Eau Claire Formation (IACAe;0)

Eau Claire Formation

Subcrops beneath Mississippi River alluvium in Allamakee County; surface exposures absent. Primary lithologies: sandstone, very fine to fine grained, part argillaceous; shale, silty, gray to green-gray, part glauconitic. Secondary lithology: siltstone, part argillaceous, part dolomitic. Minor: dolomite. Thicknesses: 120-145 ft (37-44 m).

State	Iowa
Name	Eau Claire Formation
Geologic age	Middle Cambrian, upper Marjuman (formerly Dresbachian)
Lithologic constituents	Major Sedimentary > Clastic > Sandstone (Bed)very fine to fine grained, part argillaceous Sedimentary > Clastic > Mudstone > Shale (Bed, Glauconitic)silty, gray to green-gray, part glauconitic Minor Sedimentary > Clastic > Siltstone (Bed)part argillaceous, part dolomitic Incidental Sedimentary > Carbonate > Dolostone (Bed)
References	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	NGMDB product page for 96753
Counties	Allamakee

Eau Claire Formation

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.