THE CAMAQUÃ RIVER PALEODRAINAGE ON THE COAST OF RIO GRANDE DO SUL

Abstract

The analysis of highresolution seismic records (3.5 and 7.0 kHz) obtained in the Patos Lagoon revealed the presence of several buried channels that deeply dissected the Rio Grande do Sul coastal zone (Southern Brazil) before the installation of the present, low-relief and gently undulating coastal plain. Landwards, the paleodrainage system mapped from the seismic records can be linked with the present course of the Camaquã River. Oceanwards, it can be connected with the system of paleochannels recognized by previous studies in the adjacent continental shelf and slope by means of seismic and morphostructural data. Landwards, the drainage was incised into the coastal prism deposited during previous sea level highstand events of the Quaternary. The paleodrainage path recognized on the coastal plain and inferred to the adjacent continental shelf represents a river-shelf system, linking the continental drainage basin to the depositional settings on the marginal basin, bypassing the continental shelf exposed during a forced regression event.