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Bedrock Geology of the Davenport West (Iowa) BEDROCK GEOLOGY OF THE DAVENPORT WEST 7.5’ QUADRANGLE, SCOTT COUNTY, IOWA 7.5' Quadrangle Iowa Geological Survey Open File Map OFM-09-03 90°45'0"W 90°42'30"W 90°40'0"W 90°37'30"W June 2009

prepared by 41°37'30"N 41°37'30"N

Sg Ss Robert McKay, Huaibao Liu, Stephanie Tassier-Surine, and James D. Giglierano

Iowa Geological Survey, Iowa City, Iowa

Sg Dw

Pcc Sg Iowa Department of Natural Resources, Richard A. Leopold, Director Iowa Geological Survey, Robert D. Libra, State Geologist

Dw Supported in part by the U.S. Geological Survey Cooperative Agreement Number 08HQAG0082 National Cooperative Geologic Mapping Program (STATEMAP)

Dw ACKNOWLEDGMENTS

Dw New subsurface geologic data was generated by the University of Iowa students Sarah Byram and Kyle Bracken who produced descriptive logs of water well drill samples. Deborah Quade of Iowa Geological Survey (IGS) lent support with field and office expertise; Murray Perdue (IGS) prepared well samples for stratigraphic logging; Ray Anderson (IGS) provided updated bedrock topography data; Brian Witzke (IGS) provided valued information concerning the and stratigraphy of the area; and

Sg Chris Kahle and Andy Asell (IGS) provided GIS mapping technical help.

Dw Pcc Dw

41°35'0"N 41°35'0"N

Sg

Dw Pcc

Dw LEGEND

CENOZOIC Correlation of Map Units

M S

QUATERNARY SYSTEM E E I T R S MAP E Y S Qu - Undifferentiated unconsolidated sediment Consists of loamy soils developed in loess and glacial (Ma) S Qu UNIT till of variable thickness, and alluvial clay, silt, sand and gravel, with a maximum thickness locally exceeding 60 m (200 ft). Unit shown only on cross-section, not on map. QUATERNARY Qu 2.58 Dw Sg Pcc N

e l Desmoinesian A d SYSTEM I 310 d N i Pcc Pcc A M Atokan V

L ? Dw Pcc – Shale, Siltstone and Sandstone (Cherokee Group and undifferentiated) Lower Y

Dc r S

Pcc and Middle Pennsylvanian. The thickness of this formation may exceed 60 m (200 ft), but in general is less e Pcc N B than 30 m (100 ft). Primary lithologies includes gray shale, siltstone, and minor sandstone. Secondary 315 w N o Morrowan L A lithologies include black carbonaceous shale and coal; , pyrite, and siderite pellets & E

concretions may be present. P

DEVONIAN SYSTEM Dw

N 41°32'30"N 41°32'30"N Dc - Limestone (Cedar Valley Group) Middle Devonian. This map unit includes the Little Cedar A Dc I e Sg l

Dc Formation, and reaches a maximum thickness of 9 m (30 ft). The Little Cedar is composed of fossiliferous 390 N d d O

to sparsely fossiliferous limestone and argillaceous limestone containing a diverse marine fauna including i Dw V

echinoderms, corals, brachiopods and bryozoans; bioturbated fabrics are common. M E

D Dc Pcc 395 Dw - Dolomite, Limestone, Shale, and minor Sandstone (Wapsipinicon Group) Middle Devonian. This Dw map unit includes the Otis and the Pinicon Ridge formations, with a total thickness between 18 and 29 m Pcc (60-95 ft). The Otis Formation is dominated by lithographic to sublithographic, pelletal limestone, with minor dolomite near its base. The Pinicon Ridge Formation is characterized by laminated or brecciated, unfossiliferous limestone and dolomite with minor shale. n a

i Dw w o Dc l SILURIAN SYSTEM d u

L 423 Pcc Sg - Dolomite (Gower Formation) Silurian. Thickness of this formation ranges between 27 and 37 m (90- n a

Sg i 120 ft), and the lithology is dominated by porous dolomite, in part laminated, and vuggy. Brachiopods and k Sg corals are common in mounded facies. c o l

n

D e Ss - Dolomite and minor Chert (Scotch Grove Formation) Lower Silurian. The thickness of this interval N

W A Ss ranges between 35-45 m (120-150 ft), and is characterized by moldic (especially crinoidal) dolomite. 428 I Vugs and pores are common in most part, and minor chert may occur in lower part of the formation. R

D U Ss

L I S

n a D D i D Drill Holes r

Pcc e v o

D Outcrops d

436 n a L

Pcc L Pcc 439

41°30'0"N 41°30'0"N

90°45'0"W 90°42'30"W 90°40'0"W 90°37'30"W

1:24,000 0 0.5 1 2 3 4 Miles

Kilometers Adjacent 7.5' Quadrangles 0 0.5 1 2 3 4 Locator Map

LYON OSCEOLA DICKINSON EMMET WINNEBAGO ± WORTH MITCHELL HOWARD WINNESHIEK ALLAMAKEE

KOSSUTH

SIOUX OBRIEN CLAY PALO ALTO HANCOCK CERRO GORDO CHICKASAW DIXON DONAHUE ELDRIDGE FLOYD

FAYETTE CLAYTON PLYMOUTH HUMBOLDT GEOLOGIC CROSS-SECTION A-B CHEROKEE BUENA VISTA BREMER POCAHONTAS WRIGHT FRANKLIN BUTLER

BLACK HAWK BUCHANAN DELAWARE DUBUQUE WOODBURY WEBSTER IDA SAC Duck Creek Emeis Golf CALHOUN HAMILTON HARDIN GRUNDY 800 I - 280 800 JACKSON A B JONES BENTON LINN Course MONONA CRAWFORD TAMA CARROLL GREENE BOONE STORY MARSHALL

( CLINTON )

f l

e DAVENPORT_E CEDAR e WALCOTT DAVENPORT_W e HARRISON SHELBY AUDUBON Qu GUTHRIE DALLAS POLK JASPER POWESHIEK IOWA JOHNSON SCOTT

v 700 700

t

e

a MUSCATINE

l

E

b POTTAWATTAMIE

CASS ADAIR MADISON WARREN MARION MAHASKA KEOKUK WASHINGTON a n Pcc

l o

e LOUISA

e o

v i

600 v

s 600 t

e MILLS MONTGOMERY ADAMS a UNION CLARKE LUCAS MONROE WAPELLO JEFFERSON

a HENRY

e

Dw t DES MOINES

s v

i v

o

e

e FREMONT o l PAGE TAYLOR RINGGOLD DECATUR WAYNE APPANOOSE DAVIS VAN BUREN

n a LEE

b 500 500 E

l a

e MONTPELIER ANDALUSIA MILAN

Sg t

v e

e e

l f

400 400 ) ( Ss 300 300

Base map from USGS Davenport West 7.5' Digital Raster Graphic (IGS GIS file DRGQ49.TIF) which was scanned from the Davenport West 7.5' Topographic Quadrangle map, published by US Geological Survey in 1991 Topographic contours and land features based on 1986 aerial photography, field checked in 1991 Land elevation contours (10' interval) based on NGVD 1929.

Iowa Geological Survey digital cartographic file DavenportWestquad_bedrock09.mxd, version 6/18/09 (ArcGIS 9.2) Map projection and coordinate system based on Universal Transverse Mercator (UTM) Zone 15, datum NAD83.

The map and cross section are based on interpretations of the best available information at the time of mapping. Map interpretations are not a substitute for detailed site specific studies.