https://ir.uiowa.edu/igs_ofm/1004/thumbnail.jp

Anderson, Raymond R

Bettis, E Arthur, III

Bunker, Bill J

Giglierano, James D

Howes, Mary R

Ludvigson, Greg A

Witzke, Brian J

English

Iowa Research Online

R6W R5WR7WR8W
T8
2N
T8
3N
T8
4N
T8
5N
T8
6N
Walker Coggon
Prairieburg
Central City
Center Point
Alburnett
Robins
Palo
Springville
Cedar Rapids
Marion
Hiawatha
Bertram
Mount Vernon Lisbon
Fairfax
Ely
Plum
 
River
 
Fault
 
1 0 1 2 3 4 5 6 7 8 9 10 Miles
N
Bedrock Geology of Linn County
1 0 1 2 3 4 5 6 7 8 9 10 Kilometers
1:100000
  SCALE
Pennsylvanian System
Devonian System
Silurian System
Caseyville Fm. + Cherokee Grp. undiff.
Cedar Valley Grp.
Pinicon Ridge Fm.
Otis/Bertram Fms., undiff.
Gower, Scotch Grove and Hopkinton Fms., undiff.
MAP LEGEND
Description of Map Units
Unit Description
Pennsylvanian System
P SHALE AND SANDSTONE (Caseyville Formation and Cherokee Group) -- Soft, dark gray pyritic, carbonaceous shale with interbedded sandstone up to 6 meters
in thickness.  Mantles Devonian and Silurian carbonates on the bedrock surface, and also occurs as paleokarst fills.
Devonian System
Dcv FRACTURED CARBONATE BEDROCK (Cedar Valley Group) -- Fossiliferous gray limestones and dolostones with skeletal lime packstone, wackestone, and
mudstone fabrics, up to 47 meters in thickness.
Dpr FRACTURED CARBONATE BEDROCK (Pinicon Ridge Formation) -- Unfossiliferous limestone, dolostone, and shale.  Includes up to 7.5 meters of light gray to
dark brown sublithographic lime mudstone (Davenport Member), overlying up to 7.5 meters of laminated, porous, dolostone (Spring Grove Member), overlying up
to 6 meters of blue gray sandy calcitic shale with limestone and dolostone interbeds (Kenwood Member).  The Spring Grove Member is a porous, vuggy, unit
contains cavernous openings that yield groundwater to many natural springs.  Active karst is developed in this unit in the Robins area.
Dob FRACTURED CARBONATE BEDROCK (Otis and Bertram formations) -- Unfossiliferous to poorly fossiliferous limestone and dolostone with with mudstone
fabrics.  The Otis consists of up to 15 meters of laminated brown dolostone (Coggon Member) containing the spiriferid brachiopod Emanuella  sp., and is overlain by
limestone and dolostones (Cedar Rapids Member) with sublithographic fenestral lime mudstones fabrics, pelletal fabrics, and oolitic limestone fabrics containing the
spiriferid brachiopod Emanuella  sp.  The Otis overlies the Bertram, which consists of up to 23 meters of brown to gray sublithographic laminated, sandy, intraclastic
dolostone.
Silurian System
S FRACTURED CARBONATE BEDROCK (Gower, Scotch Grove, and Hopkinton formations) -- Fossiliferous dolostones with lime packstone, wackestone, to
mudstone fabrics.  This unit is the principal bedrock aquifer in Linn County.  The Gower ranges from 0 to 30 meters in thickness and is mostly confined to the
southern half of Linn County.  It includes flat-lying laminated unfossiliferous facies (Anamosa Member) and fossilifrous mounded facies (Brady Member).
Underlying the Gower is the Scotch Grove Formation, up to 50 meters in thickness.  The Scotch Grove includes cherty units of sparsely skeletal-moldic dolostone
(Buck Creek Quarry Member),  units of sparsely skeletal-moldic dolostone (Waubeek Member), and mounded facies with abundantly fossiliferous skeletal-moldic
and skeletal-replaced dolostone (Palisades-Kepler Member).  The Hopkinton Formation contains about 40 meters of fossiliferous skeletal-moldic to skeletal-replaced
dolostones.
Geological Survey Bureau
Open File Map Series 95-3
Prepared by
Greg A. Ludvigson
Bill J. Bunker
James D. Giglierano
Mary R. Howes
E. Arthur Bettis III
Brian J. Witzke
Ramond R. Anderson
Energy and Geological Survey Division
Geological Survey Bureau
October 1995
Supported by the U.S. Geological Survey, Department of Interior,
under Assistance Award No. 1434-94-A-1232, and Bluestem Solid Waste Agency, City
of Cedar Rapids City Engineer, Linn County Engineering, Linn County Planning and
Zoning, Linn County Regional Planning, and the cities of Hiawatha and Marion.
Iowa Department of Natural Resources
Larry J. Wilson, Director
ACKNOWLEDGEMENTS
Recognized for direct contributions to the map’s production: M.J. Bounk, D.L. Koch, of the IDNR
Geological Survey Bureau, Iowa City office of the U.S. Geological Survey - Water Resources Division,
Iowa Department of Transportation, U.S. Department of Agriculture - Natural Resources Conservation
Sevice, Linn County Engineering, Bluestem Solid Waste Agency, Linn County Planning and Zoning, R.E.
Novotney Well Drilling Company, and landowners who granted access for field studies.  Special thanks is
extended to Rebecca Palmer, Director of Linn County Planning and Zoning, for coordination with
government agencies in Linn County.


Bedrock geology of Linn County

https://ir.uiowa.edu/cgi/viewcontent.cgi?article=1004&amp;context=igs_ofm

Bedrock geology of Linn County

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