Abstract

The 1 Ma Bosumtwi Crater in Ghana is an 11-km-diameter, presumably complex, well-preserved impact structure that is associated with the Ivory Coast tektite strewnfield. Detailed structural geologic studies along a complete traverse through the northwestern rim section indicated four zones characterized by distinct deformation styles from just outside of the crater rim to near the crater floor. Zone 1 is dominated by thick deposits of lithic impact breccia, intercalated in places with products of local mass wasting. Zone 2 contains inward-dipping thrust planes, conjugate radial fractures, isoclinal folding, and overturned stratigraphic sequences. Zone 3 represents a megabreccia zone, in which block size decreases upward and outward toward the rim crest. The innermost zone 4 is dominated by intense thrust faulting of multiple orientations, resulting in complex duplex- and lens-shaped bodies. These deformation styles generally correspond to those previously reported from the rims of simple bowl-shaped meteorite-impact craters and appear to be characteristic of impact structures in general.

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