Cambio hidrológico asociado al Último Maximo Glacial-Altitermal durante la transición Pleistoceno-Holoceno en el borde oriental de Puna Norte.

Abstract

ABSTRACT. The environment of the Andean Puna Plateau is mostly characterized by the dominance of evaporative processes due to aridity. Since the intermittent runoff lacks the morphodynamic competence to generate the present day landscape, authors have usually considered that the Puna landscape is a remnant feature of the Miocene arid-climate persistence. Then, a Quaternary-sensu lato-age was assigned to salars, alluvial fans and other geomorphologies. We present evidences from the endorheic depression of Guayatayoc-Salinas Grandes (GSG) located at 3,400 m a.s.l. in the eastern border of northen Puna. The basin includes a saline playa domain in the north (Guayatayoc Playa Lake) and a salt pan in the southern part (Salinas Grandes). We have identified two dissimilar processes originating the subdivision of the GSG depression. The characterization of those processes included sedimentological and geomorphological observations, as well as chronologies using luminescence and radiocarbon. Evidences reveal the development of a saline-lacustrine water body that is associated with the Last Glacial Maximum. During the Late Pleistocene and until ~13.8 cal kyr BP, lake shores were modelled in the front of distal-alluvial fans, the sedimentary aggradation was widespread, and associated with kaolinitic-clay accumulation, inyoite, and the formation of peat-deposits. An environmental change towards aridity occurred after 13.8 cal kyr BP, and wetter conditions returned during the early to middle Holocene, around 9 cal kyr BP. Then, incisive river dynamics accompanied the establishment of a playa lake, with montmorillonitic-fine sediments and ulexite generation during later Holocene. The subdivision of the GSG depression onset by the two following processes: 1. the topographic decoupling, that is associated with Las Burras's alluvial fan aggradation during Pleistocene; 2. the lacustrine regression phase at 13.8 cal kyr BP. Therefore, Guayatayoc and Salinas Grandes are saline systems functioning as a playa lake and a salt pan, respectively, since the Holocene, due to environmental constraints.

Dust deposition tracks late-Holocene shifts in monsoon activity and the increasing role of human disturbance in the Puna-Altiplano, northwest Argentina

“…Diatoms could alternatively live in situ within the peat matrix, although the low pH of SV1 (generally < 4) would likely restrict diatoms to a few tolerant genera (mainly Eunotia, Nitzschia and Pinnularia ; Denicola, 2000). The diverse diatom assemblage found in the core ash is more likely to flourish in the more neutral/basic conditions common to the endorheic basins of the Puna (López Steinmetz and Galli, 2015; McGlue et al, 2012).…”

Palynological evidence of the geoecological belts dynamics from Eastern Cordillera of NW Argentina (23° S) during the Pre-Last Glacial Maximum

“…In this context, the scarce representation or even complete absence of the Late Glacial and Holocene sedimentary record could be explained by local geomorphological inactivity or by recent eolian deflation. Similarly at Laguna de Pozuelos (McGlue et al, 2013) and Laguna Guayatayoc (López Steinmetz and Galli, 2015), there is also a noticeable reduction of the record during the last 20,000 cal. years BP while Sierra de Santa Victoria and Zenta have better records for the Pleistocene-Holocene transition (Schäbitz et al, 2001;Zech et al, 2009).…”

“…Several authors suggest the development of paleolakes in Sierra de Santa Victoria and Laguna Guayatayoc as a consequence of glacier melting and precipitation increase between 20,000 and 17,000 cal. years BP (Zech et al, 2009;López Steinmetz and Galli, 2015) and in Laguna de los Pozuelos, McGlue et al (2013) identified a lithostratigraphic unit which characterize a predominantly palustrine environment between 37,000 and 23,000 cal. years BP.…”