Scanning Electron Microscopy (SEM) in the surficial cover analysis of the low fluvial-marine terraces in the southern coast of São Paulo state, Brazil

Abstract

The Ribeira de Iguape estuarine system in Southeastern Brazil has resulted from the complex interactions betweenallogenic (climate, tectonics, and human interventions) and autogenic geomorphological processes. Early studies have shownthat the relationship between sedimentary balances, fluvial discharge, and Holocene climate pulses resulted in the coastlinedisplacement and low fluvial-marine terraces morphogenesis, which are composed of the marine and fluvial sedimentaryunits. In this perspective, this study aimed to investigate whether the microtextural and morphological records on the quartzgrains associated with the different allostratigraphic units (marine and fluvial) correspond to the paleoenvironmentsidentified in previous studies. In this study we have used a combination of analyses (grain-size, microtextural, and absolutedating) applied to the surficial cover sampled from two fluvial-marine terraces located on the right and left banks of theIguape river channel. The results show correspondences between paleoenvironments and microtextures found on the quartzgrains, confirming the statements addressed in previous studies that indicated the coastline was positioned about 9 kminland around 3.5-2.7 ka.

Keywords

• transgressões e regressões
• pulsos climáticos
• holoceno superior