Formation includes Welton, Buck Creek Quarry, Waubeek, Palisades-Kepler, Johns Creek Quarry members; Palisades-Kepler and Johns Creek Quarry members contain carbonate mound facies. Erosionally beveled and truncated beneath Dw. Primarily Lithologies: dolomite, porous, fossil-moldic to vuggy, part very crinoidal (includes Welton Mbr); dolomite, cherty to very cherty, dense (Buck Creek Quarry Mbr). Secondary Lithologies: dolomite, sparsely fossil-moldic, dense, part vuggy (includes Waubeek Mbr); dolomite, coarsely crystalline, part very crinoidal (within Johns Creek Quarry, Palisades-Kepler mbrs); dolomite mudstone, dense. Minor: dolomite, slightly argillaceous; quartz druse, chalcedony, silicified fossils. Maximum thicknesses: 94-240 ft (29-73 m); may reach thicknesses to 300 ft (90 m); beveled and truncated beneath Dw.
Mosalem Formation infills erosional paleovalleys incised into Maquoketa Shale; absent outside of paleovalleys. Lower Hopkinton Formation locally contains carbonate mound facies in Bremer County. Blanding Formation oversteps Tete des Morts-Mosalem edge in southern outcrop area. Primary Lithologies: dolomite, fossil-moldic to vuggy, fine to coarse crystalline; dolomite, dense to porous, cherty to very cherty, nodular to bedded chert (especially Blanding Fm). Secondary Lithologies: dolomite, dense, sparsely fossiliferous; dolomite, argillaceous, part laminated (Mosalem Fm). Minor: chalcedony, silicified fossils. Maximum thicknesses total interval: 160-330 ft (49-100 m), thickest in Dubuque, Jackson, Jones counties where Mosalem present; southern outcrop total thickness 65-130 ft (20-40 m). Formation thicknesses: Hopkinton, 65-160 ft (20-49 m); Blanding, 25-65 ft (8-20 m); Tete des Morts, 0-35 ft (11 m); Mosalem, 0-100 ft (30 m).
Includes Elgin, Clermont, Fort Atkinson, Brainard, and Neda members. Overlain by Silurian strata in east-central Iowa, incised paleovalleys beneath Mosalem Fm.; truncated beneath Devonian strata in northern-most counties. Primary lithologies: shale, green-gray, variably dolomitic, mostly unfossiliferous; dolomite, argillaceous, part shaly, variably fossiliferous (part with common trilobites); dolomite, part argillaceous, part cherty to very cherty (northern Iowa). Secondary lithologies: shale, brown to brown-gray, organic, part graptolitic, part finely laminated (lower strata); dolomitic limestone to limestone, argillaceous, part cherty to very cherty, variably fossiliferous, part crinoidal (northern Iowa); interbedded dolomite and shale, part nodular, part fossiliferous. Minor: phosphorite, granular to massive (basal unit); dolomite, phosphatic to very phosphatic, argillaceous (Elgin Mbr.); ooidal ironstone and red shale (Neda Mbr.); pyrite, finely disseminated to nodular, pyrite cements. Maximum thicknesses: generally 200-275 ft (60-85 m) beneath Silurian, locally 100-200 ft (30-60 m) beneath Mosalem Fm.; 75-180 ft (23-55 m) where capped by Devonian strata in northern Iowa.
Formation includes Anamosa, Brady, LeClaire (Scott-Muscatine counties) members; Brady and LeClaire members are carbonate mound facies. Erosionally beveled and truncated beneath Dw. Primary Lithologies: laminated dolomite (Anamosa Mbr), part fetid/organic to east (Scott-Clinton counties); dolomite mudstone, dense, featureless. Secondary Lithologies: dolomite, fossiliferous to vuggy, moldic, part brachiopod-rich (Brady Member); dolomite, part coarsely crystalline, vuggy, fossiliferous to sparsely fossiliferous, part crinoidal (LeClaire Member). Minor: chert; intraclastic dolomite. Maximum thickness: 180 ft (55 m); beveled and truncated beneath Dw.
Galena Group includes Decorah, Dunleith, Wise Lake, Dubuque formations; Platteville Formation includes Pecatonica, McGregor members; Glenwood Shale forms thin basal shale unit. Primary lithologies: dolomite, part porous to vuggy, fossiliferous, part cherty; limestone and dolomitic limestone, fossiliferous, part cherty (note: Galena Group entirely limestone to north, entirely dolomite to south, interstratified limestone-dolomite in intervening areas). Secondary lithologies: shale, green-gray, calcareous, with thin to nodular limestone, part fossiliferous (Decorah Sh); limestone, wavy-bedded to nodular, part fossiliferous (Decorah-Platteville); dolomite and limestone, slightly argillaceous. Minor: shale partings and thin beds, green-gray to brown-gray, part fossiliferous (Dubuque Fm); shale partings and thin beds, light to dark brown, part organic-rich (Decorah-Platteville); dolomite, sandy to very sandy (Pecatonica Mbr); shale, green-gray, noncalcareous, unfossiliferous, part sandy (Glenwood Sh); thin sandstone to siltstone (Glenwood Sh); dark phosphatic grains (primarily Glenwood, Pecatonica, Decorah); phosphate-pyrite-iron oxide crusts (on some hardground surfaces); pyrite nodules; thin K-bentonite beds (Galena Gp); ironstone ooids (Decorah Sh). Maximum thicknesses total interval: 330 ft (100 m); Galena Group, 250-280 ft (76-85 m); Platteville Formation, 25-55 ft (8-17 m); Glenwood Shale, 3-10 ft (1-3 m).
Lower Cherokee Group in southern, central, and western Iowa includes Kilbourn, Kalo, Floris formations (primarily Atokan-lower Desmoinesian, locally Morrowan at base); Raccoon Creek Group in eastern Iowa includes “Caseyville” and Tradewater formations (primarily Morrowan at most localities; locally includes Atokan-lower Desmoinesian Tradewater Formation in upper part). Primary Lithologies: shale/mudstone, light to dark gray, part silty to sandy; sandstone, very fine to medium grained; siltstone, gray. Secondary Lithologies: carbonaceous shale/mudstone, gray to black; phosphatic black shale; limestone, dense, part fossiliferous, part sandy; coal (beds locally > 2 ft). Minor: sandstone, coarse-grained to granular, part conglomeratic; mudstone, red to pink; limestone concretions (may be septarian); cone-in-cone limestone; siderite/ironstone concretions and pellets; pyrite. Maximum thicknesses Raccoon Creek Group in Muscatine-Scott counties: 230-250 ft (70-75 m). Maximum thicknesses Lower Cherokee Group across outcrop belt: 200-370 ft (60-113 m). Maximum thickness in southwest Iowa subsurface: 650 ft (200 m).
Galena Group (Trenton Limestone), includes Decorah, Dunleith, Wise Lake and Dubuque Formations in northern Illinois.