Geologic-geotechnical map of Bacanga river basin, São Luís Island (MA), Brazil

Abstract

This paper presents the results of a study of geological characteristics of the Bacanga River basin materials, located in west zone of São Luís city (MA), Brazil. This basin is inserted on geomorphologic unity named Golfão Maranhense, according to the regional geomorphologic classification, with two marked relief forms: dissected hills and fluvial-marine plains. The studies aimed the elaboration of a geologic- geotechnical map based on progressive-detailed method, with geological, soil and geomorphological data plotted on a topographic base (1:20.000). Photogeological analysis was the main research tool, followed by field control and in situ tests. The mapping recognized six geological-geotechnical features: Unity I – built deposits; Unity II – flat surface valleys; Unity III – sandy facies of Barreiras Formation; Unity IV – sand-clayey facies of Barreiras Formation; Unity V – clayey facies of Barreiras Formation; Unity VI – Itapecuru Formation grounds. In these features were identified geological processes and environmental problems that make up the dynamics of Bacanga River basin. The confection of the geologic-geotechnical map is considered an indispensable tool to support the planning of land use. Keywords: Geologic geotechnical mapping, uplands, Bacanga River, São Luís.