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

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 68.2°. 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 58.1°. 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 (