Wapsipinicon Group

Interval includes Pinicon Ridge, Otis, Spillville, and Bertram formations. Otis and Bertram formations restricted to east-central Iowa only; Spillville Formation in northeast Iowa only. Pinicon Ridge Formation oversteps Spillville and Otis edges in Fayette, Bremer, Black Hawk, Buchanan, southern Chickasaw counties to directly overlie Sh, Sw, or Om. Primary Lithologies: dolomite, part laminated, variably argillaceous, part fetid; limestone, dense, “sublithographic”, part laminated to intraclastic; dolomite, fossil-moldic to vuggy (Otis-Spillville fms). Secondary Lithologies: limestone/dolomite breccia (evaporite collapse); dolomitic shale and shaly dolomite, gray to green-gray, part silty-sandy; limestone, part peloidal to fossiliferous (Otis Fm). Minor: chert and chalcedony nodules (Pinicon Ridge Fm); sandstone; oolitic limestone (Otis Fm). Extensive anhydrite/gypsum in subsurface outside of outcrop belt. Maximum thicknesses in outcrop belt: east-central Iowa, 60-160 ft (18-49 m); northern Iowa, 10-130 ft (3-40 m), locally absent in Bremer County beneath Dc.
State Iowa
Name Wapsipinicon Group
Geologic age Middle Devonian, upper Eifelian-middle Givetian
Lithologic constituents
Sedimentary > Carbonate > Limestone (Bed)dense, “sublithographic”, part laminated to intraclastic; minor part peloidal to fossiliferous (Otis Fm); inciental oolitic, (Otis Fm)
Sedimentary > Carbonate > Dolostone (Bed)part laminated, variably argillaceous, part fetid; fossil-moldic to vuggy (Otis-Spillville fms); shaly, gray to green-gray, part silty-sandy
Sedimentary > Clastic > Sedimentary-breccia (Bed, Calcareous)limestone/dolomite breccia (evaporite collapse)
Sedimentary > Clastic > Mudstone > Shale (Bed)dolomitic, gray to green-gray, part silty-sandy
Sedimentary > Clastic > Sandstone (Bed)
Sedimentary > Chemical > Chert (Bed)chert and chalcedony nodules (Pinicon Ridge Fm)

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.

NGMDB product
Counties Benton - Black Hawk - Bremer - Buchanan - Cedar - Chickasaw - Clayton - Delaware - Fayette - Floyd - Howard - Jackson - Johnson - Jones - Linn - Louisa - Mitchell - Muscatine - Scott - Winneshiek