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1 Polish Geological Institute Special Papers

1 2004

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Evolution of the semi-enclosed basins and surrounding coastal plains adjacent to the Pampean Region, Argentina

Violante R. A., Cavallotto J. L.

Polish Geological Institute Special Papers

2004

Vol. 11

59-70

The coastal plains adjacent to the Pampean region in eastern Argentina evolved during the Holocene in response to interaction between sea level fluctuations and different littoral dynamic factors in such a way that several sedimentary environments developed. Evolutionary stages can be synthesised in three periods: 1) the post-LGM transgression, when landward migrating coastal barriers extended on the present shelf under the effect of a dominant northward littoral drift; 2) the last stages of the transgression (between 8000 and 6000 years BP), when the rising sea flooded the Alto Marítimo (a pre-Holocene positive morphological feature which in previous times separated the course of the de la Plata river from the open sea), resulting in a new coastal configuration in which the presence of two headlands, Punta Piedras (in the north) and Villa Gesell (in the south), influenced the coastal processes so changing the original regional northward littoral drift into cell-type circulation systems; 3) between 6000 years BP and the present, when progradation processes characterised by barriers and beach ridges development dominated as a result of the sea level fall and an excess of sediment supply. As a result, coastal semi-enclosed basins located in between the headlands, such as Samborombón bay and Mar Chiquita lagoon, became the main depocenters where low-energy conditions (coastal lagoons, tidal flats and marshes) prevailed due to its isolation from the open-sea by the barriers and ridges. Interaction between southward migration of coastal environments associated to the northern headland and northward migration of those related to the southern headland was a very important process in shaping the present morphology of the area.