MORPHOTECTONIC CHARACTERIZATIONOF BASEMENT COMPLEXROCKS FROM SATELLITE IMAGES IN IGARRA SCHIST BELT,SOUTHWESTERN NIGERIA

Abstract

The effects of tectonism in a terrain has become a major concern to geologist and engineers, as structures generated from tectonism e.g. lineaments serve as a trap for natural resources like solid minerals, hydrocarbon, and groundwater, also considered during engineering work. This makes the study of tectonics and its effect on rock types very important. In order to understand how tectonism have affected the rocks in the study area, a morhophotectonic characterisation study was carried out using lineaments and morphology (forms and shapes) observed from remotely sensed data, which will serve as a guide for geologist and engineers during exploration and construction. This study was carried out using Shuttle Radar Topographic Mission (SRTM), Digital Elevation Model (DEM), Landsat OLI/TIRS and Aeromagnetic data. The approached used includes image filtering, lineament extraction, lineament grouping, statistical analysis of the distribution of lineament. Statistical quantification of counts, mean length, density and orientation was used to infer the effect of tectonic activity on the various rock types. The extracted lineament shows prominent trend in N-E, N-W, and N-S trends were also common. Statistical analysis however, shows different number of count for different images and also for different angle of filtering used. The morphological comparison of the filtered images showed that the basement complex rocks have been subjected to a lot of stress which is associated with tectonism that have affected that area. The quartz mica schist, migmatite and the biotite hornblende granite present in the basement complex area showed more effect of the tectonism as seen in lineament count and the lineament density map. The morphotectonic studies carried out therefore, shows that the various rock types present in the study area have unequal distribution of the lineaments and therefore have been affected unevenly during the tectonic episode that happened in the study area.