Mezue ahịrịokwu na-esonụ:
N'afọ 1993 mgbe idei mmiri ahụ mere, a kpughere akụkụ nile nke Council Grove Group, site n'ugwu Speiser Shale ruo n'ọdọ mmiri Americus limestone, maka ọmụmụ ihe site n'elu ruo na ala na Tuttle Creek Lake Spillway.