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Home , Decorah Shale, Geology of Wisconsin, Ice cave, Plateau, Upper Iowa River, Wise Lake Formation

GGroundwaterroundwater IssuesIssues inin tthehe PaleozoicPaleozoic PlateauPlateau A Taste of , a Modicum of , and a Whole Lot of Scenery

Iowa Groundwater Association Field Trip Guidebook No. 1 Geological and Survey Guidebook Series No. 27

Dunning , near Decorah in Winneshiek , Iowa

September 29, 2008

In Conjunction with the 53rd Annual Midwest Ground Water Conference Grand Center, Dubuque, Iowa, September 30 – October 2, 2008

Groundwater Issues in the Plateau A Taste of Karst, a Modicum of Geology, and a Whole Lot of Scenery

Iowa Groundwater Association Field Trip Guidebook No. 1 Iowa Geological and Water Survey Guidebook Series No. 27

In Conjunction with the 53rd Annual Midwest Ground Water Conference Grand River Center, Dubuque, Iowa, September 30 – October 2, 2008

With contributions by M.K. Anderson Robert McKay Iowa DNR-Water Supply Engineering Iowa DNR-Geological and Water Survey

Bruce Blair Jeff Myrom Iowa DNR-Forestry Iowa DNR- Waste

Michael Bounk Eric O’Brien Iowa DNR-Geological and Water Survey Iowa DNR-Geological and Water Survey Karen Osterkamp Lora Friest Iowa DNR-Fisheries Northeast Iowa Resource Conservation and Development Jean C. Prior Iowa DNR-Geological and Water Survey James Hedges James Ranum Natural Resources Conservation Service John Hogeman Winneshiek County Landfi ll Operator Robert Rowden Iowa DNR-Geological and Water Survey Claire Hruby Iowa DNR-Geographic Information Systems Joe Sanfi lippo Iowa DNR-Manchester Field Offi ce Bill Kalishek Gary Siegwarth Iowa DNR-Fisheries Iowa DNR-Fisheries

George E. Knudson Mary Skopec Luther College Iowa DNR-Geological and Water Survey

Bob Libra Stephanie Surine Iowa DNR-Geological and Water Survey Iowa DNR-Geological and Water Survey

Huaibao Liu Paul VanDorpe Iowa DNR-Geological and Water Survey Iowa DNR-Geological and Water Survey

Iowa Department of Natural Resources Richard Leopold, Director September 2008 CONTENTS

INTRODUCTION ...... 1 The Karst Landscape of Northeast Iowa ...... 1 References ...... 1

PALEOZOIC PLATEAU ...... 2 What is the Paleozoic Plateau? ...... 2 Bedrock Geology of Northeast Iowa ...... 2 ...... 3 ...... 5 Siluiran ...... 7 ...... 7 References ...... 7 History of the Paleozoic Plateau ...... 8 Introduction ...... 8 Paleozoic Plateau Region ...... 8 Early Studies of Northeastern Iowa – the “” ...... 9 Quaternary Materials in the Paleozoic Plateau ...... 9 References ...... 11 Karst and Formation and Development on the Paleozoic Plateau ...... 12 Mechanical Karst Formation and Development in Iowa ...... 13 Distribution of Karst in Northeast Iowa ...... 14 References ...... 15

LIVING WITH KARST ...... 16 Sources of Bacteria in Karst...... 16 Tourism and Agriculture ...... 16 Trout Fishing ...... 16 Landfi lls – Solid Waste in Karst ...... 17 Wastewater and Water Quality ...... 19 Animal Feeding Operations in Karst ...... 19 Forestry Planting – Alternative Land Use ...... 20 Pasture-based Dairies – Alternative Land Use ...... 20

GROUNDWATER RESOURCES ...... 20 An Overview of Water Use Permitting in Iowa ...... 20 Authority/Mission ...... 21 Usual Procedures ...... 21

FIELD TRIP STOPS ...... 23

STOP 1...... 25 Guttenberg scenic overlooks ...... 25 South overlook ...... 25 North overlook ...... 25 Development ...... 25

STOP 2...... 29 Allamakee County Park near Rossville ...... 29 Glenwood Cave ...... 29 References ...... 30

STOP 3...... 31 Skyline Quarry – The View from Inside an ...... 31 Decorah Cave ...... 32

STOP 4. LUNCH ...... 33 Dunning Spring Park – The Bottom of an Aquifer ...... 33 Losing Streams ...... 33

STOP 5...... 35 Roberts Creek Sinkhole ...... 35 Results from the Big Spring Basin Water Quality Monitoring and Demonstration Projects ...... 36

STOP 6...... 39 Chicken ...... 39 Drinking Water ...... 39

MAP OF FIELD TRIP STOPS ...... inside back cover

Figure 1. Generalized stratigraphic succession for northeast Iowa and the fi eld trip area (from Hallberg et al., 1983). INTRODUCTION

The Karst Landscape of Northeast Iowa Bob Libra Iowa Department of Natural Resources, Iowa Geological and Water Survey

A variety of geologic factors have produced Water – and any contaminants – enter karst- the karst, shallow , high relief landscape of carbonate via , losing streams, northeast Iowa. First, Paleozoic age carbonate and by infi ltration through the shallow soils ( and dolomite) rocks form the up- in fl at upland areas. The water travels through permost bedrock over much of the area. These cracks and voids to the water , below which carbonate strata are broken into various sized all voids are water-fi lled. The groundwater then “blocks” by vertical fractures and roughly hori- travels “down-fl ow” through the broken rocks zontal bedding planes. As groundwater circulates to springs and seeps along the deeply cut stream through these cracks, it slowly dissolves the rock valleys. These springs and seeps supply much away, creating wide fractures, pipes, voids, and of the stream fl ow in shallow rock areas. The . Second, has removed much of the carbonate aquifers are underlain by less trans- glacial deposits that once covered the landscape, missive rocks, called confi ning beds, which act leaving the carbonate rocks near the surface, as the “bottom seal” of the aquifer. Springs and typically within 25 feet and often within 10 feet. seeps are most prominent where the contact be- When rock that contains voids and openings is tween the aquifer and the underlying confi ning combined with a thin cover of soil, the soil may bed is exposed in valleys. collapse into the rock openings producing sink- Figure 1 is a generalized stratigraphic col- holes. Finally, the proximity of this area to the umn for northeast Iowa, showing the sequence deeply cut has resulted of rocks that underlie the area. The unit called in steep, deep stream valleys. the Galena Limestone is the most karst-affected These solutionally modifi ed karst-carbonate unit. In particular, most of the sinkholes and rocks are excellent aquifers. They are capable of large springs in this area are formed in this unit. transmitting large quantities of groundwater at The unit called the Prairie du Chien Dolomite quite fast rates. However, the presence of sink- is another carbonate unit that exhibits voids and holes allows and any associated dissolved fractures, but few sinkholes. We will contamination to directly enter these rock strata. be referring to the rock column and geologic When sinkholes or enlarged fractures occur in map throughout the trip to keep ourselves geo- stream valleys and other drainage ways, entire graphically and geologically located. streams may disappear into the rock. These streams are called “losing streams.” In addition, References “between the sinkholes,” the thin soil cover pro- vides much less fi ltration of percolating water Hallberg, G.R., Hoyer, B.E., Bettis, E.A., III, and than occurs elsewhere in the state. These factors Libra, R.D., 1983, Hydrogeology, water quality, make the aquifers, and water tapping them, and land management in the Big Spring Basin, very vulnerable to contamination and allow any Clayton County, Iowa: Iowa Geological Survey, contaminants that reach the aquifer to spread Open-File Report 83-3, 191 p. long distances very quickly – especially by groundwater standards.

1 PALEOZOIC PLATEAU entrenched valley of the Mississippi River along the eastern margin of the region. What is the Paleozoic Plateau? When observing limestone and dolomite Jean C. Prior (retired) outcrops, notice the prominent vertical fractures Iowa Department of Natural Resources and crevices as as the numerous horizontal Iowa Geological and Water Survey bedding planes, recesses, and overhangs. These intersecting pathways, occurring at nearly right Iowa has seven major landform regions, and angles, are the primary avenues for infi ltrating Paleozoic Plateau is the name given to the dis- groundwater. The lime-rich strata are slowly sol- tinctive, high-relief in the northeastern uble in the percolating . Through geologic part of the state (Figure 2). This fi eld trip tra- time, this process has given rise to karst fea- verses through parts of Allamakee, Winneshiek, tures such as sinkholes, “disappearing streams,” and Clayton counties and examines the unique caves, and springs as well as an explanation for topography, geology, and hydrology that set the many sharply angled stream courses. These this region apart from the rest of Iowa. Watch carbonate rocks also contain valuable ground- for rugged terrain, steep , abundant water resources for wells throughout the region. rock outcrops, deep narrow valleys, springs, Thus, the karst topography characteristic of this seeps, fast-fl owing streams, and abundant wood- region, with its inseparable surface water and lands as well as broad sweeping views across groundwater interactions, results in a high vul- uniformly rolling summits. These unexpectedly nerability of this area to groundwater contamina- scenic landscapes were dubbed “the Switzerland tion problems. of Iowa” by Samuel Calvin, one of Iowa’s best Understanding the geologic and hydrologic known 19th century geologists. systems at work across and beneath the Paleo- The key to this dramatic difference in the zoic Plateau region is important to meeting the Iowa landscape is the dominance of shallow challenges of landuse, water quality, water sup- sedimentary bedrock at or near the land sur- ply, recreation, and conservation issues in this face. Whereas glacial deposits of various kinds part of Iowa. dominate other regions of the state, they are nearly absent here and more durable and dolomites (carbonate rocks), , Bedrock Geology of Northeast Iowa and shale units control the topography. These Robert M. McKay sedimentary strata, collectively referred to as Iowa Department of Natural Resources Paleozoic in age, include fossiliferous rocks of Iowa Geological and Water Survey Cambrian, Ordovician, , and Devonian age (Figure 3). Their layered sequences vary in The bedrock formations of northeast Iowa resistance to erosion and, as a consequence, dis- are concealed, to varying degrees, by a cover tinct geologic formations can be traced for miles of Quaternary deposits, but the majority of the across the landscape, mirroring the underlying area traversed by this fi eld trip is within the por- bedrock units. Distinctive plateau surfaces are tion of the state referred to by Prior (1991) as developed across the Hopkinton, Galena, and the “Paleozoic Plateau.” This landform region Prairie du Chien dolomites in particular. These is characterized by a thin mantle of Quaternary carbonate units are marked along their edges by materials overlying early Paleozoic bedrock. bold bluffs and escarpments, which produce an Much of this area has traditionally been included angular, stepped skyline all the way from the within the so-called “Driftless Area,” and al- prominent (often wooded) bluff line along the though glacial deposits are largely absent across Silurian at the western border of the this area, the region is not truly “driftless,” as region eastward to the dramatic drop into the scattered erosional outliers of glacial till are not-

2 Figure 2. Landform regions of Iowa. ed in more than a few places. All major streams from older Precambrian structures and basins within this area are incised into bedrock, and ( et al., 1985; Bunker et al., 1988; Witzke the bulk of the Quaternary deposits that conceal and Bunker, 1996). All Paleozoic strata of the bedrock are upland deposits, valley wall region appear to be fl at lying, but actually have a colluvial deposits of mixed loess and bedrock, regional dip to the southwest that varies between and alluvial . 20 to 40 feet per mile. Along some local struc- Figure 4 is an extract of the Bedrock Geol- tures, strata attain slightly higher dips. ogy of Northeast Iowa map (Witzke, et al., 1998; Witzke, 1998) for the area of the fi eld trip. It Cambrian shows the major bedrock units, the fi eld trip route, and signifi cant towns along the route. Cambrian strata are the oldest exposed rocks Figure 1 illustrates the generalized stratigraphic within the region, but these rocks will not be sequence within all of northeast Iowa. Paleozoic seen because they lie to the northeast of the trip strata across this region are deposits primarily route or are buried under thick alluvial depos- of shallow marine origin that accumulated on its of the modern Mississippi River. The most slowly subsiding cratonic basins and shelves and notable of these units is the , along the margins of gentle positive arches. De- a friable, quartzose sandstone of sheet-like pocenters and facies belts shifted through time in distribution approximately 100 feet thick. The response to distant tectonic activity at continen- Jordan forms the lower part of Cambrian-Or- tal margins and lithospheric adjustments dovician aquifer system across eastern Iowa

3 Age Maximum Age Maximum (million years thickness (million years thickness before present) System Rocks Rock-unit names (ft) before present) System Rocks Rock-unit names (ft) 0 359 units (DeForest Fm.) 100 “Maple Mill” cene Holo- (Grassy Creek - 300 0.01 Saverton) Dows Peoria 60/200 374 alluvium 100 0.02 Upper Lime Creek Fm. 300 Glasford Loveland 95 385 Cedar Valley Group 400 0.6 Wolf Creek &

Pleistocene Alburnett fms. 391

(“A & B” tills), 400 DEVONIAN unnamed alluv. Middle Wapsipinicon Group 180 QUATERNARY 397 1.3 L unnamed 100 416 1.7 U “C-tills” & 80 423 Gower Fm. 150 unnamed alluv. 2.5

Pliocene Scotch Grove Fm. 428 300 5 Unnamed (“salt & pepper”) 200 Hopkinton Fm. 13 Lower 160 L-M SILURIAN Blanding - Mosalem TERTIARY 160 65 fms. 443 Maquoketa Fm. 350 74 Manson Impact 10,000 290 Niobrara Fm. 50 Upper 83 455 80

Upper Platteville Fm. 91 461 St. Peter - Glenwood Fort Benton Group 265 fms. 450

95 Mid. 472 Dakota Fm. 500 ORDOVICIAN Prairie du Chien Group 650 Lower 102 488 Jordan Sandstone 130 Lower 142 St. Lawrence Fm. 240 Lone Rock Fm. 180 160 Fort Dodge Fm. 75 g

Upper Wonewoc Fm. 150

JUR- g Eau Claire Fm. 250 206 ASSIC 501 TRI- Mt. Simon Sandstone 1400 CAMBRIAN ASSIC L-M 251 not present in Iowa 542 PERM- unnamed 800 IAN 900 299 “red 25,000 Keweenawan clastics” Wabaunsee Group 320 1050 Supergroup volcanics 40,000 Shawnee Group 220 1100 1280 mafic intrusives Douglas &

Upper Lansing groups 200 , Kansas City Group 140 1480 rhyolites, metamorphics Bronson Group 120 1640 306 Sioux 500 Marmaton Group 200 PROTEROZOIC 1760

1800 PRECAMBRIAN granites, ,

Middle Cherokee Group 750

PENNSYLVANIAN metavolcanics 312 2100 Caseyville Fm. 85 2500 Lower 318 gneisses, mafics, iron formation Pella Fm. 75 2910 Upper 327 “St. Louis” Fm. 160 KEY 340 sandstone, igneous- Warsaw - Keokuk fms. 200 sand metamorphic Middle siltstone, gypsum, anhydrite Burling- 140 silt g Gilmore ton Fm. 350 City Fm. shale, coal mudstone 160

MISSISSIPPIAN limestone Maynes Creek Fm. 150 oolite Lower “North Gp.” 120 dolomite g glauconite 359 diamicton breccia (glacial till)

Printed on recycled paper Iowa Department of Natural Resources Geological Survey 109 Trowbridge Hall Iowa City, Iowa 52242-1319 www.igsb.uiowa.edu

Figure 3. Stratigraphic column of Iowa.

4 Win n e sh ie k Alla m a ke e

DEVONIAN Figure 4. Bedrock Decorah Dc Cedar Valley Group geology of northeast

M Dw Wapsipinicon Group Iowa with fi eld trip

I route and selected

SILURIAN

S

Scotch Grove Fm. towns (adapted from

Ss S

Witzke et al., 1998).

Shb Hopkinton and Blanding Fms.

Postville I

S Sls Silurian Limestone facies

Clayton

Fa ye tte S ORDOVICIAN

I Om Maquoketa Fm.

P Ogp Galena Group and Platteville Fm.

P

Ops Prairie du Chien Group and I St. Peter Sandstone Elkader CAMBRIAN Cjl Jordan, St. Lawrence, and Lone Rock Fms. Garnavillo Cw Wonewoc and Eau Claire Fms. Guttenberg R Field Trip Route I V E R

Buchanan De la wa re Dub uq ue

Dubuque

and surrounding states. Many communities and Skakopee Formation, averaging 100 feet thick, commercial entities draw their primary source of is the upper division of the Prairie du Chien water from “Jordan” wells. Group and lies disconformably on the Oneota. Its basal member, the quartzose New Richmond Ordovician or Root Valley Sandstone, grades upward into the shallow-water carbonates of the Willow The Ordovician Prairie du Chien Group, River Member which contains distinctive beds above the Jordan, comprises the middle unit of of oolites and stromatilites. The trip will pass a the Cambrian-Ordovician aquifer. The Oneota roadcut of large, meter-scale stromatolites, along Formation, the lower subdivision of the Prairie Allamakee County X26 after crossing the du Chien Group, is a dense to vuggy, cherty do- Yellow River before Stop 2. lomite that averages 200 feet thick. It consists of The uppermost unit of the Cambrian-Ordovi- numerous stacked cycles of shallow subtidal to cian aquifer is the well-known St. Peter Sand- peritidal carbonate rock. Some zones within the stone, a friable, high-purity, fi ne- to medium- Oneota exhibit enhanced porosity of meter-scale grained quartz sandstone that averages 50 feet vugs and pores which almost certainly contrib- in thickness. The St. Peter rests unconformably ute to water availability in many wells. Locally, on older Ordovician and Cambrian strata across the formation hosts small occurrences of Upper the upper Midwest and locally thick sequences Mississippi Valley type lead mineralization. The of St. Peter, exceeding 250 feet in thickness,

5 fi ll paleovalleys on this erosion surface. Com- in Decorah along the south side of State High- munity and commercial wells typically case-off way 9 as the trip leaves Decorah. the unit to prevent production of fi ne sand, how- The Galena Group is a resistant carbonate ever, many domestic wells in the region utilize interval that is well displayed in the Ordovician the St. Peter as their primary aquifer. Although outcrop of northeast Iowa. It forms prominent the trip will not stop at any St. Peter outcrop, vertical outcrops along stream courses and the formation is visible in the valley wall of the stands well in roadcuts such as that at Stop 1. Mississippi on the northwest side of Guttenberg, The bulk of the Galena Group is comprised in and again south of the crossing of the Yellow ascending order of three formations: the Dun- River along X26, and fi nally along Winneshiek leith, the Wise , and the Dubuque. The County Road A52 east of Decorah. The St. Peter Dunleith averages 135 feet thick, the Wise Lake is currently mined along the Mississippi River 65 feet, and the Dubuque 35 feet, for a combined at Clayton, Clayton County and shipped to the aquifer thickness of 235 feet that is remark- southern U.S. for use as a propping agent sand in ably consistent across the area. In the Dubuque the oilfi elds when hydraulic fractures need to be area these formations are composed primarily propped open. of dolomite, but north of Dubuque County the The overlies the St. sequence becomes dominated by limestone, and Peter everywhere and is an unusually thin, but this is the area of karst that the Galena Group highly distinctive green to gray, variably phos- is so well known for. In general the Dunleith is phatic and sandy, shale unit. It averages 4 to variably cherty and chert is one characteristic 8 feet thick and forms the lowermost division that is used to divide the Dunleith from the over- of an informal confi ning unit comprised of the lying Wise Lake; the Dunleith is also fossilifer- Glenwood and the overlying Platteville and Dec- ous and contains numerous thin shaly horizons. orah formations. In wet times small water seeps The Wise Lake is mostly chert-free, and often often form at the top of Glenwood outcrops. appears thick-bedded in exposures, a charac- The Platteville Formation, a dense, fossiliferous teristic derived from the extensive bioturbated dolomite and limestone formation, occurs above fabric that typifi es the formation. The Dubuque the Glenwood. It averages 30 to 50 feet in thick- is fossiliferous limestone with notable crinoid ness, being thinner to the north, and is widely skeletal debris. It typically appears as thin to me- quarried for road stone. dium beds separated by thin beds of gray shale. The overlying Decorah Formation forms All the units are jointed or fractured and karst- the upper and most effective division of this solutional features or activity is visible at nearly aquitard. The Decorah is included as the lowest any exposure or quarry. Major joints have been statigraphic division of the Galena Group but is widened by solutional activity and secondary not considered part of the Galena aquifer. It is a carbonate deposits of fl owstone are often com- sparsely to highly fossiliferous unit that averages monly observed (Hallberg et al., 1983). The land 40 feet thick. It is shale-dominant to the north surface above the Galena typically displays sink- at Decorah, its type area, where it is known as hole topography to varying degrees, and some the but is limestone-dominant to areas, such as near Stop 2 in southern Allamakee the south near Guttenberg. The Decorah Shale County, can be characterized as sinkhole . aquitard is a major barrier to groundwater fl ow Stops 2, 3, 4, and 5 will all focus on the Galena from the overlying Galena Group carbonates. Group aquifer and its karst characteristics. Throughout the region, major groundwater The overlies the Ga- springs issue from the base of the overlying Ga- lena Group. It is an Upper Ordovician aquitard lena Group carbonates due to the presence of the characterized by shale and carbonate strata that Decorah Shale. The trip will not stop to see the exhibits considerable north-to-south facies varia- Decorah Shale, but it can be viewed at a quarry tions within the outcrop belt of northeast Iowa

6 (Witzke et al., 1998). In Dubuque County, the termed the “Niagaran” or Silurian Escarpment in Maquoketa is dominated by green-gray shale eastern Iowa, and the trip will inspect the Bland- with subordinate interbeds of dolomite. The low- ing Formation at Stop 6 along the feather edge er interval in this area includes a basal phospho- of the escarpment at “Chicken Ridge.” Silurian rite and brown organic shale facies, locally with dolomite strata of the escarpment host numer- phosphatic dolomites. Signifi cant sub-Silurian ous sinkholes and related mechanical/solutional erosional relief on the Maquoketa shales is seen karst, and some groundwater springs do issue in this area. Northward in the outcrop belt the from Silurian strata along the foot of the escarp- formation incorporates progressively more car- ment. bonate facies, where the Maquoketa can be read- ily subdivided into four constituent members, Devonian ascending: 1) Elgin (limestone/dolomite, vari- ably cherty, shale interbeds, basal phosphorite); Devonian strata of the Wapsipinicon and Ce- 2) Clermont (shale and argillaceous limestone/ dar Valley groups cap the bedrock sequence in dolomite); 3) Fort Atkinson (fossiliferous lime- the western counties of the fi eld trip region. The stone); and 4) Brainard (green-gray shale, dolo- Wapsipinicon Group, averaging 75 feet thick, mite interbeds in upper part). The alternation of lies unconformably above Silurian and Ordovi- resistant carbonates and easily eroded shale seen cian strata and rests as low as the middle por- in the vertical progression of members produces tion of the Maquoketa Formation in Winneshiek a distinctive landscape within the Maquoketa County. It is comprised of a basal Spillville exposure belt. The Maquoketa is capped by Si- Formation composed of thick bedded dolomite lurian strata over much of eastern Iowa, but the and limestone, and an upper division, the Pini- Maquoketa is beveled northward in Winneshiek con Ridge Formation, composed of laminated County beneath the Devonian (Witzke et al., to brecciated limestone and shaly dolomite. The 1998). Although a signifi cant part of the trip will younger Cedar Valley Group attains thickness travel over the Maquoketa Formation there are in excess of 100 feet and is dominated by lami- few exposures. The Maquoketa and its shale- nated to fossiliferous, variably cherty limestone dominated nature forms an effective aquitard and dolomite. above the Galena Group and below the overly- ing Silurian and Devonian carbonates. References

Silurian Bunker, B.J., Ludvigson, G.A., and Witzke, B.J., 1985, The Plum River Fault Zone and the struc- Silurian strata along the fi eld trip route are tural and stratigraphic framework of eastern Iowa: restricted to that of the Tete des Morts, Bland- Iowa Geological Survey, Technical Information ing, and Hopkinton formations. The Blanding Series, no. 13, 126 p. Formation is a distinctive very cherty dolomite Bunker, B.J., Witzke, B.J., Watney, W.L., Ludvigson, interval above the Tete des Morts dolomite. G.A.,1988, Phanerozoic history of the central The Hopkinton Formation, the thickest Silurian midcontinent, : in The Geology formation in the trip area, is widely exposed of , Sedimentary Cover – North in eastern Iowa, and everywhere is known to American Craton: U.S., Geological Society of overlie the Blanding. The Hopkinton consists of America, v. D2, p. 243-260. variably fossiliferous dolomite of differing tex- Hallberg, G.R., Hoyer, B.E., Bettis, E.A., III, and tures and is variably cherty. The aggregate thick- Libra, R.D., 1983, Hydrogeology, water quality, ness of these units is approximately 125 feet and land management in the Big Spring Basin, along the trip route. They comprise the bedrock Clayton County, Iowa: Iowa Geological Survey, that forms the prominent physiographic feature Open-File Report 83-3, 191 p.

7 Prior, J.C., 1991, of Iowa: University of Paleozoic Plateau Landform Region Iowa Press, Iowa City, 154 p. Witzke, B.J., and Bunker, B.J., 1996, Relative sea- The Paleozoic Plateau region is characterized level changes during Middle Ordovician through by an abundance of bedrock exposures, deep deposition in the Iowa area, North and narrow valleys, and limited glacial deposits. American Craton, in Witzke, B.J., Ludvigson, The steep slopes, bluffs, abundant rock outcrops, G.A., and Day, J., eds., Paleozoic Sequence Stra- , , sinkholes, springs, and en- tigraphy: Views from the North American Craton: trenched stream valleys form a unique physio- Geological Society of America, Special Paper graphic setting. These characteristics combine to 306, p. 307-330. form an area of many diverse microclimates that Witzke, B.J., Ludvigson, G.A., McKay, R. M., An- support varied fl ora and fauna communities not derson, R. R., Bunker, B. J., Giglierano, J. D., represented elsewhere in the state. The boundar- Pope, J. P., Goettemoeller, A. E., and Slaughter, ies of this landform region are defi ned along the M. K., 1998, Bedrock geology of northeast Iowa, southern and western margins with the change Digital geologic map of Iowa, Phase 2: Northeast from a rugged, dissected, rock-controlled land- Iowa scale 1:250,000; contract completion report scape to that of the gently rolling, lower relief to U.S. Geological Survey for Assistance Award landscapes of the Iowan Surface to the west and No. 1434-HQ-97-AG-01719, August 1998. the Southern Iowa Drift to the south. The Witzke, B.J., 1998, Bedrock Geologic Map of North- Quaternary deposits of the Paleozoic Plateau are east Iowa – text discussion: online at http://www. characterized by loess covered patches of iso- igsb.uiowa.edu/gsbpubs/pdf/OFM-1998-7_txt. lated glacial till and alluvial materials. pdf. The characteristic features of the Paleozoic Plateau are representative of deep dissection by Quaternary History streams through gently inclined Paleozoic rock of the Paleozoic Plateau units with varying resistance to erosion. These Stephanie Surine rocks range in age from 350 to 600 million years Iowa Department of Natural Resources old and include formations from the Devonian, Iowa Geological and Water Survey Silurian, Ordovician, and Cambrian. The rocks dip gently to the southwest, exposing progres- Introduction sively older Paleozoic rock units in the north- east corner of the state. The more resistant rock On this Iowa Groundwater Association spon- types ( and carbonates) form cliffs sored fi eld trip, participants will travel to the and escarpments high on the landscape whereas most unique landform region of Iowa. The fi eld the more easily weatherable shales have gentler trip area is almost entirely within the Paleozoic slopes. This differential weathering creates a Plateau and includes stops in Winneshiek, Alla- landscape refl ecting the local bedrock. Topog- makee, and Clayton counties. Steep-sided cliffs, raphy is also controlled by extensive karst de- bluffs, deeply entrenched stream valleys, and velopment in this area forming caves, sinkholes, karst features are characteristic of this markedly springs, and subsurface caverns. The Mississippi different physiographic region of northeast Iowa. River also infl uenced landscape development, In contrast to other parts of the state, where gla- and its tributary valleys contain well preserved cial cover dominates, the surfi cial character of terraces, older fl oodplain deposit remnants, and this area is bedrock controlled. The Paleozoic entrenched and hanging . All of these Plateau is bordered by the Iowan Surface which features indicate the complexity of the alluvial comprises the western portion of Winneshiek history and river development associated with County and the southernmost edge of Clayton glacial melting and drainage diversions. County.

8 Early Studies of Northeastern Iowa – 1923), a fi eld conference was held, and at its the “Driftless Area” completion researchers generally agreed that the drift east of the Kansan border was in fact The landscape region of northeast Iowa was deposited by a and that the Kansan oc- originally termed the “Driftless Area” due to the curs both in the valleys and on the uplands. Kay scarcity of glacial deposits and the belief that and Apfel (1928) later published Williams’ map this area had never been glaciated. Later stud- showing the locations of upland drift in north- ies indicated this was not the case, and it was eastern Iowa. From then on the area was mapped termed the Paleozoic Plateau (Prior, 1976). The as Nebraskan and no truly driftless area was rec- fi rst geological investigations of northeast Iowa ognized in Iowa. were completed during the 1840s under the di- In 1966, Trowbridge published a summary rection of David Dale Owen (in Calvin, 1894). of previous works and included additional data In 1862, Whitney was the fi rst to document a from his studies of the region. In all, Trowbridge Driftless Area in Iowa, , , documented more than 100 occurrences of gla- and and produced a map depicting this cial drift and determined that these materials region. Chamberlain (1883) and Chamberlain are till and not outwash. Trowbridge’s research and Salisbury (1886) later used Whitney’s des- further supported the idea that areas in northeast ignation in their mapping of the Driftless Area Iowa previously considered “driftless” by re- boundary in Iowa and noted a “pebbly border searchers had been glaciated. of earlier drift” in all except a few townships. The term Driftless Area came into being and Although the researchers recognized this drift as was commonly used as a term to describe the foreign material, they did not believe these ma- region of high relief, heavily dissected, bed- terials had been deposited directly by the ice and rock-controlled landscape of northeastern Iowa. thought they were possibly ice-rafted debris or However, the original area designated as the the result of fl oodwaters. Driftless Area was much smaller than the region Numerous studies and maps were published of rugged topography and associated fl ora and for this region by the Iowa Geological Survey fauna commonly referred to by natural scien- from 1892 through the early 1900s. McGee tists. Therefore, it was incorporated into a much (1891) and Calvin (1894, 1906) recognized up- larger area than initially defi ned and termed the land glacial materials and boulders, but Paleozoic Plateau. Within this larger area, many did not consider them to be “proper” drift. Other remnants of glacial drift are identifi ed, making studies described glacial outwash materials and the terminology “Driftless Area” incorrect. The boulders of non-native origin, but they were not term Paleozoic Plateau is a better description for determined to be directly deposited by . this physiographic region and incorporates the Due to the lack of glacially deposited materials, much larger topographically and ecologically the high relief, and the extensive bedrock expo- similar area referred to by natural scientists and sures, all these investigations led to the conclu- biologists. sion that the northeastern region of Iowa had not been glaciated. Quaternary Materials in the Paleozoic Plateau While working on a Master’s thesis, A. J. Williams documented 80 patches of glacial drift The Paleozoic Plateau region was glaci- in what had previously been called the Drift- ated multiple times during the Pre-Illinoian less Area. Due to the upland position of the drift between 2.2 million and 500,000 years ago. and the differences between these materials Based on work by Hallberg (1980a), it has been and the Kansan drift to the west, he believed determined that two Pre-Illinoian till units are these deposits were Nebraskan in age. Prior to present, the Wolf Creek and the Alburnett for- the completion of his Ph.D. in 1923 (Williams, mations. The younger Wolf Creek Formation

9 cannot be directly dated in northeast Iowa, but on the divides. The Late-Sangamon paleosol based on other studies it is younger than 600 ka, may extend to the Paleozoic bedrock surface and it is estimated to be about 500 ka indicating (Hallberg et al., 1984). the last time glacial ice advanced into this area Although many early studies suggested that (Hallberg and Boellstorff, 1978; Lineback, 1979; the landform features of the Paleozoic Plateau Hallberg, 1980b). Stream erosion and hillslope are very old, more recent research indicates that development since the last glaciation has re- the modern drainage system and dissected land- sulted in the removal of most of the glacial ma- scape of this region occurred during the Pleis- terials, except those high on the divides, and has tocene. The oldest valley remnants are buried produced the dissected landscape we see today by Pre-Illinoian tills and may be middle to early (Hallberg et al., 1984). in age, although the time of incision More recent studies and drilling associated is not well constrained. Evidence is derived from with mapping projects in the Upper studies of the upland stratigraphy and erosion, Watershed indicate that although glacial till is karst systems, fl uvial and terrace deposits of the rarely recognized in outcrop, it is commonly stream valleys, and the dating of . found in drill core at upland locations. Review Knox and Attig (1988) studied the - of existing drilling records shows the same pat- port terrace in the lower Wisconsin River valley, tern of till distribution. Most exposures at lower Wisconsin. Paleomagnetic dating of the Bridge- elevations and slopes near valleys are comprised port terrace sediments indicate that they are of loess derived colluvium over bedrock. It older than 730 ka. The valley would have had is believed that a period of mass erosion oc- to already be entrenched by this time, indicating curred that removed till from slopes and left till a minimum age for these deposits. Therefore, on the uplands. Early researchers didn’t have they believe that the Mississippi River between the benefi t of drilling records and were limited northeast Iowa and southwestern Wisconsin to outcrops leading to the idea of a “Driftless was deeply entrenched by Pre-Illinoian time. Area.” Glacial till thins toward the Mississippi Research summarized in Hallberg and others River and is very limited in extent in Allamakee (1984) suggests that the Mississippi River and County. The majority of Winneshiek County has its tributaries are of middle Pleistocene age (500 till in upland positions and increases in distribu- ka). The major drainage lines were established tion to the west. The western third of the county by Late Sangamon time, however major stream is in the Iowan Surface landform region with incision probably began prior to the Illinoian loamy reworked glacial till at the surface and a (300 ka). The valley thin mantle of eolian silt (loess) and sand. likely originated as an ice-marginal stream dur- Upland surfaces are mantled with 3 to 6 me- ing a Pre-Illinoian ice advance. ters of Wisconsin age Peoria Formation loess The relationship between karst deposits and which has been radiocarbon dated at 25.3 ± Pre-Illinoian tills can also yield information 0.65 ka (Hallberg et al., 1978). The end of loess regarding the landscape evolution of the Paleo- deposition in Iowa is considered to be about 14 zoic Plateau area. Karst ages have been deter- ka (Ruhe, 1969) and these materials often ob- mined by radiometrically dating speleothems. scure the glacial deposits. On the primary stream Fifty speleothems in Minnesota and Iowa have divides, 4 to 6 meters of loess overlies well- been dated (Lively, 1983). A few dates range drained paleosols developed on Pre-Illinoian from 250 ka to greater than 350 ka, but the ma- tills. The paleosols are generally 1 to 2 meters jority of the dates fall into three general group- thick, but locally may be up to 2 to 5 meters ings: 163-100 ka, 60-35 ka, and from 15 ka thick. These thicknesses and other features are to present. growth is episodic and typical of Late-Sangamon paleosols. Yarmouth- partially controlled by climate, and dates provide Sangamon paleosols are only locally preserved minimum ages on major valley downcutting,

10 which lowered the piezometric surface and al- tocene stratigraphy in Iowa. Geological Society lowed speleothem growth in vadose caves. of America- Abstracts with Programs, v. 12, no. During the past 25 ka in the upper Missis- 5, p. 228. sippi River valley, there have been four major Hallberg, G.R., and Boellstorff, J.D., 1978. Strati- episodes of alluvial activity (Knox, 1996). The graphic “confusion” in the region of the type ar- period between 25 ka and 14 ka was character- eas of Kansan and Nebraskan deposits. Geologi- ized by large quantities of bedload cal Society of America- Abstracts with Programs, being transported by a braided stream system. v. 10, no. 6, p.255. This aggradation has been related to outburst Hallberg, G.R., Fenton, T.E., Miller, G.A., and Lute- fl oods from glacial and normal meltwater neger, A.J., 1978. The Iowan erosion surface: discharge from the Wisconsin glacier. An an old story, an important lesson, and some new braided system developed between wrinkles, in Anderson, R.R. (ed.), 42nd Annual 14 ka and 9 ka as large discharges from outlet Tri-State Geological Field Conference, Geology failures of proglacial lakes and sustained low of East-Central Iowa, p. 2-1 to 2-94. sediment fl ows caused major downcutting. Mod- Hallberg, G.R., Bettis, E.A., III, and Prior, J.C., 1984. ern Holocene climate and vegetation systems Geologic overview of the Paleozoic Plateau re- developed from 9 ka to approximately 150 to gion of northeastern Iowa. Iowa Academy of Sci- 200 years before present. The upper Mississippi ence Proceedings, v. 91 (1), p. 3-11. River returned to aggradation as Late Wisconsin Kay, G.F. and Apfel, E.T., 1928. Pre-Illinoian Pleisto- age sediment in tributaries remobilized. Domi- cene geology of Iowa. Iowa Geological Survey, v. nant processes during this period involved minor 34, p. 1-304. downcutting, channel migration, and the develop- Knox, J.C. and Attig, J.W., 1988. Geology of the Pre- ment of fl uvial fans and deltas at the junction of Illinoian sediment in the Bridgeport terrace, lower tributaries. The fourth episode encompasses the Wisconsin River valley, Wisconsin. Journal of time since European settlement when agricultural Geology, v. 96, p. 505-513. land use, channelization, and building have Knox, J.C., 1996. Late Quaternary Upper Mississippi greatly impacted the upper Mississippi River. River alluvial episodes and their signifi cance to the Lower Mississippi River system. Engineering References Geology, v. 45, p. 263-285. Lineback, J.A., 1979. The status of the Illinoian gla- Calvin, S., 1894. Geology of Allamakee County. cial stage. Midwest Friends of the Pleistocene Iowa Geological Survey Annual Report, v. 4, p. 26th Field Conference, Illinois State Geological 35-120. Survey Guidebook 13, p. 69-78. Calvin, S., 1906. Geology of Winneshiek County. Lively, R.S., 1983. A U-Series speleothem growth Iowa Geological Survey Annual Report, v. 16, p. record form southeastern Minnesota. Geological 37-146. Society of America Abstracts with Programs, v. Chamberlain, T.C., 1883. General geology of Wis- 15, no. 4, p. 263. consin. Wisconsin Geological Survey, geology of McGee, W.J., 1891. The Pleistocene history of north- Wisconsin, survey of 1873-1879, v. 1, p. 3-300. eastern Iowa. U.S. Geological Survey, 11th An- Chamberlain, T.C. and Salisbury, R.D., 1886. Pre- nual Report, p. 189-577. liminary paper of the driftless area of the upper Prior, J.C., 1976. A regional guide to Iowa landforms, Mississippi valley. U.S. Geological Survey, 6th Iowa Geological Survey Education Series 3, 16p. Annual Report, p. 199-322. Ruhe, R.V., 1969. Quaternary Landscapes in Iowa, Hallberg, G.R., 1980a. Pleistocene stratigraphy in Iowa State University Press, Ames, 255p. east-central Iowa. Iowa Geological Survey Tech- Trowbridge, A.C., 1966. Glacial drift in the “Driftless nical Information Series 10, 168p. Area” of northeast Iowa. Iowa Geological Survey Hallberg, G.R., 1980b. Status of Pre-Wisconsin Pleis- Report of Investigations 2, 28 p.

11 Whitney, J.D., 1862. Report on the Upper Mississippi time, glacial deposits covered much of the land- lead region, physiogeography and surface geol- scape, and relief was subtle compared to that in ogy. Geology of Wisconsin, v. 1, p. 93-139. the area today. Groundwater levels would have Williams, A.J., 1923. The physiographic history of been fairly high and water fl ow was down head the “Driftless Area” of Iowa. State University of along horizontal bedding planes and vertical Iowa Library, Unpublished Ph.D. Dissertation, fractures. As time progressed, groundwater dis- Iowa City. solved portions of the rock along these zones of high hydraulic conductivity and elliptical-shaped Karst and Cave Formation and conduits began to develop. These fi rst conduits Development on the Paleozoic Plateau developed while completely water fi lled under Michael Bounk phreatic conditions. Sometime before 30,000 Iowa Department of Natural Resources years ago, entrenchment of the Mississippi River Iowa Geological and Water Survey and its major tributary valleys lowered the level of groundwater far below the land surface of In most carbonate rocks, there is relatively upland areas. As the level of the groundwater little intergranular porosity compared to sand- dropped, conduits closer to the land surface stones. For this reason, most water movement became partly air-fi lled and cavern formation through carbonates is along vertical fractures, or continued under vadose conditions. Under these joints, and horizontal bedding planes. As water conditions, water in a conduit is analogous to a moves through these openings, it dissolves some surface stream and it dissolves and mechanically of the confi ning rock, thus enlarging the open- erodes the fl oor of the conduit, forming a can- ings and allowing greater fl ow. This diverts fl ow yon-like vadose trench below the elliptical phre- from smaller adjacent openings and concentrates atic tube. Many spectacular cave formations, fl ow in the larger conduits causing them to in- such as and , form under crease in diameter. vadose conditions as dripstone and fl owstone ac- The overall direction of groundwater fl ow cumulate because of the high carbonate content in carbonate rocks is down-head in response to of the water. Where a vertical conduit enlarged hydrostatic pressure, as it is in a more hydrologi- near the surface and the mantle of glacial or al- cally, more isotropic rock such as sandstone. In luvial deposits collapsed, sinkholes developed. carbonates however, fl ow is concentrated along Occasionally, a surface drainageway was inter- fractures and bedding planes, zones of high hy- cepted by a large sinkhole and a blind valley draulic conductivity or water movement. Thus, developed. When valleys intercepted conduits solutional conduit and cavern development in at the groundwater level, springs formed. As Iowa occurs along those fracture trends which vadose processes operated in the aerated zone, best facilitate down-head movement (Bounk conduit enlargement continued in the phreatic 1983a, 1983b) zone. These processes continue to operate today, The presently active and easily discernible increasing the secondary porosity of the carbon- karst landforms were not the fi rst to develop in ate rocks and allowing for faster groundwater what is now the Paleozoic Plateau. Prior to the fl ow through these aquifers. Pleistocene, other episodes of karstifi cation oc- Water in a sinking stream or entering a curred in carbonate rocks in this area. Most of sinkhole also carries sediment into the conduit this older karst was destroyed by erosion prior to system. As conduits are abandoned, they may and during the advance of Pleistocene glaciers become partly or entirely fi lled with sediment. into this area. The present northeast Iowa karst Many of these plugged passages, remnants of system began to develop after retreat of Pre-Il- earlier cavern systems, are known from explored linoian glaciers from the area approximately sections of northeast Iowa caves. In addition, 500,000 years ago (Hallberg, 1980). At that large blocks occasionally fall from the roof and

12 Cold Water Cave, in northeastern Iowa, is shown in both photos. This cave contains spectacular speleothems, including stalactites, stalagmites, bacon rind (shown in photo below), soda straws, and fl owstone.

sides of caverns forming “breakdown.” Some tions of the original cavern; and 3) tufa, which is passages become blocked with breakdown and deposited at or near springs, and is highly porous are abandoned. In some instances breakdown, due to the presence of plant material (generally plus the downcutting of a surface stream into a moss) incorporated at the time of deposit. cavern, will result in destruction of the cavern and formation of a steep-sided valley at the sur- Mechanical Karst Formation face. Indicators of former cave systems which and Development in Iowa have since been destroyed include: 1) large blocks of breakdown on the valley fl oor; 2) natu- Another type of karst, mechanical karst, de- ral formed from small, uncollapsed sec- velops in massive carbonate units which overlie

13 shale. In this instance, the carbonate/shale con- range from a minimum of a few meters to a tact is lubricated by groundwater, and blocks maximum known length of over 28 kilometers. of the overlying carbonates slide downslope on Generally, the larger caves contain streams and the overlying shale. Often the base of the mov- are said to be hydrologically active. The streams ing rock rotates outward, forming a roofed cave. in these caves emerge at the surface as springs. Slumping of overlying unconsolidated material Springs issuing from the Galena vary in average results in the development of sinkholes which discharge from less than three liters a minute to form in parallel alignment to the nearby bluf- over 75,000 liters a minute, although the ma- fl ine. This type of sinkhole usually occurs within jority occur at the low end of the spectrum. A a few hundred feet of the bluffl ine (Hansel, single spring can also show wide fl uctuations 1976). in discharge throughout the year. An estimated 100-fold increase in fl ow can occur following a Distribution of Karst in Northeast Iowa heavy rain or spring snowmelt. Occasional examples of mechanical karst Karst development includes several types of also are found in the Galena outcrop area. These landforms which result from solution and me- usually are restricted to escarpments along major chanical movement of the carbonate rocks and valleys draining the area. Some of these mechan- from collapse of overlying, unconsolidated de- ical karst features are shaped so as to trap cold posits into solutional and mechanically induced winter air and hold it far into the warmer spring openings. These landforms are not uniformly and summer months. Water descending into distributed across northeast Iowa. Instead, they these areas during the spring freezes and forms are concentrated where lithologic, hydrologic, ice, from which the term, “ice cave” is derived. and geomorphic conditions have promoted their Prior to widespread use of refrigeration, several development and preservation. ice caves, such as Decorah Ice Cave, were used Figure 5 shows the general distribution of by local inhabitants for cold storage. karst features in northeastern Iowa. Two major Karst along the Silurian Escarpment is domi- areas of concentration are readily apparent: nantly mechanical in origin (Hansel, 1976). the outcrop area of the Ordovician-age Galena Here, Silurian strata are underlain by the Ordo- Group, and a zone extending roughly northwest vician-age Maquoketa Shale. Water percolating to southeast along the leading edge of Silurian- through the Silurian carbonates is perched at the age strata in northern Dubuque, southwestern contact with the underlying shale. This lubricat- Clayton, and northeastern Fayette counties. ing action coupled with high relief along the Solutional karst dominates the Galena out- escarpment induces downslope movement of the crop area. Sinkholes are abundant in portions Silurian rocks and development of mechanical of this area, with more then 1,800 recorded in a karst. Some solutional karst is also developed in single township (Ludlow) in southwestern Al- this area, but the known caves and other solution lamakee County (Hallberg and Hoyer, 1982). features are smaller than those formed in the Ga- Sinkholes in northeast Iowa range from about lena outcrop area. two meters in diameter and one-half meter deep to large depressions one hundred meters in di- ameter and in excess of ten meters deep. Blind valleys are also common in this area where high sinkhole concentrations are found. Several caves are known in the Galena outcrop area. These

14 Fayette Clayton

Dubuque

Figure 5. Areas in Iowa with varying levels of karst development and potential.

References Hallberg, G. R., 1980. Pleistocene stratigraphy in Bounk, M. J., 1983a. Some factors infl uencing phre- east-central Iowa. Iowa Geological Survey Tech- atic cave development in the Silurian strata of nical Information Series No. 10, 168 p. Iowa. Proc. Iowa Acad. Sci. 90:19-25. Hallberg, G. R., and Hoyer, B. E., 1982. Sinkholes, Bounk, M. J., 1983b. Karstifi cation of the Silurian hydrogeology, and groundwater quality in north- Escarpment in Fayette County, Northeastern east Iowa. Contract report, Iowa Geological Sur- Iowa. Geological Society of Iowa Guidebook 40, vey, Iowa City, 120 p. 26 p. Hansel, A. K., 1976. Mechanically induced karst Bounk, M. J., and Bettis, E.A., 1984. Karst Devel- development along the Silurian Escarpment in opment in Northeastern Iowa, Iowa. Proc. Iowa northeastern Iowa. Unpublished M.S. thesis, Uni- Acad. Sci. 91:12-15. versity of Northern Iowa, Cedar Falls.

15 LIVING WITH KARST community with a rich heritage that includes hundreds of small livestock and dairy producers Sources of Bacteria in Karst managing hay and pasture on steep, highly erod- Eric O’Brien ible slopes. On the other side of the scale is a Iowa Department of Natural Resources burgeoning recreation and tourism industry that Iowa Geological and Water Survey capitalizes on the beautiful and unique features and found in the rolling of northeast Iowa and the coldwater fi sheries and streams that fl ow Mary Skopec through them. The marriage of these two indus- Iowa Department of Natural Resources tries creates a balanced, diverse economy, but Iowa Geological and Water Survey it also creates an environment for confl ict when one industry tries to dominate the resources or The Upper Iowa River and its watershed are when shifts in one industry negatively impact valuable natural and economic resources located the other. in extreme northeast Iowa and southeast Min- nesota. The Upper Iowa River watershed is a Trout Fishing 1,005-square-mile watershed recognized by the Bill Kalishek, Fisheries U.S. Environmental Protection Agency and the Iowa Department of Natural Resources State of Iowa as a priority watershed for water and quality protection. This river system is heavily Karen Osterkamp, Fisheries utilized for swimming, tubing, and canoeing. Iowa Department of Natural Resources The river has a variety of water quality issues. Some reaches of the river were placed on Iowa’s Trout fi shing is a major economic force in Impaired Waters List in 2004. Concentrations of northeast Iowa. It is estimated that angler expen- the indicator bacteria E. coli exceeded state stan- ditures for all Iowa coldwater trout fi sheries total dards for body contact in recreational waters. $13.9 million per year. The American Sportfi sh- ing Association’s report “Sportfi shing in Ameri- Efforts to lower bacteria levels need information ca” indicated the retail sales related to all fi shing on the source(s) of the bacteria. In the Upper in Iowa was $356 million and total economic Iowa Watershed, this involves knowing where output from these sales was $728 million. the water sources are. The presence of sinkholes All of Iowa’s 105 trout streams are located and losing streams, which may contribute bac- in 10 counties in the northeastern part of the teria-laden runoff to the complex groundwater state. Trout have a water temperature require- system, complicates the question of where the ment that restricts their distribution in Iowa. In bacterial sources are located. Further, in all our general, trout cannot survive in water greater watersheds, there are questions as to the biologi- than 75 degrees. Most Iowa waters will reach cal sources of bacteria. Are they from human maximum summer water temperature of greater waste, livestock manure, or wildlife? than 80 degrees. The only waters that stay cold enough during the summer to support trout are Tourism and Agriculture the spring-fed streams that drain from the karst Lora Friest topography of northeast Iowa. Northeast Iowa Resource Conservation A coldwater trout stream is a very complex and Development (RC&D) natural system. The quality of the stream is af- fected by the underground aquifer that forms the Northeast Iowa communities balance the spring fl ow, the surface watershed that drains economics of agriculture and tourism every day. into the stream, the land use immediately along On one side of the scale is a strong agricultural the stream, and the physical characteristics in the

16 Livestock is one of the many potential sources of E. coli bacteria in Iowa streams.

stream itself. High-quality trout streams result Landfi lls – Solid Waste in Karst from successful partnerships between private Jeff Myrom, Solid Waste landowners and conservation agencies in the Iowa Department of Natural Resources management of these natural resources. and During rainfall events, sinkhole-driven water John Hogeman source can be contaminated by heavy silt loads Winneshiek County Landfi ll Operator and high concentrations of nitrogen gas. These and runoff events cause severe fi sh mortality and Joe Sanfi lippo health problems, and fi sh production and effi - Manchester Field Offi ce ciency are greatly impacted. Problems with fi sh Iowa Department of Natural Resources health are still directly related to runoff events and and necessitate costly treatments to minimize Bob Libra disease outbreaks. It is apparent that additional Iowa Department of Natural Resources improvements in the watershed will have a posi- Iowa Geological and Water Survey tive impact on fi sh health. and Bill Kalishek, Fisheries Iowa Department of Natural Resources

The Iowa Department of Natural Resources regulates landfi lls through the solid waste pro- gram. Landfi lls are tracked from the initial site

17 selection through approval of the engineer’s site will be monitored include methane gas produc- plans, construction of base works, day-to-day tion, settlement, groundwater, storm water run- operations, fi nal closure, and the 30-year post- off, leachate, fencing, vegetation, building main- closure monitoring and maintenance. tenance, and erosion. Closure and post-closure The DNR’s Solid Waste Section gives initial costs at this site are included in the tipping fee site approval, approves plans, and monitors re- that the current landfi ll customers are paying. ports that the landfi ll operators and responsible Groundwater monitoring is required at all offi cials are required to submit. The reports Municipal Solid Waste Landfi lls. Monitoring include water monitoring, gas monitoring, and wells are placed and designed based on the engineer inspections. “hydrogeologic investigation” that was done The DNR’s Field Offi ce located in Manches- for each landfi ll. A range of parameters are ter inspects the site on a periodic basis for com- measured depending upon well position and pliance with the solid waste regulations and to site history. In 2004, a review of annual moni- offer operator assistance. The Field Offi ce also toring reports from landfi lls was conducted by maintains a working relationship with the land- the DNR-Solid Waste and Geological Survey fi ll personnel so they are aware that assistance staff. At that time, there were 14 monitoring from the DNR is available. The Field Offi ce also wells in use at the Winneshiek landfi ll. Wells works closely with the Solid Waste Section to monitor both the “top of the water table” within insure that any concerns noted in any of the re- the unconsolidated deposits, and groundwater ports are properly addressed. from the underlying bedrock. Two locations on Although not a stop on this trip, the Win- Trout River are also monitored, as the stream neshiek County landfi ll lies within a few miles passes close to the landfi ll and loses water into of some of the most karst-affected areas in the the Galena Limestone downstream to the north. state. How can a landfi ll be in such a setting? While some monitoring wells have detected Relatively subtle changes in the underlying geol- indications of landfi ll leachate in the shallow ogy occur in the landfi ll area. Here, more slowly geologic materials, concentrations have not been permeable shale and shaley carbonate rocks of signifi cantly above background, and no upward the Maquoketa Formation overlie the Galena trends were visually identifi ed in the monitoring Limestone. The Maquoketa rocks are less prone data. The review included a recommendation for to fracturing and karst formation, although the better monitoring of the deeper zones, given the lowermost part of the formation does exhibit relatively vulnerable nature of the underlying some sinkholes. Also, there is a somewhat great- aquifers. Stream sampling has shown minor con- er thickness of glacial deposits. Taken together, tamination in Trout River. The landfi ll operates these deposits provide suitable materials for the a leachate control/recirculation system which is landfi ll cells. likely helping to limit leachate movement. The Winneshiek County Sanitary Landfi ll is Trout River is a small coldwater stream a regional landfi ll serving the counties of Win- that originates 2 miles south of the Winneshiek neshiek, Howard, and Clayton, the municipality County landfi ll. As the stream fl ows north to- of Postville, and Fillmore County in Minnesota. ward its confl uence with the Upper Iowa River, The population served by the Winneshiek Coun- it is adjacent to the east edge of the landfi ll site. ty Sanitary Landfi ll is approximately 63,000. Downstream of the landfi ll Trout River is a It is estimated that the remaining life of this losing stream and goes completely dry in one landfi ll is 11 years (2019). When the landfi ll is segment during most summers. This stream has closed the Winneshiek County Area Solid Waste been stocked with four-inch fi ngerling brook Agency is required to monitor and maintain the trout yearly since 2000. Brook trout are the trout site for the following 30 years. The items that that are native to Iowa and the trout species that

18 is the most intolerant of warm water tempera- Animal Feeding Operations in Karst tures and pollution. These trout have survived Claire Hruby and fl ourished in the section of Trout River on Geographic Information Systems the landfi ll property. Recent fi shery surveys have Iowa Department of Natural Resources shown good numbers of brook trout present with fi sh up to 14 inches in length. In the case of the Winneshiek County Landfi ll, a managed brook Within the outcrop belt of the Galena Lime- trout stream and a landfi ll are compatible uses stone, the Allamakee County Soil Survey shows for the same piece of property. more than 1,000 sinkholes in one 36-square-mile township, or about one mapped sinkhole every Wastewater and Water Quality 20 acres. The sinkholes here aren’t all mapped; Joe Sanfi lippo in places the soil survey stopped trying to map Manchester Field Offi ce individual sinkholes and created a soil mapping Iowa Department of Natural Resources unit that is described as containing “sinkholes too numerous to map.” Iowa has a little over 1,500 facilities covered Senate File 2293 banned confi nement struc- under individual “National Pollutant Discharge tures within 1,000 feet of “known” sinkholes. Elimination System” (NPDES) permits. Of Much of the soil mapping was carried out 20 or those, about 800 are municipal facilities, 365 more years ago. DNR’s Geological and Water are industrial facilities, 280 are semi-public fa- Survey, the Northeast Iowa RC&D, and other cilities (such as mobile home parks), and there partners are mapping sinkholes in the area to are about 80 other miscellaneous facilities with improve and update our knowledge of their loca- permits (water treatment plants, land application tions and characteristics. facilities, and industrial stormwater). In addition, In Ludlow Township, Allamakee County, and there are three stormwater general permits that adjacent areas, over 75% of the land is within cover a total of more than 6,000 active sites, and 1,000 feet of known sinkholes. Sinkholes are one general permit for over 400 rock and sand- present within 200 feet of certain farm’s animal and-gravel operations. feeding operation (AFO) structures. The Department of Natural Resources The Prairie du Chien dolomite forms an im- regulates wastewater facilities through the Na- portant statewide aquifer. Wells as far southwest tional Pollution Discharge Elimination System as the Des Moines area are drilled into the Prai- (NPDES) permitting and inspection process. rie du Chien and the underlying Jordan Sand- Plans for wastewater plants, beginning with stone, where these rocks lie more than 1,500 feet site location separation distances, were submit- below the surface. The Prairie du Chien typically ted to the department and separation distances exhibits solutionally enlarged openings, but were verifi ed in the fi eld. The fi nal plans were rarely sinkholes. The number of Prairie du Chien reviewed and approved by DNR engineers prior sinkholes mapped by the county soil survey are to construction. Plants will be monitored by the miniscule compared to those mapped on the Ga- owners, who will operate the plant and submit lena Limestone. However, subsurface voids do periodic reports to the department. The plant will occur in the Prairie du Chien, even though there also be monitored by the DNR’s Field Offi ce in are no sinkholes to help indicate their presence. Manchester which will conduct periodic inspec- Unanticipated voids found to be present affect tions of the plant, monitor the receiving streams, manure operators in this area. and respond to concerns from the public.

19 Forestry Planting – Alternative Land Use face runoff. On a 10% slope, a 3-inch rain in 90 Bruce Blair, Forestry minutes will only have 10% runoff vs. 50% to Iowa Department of Natural Resources 60% for cropland or overgrazed pastures. The reduced runoff decreases the chance of nutri- The wood products industry in northeast ents and pesticides reaching sinkholes. Another Iowa is booming. The region’s climate and great water quality advantage is the reduced amount soils combine to produce some of the highest of fertilizers and pesticides applied to the land. quality fi ne hardwoods in the world. Buyers A 100-cow dairy would have 100 acres of pas- travel from all over to northeast Iowa because ture receiving 0 to 100 lbs/acre of nitrogen and we are viewed as growing some of the best qual- minimal phosphorus compared to row crop that ity black walnut anywhere. In a recent timber would be heavily fertilized. Pesticides are only harvest in Delaware County, a 2.5 acre stand spot applied as needed, as opposed to broadcast of red oak, white oak, and black walnut sold applications for cropland. Another advantage for $29,200. The 140-year-old trees were quite can be the reduced amount of manure storage large, but were otherwise of typical quality for needed. Seasonal systems can have the cows on the area. The stand went virtually unmanaged pasture from seven to twelve months spreading from the time squirrels planted the seeds. The their own manure. Cropland can be converted stand averaged $83.43 of net return per acre per to long-term pasture for less than $100 per acre year with very small input costs including no making this system the most cost effective meth- property taxes. od of erosion control. The water quality benefi ts from timber pro- The local community receives considerable duction are obvious when compared with row economic benefi ts from dairies, and new opera- crop production. Storm runoff is minimal with tions should be a priority. Grass-based systems most of the rain being intercepted by the forest are a viable entry avenue for beginning farmers. canopy and absorbed in the soil. Pollution from Two hundred acres could support a 100-cow pesticides and nutrients is a tiny fraction of that dairy. Low costs and labor effi ciency are the from row crop production. Woodlands also pro- keys to success. An effi cient milking parlor is es- vide clean air, wildlife habitat, carbon storage, sential and should be considered as a cost share- and recreation. Timber production in northeast able practice in the same manner as a manure Iowa is a terrifi c conservation alternative. Policy storage structure. makers and natural resource agencies should promote timber production on our most highly GROUNDWATER RESOURCES erodible farm ground. An Overview of Water Use Permitting Pasture-based Dairies – in Iowa Alternative Land Use M. K. Anderson James Ranum Water Supply Engineering Section Natural Resources Conservation Service Iowa Department of Natural Resources

A pasture-based dairy will have around one In order to obtain and use groundwater acre of intensively managed pasture per cow. in Iowa, state law requires a water allocation They may have another half-acre of hay where permit. This is required by municipalities, in- they take one or two cuttings, then graze. They dustries, agricultural and golf course irrigators, may purchase their stored feed, creating a mar- farms, agribusinesses, and any other user of over ket for other producers. These well managed 25,000 gallons of water per day. These permits pastures will be a dense sward which practically are required under Iowa laws that originated eliminates and greatly reduces sur- during the droughts of the 1950s. The stated

20 purpose of the law is to “...assure that the water methods of water use are prevented. resources of the state be put to benefi cial use to 3. Water conservation is expected. the fullest extent possible, that the waste or un- 4. Established average minimum instream fl ows reasonable use, or unreasonable methods of use are protected. of water be prevented, and that the conservation and protection of water resources be required Usual Procedures with the view to their reasonable and benefi cial use of the people.” Application for a water use permit is made on The law requires permitting the use of all wa- a 6-page form supplied by the Iowa DNR, last ter in quantities over 25,000 gallons per day. It updated in 2005 and available on our web-site. applies to the use of water from streams and res- The completed forms must be accompanied by ervoirs, gravel pits, quarries, and other sources. a $25 fee and a map showing the location of the The injection of water into the ground, for dis- proposed well must be returned to the DNR. The posal of water used in heat pumps, or for other location of the land upon which the water is to purposes, is also regulated, but in practice, this is be used must also be shown on the map. The ap- done by EPA. plicant should include a description of the exact The term of these permits is 10 years; in manner in which they intend to use the water for some circumstances, they are issued for a shorter which a permit is requested. period. When DNR receives an application, it is initially screened to determine whether there is Authority/Mission suffi cient information provided to process the application. In the case of groundwater, the Iowa The authority for regulating water allocation Administrative Code requires that available arises from the mission the State has to protect hydrogeological information be reviewed to de- public health and welfare. The use of water by termine what, if any, further information the ap- one person can affect other nearby water users plicant must provide. The IAC specifi cally states and the general public. Iowa’s water allocation that additional information, over and above that program attempts to sort through various com- requested by the application form, may be re- peting uses, by doing the following: quired. The application is not complete without this additional information; the applicant must 1. An administrative procedure to resolve water supply it in order to obtain the water-use permit. use confl icts. If DNR is unable to identify the aquifer from 2. A permitting program to ensure consistency in which withdrawals are proposed, the applicant decisions on the use of water. is required to assist in determining this. They’re 3. Provisions for public involvement in issuing further required to provide information that will water allocation permits and in general estab- assist DNR to predict the effects of the with- lishing water-use policies. drawals upon the aquifer and upon neighboring water supplies. DNR may require a survey of All waters, surface and groundwater, are surrounding wells (usually within 1-2 mile radi- “public waters and public wealth” of Iowa citi- us), to determine the probability of serious well zens. Iowa statute provides an allocation system interference problems. based on the concept of “benefi cial use.” The Water-quality data, if available, though not key points are: specifi cally mentioned in the rules, is helpful in determining the aquifer that is being tapped. It 1. Water resources are to be put to benefi cial use should be supplied by the applicant if it is avail- to the fullest extent of which they’re capable. able and may be requested by DNR. In practice, 2. Waste, unreasonable use, and unreasonable DNR relies heavily on the expertise of the Iowa

21 Geological and Water Survey (IGWS) in Iowa City to evaluate data in ambiguous cases. Test drilling may be required, and if done, the well logs must be submitted to IGWS in Iowa City. Yield tests may be needed, and even controlled aquifer tests using the formal Theis method are on occasion necessary. These are done under the supervision of a registered well driller or a licensed professional engineer. DNR may require monitoring well installation for the aquifer test. For wells in a karst-type hydrogeologic set- ting, special procedures are suggested. Where possible, the Department will ask the applicant to conduct some form of hydrogeologic map- ping. Hydrogeologic mapping has a high degree of accuracy and produces an easily defensible wellhead protection area. This method maps physical fl ow boundaries using a combination of geologic, geomorphic, and geophysical methods. To determine the appropriate fl ow boundaries, studies of the aquifer are undertaken to iden- tify varying rock characteristics, the extent and Community water tower in Colesburg, Iowa. thickness of unconfi ned aquifers, groundwater drainage divides, and groundwater and surface water basin delineation. for the inclusion of non-standard permit condi- This method can be used to delineate well- tions are indicated in the summary report. head protection aquifers whose fl ow boundaries Upon completion of the summary report, are close to the surface, such as glacial and al- DNR publishes a notice of its intent to award a luvial aquifers and those aquifers exhibiting dif- permit. The Iowa Administrative Code allows 20 ferent physical properties in different directions, days for the public to request a copy of the sum- such as fractured bedrock and karst. This delin- mary report and to submit comments. The com- eation technique requires technical expertise in ment period may be extended for cause. the geological sciences. Hydrogeologic mapping At the end of the notice period, DNR consid- may prove expensive if suffi cient hydrogeologic ers all comments and if necessary revises the data does not exist and fi eld investigations are summary report. The initial decision is then necessary. New karst wells will, however, re- issued, as either a Water Use Permit or a disap- quire hydrogeologic mapping with associated proval of the application. Complete disapprovals fi eld verifi cation before a fi nal permit is issued. are very rare. In many cases, though, special After all the necessary supporting informa- conditions are included in the permit. In oth- tion is received, a summary report of the appli- ers, the rates of withdrawal, and the total annual cation is written containing recommendations to amount of withdrawals, may be reduced from award or deny the permit. It describes the hydro- the rates and amounts requested to facilitate wise geologic context of the proposed withdrawal, the and benefi cial use of the water resource. Copies anticipated effects of the proposed withdrawals of the initial decision are mailed to the applicant, of groundwater, and indicates whether verifi ed all who provided comments, and any others who well interference has been found. The reasons request a copy.

22 FIELD TRIP STOPS (See inside back cover for map of Field Trip Stops.)

23 24 STOP 1.

Guttenberg scenic overlooks

There are two Mississippi River scenic over- looks at Guttenberg: south and north. The south overlook, while stratigraphically important, will be bypassed on this trip because the focus of this trip is karst-related issues. Besides which, we’re on a tight schedule!

South overlook from Delgado, David J., ed., Ordovician Galena Group of the Upper Mississippi Valley – Deposi- tion, Diagenesis, and Paleoecology, Guidebook for the 13th Annual Field Conference September 30 – October 2, 1983, Great Lakes Section Soci- ety of Economic Paleontologists and Mineralo- gists, Stop 3, p. R16 – R27. Scenic overlook of the Mississippi River at “This magnifi cent road cut, constructed in Guttenberg. 1975, is the most nearly complete exposure of the Galena Group. Parts of the Decorah and in base level, which, of course, affected solu- Dubuque formations, and the entire Dunleith tional karst and cave development across the Pa- and Wise Lake formations are exposed without leozoic Plateau. So enjoy the view of the mighty break, with road level access to the Dunleith “Ole Man River,” ‘cause he’s had a profound and lower Wise Lake. Upper Wise Lake and infl uence on what you’re going to see today. Dubuque strata must be reached with ladders but can be examined by intrepid sedimentologists Additional information about this area: with suffi cient motivation. This cut illustrates most of the characteristics and sedimentological Sinkhole Development problems associated with the Galena Group.” Bob Libra Iowa Department of Natural Resources North overlook Iowa Geological and Water Survey Paul VanDorpe Iowa Department of Natural Resources Percolating soil water is typically acidic Iowa Geological and Water Survey and therefore can dissolve carbonate rocks such as limestone. When near surface fractures While enjoying the colorful view of , and cracks are dissolved into larger voids, the sloughs, and Mississippi River vehicular traf- overlying glacial soils may no longer have the fi c, keep in mind that you’re looking at the top strength to bridge the void and will slowly begin of about 350 feet of alluvium. That amount of to slump downward. The process of dissolving down-cutting, below the river level you see be- out voids takes thousands to tens of thousands fore you, is approximately the same as the dis- of years. The failure of surface soils over the tance from the river level to where we’re stand- void is a much shorter process. It can occur over ing, perhaps a bit more. That’s a lot of missing months to years, or it can occur instantaneously. rock! Accompanying down-cutting are changes Figure 1-1 is a schematic depiction of sinkhole

25 Figure 1-1. Diagram showing steps in sinkhole formation.

formation. Saturated glacial soils will collapse simple design than the city had planned on, but into voids more readily than dry soils. They can it was a retrofi t that would work. fl ow and ooze into relatively small openings. For In the more typical setting in the countryside, this reason, seepage from earthen structures such when a sinkhole forms, it becomes the new low as and farm may accelerate col- spot on the ground. Runoff will fl ow downhill lapse, as the seepage keeps the underlying soils into the sinkhole, and typically cause headward permanently saturated. This was the unfortunate erosion and the establishment of a drainage way case of the Garnavillo sewage in Clayton leading to the sink. Eventually the sinkhole may County in the early 1980s. form its own watershed. Other sinkholes form in The Garnavillo lagoon system was built as streams beds and are referred to more commonly a passive three-cell system, a design easy for as stream sinks or just as a losing stream point. the small community to maintain and operate. These sinkholes come with their own watershed. The lagoon cell shown in Figure 1-2 was built Since sinkholes take surface drainage, they into a hillside, with the fl oor of the lagoon cut receive inputs of sediment as well. Often, they to within 5 feet of the Galena Limestone. As the will become “plugged” with sediment, and have lagoon system was approaching completion, no obvious opening. However, since they will stormwater was directed into this cell to test the continue to receive drainage, they will often plug seal of the liner, fi lling the cell to roughly a 1-2 and unplug repeatedly. This can happen on time- foot depth. This occurred on a Friday afternoon. scales of months, years, or decades. Sinkholes By Monday morning, a sinkhole had formed and have been known to “form” and expose decades- the lagoon was dry (Figures 1-2 and 1-3). Over old farm equipment that was dumped in a former the coming months, a line of small depressions sinkhole, at that location, in the past. formed in the cell. Ultimately, this cell and a Along with sediment, sinkholes may receive second were abandoned. The third cell, which runoff containing relatively high levels of herbi- overlies a thicker cover of glacial materials, was cides, phosphorus, bacteria, ammonia nitrogen, converted to an aerated system. This was a less and organic matter. This water is delivered into

26 Figure 1-2. City of Garnavillo lagoon after sinkhole failure.

Figure 1-3. Close-up of sinkhole at City of Garnavillo lagoon.

the groundwater system with little or no fi ltra- cans have been disposed of in sinkholes in the tion and may travel quickly through the frac- past. While this practice is no longer as common tured and karsted rocks. The water may impact as it used to be, some dumping still occurs. The wells or recharge the coldwater streams found in Groundwater Protection Act of 1987 provided the valleys below. funds for a number of sinkhole cleanups. As you As suggested above, sinkholes are far too can imagine, removing large quantities of trash convenient locations for waste disposal. Trash, and old equipment, mixed with sediment and old equipment, white goods, cars, and pesticide rock, is not an easy or inexpensive task.

27 28 STOP 2.

Allamakee County Park near Rossville

The Rossville County Park is located on the drainage divide between the Yellow River to the south and Paint Creek to the north. State High- way 76 follows the divide southeast to the Mis- sissippi River, a distance of roughly 10 miles. The valleys of Paint Creek and the Yellow River are cut through the Galena Limestone and into the St. Peter Sandstone and older rocks. But on the divide, Galena Limestone is present much of the way to the Mississippi River, and sinkholes are very common in the Rossville area (see Fig- ure 2-1). We will view and enter a prominent sinkhole in the wooded part of the park, and see STOP 2 several depressions in the ground where sink- holes appear to be forming…or re-forming.

Field trip refreshments sponsored by HOWARD R. GREEN COMPANY Thank You.

Additional information about this area:

Glenwood Cave Michael Bounk Iowa Department of Natural Resources Iowa Geological and Water Survey

Glenwood Cave is developed near the base of the Dunleith Fm. of Ordovician age. The entrance at the end of the box is a wet weather overfl ow. Figure 2-2 is an incomplete map of Glenwood Cave (Iowa , 1992) overlain on the USGS 7.5’ quadrangle. During dry weather, this entrance leads Figure 2-1. Color infrared photo of the Ross- downward about 10’ to water level. This wet ville area showing sinkholes (yellow circles). passage can be followed for about 1,600 feet to a “T” intersection with a stream that fl ows from left to right. This stream sumps (goes completely under water) about 30 ft. to the right of the “T.” It is believed to resurge at a spring located in the valley to the north of here, on the west side of the north-south road. To the left of the “T,” the

29 Figure 2-2. Mapped extent (in red) of Glenwood Cave.

passage continues for about 1,100 ft. to where caves which can or could be entered through the stream comes out of an un-enterable slot. A their springs. Other springs, in the Galena short distance before this, there is a fl owstone Group, which are known or believed to be fed climb up to an upper level. Total passage length by solutional caves, include Dunning Spring in for this cave is estimated to be about 1 mile. Decorah, and Big Spring near Elkader. These At one time the passage at the end of which the and other springs and related solutional conduits entrance is located extended at least to the end are important components in the hydrology of of the box canyon. It has since retreated due to the Galena Group in its outcrop area in northeast headward collapse of the canyon. The collapsed Iowa. Understanding the factors controlling the rock prevents the stream from fl owing out here development of this karst is important in protect- except during higher water levels. ing this source of water from contamination by both point source and nonpoint sources of pollu- WARNING: This entrance and several hun- tion. dred feet of passage can be sumped for months This karst is also important as the site of at a time; therefore, it should only be entered, deposition of speleothems. The oxygen isotope beyond the beginning of the water, during dry and carbon 14 analyses of suffi cient stalagmites conditions, when rain is not expected, and in the can provide us with a chronology of the mean company of experienced wetsuit cavers. A full annual temperature, of the area where the cave is wetsuit is required. located, through time.

This cave was shown as a commercial cave References during the summers from 1931-1935. The tour was by boat and cost 25 cents a person. The Hedges, 1974, Intercom, vol. 10, issue 1, National boats which held a guide and two passengers Speleological Society Convention Guidebook, were poled by the guide. Illumination was by p. 117. fl ashlight (Hedges, 1974). Iowa Grotto, 1992, Iowa Cave Map Book, vol. 1, Glenwood Spring and Cave is an easily ac- p. 142. cessible example of the several known stream

30 STOP 3. ing from miles per hour following rainstorms to thousands of feet per day during dry periods. Skyline Quarry – The larger voids act as drains for the aquifer, and The View from Inside an Aquifer groundwater within smaller openings and frac- Bob Libra and Robert M. McKay tures follows the path of least resistance, moving Iowa Department of Natural Resources towards the larger voids. Geologists spend much Iowa Geological and Water Survey time explaining that groundwater isn’t contained in underground . However, in karst aqui- STOP! If you are not wearing a hard hat, you fers the underground river analogy isn’t that far must remain on the bus. off; major conduits are like the main stem of a river, and the smaller voids and fractures are like Skyline Quarry is owned and operated by a three-dimensional web of tributaries. This is in Bruening Rock Products, Inc. of Decorah. The contrast to sand, gravel, and sandstone aquifers, quarry fl oor is about 102 feet above the top of where groundwater movement is more uniform the underlying Decorah Shale; about 70 feet of throughout the aquifer and much slower as it Galena limestone is mined here. The quarry sec- works its way between the individual sand and tion is essentially in the middle of the 235-foot gravel particles. thick limestone portion of the Galena Group. At the top of the quarry walls, only a thin The lower 35 feet of the section is within the cover of unconsolidated soils is present. Beneath upper part of the . It is this thin soil mantle, fractures widen (Figure composed of dense limestone with mudstone 3-2). This is the result of void formation near to packstone depositional textures and contains the top of the bedrock, a common occurrence in numerous chert nodule horizons. Distinctive karst that marks the fi rst steps towards sinkhole multimillimeter-thick, dark-colored surfaces, formation. A larger sinkhole is also exposed in referred to as hardgrounds or corrosion surfaces, cross-section by the quarry walls (Figure 3-3). are common. These are features formed on the The combination of a thin soil cover that of- seafl oor during times of sediment starvation and fers limited fi ltration and protection from any possible water chemistry change. The overlying contamination in downward-percolating soil comprises the upper half water, sinkholes which capture surface runoff of the quarry section. It contains minor chert in and direct it into the aquifer, and essentially no the lower few feet but is mostly chert-free, tends removal of contaminants from the fast moving to be thicker bedded, and has a well developed groundwater in the fractures results in common bioturbated depositional fabric. The upper 10 water-quality problems in the Galena aquifer. As feet of Wise Lake is considered suitable for con- this aquifer supplies much of the “basefl ow” for crete aggregate. area streams, any contamination is delivered to As you enter the quarry, you are in essence the streams as well. “stepping into” the Galena aquifer. Visible in Long-term groundwater monitoring has the quarry walls are nearly vertical fractures and been conducted at Big Spring, which drains a nearly horizontal bedding planes that have been 100-square-mile area underlain by the Galena solutionally enlarged to varying degrees (Figure Limestone in Clayton County. On average over 3-1). These are the pathways that groundwater 15,000 gallons per minute of groundwater dis- fl ows through. The rock “matrix” itself has little charges from Big Spring to the River. permeability and transmits little groundwater. As For comparison, this is a little over one-half the groundwater is forced to fl ow through only a of the average amount of water produced by small percentage of the rock, it moves relatively the Des Moines Water Works. Land use in Big fast. Where large, open, cavernous conduits are Spring’s “groundwater-shed” is essentially all present, dye traces have shown fl ow rates rang- agricultural. Typically, 45-50% of the land is

31 in corn production and 35-40% is used to raise alfalfa. Small dairy and hog operations are com- mon. Concentrations of nitrate-N at Big Spring commonly are near the 10 mg/L U.S. EPA drink- ing water standard. Low levels of atrazine (0.1 to 1.0 ug/L) are typically present, along with 200 to 300 ug/L of phosphorus. Fecal bacteria levels are commonly in the hundreds to thousands of colonies/100 ml. Concentrations of phosphorus, bacteria, and herbicides are generally 1-2 orders of magnitude greater following major rainfall events. These data point out the vulnerability to contamination of this productive karst aquifer. Figure 3-1. Skyline Quarry. Note vertical and horizontal fractures. Additional information about this area:

Decorah Ice Cave George E. Knudson and James Hedges Luther College, Decorah, Iowa

The Ice Cave at Decorah, Iowa, is the larg- est known glacière in North America east of the Black Hills and the subject of much international speculation. A satisfactory theory for ice forma- tion in late spring is that cold air circulates freely through the cave in winter, cooling the rocks to below freezing. Warmed air ascends through fi s- sures in the roof. Thick layers of ice occur after a Figure 3-2. Skyline Quarry. Note widening of thaw of the bluff surface above. Since the mouth vertical fracture below soil horizon. of the cave is higher than the ice chamber, cold air is trapped in the interior in the summer al- lowing ice to persist until August or September.

Figure 3-3. Skyline Quarry. Note sinkhole in cross section.

32 STOP 4. LUNCH

Dunning Spring Park – The Bottom of an Aquifer

Dunning Spring issues from near the base of the Galena aquifer. The much less permeable Decorah Shale - the confi ning bed “fl oor” for the aquifer - is near the land surface, forcing the water to discharge from the wall of the Upper Iowa River Valley. The result is the picturesque falls. The groundwater issuing from the spring is fl owing through an open, cavernous conduit, formed by the solutional enlargement of frac- tures. Solutionally modifi ed fractures and cracks are the most common characteristic of karst. The water from this (and most larger springs in the area) maintains a fairly constant temperature of about 45 degrees F most of the year. Exceptions occur after snowmelt or heavy rains when colder or warmer water rapidly enters the aquifer via sinkholes and losing streams. About 50 feet be- low our feet is the contact between the Decorah confi ning bed and the underlying St. Peter Sand- stone. Dunning Spring near Decorah in Winneshiek County, Iowa. Additional information about the area between Stops 4 and 5:

Losing Streams segment, regardless of the water body’s Bob Libra designated use, shall not exceed a Geomet- Iowa Department of Natural Resources ric Mean value of 126 organisms/100 ml Iowa Geological and Water Survey or a sample maximum value of 235 organ- isms/100 ml. No new wastewater discharges Losing streams are defi ned by Iowa Code: will be allowed on watercourses which di- “Losing streams” means streams which lose rectly or indirectly enter sinkholes or losing 30 percent or more of their fl ow during the stream segments. seven-day, ten-year low stream fl ow periods to cracks and crevices of rock formations, Iowa streams, whether losing or not, com- sand and gravel deposits, or sinkholes in the monly exceed these bacteria levels. At pres- streambed. ent, new discharges to losing streams are not allowed, regardless of the level of treatment. An additional part of the Code addresses losing Streams that lose water to fractured rocks and streams this way: sinkholes are typically considered greater envi- The Escherichia coli (E. coli) content of wa- ronmental and public health threats than those ter which enters a sinkhole or losing stream that lose water to sand and gravel aquifers, in

33 that the lost surface drainage moves much faster tween the Yellow and Turkey rivers. Postville and farther in fractured rock, and can appear in is underlain by 40 to 100 feet of unconsolidated hard-to-predict places. The fractured rock situa- glacial materials which rest on the Maquoketa tions also offers little or no fi ltration of contami- Formation. The karst-forming Galena Limestone nants. is nowhere to be seen, and in fact lies about 200 Losing streams are not uncommon in north- feet deep. Between Postville and the Yellow east Iowa and other parts of the state that are River, Hecker Creek cuts downward towards the underlain by shallow permeable bedrock. Some upward-sloping Galena Limestone. Where the streams lose water into their underlying sand and two meet, the creek begins to lose water. gravel deposits, even when no shallow rock or karst is involved. Losing streams are complex to characterize, as the losing aspect may vary sea- sonally, and the locations where water goes into the ground often changes through the year with fl ow conditions. Efforts to map losing stream reaches, sinkholes, and springs are underway in northeast Iowa, including detailed geologic map- ping to further our ability to predict where such features are most likely to occur. The Yellow River in this area provides a larger example of a losing stream. The Yellow River heads on the slowly permeable Maquoketa Formation, and as its valley cuts into the karstic Galena Limestone, the river loses water into the rock. In the drier parts of most years, the Yel- low River has no fl ow as it crosses the Galena Limestone, although it is fed by an 80-square- mile watershed. Further downstream, the valley cuts into the Decorah Shale “fl oor” below the Galena. Where this occurs, numerous springs discharge groundwater into the Yellow River, and its fl ow from that point on downstream is typically perennial. Hecker Creek is a tributary of the Yellow River. The creek heads near Postville and joins the Yellow about 3 miles north. The uppermost part of the watershed is underlain by bedrock of the relatively slowly permeable Maquoketa Formation, and a relatively thick cover of glacial deposits. As the stream fl ows north, its valley cuts into the underlying karstic Galena Lime- stone. Where the stream runs over the fractured Galena bedrock, it “loses water” into the rock. During relatively dry conditions, the entire fl ow disappears into the rock. Postville straddles the drainage divide be-

34 STOP 5. Section 14, several miles downstream from the originally documented opening. Roberts Creek Sinkhole In 2005, a dye-trace was conducted that con- Gary Siegwarth, Fisheries Bureau fi rmed the direct connection of Roberts Creek Iowa Department of Natural Resources to Big Spring. The sinkhole is 5.8 straight line miles (“as the crow fl ies”) from Big Spring and The Roberts Creek sinkhole, located 2 miles it took nearly 3 days for the dye to be detected west of Farmersburg, can be a highly visible at the spring during low fl ows. However, fl ow example of a losing stream. During low fl ows, bypass manipulations that temporarily diverted the direct opening allows the entire stream- fl ows around the opening during this same low- fl ow to cascade and disappear into the opening fl ow period were detected in fl ow changes at the (Figure 5-1). For several consecutive years this spring within several hours. The Roberts Creek sink caused nearly four miles of Roberts Creek connection is also the suspected origin of numer- to go completely dry. During higher fl ows, the ous non-trout fi sh species that show up in race- sink becomes submerged and is barely visible. ways at the trout hatchery. The original 1856 land survey map for Clay- Roberts Creek is currently listed as an im- ton County documents Roberts Creek ending paired stream due to excessive nutrients that abruptly and labeled as “Sink” in Section 15 on plague the stream. Due to the connection of this the accompanying map (Figure 5-2). More re- impaired stream to the Big Spring aquifer, there cent maps showed Roberts Creek connected to are water quality concerns at Big Spring because Poney Creek with no mention of the losing por- of the associated use of the spring for rearing tion. The current sinkhole opening is located in trout. The direct connection of Roberts Creek is

Figure 5-1. Roberts Creek sinkhole. Note the large visible sink- hole that is taking the entire fl ow of Roberts Creek.

35 Figure 5-2. This original 1856 Land Survey Map shows an early documentation of the Roberts Creek Sink in northwest corner of Section 15, Wagner Township in Clayton County.

suspected to be causing excessive nutrient (as Additional information about this area: well as other unknown chemicals and contami- nants) and sediment deposition problems at the Results from the Big Spring Basin Water hatchery during annual snowmelt and other high Quality Monitoring and Demonstration water events. There is also concern about the Projects consequences of other “emerging contaminants” Robert D. Rowden, Huaibao Liu, entering the Big Spring aquifer. Until these wa- and Robert D. Libra ter quality concerns can be corrected, there is Iowa Geological and Water Survey, consideration of a plan to temporarily divert or Iowa Department of Natural Resources partially block the known fl ow of Roberts Creek into the sinkhole. Agricultural practices, hydrology, and water quality of the 267 km2 Big Spring groundwater drainage basin in Clayton County, Iowa, have been monitored since 1981. Landuse is agricul- tural, dominated by corn and alfalfa production, along with numerous small livestock opera- tions; nitrate-nitrogen (-N) and herbicides are the resulting contaminants in groundwater and

36 surface water (Figure 5-3). The Ordovician Ga- cm inches A 50 lena Group carbonate rocks comprise the main 120 Annual Basin Precipitation 45 aquifer in the basin. Recharge to this shallow, 110 moderately karsted aquifer is dominated by infi l- 100 40 90 35 tration, augmented by sinkhole-captured runoff. 80 30 Groundwater is discharged to the surface at Big 70 25 Spring, where the quantity and quality of the dis- 60 50 20 charge are monitored. '82 '83 '84 '85 '86 '87 '88 '89 '90 '91 '92 '93 '94 '95 '96 '97 '98 '99 '00 Monitoring has shown a three-fold increase in groundwater nitrate-N concentrations from the 1960s to the early 1980s, following a similar B mcm ac-ft 60,000 increase in nitrogen fertilizer applications. The 70 Annual Groundwater nitrate-N discharged from the basin by ground- 60 Discharge 50,000 water and surface water typically is equivalent to 50 40,000 over one-third of the nitrogen fertilizer applied, 40 30,000 with larger losses and greater concentrations oc- 30 20,000 curring during wetter years. Atrazine is present 20 in the groundwater year round, however, con- 10 10,000 taminant concentrations in the groundwater re- '82 '83 '84 '85 '86 '87 '88 '89 '90 '91 '92 '93 '94 '95 '96 '97 '98 '99 '00 spond directly to recharge events, and the unique chemical signatures of infi ltration versus runoff NO3-N load C mg/L kg recharge are detectable in the discharge from 14 Annual flow-weighted Mean NO -N 900,000 Big Spring. 3 12 750,000 Annual NO -N Load Education and demonstration efforts have 3 decreased pesticide use and have reduced nitro- 10 600,000 450,000 gen fertilizer application rates by one-third since 8 300,000 1981, while crop yields have been maintained. 6 150,000 Relating declines in nitrogen and pesticide in- 4 0 puts to nitrate and pesticide concentrations at '82 '83 '84 '85 '86 '87 '88 '89 '90 '91 '92 '93 '94 '95 '96 '97 '98 '99 '00 Big Spring is problematic. Annual recharge, as inferred by discharge from Big Spring, has Atrazine load varied fi ve-fold during the monitoring period, D µg/L kg 10.0 70 overshadowing any water quality improvements Annual flow-weighted Mean Atrazine 5.0 60 resulting from incrementally decreased inputs. Annual Atrazine Load 50

40 1.0 30 0.5 20 10 0.1 0 '82 '83 '84 '85 '86 '87 '88 '89 '90 '91 '92 '93 '94 '95 '96 '97 '98 '99 '00

Figure 5-3. Summary of annual A – basin precipitation, B – groundwater discharge, C – fl ow-weighted mean nitrate-N concentrations and nitrogen loads, and D – fl ow-weighted mean atrazine concentrations and loads from Big Spring groundwater, water years 1982-1999.

37 38 STOP 6.

Chicken Ridge Michael Bounk Iowa Geological and Water Survey Iowa Department of Natural Resources

This portion of the Silurian (Niagaran) escarpment affords spectacular views of the Turkey River valley to the north and the Volga River valley to the south. Much of the Niagaran escarpment in Iowa is characterized by a me- chanical karst, the result of slippage and rotation of blocks of Silurian carbonates on the underly- ing Maquoketa Formation . Pos- sibly, solutional karst once was developed along the entire escarpment in conjunction with stream incision. As the caverns were destroyed by head- ward erosion, mechanical karst developed which diverted surface water rapidly downward to the Brainard Shale, thus preventing additional solu- tional karst. Thus, the present-day escarpment has little solutional karst of any size.

Field trip refreshments sponsored by HOWARD R. GREEN COMPANY public water supplies that rely on surface water Thank You. in this region. Groundwater supplies are so prolifi c that Additional information about this area: some communities do not have municipal wa- ter supplies (e.g., Luxemburg, population 246). Drinking Water Other small communities readily rely upon Pa- Paul VanDorpe leozoic Plateau bedrock aquifers for their drink- Iowa Geological and Water Survey ing water (e.g., Holy Cross, population 339). Iowa Department of Natural Resources

Drinking water for northeast Iowa citizens is derived from Paleozoic aquifers: Devonian/ Silurian; Ordovician above the St. Peter (i.e., Galena Group and, locally, Maquoketa Forma- tion); Cambrian-Ordovician (Jordan) (i.e., St. Peter Sandstone, Prairie du Chein Group, Jordan Sandstone); and the Dresbach (i.e., Wenowoc Formation, Eau Clare Formation, and the Mt. Simon Sandstone). Alluvial, glacial drift, and buried-channel aquifers are available mostly southwest of the Paleozoic Plateau. There are no

39 40 WINNESHIEK ALLAMAKEE FieldTripStop

Cjl Cw RoadField Network Trip Stop Trip Route Other Stop 4: Road Network Dunning Spring Trip Route FederalOther Roads FederalState StateCounty Stop 3: Ops County Skyline Quarry City City

GeologicGeologic Symbols Symbols A6W SinkholeSinkhole A52 NortheastNortheast Iowa Iowa Bedrock Bedrock Geology Geology Decorah Ops Kw (Cretaceous - Windrow Fm.) Kw (Cretaceous - Windrow Fm.) 9 Pcc ( - Cherokee Grp. and Caseyville Fm.) Pcc (Pennsylvanian - Cherokee Grp. and Caseyville Fm.) 9 Dl (Devonian - Lime Creek Fm.) DcDl (Devonian (Devonian - Cedar - Lime Valley Creek Grp.) Fm.) 76 DwDc (Devonian (Devonian - Wapsipinicon - Cedar Valley Grp.) Grp.) SgDw (Silurian (Devonian - Gower - Wapsipinicon Fm.) Grp.) Ss (Silurian - Scotch Grove Fm.) 51 Sg (Silurian - Gower Fm.) Shb (Silurian - Hopkinton and Blanding Fms.) Ss (Silurian - Scotch Grove Fm.) Sls (Silurian - Limestone Facies) OmShb (Ordovician (Silurian - - Maquoketa Hopkinton Fm.) and Blanding Fms.) Stop 2: Allamakee OgpSls (Ordovician (Silurian - - Limestone Galena Grp. Facies)and Platteville Fm.) Om X26 County Park OpsOm (Ordovician (Ordovician - St. - Peter Maquoketa Sandstone Fm.) and Prairie du Chien Grp.) Postville Cjl (Cambrian - Jordan Sandstone, St. Lawrence and Lone Rock Fms.) Ogp (Ordovician - Galena Grp. and Platteville Fm.) FAYETTE CLAYTON Cw (Cambrian - Wonewoc and Sub-Wonewoc Fms.) Monona Ops (Ordovician - St. Peter Sandstone and Prairie du Chien Grp.) Om Geographic Boundaries W64 Cjl (Cambrian - Jordan Sandstone, St. Lawrence and Lone Rock Fms.) State Boundary 18 Cw (Cambrian - Wonewoc and Sub-Wonewoc Fms.) Iowa County Boundary Ogp GeographicCounty Boundary Boundaries (Minnesota & Wisconsin ) Municipalities along field trip route B60 State Boundary

52 Iowa County Boundary Stop 5: Roberts County Boundary (Minnesota & Wisconsin ) Om Creek Sinkhole 13 Municipalities along field trip route Dc 56 Elkader Stop 1: Guttenberg C2W Scenic Overlook

X3C Guttenberg

Stop 6: Chicken Ridge

Shb

X3C 52

Ss DUBUQUE BUCHANAN DELAWARE 3 Ss 52 Luxemburg Shb

52 Ss

Sls Dubuque

Ss

Dc Sls Grand Harbor Resort, beginning and end of trip

Dw Dw Shb

Dc Dw Ss Ss

03 6 12 18 24 Miles

Map of Field Trip Stops (Field trip route outlined in blue.) Iowa Geological and Water Survey Iowa Dept. of Natural Resources 109 Trowbridge hall Iowa City, IA 52242-1319