Dunefields of Patagonia

MONTES, A.

Nueva Delhi

Conferencia; 9th International Conference on Geomorphology; 2017

Indian Institute of Geomorphologists

Patagonia (40°-60° S) is the only continental territory exposed to the southern westerlies. The velocity and frequency of the westerly winds generate a landscape strongly influenced by aeolian processes. The winds coming from the Pacific Ocean ascend on reaching the Andes, while cooling adiabatically and generating high precipitation on the western slopes, whereas the eastern side of the Andes is in the rain shadow, which generates true desert conditions. Pans, tablelands, closed basins and ephemeral streams are dominant in the landscape due to the climatic conditions. Dunefields mainly consist of transverse dunes, barchans, sand shadows and sand sheets and they move predominantly in a west-east direction. Yardangs, desert pavements, exhumed roots and decapitated soils were recognized in interdune areas. Longitudinal sand ridges, parallel to the prevailing wind direction, often remain preserved after the dunefields have passed. This allows to recognize the path of the dunes in the past. The barchans and barchanoid transverse dunes have a height between 3.5 and 14 m. The average speed movement measured in the dunes located at the east of Lake Colhué Huapi is 45 m/year. The sand sheets are 0.4 - 1.2 m thick and they are located at the eastern end of the dunefields as sandy tongues shaped in top view. Their shifting speeds are the highest in the region and often exceed 100 m/year. Dunes with similar morphology show large textural differences associated with the sediment supply environment. The main sediment supply to dunefields development is lakebed of pans and west facing beaches of lakes and gulfs. Also, they feed by erosion of top soil horizons of interdune areas. The climatic variations control the development and stabilization of all the dunefields studied.