State of Illinois 
 Department of Registration and Education 
 STATE GEOLOGICAL SURVEY DIVISION 
 John C. Frye, Chief 
 
 
 S/t 
 
 m 
 
 i. 
 
 GEOLOGICAL SCIENCE FIELD TRIP 
 
 Sponsored by 
 
 ILLINOIS STATE GEOLOGICAL SURVEY 
 
 \ m~\ e 
 
 Stephenson and Jo Daviess Counties 
 Lena, Elizabeth and Galena Quadrangles 
 
 Leaders 
 Edgar Odom, George M. Wilson, Guy Dow 
 
 Urbana, Illinois 
 September 9,1961 
 
 GUIDE LEAFLET 19 6 ID 
 
 HOST: Lena-Wins low High School 
 
THE LENA GEOLOGICAL SCIENCE FIELD TRIP 
 
 ITINERARY 
 
 Suggestion: Have someone read the guide as we 
 travel through the countryside so 
 that the driver will be able to 
 learn the geology of the area, also. 
 
 Abstract 
 
 Lena is situated on the glaciated plain adja- 
 cent to the non-glaciated area of northwestern Illinois. 
 The glacial sequence includes Winnebago Drift, lake silts 
 and sands of Altonian Age, and loess of Woodfordian Age. 
 
 The Galena Dolomite, Maquoketa Shale (Ordovi- 
 cian) and the Niagaran Dolomite (Silurian) compose the 
 bedrock formations. In the non-glaciated area difference 
 of these formations in resistance to weathering accounts 
 for a marked bedrock control of the topography, charac- 
 terized by mounds, narrow ridges, and sweeping slopes. 
 The mounds are capped by Silurian dolomite. Slopes are 
 underlain by weak Maquoketa shale. The mounds and ridges 
 rise to approximately the same elevation. These summits 
 form a surface correlated with the Dodgeville Peneplain 
 of Tertiary Age. 
 
 The trip includes a visit to the zinc and lead 
 district centered around Galena, Jo Daviess County, where 
 specimens of galena, sphalerite, pyrite, calcite, limonite 
 and other less abundant lead-carbonate minerals may be 
 found. 
 
 Drainage derangement caused by glacial action is 
 superbly illustrated by Apple River. During pre -Al- 
 tonian time, Apple River flowed to the southeast. It 
 now flows southwest through a deep gorge eroded when the 
 Altonian Glacier blocked the southeast course. 
 
 0.0 0.0 Assemble at front of Lena-Winslow High School, heading west on 
 Freemont Street. 
 
 0.1 0.1 STOP. Turn right on Lena Street. 
 
 O.k 0.5 STOP. North Schyler Street. Continue straight ahead. 
 
 0,k 0.9 SLOW. Turn right on Lake Le-aqua-na Road. 
 
 1.1 2.0 Galena Dolomite outcropping in road cut on right and left. 
 
 0.7 2.7 Galena Dolomite on right and left. The dolomite is capped by x ^ 
 
 a thin cover of glacial till and loess. cN^ Q ^t> 
 
 ¥•' 
 
 s* 
 
Digitized by the Internet Archive 
 
 in 2012 with funding from 
 
 University of Illinois Urbana-Champaign 
 
 http://archive.org/details/guideleaflet61odom 
 
- 2 - 
 
 Summary of The Pleistocene History of Illinois 
 
 Tens and hundreds of thousands of years ago most of Illinois, 
 together with most of northern North America, was covered by huge glaciers. 
 These glaciers expanded from centers in central and eastern Canada. They 
 developed when the mean annual temperatures were somewhat lower than now, so 
 that not all of the snow that fell during the winters melted during the sum- 
 mers. The snow residues accumulated year after year until a sheet of ice 
 was formed so thick that as a result of its weight, it began to flow out- 
 ward, carrying with it the soil and rocks on which it rested and over which 
 it moved. The process continued until the glacier extended into our country 
 as far south as Missouri and Ohio Rivers. 
 
 Moderation of temperatures halted the glacier. For a while the 
 melting of the ice balanced its accumulation and expansion, so that its 
 margin remained stationary. Later the melting exceeded the accumulation 
 and expansion, and the ice-front gradually melted back until the glacier 
 disappeared entirely. 
 
 It is now commonly known that there were four major periods of 
 glaciation during the Pleistocene or Great Ice Age (see accompanying illus- 
 tration), and that between each there was a long interglacial period in 
 which conditions were much as they are today. It is also commonly known 
 that during each major glaciation there were a number of retreats and re- 
 advances. This was particularly true during the last or Wisconsinan glacial 
 stage. 
 
 A complete discussion of Pleistocene (Ice Age) history would 
 require a sizable volume, in fact, the story is still not fully known. 
 Present facts indicate that this era of geologic history began about one 
 million years ago when the Nebraskan glacier advanced over the area. This 
 oldest glacier is named Nebraskan because the typical Nebraskan glacial 
 deposits are best developed in the state of Nebraska. Nebraskan deposits 
 are not abundant in Illinois probably because weathering during the Aftonian 
 interglacial stage after the retreat of the Nebraskan glacier destroyed 
 them. 
 
 The next glacial episode produced the Kansan glacier which again 
 advanced from the west. Thick deposits of till and outwash sand and gravel 
 were deposited in Illinois when the Kansan glacier withered away. 
 
 The Kansan stage was followed by the Yarmouthian interglacial 
 stage during which erosion carved valleys and hills in the Kansan deposits. 
 
 The third glacial stage, the Illinoian, is important to the 
 residents of Illinois. It covered 80 percent of Illinois, reaching south- 
 ward to Carbondale and Harrisburg. In contrast to the preceding glacial 
 advances, the Illinoian came from the east rather than the west. 
 
 After several thousands of years, climatic conditions caused the 
 melting away of the Illinoian ice sheet. During this warm stage, the upper 
 part of the Illinoian till was weathered and soil developed, just as in the 
 case of the preceding Yarmouthian interval. However, this action did not 
 take place to the degree it did during the Yarmouthian, so that the post- 
 
- 3 - 
 
 Illinoian (Sangaraonian) interval is estimated to have lasted only about 150,000 
 years. The Sangamon soil resembles present day soils in color, texture, and 
 depth of development. This fact lends support to theory that the climate ex- 
 isting during interglacial times was similar to the present climate. The 
 theory that we are living in an interglacial interval has been advocated by 
 numerous glacial geologists. We should not brush this thought aside for it 
 is estimated that a drop of only five degrees in the average annual tempera- 
 ture would bring another glacier down upon us. 
 
 The last and most recent glacial stage was the Wisconsinan. This 
 glacier advanced southward from the Lake Michigan Basin to the present sites 
 of Shelbyville, Charleston, and Peoria where it formed a terminal moraine that 
 geologists call the Shelbyville Moraine. The Shelbyville Moraine was built by 
 the Wisconsinan glacier approximately 20,000 years ago. 
 
 As the Wisconsinan Glacier retreated, withdrawals and readvances 
 created a complex sequence of deposits in northeastern Illinois, the most out- 
 standing of which are the moraines. More than fifty separate moraines were 
 formed by this glacier in Illinois alone. The major ones are shown on the 
 accompanying glacial map of northeastern Illinois. 
 
 To appreciate the significance of the Pleistocene history and its 
 effects on the inhabitants of Illinois, we need to consider only the rich soils 
 formed from the glacial deposits, and the abundant deposits of sand and gravel 
 of glacial origin in our state. We definitely would not have these treasures 
 had the glaciers missed Illinois. 
 
 In this discussion are a number of terms that are unfamiliar to many 
 persons. The following discussion will clarify many of these terms as well as 
 explain some of the various types of glacial deposits found in Illinois. 
 
 As the glacier melted, all of the soil and rocks which it had picked 
 up as it advanced were released. Some of this material or drift was deposited 
 in place as the ice melted. Such material consists of a thorough mixture of all 
 kinds and sizes of rocks and is known as till . Some of the glacial drift was 
 washed out with the melt-waters. The coarsest out wash material was deposited 
 nearest the ice- front and gradually finer material farther away. The finest 
 clay may have been carried all the way to the ocean. Where the outwash material 
 was spread widely in front of the glacier it forms an outwash-plain ; where it 
 was restricted to the river valleys it forms valley-trains . 
 
 As shown on the accompanying map, there are many moraines in Illinois. 
 The moraine represents the accumulation of drift at the ice-margin while the 
 advance and melting were essentially in balance, when more and more material 
 was being brought to the edge of the advancing ice. 
 
 With the exception of the Shelbyville moraine, which marks the maxi- 
 mum advance of the Wisconsinan glacier, each marks the position to which the 
 ice-front readvanced after a recession of unknown distance from the position 
 it had previously attained. 
 
T,f 
 
The surface relief of moraines is generally greater than that 
 of the drift-plains . It is generally referred to as swell -and -swale, 
 but on some moraines it is termed knob -and -kettle topography. Generally, 
 the outer slope and edge of the moraines is interrupted by valleys and 
 re-entrant angles marking the courses of glacial rivers. At some places, 
 there are gaps in the moraines where subglacial streams presumably 
 carried away most of the drift. Subglacial valleys may be distinguished 
 from valleys developed by erosion in postglacial time by the fact that 
 morainic topography occurs all the way down the valley slopes. 
 
 As a glacier began to recede, melt-water gradually accumulated 
 in local ponds or lakelets between the ice-front and the moraine last 
 formed, except where there were channels through the moraine through which 
 it could drain. Where such drainage channels are absent, it may be pre- 
 sumed that as the ice-front continued to recede, the local ponds and lake- 
 lets gradually merged into one large lake which persisted until the glacier 
 uncovered some passage or until some river eroded a channel through which 
 the lake could be drained. 
 
 At times, especailly in the winters, the outwash -plains and 
 valley-trains were exposed as the melt-waters subsided, the wind picked 
 up silt and fine sand from their surfaces, blew it across the country, 
 and dropped it to form deposits of what is known as loess. Glacial loess 
 mantles most of Illinois. Near the large river valleys it may be as much 
 as 60 to 80 feet thick. Far from the valleys it may be measured only in 
 inches, if it can be identified at all. 
 
 0.5 3.2 STOP 1. Quarry in Galena Dolomite. 
 
 The Galena Formation of Middle Ordovician Age is exposed extensively 
 in northwestern Illinois. Over most of the area it is a dolomite, that is, 
 it consists of calcium magnesium carbonate (CaMg C0 3 ) in contrast to- limestone 
 which is mostly calcium carbonate (CaC0 3 ). In some places through northwestern 
 Illinois the formation is as much as 225 feet thick. 
 
 The Galena is divided into three members . The lower Prosser Member 
 is 150 feet thick and consists of a lower cherty portion 105 feet thick and an 
 upper non-cherty portion 45 feet thick. Overlying the Prosser is the 
 Stewartville Member, a thick-bedded dolomite except in the upper 10 feet 
 where it becomes thinner -bedded. The Dubuque Member, the upper 45 feet of 
 the Galena Dolomite, is in general thin-bedded, argillaceous, and has many 
 shale partings. 
 
 Within the Galena Formation are two zones of Receptaculite s oweni , 
 a fossil believed to be a type of sponge. This fossil is found only in the 
 Galena Formation and serves to differentiate the Galena Formation from those 
 above and below. Prominent Receptaculites zones occur in the Prosser Member 
 and in the Stewartville Member. 
 
 Near the top of this quarry is a zone of Receptaculites . It is 
 believed to be the upper zone that occurs near the base of the Stewartville 
 
 Member . 
 
- 5 - 
 
 0.4 3.6 Lake Le-aqua-na State Park on left. 
 
 0.9 4.6 Glacial till of Altonian age exposed in road cut on right and 
 left. 
 
 The glacial geology of northwestern Illinois has engaged the 
 attention of geologists for more than a century. The first 
 extensive study of these deposits was by Leverett (1899). He 
 states, "In the portion of Illinois north from the latitude of 
 Rock Island, the Iowan drift occupies a large part of the interval 
 between the glacial boundary and the outer moraine of the Wisconsin 
 series. A drift, tentatively referred to the Illinoian, forms the 
 surface sheet in the region in Stephenson County and part of Winne- 
 bago, Ogle, Whiteside, Carroll, and Jo Daviess Counties." Leverett 
 used the term "Iowan'' to denote a separate glacial stage occurring 
 between the Wisconsinan and the Illinoian. 
 
 In 1923, Dr. Morris M. Leighton in his studies of the glacial 
 deposits of northwestern Illinois defined the Belvidere and the 
 Green River Lobes (see fig.). He thought the Belvidere lobe was 
 early Tazewell (Shelbyville) and the Green River lobe Iowan, a 
 substage of the Wisconsinan and older than the Tazewell. All the 
 till deposits north and northwest of the Belvidere and Green River 
 lobes were regarded by Leighton as Illinoian in age, although he 
 recognized that they were younger than the Illinoian in southern 
 Illinois. 
 
 In 1954, Dr. Paul Shaffer extended Leighton' s Belvidere lobe 
 into eastern Iowa and defined it as the Shelbyville of early 
 Tazewell age. Again, the drift north of the Shelbyville boundary 
 was regarded as Illinoian in age. In 1956, Shaffer continued 
 studies of the glacial deposits of northwestern Illinois. His 
 proposal that the drift long considered Illinoian was deposited 
 during the Farmdale Substage of the Wisconsinan was published in 
 Illinois State Geological Survey Report of Investigation 198, 
 "Farmdale Drift in Northwestern Illinois." The Farmdale was con- 
 sidered to be the first substage of the Wisconsinan Stage. This 
 discovery correlated well with loess deposits recognized by Leighton 
 and others along the Illinois and Ohio Valleys. Thus, the till de- 
 posits of northwestern Illinois long considered Illinoian were 
 proven to be Wisconsinan. Now it is assumed there are few Illinoian 
 glacial deposits in extreme northwestern Illinois. 
 
 In most geologic problems new evidence often changes old ideas 
 and concepts. In 1960, Drs. Frye and Willman revised the classi- 
 fication of the Wisconsinan in the Lake Michigan lobe. This re- 
 classification compared with the old is presented in the following 
 illustration from Illinois State Geological Survey Circular 285, 
 "Classification of the Wisconsinan stage in the Lake Michigan 
 Glacial Lobe." 
 
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- 7 - 
 
 RECENT STAGE 
 
 oa 
 
 5,ooo 
 
 (Alluvium) 
 
 VALDERAN 
 SUBSTAGE 
 
 (.Alluvium) 
 
 11,000 __ 
 
 -THOCEEEKAK- SUBSTAGE- 
 12,500 
 
 VALDERS 
 
 3 m 
 O CO 
 
 8 W & 
 
 i .Lake Border 
 
 moraine 
 
 ,_/ — "~ -Valparaiso moraines 
 .._f-f _ Bloomington-Normal moraines 
 
 22,000 
 
 FARMDALIAN 
 SUBSTAGE 
 
 28,000 
 
 Shelbyville moraines 
 ^' ^ j^^ Loesa^ 
 
 Farmdale 
 silt and peat 
 
 FORMER CLASSIFICATION 
 
 / 
 
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 f 
 
 
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 3 CO 
 
 co 
 
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 03 
 
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 05 
 
 Winnebago drift 
 
 (Inferred southern limit 
 of glacial ice in the 
 Lake Michigan lobe.) 
 
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 mTi 5 
 
 50,000 - 70,000 
 
 SOIL -5 
 
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 From Illinois State Geological Survey Circular 285, 
 "Classification of the Wisconsinan Stage in the Lake 
 Michigan Glacial Lobe." 
 
 RECENT STAGE 
 
 1 
 
 CO 
 
 ft 
 
 8 
 
 o 
 
 St 
 
 MANKAT0 
 
 CARY 
 
 TAZEWELL 
 
 IOWAN 
 
 FARMDALE 
 
 SANGAMON 
 STAGE 
 
- 8 - 
 
 Ihe most important point m this reclassification in relation- 
 ship to the glacial deposits of the Lena area, is that they are 
 now considered even older than the Farmdale of Shaffer's and 
 belong to a separate glacial advance. Also, the length of the 
 Wisconsinan Stage has been extended some 20,000 years. 
 
 0.1 4.6 SLOW. Turn left, west. 
 
 0.2 4.8 Note the gently rolling nature of the topography. As we proceed 
 westward toward the nonglaciated area,. the topography "becomes 
 considerably sharper and more dissected. 
 
 0.3 5.1 T road north, continue ahead. 
 
 0.4 5.S Note prominent mound ahead (west). This is a bedrock high, one 
 of many in this region. 
 
 0.6 6.1 Drainage is to the southeast toward the Pecatonica River. 
 
 0.1 6.2 SLOW. Crossroad. Continue ahead. 
 
 0.5 6.7 Outcrop of Galena Dolomite on left. 
 
 0.7 7.4 SLOW. Turn left (southwest). 
 
 0.5 7.9 STOP. Turn right (northwest). Note excellent view toward the west. 
 
 0.6 8.5 STOP 2 . (Top of Waddams Hill) 
 
 Waddams Hill is one of a host of mounds in the field trip area. 
 On a clear day, a remarkable view of the surrounding flat glaciated 
 plain can be enjoyed. 
 
 Presumably, this hill was overridden by the Altonian glacier 
 which deposited the Winnebago Drift in northwestern Illinois. 
 
 This mound is held above the surrounding plain by resistant 
 Silurian dolomite. Euring the course of today's trip we will see 
 how the bedrock controls the topography of the region. In this 
 area the Galena and Silurian Dolomites form steep cliffs and the 
 softer, shaly Maquoketa Formation, forms gentle slopes and broad 
 terraces. In the area of Waddams Hill the topography has been 
 modified considerably by glaciation. 
 
 0.3 8.8 SLOW. Entering Waddams Grove. 
 
 0.8 9.6 SLOW. Railroad crossing. Extremely dangerous. 
 
 2.2 11.8 Note that the non-glaciated area is conspicuous on the western 
 horizon. 
 
 0.5 12.3 SLOW. Turn left on Apple River Canyon State Park Road. 
 
 0.3 12.6 Village of Nora % mile to north. <£* 
 
- 9 - 
 
 0.3 12.9 STOP. Continue ahead. 
 
 0.6 14.0 HOCe severe erosion in gully on right. 
 
 0.5 14.0 STOP. Highway 78. Continue ahead on Apple River Canyon road. 
 
 1.1 15.1 Approximate boundary between glaciated and non-glaciated area. 
 
 0.3 15.4 SLOW. Narrow bridge. 
 
 0.7 16.1 Crossroad. 
 
 0.3 16.4 SLOW. Begin descent into Apple River Canyou. 
 
 0.1 16.5 Note outcrop of Galena Dolomite on the left. 
 
 0.8 17.3 SLOW. Sharp turn. 
 
 0.1 17.4 Entering Apple River Canyon State Park. 
 
 0.3 17.7 Turn right (north). 
 
 °-° *7.7 STOP 3. Apple River Canyon. 
 
 Apple River is an excellent example of the effects of glaciation 
 upon drainage. Before the Wisconsinan Glacial stage Apple River 
 drained south along the valley of the South Fork of Apple River 
 past Stockton and along the Silurian Escarpment to the valley of 
 Yellow Creek, thence into the Pecatonica River south of Freeport . 
 
 When the Wisconsinan ice invaded the area during the Altonian 
 Substage, South Fork was dammed near Stockton. The waters of 
 Apple River spilled over the low divide southwest of the park and 
 carved out the deep Apple River Canyon. The canyon is nearly 
 200 feet deep, trends in a nearly straight NE-SW direction, and 
 is over 4 miles long. The canyon is eroded in the Galena Dolomite. 
 
 The pre-Altonian drainage can be interpreted as follows: 
 Before the advance of the glacier there were two drainage systems: 
 Apple River including Mill Creek, Holts Branch, Coon Creek; and 
 the present Apple. River as far northeast as the mouth of Apple 
 River Canyon constituted one drainage system. The valleys now 
 occupied by West Fork and South Fork with several small tributaries 
 constituted another drainage system. Between the two systems was 
 a divide where the main canyon is now located. 
 
 Note that South Fork now drains to the north, a reversal of 
 its former course. 
 
 A more detailed summary of the history of Apple River Canyon 
 is contained in Illinois Geology Survey Bulletin No. 26, "Geology 
 of the Galena and Elizabeth Quadrangles. 1 ' 
 
- 10 - 
 
 0.0 17.7 STOP 4 . LUNCH. Apple River Canyon Picnic Area. 
 
 0.7 18.4 Turn left. 
 
 0.2 18.6 Turn right. 
 
 0.1 18.7 End of blacktop road. 
 
 0.5 19.2 SLOW. Turn sharp left (west). 
 
 0.2 19.4 Turn sharp right (north). 
 
 1.1 20.5 Crossroad. Continue ahead. 
 
 0.2 20.7 Note high hill on left. 
 
 0.2 20.9 Galena Dolomite exposed in ditch on right and left. 
 
 0.6 21.5 STOP. Turn left on blacktop road to Apple River. 
 
 1.1 22.6 STOP 5 . Outcrop of Maquoketa Shale. 
 
 The Maquoketa Formation in the non-glaciated area is approxi- 
 mately 200 feet thick. Maquoketa consists of shale and interbedded 
 dolomites. This is one of the best outcrops of Maquoketa Formation 
 in the Apple River area, but even here it is poorly exposed. The 
 shales of the Maquoketa weather very rapidly to broad slopes, while 
 the dolomites of the Galena Formation and the Niagaran Series are 
 resistant and form steep cliffs or flat terraces. 
 
 Extensive flat areas and long sweeping slopes are characteris- 
 tic features of the topography of the non-glaciated area. These 
 reflect the bedrock control of the topography, directly traceable 
 to the underlying rock strata. 
 
 The most conspicuous flat is the top of the mounds and sharp 
 ridges in the area. This flat is formed on the Silurian dolomites 
 of the Niagaran Series. The second flat is lower than the Niagaran 
 Dolomite and is situated at the top of the Galena Dolomite at ap- 
 proximately 150 feet below the Niagaran flat. The present streams 
 are now entrenched 20 or 30 feet below the Galena flat. 
 
 In a few spots, terraces are present that correlate with resis- 
 tant dolomite beds in the Maquoketa Formation. Throughout the 
 region, however, the highest hills, regardless of the rock composing 
 them, all rise from 1,100 to 1,200 feet high. These crests are be- 
 lieved to be remnants of what was once a continuous plain (peneplain) 
 formed when the region lay lower than it does today. At a past time, 
 long-acting erosion cut away still higher hills and reduced the re- 
 gion to this plain surface. Later the region was again uplifted, 
 and erosion is actively cutting it down and dissecting it into a 
 maze of narrow ridges and deep valleys. If nothing intervenes, a 
 new peneplain will be formed slightly above the level of the Missis- 
 sippi River. 
 
- 11 - 
 
 The region preserves this long erosional history because 
 it was never covered by glacial ice. This non-glaciated region, 
 entirely surrounded by glaciated country, is world-famous as 
 'The Driftless Area.' This is actually an incorrect name for 
 the area is not driftless, but non-glaciated. Drift is the 
 term used by geologists to designate all types of glacial de- 
 posits such as till, loess, outwash sand and gracel, etc. It 
 is thought that this region was never glaciated, but it cer- 
 tainly isn't driftless. There are thick deposits of loess, a 
 wind-blown silt of glacial origin, throughout the region. 
 
 0.3 22.9 SLOW. Entering Apple River 
 
 0.8 23.7 Galena Dolomite outcrop on left. 
 
 0.2 23.9 SLOW. Turn left on Woodbine Road. 
 
 1.6 25.5 Bridge crossing Apple River. 
 
 1.7 27.2 Woodbine Road turns left. Continue straight ahead on road to 
 
 Summit of Sumner Hill. 
 0.3 27.5 Ascending Sumner Hill. 
 
 0.3 27.8 Note rubble of Silurian dolomite in roadcut on right. 
 
 0.1 27.9 STOP 6. Crest of Sumner Hill 
 
 From this vantage point one can enjoy an excellent view of 
 the non- glaciated area. Like the other mounds in the area Sumner 
 Hill is capped by Niagaran dolomite. This dolomite contains white 
 chert which is left behind as a residue as weathering decomposes 
 the dolomite. Residual chert can be seen in the road cuts near the 
 top of the hill. The hill also is capped by a mantle of loess. 
 In most instances, loess is the parent material of the fertile 
 soils of the area. We will examine a soil profile developed in 
 loess at the next stop. 
 
 0.2 28.1 Maquoketa Formation outcrops in ditch on right along slope of 
 
 Sumner Hill. 
 0.8 28.9 Galena Dolomite outcropping on right. 
 0.1 29.0 STOP 7. Soil Profile Developed in Loess. 
 
 The soil profile is approximately as follows: A zone, dark 
 colored, rich in organic matter 6-8 inches; B zone, chocolate 
 brown, oxidized 4-5 feet; Galena Dolomite 4-5 feet. 
 
 The soils of Jo Daviess County are very fertile. The parent 
 material of these soils is not the underlying bedrock formation, 
 but loess that was deposited over the countryside by wind during 
 the Pleistocene, mainly during the last stage of Glaciation. Loess 
 is nothing more than fine rock flour of silt size. It is rich in 
 variety of minerals which upon weathering, yield nutrients 
 essential for plant growth. Most of the soils of Illinois are 
 developed in loess. 
 
(I '.:'/■ 
 
- 12 - 
 
 We can never overemphasize the importance of the rich soils 
 in the United States, particularly in the Midwest. Soils vary 
 greatly in richness and character from place to place. Yet, in 
 mature soils we can recognize zones that are common to all. The 
 zonal effect comes about because the four major weathering process- 
 es progress at different rates, although all of them depend on the 
 downward movement of groundwater. The processes, listed according 
 to their rate of progress and beginning with the most rapid, are 
 (1) oxidation; (2) leaching of carbonates; (3) decomposition of 
 more resistant minerals; and (4) accumulation of humus. 
 
 In the A zone, in which humus material from decaying plants 
 has accumulated, we find the rock minerals oxidized, leached, and 
 decomposed. In the upper part of the B zone the rock minerals are 
 only oxidized (shown by reddish or yellowish color caused by 
 oxidation of iron minerals). The leached zone is determined by 
 absence of carbonate rocks, such as limestone, and is revealed by 
 test 8 with a solution of hydrochloric acid. 
 
 0.3 29.3 SLOW. Turn right (north) 
 
 0.5 29.8 STOP. Turn left on blacktop road (west). For the next 15 miles 
 
 we will be treated to some of the finest scenery in Illinois. 
 1.6 31.4 Note the fascinating gentleness of the topography — interesting 
 
 and beautiful. 
 0.3 31.7 Galena Dolomite outcropping in roadcut on right. 
 0.6 32.3 Outcrop of Maquoketa formation on left. 
 0.4 32.7 Note the conspicuous development of the Galena Terrace about 20 to 
 
 30 feet above the present streams, and that the Galena Dolomite 
 
 outcrops repeatedly in roadcuts through this terrace. 
 
 0.6 33.3 SLOW. Crossroad. Village of Scales Mound 1 mile to north. 
 
 0.9 34.2 Scales Mound. Elevation -- 1104 feet. 
 
 Highest rock on mound is cherty Silurian Dolomite of Kankakee 
 Formation. Numerous small marine fossils and the honeycomb coral 
 Favosites occur in this rock. 
 
 Note how huge blocks of the dolomite have slumped down the 
 sides of the slope due to the weathering away of the soft Maquoketa 
 Shale which underlies the dolomite. Maquoketa outcrops occur in 
 the road cut . 
 
- 13 - 
 0.3 34.5 Note excellent view to west. In the far distance is the tailings 
 
 pile of the Vinegar Hill sphalerite mine. Continue ahead on 
 
 blacktop road. 
 0.5 35.0 Silurian Dolomite outcropping on right. Note that there is 
 
 considerable chert in the Silurian. 
 0.5 35.5 STOP 8. Scenic View. 
 0.5 36.0 From this point to Galena the road follows a northeast - southwest 
 
 trending ridge. The rocks exposed along the crest are Silurian 
 
 in age. 
 0.8 36.8 Note the contour farming that is practiced in the region. 
 1.0 37.8 Exposure of Silurian Dolomite on right. 
 1.5 39.3 Note slumping of loess on left. 
 
 0.5 39.8 Note tailings pile of Vinegar Hill Mine on far right. 
 1.9 41.7 SLOW. Steep Hill. 
 0.1 41.8 Quarry in Galena Dolomite on right. 
 0.6 42.4 Note conspicuous terrace on right. This is a depositional terrace 
 
 called the Mississippi Terrace formed when the valley of the 
 
 Galena River was filled during the Ice Age. This is a lake deposit, 
 0.3 42.7 Crossing Galena River. 
 0.6 43.3 Entering city of Galena 
 0.3 43.6 Note outcrop of Galena Dolomite on right and cave near top of 
 
 outcrop. 
 0.2 43.8 Turn right on Meker Street. 
 0.1 43.9 Cross Broadway, turn left on Bench Street. 
 0.1 44.0 Continue ahead on Bench Street. 
 0.1 44.1 STOP. Continue ahead on Bench Street. 
 
- 14 - 
 
 0.1 44.2 Note large buildings built of native stone, the Galena Dolomite. 
 
 0.2 44.4 Continue ahead on Bench Street. 
 
 0.2 44.6 STOP. Junction Highway 20. Turn left on U. S. Highway 20. 
 
 0.1 44.7 Bridge over railroad and Galena River. 
 
 0.2 44.9 SLOW. Turn right on Fourth Street. Continue ahead on blacktop 
 
 road. 
 
 0.3 45.2 Blacktop road ends. Continue ahead on gravel road. 
 
 0.7 45.9 Note outcrops of Galena Dolomite on right and left. 
 
 0.7 46.6 T-road South. Continue ahead. 
 
 2.6 49.2 STOP 9 . Tri-State Zinc Mining Company. 
 
 The Galena region is one of the oldest lead and zinc mining 
 regions in the United States. The following historical summary is 
 from 111. State Geol. Survey Report of Investigations 210, 
 "Crevice Lead-Zinc Deposits of Northwestern Illinois, 1959. i- 
 The shallow lead-zinc deposits of the Upper Mississippi Valley 
 mining region, of which those in northwestern Illinois are a 
 part, were the nation's principal source of the lead ore be- 
 tween 1820 and 1865. Peak production was reached in the years 
 1845 to 1847 when the annual output was 27,000 tons of lead 
 metal. As the known richer and shallower deposits were de- 
 pleted, as market conditions changed, and as various factors 
 adversely affected the supply of miners, lead mining declined 
 to a fraction of its former importance. At present nnly a 
 few hundred tons of ore are taken from the shallow deposits 
 each year. Zinc, gained almost exclusively from the larger deeper 
 flat and pitch deposits, is now the chief product of the district. 
 
 Galena and sphalerite ores occur in the region in two geologi- 
 cal settings, crevice fillings and flat and pitch deposits. The 
 crevice deposits are in a general way vertical joint- like fissures, 
 These ores are believed to have been deposited along solution 
 cavities in the Galena Dolomite. Thus far, crevice deposits have 
 been found only in the Galena Dolomite. 
 
 Flats are horizontal veins along bedding planes of the host 
 rock and pitches are veins along inclined fractures. The lead 
 and zinc deposits of northwestern Illinois are thoroughly covered 
 in Report of Investigations 210 which can be ordered from the 
 Survey for 25 cents. 
 
 You may find the following suite of minerals in the spoil 
 piles: Galena, Sphalerite, Pyrite, Marcasite, Calcite, Cerussite, 
 Angles tie, Smithsonite, and Limonite. 
 
- 15 
 
 The large tailings piles south of the Tri-State Zinc mill 
 are baren of ore minerals. This is host rock from which the 
 mineral has been separated. 
 
 End of trip. Thanks for coming. Next trip Georgetown, 
 September 23. 
 
...GENERALIZED GEQ LOG IC__CuLUMW _FOR_ J O DAVISS S_ AND jTjgmflSON JMUNTY 
 
 PEkIuOS 
 
 ERAS 
 
 0) 
 
 o 
 
 •H 
 
 1-1 
 
 •J 
 
 o 
 
 
 N 
 
 ■u 
 
 O 
 
 C 
 
 a 
 
 a> 
 
 <u 
 
 o 
 
 o 
 
 a> 
 
 
 OS 
 
 o 
 
 •H <U - 
 
 o ih <y 
 
 O T) -^ 
 
 £ E 
 
 <u 
 
 <4-l !-H 
 O «H 
 
 a> a. 
 op CD 
 
 EPOCHS 
 
 Quaternary 
 
 Tertiary 
 
 Cretaceous 
 
 Jurassic 
 
 Triassic 
 
 Pleistocene 
 
 Pliocene 
 
 Miocene 
 
 Oligocene 
 
 Eocene 
 
 Paleocene 
 
 REMARKS 
 
 wisconsinan glacial till 
 along east edge of area. 
 Loess deposits on upland & 
 alluvium in river valleys. 
 
 Present in southern Illinois 
 
 Present only in extreme 
 southern Illinois. 
 
 Not present in Illinois 
 
 Not present in Illinois 
 
 
 <u 
 
 
 <-M 
 
 o 
 
 •rl 
 
 •rt 
 
 t-i 
 
 O 
 
 
 N 
 
 •U 
 
 O 
 
 a 
 
 <u 
 
 <u 
 
 rH 
 
 •i-» 
 
 Cfl 
 
 O 
 
 (U 
 
 a 
 
 to 
 
 a 
 
 •rl 
 
 ■Q 
 •rl 
 
 X 
 
 I 
 
 Permian 
 
 Not present in area 
 
 c 
 
 CO 
 
 T-l 
 
 Oh 
 r** 
 
 r-l 
 U 
 
 CO 
 
 a 
 
 <+h to 
 o <u 
 
 <U to 
 
 to 
 CD 
 
 JJ 
 CtJ 
 M 
 
 CD 
 
 u 
 
 VI 
 0) 
 
 § 
 
 4-1 
 
 o 
 
 CD 
 00 
 
 Proterozoic 
 
 Archeozoic 
 
 I 
 
 J 
 
 Pennsylvanian 
 
 Not present in area 
 
 Mississippian 
 
 Not present in area 
 
 Devonian 
 
 Silurian 
 
 Ordovician 
 
 Not present in area 
 
 Cayugan 
 
 Not present in this area 
 
 Niagaran 
 
 Present only on highest 
 mounds 6outh and west of 
 JudLp_aj:£a_ ! 
 
 Alexandrian 
 
 Kankakee cherty dolomite 
 Edgewood thin-bedded earthy 
 dolomite in outcrop. 
 
 Cincinnatian 
 
 Maquoketa shale and shaly 
 limestone in outcrop, 
 
 Mohawkian 
 
 Galena dolomite - in outcrop 
 Decorah shale) 
 Platteville Is.) in wells 
 Glenwood ss.) 
 
 -fifaasyan 
 
 Prairie du Chie 
 
 St. Peter ss. - in wells 
 
 Shakopee dolomite) 
 a New Richmond ss. ) in wells 
 Oneota dolomite ) 
 
 _£ambxiaa_ 
 
 In dee p shells only. 
 
 Referred to as :; Pre -Cambrian" 
 time. 
 
 No data available 
 
Suggested References for further Study of the Geology of the 
 
 Field Trip Area, 
 
 1. Illinois State Geological Survey Bulletin 26, Geology and Geography of 
 the Galena and Elizabeth Quadrangles , 1916. 
 
 2. Illinois State Geological Survey Circular 214, "Geologic Structure Map 
 of the Northwestern Illlinois Zinc-Lead District," 1956. 
 
 3. Illinois State Geological Survey Bulletin 21, Lead and Zinc Deposits 
 of Northwestern Illinois , 1914. 
 
 4. Illinois State Geological Survey Report of Investigations 124, Geological 
 Structure of the Zinc-Lead District of Northwestern Illinois, 1947. 
 
 5. Illinois State Geological Survey Report of Investigations 116, Geological 
 Aspects of Prospecting and Areas for Prospecting in the Zinc-Lead District 
 of Northwestern Illinois , 1946. 
 
 6. Illinois State Geological Survey Report of Investigations 210, Crevice 
 Lead-Zinc Deposits of Northwestern Illinois , 1959. 
 
Time Tab!*, of Pit- 1 toc-.n<-:- oluciat'jon 
 
 (aft<=r M. M. 
 
 Leigh ton and H. 3.. 1 
 
 /illman, 1950, J. C. Frye 
 
 and n. B. Willman, 1960) 
 
 Staqe 
 
 SufastaQe 
 
 Nature of Deoosits 
 
 Special features 
 
 Recent 
 
 
 s 000 vrs - - 
 
 Soil, youthful profile 
 of weathering, lake and 
 river deposits, dunes, 
 peat 
 
 
 
 Valderan 
 ] 1 000 vt'i 
 
 Outwash 
 
 Glaciation in northern 
 Illinois 
 
 
 Twocreekan 
 12.500 vrs-. 
 
 Peat, alluvium 
 
 Ice withdrawal, erosion 
 
 c 
 c 
 
 •ri 
 
 to 
 
 c 
 o 
 
 Woodfordian 
 22,000 yrs. 
 
 Drift, loess, dunes 
 lake deposits 
 
 Glaciation, building of 
 many moraines as far 
 south as Shelbyville, ex- 
 tensive valley trains, 
 outwash plains, and lakes 
 
 o 
 
 (0 
 
 •H 
 
 3: 
 
 Farmdalian 
 
 28.000 vrs - 
 
 Soil, silt and 
 peat 
 
 Ice withdrawal, weather- 
 ing, and erosion 
 
 
 Altonian 
 50,000 to 
 
 Drift, loesb 
 
 Glaciation in northern 
 Illinois, valley trains 
 along major rivers, 
 Winnebago drift 
 
 Sengamonian 
 
 (3rd interglacial) 
 
 fvJ,uvju yrs.~ ' 
 
 Soil, mature- profile 
 of weathering, al- 
 luvium, peat 
 
 
 illinoian 
 (3rd Glacial) 
 
 Buff alohartan 
 
 Jecksonviliian 
 
 Paysonian 
 (terminal) 
 
 Lovelandian 
 (Pro-Illincian) 
 
 Drift 
 Drift 
 Drift 
 
 Loess (in advance of 
 glaciation) 
 
 
 Yarmouthian 
 (2nd interglac 
 
 ial) 
 
 
 Soil, mature profile 
 of weathering, al- 
 luvium, peat 
 
 
 Kansan 
 
 (2nd glacial) 
 
 
 Drift 
 Loess 
 
 
 Aftonian 
 
 (1st interglacial] 
 
 
 Soil , mature profile 
 of weathering, al- 
 luvium, peat 
 
 
 Nebraskan 
 
 (1st glacial) 
 
 
 Dri ft 
 
 
^^e^ T ^"T N . S °'^^^T^^' ; ' NEBA ?"' d ' ""T^p^NEf^MCyTENW - " 5fw 
 
 GEOLOGIC MAP OF ILLINOIS 
 
 showing 
 
 BEDROCK BELOW 
 
 THE GLACIAL DRIFT 
 
 1961 
 
 - W&L ■ 
 
 ■ ' \v::; "> DEKALB ",( KANE 
 
 ^V^r'OSDM 
 
 W^H^ 
 
 \£/d'up'aGE I \ 
 
 Tertiary 
 (Pliocene omitted) 
 
 Pennsylvanian 
 (Above No. 6 Coal) 
 
 Pennsylvanian 
 (Below No. 6 Coal) 
 
 Mississippian 
 (Middle and Lower) 
 
 Silurian and Devonian 
 
 ILLINOIS STATE GEOLOGICAL SURVEY. URBAHA 
 
 (47669-15M-11-61) *f 
 
TILL PLAINS SECTION, 
 
 GREAT LAKE 
 
 CENTRAL 
 
 LOWLAND 
 
 PROVINCE 
 
 ff- 
 
 * J \ 
 
 < / if 
 
 CENTRAL 
 
 LOWLAND 
 
 PROVINCE 
 
 INTERIOR 
 LOW 
 
 PLATEAUS 
 PROVINCE 
 
 ILLINOIS STATE GEOLOGICAL SU*VEY 
 
 COASTAL PLAIN 
 PROVINCE 
 
 PHYSIOGRAPHIC DIVISIONS OF ILLINOIS 
 
 (Reprinted from Illinois State Geological Survey Report of 
 Investigations 129, "Physiographic Divisions of Illinois, " 
 by M. M. Leighton, George E. Ekblaw, and Leland Horberg) 
 
 (47669-15M-11-61) «a^^>» 
 
GLACIAL MAP OF NORTHEASTERN ILLINOIS 
 
 (47669- 15M-11-61) 
 
 GEORGE E. EKBLAW 
 Revised 1960 
 
Plate I 
 
 Common Types of Illinois fossils 
 
 Cup coral 
 
 GRAPTOLITE 
 
 
 Lithostrotion 
 
 CORALS 
 
 Honeycomb coral 
 
 Archimedes 
 
 Fenestella 
 
 Branching 
 
 BRYOZOA 
 
 CRINOID 
 
 PENTREMITE 
 
 Lingula Orbiculoidea 
 
 Spiriferoid 
 
 Productoid 
 
 Pentameroid 
 
 BRACHIOPODS 
 
 (55757-25M-5-62) ■*>% 
 
Plate 2 
 
 COMMON TYPES of ILLINOIS FOSSILS 
 
 "Clam" "Scallop" 
 
 PELECYPODS 
 
 Curved cone 
 
 ?2 
 
 Coiled cone 
 (Nautilus) 
 
 Straight cone 
 
 CEPHALOPODS 
 
 Low - spired 
 
 High- spired 
 
 Flat - spired 
 GASTROPODS 
 
 Bumastus 
 
 Calymene 
 (coiled ) 
 
 OSTRACODS 
 (greatly enlarged) 
 
 Calymene 
 (flat) 
 
 TRILOBITES 
 
 (55757-25M-5-62)