Abstract

HORTA, Luis R; GEORGIEFF, Sergio M; BUSNELLI, José  and  ASCHERO, Carlos A. 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. Ser. correl. geol. [online]. 2013, vol.29, n.2, pp.21-32. ISSN 1666-9479.

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 this 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 firontal 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 firom West. The apexes of these fan-deltas are correlated with datings in lacustrine levels at the North coast of the P-PLS. At both sides of fan-deltas, two terraces were identifed, 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 feld work. Thus, the development of these fan-deltas in the P-PLS could be, mainly, controlled by allocyclic factors: climate and base level.

Keywords : Fan-deltas; Lacustrine System; Allocyclic controls; Late Pleistocene-Early Holocene; Pueyrredón Lake.

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