Parabolic megadunes in a subtropical Quaternary inland dune field, southwestern Pampas, Argentina

TRIPALDI, ALFONSINA; MEHL, ADRIANA; ZÁRATE, MARCELO A.

GEOMORPHOLOGY

ELSEVIER SCIENCE BV

Año: 2018 vol. 321 p. 103 - 116

0169-555X

The Utracán paleo-dune field (La Pampa Province, Argentina, southern South America) was examined by remote sensing, morphometric analyses and field surveys as a case study of complex megadunes of inland deserts. The paleo-dune field is within the Utracán-Argentino valley, one of the transverse valleys of La Pampa Province excavated into a regional structural plain. Similar paleo-dune fields occur within these valleys. Utracán dunes are mostly stabilized by grasses, deeply disturbed by cattle grazing and agriculture. The paleo-dune field is formed by complex parabolic megadunes with superimposed dunes. Parabolic megadunes present lengths of trailing arms of 3.3-12.9 km, widths between them of 2-2.9 km and heights of 7-38 m. The position of the dune noses at the northeastern tip of the bedform and measured SW-NE orientation of arms indicate a mean transport direction to azimuth 68.2º. Above the parabolic arms, and isolated in the paleo-dune field, there are compound blowout dunes (clusters of several blowouts forming a larger bedform). They show the depositional lobes to the NE, with a measured mean transport direction to azimuth 58.1º. The SW-NE longitudinal length varies between 324 and 1302 m and the NW-SE transverse length between 114 and 622 m. Other parabolic arms show low (