|Name||Maquoketa Formation or Group|
|Geologic age||Upper Ordovician (Stage 6 to Hirnatian)|
Sedimentary > Clastic > Mudstone > Shale (Bed, Calcareous)Shale can be silty, dolomitic, or calcareous.
Sedimentary > Carbonate > Limestone (Bed)Limestone can be oolitic, bioclastic, or shaly or argillaceous.
Sedimentary > Clastic > Sandstone (Bed, Calcareous)Sandstone can be shaly or argillaceous, or calcareous.
Sedimentary > Carbonate > Dolostone (Bed)Dolomite can be bioclastic.
|Comments||Thickness from stratigraphic columns: Cape Ls (0-8’), Maquoketa Fm (0-325’), Leemon Fm (0-25’) in southern Illinois (south of 40 degrees north latitude); Scales Sh (0-135’), Ft. Atkinson Ls (0-60’), Brainard Sh (0-100’), and Neda Fm (0-15’) in northern Illinois (north of 40 degrees north latitude). The Maquoketa Fm is comprised, from oldest to youngest, of the Cape La Croix Shale, Thebes Sandstone, Orchard Creek Shale, Girardeau Limestone, and Noix Oolite in southern Illinois (south of 40 degrees north latitude); the Maquoketa Group is comprised, from oldest to youngest, of the Scales Shale, Fort Atkinson Limestone, Brainard Shale, and Neda Formation in northern Illinois (north of 40 degrees north latitude). Unit name in original GIS (Esri shapefile IL_Geologic_Units_500K_2005_Py) is 'Maquoketa Shale Group'; name on Legend of geologic map is 'Maquoketa Formation or Group'.|
Kolata, D.R., comp., 2005, Bedrock Geology of Illinois: Champaign, Ill., Illinois State Geological Survey, Illinois Map Series 14, scale 1:500,000.
|Counties||Alexander - Boone - Bureau - Calhoun - Carroll - Cook - DeKalb - DuPage - Greene - Grundy - Iroquois - Jersey - Jo Daviess - Kane - Kankakee - Kendall - Lake - La Salle - Lee - McHenry - Monroe - Ogle - Pike - Stephenson - Union - Whiteside - Will|