DETAILED STRUCTURAL-ANALYSIS OF THE RIM OF A LARGE, COMPLEX IMPACT CRATER - BOSUMTWI CRATER, GHANA

The 1 Ma Bosumtwi Crater in Ghana is an Il-km-diameter, presumably com plex, well-preserved impact structure that is associated with the Ivor y Coast tektite strewnfield. Detailed structural geologic studies alon g a complete traverse through the northwestern rim section indicated f our zones characterized by distinct deformation styles from just outsi de of the crater rim to near the crater noon Zone 1 is dominated by th ick deposits of lithic impact breccia, intercalated in places with pro ducts of local mass wasting. Zone 2 contains inward-dipping thrust pla nes, conjugate radial fractures, isoclinal folding, and overturned str atigraphic sequences. Zone 3 represents a megabreccia zone, in which b lock size decreases upward and outward toward the rim crest. The inner most zone 4 is dominated by intense thrust faulting of multiple orient ations, resulting in complex duplex-and lens-shaped bodies. These defo rmation 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.