Resumo

FUCKS, Enrique et al. Evolución geológica-geomorfológica de la cuenca del río Areco, NE de la provincia de Buenos AiresGeologic-geomorphologic evolution of the Río Areco basin, north-eastern of Buenos Aires province. Rev. Asoc. Geol. Argent. [online]. 2011, vol.68, n.1, pp.109-120. ISSN 0004-4822.

The Areco River Basin is part of the drainage system of Pampa Ondulada region, NE Buenos Aires Province. Geomorphic processes that it formed, acted on the loessoid sediments of the Pampeano Formation (Pleistocene) building a morphology contrasting with those of the surrounding environment. In the upper and middle basin there are fluvial successions (Late Pleistocene-Holocene) with different development of pedogenesis. ¹⁴C on OM of these paleosoils yielded 7,000 ± 240 and 1,940 ± 80 years BP in San Antonio de Areco, and 2,320 ± 90 and 2,000 ± 90 years ¹⁴C BP in Castex Bridge, for two important landscape stabilizations, separated in the latter place for a brief episode of sedimentation. The lower basin, together with Cañada Honda locality, was occupied during MIS 1 ingression (Campana Formation) leaving a wide paleoestuary, limited by fossil cliffs. These sediments were generally deposited in low energy environments, associated with three different lithofacies; ¹⁴C ages range between 4,270 ± 70 years BP in this basin and 6,000 ± 80, 6,370 ± 90, 3,640 ±70, 5,630 ± 100, and 5,420 ±,110 years BP in near basins. Based on this information, the late Pleistocene ingression MIS 5e also entered by Areco River putting in evidence, already, the existence of this depression. The external limit of this unit is the Paraná Delta River whose progradation exposed specific morphologies and deposits. In the contact between both morphological units (delta and paleoestuary) is determined by the water streams that, with abrupt direction changes according to deltaic complex development.

Palavras-chave : Areco River; Quaternary; Geomorphologic evolution; Marine level changes.

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