LaPorte City Formation

Interval is a northwestern limestone facies that correlates with dolomite strata (upper Hopkinton-lower Scotch Grove formations) to the south and east; locally interfingers with dolomite to south; it overlies progressively higher stratigraphic levels southward within the Hopkinton to Scotch Grove formations. Sl forms highest Silurian unit throughout its extent; unconformably overlain by Dw. Primary lithologies: limestone, dense, fossiliferous, part cherty to very cherty. Secondary lithologies: dolomitic limestone, dolomite. Minor: argillaceous to shaly chert residuum at top (may be basal Dw); shale, green-gray. Maximum thickness, 140 ft (43 m); average thicknesses: 20-60 ft (6-18 m).
State Iowa
Name LaPorte City Formation
Geologic age Lower Silurian, upper Llandovery-lower Wenlock
Lithologic constituents
Sedimentary > Carbonate > Limestone (Bed)dense, fossiliferous, part cherty to very cherty; minor dolomitic limestone
Sedimentary > Carbonate > Dolostone (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed)green-gray
Sedimentary > Chemical > Chert (Bed)argillaceous to shaly chert residuum at top (may be basal Dw)

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 - Buchanan - Delaware - Linn