El desarrollo de abanicos deltaicos (fan deltas) en el sistema lacustres Pueyrredón-Posadas y su correlación con los controles alocíclicos postglaciales del Pleistoceno-Holoceno en la Patagonia andina argentina

HORTA, LUIS RUBÉN; GEORGIEFF, SERGIO M.; BUSNELLI, JOSÉ; ASCHERO, CARLOS A.

Serie Correlación Geológica

nstituto Superior de Correlación Geológica, Consejo Nacional de Investigaciones Científicas y Técnicas

Año: 2012 vol. 29 p. 9 - 20

1666-9479

THE DEVELOPMENT OF FAN DELTA IN THE SYSTEM LAKE PUEYRREDÓN-POSADAS AND ITS CORRELATION WITH ALLOCYCLIC CONTROLS POSTGLACIAL PLEISTOCENE-HOLOCENE IN THE PATAGONIAN ANDES, ARGENTINA. At the foot of the Andes in Patagonia argentine, a series of oligotrophic lakes were formed by deglaciation during Late Pleistocene ? Early Holocene. The Pueyrredón-Posadas Lacustrine System (P-PLS) in Argentina belongs to this group of postglacial lakes. In the southern coast of the P-PLS four fan-deltas were developed; the largest development in area is located in the mouth of Furioso River Eastward, whereas the others three decrease in size Westward. The Furioso River fan-delta is connected with deposits of a frontal moraine; both together produce the separation of Pueyrredón and Posadas Lakes. The Oro and Suyai fan-deltas have developed barriers parallel to the coast by wave actions related to intense winds from West. The apexes of these fan-deltas are correlated with datings in lacustrine levels at the North coast of the PPLS. At both sides of fan-deltas, two terraces were identified, at 300 masl and 400 masl. The timing in the base level fall of P-PLS allowed this particular systematic development of fan-deltas, as in geoform sizes (directly related to size of drainage basin) as altitudes of these apexes, with a methodical diminution of both parameters in the East-West sense. The bathymetric variations in P-PLS were corroborated with the integration of a digital elevation model and field work. Thus, the development of these fan-deltas in the P-PLS could be, mainly, controlled by allocyclic factors: climate and base level.