.Ifi^O'f STATE Q E0L0G|CAL 
 
 -SURVEY 
 
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5 \ 
 
 ILLINOIS STATS GEOLOGICAL SURVEY 
 Urbana, Illinois 
 John C. Frye, Chisf 
 
 ^ILLINOIS 
 
 INDUSTRIAL MINERALS NOTES 
 
 Number 8, August 1/ 1958 
 
 ORIGIN OF ILLINOIS SAND AMD GRAVEL DEPOSITS 
 J. E. Lamar and H. B. Willman 
 
 Introduction 
 
 Sand and gravel are important mineral resources and occur at many- 
 places in Illinois. Numerous questions have been asked from time to time by 
 members of the industry producing these materials regarding hov the various 
 kinds of sand and gravel deposits have been formed. This is a complex story. 
 To tell it simply and briefly requires the omission of many details regarding 
 the manner in which many special types of deposits were formed. Neverthe- 
 less, certain broad features that pertain to the majority of deposits can be 
 outlined. This is done below, with the aid of diagrammatic drawings, in the 
 hope that it will explain some of the major ways in which the State * s sand 
 and gravel deposits originated. 
 
 The Formation of Illinois Sand and Gravel' Deposits 
 
 The sand and gravel deposits of Illinois-"- are directly or indi- 
 rectly related to glaciers. Glaciers extended southward from Canada into 
 the State during each of four major intervals of glaciation. Most of the 
 economically important deposits of sand and gravel were formed during the 
 last two glaciations, the older of which is called the Illinoian and the 
 younger the Wisconsin. Figure 1 shows the area covered by the Illinoian 
 and Wisconsin glaciers . The glaciers may have been as much as several 
 thousand feet thick. 
 
 Excluding certain deposits of sand and chert gravel in western and ex- 
 treme southern Illinois. 
 
 ILLINOIS GEOLOGICAL 
 SURVEY LIBRARY 
 
-2- 
 
 Fig. 1. - Areas covered "by Wisconsin and Illinoian glaciers. 
 Areas marked "U" were not glaciated. Modified from 
 maps "by G. E. Ekblaw (Glacial geology of northeastern 
 Illinois, 1957) and J. M. Ueller (Geologic Map of 
 Illinois, 19^5). 
 
 The glaciers carried embedded in their ice enormous amounts of clay, 
 silt, sand, and gravel they had picked up from the areas over which they 
 passed. The formation of useful sand and gravel deposits involved a separ- 
 ation of the sand and gravel from this mixture of materials . The sorting of 
 the glacial debris into deposits of materials of different sizes was accom- 
 plished by running water which came largely from the melting of the glacial 
 ice. 
 
 The ice in a glacier flows continuously forward. The front of the 
 glacier moves forward when the ice advances more rapidly than it melts. The 
 front melts hack, or retreats, when melting exceeds the rate of advance. 
 
"J" 
 
 <r 
 
 GLACIER 
 
 ICE ADVANCE 
 
 FRONT OF GIACIER MOVES FORWARD 
 
 Fig. 2. - Diagrammatic cross section shoving glacier moving forward 
 faster than it melts. As a result the front of the glacier 
 moves forward. 
 
 GLACIER 
 
 MELTING 
 BACK 
 
 ICE ADVANCE 
 
 ■O FRONT OF GLACIER RETREATS 
 
 Fig. 3- - Diagrammatic cross section showing ice melting faster than 
 glacier moves forward. As a result the front of the glacier 
 moves back. 
 
 GLACIER 
 
 MELTING 
 
 v_ 
 
 FRONT OF GLACIER REMAINS STATIONARY 
 
 Fig. k. - Diagrammatic cross section of stationary front resulting 
 when glacier melts as fast as it moves forward. 
 
 Under some conditions , the ice movement stops and the ice melts, largely from 
 the top down. The conditions under which a glacier's front advances, retreats, 
 or remains stationary are shown in figures 2, 3, and k. 
 
-4- 
 
 When the advance and melting back of glacial ice are about equal 
 (fig. k) , the front of the ice remains stationary or fluctuates within a nar- 
 row zone. The debris freed from the melting ice therefore piles up into a 
 band of hills and ridges along the front of the ice (figs. 5 and 6). Such a 
 band of hills and ridges is called an end moraine and may extend for long 
 distances across country. Many end moraines are from one to several miles 
 wide. Most hills of the moraine consist largely of pebbly, silty clay, called 
 till, but some moraines are very gravelly. The gravel deposits of end moraines 
 are commonly irregularly bedded and poorly sorted (fig. 7) and in many places 
 contain boulders as well as beds, lenses, and balls of clay. 
 
 When the front of a glacier remains stationary, melt water from the 
 ice may deposit aprons of sand and gravel, called outwash plains, in front of 
 the glacier or its end moraine (figs. 8 and 9)« The dimensions of outwash 
 plains are often to be measured in miles. They are important commercial 
 sources of gravel and sand in some parts of Illinois. Gravel deposits in out- 
 wash plains generally are regularly bedded (fig. 10) and commonly grade from 
 gravel near the moraine to sand at greater distances. 
 
 In many situations much of the melt water with its load of rod: debris 
 was concentrated in valleys leading away from the front of the glacier. As this 
 water moved down the valleys it sorted its load and dropped the coarser gravel 
 and sand first, then the finer gravel and sand, then sand, then finally silt 
 and clay (fig. 11). Such deposits are called valley trains and may be many 
 miles in length. 
 
 As the rate of glacial melting varied, the coarseness of the mate- 
 rials deposited at a given place also varied. Nevertheless, the valley-train 
 gravel deposits generally are regularly bedded (fig. 10) and better sorted than 
 other deposits. 
 
 With the retreat of the glacier, rivers cut into and partly removed 
 the valley-train deposits, as shown in figures 12 and 13 . Remnants of the 
 valley trains remain as terraces or high bottomlands above the level of present- 
 day floods. At some places a later advance of the glacier built another valley- 
 train deposit in the valley (fig. 14), and, when this was cut into by a later 
 stream, remnants of the second deposit were left in the valley as lower sand 
 and gravel terraces (fig. 15). 
 
 Valley-train deposits are one of the principal sources of sand and 
 gravel in Illinois and are found along most of the rivers and many of their 
 major tributaries. 
 
 Streams of melt water flowing on the ice or in channels in the ice 
 deposited sand and gravel where they spilled from the margin of the ice or in 
 crevasses in the ice. When the ice melted, such a deposit remained as a hill, 
 called a kame (fig. 16) . Karnes are the source of comparatively small amounts 
 of sand and gravel but are worked in many small pits. They are found commonly 
 in association with end moraines. As a rule the material in kames is irregu- 
 larly bedded (fig. 7). 
 
END 
 MORAINE 
 
 -5- 
 
 Fig. 5- " Cross section of glacier with end moraine 
 in front of it. 
 
 
 
 A y 
 
 \. „ _ 
 
 Fig. 6. - Bird's-eye view of 
 a glacier and the hills and 
 ridges comprising its end 
 moraine. Some of the hills 
 may contain sand and gravel. 
 
 
 HILLS 
 AND 
 RIDGED 
 COMPRISING 
 AN END MORAINE 
 
 Fig. 7* - Irregularly "bedded deposit of sand and gravel. 
 This type of bedding is likely to be found in kames 
 and eskers. 
 
•6- 
 
 Fig. 8. - Bird's-eye view 
 of the formation of 
 an outwash plain. 
 
 CLAY AND 
 SILT 
 
 WATER FLOWS AWAY 
 
 FROM GLACIER SORTING 
 ROCK DEBRIS INTO 
 VARIOUS SIZES 
 
 Or 
 
 SAND 
 
 D-rTTX Cnrrd 
 
 SAND AND 
 GRAVEL 
 
 O 
 
 GRAVI 
 AND SAND 
 
 jjonru?- 
 
 MELTING MTJCH 
 
 ROCK DEBRIS FREED 
 
 GLACIER 
 
 Fig. 9. - Formation of an outvash plain of sand and gravel in front of a glacier 
 
 d . O '. r. ' •_ O 
 
 O'O'O* Ofb'O'O'O'O'O 
 
 b <» 
 
 o 
 
 o 
 
 <3- 
 
 o - o 
 
 c 
 
 c 
 o 
 
 <2 
 
 Fig. 10. Regularly "bedded deposit of sand and gravel. This type of bedding is 
 often found in valley-train and outwash deposits. 
 
-7- 
 
 FRONT OF GLACIER 
 
 u 1 1 1 iPM 
 
 Water from 
 melting glacier flows 
 into valleys in 
 
 The water 
 carries a load of rock 
 debris that it sorts and de- - r. 
 
 / y- front of ice . 
 
 posits roughly as shown. 
 The deposit so made is 
 called a valley train. 
 
 CLAY AND SILT 
 
 X 
 
 *"" 
 
 £ = gravel 
 
 1 /x c 
 
 S = sand 
 
 
 
 
 OIAY AMD 
 
 SILT 
 
 
 Fig. 11. - Bird's-eye view of glacier and valley trains 
 
 Gravel and sand also accumulated in stream channels in or under the 
 glacier. When the ice melted, the sand and gravel was left in a ridge, called 
 an esker, commonly a few hundred feet wide and as much as several miles long. 
 The materials in eskers usually,, are irregularly, "bedded (fig. 7). Eskers are 
 among the less common sources of gravel in Illinois. 
 
 In a few places, streams from melting glacial ice built deltas of 
 sand and gravel out into lakes . The waters of the lakes have long since 
 drained away but the deltas remain and are a local source of gravel. These 
 deltas are for the most part small but some have been worked as major sources 
 of sand and gravel. 
 
-8- 
 
 VALLEY TRAIN DEPOSITED 
 IN PRE-EXISTING VALLEY 
 
 <S 
 
 
 <--A 
 
 Fig. 12. - Cross section of valley train,, A, 
 
 STREAM HAS CUT INTO 
 VALLEY TRAIN 
 
 Fig. 13. - The valley train has been cut into and partly worn away 
 "by a later stream. Terraces of sand and gravel result. 
 
 SECOND VALLEY TRAIN 
 DEPOSITED 
 
 Fig. 1^. - Another valley train (D) lias been deposited. 
 
 STREAM HAS CUT INTO 
 SECOND VALLEY TRAIN 
 
 Fig. 15. - The second valley train has been partially eroded 
 producing a second set of terraces. 
 
-9- 
 
 STREAMS FLOWING INTO 
 CREVASSE BUILD UP 
 
 DEPOSIT OF GRAVEL AND SAND 
 
 FRONT OF 
 
 ULlXjJJJ- 
 
 GLACIER 
 
 CREVASSE 
 
 JU-Jj 
 
 if / I \ GLACIER 
 
 FRONT OF 
 
 HAS 
 MELTED BACK 
 
 HILL' OF GRAVEL 
 AND SAND, CALLED 
 A KAME 
 
 Fig. 16. - Front of glacier with a re-entrant or crevasse in its 
 margin. Water from the melting ice at the surface of the glacier 
 drains into the crevasse, carrying with it rock debris. The 
 gravel and sand "build up in the bottom of the crevasse. The clay 
 and silt are carried away. When the front of the glacier retreats 
 (B), the crevasse deposit is left as a rounded hill of sand and 
 gravel, called a kame. 
 
 Modern streams cutting through the various types of glacial deposits 
 commonly deposit some of the sand and gravel in or near their channels. Such 
 deposits generally are comparatively small but some of them have been used as 
 sources of sand and gravel. In favorable places the supply is renewed with 
 each succeeding interval of high water. 
 
 Huge areas of sand, chiefly in sand dunes, occur in many places in 
 Il lino is, including the regions near Havana, Watseka, Kankakee, Prophetstown, 
 Geneseo, Amboy, and Keithsburg. Most of these dunes have been blown by the 
 wind from large areas of sand along the floodways of ancient glacial melt 
 waters .