Bosumtwi Impact Crater, Ghana: A Remote Sensing Investigation

Abstract

The Bosumtwi crater in Ghana is a ~1.05 million year old, very well-preserved complex meteorite impact structure of approximately 10.5 km rim-to-rim diameter. The interior of the structure is largely filled by Lake Bosumtwi, and the crater rim and the environs of the crater are covered by dense tropical rainforest. Thus, direct geological study of this structure is not easy; but remote sensing and geophysical data can be used to better constrain the surface and subsurface geology. Landsat Thematic Mapper (TM) data reveal detailed structure of the crater rim, including arrays of radial, concentric, and tangential or oblique fractures. In all data sets, the presence of an apparent ring feature at ~10–11 km from the crater center is visible. Digitised topographic information and, to a lesser extent, ERS-1/2 radar data provide an improved picture of the crater morphology. A digital elevation model (DEM) for the wider Bosumtwi crater area also reveals the presence of a subdued elevation feature at about 10–11 km radial distance from the lake center, which, in the western area, coincides with the distribution pattern of vegetation. Perspective views of the DEM and other remote sensing data suggest the existence of a further structural feature at 17–19 km distance from the crater center, and which is mainly visible in the southeast sector. An “outer rim“ topography is also known from other impact structures, for example, the Elgygytgyn crater in Russia; the origin of this feature is still debated, but the existence of two apparent ring features may suggest that they represent ring faults caused by the impact compression.