Fort Benton Group (IAKf;0)

Fort Benton Group

Interval includes “Graneros” Shale, Greenhorn Formation, Carlile Shale. Primary Lithologies: shale, medium to dark gray, variably silty, calcareous to very calcareous. Secondary lithologies: chalk, marl, argillaceous limestone, with skeletal (inoceramid) packstones; shale, gray, silty, noncalcareous. Minor: siltstone; calcite and siderite concretions. Maximum thickness 265 ft (80 m).

State	Iowa
Name	Fort Benton Group
Geologic age	Upper Cretaceous, upper Cenomanian-Turonian
Lithologic constituents	Major Sedimentary > Clastic > Mudstone > Shale (Bed, Calcareous)medium to dark gray, variably silty, calcareous to very calcareous; minor gray, silty, noncalcareous Minor Sedimentary > Carbonate (Bed)chalk, marl, argillaceous limestone, with skeletal (inoceramid) packstones Incidental Sedimentary > Clastic > Siltstone (Bed)calcite and siderite concretions
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	Cherokee - Clay - Dickinson - Ida - Lyon - O'Brien - Osceola - Plymouth - Sac - Sioux - Woodbury

Fort Benton Group

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.