Hammen and Absy 1994;Wirrmann and Mourguiart 1995;Ledru et al 1996;Godfrey et al 1997;Turcq et al 1997;Haselton et al 2002) and a stronger ENSO influence Beaufort et al 2001;Tudhope et al 2001) (Fig. 1).…”

A geomorphological map of the Quebrada de Purmamarca, Jujuy, NW Argentina

“…This geological setting accounts for a steep relief, a large complexity of geomorphic forms and processes within a relatively limited spatial range and active tectonic processes. In addition, NW Argentina is situated at the transition between Research on Cenozoic landscape history and the reconstruction of past surface environments in NW Argentina has included studies on longer-term landscape evolution with a focus on climatic and tectonic interactions (Alonso et al, 2006;Strecker et al, 2007) and the investigation of Late Quaternary environmental changes as seen in various geomorphological archives (Alcalde and Kulemeyer, 1999;Zipprich et al, 1999;Trauth et al, 2000;Bookhagen et al, 2001;Tchilinguiriani and Pereyra, 2001;Haselton et al, 2002;Kull et al, 2003;Trauth et al, 2003;Hermanns et al, 2004;Kull et al, 2008). Some efforts have recently been made to achieve improved age control of the >100 m high depositional terrace levels observed along the larger intramontane valleys (Robinson et al, 2005;Spencer and Robinson, 2008).…”

Tectonics, Climate, and Landscape Evolution of the Southern Central Andes: the Argentine Puna Plateau and Adjacent Regions between 22 and 30°S

“…Quaternary lake-level changes, pollen data, and snowline changes document significant shifts in temperature and precipitation (e.g., Ammann et al 2001;Haselton et al 2002;Seltzer et al 2003;Placzek et al 2006). The general agreement between the timing of more humid conditions and periods of maximum summer insolation on the Puna-Altiplano Plateau supports a first-order orbital control of the intensity of the South American summer monsoon (Baker et al 2001).…”

“…Although moisture-bearing winds impinge on the eastfacing margin of the plateau, the high topography of the Eastern Cordillera and the northwestern extension of the Sierras Pampeanas borders the full length of the plateau, effectively shielding this region from significant amounts of eastwardly-derived precipitation ( Fig. 12.2) (WMO 1975;Masek et al 1994;Haselton et al 2002). This situation inhibits the development of an effective bedrock fluvial system, isolating the high plateau from the foreland baselevel, a setting reminiscent of conditions along the northeastern border of the Tibetan Plateau (e.g., .…”

“…Similarly, farther south where the southern hemisphere westerlies impinge on the Patagonian Andes, high precipitation on the windward western side of the orogen contrasts drastically with the arid climate to the east (WMO 1975;Lenters and Cook 1997). These differences create strong effects on erosion and sediment transport in both regions (e.g., Bangs and Cande 1997;Haselton et al 2002;Hartley 2003;Stern and Blisniuk 2003;Blisniuk et al 2005).…”