Mapeamento geológico do município de São Lourenço do Sul, Planície Costeira do Rio Grande do Sul, Brasil

Abstract

Sao Lourenco do Sul, RS, is located on Lagoa dos Patos the west margin in a region with very particular geologic and geomorphological characteristics. The crystalline basement is located near the lagoon’s coast line; interacting with the Coastal Plan of Rio Grande do Sul (PCRS) deposit’s, resulting in a large geomorphological diversity. These preserved deposition record and can contribute to both the relative sea-level fluctuations (RSL) during the Quarternary period and processes of coastal sedimentation and erosion. The purpose of this study is to define the main geological units, with a focus on the Quartenary deposits São Lourenco do Sul city. These definitions were made in accordance with data olitained from remote sensors (Satellite Imaging Corporation, LANDSAT 7 ETM+) and descriptions of sedimentary deposits and crystalline rocks. Image processing software was used together with outcrop descriptions, topographic data, granulometric analysis, assessment of statistical parameters and imaging by georadar to determine the depositional geometry of the coastal ridges present in the mapped area. As a result of this study it is presented geological map, characterization of four units geomorphological and geological. These units are: the crystalline and rocks, the alluvial fans deposits, the lagoon plan deposits and the coastal ridges, where it was possible to recognize progradational sequences. The methodology applied and the results allowed an increase knowledge regarding geological features present in the study area specially the quaternary in the sedimentary deposits.