Hierarchic classification and mapping of modern eolian fields of northwestern Argentina

TRIPALDI, A.; LIMARINO C.O.

Florencia, Italia

Congreso; 32nd International Geological Congress; 2004

International Union of Geological Sciences

Northwestern Argentina have several intermontane valleys limited by the Andean Range to the West and uplifted basement blocks (Pampean Ranges) to the East. These valleys present arid to semiarid climates that favour a landscape shaped by mass wasting processes, ephemeral currents and wind action. Moreover, dry foehn winds descending from the Andean Range transportimportant amount of sediments. Wind-blown sands are then widely distributed appearing as different kinds of dunes, deflationary forms and sand sheets that all together form "valley eolian fields". Vegetation cover varies from scarce bushes to small trees.Owing to the fact that human habitat and agriculture, among many other human activities, depend strongly on the kind of substrate, the location of eolian fields as well as its nature is very important for human developing. Remote sensing has proved to be a very useful tool for examining extensive areas. For this reason, remote sensed images and aerial photographs together with field data were used for classifying and mapping the eolian deposits located between 27° and 35° of south latitude of northwestern Argentina.Eolian fields can be classified as: 1) dunefields, 2) eolian sand sheets,3) fluvial-eolian interaction fields and 4) stabilized eolian fields. Dunefields are typically formed by dunes and, in some cases, also draas. Deflationary blowout forms can be present as well. Although in some dunefields wind action is partially limited due to some vegetation cover, sand is still available for being transported as shown by the presence of eolian ripples and slipfaced dunes. The main dunefields are Médanos Grandes, Médanos de las Chacras, Lomas de laEstancia, Los Colorados and Campo de Belén. Eolian sand sheets and fluvial-eolian interaction fields are characterized by a low-relief irregular topography covered by eolian ripples and few small dunes. Moreover, interaction fields show a close interrelation between ephemeral currents and the eolian cover. These kinds of valley eolian fields appear in El Jumeal, Gualilán, Ampacama, Mogna, Punta de Agua, Guandacol, Antinaco, Pipanaco, Medanitos and Campo del Arenal valleys. Finally, in the stabilized eolian fields vegetation cover has increased enough to not allow almost any sand movement. These areas include degraded dunes and sand sheets. Larger stabilized eolian fields occur in Llanura de la Travesía in the Mendoza province and Campos de las Salinas in La Rioja province.