|Geologic age||Upper Ordovician; Richmondian (upper Katian)|
Sedimentary > Carbonate > Dolostone (Bed)argillaceous, part shaly, variably fossiliferous (part with common trilobites); part argillaceous, part cherty to very cherty (northern Iowa); incidental phosphatic to very phosphatic, argillaceous (Elgin Mbr.)
Sedimentary > Clastic > Mudstone > Shale (Bed)green-gray, variably dolomitic, mostly unfossiliferous; minor brown to brown-gray, organic, part graptolitic, part finely laminated (lower strata); minor interbedded dolomite and shale, part nodular, part fossiliferous; incidental red shale (Neda Mbr.)
Sedimentary > Carbonate > Limestone (Bed)dolomitic limestone to limestone, argillaceous, part cherty to very cherty, variably fossiliferous, part crinoidal (northern Iowa)
Sedimentary > Chemical > Phosphorite (Bed)granular to massive (basal unit)
Sedimentary > Chemical > Banded-iron-formation (Bed)ooidal, (Neda Mbr.)
Witzke, Brian J., Anderson, Raymond R., and Pope, John P., 2010, Iowa Geological and Water Survey, DNR, Bedrock Geologic Map of Iowa, OFM-2010-1. Scale 1:500,000.
|Counties||Allamakee - Black Hawk - Bremer - Buchanan - Chickasaw - Clay - Clayton - Clinton - Delaware - Dubuque - Emmet - Fayette - Howard - Jackson - Jones - Kossuth - Palo Alto - Scott - Winnebago - Winneshiek|