Landscape of lakes formed in parabolic and blowout dunes, San Luis province,central Argentina

TRIPALDI, A.; FORMAN, S.L.

Santa Rosa, La Pampa, Argentina

Conferencia; VII International Conference Aeolian Research; 2010

INTA

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} p.MsoTitle, li.MsoTitle, div.MsoTitle {margin:0cm; margin-bottom:.0001pt; text-align:center; mso-pagination:widow-orphan; font-size:12.0pt; mso-bidi-font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:ES-MX; font-weight:bold; mso-bidi-font-weight:normal; text-decoration:underline; text-underline:single;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Most of central and southern San Luis province (central Argentina) is covered by aeolian sand deposits that form diverse landscapes like sand sheets and transverse, blowout and parabolic dunes (San Luis dune field). This region is almost completely covered by vegetation, a savanna dominated by Prosopis caldenia and profuse grassland (Espinal phytogeographical province). Active blowout and parabolic dunes, elongated by northeasterly winds, are common in the eastern area of the San Luis dune field. These geoforms are surrounded by depositional lobes on their lee sides, commonly covered by unvegetated loose sand forming barchanoid crest dunes. Mostly stabilized, compound parabolic dunes occur in the western portion and are elongated by southeasterly winds. One conspicuous feature of this aeolian landscape is the presence of numerous lakes formed in the depressions of parabolic and blowout dunes. The lake size is variable, ranging from few tens of meters to up to 2 km of diameter. These depressions were, at first, likely infilled by groundwater due to aeolian excavation but ecological studies indicate that groundwater rise cannot be ruled out as an important component of lake formation. A recent rise groundwater levels is the result of replacement of dry forest by crops. Sedimentological analysis and OSL dating reveal episodic sand sheet deposition between ca. 33 and 25 ka, with a potentially high lake stand at ca. 11.4 ka. Dune reactivation appears to have occurred into the Holocene with accretion of eolian sand at ca. 9.7 and 1.6 ka. This study reveals that the landscape of blowout- and parabolic-dunes and lakes reflects different sedimentary processes along the late Pleistocene-Holocene, with possibly significant changes in vegetation.