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-The Project Gutenberg eBook of Guide to the Geologic Map of Illinois, by
-anonymous anonymous
-
-This eBook is for the use of anyone anywhere in the United States and
-most other parts of the world at no cost and with almost no restrictions
-whatsoever. You may copy it, give it away or re-use it under the terms
-of the Project Gutenberg License included with this eBook or online at
-www.gutenberg.org. If you are not located in the United States, you
-will have to check the laws of the country where you are located before
-using this eBook.
-
-Title: Guide to the Geologic Map of Illinois
-       Educational Series 7
-
-Author: anonymous anonymous
-
-Release Date: June 26, 2021 [eBook #65704]
-
-Language: English
-
-Character set encoding: UTF-8
-
-Produced by: Stephen Hutcheson and the Online Distributed Proofreading
-             Team at https://www.pgdp.net
-
-*** START OF THE PROJECT GUTENBERG EBOOK GUIDE TO THE GEOLOGIC MAP OF
-ILLINOIS ***
-
-
-
-
-                             _Guide to the_
-                        GEOLOGIC MAP OF ILLINOIS
-
-
-                   _Illinois State Geological Survey
-                         Educational Series 7_
-
-                           STATE of ILLINOIS
-                         Otto Kerner, Governor
-
-    [Illustration: SEAL OF THE STATE OF ILLINOIS]
-
-                DEPARTMENT of REGISTRATION and EDUCATION
-                   William Sylvester White, Director
-
-
-                                  1961
-
-
-                    ILLINOIS STATE GEOLOGICAL SURVEY
-                          John C. Frye, Chief
-                            URBANA, ILLINOIS
-
-             PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS
-                          42517-20M 2 (78783)
-
-
-
-
-                             _Guide to the_
-                        GEOLOGIC MAP OF ILLINOIS
-
-
-
-
-                            GLACIAL GEOLOGY
-
-
-    [Illustration: Decorative capital]
-
-Although the age of the Earth is measured in billions of years, the face
-of Illinois is young—a mere 15,000 years old.
-
-During the Ice Age, most of Illinois was repeatedly invaded by huge
-glaciers, sometimes towering a mile or more high, that carried embedded
-in them ground up rock materials they had gouged out of the bedrock to
-the north as they ponderously pushed south.
-
-When the last of the glaciers melted from Illinois, about 15,000 years
-ago, the country that emerged looked far different from the preglacial
-land. Old hills and valleys had vanished, new ones had formed, and a
-mantle of unconsolidated rock material, the burden carried by the ice
-and dropped as the ice melted, lay over most of the region.
-
-Most of this material, called glacial drift, was brought in by the ice
-during the last two of the four major periods of glaciation—the
-Illinoian period 100,000 to 150,000 years ago and the Wisconsinan 5,000
-to 50,000 years ago. The older drift introduced during the Kansan and
-Nebraskan glacial periods is almost entirely buried beneath the later
-drifts.
-
-The glaciers covered all of Illinois except the northwestern corner, the
-southwestern edge along the Mississippi River, and extreme southern
-Illinois, as shown in figure 1. In those areas the land is much as it
-was before the glaciers came. In the glaciated portion of the state,
-however, the bedrock generally is covered by the rock debris the ice
-carried from as far away as Canada. As the fringes of the ice melted,
-these loads of rock material were, in some places, dumped as ridges
-(moraines) which are the hills and mounds on the flat prairies of the
-present landscape. Such material also filled ancient river valleys, but
-new valleys were cut by torrents of water released by the melting ice.
-
-    [Illustration: Figure 1—A mantle of glacial drift covers the bedrock
-    in much of Illinois.]
-
-  WISCONSINAN GLACIAL DRIFT
-  KANSAN GLACIAL DRIFT
-  ILLINOIAN GLACIAL DRIFT
-
-The glacial drift belongs to the youngest (topmost layer) of the major
-divisions of our rocks, which geologists have named the Pleistocene
-(scientific name for Ice Age deposits).
-
-Most of the drift is an unsorted mixture of clay, pebbles, and boulders
-called “till,” but some glacial deposits consist of water-sorted sand
-and gravel carried and deposited by meltwater from the glaciers. Other
-materials were deposited by the wind—sand was piled into shifting dunes
-and fine silts were spread like a blanket over the land. This mantle of
-silt is called loess.
-
-The glacial deposits contain a wide variety of rocks, some brought from
-regions to the north, others scoured from the layers of native rock in
-Illinois.
-
-The limits of the Illinoian, the Wisconsinan, and the Kansan glaciations
-are shown in figure 1. Some of the more prominent moraines are sketched
-with dark gray lines on plate 1. Within this area, glacial drift covers
-the bedrock except along valleys where streams have cut through and
-removed it.
-
-
-                            BEDROCK GEOLOGY
-
-Beneath the glacial drift of Illinois many layers of rocks overlie a
-base of ancient crystalline rocks that in Illinois occur at depths of
-2,000 to as much as 15,000 feet. The geologic map (plate 1, in pocket)
-is drawn as if the mantle of glacial drift had been removed to expose
-the layers of bedrock, which are largely limestone, shale, and
-sandstone.
-
-The key on the map shows the age sequence of the rocks, arranged with
-the youngest at the top, and gives the names that geologists have
-assigned to the various systems of rocks. Each system consists of rocks
-that were deposited during a long period of time. The complete sequence
-of rocks might be likened to a book of earth history, and each system
-likened to a chapter. Systems are divided into formations, which might
-be regarded as pages in the book.
-
-As shown on the generalized rock column in figure 2, the rocks next
-older than the glacial drift (Pleistocene) are the Tertiary and
-Cretaceous sands, gravels, and clays, mostly unconsolidated. They occur
-only at the extreme southern tip of Illinois and were deposited when
-that area was covered by a northward extension of the Gulf of Mexico.
-The Tertiary rocks are shown on the map in grayed pink (T) and the
-Cretaceous in red-violet (K).
-
-Next older than the Cretaceous are the Pennsylvanian rocks, named for
-the state of Pennsylvania where they are well exposed and were first
-studied.
-
-The Pennsylvanian System is divided into two areas on the map (P¹ and
-P²). The rocks shown in lightest gray (P²) lie above the No. 6 Coal in
-the sequence and those in medium gray (P¹) lie below it. The No. 6 Coal
-is one of the thickest, most valuable coals in the state. Pennsylvanian
-rocks occur under the glacial drift, and their thickness ranges from a
-few feet to as much as 3,000 feet.
-
-    [Illustration: Figure 2—Diagram of layers of rocks in Illinois. The
-    oldest rocks are at the bottom, the youngest at the top. Names are
-    the standard ones applied by geologists to the subdivisions of the
-    geologic eras.]
-
- Era                                 General Types of Rocks
-    Period or System and Thickness
-       Epoch
-
- CENOZOIC “Recent Life”
- Age of Mammals
-    Quaternary
-    0-500′
-       Pleistocene or Glacial Age
-                        Recent—alluvium in river valleys
-                        Glacial till, glacial outwash, gravel, sand,
-                        silt lake deposits of clay and silt, loess and
-                        sand dunes; covers nearly all of state except
-                        northwest corner and southern tip
-    Tertiary
-    0-500′
-       Pliocene         Chert gravel; present in northern, southern, and
-                        western Illinois
-       Eocene           Mostly micaceous sand with some silt and clay;
-                        present only in southern Illinois
-       Paleocene        Mostly clay, little sand; present only in
-                        southern Illinois
- MESOZOIC “Middle Life”
- Age of Reptiles
-    Cretaceous          Mostly sand, some thin beds of clay and,
-    0-300’              locally, gravel; present only in southern
-                        Illinois
- PALEOZOIC “Ancient Life”
-    Age of Amphibians and Early Plants
-    Pennsylvanian       Largely shale and sandstone with beds of coal,
-    0-3,000′            limestone, and clay
-    (“Coal Measures”)
-    Mississippian       Black and gray shale at base; middle zone of
-    0-3,500’            thick limestone that grades to siltstone, chert,
-                        and shale; upper zone of interbedded sandstone,
-                        shale and limestone
-    Age of Fishes
-    Devonian            Thick limestone, minor sandstones and shales;
-    0-1,500’            largely chert and cherty limestone in southern
-                        Illinois
-    Age of Invertebrates
-    Silurian            Principally dolomite and limestone
-    0-1,000’
-    Ordovician          Largely dolomite and limestone but contains
-    500-2,000’          sandstone, shale, and siltstone formations
-    Cambrian            Chiefly sandstones with some dolomite and shale;
-    1,500-3,000’        exposed only in small areas in north-central
-                        Illinois
- ARCHEOZOIC and PROTEROZOIC
-                        Igneous and metamorphic rocks; known in Illinois
-                        only from deep wells
-
-The Pennsylvanian System contains many different kinds of rocks,
-including all of our minable coals. It also contains important deposits
-of limestone, shale, and clay, and at places oil and gas.
-
-Next below the Pennsylvanian are the rocks of the Mississippian System,
-shown in blue on the map (M¹ and M²). The lower and middle Mississippian
-rocks (M¹) are largely limestone in and near the areas mapped, but in
-the central and eastern part of the state where they are buried under
-Pennsylvanian rocks they contain much siltstone and cherty limestone.
-The upper Mississippian rocks (M²) consist of a succession of sandstone,
-shale, and limestone formations.
-
-This system of rocks takes its name from the Mississippi River because
-there are excellent exposures of these strata along the Mississippi
-Valley in western Illinois, southeastern Iowa, and eastern Missouri.
-
-The Mississippian rocks are a source of limestone, fluorspar, zinc, and
-ganister, and are of greatest economic significance in southeastern
-Illinois where they are the most important of our oil-producing rocks.
-
-The Devonian (D, dark gray on the map), Silurian, (S, violet),
-Ordovician (O, light pink), and Cambrian (C, deep pink) rocks, in the
-order named, are older than the Mississippian strata. In general, they
-include dolomite, limestone, shale, and sandstone. Except for small
-areas along the Mississippi and Illinois River Valleys, these older
-rocks are found at the surface only in the northern quarter of the state
-and locally in Alexander, Hardin, Jackson, Monroe, Pike, and Union
-Counties. They are nevertheless economically important because they
-yield limestone, dolomite, silica sand, oil, zinc and lead, tripoli,
-novaculite, and novaculite gravel.
-
-The rocks of the Cambrian through Pennsylvanian Systems belong to the
-Paleozoic Era. The Paleozoic rocks overlie crystalline rocks, such as
-granites, that extend to unknown depths in the crust of the earth. The
-crystalline rocks are not exposed in Illinois but are encountered in the
-drilling of some deep wells and may be seen in the nearby Missouri
-Ozarks and in central Wisconsin.
-
-
-                           STRUCTURAL GEOLOGY
-
-The rock formations appear to lie flat in most of Illinois, but they are
-slightly inclined in most places. In some areas they are down-warped
-into basins and troughs (synclines), upfolded into domes and arches
-(anticlines), or broken by faults.
-
-The largest structural feature in Illinois is a great spoon-shaped
-basin—the Illinois Basin—that extends southeastward into Indiana and
-Kentucky. The deepest part of the basin is in southeastern Illinois.
-
-    [Illustration: Figure 3—When rocks are down-warped and the surface
-    is leveled by erosion, the youngest rocks are preserved in the
-    center and the older rocks are exposed at the margins.]
-
-Because the entire region, including the basin, has been eroded by rain,
-ice, wind, and many rivers and streams, the youngest Paleozoic rocks
-(top-most layers) are preserved only in the middle of the basin, as
-shown in figures 3, 6, and 7. This is why the map shows the coal-bearing
-rocks of Pennsylvanian age in the center of the state and the older
-rocks cropping out in successive bands around the margins of the basin
-in southern, western, and northern Illinois.
-
-Distribution of bedrock in northern Illinois is influenced by a broad
-upfold or arch (see figures 4, 6, and 7). The map (plate 1) shows the
-older rocks (Cambrian and Ordovician) exposed at the center of the arch
-and surrounded by younger Silurian and Devonian rocks. Another elongated
-upfold (anticlinal belt) extends from the vicinity of Dixon
-southeastward into Indiana. The crest of the upfold is indicated on the
-map by patches of Silurian and Devonian rocks in Champaign and Douglas
-Counties.
-
-    [Illustration: Figure 4—When rocks are upfolded and the surface is
-    eroded, the older rocks are exposed at the crest of the dome or
-    anticline.]
-
-In extreme southern Illinois and in north-central Illinois, the rock
-layers are broken by great faults (see figures 5 and 6) which displace
-the layers of rocks by as little as a few inches to as much as 3,000
-feet.
-
-The structural map of Illinois (figure 6) shows the position of the
-major geologic structures. The big basin is indicated by shading, with
-the darkest pattern showing where the basin is deepest. The same strata
-that lie at sea level at the basin’s outer edge are downwarped to 6,000
-feet below sea level in its deepest part. Axes of some small anticlines
-and locations of major fault zones also are shown.
-
-    [Illustration: Figure 5—When rocks are faulted by earth stresses,
-    the layers of rock are displaced or offset.]
-
-    [Illustration: Figure 6—Major structural features of Illinois—the
-    Illinois Basin, anticlines, and faults. The increasing depth of the
-    basin is shown by progressively darker patterns.]
-
-  KANKAKEE ARCH
-  MISSISSIPPI R. ARCH
-  LA SALLE ANTICLINAL BELT
-  OZARK UPLIFT
-  KEY
-    Position of major anticline
-    Major faults
-
-    [Illustration: Figure 7—The cross section from north to south
-    through Illinois shows the strata down-warped into the basin.]
-
-
-                           HISTORICAL GEOLOGY
-
-Reading the history of the earth’s crust is like reading a mystery
-story. The geologist must examine, or read, each rock layer, from the
-youngest at the top to the oldest at the bottom, searching for clues to
-its origin, age, and development from which he can reconstruct the past.
-
-One of the clues to the past is the fossil remains of plants and animals
-found in the rocks. For instance, if a certain coral is known to have
-lived only during one span of time, all rocks containing that coral
-fossil must have been formed within that span.
-
-Records of wells (well logs) and rock cores or samples collected when
-test holes are drilled into the bedrock also reveal much about the
-sequence of rock strata beneath the surface. The kinds of rocks
-encountered tell, in addition, something about ancient geography, for
-some were formed on land and others were deposited in long-departed
-seas.
-
-Such knowledge is extremely important in finding and developing mineral
-resources such as coal and oil.
-
-
-                            ECONOMIC GEOLOGY
-
-Minerals produced commercially in Illinois include crude oil, coal,
-limestone, dolomite, clay, sand, gravel, fluorspar, tripoli, ganister,
-novaculite gravel, silica sand, and the metals zinc and lead. The
-distribution of mineral industries, shown in the several maps of figures
-8 through 12, is, of course, related to the distribution of the rocks
-(plate 1). For example, the coal mines are scattered along the margin of
-the area of Pennsylvanian rocks where the coals are at relatively
-shallow depths.
-
-The mineral fuels, coal and petroleum, are the leading mineral products
-of Illinois, making up about 70 percent of the annual value of all
-minerals produced in the state. For many years coal was at the top of
-the list, but petroleum now holds first place.
-
-
-                               Petroleum
-
-In recent years production of petroleum has averaged about 78 million
-barrels each year, making Illinois the eighth largest petroleum
-producing state. The major oil area is the deep part of the Illinois
-Basin in the southcentral and southeastern parts of the state, but
-significant discoveries have been made recently in central and western
-Illinois. There are about 490 oil fields in Illinois, ranging from a few
-to several thousand acres in size.
-
-Oil has been discovered in rocks of the Pennsylvanian, Mississippian,
-Devonian, Silurian, and Ordovician Systems, but the Mississippian are
-the most productive and account for about 76 percent of our total oil
-production.
-
-    [Illustration: Figure 8—Oil pools in Illinois as of January 1, 1961.
-    The pools are concentrated mainly in the Illinois Basin and along
-    the LaSalle Anticlinal Belt.]
-
-    [Illustration: Figure 9—Active coal mines are scattered around the
-    margin of the basin where the coals are at relatively shallow
-    depths.]
-
-  KEY
-    SHIPPING MINES
-      Underground
-      Strip
-      Slope
-    LOCAL MINES OVER 25,000 TONS
-      Underground
-      Strip
-
-
-                                  Coal
-
-Illinois ranks fourth in the nation among states that produce bituminous
-coal, the type of coal most widely mined in the United States. Coal is
-used by many manufacturing industries, by public utilities companies
-that burn coal to generate electricity, and by individuals for heating
-homes.
-
-All Illinois coal deposits are found in the Pennsylvanian System. Of the
-many coals, only a few are thick enough to be mined profitably. The coal
-is of bituminous rank, but it varies in quality. Illinois coal reserves
-in strata more than 28 inches thick are estimated at 137 billion tons
-and are larger than those of any other state.
-
-Around the edge of the coal basin where the coal lies at shallow depths,
-it is commonly mined in open pits (strip mines). However, in the past,
-most coal has been mined underground, and more than half of Illinois
-coal is still produced from such mines.
-
-
-                         Limestone and Dolomite
-
-There are two types of carbonate rocks in Illinois, limestone and
-dolomite. In appearance they are almost indistinguishable, although they
-are different chemically. Limestone is composed mainly of calcium
-carbonate (the mineral calcite), whereas dolomite is calcium magnesium
-carbonate (the mineral dolomite).
-
-Limestone deposits are found at many places in the western,
-southwestern, and southern marginal portions of the state. They are
-largely of Mississippian and Ordovician age. Lesser deposits of
-Pennsylvanian limestone are found in the central portion of the state.
-In the northern fifth of the state, dolomites of Silurian and Ordovician
-age are exposed at many places.
-
-Limestone and dolomite are quarried for a variety of uses, including
-aggregate for concrete, agricultural limestone, railroad ballast, chips
-for bituminous roads, and for use in metallurgical and chemical
-processes. They also are quarried for building stone at some places, and
-marble is produced in southern Illinois.
-
-    [Illustration: Figure 10—Limestone and dolomite are quarried at many
-    places, but fluorspar, zinc, and lead are produced in restricted
-    mineralized areas.]
-
-  KEY
-    Quarry, Limestone or Dolomite
-    Cement or Lime
-    Fluorspar
-    Zinc and Lead
-
-Limestone and shale or clay are burned together in kilns to produce
-portland cement. Portland cement is manufactured from a Pennsylvanian
-limestone in LaSalle County and from an Ordovician limestone in Lee
-County.
-
-Limestone or dolomite also is burned in kilns to make lime.
-Mississippian limestone is used in Adams County and Silurian dolomite is
-used in Cook County for lime making.
-
-
-                         Clay and Clay Products
-
-Illinois commercial clays are found in glacial, Cretaceous, Tertiary,
-and Pennsylvanian deposits. Pennsylvanian shales also are sources of
-clays. Glacial clays, which occur as loess (wind-blown materials),
-alluvial (water-deposited) sediments, and glacial till, are widespread
-in the state. Cretaceous and Tertiary clays, at the extreme southern tip
-of the state, are valuable for the manufacture of heat-resistant bricks
-and coatings and for floor-sweeping compounds.
-
-Pennsylvanian clays and shales are the most important source of clay for
-manufacturing such products as pottery, stoneware, drain tile, sewer
-pipe, flue tile, building tile, brick, and special heat-resistant
-fire-brick.
-
-
-                            Sand and Gravel
-
-Deposits of sand and gravel, found in many parts of Illinois, provide
-large quantities of material for concrete, railroad ballast, road
-gravel, building sand, molding sand, and other uses. Glacial deposits
-are the principal sources of sand and gravel, but in extreme southern
-Illinois where there is no glacial drift the main source of supply is
-Tertiary gravel and Devonian chert gravel.
-
-    [Illustration: Figure 11—The clay industry is scattered widely in
-    Illinois. Many manufacturing plants are located at the clay pits.]
-
-  KEY
-    Pit or Plant
-
-Almost every county has some sand and gravel, but the major areas of
-production are northeastern Illinois and some of the major rivers.
-Considerable tonnages of sand and gravel are dredged from bars in the
-channels of the Mississippi, Ohio, and Wabash Rivers.
-
-
-                              Silica Sand
-
-Silica sand is used in making glass, for sand blasting, as grinding
-sand, as molding sand for casting steel, and in the fracture treatment
-of oil wells to increase oil production. Some of the sand is finely
-pulverized into a powder that is used as a filler, a fine abrasive, as a
-ceramic material, and for many other purposes.
-
-This special sand, composed of grains of the mineral quartz (silica),
-comes from a sandstone of Ordovician age that is mined in LaSalle and
-Ogle Counties.
-
-
-                          Tripoli and Ganister
-
-Tripoli, or “amorphous” silica, is mined from Devonian rocks in
-Alexander County. The silica is finely ground for use as a polishing
-agent, as a filler, in buffing compounds, and for other purposes.
-
-Ganister, a granular material with a high silica content, also is mined
-in extreme southern Illinois. It is used in making products that can
-withstand high temperatures.
-
-
-                               Fluorspar
-
-For many years Illinois has led the nation in the production of
-fluorspar, accounting annually for about half the total United States
-output. The industry is centered in Hardin and Pope Counties where the
-deposits occur in veins and beds in rocks of the Mississippian System.
-Reserves of fluorspar are adequate to supply the industry for many
-years.
-
-    [Illustration: Figure 12—Sand and gravel is produced at many places
-    in the state. Silica sand is produced only from a sandstone in
-    northern Illinois. Tripoli is found only in southern Illinois.]
-
-  KEY
-    Sand and Gravel
-    Silica Sand
-    Molding Sand
-    Tripoli
-
-Fluorspar is used in the manufacture of hydrofluoric acid, as a flux in
-the manufacture of steel, in the refining of aluminum, for the
-manufacture of fluorine compounds used in a variety of products, in
-ceramic glazes, and for other special purposes.
-
-
-                             Lead and Zinc
-
-Lead and zinc are the only metallic minerals mined in Illinois. Deposits
-are found in Jo Daviess County in northwestern Illinois and in the
-fluorspar area of Hardin and Pope Counties in extreme southern Illinois.
-In northwestern Illinois the ore occurs in rocks of Ordovician age, but
-in southeastern Illinois it is associated with fluorspar in rocks of
-Mississippian age.
-
-Between 1820 and 1865, the mining area of which northwestern Illinois is
-a part was the nation’s principal producer of lead ore. In recent years
-production of zinc has increased and that of lead has decreased.
-
-
-                             Water Supplies
-
-Water, too, is a mineral resource, and our most necessary one. The
-source of nearly all water is rain and snow, which collect in lakes and
-streams or seep into the ground to form our two types of water
-supplies—surface water and ground water.
-
-Ground water in Illinois collects underground in deposits of sand and
-gravel or in the porous sandstone or limestone layers of bedrock. These
-rock materials are called “aquifers” because of their ability to hold
-water and to allow it to flow into wells that are drilled into them.
-
-The aquifers are not equally distributed throughout Illinois, so
-ground-water supplies are abundant in some parts of the state but are
-scarce in others. Some Illinois cities depend wholly or partly on
-surface supplies from lakes and rivers.
-
-The sand and gravel aquifers yield more ground water than any others in
-Illinois. The major sand and gravel aquifers were deposited by streams
-and lie along river valleys. Some of these river valleys are no longer
-visible to us because they were buried by glacial drift. They are
-recognized, however, from well records or drilling records.
-
-The northern third of Illinois has the most abundant supplies of ground
-water. Bedrock formations of Devonian through Cambrian age are favorable
-aquifers and supply drinkable (potable) water at depths of from 200 to
-2,000 feet. These formations, however, lie much deeper in the Illinois
-Basin, where the water they furnish is too salty for most uses.
-
-West of the Illinois River and at the southern tip of the state, the
-Mississippian, Devonian, and Silurian limestones are the chief aquifers.
-Their yield, however, is small.
-
-In the Illinois Basin all these formations are overlain by Pennsylvanian
-rocks which offer only small, scattered supplies of ground water.
-
-
-
-
-                    ILLINOIS STATE GEOLOGICAL SURVEY
-
-
-A city or farmer needs a new water supply. Where can suitable
-water-bearing formations be found? A new limestone quarry is considered.
-Where are the most suitable limestone deposits? A coal mine is being
-planned. How deep must a shaft be sunk to reach the nearest minable coal
-and what will the mining conditions be? A land owner has a clay deposit
-on his land. What uses can be made of it? A road is to be constructed.
-Are sand and gravel or limestone deposits available nearby for
-construction materials? A farmer wants to know whether there might be
-oil on his property. Are oil-bearing structures present and, if so, at
-what depth?
-
-These are typical questions brought to the Illinois State Geological
-Survey by the industries and people of Illinois. From its accumulated
-store of information and experience, the Survey provides answers. This
-storehouse of knowledge is the result of the Survey’s continuous program
-of geologic exploration, mapping, research, and organization and
-interpretation of data.
-
-The Survey explores and maps the geology and mineral resources of the
-state, does research to find new and improved uses for our mineral
-resources, and organizes and interprets basic geologic information
-gathered from well logs, rock samples, and field studies, putting them
-all into usable form.
-
-Such knowledge is shared with the public through publications, maps,
-lectures, and personal consultations with industries, drillers,
-engineers, land owners, teachers, and others in need of geologic
-information.
-
-The discovery of facts about the rich mineral resources of Illinois has,
-in effect, only begun, and it is the task of the Geological Survey to
-continue to collect and apply new information so that our resources can
-be used to the best advantage.
-
-
-
-
-                     EDUCATIONAL EXTENSION PROGRAM
-
-
-The Educational Extension Section of the Geological Survey conducts six
-field trips each year, in various parts of the state, for teachers,
-students, and laymen. It also assembles and distributes rock and mineral
-collections for Illinois educational groups, gives lectures, prepares
-exhibits, and identifies rocks and minerals for the public.
-
-
-Educational Extension publications, such as this book, are simplified
-discussions of geological subjects. Available for 25 cents each, these
-include:
-
-    Educational Series 4: Guide for Beginning Fossil Hunters, by Charles
-          W. Collinson.
-    Educational Series 5: Guide to Rocks and Minerals of Illinois.
-    Educational Series 6: Field Book of Pennsylvanian Plant Fossils of
-          Illinois, by Charles Collinson and Romayne Skartvedt.
-
-Many technical discussions of the various phases of Illinois geology
-also are published by the Geological Survey. Regional reports on the
-geology and mineral resources of some areas are available in many school
-and public libraries or they may be purchased from the Survey. Some of
-the regional reports include:
-
-    Beardstown, Glasford, Havana, and Vermont Quadrangles, Bulletin 82,
-          $1.00.
-    Buda Quadrangle, Circular 275, no charge.
-    Carlinville Quadrangle, Bulletin 77, $1.00
-    Chicago Region, Bulletin 65, Part 1, 50 cents.
-    Marseilles, Ottawa, and Streator Quadrangles, Bulletin 66, $1.00.
-
-“Mineral Production in Illinois in 1959,” Circular 300 (no charge), is
-one of a series of annual economic summaries. “Caves of Illinois,”
-Report of Investigations 215, price 50 cents, will be available by
-September 1961.
-
-
-         Illinois State Geological Survey Educational Series 7
-                  24 pages, 1 plate, 12 figures, 1961
-
-    [Illustration: Illinois State Geological Survey, Urbana Educational
-    Series 7—Plate 1—North]
-
-    [Illustration: Illinois State Geological Survey, Urbana Educational
-    Series 7—Plate 1—Central]
-
-    [Illustration: Illinois State Geological Survey, Urbana Educational
-    Series 7—Plate 1—South]
-
-  GEOLOGIC MAP OF ILLINOIS
-  showing
-  BEDROCK BELOW
-  THE GLACIAL DRIFT
-  1961
-  KEY
-    T  Tertiary (Pliocene omitted)
-    K  Cretaceous
-    P²  Pennsylvanian (Above No. 6 Coal)
-    P¹  Pennsylvanian (Below No. 6 Coal)
-    P³  Pennsylvanian (Above No. 6 Coal)
-    M²  Mississippian (Upper)
-    M¹  Mississippian (Middle and Lower)
-    D   Devonian
-    SD   Silurian and Devonian
-    S   Silurian
-    O   Ordovician
-    C   Cambrian
-    F  Fault
-    OSDM   Complex faulted area
-  Physiographic base map by James A. Bier
-  Price, 25 cents
-
-    [Illustration: PENNSYLVANIAN COAL-BEARING ROCKS]
-
-
-
-
-                          Transcriber’s Notes
-
-
-—Silently corrected a few typos.
-
-—Retained publication information from the printed edition: this eBook
-  is public-domain in the country of publication.
-
-—In the text versions only, text in italics is delimited by
-  _underscores_.
-
-
-
-*** END OF THE PROJECT GUTENBERG EBOOK GUIDE TO THE GEOLOGIC MAP OF
-ILLINOIS ***
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