Resumo

KOKOT, Roberto R  e  CHOMNALEZ, Florencia. Retreat of the line of coast in Las Grutas, Río Negro province. Rev. Asoc. Geol. Argent. [online]. 2012, vol.69, n.1. ISSN 0004-4822.

The town of Las Grutas, province of Río Negro, has a cliffed coastline with an extensive coastal platform. Mentioned land-forms are formed above Paleogene sedimentary rocks for the Gran Bajo del Gualicho Formation. Rely on them in erosive unconformity Pleistocene beach ridges deposits and the sequence ends with Holocene dune deposits. By comparing aerial photographs and satellite images, it was determined that the coast was eroded from 1969 to nowadays. The retreat was studied by comparing aerial photographs and georeferenced satellite imagery. The results show a downward trend of the dunes, the retreat of shore platforms and coastal shoreline. The latter has an average erosion rate of 1.50 m in 39 years. However, the central and northern sectors are most affected reaching up to 3 m setback in the same period. These erosion and resulting mass movement processes respond mainly to intense wave action on coastal outcrops, especially in coastal areas most exposed to the breakers, as well as the determining geological/structural outcrops exposed. The dangerous scenario is exacerbated by human action that contributes to the acceleration of the natural processes.

Palavras-chave : Coastal erosion; Shore platform; Pleistocene beach ridges; Sea levelfall.

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