96°30'0"W 96°0'0"W 95°30'0"W 95°0'0"W 94°30'0"W 94°0'0"W 93°30'0"W 93°0'0"W 92°30'0"W 92°0'0"W 91°30'0"W 91°0'0"W 90°30'0"W 90°0'0"W 43°30'0"N EXPLANATION Xs 43°30'0"N M I N N E S O T A New Larchwood Albin BEDROCK Little Spirit Chester Lester Rock Rock Lake Op Op CRETACEOUS Kf Lake iver Og Ce Rapids Park Rake Kd Dc per Iowa R P9 Kf Harris T100N Kd Dolliver Kd Dc Up Cw O Kd Kd Scarville Og Kmt Ocheyedan Orleans Om Og Northwood Dc Op P9 Spirit Superior Cw Kf O Lake Lake Cm Sibley er Lime Om Cj Cj 15 v Dc Kd Dc 26 Manson Impact Structure, Terrace Terrane (breccia) 86 OP i Mills Kd Dc Dw OP GEOLOGIC MAP OP Stacyville Dc Springs 139 R P Kd O o C a Okoboji Kd Buffalo g Om n 182 Armstrong Ledyard Om Carpenter McIntire Dw U o Ce P LYON Swea a p e Kmm O 9 Center pe C Kd 71 OP b r Alvord £¤ Gruver City e I re S George OSCEOLA T99N D o n Dc e 76 Lakota St. w k P r Estherville e n O ve s 9 Thompson i WORTH Cresco a Op Manson Impact Structure, Crater Moat (shaly breccia) i Wahpeton P Dc Ansgar M O R R Arnolds W Joice Lansing Kn k 59 o Dl El S i v c r £¤ Park i Dc k Cree h e n k o 75 iv E e e Cj R West a Kd Om r OF IOWA £¤ e O R k Kd l C c Ashton O EMMET s l M o s t KOSSUTH Kmc Okoboji R e is R c Kensett Riceville s F Leland o d i le h R MITCHELL s tt Kf c Dc 9 si Inwood i e Milford Kd i k k a P p L v O p Doon y D r Terril Wallingford e HOWARD i e e R r s Manson Impact Structure, Central Peak 65 Dc R Mitchell R M £¤ Kd Melvin d o i 218 i Kf in v Kd iv £¤ Dc Dw v (breccia; basement-rock megabreccia) Kd a Ringsted e Kd e Dc e U s WINNEBAGO e Grafton r C 1:500,000 n r Cr R r Dw Decorah r tte ee R DICKINSON Kd iver Bancroft Dc ra Dw O k Manly W n Cw iv T98N Kd Osage e Ridgeway Og Kd e Hanlontown a 52 r 4 Dl p C £¤ s 63 Kn Kf OP 69 r £¤ £¤ 9 i e Dw Og Op OP p e Waukon T i k Iowa Geological and Water Survey Rock Forest n Matlock 15 Dc i Valley L OP City Fertile c Elma Dc Dc Cw i Fostoria o Niobrara Formation (shale) 60 t Creek t k lo n P O l e uffa Hull e B Graettinger re Kd Dl WINNESHIEK Og Open File Map OFM-2010-01 C Woden Crystal Plymouth R Kd S R H B Boyden k Dc o i i c c Dc a Lake k Orchard v i J C Waterville g Dc Kf Sheldon Sanborn o T97N Dl Fenton Titonka r e Cj Kf Kd e r Spillville S Hartley u x Lone Kd ek i R Burt Dw March 2010 o iv Rock Om Harpers er Kd u Rock Protivin Dw Fort Benton Group (shale, chalk) Dc Ferry x Kf Everly Kd Spencer B Falls Alta L Calmar R r Dl Dw ALLAMAKEE e l Dl i D i W a Vista t v v c t Pa i k Dw in e SIOUX Kd le t Ce r C Primary Map Compilation By a Ca Kd reek R t Nora T Kd te Cr Dl Ossian 51 d r ee Clear u OP Kd k L Kd r Kd y m Dickens Springs Og i k o Archer Ruthven Dl t Om Sioux l a Lake e Mason tl Colwell Dc Dc Fort ellow Rive n Y A F y r Center 18 Emmetsburg Ventura 122 122 Dc e 76 Dl OP City OP Rudd R Atkinson P C £¤ Floyd O C iv Brian J. Witzke, Raymond R. Anderson and John P. Pope Dakota and Windrow Formations (sandstone, shale) HANCOCK e e r d North Dc r Castalia Om Primghar e T96N ar Lake a e Dc le k Garner C r Washington Kd 18 Ri Dc K Hospers £¤ Om Britt W ve Postville JURASSIC Cylinder i r Sw Iowa Geological and Water Survey, Iowa City, Iowa Kf Royal Wesley Kd nn 24 Kf CLAY e P Op Og bag o Ri Charles CHICKASAW Lawler O PALO ALTO ve Dl Hawarden Kf Whittemore Dc r City Waucoma Jf O Orange Dl Kd FLOYD Og Luana Og Marquette Kd OBRIEN Ayrshire Algona Rockford Sw Monona 43°0'0"N Kd City CERROB GORDO Bassett T95N e Rodman Kd a Df Ionia New Om Fort Dodge Formation (gypsum, redbeds) 75 Rossie Greenville Gillett Kd v Dw Om Dc £¤ 10 Dl e 18 Hampton Om Sh McGregor 43°0'0"N Ireton P Grove Dl r £¤ Dc O d Kd Dw T E Klemme a Dc Dc Clermont Dl a m Dw Om Des s Alton M t C Sutherland o Corwith Dl r Maurice Granville i F n E Kd W k e Dc e PENNSYLVANIAN Paullina e a e Df s I Curlew k A s s o West t t w R Kd a Swaledale Dc Dw Dc F F Dw Robe Kd i Df Fredericksburg Union rts v Df C West k Mk k R Df 14 Elgin r e Kd e i Rockwell P e D k Pw Chatsworth Kf Calumet Webb r I v O 18 Farmersburg T94N Bend L 17 o e Kd 346 £¤ T Mallard o e P w r OP urke s O Dc Sw y tt a Peterson s Df Kd Kanawha Thornton Dl Dc R Cj M Kd Marble Dc i ve r Iowa Geological and Water Survey 10 C R 107 Df Dc Wabaunsee Group (shale, limestone) Struble P r o Df 12 O Dl e i OP Rock Nashua St. Olaf P Craig e i v Om Dw Dc B O k n Hawkeye Sw e Og u Robert D. Libra, State Geologist 143 e Mk r Df Clayton OP P Bailey 150 c s C Dougherty Sh P Sh k r Goodell Meservey re O Kf a Kd 107 e Ps R i OP k C M i r Om r T93N ve ie e i Linn Sioux Plover 15 r 56 e Kf l Larrabee Lu Verne Kd Sheffield Dc Sw P Iowa Department of Natural Resources r O 128 P k l Grove Rapids O Ottosen C Df Greene Dw Cj e C Marathon r Frederika Om FAYETTE OP r Shawnee Group (limestone, shale) Akron v Kd e Dc e i Kd r Livermore e Randalia Elkader Garnavillo v e Laurens k Richard Leopold, Director i R Marcus e Kd Dl Om Oyens k Mk Dw Om Sh Og R d 10 Kd Sw Sw Fayette Wadena x y 75 OP Plainfield Sw Dc u Brunsville o £¤ Rembrandt Havelock Bode Mk Belmond io l Remsen Mk Pd F Kd 188 93 S Cleghorn Kd Renwick Dc OP Dw k r OP e ig Kf 59 Rolfe Kd Sh Sh e CLAYTON B £¤ WRIGHT r Om B Mk Aredale Shell Sumner t Le Mars 71 Ro C ACKNOWLEDGEMENTS Douglas Group (shale, limestone, sandstone) Kd s 3 £¤ k c Sw sh e P Albert Bradgate e Kd k u Guttenberg Meriden O e r R Dc r Volga Westfield W Hardy Tripoli B City Df C Alexander i Om olga R er v W V Kd e i Mk tt a v Om D r Recognized for significant contributions to the map’s production: Bill T92N e p e s O Clarksville s Dc Dc r Cherokee HUMBOLDT C BUENA VISTA M Dw i Dw Pl Mg o Mk Bristow p Littleport i Latimer e POCAHONTAS ne Ma i Dw J. Bunker, James D. Giglierano, Greg A. Ludvigson, Robert M. s R Allison d n 13 Og Ma Rutland Mg a i Maynard P c Westgate O Garber Kf iv Ma Dumont r Merrill Mk e o Osterdock Kf N Gilmore r Mg McKay, Huaibao P. Liu, and Thomas R. Marshall. Lansing Group (limestone, shale) o Pocahontas Clarion Kd Hansell R Dc Dw n Om Arlington r r Ms Goldfield Rowan i Elkport t Hampton v R e h City e i v Kd r v R Dc i Truesdale Coulter Sh Dw CHEROKEE 3 e a R OP 218 Waverly r Millville North c Humboldt Dakota Kd I £¤ BREMER Supported in part with funding from the U.S. Geological Survey - Pk d Aurelia 4 o Dw r Op y c P Pcl w Df Shell 3 Buena e O o o Mg City a Dl Dc P l O v Alta o Kd BUTLER C Sh PLYMOUTH i Rock 63 Readlyn B Vista National Cooperative Geologic Mapping Program. F T91N Thor Galt R 116 n £¤ Sh Ma Pcl r Oelwein Storm Eagle i P u Kansas City Group (limestone, shale) 7 v O R W a Kd R e ek ux OP Kd r re e c Sh C 169 Kd s s n Sh o Lake i Grove Pcl FRANKLIN ayne t Dw i £¤ Ma M Dl k Sh 12 Kf S v Kmt F Om Strawberry P k e T91N O e e Kd C C Dw l Mg Kmm e 52 tt r C Point £¤ Hinton Li Varina Mg Ms Dows da Denver r 187 Edgewood Og Pb Pioneer Kd Geneva r R r e OP Kd Df iver e e Balltown 140 Kd Mk e k 75 OP k k Dw £¤ Storm Mk e Janesville Fairbank Quimby e Kd Sh M Bronson Group (limestone, shale) Kd Lakeside Palmer r Df Aurora Colesburg Holy Lake Newell k Ms C Stanley Sherrill i Mg e Kingsley Kd Badger Luxemburg s Kmt e Sh Cross s 17 l B e Ss i Mg OP g r 281 Om Om s Kmc o T90N s Ma a Ms C P Hazleton Sh i o O Fonda Dl Dc Sh Lamont p E x Dw Pm Washta 110 T90N 7 Pcl Vincent n Pcl Mk Dc Greeley p Pcl e o Mg B Dc i Sioux OP OP Clare eav Om Sageville Manson Impact L F R i Mg R Popejoy e Dw Dundee Rickardsville za Pcl e r Om Om Durango Op i City r i t Dunkerton k Ss New v Marmaton Group (shale, limestone) d v Woolstock i C k Dc e e Pierson Structure Cre Pcl e h ree New Hartford e r Kf ek Ms r Ma r Vienna Pcl W Mg Aplington Dw Jf Sh C Ss Pomeroy S Parkersburg Ss Dubuque 42°30'0"N o r Sl k Og u 57 e e t P t Dc e O Dw t h Dc r Pcu 376 Galva k Ma Pcl Sh 32 Kd e Ackley 57 C Sh Bankston P 77 P B Mk O O £¤ O Moville Kd e r Stout P Dc 42°30'0"N Holstein Fort y Correctionville r Manson L Pcl O Ss Lawton Schaller i Pcl Alden e T89N za Dodge Mk Df n £¤61 Upper Cherokee Group (shale, 12 Nemaha C Kd 7 r Cedar o Op OP 20 r OP d Dl DELAWARE Dyersville sandstone, limestone) £¤ 20 a Kmm C Falls H Sl Graf Om £¤ Mg d Barnum re Mg Sh BUCHANAN Earlville e ek 926 Webster Williams Iowa 934 Manchester Ss Ss T89N C OP Mg Df OP 63 Dw 129 Mg Jolley Ms Ms City Ms Falls Df 27 £¤ Dc Jesup Sl Winthrop Sl ¨¦§ Duncombe Io OP Evansdale Cushing Early D Jf Ma w Dc Centralia r Ms Independence Pcl 31 Blairsburg a Df Dike Raymond Masonville P e Kd Sou Waterloo Farley Sergeant OP Pcl U th Fk R 20 Delaware l v Io i £¤ u Op i T88N Pcl wa v B Bronson Kd Knierim Moorland Jf e Ss m Bluff Ma Sac City Coalville Mg R r R Kf Elk Run Heights u Lower Cherokee Group and Raccoon Creek Group i Pcl Pcl Mk 150 Dc f Ss C Peosta 20 f Ss r Epworth x Ms £¤ v OP a Om Mg e Wellsburg Hudson l e (shale, sandstone) u Ma Pcl r Owasa o Delhi e Om Sh Ma Pcl C Sl o Anthon Rockwell Ma Dc Sl Dw k i Ms Pcl Mg Dc re T88N S Gilbertville Lytton City Steamboat Df e Otho 58 Dw k e Buckeye P Sh Worthington l Ms B Pcl Rock Dl O Dw t 196 t Sl SAC P r Pcl Holland Sh O u i DUBUQUE N Ms Kamrar Pcl Dl Quasqueton MISSISSIPPIAN s Pcl L Ida Somers St.