Morphometric and Structural Evaluations of Satellite Data from the Bosumtwi Impact Structure and Adjacent Areas in Ashanti, Ghana

The Bosumtwi impact crater in Ashanti, Ghana is one of the most thoroughly investigated impact structures in Africa. Nevertheless, by the evaluations of Sentinel 1 and 2, and Landsat data as well as by ALOS PALSAR, ASTER and SRTM digital elevation model (DEM) data further geomorphological and structural knowledge can be derived. Morphometric maps were used to visualize the concentric and radial drainage and valley pattern surrounding the impact crater. The larger valleys are arranged in a nearly concentric and radial pattern like the river Pra and its tributaries, the Ofin, Anum and Brim river, tracing the outer, southern border of the impact affected area. From the ASTER and SRTM DEM data the morphological drainage basin was calculated. The drainage basin-outline is nearly circular, discharging into the Pra river in the southern part. Structural evaluations of satellite radar and optical data reveal that linear and circum-linear features can be detected more than 80 km around the Bosumtwi impact crater. Small-scale/artisanal mining activities in this area are visible on satellite images and, thus, indirectly tracing ore deposits. As detailed mineral maps are not publicly available, the position and distributions of mining areas was used as indicator for the occurrence of mineral deposits, especially placer deposits. Their occurrence and the distribution of the mining areas follows the larger rivers. Weathering processes along the deformation pattern and erosion and sedimentation probably had an influence on placer deposit development.