LATE QUATERNARY GEOLOGICAL HISTORY OF RIO GRANGE DO SUL COASTAL PLAIN, SOUTHERN BRAZIL

LUIZ JOSÉ TOMAZELLI, SÉRGIO REBELLO DILLENBURG, JORGE ALBERTO VILLWOCK

Resumo


The sedimentary deposits and geomorphic features preserved in the Rio Grande do Sul coastal plain, southern Brazil, represent a significant record of late Quaternary climatic changes with its associated glacio-eustatic sea-level fluctuations. The sediments of the coastal plain belong to two major depositional systems - an alluvial fan system developed along the inner part of the coastal plain and a barrier-lagoon complex with four distinctive transgressive-regressive cycles seaward. The alluvial fan sediments were derived from igneous and metamorphic rocks of the Precambrian shield and from sedimentary and volcanic rocks of the Paraná Basin. Subsequently, they were reworked by four barrierlagoon systems each representing a transgressive-regressive cycle. Each barrier probably originated at the landward limit of a transgression and was preserved due to regression of the shoreline forced by a glacio-eustatic sea-level fall. The four barrier-lagoon systems are believed to have formed during the last 400 ka assuming a correlation with the highstands represented by the last major peaks of the oxygen isotopic record.

Palavras-chave


Quaternary geology; sea-level variations; Coastal evolution; Rio Grande do Sul coastal plain.

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