SHALLOW GEOLOGICAL TRANSECT OF WETUMPKA IMPACT STRUTURE, ALABAMA

Access to key public rights of way and recent core drilling affords the opportunity to construct a shallow geological transect across the ~ 5 km, Late Cretaceous, marine-target impact structure at Wetumpka, Alabama. From northwest to southeast, the transect encountered deformed crystalline rim terrain, vertically stacked sedimentary target megablocks, sedimentary target megablocks in impactite matrix, stacked and faulted sedimentary target megablocks, interior polymict impact breccia, resurge chalk deposits, and steeply inclined, deeply weathered (saprolitic) crystalline rim terrain. Core drilling near the transect indicates that sedimentary target megablock deposits are lateral facies equivalents, whereas the resurge chalk deposits and interior impact breccia unit rest upon those two facies. The relative age of the resurge chalk deposits and the interior impact breccia is not known at this time. The formative events that generated the units seen in the geological transect are all related to late stage modification of the Wetumpka impact structure and likely represent the last few minutes in Wetumpka’s sequence of events.