Nyorai kupfuurira kweiyi ndima - Nokuratidzwa kwezvikwata zvepasi zveboka iri mumafashamo a1993
, boka rose reCouncil Grove Group, kubva pachikomo cheSpeiser Shale kusvika padziva reAmericus limestone, rinoratidzwa kuti riongororwe kubva kumusoro kusvika pasi muTuttle Creek Lake Spillway.