STATE OP WILLIAM G. STRATTON, Governor DEPARTMENT OP REGISTRATION AND EDUCATION VERA M. BINKS, Director

DIVISION OP THE STATE GEOLOGICAL SURVEY JOHN C. PRYE. Chief URBANA

REPORT OF INVESTIGATIONS 198

FARMDALE DRIFT IN NORTHWESTERN ILLINOIS

BY

PAUL R. SHAFFER

PRINTED BY AUTHORITY OF THB STATE OF ILLINOIS

URBANA, ILLINOIS

1956

STATE OF ILLINOIS WILLIAM G. STRATTON. Governor DEPARTMENT OF REGISTRATION AND EDUCATION VERA M. BINKS. Director

DIVISION OF THE STATE GEOLOGICAL SURVEY JOHN C. FRYE. Chief URBANA

REPORT OF INVESTIGATIONS 198

FARMDALE DRIFT IN NORTHWESTERN ILLINOIS

PAUL R. SHAFFER

PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS

URBANA, ILLINOIS

1956 ORGANIZATION

STATE OF ILLINOIS HON. WILLIAM G. STRATTON. Governor DEPARTMENT OF REGISTRATION AND EDUCATION HON. VERA M. BIXKS. Director

BOARD OF NATITRAL RESOURCKS AND CONSERVATION HON. VERA M. BIXKS, Chairman W. H. NEWHOUSE. Ph.D., Geology ROGER ADAMS, Ph.D., D.Sc, Ll.D.. Chemistry ROBERT H. ANDERSON, B.S.. Engineering A. E. EMERSON, Ph.D., Biology LEWIS H. TIFFANY, Ph.D., Pd.D., Forestry W. L. EVERITT, E.E., Ph.D. Representing the President of the University of Illinois DELYTE W. MORRIS, Ph.D. President of University

GEOLOGICAL SURVEY DIVLSION

JOHN C. FRYE, Ph.D.. D.Sc, Chief

(42848—2500—9-56) CONTENTS

Page

Introduction 5

Location, size, and drainage of the area . 5 Acknowledgments 5 Early studies 5 Age of the drift 5 Methods of study 7 Classification of the Pleistocene series 10 Illinoian drift 10 drift 11 Farmdale drift 11 Thin drift in the upland areas 13 Thickness of the ice 15 Origin of the stratif.ed deposits 15 Character of the drift 16

Upper Farmdale sandy silts with rock flakes 20 Calcareous loess above calcareous Farmdale drift 20

Size analyses of Farmdale till matrix 21 Humic-glei soils 21 ShelbyviUe drift 22

Sand-silt-clay ratios of the till matrix 24 References cited 25

ILLUSTRATIONS

Figure - Page

1. Map of Illinois showing area studied 6 2A, 2B. Map of area studied 8

3. Diagram showing distribution of sand-silt-clay ratios of till matrix 23 Plate 1-A, B. Exposures of Farmdale ice-contact gravels 12

2-A. Stony calcareous Farmdale till 14 2-B. Calcareous Farmdale drift 14

2-C. ShelbyviUe till 14 Digitized by the Internet Archive

in 2012 with funding from

University of Illinois Urbana-Champaign

http://archive.org/details/farmdaledriftinn198shaf FARMDALE DRIFT IN NORTHWESTERN ILLINOIS

PAUL R. SHAFFER

ABSTRACT

The Farmdale drift, consisting of till and stratified deposits is present over a wide area of northwestern Illinois. It covers the area from the Belvidere lobe on the east and the Green River lobe on the south (both regarded as Shelbyville) to the unglaciated area on the west and

northwest. Both south and east of this area calcareous Farmdale drift Is overlain by calcareous

lowan or pro-Shelbyville loess, in turn overlain by calcareous Shelbyville till and Peorian loess.

In the main area of Farmdale drift there is no Farmdale loess, although the loess is present in the surrounding areas. The Farmdale drift is more thoroughly weathered than lowan drift

at the same latitude in . The Wisconsin age of the Farmdale drift is indicated by its lack of thorough dissection, its lack of evidence of continued exposure during Sangamon interglacial time, and its stratigraphic relationships with lowan or pro-Shelbyville loess and Shelbyville

till. The Farmdale till is markedly different in texture from the Shelbyville till, which occurs

both as continuous deposits and as isolated discontinuous patches west and north of its previously mapped extent in Ogle, Lee, and Whiteside counties.

INTRODUCTION in the preparation of the report. John C. Frye, Chief, Illinois State Geological Sur- Location, Size, and Drainage of the vey, lent his support Area to the continuation of the study. H. B. Willman and George E. The area included in this study (fig. 1) Ekblaw have contributed valuable informa- consists of about 2,930 square miles and tion and suggestions throughout the study embraces eastern Jo Daviess, Stephenson, and have also reviewed the manuscript. Winnebago, northwestern Boone, Ogle, Vincent C. Shepps, aided by the writer, Carroll, northern Whiteside, and northern made the mechanical analyses, and John B. Lee counties in northwestern Illinois. It Droste made the x-ray studies. George W. lies essentially within the Rock River Hill White, Head, Department of Geology, Country of Leighton, Ekblaw, and Hor- University of Illinois, has given valuable berg (1948, p. 25). suggestions and encouragement. Herman The major portion of the area is drained L. Wascher, Agronomy Department, Uni- by the Rock River system—Kishwaukee versity of Illinois, spent several days in the River, , Rock Creek, and field with the writer and made valuable their many tributaries. A small area in suggestions concerning the material in northern Carroll and eastern Jo Daviess Boone and McHenry counties. To these counties is drained by relatively short trib- persons and to all others who have contrib- utaries to Mississippi River, namely, Apple uted in any way the writer is grateful. River and Plum River. Acknowledgments EARLY STUDIES Age of the Drift The writer is grateful to many persons for their aid in his field and laboratory The origin, character, and age of the studies and in the preparation of this report. glacial drift in northwestern Illinois east M. M. Leighton, Chief Emeritus, Illinois and southeast of the unglaciated area have State Geological Survey, initiated the proj- engaged the attention of geologists for more ect. He has on several occasions examined than a century. Although earlier observa- critical exposures in the field and has aided tions were made and recorded, the detailed [5] ILLINOIS STATE GEOLOGICAL SURFEY

reports of Shaw (1873, p. 1-201) and of V//.A7///y/yx\ \\ Chamberlin and Salisbury (1884-85, p. 199-322) focused attention on the area and its unusual geologic aspects and problems. The drift was regarded by Chamberlin and Salisbury (1884-85, p. 265, footnote) as older than th^ moraine just south and southwest of Madison, Wisconsin, now re- garded as of Gary age (Glacial Map of

eio«,./.oooro«o I 1 1 k^ North America). Chamberlin and Salis- bury stated, * We do not here wish to as- sert or imply any final opinion as to whether this older sheet is the oldest of the drift sheets known to us in the interior or not. We do, however, desire to be understood as holding that this belongs to one of the two or more ancient drift sheets, as disinguished from the two or more later drift sheets whose margins are marked by the great mo- raines of the interior."

Leverett (1899, p. 26) states, ''In the portion of Illinois north from the latitude of Rock Island the lowan drift occupies a large part of the interval betw^een the glacial boundary and the outer moraine of the Wisconsin series. A drift, tentative!) referred to the lUinoian, forms the surface sheet in that region in Stephenson County and parts of Winnebago, Ogle, Whiteside, Carroll, and Jo Daviess counties." The term lowan as used above, unlike Fig. 1. —Map of Illinois: diagonal lines show the its present usage to denote a substage of the area studied. Wisconsin, referred to a drift that was re- garded as post-Sangamon in age and sep- the later moraines to the earlier Wisconsin. arated from the early Wisconsin drift sheets It does not seem to be separated from the by an interval of recession or deglaciation Illinoisan drift by a definite inter-glacial which Leverett (1899, p. 20) designated stage, but instead to represent a substage or Peorian. The glacial deposits were mapped stadium of the Illinoisan. It may, therefore, as probable Illinoian in Stephenson, Car- be advisable, pending further study, to ap- roll, northeast Whiteside, northwest Ogle, ply to it the double name Later Illinoisan and northwest and southwest Winnebago or lowan." counties and as lowan in eastern Winne- Trowbridge and Shaw (1916, p. 92) bago, southeastern Ogle, and northwestern made the following statement: "The age of

Lee counties and in a narrow strip in cen- the drift in the Elizabeth quadrangle is tral Whiteside County north of Rock not definitely known. It does not belong to River. the last or Wisconsin stage of glaciation, as

Leverett summarized his concept of the its surface has been much more altered by lowan drift of northwestern Illinois and its streams, wind, and other agents than the age relationship to the Illinoian drift at that surface of the Wisconsin drift north and time as follows (Leverett, 1913, p. 698): east of our area. From the relations of this "The so-called lowan drift may stand in drift to drift of known age in Wisconsin about as close relation to the Illinoisan as do and Iowa, it is usually considered to be METHODS OF STUDY 7

lllinoian, though this is by no means "subdued," partly because its relief is nec- proved." essarily slight owing to control by a high Alden included observations in north- baselevel, and partly because glaciation and western Illinois along with his detailed the accumulation of loess have delicately studies of the "Quaternary Geology of smoothed out some of the slight irregulari- Southeastern Wisconsin," which was called ties in the landscape profiles caused by out- by T. C. Chamberlin "a first serious study crops of the more resistant strata. . . . after a first serious reconnaissance." Alden "The surface of the upland is covered in-

(1918, p. 160) made a major contribution completely with a thin mantle of loess, toward unravelling the Pleistocene history which over much of the area is imperfectly of the area when he stated, "After consid- separated from the underlying bedrock sur- eration of all factors in reference to the pre- face by a thin and discontinuous accumula-

Wisconsin drift the writer is convinced that tion of lllinoian till." the conditions were, in general, the same in It is interesting to note that the age of the tracts north and south of the state line, the bulk of the drift west of the Blooming- and he is led to the conclusion already ton moraine and Marengo Ridge was re- stated (p. 152) that the uppermost drift garded as probably or tentatively lllinoian outside the moraines of the Wisconsin stage until Leighton's work in 1923. His west- in southern Wisconsin and ward extension of the Wisconsin drift em-

(at least in that part of it examined by him- phasized the fact that west of the Belvidere self—Boone County, north of Kishwaukee lobe and extending to the east border of the unglaciated area there a drift River ; Winnebago County ; eastern Ste- was that was older than the Belvidere lobe (Shelby- phenson County ; Ogle County ; northern Lee County; and northeastern Whiteside ville). The only possibilities for its age as-

County) is of practically the same age signment then were lllinoian or older be- throughout instead of representing two or cause the Farmdale substage of the Wiscon- m.ore distinct stages of glaciation separated sin stage was then unrecognized. However, by stages of deglaciation, and that the Leighton noted that this older drift seemed whole was probably deposited at the llli- less weathered than the lllinoian drift far- noian stage of glaciation. He admits, how- ther south and southwest in Illinois. Later, ever, that there is legitimate ground for after he recognized the Farmdale loess as difference of opinion in regard to this matter Wisconsin, his feeling that the difference in and that the question of age is not to be weathering might denote an age younger considered as positively settled." than lllinoian prompted the present study. Leighton (1923, p. 267) extended the METHODS OF STUDY Wisconsin drift considerably westward with his discovery of the Belvidere lobe Significant Pleistocene sections were stud- and his westward extension of the Green ied, measured, and recorded at 105 road- River lobe. The drift west of the Belvi- cuts, railroad cuts, and stream bank expos- dere lobe he regarded as lllinoian in age. ures, 14 quarries, and 21 gravel pits (fig.

Flint (1931, p. 424) also regarded the 2). In 42 roadcuts that were too shallow drift west of the Belvidere lobe as lllinoian to reveal vital information and at 123 addi- in age. He stated, "Between the Driftless tional locations, borings with a H/^-inch Area and the outer edge of the Wisconsin auger and ranging in depth from a few to drift sheet east and south of Rock River, 18 feet were made to obtain samples for lies a broad upland developed on nearly study. Depth of leaching was determined horizontal dolomites and shales and subma- on divides and upland areas rather than on turely dissected into a dendritic system of slopes exposed to erosion. rather shallow valleys and correspondingly In addition to the collection of general low ridges controlled by a single large samples, 25 samples from as many sample stream. Rock River (fig, 1). The topog- areas (fig. 2) were studied for sand-silt-clay raphy of this upland merits the adjective ratios of the matrix. The coarse fraction ILLINOIS STATE GEOLOGICAL SURVEY

Fig. 2A. —Map of area studied,.showing principal glacial boundaries and location of exposures examined and of auger borings made during the study. MAP OF AREA STUDIED

R. lOE

^^^ Border of unglociated area •y^ Leverett ( 1898), Trowbridge and Show (1916), EKblaw(l942), modified by Shoffar.

• • ' Leigfifons 1923 boundary of Belvidere and Green River lobes.

Shelbyville boundary (discontinuous deposit"^ common in outer 3 or 4 miles)

O Section discussed in fex

8 10 Miles

Fig. 2B.—Map of area studied, showing principal glacial boundaries and location of expo.sures examined and of auger borings made during the study. 10 ILLINOIS STATE GEOLOGICAL SURVEY

has been retained for a proposed study of Thickness the heavy minerals. Ft. In. Leached till, dark buff, clayey, hard .... 1 6 CLASSIFICATION OF THE Calcareous till, yellow PLEISTOCENE SERIES when dry, gray-yellow with pink tint when The current classification of the glacial damp, limestone pebbles 7 Fine sand, no pebbles, yel- and correlative deposits in Illinois is given low, highly calcareous . 2 6 below (Leighton and Willman, 1950, p. Calcareous till, banded, yellow and grayish lime- 602; Horberg, 1953, p. 12). stone pebbles, compact . 1 6 Blue gummy clay, near- Siage S-ubstage ly gritless in some places Recent postglacial and pebbles up to 1 inch in others, highly calcar- Mankato eous 4-8 Gary lowan loess Wisconsin glacial Tazewell Fossiliferous loess, gray- lowan yellow, rusty streaks Farmdale near base, calcareous throughout, sand Sangamon interglacial streaks, cross-bedded, southward dip ... 5 r Buffalo Hart Jacksonville lUinoian glacial J Sangamon sand 1 Payson Stratified yellow sand and [ Loveland (pro-Illinoian) gray silt with few peb- Yarmouth interglacial bles, few fossils, discoi- dal, calcareous ... 1 6 Kansan glacial ? (pro-Kansan) Illinoian drift (Farmdale per Aftonian interglacial Shaffer) Light blue silt, pebbly, Nebraskan glacial some limestone pebbles, highly calcareous, may ILLINOIAN DRIFT be till 1 Sandy to gravelly till, yel- In this study no Illinoian drift was found low to rusty, limestone pebbles, matrix calcar- in northwestern Illinois north roughly from eous 2 the latitude of Morrison (41° 49'), or ap- Probable till, gray with

pink tint, calcareous. . 7 proximately 45 miles south of the Wiscon- sin state line. In a railroad cut near the village of Irene In his discussion of the section above,

(Leverett, 1899, p. 138 and p. 575; Leigh- Leighton stated, "Here two glacial tills are separated by fossiliferous loess and fos- ton, 1923, p. 271 ; Horberg, 1953, p. 43) a

succession is exposed which Horberg re- siliferous silts and sands with some sugges- garded as Illinoian drift overlain by tion of old vegetation, but neither the fossil younger loess and drift. It constitutes the content nor the vegetation excludes the pos- northernmost and westernmost of his ex- sibility of a retreat and readvance of the posures containing Illinoian drift overlain same ice sheet." bv Wisconsin drift. The section was not examined during the

current study, but because of its similarity No. 1.—Railroad cut, NW % sec. 29, T. 43 N., to other geologic sections that were studied R. 3 E. (Flora Twp.), Boone Co.; description by (especially nos. 4-8) it is believed that the M. M. Leighton, correlation by Horberg. material correlated by Horberg as Illinoian Thickness drift is actually Farmdale and that there Ft. In. materials present. Pleistocene series are no Sangamon Wisconsin drift In the area studied, till older than the Tazewell drift as Soil, dark, loessial, sparse Farmdale and regarded Illinoian in age pebbles 2 6 was found at the following two locations. .

FARMDALE DRIFT 11

No. 2. —Exposure in east bank of Deer Creek, Thus there is no established evidence, at east side of sec. 19, T. 21 N., R. 6 E., about 500 from exposures, of Illinoian till in northern feet north of U. S. Highway 30; elevation at top 680 ± feet. Illinois within 45 miles of Wisconsin. Thickness The distribution of known Illinoian till Ft. In. indicates that the Illinoian glacier Invaded Wisconsin drift Illinois from the east, across the Lake Mich- Peorian, loess, buff-yellow, be- igan basin, as Ossian Guthrie stated long coming gray and calcareous in bottom 3 inches. ... 8 ago (1895, p. 305). He suggested four ma-

Farmdale, loess, more clayey jor Ice invasions In Illinois with two ice than above, becomes siltier sheets that moved directly south from Lake downward, calcareous in Superior and remained west of Illinois spots only, chocolate-brown, rusty brown at base ... 2 River and two ice sheets from Lake Huron.

Illinoian Of the latter, one moved Into the Lake Silt, leached, chocolate- Erie basin and Ohio, while the other "left brown, with gray mottling. 1 Lake Huron at Saginaw Bay, passed diag- Till, clayey, with a few peb- bles; compact, fairly hard, onally across the State of Michigan, entered yellow, top foot leached, Kankakee valley near South Bend, and fol- secondary carbonate in lowed thence along that valley to the Illi- spots in bottom foot . . 2 Till, clayey, pebbly; com-^ nois, which valley it followed to the Mis- pact, yellow-gray, "ghosts" sissippi River, scattering the red jasper or of limestone pebbles; sec- all ondary carbonate in spots . 6 Huron conglomerates, of Canadian ori- gin, all along its tortuous pathway."

No. 3. —Roadcut and auger boring, SW 34 NW }/i Although on the basis of present knowl- sec. 7, T. 21 N., R. 7 E.; elevation top of section. edge the details of movement of this ice 705 feet. sheet Thickness are questionable, the general direction Ft. In. from which it came seems borne out by the Wisconsin evidence In northern Illinois.

Peorian No attempt was made to show an Illi- Loess, leached, yellow-buff noian boundary on the map (fig. as none Loess, calcareous, yellow- 2), buff can be drawn accurately until more de-

Farmdale, loess, more clayey tailed subsurface studies are made. than above, brown, with flakes of carbonaceous ma- terial WISCONSIN DRIFT Illinoian drift Clay, leached, waxy, tough, Farmdale Drift gritty; becomes more grit- ty downward and small Leigh ton In observed a loess be- pebbles appear, gray where 1920 fresh with orange oxida- neath the Peorian and above the Sangamon streaks tion weathered zone in Illinois. In 1926 he re- Till, pebbly, gritty, leached, yellow, with a badly weath- garded it as "late Sangamon loess" (1926, ered pebble of pink granite p. 170) but later called it "Farmdale." Leighton and Willman (1950, p. 603) At the same latitude and within the same noted that the Farmdale loess "has definite township other auger borings encountered valley relationships to the Illinois River no Illinoian drift but only Farmdale loess Valley (ancestral Mississippi), the present above the Maquoketa shale with or without Mississippi Valley below the mouth of the a soil profile on the shale. Also at this Illinois River, and the Wabash and lower same latitude near the town of Elburn in Ohio valleys. Such a relationship suggests Kane County there is reported an occur- a valley-train source. This In turn implies rence of Illinoian drift (Horberg, 1953, an extension of an Ice sheet during the

p. 43). Farmdale substage Into the drainage basin 12 ILLINOIS STATE GEOLOGICAL SURVEY

,-9»» ^

Plate 1. —Exposures of Farmdale ice-contact gravels in pit in NW34 sec. 24, T. 24 N., R. 4 E., about two miles southwest of Mt. Carroll. A—Gravel over lens of pink till near base. B—Contorted gravel over- lain by Farmdale silt and Peorian loess. Photographs by H. B. Willman. FARMDALE DRIFT 13 of the ancestral Mississippi prior to the although in an adjacent cut the erratics may lowan substag;e but not yet recognized in be numerous and included in several inches the series of drift sheets because it fell short of till. Pebbles and cobbles of coarse- and of the subsequent ice lobes." fine-grained granites, diorites, gabbros, The Farmdale loess has been tentatively quartzites, and basalts are remarkably fresh identified (White, 1953, p. 362) at Cleve- and usually show but a small amount of land, Ohio, on the east, and has been rec- etching. When broken the erratics show no ognized in Indiana, Illinois, Iowa, and evidence of a weathering rind. westward into the Great Plains of Kansas Shaw (1873, p. 63) in his discussion of (Frye and Leonard, 1951, p. 298) and the Quaternary deposits in Stephenson Leonard (1951, p. 323). Sand and gravel County remarked, "That part lying west deposits regarded as age equivalents of the of the Illinois Central Railroad and south Farmdale loess are recognized in central of Yellow Creek—being mostly, low, level and western Nebraska (Condra et al., 1950, prairie, underlain mostly by the Cincinnati p. 12) also. shales, and also that low, rich, level part

Although loess, stream silts, and pond and between Waddam's Mound and the range swamp deposits of Farmdale age were of mounds running from the neighborhood known, Shafifer (1954b, p. 693) announced of Warren towards the southwest, and un- the first discovery of deposits of Farmdale derlain by the Galena limestone—may al- most be a driftless region. drift (till and glacio-aqueous deposits) in denominated Few boulders are seen it, northwestern Illinois, coextensive with an over and few or no real gravel deposits can be found." area which had come to be regarded as con- The passage from glaciated to the un- taining a single drift of Illinoian age. His glaciated region occurs almost impercepti- later studies confirmed that the Farmdale bly on the uplands although in the valleys drift (fig. 2) is the only drift in this area. the ice-contact deposits indicate the approxi- Younger Wisconsin drift overlaps the Farm- mate extent of the ice sheet. dale drift east and south of this area. On Chamberlin and Salisbury (1884-85, p. the west the border of the Farmdale drift 265) describe the transition as follows, adjoins the unglaciated area and is marked "Even a keen observer fails to note the by large deposits of ice-contact materials in point of passage from the drift-bearing to the valleys and scattered pebbles, cobbles, the driftless region, unless his attention is and boulders on the uplands. (PL 1.) studiously directed to the subject. Even The invasion of northwestern Illinois by then he will be able to determine the exact the Farmdale glacier resulted in the diver- limit only by a vigilant outlook for erratics. sion of Apple River and the formation of In general, the drift terminates in this way: its very youthful-appearing canyon. approaching the edge from the drift side, Thin drift in the upland areas.—A re- the till becomes gradually thinner and dis- markable feature of the upland areas in continuous, until, at length, it disappears in Winnebago County north of the Pecatonica an irregular and patchy border." River, in Stephenson County, and in the On page 268 these authors clearly de- small glaciated portion of Jo Daviess Coun- scribe the thinning of the drift toward the ty, is the extreme thinness of the Farmdale unglaciated area: "A part of the attenuation drift. The roadcuts generally expose bed- of the old drift border is doubtless due to rock with an overlying succession of : 1 ) a erosion subsequent to the time of its for- foot or two of heavy brown or red-brown mation, but we have been unable to find any residual clay "geest" with many chert frag- evidence that the border ever consisted of ments; 2) scattered pebbles, cobbles, and any special aggregation of drift to which boulders of ice-laid origin; and 3) a few we would apply the name terminal moraine. inches to 5 feet of leached loess. On the contrary, the drift mantle seems to In some areas only four or five erratics us to have originally thinned out gradually can be found in an extensive hilltop roadcut to an attenuated edge." 14 ILLINOIS STATE GEOLOGICAL SURVEY

Plate 2-A. Stony calcareous Farmdale till in roadcut in SWM SW3^ sec. 9, T. 27 N., R. 10 E., about two and a half miles north of Pecatonica, with upper 1^ feet weathered brown, overlain by 13^ feet of Peorian loess.

Plate 2-B. Calcareous sandy Farmdale drift in sec. 18, T. 25 N., R. 11 E., three miles north of Byron, with upper part weathered brown beneath a thin sandy topsoil.

Plate 2-C. Shelby ville till in roadcut in NWM sec. 12, T. 21 N., R. 4 E., with upper V^ feet leached and overlain by 3 feet of leached brown Peorian loess. I'ARMDALE DRIFT 15

In the valleys the maximum extent of the and water-laid silts and clays with peat de-

ice is marked in some places by masses of posits. ice-contact gravels. In the area just east Shaw (1873, p. 109), in speaking of de- of Waddam's Grove in Stephenson County, posits in Ogle County, remarked, "If the

in sees. 5, 6, 7, 8, 16, and 22, T. 28 N., R. phenomena in this interesting locality indi- 6 E., the constructional topography of the cate glacial action, and we think they most

deposits of till and stratified drift has the unmistakably do, it was probably combined appearance of an end moraine although with aqueous forces, and the two causes

Farmdale drift is known to extend farther contributed to the results observed." west. The vast accumulations of stratified drift

were described by Flint (1931, p. 422- Thickness of the ice. —Another remark- 440), and regarding their mode of forma- able aspect of the upland areas in Winne- tion he stated 431), "When the evi- bago, Stephenson, and glaciated Jo Daviess (p. dence yielded by the stratified deposits is counties is the widespread presence of bed- reviewed, the results are interesting. The rock residuum beneath the scattered errat- evidence of composition indicated deposi- ics. The fact that this preglacial surficial tion in lakes with highly variable currents, material remained on the hilltops and hill- in certain cases fluviatile deposition, and sides despite their glaciation indicates that in all cases deposition in direct contact the Farmdale glacier was thick enough to w^ith ice. The evidence of form indicates create ice-flow, as otherwise the residual that the masses of deposits are not erosion material would have been readily removed. remnants, but original forms of accumula- Throughout most of the upland area tion built in contact with ice. The evidence there is about 300 feet of relief, and another of distribution indicates deposition in 200 feet of ice would probably be necessary ponded water controlled by pre-existing to- for flow to occur. On this basis the Farm- pography. dale ice sheet had a minimum thickness of "This evidence presents no conflicting 500 feet and probably thickened consider- elements. It points consistently to a single ably back from its margin. definite reconstruction of the conditions un- The thinness of the Farmdale drift and der which the stratified deposits had their its relationships with the overlying lowan origin. The terraces at several accordant or pro-Shelbyville loess and Shelbyville till levels require for their development the for-

indicate that : 1 ) after the Farmdale ice mer presence of several extensive lakes. sheet invaded the area it melted down and Their ice-contact form and stratification re- back fairly rapidly; 2) loess was deposited; quire that ice shall have been present in the and 3) then the Shelbyville glacier ad- valleys throughout their accumulation. vanced over a portion of the area without a Since each level is represented throughout long weathering interval between. Some nearly the whole region, each lake, to- staining of sand in the upper part of the gether with ice, must have existed in nearly Farmdale drift is present at some places and every valley. These requirements are satis- an accumulation of Farmdale peat is known fied only by the melting-away of an ice sheet at several others, but at no place is there in situ, not inward from a lateral margin ..evidence of a significant period of weather- but from the top down. Under such con- ing between the deposition of the Farmdale ditions, and only under such conditions, can till and the deposition of the overlying the simultaneous presence of ice and lakes lowan or pro-Shelbyville loess or between in all the valleys be explained. Since the the deposition of the loess and the deposi- form and structure of the stratified de- tion of the overlying Shelbyville till. posits yield no evidence whatever of bodily Origin of the stratified deposits.—The movement of the ice in contact with them, Farmdale drift consists not only of till but and since movement inevitably would have also of huge stratified deposits in the form swept away those deposits built in exposed of kames, kame terraces, crevasse fillings, positions, it follows that by the time the 16 ILLINOIS STATE GEOLOGICAL SURVEY lakes came into existence, all such motion contain Farmdale drift overlain by Peorian had ceased. We have to deal, then, with an loess. ice sheet that lost its motion, passed into a stagnant condition, and melted away in No. 4. —Railroad cut at village of Stratford, sec. 8, T. 23 N., R. 9 E. place, from the top down, disappearing first from over the interfluves and remaining Thickness Ft. In. longest in the valleys." Wisconsin Character of the drift. —The Farmdale Peorian Clay, silty, leached, dark gray 8 till is frequently light pink to salmon in Loess, leached, brown to light color (7.5 YR 8/4 dry) and sandy tex- yellow-brown .... 3 4 tured. It is considerably different textur- Shelbyville Till, clayey, pebbly, top 6 ally from the overlying Shelbyville till inches silty, leached, yel- (fig. 2). low-brown 1 6 Till, clayey, pebbly, leached, A characteristic feature of the upper 3 or yellow-gray 6 4 feet of both ice-laid and water-laid Farm- Till, clayey, pebbly, calcar- dale deposits is the widespread presence of eous, yellow-gray ... 1 6 or pro-Shelby ville, loess, a conspicuous red-brown to rusty brown lowan calcareous, gray, limonite leached zone (pi. 2, A and B) developed by stains and streaks, espec- weathering. The material is clay-bound ially in top few inches . , 1 pebbly sand or clay-bound sand which con- Farmdale Sand, with a little clay tains pebbles, cobbles, occasional boul- and binder, calcareous, brown ders of coarse- and fine-grained granite, and yellow 3 Sand, with an occasional silty diorite, gabbro, and basalt. Etching of the mass or streak, calcareous, granites is and the coarse-grained common brown and yellow ... 1 3 basic materials are generally altered, but

the weathering and etching phenomena, The contact between the Farmdale and close examination, not indicate or upon do the overlying loess in this railroad cut was both Sanga- suggest exposure throughout determined by digging or boring in a num- time, as would have to mon and subsequent ber of places. At many places there was a of Illi- be the case if the materials were slight concentration of clay in the upper noian age. few inches of the Farmdale drift and usu- The thickness of the red-brown zone of ally there was a concentration of iron oxide,

leaching and staining is highly irregular, but it was always calcareous and at no depending upon the thickness of the loess place was a soil developed or a significant

over it and the texture of the till or strati- weathering interval recorded. In some

fied drift in which it occurs. Where strati- auger borings on the south side of the rail-

fied drift is very sandy the leaching and road pinkish-red calcareous sandy Farmdale

staining may be as much as IIV2 ^^^^ thick, till is present beneath the lower loess. but in the same gravel pit a few yards away the red-brown zone may be only 3 feet No. 5.—Roadcut in NW i^ SW M sec. 31, T. 23 N., R. 11 E., about 17 miles east-by-southeast of thick with calcareous sands and gravels be- No. 4. low. Excellent examples of the variation in Thickness thickness of this zone are present in the ex- Ft. In. posures of stratified drift near Forreston Wisconsin (No. 10) and in the Hazelhurst gravel pit Peorian, topsoil and brown (No. 9). loess, leached; lower 9 inches contains scattered The following geologic sections show pebbles 1 6 some of the characteristics of the Farmdale Shelbyville Till, clayey, pebbly, leached, drift. The first five (Nos. 4-8) contain yellow-gray 9 Farmdale drift overlain by younger Wis- Till, clayey, pebbly, calcar- consin till and the later ones (Nos. 9-21) eous, yellow-gray 2 3 FARMDALE DRIFT 17

Thickness Thickness Ft. In. Ft. In. lowan or pro-Shelbyville, loess, Loess, calcareous, yellow and

calcareous, gray and yel- gray, fossiliferous 1 6 low-gray Farmdale, till, sandy, calcar- Farmdale, with pebbles, sand eous, bouldery at top, pink . 6 some cobbles, and some gravel; calcareous, yellow, occasionally stained light In roadcuts at the railroad crossing just rusty brown in upper few south of the above geologic section the pink inches Farmdale till is well exposed interbedded

with sand, pink silts, and gravel. The thickness of the lower loess ranges from 3 inches to as much as 3 feet over a No. 8.—Auger boring in S j^ NW \i sec. 15, T distance of several hundred yards in this 24N., R. 11 E. cut. Thickness Ft. In. Wisconsin 6. auger boring No. —Roadcut and on east side of Peorian, topsoil, powdery, gray, on hilltop in road NW M SE M sec. 1, T. 23 N., and loess, leached, yellow- R. 9E. buff with gray mottling Thickness from 2 to 3 feet .... 4 Ft. In. Shelbyville Till, silty, pebbly, leached, Wisconsin fairly soft, light yellow and Peorian, topsoil and loess, gray 3 leached, bufF-brown. . . 3 Till, clayey, silty, pebbly, cal- Shelbyville careous, light yellow and Till, clayey, pebbly, stony, gray ...... 7 9 leached, light yellow to lowan or pro-Shelbyville, loess, yellow-gray 1 calcareous, gray with rusty Till, clayey, pebbly, stony, yellow streaks, bottom 3 calcareous, light yellow to inches rusty brown ... 9 yellow-gray, top 6 inches Farmdale, till, clay-bound, brown 1 6 sandy, pebbly, calcareous, lowan or pro-Shelbyville, loess,

yellow to yellow-gray . . 6 calcareous, pink and rusty Boulder or bedrock at base brown 3 Farmdale Till, pebbly, sandy, with clay binder, calcareous, red- sec. 22, T. 23 N., R. 7 E

brown to rusty brown . . 9 Thickness Till, sandy, pebbly, with a Ft. In. little clay binder, calcar- eous, red-brown to light Wisconsin Peorian, yellow 5 topsoil and loess, leached 1 Farmdale No. 7. —Roadcut and auger boring on east side Sand and gravel, clay-bound, of road in sec. 1, T. 23 N., R. 9 E., about 150 yards leached, red-brown. . . 2 north of C. B. and Q. R.R. Sand and gravel, leached,

slightly iron-stained . . 2 Thickness Sand and gravel, calcareous, Ft. In. gray 2 Wisconsin

Peorian, loess, leached brown . 1 Shelbyville The red zone is variable in thickness in Till, clayey, pebbly, leached, this pit depending on the texture of the un- yellow-gray 6 Sand and pebbles, calcareous 3 derlying material. Till, clayey, pebbly, with cobbles and boulders, cal- No. 10. —Gravel pit near Forreston, in NW 3^ careous, yellow-gray . . 2 NE sec. 20, T. 25 N., R. 8 E.; elevation at top Sand, pebbles, cobbles, and M feet. boulders, calcareous, yellow 9 940-f Till, clayey, pebbly, calcar- Thickness eous, yellow-gray ... 9 Ft. In. lowan or pro-Shelbyville Wisconsin Loess, calcareous, yellow and Peorian, topsoil and loess,

gray 1 leached, yellow- brown . . 3 .

18 ILLINOIS STATE GEOLOGICAL SURVEY

Thickness T,'.ickness Ft. In. Ft. In. Farmdale Farmdale Silt and sand, pebbly, clay- Till, pebbly, leached, yellow-

bound, light brown . bufF 3 Sand, pebbly, clay-bound, Till, clay-bound, sandy, peb- leached, red-brown to rusty bly, leached, red-brown to brown, granites common. rusty brown 1 6 Sand, clay-bound, leached, Till, sandy, pebbly, calcar-

rusty brown to red-brown . eous except for top 6 Sand and gravel, calcareous, inches, with enough clay yellow, and gray; lime- to bind it loosely, soft, yel- stone and dolomite peb- low-bufF 3 6 bles a little powdery on top; iron staining near top No. 14. —Auger boring on top of Bunker Hill, and in some beds below 70 NE li NE M sec. 19, T. 26 N., R. 9 E.; elevation 965 feet. Thickness No. 11.—Gravel pit in NE ^ NVV sec. 22, T H Ft. In. 25 N., R. 8 E.; elevation 900+ feet. Wisconsin Thickness Peorian Fi. In. Topsoil and silt, leached, Wisconsin light brown 2 Peorian, loess, leached, yellow Loess, leached, brown, with a to brown 2 clayey layer from 2 to 3 Farmdale feet 1 9 Gravel; clay-bound, leached, Farmdale red-brown to rusty brown; Till, clay-bound, pebbly, granites and other igneous leached, brown to brown- ish-yellow 9 pebbles common ... 1 9 Gravel, sandy, clay-bound, Till, sandy, pebbly, calcar- leached, rusty brown to eous, light yellow, soft on dark brown 3 auger 7 Sand and gravel, calcareous, cross-bedded, iron staining No. 15.—Roadcut in SE 3^ SW ^ sec. 34, T. 28 common, limestone and do- N., R. 9 E., elevation 805± feet. lomite pebbles, powdery in Thickness top 2 feet 36 Ft. In. Wisconsin Peorian, topsoil and loess, rusty is The brown to red layer variable leached, brown .... 2 6 in thickness in the gravel pit. Farmdale Till, clay-bound, sandy, peb-

bly, leached, brown. . . 1 i^ No. 12.—Roadcut in NW ^ NW sec. 17, Till, sandy, pebbly, calcar- 25 N., R. 9 E.; elevation 828 feet. eous, yellow-gray, sandy above, more compact below 2 6 Thick) Ft. In. Wisconsin Cobbles and boulders are common in this Peorian, topsoil and loess, section, indicating much water action dur- leached, brown . . . . 6 Farmdale ing deposition of the till.

Till, silty-textured, leached . 9 No. 16. Roadcut and auger boring in SW Till, clay-bound, sandy, — 34 sec. T. 27 N., R. 10 E.; elevation 835 feet. leached, yellow-brown to SW }4 9, brown Thickness Till, clay-bound, sandy, peb- Ft. In. bly, bouldery, leached, Wisconsin light yellow-gray Peorian, topsoil, gray; and Till, sandy, pebbly, calcar- loess, leached, brown . . 1

eous, light yellow-gray . Farmdale Till, clay-bound, pebbly, leached, chocolate-brown No. 13. —Roadcut and auger boring in NW 34 to dark brown .... 1 sec. 4, T. 25 N., R. 9 E. Till, clayey, sandy, pebbly, Thickness leached, rusty brown and Ft. In. dark brown Wisconsin Till, sandy, pebbly, calcar- Peorian, topsoil and loess eous, yellow-gray with a

leached, brown . pink cast :

FARMDALE DRIFT 19

No. 17.—Roadcut in SW M SW M sec. 6, T. No. 21.—Roadcut in NW ^ sec. 32, T. 46 N. 23 N., R. 11 E. R. 3 E.; elevation 930 feet. T/iickness Thickness Ft. In. Ft. In. Wisconsin Wisconsin Peorian (?), topsoil, sandy, Peorian, topsoil and loess, leach- leached, dark .... 9 ed, brown Farmdale Farmdale Sand, clay-bound, leached, Till, clay-bound, sandy, peb-

rusty brown with scattered bly, leached, rusty brown . large boulders .... 1 Till, sandy, pebbly, cobbly, Sand, pebbly, clay-bound, bouldery, calcareous, yel-

leached, red-brown ... 9 low-gray and pink . Sand, a little clay binder, a few pebbles and cobbles, the al- leached, red-brown, rusty Alden (1918, p. 157) described

brown, and yellow-brown . 2 teration of the drift west of Rock River as

and gravel, calcareous . 4 6 Sand follows

"Generally throughout this tract the up- No. 18. —Roadcut and auger boring in NW 3^ per part of the drift shows the effects of SW M sec. 6, T. 43 N., R. 1 E.; elevation 812 feet. alteration by exposure to the weather dur- Thickness Ft. In. ing the long time since its deposition. The

Wisconsin amount of this alteration is one of the most topsoil, light gray; and Peorian, important reasons for referring its deposi-

loess, leached, brown . . 1 3 Farmdale tion to the Illinoian stage of glaciation. Till, clay-bound, sandy, peb- Where the drift is very thin it is little more

bly, leached, rusty brown . 2 than a layer of gravel composed of pebbles Till, sandy, pebbly, leached, light brown, with a few of less readily soluble rocks such as dense

masses of dark clay . . . 1 fine-grained crystallines, quartzites, quartz, Till, sandy, pebbly, calcar- and chert. thicknesses of 2 or 3 feet eous, light gray, yellow- Where gray, and pink .... 3 remain the drift is brown or reddish brown, sandy, and gravelly, with perhaps some non- No. 19. —Roadcut and auger boring in SW J^ calcareous clayey matrix but with few lime- N., 1 sec. 6, T. 45 R. E. stone pebbles (and those with surfaces Thickness roughly etched by solution). Where thick- Ft. In. nesses of more than 5 to 6 feet remain, the Wisconsin Peorian, topsoil, dark gray; and drift below this depth is usually unaltered,

brown . . 1 6 loess, leached, highly calcareous, fresh till. The top of the Farmdale unaltered clayey till is generally marked Sand, leached, brown ... 1 Sand, clay-bound, leached, by an abrupt change in color from bluish, with scattered pebbles, gray, pink, or buff to dark brown or red ; rusty brown 1 6 Till, sandy, pebbly, calcar- the matrix becomes more gritty and less

eous, light yellow-buff . . 1 clayey, is largely or quite leached of its lime carbonate, and the limestone pebbles No. 20.—Roadcut in SE M sec. 12, T. 45 N., are few and rotted or have roughly etched R. 3 E.; elevation 940 feet. surfaces. A few inches above or within Thickness a foot, the limestone pebbles disap- Ft. In. about pebbles Wisconsin pear entirely and only sand and of Peorian, topsoil and loess, the less easily soluble rocks are found, com-

leached, yellow-brown . . 3 pactly bound together by a little sticky, non- Farmdale Till, clay-bound, sandy, peb- calcareous clay. In this part, which in many bly, leached, yellow-brown places is 2 to 4 feet thick, there is sometimes to red-brown 2 indefinite banding as though due to set- Till, sandy, pebbly, calcar- an

eous, yellow-gray to pink . 1 tling or pressure." 20 ILLINOIS STATE GEOLOGICAL SURVEY

The above is not a description of glacial No. 24.—Gravel pit in NE H NW M sec. 24, T. 24 N., R. 4 E. drift of Illinoian age subjected to the long- Thickness continued weathering and leaching during Ft. In. and since Sangamon time. It is descriptive Wisconsin of materials of much more recent age which Peorian Topsoil and loess, leached, have suffered much less weathering. buff 7 8

This is one of the important reasons for Loess, calcareous, buff . . 4 Farmdale referring its deposition to the Wisconsin *Silt, calcareous, chocolate- stage of glaciation. brown, with a few small

pebbles 1 silts Upper Farmdale sandy with rock *Silt, calcareous, chocolate- flakes.—Another feature found at some brown, with gray spots and mottling; contains rock places in the upper part of the Farmdale

flakes and small pebbles . 1 drift is a bed of sandy silt with numerous Gravel, clay-bound, sandy, calcareous, small rock flakes. The bed is present east pebbly, red- brown to orange, contains of Freeport, east of the village of Dakota, some partially decayed north of Mt. Carroll, and in several large limestone pebbles and some slightly etched gran- gravel pits just south and west of Mt. Car- ite pebbles 2 roll. It is in the following geologic sec- Clay, silty, calcareous, gray- tions and is indicated by an asterisk. brown, lens 6 Gravel, calcareous, stained yellow and brown, lime- No. 22. —Roadcut and auger boring in SW ^ stone pebbles are yellow NE )i sec. 30, T. 27 N., R. 9 E. and powdery 1 6 Thickness Ft. In. Coarse ice-contact gravels with inter- Wisconsin bedded lenses and layers of pink, sandy till Peorian (pi. and B) are exposed at places in Loess, leached, bufF-brown . 3 1, A Loess, calcareous, buff-brown 5 this pit. Farmdale *Silt, calcareous, brown to These last three geologic sections are rep- with fine chocolate-brown, resentative of the silt that sometimes oc- sand, medium sand, small rock flakes, and small peb- curs in the upper part of the Farmdale bles, igneous pebbles at drift. In the first two sections the silt ap- base; conformable above pears to have been stirred up on the sur- and below 2 face of the drift, possibly by wind action.

Near Mt. Carroll it appears to be water- Along the road down slope to the east laid above the ice-contact gravels. In any there is calcareous sandy Farmdale till with event, it does not appear to have traveled some rusty brown staining in the upper por- very far from its source. The important tion. fact is its conformable relationship with the loess above and the drift below. Where the No. 23.^—Roadcut and auger boring^ near center of south line sec. 33, T. 28 N.,^R. 9 E. loess above is calcareous, this upper Farm- Thickness dale silt is also calcareous, as is the contin- Ft. In. uation of the drift below. Where the loess

Wisconsin above is thin and leached, the silt below is Peorian, topsoil and loess, leach- also partially or wholly leached. ed, brown 7 Farmdale Calcareous loess above calcareous Farm- *Silt, and fine sandy silt, very slightly calcareous, brown dale drift.—At two places the Farmdale to chocolate-brown, with drift was overlain by loess, extending to the some rock flakes. ... 2 surface, that was not completely leached of Pebbly and gritty gradation to geest its carbonates. .

FARMDALE DRIFT 21

No. 25. —Auger boring near village of Hunter, in classification of Shepard (1954, p. 157) is sec. 26, T. 46 N., R. 3 E. SE ^ SW M silty sand. Thickness Humic-glei soils. Another noteworthy Ft. In. — feature of the Farmdale drift region is the Wisconsin Peorian local development of some unusual soils at Topsoil, leached, powdery, places near the boundary between the Farm- dark gray becoming brown dale drift and Shelbyville till and at sev- at base Loess, leached, clayey from eral places within the Farmdale drift area

IM to 2^ feet, yellow . well beyond the Shelbyville border (geo-

Loess, calcareous, yellow . logic sections nos. 27-29). Farmdale, till, sandy, pebbly, with a little clay binder, The soils, once called Wiesenboden calcareous, yellow-brown, (meadow soils) and Half Bog soils (Year- rusty brown top few inches book of Agriculture 1938, p. 1110), are now generally described under the general No. 26. —Auger boring just north of Stockton, in SW M SW M sec. 1, T. 27 N., R. 4 E. term humic-glei soils. In the area studied Thickness they occur in low flat areas or in flat areas Ft. In. on slopes. The soils are generally dark be-

'isconsin cause they contain large quantities of or- Peorian ganic material, but may be gray near the Topsoil, leached, dark, be- surface and hlue-gray or greenish gray at coming brown at base . 1 Loess, leached, buff to brown 3 6 depth. Where seen in the area the soils are Loess, calcareous, buff to not very productive, drain slowly, and ap- brown 6 Farmdale, till, silty, pebbly, parently accumulated in undrained areas. calcareous, pink to salmon- colored 7 6 No. 27.—Roadcut in NW M NW M sec. 36, T. 27 N., R. 6 E. The above sections are further evidence Thickness of the young character of the Farmdale Ft. In. Wisconsin drift. Topsoil and loess, buff-brown . 3 Clay and silty clay, leached, Size analyses of Farmdale till matrix.— olive-gray, with blue-gray The percentages of sand, silt, and clay in ten streaks; scattered pebbles in upper part, more numerous samples of calcareous Farmdale till col- below; forms lens less than lected from roadcuts and auger borings in 100 feet long 2 a zone about 20 miles wide (north-south) extending from four miles northwest of the Topsoil is absent over the olive-gray clay village of Caledonia, westward 24 miles to which grades downward into bedrock re- Pecatonica, except for one sample from a siduum that contains many chert fragments. roadcut 35 miles south of the northernmost The pebbles in the clay are mainly siliceous, sample locality, were determined according but granite, diorite, gabbro, and diabase to the procedure employed by Shepps ( 1953, pebbles, cobbles, and small boulders are p. 34) in his studies of tills from northeast- present. ern Ohio. The procedure includes the pip- ette method of Krumbein and Pettijohn No. 28. —Ditch excavation 13 feet deep and about 200 feet long, in NE SW i^ sec. 17, T. 44 N., R. p. 166-172). The material studied M (1938, 2E. was essentially the till matrix inasmuch as Thickness pebbles larger than 10 mm. were excluded. Ft. In. Wisconsin The results of the analyses (fig. 3) con- Loess or silt, mostly leached, firm that the Farmdale till, which seems slightly calcareous in lower easily distinguishable from the younger 6 inches, yellow-brown . . 5 Silt, leached, gray with organic Shelbyville till in the field, is strikingly dif- stain along joints, limonite ferent texturally, and according to the stained, bedded .... 2 22 ILLINOIS STATE GEOLOGICAL SURVEY

Thickness Depth Ft. In. 3'4"-3'8" good quartz peak, feldspar, two kinds of Silt, with scattered pebbles, top carbonate. 6 inches very silty, remainder 4'6"-4'9" good quartz peak, feldspar, two kinds of clayey, slightly more calcar- carbonate. eous, crumbly, dark gray to 4'9"-5' good quartz peak, feldspar, two kinds of black 2 3 carbonate. Clay, sandy, pebbly, some lay- 5'-5'3" good quartz peak, feldspar, carbonate. ers very clayey, some very 6'-6'4" good quartz peak, feldspar, two kinds of sandy, slightly calcareous in carbonate. places to highly calcareous in places, pink, red, gray, rusty The presence of feldspar throughout the brown and yellow .... 3 9 upper portion of the material eliminates the

possibility that the material is the result No. 29. —Roadcut and auger boring in NE 3^ of NE % sec. 2, T. 23 N., R, 9 E.; interpretation from long-continued weathering of till accom- sample study. panied by decomposition of the silicates. Thickness Ft. In. The two different kinds of carbonates pres- Wisconsin ent from 21/2 ^^^t downward indicate that

Loess or silt, leached, brown . 6 at least some of the carbonate may be pri- Clay, silty, leached, scattered mary, which further supports the idea that pebbles, mostly siliceous, but weathered surface also con- the soils are accumulations in place rather tains granites and other than the result of weathering of till. igneous pebbles, gray to dark gray with dark organic ma- Shelbyville Drift terial near the top and in spots below 2 3 Leverett (1899, p. 192) states, "The Clay, silty, visibly calcareous oldest of the Wisconsin drift, so from S]/2 to 83^ feet, scatter- moraine ed pebbles and rock flakes far as recognized, is one exposed to view in common, greenish gray, oxi- central and eastern Illinois and western In- dation stains and organic ma- terial common 5 9 diana, but which is overridden by later mo- Silt, calcareous, gray-green, raines in districts farther north and east. with some oxidation to yel- This has for some years been known as the low-brown 1 3 Clay, silty, with scattered peb- Shelbyville moraine, the name being de-

bles, calcareous, yellow . . 1 6 rived from a city in which Silt, pebbly, calcareous, yellow- brown, powdery .... 6 is situated on the extreme southwest point Clay, silty, pebbly, some of the morainic loop." streaks of fine sand, calcar- In present classification of glacial deposits eous, greenish gray, some yel- low-brown oxidation ... 2 6 in the Upper Mississippian Valley the Shel- silt pebbles, Till (?), or with byville drift is regarded as the oldest drift calcareous, yellow-gray, pink of the Tazewell substage of the Wisconsin cast when wet 1 6 Till (?), sandy, pebbly, calcar- stage of glaciation. yellow-brown and pink 9 eous, Leverett (1899, map opposite page 130) Bedrock or boulder mapped lowan drift in a large part of northern Lee and southeastern Ogle coun- Samples from both roadcut and the auger ties, north and west of the cities of Ster- boring part of the above section were pre- ling and Dixon, sli^htlv north of the village pared for study by x-ray spectrometer. The of Stratford, with the western boundary ex- spectrometer traces were interpreted by J. tending northeastward to include the cities B. Droste as follows: of Oregon, Byron, and Rockford. The Depth drift that Leverett called lowan, in Lee and 0-6" good quartz peak, feldspar. Ogle counties at least, is now regarded as G"-\' good quartz peak (possible kaolinite and Shelbyville drift but mav turn out to be feldspar). \'-\'6" good quartz peak (possible feldspar). lowan drift (Shaffer. 1954a. n. 455), even l'6"-2' good quartz peak, feldspar, hint of car- though what is now called lowan is con- bonate. 2'6"-3' good quartz peak, feldspar, two kinds of siderably different from Leverett's lowan carbonate. drift. SHELBYVILLE DRIFT 23

100% CLAY Less than .0039 millimeters

Clay

100% SAND 50% 100% SILT

10 to .062 millimeters .062 to .0039 millimeters

Fig. 3. —Diagram showing distribution of sand-silt-clay ratios of till matrix (after Shepard). Numbers 1 to 12 inclusive are Shelby ville till, numbers 13 to 23 inclusive are Farmdale till.

Leighton (1923, p. 270) named and de- and outwash deposits, indicated that he scribed the Belvidere lobe of Wisconsin gla- thought the drift might extend farther west. ciation and the drift deposited from it. The Subsequent work bv Leighton and Shafifer discovery of the Belvidere drift, now re- (1949, p. 1904) and by Shaffer (1954a, p. garded as a correlative of the Shelbyville, 446) indicated that the Shelbyville glacier represented a considerable westward exten- did extend across Mississippi River in a sion of Wisconsin glacial deposits beyond narrow lobe between Clinton and Prince- the Marengo Ridge and the Bloomington ton, Iowa, as far west as the Goose Lake moraine in southern Boone, northern De- channel. Kalb, eastern Ogle, and southeastern Win- Knappen (1926, p. 72 and map in nebago counties. pocket) mapped early Wisconsin or lowan

In the same paper Leighton (1923, p. ( ?) drift in the southernmost part of the 269) described and mapped another west- Dixon quadrangle, in an east-west belt from ward extension of Shelbyville drift, the one to three miles wide, south of the village Green River lobe, approximately to Rock of Eldena. The area north of the belt, in- Island County. The question marks which cluding the exposures in Dixon which Lev- he employed to show the western margin erett (1899, p. 138) reported, and the esker of the lobe, where it is covered bv thick loess that caused the loop in Rock River at the 24 ILLINOIS STATE GEOLOGICAL SURVEY village of Grand Detour, he regarded as Thickness Ft. In. lUinoian. The drift that he called early careous, yellow, several Wisconsin or lowan (?) is now regarded scattered pebbles as Shelbyville. Farmdale (?), till, clayey, silty, pebbly, calcareous, yellow- Templeton (1939, unpublished thesis, brown University of Illinois), who did detailed Bedrock or boulder work in the Sterling area, described the

Shelbyville till in the following manner: It is possible that in the above section all "When fresh and unweathered, the Shelby- material below the Peorian loess may be ville till has a distinct greenish-hue, or a Shelbyville drift, consisting of two till lay- color intermediate between blue-gray and ers with an intervening silty layer. How- ever, other exposures in the green-gray . . . and weathers to a pale yel- general area low-brown." support the interpretation shown.

In the current study it has been deter- No. 31.—Auger boring in SVV NE sec. 11, mined that the Shelbyville drift, which con- ^ M T. 23 N., R. 8 E. sists of materials like that described in the Thickness two following sections and illustrated on Ft. In. plate 2-C, extends considerably west and Wisconsin Peorian north of its former mapped limits. It oc- Topsoil, clayey, leached, black 1 6 curs not as a continuous blanket of drift but Clay, leached, mottled, gray- 2 as patches capping small hills or in broad brown Loess, silty, leached, yellow flat areas surrounded by Farmdale drift. and gray, soft .... 1 6 Discontinuities of this type were pointed out Loess, silty, calcareous, yel- low and gray, soft ... 1 by White (1952, p. 1312) in the plateau re- Shelbyville gion of northeastern Ohio. The boundary Till, silty, clayey, calcareous, as shown (fig. 2) follows the northernmost yellow 1 Till, clayey, pebbly, yellow to westernmost deposits of Shelbyville and yellow-gray, some thin drift that were found. Other isolated beds of gray to whitish- gray pebbly clay till, espe- patches may be found beyond this boundary. cially between 8 and 11 feet. 7 The esker or crevasse filling of glacio- fluvial material that accumulated in the val- Sand-silt-clay ratios of the till matrix.— ley of Rock River near the village of Grand Sand-silt-clay ratios of the matrix of eleven Detour and caused the big loop in the river samples of calcareous Shelbyville till were is regarded as Shelbyville in age rather than determined by the method already men- Illinoian. tioned. The samples were collected from roadcuts and auger borings in an area ex-

No. 30.—Auger borinc; in NVV }4 NW }4 sec. tending from just north of Morrison to 24, T. 22 N., R. 4 E. seven miles southeast of Oregon, a distance T/iickness of about 40 miles in a northeast-southwest Ft. In. direction. Some of the samples were col- Wisconsin lected close to the outer margin of the Shel- Peorian, clay, silty, leached, gray-brown and brownish- byville drift and some from localities at yellow 3 3 least ten miles inside the boundary. The Shelbyville results (fig. 3) indicate that the Shelbyville Till, clay-bound, sandy, peb- bly, leached, brownish-yel- till is considerably different from the Farm- low 1 3 dale till and, with the exception of one sam- Till, clay-bound, pebbly, cal- ple, would be classified after Shepard (1954, careous, brownish-yellow . 3 p. 157) in the sand-silt-clay area as clayey lowan or pro-Shelbyville (?), silt, with loess texture, cal- sandv silt. REFERENCES 25

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, 1913, lowan drift (Abstract): Geol. Soc. Flint, R. F., 1931, Glaciation in northwestern America Bull., v. 24, p. 698. Illinois: Am. Jour. Sci., v. 21, no. 221, p. 422-440. Shaffer, P. R., 1954a, Extension of Tazewell glacial substage of western Illinois into east- Frye, J. C, AND Leonard, A. B., 1951, Stratigraphy of the Late Pleistocene loesses of Kansas: ern Iowa: Geol. Soc. America Bull., v. 65, Jour. Geology, v. 59, no. 4, p. 287-305. p. 443-456.

Glacial Map of North America, 1945: Geol. 1954b, Farmdale drift: Science, v. 119, no. Soc. America, New York. 3098, p. 693-694. Guthrie, Ossian, 1895, Report of Illinois Board of Shaw, James, 1873, Reports on counties in north- World's Fair Commissioners, World's Colum- western Illinois: in Worthen et al.. Geology and bian Exposition 1893: H. W. Rokker, Spring- Paleontology, Geol. Survev of Illinois, v. V, field, Illinois, p. 305. p. 1-201. Horberg, Leland, 1953, Pleistocene deposits be- Shepard, F. p., 1954, Nomenclature based on sand- low the Wisconsin drift in northeastern Illi- silt-clay ratios: Jour. Sedimentary Petrology, nois: Illinois Geol. Survey Rept. Inv. 165, 61 p. V. 24, p. 151-158. Knappen, R. S., 1926, Geology and mineral re- sources of the Dixon quadrangle: Illinois Geol. Shepps, V. C, 1953, Correlation of tills of north- Survey Bull. 49, 141 p. eastern Ohio by size analysis: Jour. Sedimen- tary Petrology, v. 23, p. 34-48. Krumbein, W. C, and Pettijohn, F. J., 1938, Manual of sedimentary petrology: Appleton- Trowbridge, A. C, and Shaw, E. W., 1916, Century and Co., New York. Geology of the Galena and Elizabeth quad- Leighton, M. M., 1923, The differentiation of the rangles: Illinois Geol. Survey Bull. 26, 233 p. drift sheets of northwestern Illinois: Jour. U. S. Dept. Agric, 1938, Soils and Men: Yearbook Geology, v. 31, no. p. 265-281. 4, of Agriculture 1938.

, 1926, A notable type Pleistocene section, White, G. W., 1952, Discontinuities in till sheets the Farm Creek exposure near Peoria, Illinois: (Abstract): Geol. Soc. America Bull., v. 63, Jour. Geology, v. 34, no. 2, p. 167-174. p. 1312.

, Ekblaw, G. E., and Horberg, C. L., 1948,

Physiographic divisions of Illinois: Jour. , 1953, Sangamon soil and early Wisconsin Geology, v. 56, no. 1, p. 16-33. (Reprinted as loesses at Cleveland, Ohio: Am. Jour. Sci., v. Illinois Geol. Survey Rept. Inv. 129.) 251, p. 362-368. Illinois State Geological Survey, Report of Investigations 198

25 p., 2 pis., 3 figs., 1956