Resumo

CAVALLOTTO, J. L.. Holocene evolution of the coastal plain of the south margin of the Río de la Plata. Rev. Asoc. Geol. Argent. [online]. 2002, vol.57, n.4, pp.376-388. ISSN 0004-4822.

The coastal plain of the southern margin of the Río de la Plata evolved on a substratum formed during the Holocene transgression. Its present configuration is the result of the progradation processes accompanying the last sea-level fall. Coastal plain evolution was controlled by the interaction of hydrometeorological conditions (wind-wave relation, currents and tidal climate), migration of a muddy depocenter, relative sea-level fluctuations and geometry of the pre-Holocene surface. Geometry and sea-level fluctuations determined the distribution, extension and development of the sedimentary sequence, whereas hydrometeorological conditions controlled the rate of sediment supply and transport. The most important feature of the pre-Holocene surface was the ancient fluvial valley of the Río de la Plata. When the last rise of sea-level reached the upper border of the valley, a headland located at the south-eastern edge of the coastal plain behaved as a point of attack for the incoming waves coming from the south-east. This induced the formation of two littoral currents drifting in opposite directions, one to the north-west (towards the Río de la Plata), and the other to the south-west (towards Bahía Samborombón), conditions that still occur today. Evolution of the coastal plain may be summarised in three stages: (1) estuarine, coastal plain and fluvial-estuarine deltaic that represents the processes that filled up the palaeovalley, (2) coastal progradation and (3)the installation of a deltaic system.

Palavras-chave : Holocene; Coastal plain; Geomorphology; Río de la Plata.

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