1557.73 Gr-5 c. 3 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION A. M. SHELTON. Direc or DIVISION OF THE STATE GEOLOGICAL SURVEY M. M. LEIGHTON. Chief REPORT OF INVESTIGATIONS-NO. 5 STRUCTURE OF HERRIN (NO. 6) COAL SEAM NEAR DUQUOIN BY D. J. FISHER ILLII^DIS DOCUMENT JAN 1 3 1968 ILLl ms STATE LIBRAR PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA. ILLINOIS 1925 £ 3 - STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION A. M. SHELTON, Dirac or DIVISION OF THE STATE GEOLOGICAL SURVEY M. M. LEIGHTON. Chiaf REPORT OF INVESTIGATIONS-NO. 5 STRUCTURE OF HERRIN (NO. 6) COAL SEAM NEAR DUQUOIN BY D. J. FISHER PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS 1925 ILLINOIS STATE LIBRARY STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE STATE Gl^OLOGlCAJ. SUR\ EY M. M. LEIGHTON, Chief Goniniittee of the Board f)f Natural Besoure(*s and Gonsei'valion A. M. Sheltox. Chairman Director of Registration and Education Kexdhtc C. Babcock Representing the President of the Uni versity of Illinois Edsox S. Bastix Geologist ^ TRAPES tegcorNaL» SCHNEPP & Barnes, Printers Springfield, III. 1925 32712—1500 7 - 7 ? / ‘ STRLCTUKK OF HI^.RRIX (NO. (>) COAL SEAM NEAR J)UQL()IN By D. J. Fisher OUTLINE PAGi': Introduction . 7 Location . 7 Object of report. 7 Methods of study. 7 Acknowledgments . 7 Previous work and bibliography. 8 Stratigraphy. 8 General statement . 8 Origin of strata. 8 Formation of shale and limestone. 9 Formation of coal. 9 Description of the rocks. 9 General statement . 9 Herrin (No. 6) coal. 10 Strata below Herrin coal. 11 Beds between Herrin and Harrisburg coals. 11 Harrisburg (No. 5) coal. 12 Strata above Herrin coal. 15 The “cap-rock” limestone. 15 Strata between the “cap-rock” limestone and the Herrin coal 15 Limits of the area underlain by the Herrin coal. 17 Accuracy of the boundary line. 17 Absence of coal in region. 18 Area of possible non-deposition. 18 Areas of subsequent erosion. 18 Structure . 18 Structural features developed before or during consolidation. 18 Splits. 18 General statement . 18 The mapping of split areas. 19 Detailed descriptions of areas underlain by split coal. 19 Majestic mine . 19 Mulkeytown area . 21 Hallidayboro-Bush area . 21 Origin . 21 Structural features developed after consolidation. 22 General considerations . 22 Structure contours . 23 Accuracy of the structure contours. 24 Warping . 24 Duquoin monoclinal flexure. 24 Faulting. 25 General character of the faults. 25 Systems of faulting. 25 O O OUTLINE—Concluded Description of the faults. Faults near Weaver. Faults near Royalton. Faults near Hallidayboro. Faults near Dowell. Faults east of Duquoin. Practical economic aspects. Value of the structure contour map, Plate I. . . . Effects of faulting on mining methods at Dowell Importance of drilling.’.. PAGE , 26 26 , 27 28 , 29 31 , 32 32 33 . 33 ILLUSTRATIONS PLATE PAGE I. Map of the Duquoin area showing structure of the Herrin coal seam .Pocket II. Structure map of the Kathleen mine at Dowell.Pocket FIGURE 1. Division of the State into districts, and area covered in this report 6 2. The Herrin coal in its unusual thickness of about 13 feet near Christopher. 19 3. Photograph of the “blue-band” in the Herrin coal. 11 4. Generalized columnar section showing strata above and below the Herrin coal . 12 5. Map of the Duquoin area showing drill holes which reach the level of the Harrisburg (No. 5) coal seam. 14 6. Convergence map showing interval between the “cap-rock” lime¬ stone and the Herrin coal at Dowell. 16 7. Diagrammatic cross-section of split in the Majestic mine. 19 8. Detail of north side of split. ^lajestic mine. 20 9. Surface of the Herrin coal as it would appear if all the overlying material were removed. 23 10. Cross-section of main fault in No. 2 Inline at Bush. 27 11. Cross-section of fault in the main west entry of the mine at Hallidayboro . 28 12. Cross-section of fault in the back east entry of the mine at Hallidayboro . 29 13. Profile of faulted area in the Kathleen mine. 39 14. Detailed sketch of a fault in the Kathleen mine. 31 15. Cross-section of a fault in the Kathleen mine. 32 TABLES 1. Summarized data regarding the thickness of several limestones and the intervals between them and the Herrin coal. 15 Digitized by the Internet Archive in 2018 with funding from University of Illinois Urbana-Champaign https://archive.org/details/structureofherriOOfish () STRUCTURE OF IIERRIX COAL NEAR DUQUOIX JO DAVIESS WINNEBAGO LAKE McHENlY CARROLL KANE :E KALB WMJTESlOE KENDALL' 'UTNAV O CC o CO CO z < liJ O -75 -50 Limestone, medium gray, crystalline. Shale, gray. Coal. Shale, gray. (Little coal and "fire clay") Limestone, compact, light gray. Limestone, cap rock, fusulina, medium grained, dark gray. Shale, blaok fissile. Shale, gray, (sandy) Herrin (No. 6) coal. "blue band" "Fire clay" Limestone, compact, light gray Shale, gray, (sandy) Shale, black fissile No. 5 coal. Fig. 4. Generalized columnar section showing the strata above and below the Herrin (No. 6) coal. The thicknesses shown represent the average for the thickly drilled area near Dowell. was made to gather data on this seam. However, because of the in¬ terest shown by certain operators in the Duquoin area, the following statement is included. STRUCTURE OF HERRIN COAL NEAR DUQUOIN 1 -> So far as it is known, only one mine in the area is removing’ any coal from the Harrishurg seam. A small local mine operated hy the Parrish Coal Company of De Soto, and located one mile northwest of De Soto in the SWk N\V. ^ sec. 17, T. 8 S., R. 1 \\ ., is reported to be w^orking this seam. The section shown in the shaft is as follows: d'hickness Feet Clay . 20 Limestone . 2 Shale . 20 Limestone, dark gray. 2-d Shale, black fissile. 0-1^ Coal (No. 5) . d-d The clay at the to]) of this section is ])resumal)ly of glacial origin. Judging from the above stratigraphic section the Harrisburg seam was l)robably about 40 feet below the base of the Herrin coal, before the latter was removed hy erosion. In the mine of the Jackson Coal Company at Hallidayboro, just west of the shaft and east of the main fault, an entry which is now fallen in w^as cut sloping to the northwest. It is reported that the Harrisburg coal was found about 50 feet below the Herrin seam. No data as to the thickness or character of the Harrisburg coal at this locality were available. Faulting or movements in the rocks involving breakage and actual displacement of the strata has in a few cases brought the Harrisburg coal up, so that it is at or near the same level as the Herrin coal. This affords the possibility of mining both beds from the same mine level. It is reported that in the south part of the Kathleen mine at Dowell, the easternmost fault in NE. sec. 8 (PI. H ) with upthrow on the east side has brought the Harrisburg coal up, so that it appears in the face of entries 9-10 E. off the main south entry cut in the Herrin coal. Eigure 5 is a sketch map of the Duquoin area showing the loca¬ tions of the drill holes which reach the level of the Harrisburg coal. The holes in which this scam is absent or not thicker than 2 feet are indicated by a different symbol from those in which it is at least feet thick. In most holes the thickness is 4 to 5 feet. One loef of a hole near St. John shows 0 feet ; one near Waltonville, 7 feet. Data from the logs of about 50 holes in the area show the average thickness of the Harrisburg coal to be 4J4 feet and the average depth below the Herrin seam to be 35feet. crtooH c«'jh j>o-i STRUCTURE OF HERRIN COAL NEAR DUQUOIN 1 } R.2W. R. 1W. R. IE. Fic. 5. Map of the Duquoin area showing the locations of drill holes which reach the level of the Harrisburg (No. 5) coal seam. Scale, 4 miles equal one inch. STRUCTURE OF HERRIN COAL NEAR DUOUOIN 15 STRATA AROVE HERRIN COAL THE “('AP-KOCK” lAMESTONE Aliove the Herrin seam (fig. 4) in the McLeans1)oro formation, the most im])ortant key stratum close to the coal in this area is a fairly persistent thick-bedded limestone locally known as the “cap-rock.” It has a medinm-fine texture, is of a very dark gray color on the fresh surface weathering to a light brown, and contains marine fossils, among which are Girtyina ventricosa as determined in the field by H. E. Culver, a hhisnlina smaller than the forms found in die limestone below the Herrin seam in this region. This “cap-rock” limestone formed in a shallow marine emhayment, having low lying islands, or an irregular shore-line extending into the DiKjnoin area. This is indicated by the somewhat lenticular character of the rock as shown by the logs of drill holes. Other apjiarently lenticular lime¬ stone horizons occur slightly above the “ca])-rock” limestone. It would seem unlikely that the apparent lenticular character of all these limestone horizons would be due to partial erosion of each of them. One of the cores drilled near Dowell over 200 feet in depth showed no limestone above the Herrin coal. Another showed only G inches of limestone. Others contained as many as three limestone formations. Study of the cores of 25 holes drilled l)y the Union Col¬ liery Company near Dowell furnished data for the following table; Taple 1. —Summarized data regarding the thickness of several limestones and the intervals between them and the Herrin coal. Limestone Average thick¬ ness Average distance of base of lime¬ stone above the top of the Herrin coal Feet Feet 3. Medium-gray, crystalline . 8 82 2. Light-gray, compact . 12M. 49 1. “Cap-rock" limestone . 5 33 In the DiKjUoin area the maximum known thickness of the “cap- rock” limestone is 12 feet, but it averages 4 to 5 feet. It is not known to be more than lOO feet aliove the Herrin coal, and is generally found between 40 and 50 feet above it. STRATA 15ETWEEN THE ‘‘CAP-ROCK’' LIMESTONE AND THE HERRIN COAL 4 he “cap-rock” limestone is commonly underlain by 2 to G feet of black fissile shale known as “draw slate” which contains marine 1 () STRUCTURE OF HERRIX COAL NEAR DUOUOIX fossils. The strata between this and the Herrin coal are mainly of gray, somewhat sandy shale. In places this shale is thin; locally it is absent. Thus at the strip pit of the Black Servant Coal Company one mile west of Elkville the “cap-rock” limestone which is 5 to 6 feet thick rests on 3 or 4 feet of black hssile shale which immediately overlies the Herrin coal. In the Jackson Coal Company mine at Hallidayboro, along the main west entry at the fault just west of the shaft (see fig. 11), the “cap-rock” limestone is about Id feet thick and in places is separated from the Herrin seam by only 8 feet of shale, the upper half Fig. 6. Convergence map showing interval in feet between the base of the “cap-rock” limestone and the top of the Herrin coal. Secs. 31, 32, and 33 in T. 6 S., R. 1 W. and secs. 4, 5, and 6 in T. 7 S., R. 1 W. of which is of the black fissile type. The lower surface of the lime¬ stone is somewhat contorted. These contortions are apparently the result of roll-like disturbances in the underlying shale, and help ex- ])lain the variable thickness of the limestone. Three miles farther north, half a mile south of the shaft of the Kathleen mine at Dowell, the “cap-rock” limestone is 2o feet above the top of the Herrin coal. North of the shaft the thickness of the strata between the Herrin coal and the “cap-rock” limestone increases rather rapidly, as is shown by STRUCTURE OF HERRIN COAL NEAR DUQUOIN 1 ? the convergence map, hgure h. The lines connect ])oints having constant interval between the limestone and the coal, and have the values indicated by the figures on the lines. Four miles northeast of Dowell, at the Majestic Aline of the Equitable Coal and Coke Com¬ pany, this interval is almost 100 feet. The variation in thickness of the strata between the Herrin coal and the “cap-rock” lime.stone seems best explained on the basis that the vegetable matter which later became the Herrin coal accumulated on an irregular surface. That such a surface, probably due to erosion, existed is indicated by the fact that the Herrin coal rests on “fire clay” of variable thickness or even directly on the underlying limestone. Aloreover, while the interval between the Harrisburg and Herrin coals is rather uniform so far as known throughout the Duquoin area, 15 miles east of Herrin it is much greater, averaging about 100 feet.^ W here now there is a Ijelt of thick coal along the eastern side of the Duquoin area, the “cap-rock” limestone is farther above the Herrin coal than is common elsewhere. When the Herrin coal swamp first existed along this belt there was proliably a gentle valley-like depres¬ sion. In this, conditions were such that vegetable material accu¬ mulated more rapidly than it did on the surrounding slightly higher land. Thus when the lake or arm of the sea in which was deposited the clayey material now making up the “blue-band” first came into existence, there was a greater thickness of a peaty material present in the lower belt. Therefore now the “blue-band” is found farther above the base of the coal in the belt of thicker coal. Somewhat later, coal-forming conditions again prevailed, and a greater thickness of peaty material accumulated in the lower area as before, until the surface of the swamp was probably nearly level. As a result of this irregular accumulation of ])eaty material, thicker in the trough than elsewhere, the greatest shrinkage of the peat took ])lace in the trough when the overlying muds were deposited. This permitted a thicker accumulation of mud here than elsewhere before the material forming the “cap-rock” limestone was deposited." Limits of the Area Underlain by the Herrin Coal ACCURACY OF THE BOUNDARY LINE The line across the southwestern part of the map, Plate I, indi¬ cating the western boundary of the Herrin coal seam represents an approximation, except west and southwest of Elkville, where drilling ^ Cady. G. H.. Coal Resources of District VI; Ill. Mining Investigations Bull. 1.5, Plate IV, 1916. 2 Idem, pp. 30-32. 18 STRUCTURE OF HERRIN COAL NEAR DUOUOIN by the Black Servant Coal Company has resulted in its accurate de¬ limitation. ABSENCE OF COAL IN REGION AREA OF POSSIBLE NON-DEPOSITION There are two large parts of the Duquoin area which have not been sufficiently tested by drill holes. These are in the whole northern and northwestern portions of the area ( PI. I) and in a large area cen¬ tered near Aliilkeytown, covering much of the western part of Frank¬ lin County, hut especially pronounced to the west of Sesser and Valier. In the northern portion of this Mulkeytown area the logs of three drill holes show no kferrin coal, indicating the ]iossihility of non-deposition of this seam here. However, since a large jiortion of the northwestern part of Franklin County has not been drilled so far as known, no defi¬ nite statement can be made concerning this area. The theory sketched in the jireceding paragraphs implies the existence of a thick seam of coal in this area. AREAS OF SrBSE(JUKNT EROSION Less than one mile east of the main line of the Illinois Central Railroad near Du([uoin, two elongate north-south areas are shown on Plate I from which it is considered that the Herrin coal has been re¬ moved by erosion. One of the early Pleistocene ice-sheets is respon¬ sible in part, though some of this missing coal was probably removed in earlier epochs. Because the coal seam was so high in these areas, the protecting cover of sediments as well as the coal were removed hy weathering and erosional processes. North of St. John, the boundary of the northern area is unknown, though it is indicated by a doubtful line. STRUCTURF Structural Features Developed Before or Inuring Consolidation SPLITS GENERAL STATEMENT W herever a coal seam is divided into two or more ])arts liy one or more layers of another rock called partings, the seam is said to he S])lit. The term is generally applied only where the jiarting is bicon¬ vex, like a large, very thin lens. A split was proliably caused by the incursion of mud-bearing waters which temporarily and more or less locally interrupted the coal-forming [irocess. Splits are important from the economic viewpoint because they prevent extraction of the STRUCTURE OF HERRIN COAL NEAR DUOUOIN 19 coal under jiresent economic conditions even though they do not in- dnence the grade or quality of the coal. Besides splits the coal has other structural features that were not formed subsequent to consolidation. Although in the main the vari¬ ous strata were at one time all essentially horizontal, minor deposi- tional dips or grades were no doubt originally present. These, and such minor strnctnres as rolls that developed at least in part during the consolidation of the loose sediments into solid rocks, are not con¬ sidered further in this report. THE MAPPING OF SPLIT AKEAS The areas of split coal are shown on Plate I by shading in black. The degree of accuracy of the boundaries are indicated by solid lines, by omission of definite boundary lines, and by the insertion of question marks to show whether the boundaries are certain, rather doubtful, or quite problematical, respectively. N w. Shale Shale parting Shale 0 50 100 15 0 Feet Fig. 7. Diagrammatic cross-section of split just southeast of shaft of Majestic mine. It is probable that patches of unsplit coal of workable thickness exist in the large area of split coal outlined around Mulkeytown. Many sections in this area have never been drilled, so far as it is known. Nine holes, each drilled in a different section, southeast, south, and southwest of Mulkeytown and none over four miles from town are not shown on Plate I since the logs were not obtainable, although it was reported that they all showed a coal seam unfavorable for mining under present economic conditions. The boundaries shown for the south and east sides of this area are particularly questionable. DETAILED DESCRIPTIONS OF AREAS OF SPLIT COAL Majestic mine .—An excellent example of a split has been com¬ pletely delimited in the workings of the Majestic mine. The outline of the split appears on Plate I in the W. ^ of sec. 33, T. 6 S., R. 1 A . a short distance southeast of the shaft. Figure 7 shows a diagram¬ matic cross-section compiled from data obtained from a study in the Shale 20 STRUCTURE OF HERRIX COAL NEAR DUQUOIX mine and the log of a drill hole which penetrates the split area. Figure 8 shows a large-scale diagram of the north side of this split as it ap¬ pears in one cross-section. The thicker part of the seam generally follows the upper side of the shale parting in the iMajestic mine, al¬ though the opposite is true at the place represented in figure 8. The diagram illustrates the fact that the bedding in the coal runs parallel to its surfaces in this split, and the dip of the split coal near the edge averages about 10°. Fig. 8. Detail of north side of split, Majestic mine (E. rib, entry 8 S., main E.). Scale, 1 inch equals 2.8 feet. The west side of a larger split has been delimited in the eastern part of the iMajestic mine, and is shown on Plate I in the extreme east- central part of sec. 23, T. 6 S., R. 1 W.. about one mile east of the shaft. The thicker part of the seam rises steeply here ; entries have been driven on as high as a 30 degree pitch for short distances in this thick U])per part. The area of this split is unknown, as the location of its eastern boundary has not been determined precisely, but it seems probable that it is not much larger than half a square mile in area at the most, as in this district known splits which cause steeply-dipping coal beds are not large. STRUCTURE OF HERRIN COAL NEAR DUQUOIN ^ J . Midkcvfozvii area.—in the northwestern ])art of sec. 15, 1'. (> S., R. 1 E., in the western part of the Old Ben Coal Corporation mine Xo. 11, the workings have delimited what ap|)ears to be the northeast corner of a larger area of split coal. The parting starts with almost paper-thinness near the middle of the 8-foot coal seam along entry 9 \\h off 4 X. off the main west. Farther west it increases very gradu¬ ally in thickness until at the end of the entry, a total distance of (>50 feet, it is about 2 feet thick. The parting is medium-gray shale con¬ taining a little line sand. The blue-hand, which is about 4 inches thick, ])ersists near the middle of the lower part of the seam. On incom¬ plete evidence it seems probable that this split area is but a small frac¬ tion of a much larger area of s])lit coal, as indicated on Idate 1. Ibis area apparently includes Alulkeytown, the southern ]xirt of Chris- tO])her, and a broad area southwest and west of Christopher reaching within two miles of Zeigler, Royalton, Elkville, Dowell, and Old Duquoin. Hallidayboro-Bitsh area. —W hat seems to be a separate area of split coal is outlined on Idate 1 between Hallidayboro and Bush al¬ though the area may be a locality in which the “blue-band” is excessivelv thick. Evidence in favor of this conception apjiears in the eastern j)art of the Jackson Coal Conqiany mine at Hallidayboro in XW\b sec. 29, T, T S., R. 1 W ., where the “blue-band” is reported to increase considerably in thickness, averaging about 18 inches. The most pro¬ nounced feature of this area is the basin shown by structure contour lines in the XIC Ft 'H, T. 1 S., R. 1 \V. It seems probable that this notable structural depression is at least in part due to a split, the contours being based on the lower part of the seam. ORIGIN XW one mode of origin will account satisfactorily for all these various types of splits, although they were formed at the same time that vegetable matter later converted into Herrin coal was accumulat¬ ing in the neighborhood. During the latter stages of the Carbondale epoch, when most of the area was a swamp in which a luxuriant vege¬ tation grew, due to small irregularities in the surface of the land, tem- ])orary lakes or ponds were present in certain localities. The split area completely outlined in the Majestic mine marks the site of one such pond near the close of the Carbondale epoch. After a certain amount of vegetable matter had accumulated at this place, which as indicated in figure 7 was probably marked by a depression in the under¬ lying rocks, physical conditions changed sufficiently so that mud was carried into the pond that already existed there or was formed at that STRUCTURE OF HERRIN COAL NEAR DUQUOIX -v -v time. If a pond existed previously, it was so shallow as to offer no real impediment to the growth of vegetation. Possibly the mud was carried in by a stream and dropped as a delta deposit, notably com¬ pressing the vegetable matter. I'hat this split is a deposit of the delta type is suggested perhaps by its small area, about ‘20 acres, and its relatively great thickness, probably over 50 feet. The split partially outlined in the eastern part of the iMajestic mine may also be of the delta type as it is probably of limited extent. On the other hand, the s]ilit discovered in the northwestern part of the Old Ben Coal Corporation mine Xo. 11 near Christopher seems to be a typical lake or sea deposit. Its gradual increase in thickness indicates a relatively thin deposit over a rather broad area. W bile it is mapped as part of the large Alulkeytown split area, it seems certain that no lake or arm of the sea covered the whole area at one time. This is indicated by the fact that no single shale parting appears to be represented in the different drill hole logs throughout the area. In fact, in some cases several partings appear in a single drill hole log, showing that mud deposits formed in several ponds or lakes that were not contemporaneous. It seems probable that locally these deposits do not overlap, and workable coal might then be present in certain re¬ stricted patches of the large iMulkeytown split coal area. The other area of s])lit coal, that lies between Hallidavboro and Bush, is in part a lake or sea deposit of the type just described. If the structural de|)ression shown on Idate I in the X^E. sec. 27, T. 7 S.. R. 1 is caused by a split, it would seem to resemble the type described in the Majestic mine, and conceivably might represent an old delta deposit. Structural Features Developed after Consolidation GENERAL CONSIDERATIONS The rocks of the Duquoin area have been slightly disturbed sub¬ sequent to their formation. V\ bile as originally deposited and changed by consolidation, certain types of structures were present, such as rolls and splits, subsequent forces have produced much more pronounced irregularities. The coal seam, once essentially continuous, has locally been faulted ; that is, broken and displaced or offset along a more or less irregular surface, the fault plane. In addition, the whole area has been gently warped and now is a part of the large structural basin of Pennsylvanian rocks which covers the southern two-thirds of Illi¬ nois, and adjacent parts of Indiana and Kentucky. The strata of the Duquoin area have a prevailing northeasterly diji towards the center of the basin, except where minor forces have produced local modih- cations. STRUCTURE OF IIERRIX COAL NEAR DUCJUOIN STRUCTURE CONTOURS The structure in an area of gently dipping rocks such as near Duquoin is l)est shown by means of structure contours, although cross- sections, block drawings, sketches, and ])hotographs are also of value. Structure contours afford an accurate representation of structural con¬ ditions ; other methods of showing structure are likely to exaggerate the actual conditions. Fig. 9. —Surface of the Herrin coal as it would appear if all the overlying material were removed. The diagram shows the significance of the struc¬ tural contour line. (Shading by George H. Renshawe.) Contours are lines drawn connecting points on any surface that have the same altitude. This surface may be the land surface, or it may lie a buried surface, such as the top or base of a coal seam. In the case of a buried surface, the lines are known as structure contours, hdgure !) by hTed kl. Kay makes clear the use of structure contours. 24 STRUCTURE OF HERRIN COAL NEAR DUQUOIN County lioiindaries are sketched on this diagram; part of Franklin County is shown in the lower right-hand corner. The vertical dis¬ tance between successive contour lines, known as the contour interval, is arldtrarily chosen. In figure 9, this is 50 feet. On Plate I it is 20 feet except in the northwestern part of the maj), where for lack of sufficient data an interval of 100 feet is used. The surface shown by structure contours on Plate I is the base of the Herrin coal or the top of the underlying beds. This was chosen in preference to the top of the coal, because mine maps generally show elevations along the floors of the entries, which practically correspond to the base of the coal bed. Where the contours are closely spaced, this surface has a rel¬ atively steep inclination; where far apart, it is nearly horizontal. ACCURACY OF THE STRUCTURE CONTOURS 41ie accuracy of the structure contours on Plate I depends mainly upon: ( 1) the accuracy of the base maps used; (2) the number and distrilnition of the drill holes whose logs are used; (3) the accuracy of the logs ; (4) the accuracy of the figures obtained for the elevations of the surface at the locations of the drill holes ; and (5) the accuracy of the elevations shown on the mine maps used. As topographic ma])S were not available for the northern half of the area, there was considerable uncertainty in locating and obtain¬ ing the surface elevations of some holes in that part of the area. In the north-central and northwestern parts, structure contour lines are either not shown, or else the contour interval is increased to lOO feet due to the paucity of both mines and available drill hole logs. 44ie absence of contours does not indicate lack of coal. In general structure contours arc less accurate than surface con¬ tours, because the data from which they are prejiared are less com¬ plete. Data from drill hole logs and other sources give the elevation of the base of the coal seam at a limited number of points. Contours are then drawn which are in harmony with these values, but minor irregularities in the coal seam are generally not shown on the ma|). Solid lines indicate very accurate data taken from levels on mine maps; long dashed lines show doulitful or somewhat scattered data; and short dashed lines are in more or less speculative positions. WARPING DUQIIOIX ]M()XOCI.IXAL FLEXURE The most pronounced feature modifying the general north-east¬ erly dip characteristic of the rocks of the area is the Ducpioin mono- clinal flexure trending N. 10° E. from Elkville ])ast Dowell and one STRUCTURE OF HERRIN COAL NEAR DUQUOIN 25 mile east of Diiquoin. This is clearly shown in figure 9. Previous authors have commonly referred to this as an anticline, Init it is more accurate to call it a monoclinal flexure, since in general opposing dips are absent and the dip is rarely greater than 5° to (P. Idle Du(|uoin monoclinal flexure is shown on Iflate 1 by the close¬ ly-spaced contours drawn on the base of the Herrin coal seam. It is especially marked between Dowell and an area about two miles east of St. John, from where it appears to liroaden out to the north¬ ward gradually, though accurate data are lacking in this area. It can be traced, however, as far north as the Sandoval dome a few miles north of Centralia. South of Elkville or Hallidayhoro it loses its monoclinal character, and the contours bend ofif in a southeasterly to easterly direction conforming to the general regional dip. Except in areas of split coal the maximum dip observed in the strata of the Duquoin monoclinal flexure was 8^4°, which is equiva¬ lent to a grade of per cent. The average easterly dip of the strata on this flexure in T. G S., R. I where it is best developed is about 5° or an 8^. per cent grade. FAULTING GENERAL CITARACTER OF THE FAULTS Most of the faults in the Duquoin area are of the normal type; that is, the fault plane dips toward the downthrow side as in figure 11. In general, therefore, where the coal seam is lost at a fault plane the rule is to follow the fault plane in the direction of the obtuse angle between the coal seam and the fault plane in order to reach the lost part of the seam. Mdiere the fault plane makes an angle of 45° to 50° or less with the horizontal as in figure 12, the fault is likely to be of the reverse type. In this case the fault plane dips toward the upthrow side, and in order to find the hidden part of the seam it is necessary to follow the fault plane in the direction of the acute angle. Eault planes do not extend indefinitely in any direction. Erom a place of maximum vertical displacement the amount of offset gener¬ ally decreases in both directions along the fault line. Although there is a general decrease, in most cases this is not uniform ; the displace¬ ment in a given direction while decreasing on the whole may actually increase locally. SYSTEMS OF FAIMTING Eaulting in the area so far as known is confined to two lielts or systems. One trends about N. 10° E. parallel to and along the east side of the Duquoin monoclinal flexure (PL I). The other trends STRUCTURE OF HERRIN COAL NEAR DUOUOIN •>() east-southeasterly through Hallidayboro and Royalton. The former system contains faults whose individual trends correspond with the trend of the system ; in the latter system, which is the wider, the faults are mainly short cross-faults that trend south-southeast roughly at 45° to the direction of the system. It is to be noted, however, that the two faults showing the greatest amount of displacement which are shown on Plate I lie in this second system and trend approximately parallel to the direction of the system. The N. 10° E. system appears to be short; there is no evidence that it extends beyond the limits of Plate I. Its close association with the Duquoin monoclinal flexure suggests that both structures were pro¬ duced approximately at the same time as a result of the same forces. There is no evidence that lateral compressive forces were of more than minor importance. A gradual settling of the beds on the east side of the flexure accompanied by minor faulting, in part of the graben type, appears to offer a simple yet logical explanation of the present structure. The other system, however, is apparently a part of the “east-west fault zone” described by Cady^ in coal district \ I to the east. Cady shows the system trending about S. 70° E. Extended in a west¬ erly direction, Cady’s “east-west” fault zone would include Dowell. It is possible that the fault mapped by Shaw and Savage^ in the northwestern part of the Murphysboro Ouadrangle also belongs in this system. It seems probable that a cross-pattern of minor faults may lie at the juncture of these two fault systems. The logical area in which to expect such a fault pattern is immediately to the northeast of Elk- ville, where the closely-spaced contours (Idate I) bend sharply to the southeast. Data to prove the existence of such faults are not avail¬ able, though recent development work in the southern part of the Kathleen mine near Dowell has uncovered a fault trending S. 15° E. which seems to be a curved extension of one of the X. 10° E. faults so common in the mine. DESCRIPTTOX OF THE FAULTS Faults near JVcaz'cr .—The largest measured fault in the area is the one trending ESE. in Old Ben Coal Corporation Aline X"o. 20 near WTaver, Whlliamson County. As this mine was closed in the 3 Cady, G. II., Coal Re.sources of District VI: Ill. IMining- Investigations Bull. 15, p. 82, 1916. * Shaw, E. W., and Savage, T. E., U. S. Geol. Survey Geol. Atlas, :Mur- physboro-Herrin folio (No. 185), 1912. STRUCTURE OF HERRIN COAL NEAR DUQUOIN 27 suninier of 1923 no underground studies could be made. It was re¬ ported that where the main N\\\ entry strikes the fault plane, the coal seam has a downthrow of about 44 feet, as shown by a drill hole a short distance beyond the end of the entry. On the south side of the fault plane for a short distance the ccjal di])s 3}4° to the south along the entry, ddie other faults in this mine are much smaller, the next largest one having a maximum known dis])lacement of 22 feet. 44iis was measured in the X\\’. ^ of the X^E. ^ of sec. 2, T. 8 S., R. 1 E., along entry 3 \\k off the main X^. To the southeast this fault disappears in slightly less than one mile. Its extension to the northwest is unknown. 44ie other faults in this mine (Plate I) have maximum throws of about 10 feet. So far as is known, all are of the normal type. Feet Fig. 10. Cross-section (looking north) of main fault in No. 2 mine at Bush. Faults Near Royalton .—It was impossible to see the fault that se])arates the two Royalton mines, but it was described as consisting of a series of parallel slips with a total downthrow of about 40 feet on the southwest side. The coal bed dips gently to the northeast on both sides of the fault zone; on the northeast side it is very gentle; on the other side it is slightly steeper, except just at the fault where it is at a rela¬ tively high angle. This belt of steeply dipping beds to the northeast is too narrow to be shown by contours on a map the size of Plate I; thus the large throw of this fault is not indicated. There is only one fault of much importance exposed in the work¬ ings of Mine Xo. 2 of the W estern Coal and Mining Company in the SE. sec. 31, T. 7 S., R. 1 E., approximately one mile north of Bush. It is the one shown by dashed lines on Plate I curving in a northerly direction. It is a normal fault with the downthrow on the east side. STRUCTURE OF HERRIN COAL NEAR DUOUOIN \\ here the 1-2 E. entries off the main N. intercept the fault, the throw is blit 10 feet; but about 1100 feet farther northwest, where the 3-4 E. entries off the main X. intercept it, the throw is 21 feet. The 5-6 E. entries off the main N. end at the fault plane. It appears that the throw along this jilane increases to the north, where it may become as much as 50 or 60 feet. In cross-section along the 4 E. entry off the main X"., this fault (fig. 10) is double, and the two planes are about 30 feet ajiart. Extending northeast from this fault is postulated a short fault with a maximum throw of about 60 feet with downthrow on the northwest. Extending in a northwesterly direction is shown on Plate I a possible fault with a maximum downthrow on the northeast side of about 100 feet. It appears to die out in Jackson County. These two hypothetical faults are based on drill hole records. Pig. 11. Cross-section of fault in the main west entry of the mine of the Jackson Coal Company at Hallidayboro. The dashed line shows the profile of the base of the entry. faults near Hallidayboro. —44ie two main faults indicated on Plate I in the workings of the mine of the Jackson Coal Company at Hallidayboro are both of some interest. The larger fault, which is of the normal type, is shown diagrammatically in figure II where it cuts the main west entry about 400 feet from the shaft. The displacement in the ])lane of the section is approximately 30 feet.'"^ It is thought that this is nearly a maximum figure for this fault, and that the throw is smaller to the northwest and southeast. At the north end of entry 9 Xb off the main \\b in the XE. SE. J4 sec. 19, T. 7 S., R. I \\b, the throw of this fault is only 7 feet. Along- the fault plane there i.s a vein of calcite about an inch thick, asso¬ ciated with which are numerous capillary, fibrous crystals of melanterite (FeSOt TH^O) a pale green mineral with a vitreous luster and a pronounced astringent, metallic taste. Both of these minerals are commonly present along the fractures found in the coal of the area. STRUCTURE OF HERRIN COAL NEAR DUQUOIN 2U The small fault, as indicated in figure 1*T apjiears to he of the reverse type. This fault was probably caused by compressive forces, and its position fixed by a pre-existing roll. The roll in the coal seam on the west side of the fault is better shown in the main east entry than it is in the back east entry represented in figure \2. Along the main east entry a stringer of coal about (> inches thick branches up from the fault plane, and there is no actual faulting along the west side of the roll, such as that indicated in figure \2 by the dotted line. The bedding of the coal within the rolled area is notably disturbed, in places appearing slightly contorted. The apparent throw of this fault is 9 to 10 feet where crossed by the main east entry. It is ])robably less than this to the northwest and southeast, as many rooms in the old workings were holed through it. West Fig. 12. Cross-section (looking south) of fault of the reverse type in the back east entry of the mine of the Jackson Coal Company at Hallidayboro. The dashed lines show the profile of the entry. Scale, 1 inch equals about 13 feet. Faults near Dozvell .—From the viewpoint of faulting, the most interesting mine in the area is the Kathleen mine at Dowell. The workings of this mine are shown in some detail on Plate II. With one exception all the faults so far discovered trend in a direction paral¬ lel to the Duquoin monoclinal flexure. They are limited to the eastern and southern parts of the workings. In the rest of the mine the coal seam has a rather uniform easterly dip of approximately 3^°. Figure 13 is a generalized cross-section of the faulted portion of the main east entry with a few minor displacements omitted. Faults Nos. 2, 5, f), and possibly 7 have smaller displacements to the south than indicated in the figure, while the reverse is true of Nos. 1 and 4. According to recent report, fault No. 1 has a throw of 35 to 40 feet about half a mile 30 STRUCTURE OF HERRIX COAL NEAR DUOUOIX south of the main east entry, where Xo. 5 coal seam appears in the face of 9 and 10 east entries off the main south entry. Fault X^o. 3 has a larger displacement a quarter of a mile to the north, but still farther north it dies out rapidly. Presumably it has a smaller displacement to the .south of the main east entry than is indicated in hs^ure 13. The only other important fault so far discovered in the Kathleen mine (see PI. II) is about 500 feet west of XT. 1. but is south of the main east entry. Figure 13 shows that the dominant faulting in the Kathleen mine is of the normal type, and that the net result of the faulting is a minor structural trough. This trough-like character dies out rapidly to the north, due to the lack of persistence of fault X^o. 3 along the west side. To the south the detailed conditions are unknown. ^^Tst of Dowell, as well as east of the faulted area (see Plate I), the coal seam is nearly horizontal, though it does have an extremely gentle easterly dip. '1-2 S. entries 0 100 200 Feet lOO Ft above sea level Fig. 13. Profile of faulted part of the Herrin coal seam along the main east entry of the Kathleen mine at Dowell. Fault Xo. 2 is not shown on Plate I. Although the major faulting in the Kathleen mine is of the normal type, there has keen some reverse faulting on a small scale, as shown by the detailed sketch (fig;. Id). It seems there have been two movements here; the earlier a normal fault, the later a reverse fault. The first fault was along the plane including A-B and its now offset continuation C-E. The throw amounted to about 1 feet, with downthrow on the west side. The second fault was horizontal along B-C with a displace¬ ment of 5 feet 9 inches in a direction perpendicular to the strike of the earlier fault. It is to be noted that the plane of the second fault in¬ cludes the top of the downfaulted part of the coal seam, and the “blue- band” in the other part of the seam, both of which are relatively weak surfaces. It was not possible to determine the actual directions of movement, but many of the fault planes in the Kathleen mine show apparently horizontal slickensides, as if at least in part the strata moved laterally along the fault plane. Essentially identical relationships are seen in other parts of this mine, such as along the main east entry whgre it cuts faults X'^os. 1 and STRUCTURE OF TIERRIX COAL NEAR DUOUOIX ;n 2. Aloreovcr, sonic of the cross-sections of the larger faults show characteristics which are in harmony with these relationships. Thus in hgure 15, the folding of the bedding planes in the coal indicates that com])ressive forces followed those which caused the typical normal faulting. Although the hedding planes in the coal on the west side of this fault jilane jirohahly once di]iped down rather steeply to the east, as would have been caused by the drag of the down-dropping strata on the east side of the plane, later compressive forces jiresum- ahly modihed this dip, or even reversed it, as shown in hgure 15. Thus the liedding of the coal scam in the upper part of the diagram near the fault })lane is almost parallel to the fault ])lane, hut the strata are Watt East 0 1 2 3 4 5 Feet Pig. 14. Detailed sketch cf fault in north rib of entry 5 W. (100 feet west of the main south) in the Kathleen mine at Dowell. bent upAvards. The maximum thickness of the gouge zone shown is aliout six inches, and it is made up almost entirely of shale. Ihjlilts cast of Diiquoiii .—The map of the abandoned Davis or Queen mine in the NW. hi tif sec. 15, T. (5 S., R. 1 Ah, shows two nearly parallel faults (PI. 1) trending in about the same direction as the faults in the Kathleen mine. It seems probable that these pro¬ duce a shallow structural rift, similar to the trough of the Kathleen mine (lig. l-l). The west fault is the larger, and has a maximum throw near the shaft, where it amounts to about 20 feet, but decreases to about eight feet before it leaves the mine workings. The offset of / 32 STRUCTURE OF HERRIN COAL NEAR DUQUOIN the east fault is only about 10 feet. Further data obtained on the faults in this old mine are highly conflicting, although it is known that to the south of the shaft the east fault dies out within the mine work¬ ings. From a study of the logs of available drill holes, it seems prob¬ able that the west fault extends as far south as the SE. ^4 of ^oc. 21, T, 6 S., R. 1 \\b, as shown on Plate L Base of entry 0 12 3 Feet Fig. 15. Cross-section of fault No. 3 (fig. 13), north rib, main east entry, Kathleen mine at Dowell. Curved lines indicate prominent bedding planes in the coal seam. PRACTICAL ECONOMIC ASPECTS \k\LUE OF THE Structure Contour Map, Plate I Plate I shows the lay, the continuity, and the areal limits of the Herrin coal, the approximate location and extent of certain areas of STRUCTURE OF HERRIN COAL NEAR DUOUOIX •> •> split coal and faults whose displacements can be computed from con¬ tours on both sides of the fault lines. With the aid of the structure contours it is ]) 0 ssible to determine the de])tb to the Herrin coal seam at any point where the surface elevation is known. If the coal is above sea-level its elevation as shown by contours should he subtracted from the elevation of the surface to hud the depth; in case the coal is below sea-level, these two elevations should lie added. Effects of Faulting on ^Mining ^Methods at Dowell In driving the main cast entry of the Kathleen mine, when fault Xo. 3 (hg. 13 and Id. II) was encountered, the entry was continued sloping rather steeply to the east until it again reached the base of the seam near fault No. d. On continuing to the east, faults Nos. 3, G and T were encountered and necessitated a rather rapid rise in the level of the entry, d'he result was two steep grades o|)posing each other along a main haulage way. Later the roof of the main east entry was shot down until the entry was nearly level between faults Nos. 3 and T. The back east entry was not changed, however, as it was needed to remove the coal from the base of the trough. Entries driven north and south from the back east entry at the base of the trough are used for the removal of the low coal. The south entry was driven slightly west of south to parallel the faults. Entries running west from entry 1 south off the back east can be continued across the trough and reach coal X"o. 5 with no pronounced change in level. Thus if in the future it is desirable to mine this lower seam, it can he done without deepening the shaft. Importance of Drilling Before the shafts of prospective new coal mines are started, it is economical to ascertain the conditions affecting the coal seam by drilling. Along the faulted belts jtreviously described (]). 25), or in the areas outlined on Plate I as being underlain by split coal, core¬ drilling is highly desirable. Sufficient holes should be put down to leave no doubt about the character, continuity and attitude of the coal. \\ here the coal seam is siilit, drill cores would show the thickness and characteristics of the interbedded shale. An operator should he com¬ petent to pass on the desirability of the prospective location from this point of view. Wdiere a seam is not essentially horizontal and is faulted, more holes might be necessary, and it would be advantageous to the prospective operator to have an ex])erienced geologist in consultation to advise on the locations of holes and the interpretation of the struc- STRUCTURE OF HERRIX COAL NEAR DUOUOIX ;u ture from the cores, \\hth careful, thorough work it would be pos¬ sible to locate a fault where the throw was large enough to be a very important factor in mining;—that is, greater than 10 or 15 feet. W here the coal seam is not split, and the strata are essentially horizon¬ tal, churn drill holes would probably give satisfactory information wiih regard to depth and continuity of the coal and location of faults. I! ■I-Vj-/- :■, S?»r"a.^ ..T® i., ^.--1. : S» -~..,' i#lf ■■:.■"•’? '- ■ -■fi* V>.i- ' ► ■\^*'.' 'v-' ■ -'• p^:;. j;§jjf:, ^ r-- - ..,^* ■i. V' b *tirJ-' . . .: .•«....**•«• w • V ■»^jS>' •P. %■ .. „... ■ ■ ‘".'/.J - ■^- .r '*' v'iI'jS V' ' '■’^JU I* ^ t . *; '■■^ i>£% ,-■ i r > : c ' r^: ■.■ 0}^^:.K,':'‘u .. f . « - . .Jt ” . *■ , i; ^ ' 13 .•^ .V: '-4 V-. I -TT-*?--* k?.)r M / ... S-4;,. ■Bj^j.-V-V - -a . li- .V J I *- w «‘>» • ' » '•W i'-‘ > - -. ;’7 '^f ifK' ■ V *'- . -Sr ♦ ^> r 4 V f > ^ -.* - V \ V. 4‘'' ■ m.^X7'‘X 'r& * -4r • ... a. jk ■» .r ' Ik •..' •K* •-f- ^ . j*. I .■^v* i<' ’ ^.*'- ■ *•'’'•♦.•■***'►■■ , , ;ir »' .L-^ . ., >- ‘u^: . f : ■ sIl.* :•-'•'*■■: .•'. ,, ,/'•■. . ,' * » ^ j fc •. .-r ^ * - i ? - Downthrow side of fault. Shipping mine, entrance by shaft. Shipping mine, entrance by slope. A. Strip pit. Local. Abandoned. Drill hole. Structure contours drawn on the base of the Herrin (No 6) coal with reference to sea level. Certain. Doubtful. Problematical. LIST OF (Active Map No. Town 1 Bois 2 Tamaroa, 3 Tamaroa. 4 Sunfield. 5 St. John. 6 St. John. 7 Duquoin. 8 Duquoin. 9 Duquoin. 10 Duquoin. 11 Duquoin. 12 Duquoin. 13 Dowell. 14 Elkville. 15 Hallidayboro. 16 Ward. 17 Ward. 18 Hurst. 19 Bush. 20 Royalton.... 21 Zeigler. 22 Zeigler. 23 Christopher. 24 Christopher. 25 Christopher. 26 Valier. 27 Sesser. 28 Sesser. 29 Weaver SHIPPING MINES IN THE AREA or only temporarily idle in 1923) Company Mine No. or Name WASHINGTON COUNTY Kuhn Colliery Co. perry county .Victory Colliery Co^. Little Muddy Fuel Co. .Bailey Bros. Coal Co. .Gayle Coal Co. .Paradise Coal Co. Equitable Coal and Coke Co.. .Scott-Smith Co. .Jewel Coal Co. .Jewel Coal Co—; ‘ ‘ h'’/V ’ .Rutledge and Taylor Coal Co JACKSON COUNTY .Union Colliery Co..... . Black Servant Coal Co. .Jackson Coal Co... ..Midway Coal and Mining Co . .Jackson Peacock Coal Co. . Bradbury-Scullion Coal Co... Diamond . Strip pit . Paradise .Majestic .Strip pit .No. 1 .No. 2 . Security . .Kathleen .. Strip pit .No. 1 .No. 1 Slope mine Slope mine FRANKLIN COUNTY Western Coal and Mining Co... Franklin County Coal Co. Bell and Zoller Mining Co. Bell and Zoller Mining Co. Old Ben Coal Corporation. Old Ben Coal Corporation. .Old Ben Coal Corporation. .Valier Coal Co. Old Ben Coal Corporation...... Southern Gem Coal Corporation .No. 2 . .North mine Zeigler, No. 2 Zeigler, No. 1 .No. 12 .No. 10 .No. 11 .No. 1 .No. 16 .No. 2 WILLIAMSON COUNTY Old Ben Coal Corporation No. 20 H * ILLINOIS STATE GEOLOGICAL SURVEY REPORT OF INVESTIGATIONS. NO. 5. PLATE 1 R. 2 W Sunflcld ,SL OuQMln R 2 W LEGEND. Boasduy af irwkatvb H « r r i o (No. II coal. Arvw In whlrk tha Itarrin («tl bH (>«*« tvmoTCd br analen. Ar««i of tidit Hatrla cool no* vorkobi* under irM i n t eeo- nomk rendtUon*. o» outUnod Id min* ooAlact. r*u)(, wdatn. UoiTBIhio* •U* of hulL Shipptai mis*, ntnse* by kluft. Shlpplnt mlno, entrance b; *lop*. Strip pit. Local. Abandoned. UrlU bole. SlfMctxira contour* dnan on lb* boM of the n*mn (No. I) coal with reloranca to a*a lerrt Certain. LIST r SHIPPIXn MIMtS IV TIIK ARKA ( Arlll*l anil O>lio Co.. .-Uredl-Wtnllh CV).. . Jeoel (Val <.to. . J.*»l (Vwil tV(.. .. . Kulle-lc* ami Tavlor Cool IS. JACKSON COltSTY . Union Colllrry Co. . llUek ServanI Coal Co.. .TeeVann Coal Oo. Ui.lvrav Coal and klinini Oo.. ..,.pn i IT Wad .Jack*on Teewk Coal Oo. Slo|-* mine II lluiel.llradlnir) Scullion Coel CO. HIm|i* mix* FRASKUS COUNTY 1( Riitb.Uealrm Coal awl Minlnd Oo.No 9 30 Koyallon... Franklin County C-