The Maquoketa formation in the outcrop area has been assigned a maximum thickness of 257 feet by earlier surface workers. Recent subsurface study in the same area reveals a thickness of 300-320 feet of Maquoketa sediments. Until now the correlation of subsurface units to recognized surface members has been hampered by this discrepancy. The recognition and identification of a new unit in the Elgin member of the Maquoketa formation, and a greater measured thickness of the Isotelus zone has resolved this difference.
Proceedings of the Iowa Academy of Science
©1959 Iowa Academy of Science, Inc.
Parker, Mary C.; Dorheim, Fred H.; and Campbell, Russell B.
"Resolving Discrepancies Between Surface and Subsurface Studies of the Maquoketa Formation of Northeast Iowa,"
Proceedings of the Iowa Academy of Science, 66(1), 248-256.
Available at: https://scholarworks.uni.edu/pias/vol66/iss1/35