JO~ s /' • I' • ... ' 1/' t$ 6. ~ n'" t 14.GS: .f.~~?[; . • 5ft' RPI 105 C.)
STATE OF ILLINOIS DWIGHT H. GREEN, Govtrnor DEPARTMENT OF REGISTRATION AND EDUCATION FRANK G. THOMPSON, Dirtctor
DIVISION OF THE STATE GEOLOGICAL SURVEY M. M. LEIGHTON, Chit/ URBANA
REPORT OF INVESTIGATIONS-No. lOS
I-SUBSURFACE RELATIONS OF THE MAQUOKETA AND "TRENTON" FORMATIONS IN ILLINOIS BY E. P. Du BOis I , '
II-PETROLEUM POSSIBILITIES OF MAQUOKETA AND "TRENTON" IN ILLINOIS
BY CARL A. BAYS
PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS
URBANA, ILLINOIS 194S STATE OF JLLINOIS DWIGHT I-I. GREE , Governor DEPARTMENT OF REGISTRATION A D EDUCATION FRANK G. THOMPSON, Director
DIVIS!O OF THE STATE GEOLOGICAL SURVEY M. M . LEIGHTO , Chief URBA A
REPORT OF INVESTIGATIONS-No. 105
I-SUBSURFACE RELATIONS OF THE MAQUOKETA AND "TRENTON" FORMATIONS IN ILLINOIS
BY E. P. Du BOis
II-PETROLEUM POSSIBILITIES OF MAQUOKETA AND "TRENTON" IN ILLINOIS
BY CARL A. BAYS
PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS
URBANA, ILLINOIS 1 9 4 5 ORGANIZATION
STATE OF ILLINOIS RON. DWIGHT H. GREEN, Governor DEPARTMENT OF REGISTRATION AND EDUCATION HON. FRA K G. THOMPSON, Director
BOARD OF NATURAL RESOURCES AND CONSERVATION RON. FRA K G. THOMPSON, Chairman NORMAN L. BOWEN, PH.D., D.Sc., Geology ROGER ADAMS, PH.D., D.Sc., Chemistry LOUIS R. HOWSON, C.E., Enginuring *WILLIAM TRELEASE, D.Sc., LL.D., Biology EZRA JACOB KRAUS, PHD., D.Sc., Forestry ARTHUR CUTTS WILLARD, D.ENGR., LL.D. Prnident of the University o/ Illinois
GEOLOGICAL SURVEY DIVISION M. M. LEIGHTON, Chit/
(83335-2,500-6-45) ~2 SCIENTIFIC AND TECHNICAL STAFF OF THE S TATE GEOLOGICAL SURVEY DIVISION 100 Natural R esources BuildinK, Urbana
M. M. LEIGHTON, PHD., Chief ENID TowNLEY, M.S., Assistant to the Chief VELDA A . MILLARD, j unior Asst. to the Chief HELEN E. McMORRIS, Secretary to the Chief EFFIE HETISHEE, B.S., Geological Assistant
GEOLOGICAL RESOURCES Stratigraphy and Paleontology J. MARVI ·W ELLER, PH.D., Geologist and H ead Coal CHALMER L. CooPER, M .S., Assoc. Geologist G . II. C\ ov, Pn.D., Senior Geologist and H ead L. C. McCABE, Pn.D., Geologist (on leave) Petrography R. ]. lhLFI;>;ST!:-IE, M.S., Alech. Engineer RALPH E. GRIM , Pu.D., Petrographer CHARLES C. BoLEY, M.S., Assoc. Mining Eng. RICHARDS A. R owLAND, PH .D., Asst. Petrographer HEINZ A . L o\\ENSTA~t, PH.D., Assoc. Geologist (on leave) BRYAN PARKS, M.S ., Asst. Geologist WILLIAM A. WHITE, B.S., R esearch Assistant EARLE F. TAYLOR, M.S., Asst. Geologist (on leave) Physics RALPH F. S·1RETE, A.M., Asst. Geologist R . ] . PIERSOL, PH.D., Physicist M. W . PuLLEN , ,IR. , M.S., Asst. Geolo gist_ B . J. GREE:-IWOOD, B.S., 1\II ech. E ngineer R oBERT M. K osANKE, M.A., Asst. Geologut RoBERT W. ELLIN<.WOOD, B.S., Asst. Geologist GEOCHEMISTRY GEORGE M. WILSON, M.S., Asst. Geologist ARNOLD EDD INGS, B.A., R esearch Assistant fRANK H. R EED, PH.D., Chief Chemist (on leave) ELIZABETH R oss MILLS, M.S. , R esearch Assistant R AYMOND SIEVER, B.S., R esearch Assistant (on leave) Coal JoHN A. HARRISON, B.S. , R esearch Assistant G. R. YouE, PH.D., Chemist (on leave) HERMAN S . LEVINE, B.S ., R esearch Assistant MARY E. BAR XES, B.S., Research Assistant MARGARET PARKER, B.S., R esearch Assistant Industrial Minerals ELIZABET.II LoHMANN, B.F.A., T echnical Assistant ] . S. MACHIN, PH.D., Chemist and H ead DELBERT L. HANNA, A.M., Asst. Chemist Industrial Minerals Fluorspar J. E . LAMAR, B.S., Geologist and H ead J l. B. WIL LMAN, PH.D., Geologist G. C . fiNGER, PH.D., Chemist R oBERT M. GROGAN, Pu.D., Assoc. Geologist OREN F. WILLIAMS, B. ENGR., R esem·ch Assistant R ouERT T. ANDERSON, M.A., Asst. Physicist RoBERT R. R EYNO LDS , M.S., Asst. Geologist X-Ray and Spectrography l\1,\RGARET C . GoDwiN, A.B., Asst. Geologist W. F. BRADLEY, Pu.D., Chemist Oil and Gas Chemical Engineering A. II. BELL, PH.D., Geologist and Head H. W . ]ACKMAN, M.S.E., Chemical Engineer CARL A. BAYS, Pn.D., Geologist and Engineer P. W. HENLINE, M .S., Assoc. Chemical Engineer FREDERICK SQUIRES, B.S., Petroleum Engineer ]AMES C. McCuLLOUGH, R esearch Associate ·TEWART FoLK, M.S., Assoc. Geologist (o n leave) ]A~IES H . HANES, B.S., R esearch Ass-istant ERxEsT P. DuBois, PH.D., Assoc. Geologist (on leave) DAviD H. SwANN, PH.D., Assoc. Geologist L EROY S . MILLER, B.S., R esearch Assistant VIRGINIA KLI NE, Pu.D., Assoc. Geologist (on leave) PAuL G. L ucKHARDT, M.S., Asst. Geologist (on leave) Analytical W.\YNE F. MEENTS, Asst. Geologist 0 . W. R EEs, PHD., Chemist and Head ]AMES S. YoLT0:-1, M.S., Asst. Geologist H owARD S. CLARK, A.B., Assoc. Chemist RouERT . M . URASH, B.S., Research Assistant L. D. McVICKER, B.S., Chemist .:\IARGARI::T SA NDS, B.S., R esearch Assistant WILLIAM F. WAGNER, M.S., Asst. Chemist CAMERON D. L Ewis, B.A., Asst. Chemist Areal and Engineering Geology HERBERT N. HAZELKORN , B.S., R esearch Assistant \VILLIAM T. ABEL, B.A., R esearch Assistant GLORGE E. EKBLAW, Pn.D., Geolo gist and H ead MELVIN A. R EBENSTORF, B.S., R esearch Assistant RI CHARD F. fiSHER, M.S., Asst. Geologist MARIAN C . STOFFEL, B.S ., R esearch Assistant j EAN L Ois R ossELOT, A.B., R esearch Ass·istant Subsurface G eology MINERAL ECONOMICS L. E. WoRKMAN, M.S., Geo logist and Head CARL A. BAYS, P11.D., Geologist and Engineer W. li. VosKUlL, PH.D., Mineral Economist C. L ELAND lloRuERG, Pu.D., Assoc. Geologis t DouGLAS F. STEVENS , M.E., R esearch Associate R oBERT R. SToR,t, A.B., Assoc. Geologist INA HAMRICK , A.B ., R esearch Assistant AR:-~OLI> C. MAsoN, B.S., Assoc. Geologist ETHEL M. K ING, R esearch .4ssistant (on leave) :\1ERLYN B . Bt: IILE , M.S., Asst. Geologist PUBLICATIONS AND RECORDS FRANK E. TIPPI E, B.S., Asst. Geolo gis t GEORGE E. EKBLAW, PH.D., Geologic Editor PAUL H ERBERT, jR., B .S ., Asst. Geologist CuALMER L. CooPER, M .S., Geologic Editor CnARLES G. ] o ii :-.SON, A.B., Asst. Geologist DoROTHY E. R osE, B.S., T echnical Ed·itor (on leave) MEREDITH M. CALK ti Consultants : Ceramics, CuLLEN W. PARMA LEE, M.S., D.Sc., and RALPH K. H u RSH, B.S., University of Illinois lvf.echanical Engineering, SE ICH I K oNzo, M.S., UniVersity of Illinois T opographic Mapping in Cooperation with the United States Geological Survey. This report is a Contribution of the Oil and Gas and Subsu rface Geology Divisio ns. May I, 1945 CONTENTS I-SUBSURFACE RELATIONS OF THE MAQUOKETA AND "TRENTON" FORMATIONS IN ILLINOIS, BY E. P. Du Bors PAGE Introduction .. 7 Maquoketa formation .. 7 Galena (Kimmswick ) formation ...... 17 Decorah formation ...... 21 Plattin (Platteville) formation . 23 Joachim formation . . 25 Dutchtown formation. 27 Discussion of cross-sections . 28 Regional interpretation of the pre-Decorah beds ...... 29 II-PETROLEUM POSSIBILITIES OF MAQUOKETA AND "TRENTON" IN ILLINOIS, nY CARL A. BAYS Maquoketa possibilities ...... 35 Galena possibilities ...... 35 Decorah-Plattin-Joachim possibilities ...... 37 Dutchtown possibilities ...... 37 Exploration ...... 37 Summary ...... 38 ILLUSTRATIONS FIGURE P AGE Isopach map of the Maquoketa formation .. 8 2 Diagrammatic sections and correlation of the Maquoketa formation in Illinois and Iowa .. 9 Maps of the facies of (A) upper Maquoketa, (B ) middle Maquoketa, and ( C ) lower Maquoketa formation in Illinois 10 4 Correlation chart of the Middle and Upper Ordovician strata in Illinois and eastern Missouri ...... 18 Isopach map of the Galena formation . 20 6 Isopach map of the strata from the base of the Galena to the base of the Dutchtown formation ...... 30 7 I sopach map of the strata from the top of the Galena to the base of the Dutchtown formation ...... 31 Diagram showing transgressive relations of the St. Peter sandstone and superjacent formations in Illinois ...... 32 9 Area of possible occurrence of sandstones in the Maquoketa formation 34 10 Petroleum possibilities of Galena st,ra-t;l . 36 1~. PLATE Cross-section through the Maquoketa and "Trenton" strata in Illinois from north to south ...... PocKET Cross-section through the Maquoketa and "'I renton" strata in Illinois from east to west ...... P OCKET SUBSURFACE RELATIONS OF THE MAQUOKETA AND "TRENTON" FORMATIONS IN ILLINOIS BY E. P. Du Bors INTRODUCTION limestone, Divine3 limestone and Thebes• sandstone have been applied locally to parts This report is a brief discussion of the of the Maquoketa formation but it appears subsurface stratigraphy and relations of the that none of these, except possibly the Maquoketa, Galena, Decorah, Plattin, Divine limestone, are consistent strati Joachim, and Dutchtown formations in graphic units. Illinois, based on information derived Instead, the formation generally, es principally from studies of samples of well pecially in northern and central Illinois, cuttings and from electric logs. appears to be divisible into three principal AcKNOWLEDGMENTs parts: an upper part that is dominantly green shale, a middle part that is domi The writer is indebted to several member: nantly limestone or dolomite, and a lower of the Geological Survey staff for sug part that is dominantly brown shale, in gestions and criticism in the preparation places calcareous (fig. 2) . However, cer of this report, including Carl A. Bays, tain lithologic variation is typical through Geologist and Engineer; A. H. Bell, out the formation. The ~pper_ green shale Geologist and Head of the Oil and G as commonly has thin lenses of limestone or Division; L. E. Workman, Geologist and dolomite, the middle carbonate zone may Head of the Subsurface Geology Division; have thin green or brown ..shale layers, and George E. Ekblaw, Geologist and Head of the lower brown shale· may contain inter the Division of Areal and Engineering bedded argillaceous limestones or dolomites Geology ; and ]. Marvin Weller, Geologist and lenses of green shale. In some areas and Head of the Division of Stratigraphy nearly the entire sequence is composed of and Paleontology. argillaceous limestone or dolomite; in other areas it consists of shale. The color 1 MAQUOKETA FORMATION of the beds appears to be more consistent LITHOLOGY AND SuBDIVISIONs than does the gross lithology. The forma tion is nearly alway~ green or gray in the The Maquoketa formation occurs in all upper portion and brown in the lower, w:th of Illinois except in the north-central some interbedding of the two colors in the and northwestern parts and locally in the middle. Ih certain parts of the State, princi western part (fig. 1). It consists dominantly pally the southwestern, a two-fold division of shale but includes much limestone, dolo appears to be more sui table : an upper green mite, siltstone, and sandstone. Lateral in~rb.edded silty shale or sandstone and gradation from one lithology to another a low~r generally. brown calc~reous shale is common, even within relatively short with occasiona:r siltstone or sandstone·· lenses. 2 distances~ Specific names, such as Fernvale Other systems of divisions ma)r apply in 1 amed for Little Maquoketa River in Dubuque County, isolated areas, "but necessarily are limited I owa, along which bluish and brownish locally calcareous or arenaceous shales are exposed between the Galena and 3 amed for exposures of coar~e-grai ned crystalline light "Niagara" limestones. White, C. A., Geological Survey of colored limestones near Divine Station, Grundy County, I owa, vol. I , pp. 180, 181, 1870. Illinois. Lamar, L .E., . and. Will!nan, H. B., Ill. Geol. 2Named for exposures of soft green and chocolate Survey Rept. Inv. ·23, 1~ H-. colored shales with interbedded coarsely crystalline lime 4Named for exposures of very fine-grained fandstone and stone near Fernvale, Williamson County, Tenness ee. siltstone in the vicinity of Thebe<, Alexander County, H ayes, C. W. and Ulrich, E. 0., U. S. Geol. Survey Geo Illinois. Worthen, A. H., Illinois State Geological Survey, logic Atlas, Columbia Folio No. 95, p. 2, 1903. . vol. 1, p. 139, 1866. [ 7 J 8 MAQUOKETA AND "TRENTON" FORMATIONS ISOPACH MAP OF THE MAQUOKETA FORMATION BY E. P. Ou BOIS JANUARY I, 1945 ·I ! .-----i __,..1·---: ____ ,__1 <"o , .l •.,..../ .I ~ - --~ _r-r • ·L ____1-, 1 --1! I' L' , • i I . ·------,-! I ,- _,_- - -,----- I DATUM POINT ...... BOUNDARY BETWEEN SILURIAN SYSTEM AND MAQUOKETA FORMATION --JOO THICKNESS OF MAQUOKETA FORMATION AREA IN WHICH MAQUOKETA FORMATION CROPS OUT OR IS COVERED ONLY BY GLACIAL DRIFT OR PENNSYLVANIAN STRATA; THICKNESS VARIABLE SCALE 10 20 30 40 ~0 FIG. 1 SUBSURFACE RELATIONS 9 Iowa Northern Southern Illinois Illinois .. · ·...... ·.·.·.:: .·· .·.· FORT ATKINSON CLERMONT----+-- ...... --+------+-""'----'---'------F;;;;;;;;;;;;;...;::;;:=-r~ :z 1--''---=1~~ <.? 1---:l~---,~ _..J t---''---y--.L.-~ w 1--...... --J'---...... 1 [] SANDSTONE ~ LIMESTONE D SILTSTONE § DOLOMITE • 0 • 8"-43 SHALE o:o:o uoEPAUPERATE ZONE'' Frc. 2.-Diagrammatic sections and correlation of the Maquoketa formation in Illinois and Iowa. geographically. The three-fold or two occur commonly as a veneer over the rest fold divisions mentioned above are appli of the formation but in many places are cable throughout the greater portion of the also interbedded with the green shale. Oc state. currences of similar clastic deposits at the The upper green shale zone (fig. 3) top of the Maquoketa in northeastern is present throughout Illinois. In Kane Illinois are known but previously have been County and adjacent areas, the shale is tentatively assigned to the Alexandrian replaced by a pale green, white or light senes. gray more or less argillaceous dolomite, The middle carbonate unit (fig. 3) which appears to the writer to represent a which has been called the Divine limestones lateral change in facies of the upper unit. in Grundy County, is widespread in north Elsewhere the shale is locally calcareous. eastern and central Illinois, occurring as By far the most important variation in far south as Marion County. Where best lithology is the appearance of siltstone or developed it consists of finely to coarsely sandstone towards the south. Notable thick crystalline limestone or dolomite, common nesses of siltstone or sandstone, similar in ly characterized by a mottled white and texture to that which crops out at Thebes gray or brown color, apparently due to in the southwestern part of the state, occur fossil inclusions. Chert, although not com- throughout the southern and eastern parts of the state. These arenaceous deposits 6Lamar and Willman, op. cit. 0 c Q SHALE [I] SILTSTONE AND SANDSTONE m LIMESTONE Frc. 3.-Maps of the facies of (A) upper Maquoketa, (B) middle Maquoketa, and (C) lower Maquoketa formation in Illinois. SUBSURFACE RELATIONS 11 mon, is present and usually is mottled applied. It should be noted that these beds white and blue, fossiliferous, and pyritic. decrease in carbonate content upwards from Usually no precise top or bottom can be the base; in very few instances does the assigned to the unit. To the south, this zone mottled character, typical of the pure lime loses its coarsely crystalline character, be stone occur within the brown shale rather comes more argillaceous, and finally appears than at the base. to grade laterally into the shales and silt Siltstones and sandstones of considerable stones of the green and brown clastic units, thickness may occur in the brown shale thus giving rise to the two-fold division unit, but not as commonly as they do in that is typical of parts of southern and the upper green unit. If color alone is used southwestern Illinois. as a criterion, the sandstones and siltstones The lower brown shale unit (fig. 3), near Thebes are properly included in this like the green shale, is recognizable over lower division, and constitute the major most of the State. It generally possesses a part of the formation in that area. high carbonate content and in many areas The variability of the Maquoketa and grades laterally into thinly bedded very the readiness with which sandstones may argillaceous limestones or dolomites. With grade laterally and vertically into shales, very few exceptions, pure carbonate rocks and the shales into limestones, as well as are not present in this part. Occasionally, the possibility of one color grading into the however, the lowermost beds have a coarsely other, can not be too strongly emphasized. crystalline mottled white and gray character The following sample studies are presented similar to that of the middle limestone in with a view to emphasizing this variability the north. To such beds, and to others in rather than of demonstrating any consist the basal section which have a high carbon ency of either a two or three ~ fold division of ate content, the name Fernvale has been the formation. WELL N o . 1-DAvis AND BLACKMA , MISSISSIPPI PALISADES STATE PARK SEC. 34, T. 25 N ., R. 3 E., CARROLL COUNTY Description Thzckneu feet Shale, slightly dolomitic, brownish, pinkish, and bluish-gray, weak; limestone, dolomitic, partly argillaceous, buff, very finely crystalline . 20 Shale, dolomitic, bluish-gray, weak; dolomite, argillaceous, bluish-gray and brown, very finely to coarsely crystalline ...... 12 Dolomite, light brown, finely to coarsely crystalline; dolomite, speckled light and dark gray, medium to coarsely crystalline; shale, dolomitic, bluish-gray, at base . . ... 18 Dolomite, argillaceous, v ery finely and very coarsely crystalline; shale, bluish-gray, weak 5 Shale, dolomitic, gray, weak ; dolomite, argillaceous, gray, very finely crystalline . 30 Same, but with little dolomite ...... 30 Shale, dolomitic, brown, firm, grading to dolomite, argillaceous, very finely crystalline . 20 Shale, as above; few layers of dolomite, argillaceous, brown and gray, very finely to medium crystalline ...... 40 Shale, slightly dolomitic, dark brown, tough; few pyritized gastropods ...... 5 Total 180 W ELL No. 2-L. E. GRAY, MIDLAND ELECTRIC CoAL CoMPANY No. 2 SEC. 36, T . 17 N., R. 4 E., HENRY COUNTY Description Thickness feet Shale, silty, gray to green, fossiliferous ...... 9 Shale, silty, gray tinged with green, firm . 58 Shale, dolomitic, bluish-gray, hard ; dolomite, gray to brown ...... 15 Shale, light gray and green; dolomite, light to dark gray .. . 40 Shale, silty, brown to dark brown, firm ...... 71 Total 193 12 MAQUOKETA AND "TRENTON" FORMATIONS WELL No. 3-SEWELL WELL DRILLING Co., CoNTINENTAL CoNSTRUCTION COMPA NY No. 2 SEC. 8, T. 16 N., R. 3 E., HENRY COUNTY Description Thickness feet Sandstone, calcareous, silty, gray, very finely grained, coherent . 10 Shale, slightly calcareous, silty, light gray, weak ...... 15 Dolomite, mottled light and dark gray, fossiliferous ...... 15 Shale, slightly calcareous and silty, greenish-gray, weak ...... 30 Dolomite, gray, buff, finely to medium crystalline, fossiliferous .. 60 Dolomite, brownish-gray to brown, very finely crystalline ...... 70 Total 200 WELL No. 4--E. STEVENSON,]. H. BUCKLEY No. 1 SEC. 21, T. 19 N., R. 10 E., LEE COUNTY Thickness Description feet Dolomite, argillaceous, brown and brownish-gray, fossiliferous; shale, dolomitic, green . 15 Dolomite, as above; shale, dolomitic, brown ...... 10 Shale, dolomitic, green; dolomite, light brown, coarsely crystalline . 10 Dolomite, brown, medium crystalline, fossiliferous; shale, dolomitic green . 5 Dolomite, argillaceous, brown, medium crystalline; shale, dolomitic, brown .... . 10 Shale, dolomitic, brownish-gray; dolomite, light brown, coarsely crystalline ...... 5 Dolomite, argillaceous, brown, finely crystalline; shale, dolomitic, brown ... . 15 Dolomite, light brown, finely to coarsely crystalline, fossiliferous ...... 30 Dolomite, white and brownish gray, coarsely crystalline, fossiliferous ...... 15 Same, and shale, dolomitic, brown, fossiliferous ...... 25 Shale, dolomitic, brownish-gray, fossiliferous; dolomite, brown. 15 Total 155 WELL No. 5-GRAYs LAKE VILLAGE SEC. 26, T. 45 N., R. 10 E., LAKE COUNTY Description Thickness feet Shale, green, gray, brown; dolomite, argillaceous, buff, yellow, green .. 10 Dolomite, white with greenish and buif tinge, medium crystalline . 30 Dolomite, mottled white and black, medium to coarsely crystalline .... 10 Shale, greenish-gray, weak ...... 40 Shale, gray, weak ...... 30 Dolomite, mottled, white and gray, medium to coarsely crystalline ...... 20 Shale, brown, and gray near the base, weak ...... 60 Total 200 WELL No. 6-ARNOLD AND MIDDLETON, HoDGEs No.1 SEC. 35, T . 15 s., R. 2 w., ALEXANDER COUNTY Description Thickness feet Siltstone, calcareous, dark gray, compact ...... 30 Siltstone, calcareous, argillaceous, dark brown, friable ...... 10 Shale, very silty, dark brown, micaceous ...... 40 Siltstone, argillaceous, dark brown, micaceous; shale, silty, brown ...... 10 Sandstone, argillaceous, brown, fine-grained; some shale, brown . 30 Siltstone, argillaceous, shaly, dark brown, micaceous ...... 30 Shale, silty, calcareous, dark brown, tough; few limestone streaks ...... 30 Shale, as above; limestone, light to dark brownish-gray, partly argillaceous, with phos- phatic nodules ...... Total 185 SUBSURFACE RELATIONS . 13 WELL No. 7-STA OLIND OIL Co., LEINER No.1 SEC. 20, T. 7 S., R. 4 W., JACKSON COUNTY Thickness Description feet Sandstone, calcareous, grayish-green, very fine-grained ...... 16 Siltstone, sandy, calcareous, grayish-green; little shale, gray ...... 17 Shale, sandy, silty, grayish-green; some siltstone, as above...... 25 Shale, grayish-green, firm ...... 40 Sandstone, very silty, argillaceous, brown, very finely grained ...... 18 Shale, silty, dark brown, firm ...... 4 Sandstone, very silty, argillaceous, brown, very finely grained ...... 10 Shale, gray, smooth...... 4 Sandstone, very silty, argillaceous, brown, very finely grained ...... 19 Shale, gray, smooth; very few interbedded limestone lenses . 25 Limestone, very argillaceous, silty, dark gray, very finely crystalline ...... 15 Limestone, argillaceous, mottled white to black, finely to coarsely crystalline 5 Total 198 WELL No. 8-PURE OIL Co., STELLA BILLINGTON No.3 SEC. 27, T. 1 N., R. 7 E., WAYNE COUNTY Thickness Description feet Sandstone, brownish-gray, fine ...... 5 Siltstone, gray, green, buff ...... 30 Shale, silty, dolomitic, brown, firm; limestone, very silty, brownish-gray, fine . 30 Shale, dolomitic, green, firm ...... 20 Shale, calcareous, dark grayish-brown, firm ...... 60 Same, but very calcareous and with phosphatic nodules 25 Same, with few layers of limestone, brown, finely crystalline ...... 35 Total 205 . WELL No. 9-0Hio OIL CoMPA Y, MmoAUGH No. 23 SEC. 32, T. 4 N., R. 12 w., LAWRENCE COUNTY Thickness Description feet Siltstone, slightly calcareous, dark gray, micaceous ...... 15 Shale, slightly calcareous, dark greenish gray, tough ...... 20 Shale, slightly calcareous, dark gray to brown, tough ...... 75 Shale, silty, slightly calcareous, brown and gray ...... 30 Shale, calcareous, brown; limestone, brown, very coarsely crystalline. 10 Shale, calcareous, brown; limestone, argillaceous, gray, very finely crystalline . 10 Shale, calcareous, brown, tough ...... 125 Shale, calcareous, brown; limestone, argillaceous, dark brown ... . 10 Total 295 Of questionable age is a red "hematitic" to the Edgewood formation on the basis of frequently plastic and sometimes micaceous their stratigraphic relations. The beds in shale, usually containing limonitic pellets Kane County and adjacent areas occur as or oolites, which lies above typical Maquo a mantle over strata of known Maquoketa keta shales and dolomites in portions of age which vary considerably in thickness. Lake, McHenry, Kane, and DuPage coun The beds are always overlain by Silurian ties, and in Kankakee County in north rocks. The red beds in Hancock County eastern Illinois, and in Hancock County and differ slightly in texture but always exhibit possibly Monroe County in western Illinois. similar stratigraphic relations, that is, they Whether or not these several occurrences lie above the Maquoketa formation (or are of the same age is not known. The above the Galena formation where the exposures in Kankakee County have failed 8 Maquoketa has been removed), and below to yield any fossils but have been referred the Silurian system (or below the Devonian 8Athy, L. F ., Geology and mineral resources of the system where the Silurian is not present). Herscher quadrangle : Illinois Geol. Survey Bull. 55, pp. 33-3 8, 1928. Beds of related lithology occur between the 14 MAQUOKETA AND "TRENTON" FORMATIONS Silurian system and the Maquoketa forma than that of the Silurian beds above or that tion in Wisconsin/ Iowa,8 and Nebraska.9 of the Galena below. A relatively higher The character of the red shale suggests that potential is present opposite the middle it is a residual, probably lateritic, deposit limestone zone in areas where it is devel formed from Maquoketa shale and lime oped. The resistivity is generally low, as it stone or dolomite. To what degree the is for most shales, but is lowest in the upper deposit has remained primary and is thus shale unit. The higher resistivity of the Maquoketa in age, or has been reworked lower part of the formation is probably a and incorporated into basal Silurian and function of the greater carbonate content. Devonian sediments is not known. The middle portion usually has a relatively There is, in addition to the subdivisions high resistivity, as might be expected from treated above, the so-called "depauperate its lithologic character. However, a rela zone" at the very base of the Maquoketa tively high resistivity is also frequently en formation. It consists of a more or less countered in the middle portion when gross conglomeratic phosphatic and slightly cal sample examination shows no marked in careous gray-to-black shale containing fos crease m carbonate material. sils of a characteristic fauna composed of at least 44 species of invertebrates, few of THICKNESS which exceed a quarter of an inch in diame The thickness of the Maquoketa forma ter. This zone is present wherever the base tion is variable and exhibits no consistent of the formation is exposed in Iowa, 10 11 trends except that it is thickest in the south Missouri, Illinois, and Wisconsin. ' Near eastern portion of the State. As indicated by the quarry of the Columbia Quarry Co. at the Maquoketa isopach map (fig. 1 ) , the Valmeyer, Illinois, the depauperate fauna is said12 to be at the base of the shale above thickness most commonly reported is about the Fernvale limestone. Frequently the 200 feet. Many variations occur along the zone can be recognized in sample cuttings. western and northern margins of the state. Some wells have been studied in which two Although it is possible that some of these or even more zones having similar lithology variations are the consequence of, or reflect, are encountered in the lower portion of the structural disturbances, the great majority Maquoketa formation. Although the gross are believed to result from post-Maquoketa, lithology of these zones is suggestive, it is pre-Silurian erosion which developed a not known whether they contain the same pattern of drainage with broad shallow fauna as does the "depauperate zone" of valleys and broad poorly drained uplands. the outcrops. STRATIGRAPHIC RE LATIONS ELECTRIC LOGGING CHARACTER The Maquoketa formation is separated The Maquoketa is the most distinct of from the overlying Silurian system by an the several formations considered, so far erosional unconformity wherever the con as electric logging character is concerned. tact is exposed. The widespread nature of Its potential is generally markedly lower this unconformity is further apparent from the isopach map of the Maquoketa forma 7Uirich, E. 0., otes on new names in table of forma tions and on physical evidence of breaks between P aleozoic tion which shows what is interpreted as the systems in Wisconsin : Trans. Wisconsin Acad. Sci. val. 21, pp. 71-107, 1924 . irregular eroded upper surface of the forma ~ Ladd , H . S., Strati graphy and paleontology of the M aquoketa shale in I owa: Iowa Geol. Survey, Ann. Rept., tion, from the considerable variations in p . 56, 1928. thickness, and from the fact that Silurian 9Lee, W., The stratigraphy and structural development of the Forest City basin in K ansas: State Geol. Survey strata rest upon different zones in the of Kansas, Bull. 51 , p. 42, 1943. 10Ladd, H. S., op. cit., pp. 371-384. Maquoketa within relatively limited areas. UWeller, Stuart, and St. Clair, Stuart. Geolcgy of Ste. Genevieve County, Missouri : Mis ouri Bur. Geol. and A well-marked erosional unconformity Mines, val. 22, 2nd [eries, p. 124, 1928 . 12Guidebook, Thirteenth Annual Field C:mference, separates the Maquoketa · from the under Kansas Geol. Soc. p. 24, 1939. lying Galena formation wherever their con- SUBSURFACE RELATIONS 15 tact is exposed in Illinois. This is corrobo and chocolate shales with interbedded rated by the relations between the two coarsely crystalline limestone occurring ·in formations shown on the cross-sections Williamson County, Tennessee. The fol (plates 1 and 2) and by the isopach map lowing year Ulrich17 stated that the thin of the Galena (fig. 5) . bed of limestone at the top of the Kimms wick formation in southeastern Missouri CoRRELATiON contained a Fernvale fauna. The presence of the Fernvale in Missouri and adjacent The correlation of the Maquoketa forma parts of Illinois was thus presumably tion with the Richmond group and Cin established by Ulrich and later workerS18 cinnatian series of Indiana and Ohio has 13 entirely on faunal grounds. Subsequently, long been recognized. Laddu suggested 10 from his extensive faunal studies of the Savage applied the term without reser vation to the middle limestone of the Ma Maquoketa that the Brainard shale, the 20 top member of the formation, in Iowa, is quoketa in northern Illinois. Ladd pointed correlative with the Elkhorn, uppermost out later that the "depauperate zone" was formation of the Ohio Valley Richmond, probably equivalent to a similar faunal zone and that the "depauperate zone" may be near the top of the Arnheim formation and correlative with the top of the Arnheim that the Arnheim in Tennessee is overlapped formation of the Ohio Valley section. by the Fernvale. This suggestion casts Savage13 believed that the middle limestone considerable doubt on previous beliefs that unit in northern Illinois is equivalent to the the Fernvale of southwestern Illinois is Waynesville formation of the Ohio Valley stratigraphically equivalent to the Fernvale succession. The present study has not of Tennessee, inasmuch as the former lies provided any new evidence pertaining to below the "depauperate zone" and other these regional correlations. zones of similar lithology. The middle lime However, a tentative correlation (fig. 2) stone unit of northern and central Illinois between the Illinois and Iowa sections based lies above the brown shale with its basal upon lithology and stratigraphic position, is "depauperate" fauna and other zones of made on the basis of this study. The upper similar lithology. The lowest known occur green shale zone is correlated with the rence of the "depauperate zone" in south Brainard shale of Iowa, the middle lime western Illinois is above the Fernvale lime stone zone with the Fort Atkinson lime stone. This apparently precludes the pos stone, a thin green shale occasionally de sibility of the two limestone horizons being veloped below the middle limestone with identical. This statement is further cor the Clermont, and the lower brown shale roborated by inspection of electric logs of unit with the Elgin shaly limestones. Appli wells in St. Clair, Madison, and Monroe cation of the Iowa member names in Illinois counties. These logs show the typical three is believed inadvisable because of the con fold division in the north and east, grading siderable local and regional variation in the within a short distance south and west .into development of the several units. the two-fold division, and still farther, into Several problems must be considered in a section composed dominantly of shale with any discussion of Maquoketa correlation. As noted above, the Fernvale has been interbedded siltstones. It appears, moreover, included with the Maquoketa in this dis that the two zones are not characterized by cussion. The term Fernvale was first applied similar electric log character : · the middle by Hayes an3 Ulrich10 in 1903 to soft green carbonate zone generally has its highest resistivity at or near the top and decreases 13Meek, F. B. , and Worthen, A. H., Descriptions of new crinoidea from the Paleozoic rocks of Illinois and 17 :.orne adjoining rtates: Proc. Acad. N at. Sci., p. 155, 1865. In Buckley, E . R ., and Buehler, H. A. , Ou ar rymg 14Ladd, op. ci• .. pp. 36-70. industry of Missouri ; Mis>ouri Bur. Geol. and \fines, vol. 2, 2nd series, p. Ill , 1904. 15Savage, T . E., Correlation of the Maquoketa and Richmond rocks of I ow a and Illinois: Trans. Ill. Acad. 18Weller and St. Clair, op. cit., p. 119. Sci .. vol. 17 , pp. 233-47, 1924. 11Savage, 1924, Joe. cit. 16Hayes, C. W., and Ulrich, E. 0 ., op. cit. 20Ladd, op. cit., 368-70. 16 MAQUOKETA AND "TRENTON" FORMATIONS in resistiVIty with an increase in depth, The Divine limestone is roughly equiva whereas in the lower zone, the resistivity, lent to the "middle limestone zone" of this and hence the carbonate amount, is lowest report. The writer has preferred the latter at the top and increases with depth. designation because it lacks the implication From these several facts, it is apparent of a definite upper and lower boundary that if the fauna of the so-called Fernvale which is imposed by the geographic name. of northern and central Illinois is so similar to that of the Fernvale of southwestern CRITERIA FOR R ECOGNITIO T Illinois as to have suggested correlation, The top of the Maquoketa formation is although physical continuity is now known recognized in well cuttings at the first ap to be impossible, then the original extension pearance of siltstone or very fine-grained of the formation from Tennessee to Mis sandstone below the basal and frequently souri is unwarranted. It appears rather that oolitic zone of the Silurian system through the Fernvale fauna is a recurrent one that out most of central and southern Illinois, is related to any relatively pure coarsely and at the first appearance of any significant crystalline limestone facies in the Maquo body of green or gray shale throughout the keta formation. It is therefore suggested rest of the State. Locally green shale forms that the term "Fernvale" be dropped from the uppermost portion in the central and usage in Illinois, and that its propriety in so uthern portions of the State and siltstone the rest of the Upper Mississippi Valley in the northern. The base of the Maquoketa and Mid-continent regions be more closely formation is always marked by an abrupt investigated. change from calcareous shale or argillaceous The Thebes sandstone consists in south limestone or dolomite to the pure, though western Illinois and southeastern Missouri sometimes shaly, white, buff, or brown of finely to very finely grained compact Galena limestone or dolomite. The lower sandstones which are bluish-gray or brown carbonate lenses in the Maquoketa forma in fresh exposures. The wide vertical and tion are generally finely-granular and thus horizontal distribution of this type of sand differ from the more coarsely crystalline stone and siltstone in the Maquoketa £orma underlying beds. The so-called Fernvale tion of Illinois and the fact that it occurs limestone, although coarse in texture, is interbedded with shale indicate that it is usually distinguished from the Galena by a lithologic facies which may occur in any its mottled white and brown or gray color. part of the Maquoketa and i especially common near the top of the formation. In In electric logs, the upper contact of the many sets of cuttings two or more horizons Maquoketa may be recognized by the sharp of Thebes-like lithology are noted (records decrease in resistivity below the Silurian, of Pure Oil Co. Stella Billington No. 3 and similarly the lower contact may be and Stanolind Oil Co. Leiner No. 1, wells recognized by a sharp increase at the top of 7 and -s, p. 13). It thus appears that the the Galena strata. Some electric logs show Tli.eoes sandstone is not a formation but steadily increasing resistivity in the basal only a lentil that is locally developed near zone of the Maquoketa, but this is usually the base of the Maquoketa formation, and less than 100 ohms, whereas the Galena the use of the name should be restricted curve is invariably more than 100 ohms accordingly. and sometimes more than 500 ohms. SUBSURFACE RELATIONS 17 22 GALENA2' (KIMMSWICK ) crops out in north-central and northwestern Illinois it consists largely of brown porous FORMATION massive finely to medium crystalline dolo Subsurface geologic studies are bringing mite.24 Locally thin partings or beds of shale to light a rapidly increasing amount of in are present. Three members are recognized formation, heretofore unavailable, on the in this region and in adjacent portions of geographic distribution and stratigraphic Iowa, Minnesota, and Wisconsin: Dubuque relationships of formations that have long at the top, Stewartville in the middle, and been known and studied at their outcrops. Prosser at the bottom. The Dubuque mem It is now clear that certain strata that crop ber may be differentiated by its faunal con out in different areas and are known by tent and by its thinly bedded shaly charac different names are parts of a formation of ter. The Stewartville member is generally great extent and more or less uniform chert-free, in contrast to the underlying lithology (fig. 4). The writer feels that member, and is distinguished by its faunal eventually many local stratigraphic names assemblage. The Prosser member is divisible will be abandoned and that such a wide into an upper noncherty zone, a middle spread formation will come to be known cherty horizon, and a lower noncherty zone. by a single name throughout its entire ex This division, however, is arbitrary and tent. Thus stratigraphic nomenclature will tends to vary from one locality to another. be greatly simplified. Several of the forma Because the lithological boundaries of the tions considered in the present report are members are so indistinct in well cuttings, of this type and in their subsurface develop little attempt has been made to differentiate ment throughout Illinois are referred to by them in common practice. In well cuttings the oldest name in good tanding applicable from northern Illinois, the Galena consists to each in this region. Strata continuous of finely to medium crystalline dolomite, or with the Galena dolomite and Kimmswick rarely limestone, usually more or less vesic limestone are designated Galena, and beds ular, and ranging from gray to buff or representing the Plattin and Platteville brown in color. Locally the upper 40 to 80 limestones are designated Plattin. In order feet of the formation differs slightly in tex to avoid confusion concerning the strata in ture or color, and may contain thin partings and near the outcrop areas where they are or beds of brown dolomitic shale. This hori known by other name , the local name is zon probably corresponds to the Dubuque added in parenthesis, as Galena ( Kimms member. Samples from the lower portion of wick) limestone in southern Illinois and the formation are frequently characterized Plattin ( Platteville) limestone in northern by a light gray or white porcellaneous chert Illinois. which apparently comes from a zone which is stratigraphically equivalent to the cherty LITHOLOGY zone in the Prosser. In southern Illinois the Galena formation Rocks of Galena age occur throughout is represented by the Kimmswick limestone. the State with the exception of parts of In outcrop it is "essentially a gray, some north-central Illinois23 and a few isolated times tinted blue or pink, coarsely granular areas along the western border where ero limestone."25 sion has cut down to the level of the Plattin or lower beds. Where the formation Locally, especially in Pike and Lincoln counties, Missouri, the upper portion of the 21 So named because this formation is the principal lead bearing zone in the Upper Mississippi Valley. It is well Galena is finely granular and thinly bedded. developed in the vicinity of Galena, Illinois, Dubuque Iowa, and Mineral Point, Wisconsin. In Fo ter, ]. w.: 23Willman, H. B., and Payne, ]. Norman, Geology and and Whitney, ]. D., Report on the geology of the Lake mineral resou rces of the l\tlarseilles, Ottawa, and Streator Su~erior land district: pt. 2, pp. 146-148, 185 I. quadrangles: Illinois Geol. Survey Bull. 66, p. 65, 1942 . T h1s name was proposed to apply "to the more or le ~s 24 Willman, H. B., High purity dolomite in Illinois: crystalline limestone bei~ g qua_rried at Graysboro, Cape Illinois Geol. Survey Rept. lnv. 90, pp. 78-79 , 1943. G1rardeau, Glen Park, K1mmsw1ck, and other localities in 25Krey, Frank, Structural reconnaissance of the Missis southeastern Missouri" by Ulrich in Buckley and Buehler sippi Valley area from Old Monroe, Missouri, to auvoo op. cit., p. Ill. ' Illinois: Illinois Geol. Survey Bull. 45 , p. 21, 1924. ' 18 MAQUOKETA AND "TR ENTONn FOR MATIONS NORTHERN ILLINOIS SOUTHERN ILLINOIS AND EASTERN MISSOUR I MAQUOKETA MAQUOKETA Stewartvi lie Prosser u I on w 0 Guttenberg : w _, Spechts Ferry "DECORAH" - > Magno I ia w 1-- 1-- Mifflin JOACHIM DUTCHTOWN ST. PETER EVERTON Frc. 4.-Correlation chart of the Middle and Upper Ordovician strata in Illinois and eastern Missouri. SUBSURFACE RELATIONS 19 This horizon has been called the McCune of which the upper noncherty zone is about limestone26 and is said to carry a Stewart 30 feet, the middle cherty zone is from 80 ville fauna.27 As observed in well cuttings to 100 feet, and the lower massive non from central and southern Illinois, the c;lerty zone is from 20 to 50 feet. Else Galena is a medium to coarsely crystalline where the Galena formation ranges from buff, brown, or white, occasionally tinged 100 to 125 feet in thickness, of which the with pink, limestone. Chert is present in lower 40 to 50 feet may be more fossil some wells but is seldom abundant. The iferous or possess a lower resistivity than uppermost few feet of beds are occasionally f12 upper. slightly shaly. Over much of the area the· formation is divisible into an upper rela STRATIGRAPHIC RELATIONS tively nonfossiliferous zone, and a lower zone which contains many- bryozoa and The Galena formation underlies the ostracods and which is so fossiliferous that Maquoketa formation ·with slight local it approaches a coquina at some places. disconformity but with broad regional un conformity. This is known from numerous ELECTRIC LoGGING CHARACTER exposures of the contact between the two formatio-ns and is further indicated by the The electrical resistivity of the Galena reduction in thickness of the Galena forma formation is high. The largest values are tions toward the St. Louis and Ozark areas. usually noted in a zone the upper limit of Apparently both Stewartville and Dubuque which is 10 or 15 feet below the contact strata have been completely removed from with the Maquoketa formation, with gradu ally decreasing values in the lower beds. most of central and southern Illinois and As seen in the north-south cross-section southeastern Missouri. The McCune lime (pl. 1) this difference in resistivity between stone of Missouri is faunally equivalent to the upper and lower beds becomes more the Stewartville and apparently represents apparent in a southerly direction and may an isolated remnant of the beds which once be related to an increase in clay content in covered the territory. that direction. Potential values of the The Galena formation is conformable Galena are generally high and appear to with the Decorah formation in northern be more consistent than are those of the Illinois and more or less disconformable 2 lower formations. elsewhere. a In much of central and southern Data now available suggest that the Illinois it is possible that the Galena members of the Galena formation in north (Kimmswick) rests disconformably upon eastern Illinois may be separated on the the Plattin. basis of their electric logging characteristics. CORRELATION THICKNESS The Galena dolomite and Kimmswick As shown on the isopach map (fig. 5), limestone are continuous in subsurface. the maximum thickness of the Galena Bradley30 states that "the fauna of the formation is about 250 feet in northwestern typical Kimmswick limestone is more simi Illinois. The formation in southern and lar to the fauna of the lower 9 feet of the central Illinois thins toward the St. Louis 26Named for expos ures of limestone near M cCune Station , area where a minimum thickness of about Missou ri , by K eyes, C. R ., Proc. I owa Acad. Sci., vol. 5. 90 feet is encountered. p . 6 1, 1898. 27Carl A. Bays, personal communica tion . The thickness of the members of the 2' Willman, H. B., op. cit., p. SO. Galena formation in northern Illinois , 2 ~ are 23K ay, G . NL, and Atwater. G . I., Basal rel ations of the Galen a dolomite in the Upper Mississ ippi Valley ; Am . as follows: Dubuque member about 30 J our. Sci., 5th Ser., vol. 29, pp. 98-lll , !93 5. feet; Stewartville member about 40 feet; 30Bradl ey, J oh n H.. Strat ig raph y of the Kimmswi ck li mestone of Missou ri and Illinois: J our. Geology, vol. and Prosser member about 150 to 175 feet 33, p. 65, 1925. 20 MAQUOKETA AND "TRENTON" FORMATIONS ISOPACH MAP OF THE GALENA FORMATION BY E. P. DuBOIS JANUARY I, 1945 I I _ ~"'-·---~ I ' ,·---·-·j , _ __j . _ i I . .. !------1 -- ---j DATUM POINT ..... ··· BOUNDARY BETWEEN GALENA AND OVERLYING FORMATIONS THICKNESS OF GALENA FORMA.TION AREA IN WHIC H GALENA- PLATT IN (PLATTEVILLE) FORMATIONS CROP OUT OR ARE COVERED ONLY BY GLACIAL DRIFT OR PENNSYLVANIAN STRATA; THICKNESS VARIABLE SCALE 10 20 30 40 50 MILE~ FIG. 5 SUBSURFACE RELATIONS 21 Prosser at St. Paul, Minnesota, designated DECORAH32 FORMATION as the Clitambonites bed by Winchell and The Decorah formation as first desig Ulrich, than that of the overlying Fusispira nated consisted of 25 to 30 feet of green bed. It seems likely .. . that with the ex calcareous shale, with numerous bands and ception of the McCune zone of northeastern nodules of limestone, exposed in the city Missouri, the Kimmswick limestone in its of Decorah. The term has since been ex type exposure does not rise above the tended in practice until it has at one time 31 Fusispira zone." Kay recognized a lower or another included any shaly horizon Trenton fauna in the basal Kimmswick and directly beneath the Galena. As commonly suggested that the base of the Kimmswick recognized in the past in the Upper Missis may be Ion in age. Thus it appears that sippi Valley, it has included three members: wherever the Kimmswick limestone is the Ion, Guttenberg, and Spechts Ferry. recognized in Illinois it represents the The Spechts Ferry member was excluded 3 Galena formation in such regions and, so from the formation in 193Y and the De far as is known, is correlative with the corah thus limited to strata of Trenton age. Prosser member of the typical Galena The beds in southeastern Missouri and formation and with perhaps some part or all southern Illinois which have been referred to the Decorah formation are, so far as is of the Ion member of the Decorah forma known, faunally equivalent to the Spechts tion of Iowa, Wisconsin and northwestern 34 Ferry member, now assigned to the Plattin Illinors (fig. 4). (Platteville) formation. However, as a matter of convenience, in subsurface work CRITERIA FOR R ECOGNITION the Spechts Ferry member is included m the Decorah formation wherever it IS The Galena formation may be dis recognized, and it is also so considered in tinguished in well cuttings by the occur this report except as otherwise indicated. rence of medium to coarsely, occasionally finely, crystalline non-argillaceous limestone LITHOLOGY or dolomite. With the exception of shaly partings and occasional cavern fillings, no With the exception of limited areas in significant body of shale occurs in the north-central and northwestern Illinois, and Galena formation throughout most of in scattered wells elsewhere, beds of De Illinois. corah lithology are present throughout the In electric logs, the top of the Galena State. The strata are often lithologically similar to the underlying Plattin formation, formation is marked by an abrupt increase and the basal contact can seldom be deter in resistivity, which should not be confused mined with certainty. with the much more gradual ·increase in resistivity with depth which in some lo In outcrops in north-central Illinois, the calities is characteristic of the lower portion Decorah (restricted) consists of "brown, gray, buff and purplish cherty, usually ar of the Maquoketa formation. gillaceous dolomite or limestone with thin 31 Kay, G. Marshall, Stratigraphy of the Decorah forma partings of gray, brown, and purplish brittle tion: j ou r. Geology, val. 37, 1929. 32 amed for the city of Decorah, Iowa, where the fossiliferous calcareous shale ... Distinctive formation is exposed. Calvin, Samuel, Geology of Winne features ... are the presence of 1) black, shiek County: Iowa Geol. Survey, val. 16, p. 61, 1907. 33Kay, G. Marshall, Ordovician strata in the Upper gray, dark brown specks and flakes in the Miss issippi Valley: Rept. 9th Annual Field Conference of the Kansas Geol. Soc . p. 289, 1935. Bays, C. A .• and G. limestone or dolomite, giving it a peculiar 0. Raasch. M ohawkian relations in Wisconsin: Rept. 9th Annual Field Conference of the K ansas Geol. Soc., p. 299, speckled appearance, 2) scolecodonts or 1935. conodonts ... , 3) shaly surfaces and pits in 34Kay, G. M arshall, Stratigraphy of the Decorah forma tion : op. cit. C:trl Bays, Person~! communication. the cuttings, and 4) speckled, partly sandy, 35Willman, H. B., and Payne, ]. Norman, Geology and gray, brown, and white translucent chert."35 mineral resou rces of the Marsei lles, Ottawa, and Streator quadrangles: Illinois Geol. Survey Bull. 66, p. 65, 1942. In extreme southern Illinois, the formation 22 MAQUOKETA AND "TRENTON" FORMATIONS (probably mostly Spechts Ferry in age) A similar occurrence of metabentonite ( ?) consists of "thin beds of dense fine-grained is present in the nearby Nelson, Erp, and limestone separated by greenish calcareous Stroh, Erp well No. 1, sec. 19, T. 24, N., shale, with as much as 10 feet of very hard R. 7 E., ford County, where it is associated siliceous limestone locally present at the with brown to buff very finely crystalline top."36 The three members of the formation slightly dolomitic limestone, brown cal in northwestern Illinois, especially the Ion careous dolomite, and brown shale. and Guttenberg, exhibit marked changes In the Arnold and Middleton, Hodges in facies from calcareous shales in the north well No. 1, sec. 35, T. 15 S., R. 2 W., western exposures to limestones or dolomites Alexander County, the upper 10 feet of the in the southeast. Decorah formation consists of brown very In well cuttings, the beds assigned to the finely crys talline argillaceous sandy lime Decorah usually consist of interbedded stone containing brachiopods and corals, and limestones, dolomites, and shales lying be white flaky translucent clay, apparently metabentonite ( ?) . neath the Galena formation. A diamond drill core from the Schwarz-Schlafly well, sec. 3, T. 2 N., R. 3 W., Clinton County, ELECTRIC LOGGING CHARACTERISTICS has 21 feet of rock which is believed to be Because of the considerable variation in Decorah. This includes about 10 feet of lithology of the Decorah, no consistent greenish-gray to green lithographic, partly electrical properties can be noted. Its out argillaceous limestone with a few shale standing feature is the presence of low partings and streaks of dolomite at the top, resistivity associated with the shales and ar 3 feet of buff sublithographic to finely crys gillaceous limestones and dolomites. Low talline dolomite near the middle, about 7 potentials are also commonly recorded at feet of similar rock with interbedded streaks this horizon. The sharp decrease in resis of buff medium to coarsely crystalline dolo tivity and potential is of aid in delimiting mitic limestone with some shale partings the top of the Decorah, but with few ex below, and 1 foot of buff coarsely crystalline ceptions, it is impossible to determine the sandy and cherty dolomite at the base. base of the formation. Metabentonite(?) occurs in the Decorah formation in Illinois, apparently at random, THICKNESS as for instance in the Barber and Sievers, There is a considerable variation in the Lindsey well No. 1, sec. 20, T. 20 N., R. 8 thickness of the strata assigned to the De E., Champaign County, in which it is corah formation in subsurface. Locally it present not only in the cuttings but is also is not possible to recognize any beds that represented on the electric log (pl. 1, well might be assigned to the formation, where 5). In this well, the Decorah formation as in other areas as much as 70 feet may be consists, from top down, of: ( 1 ) 2 feet of present. Thicknesses ranging from 20 to 50 greenish-gray pyritic metabentonite(?) ;(2) 31 feet are reported in north-central Illinois 13 feet of gray to buff finely to medium and elsewhere, but the average for most of crystalline limestone, some of which has a central and southern Illinois appears to be red speckled appearance similar to that ob 35 to 40 feet. served in the Decorah elsewhere; ( 3) 1 foot of reddish-brown calcareous shale; ( 4) 5 feet of brown to gray more or less ar- . STRATIGRAPHIC R ELATIONS gillaceous slightly cherty limestone, and; There is no well marked unconformity ( 5) 1 foot of gray sandy metabentonite ( ? ) . either above or below the Decorah formation 38 36Weller, J. Marvin, Geology and oil possibilities of in northern Illinois. In outcrops in south extreme ~outhern Illinois: Illinois Geol. Survey R ept. Inv. 71 , p. 18, 1940 . eastern Missouri, where the formation is 37 W;llman a11d Payne, op. cit. better exposed than in adjacent parts of 3"Kay, G. M arshall, Stratigraphy of the Decorah forma tion: op. cit. p. 656. Willman and Payne, op. cit. Illinois, the Decorah ( Spechts Ferry) is SUBSURFACE RELATIONS 23 41 2 separated from the overlying Galena by a PLATTIN (PLATTEVILLE. ) well marked unconformity, but appears to 3 FORMATION be gradational into the underlyin;;; Plattin. ) Such data as are available from well cut vVith the exception of part of north tings and electric logs indicate by the varia central Illinois and part of Calhoun tion in those beds which underlie the Galer.a County, where the St. Peter sandstone and formation that this same situation prevails elder strata are exposed at the surface, Plattin strata are present throughout the in much of the central and southern portions state. of the state. Red bituminous shales which occur in the Decorah along the western The Plattin formation in northern border of the state, and which crop out in Illinois, where it has generally been called Platteville, is divided into four members,' 3 C alhoun County, bear a strong lithologic namely from top down, Spechts Ferry,.. resemblance to the "oil rock" of the Gutten 45 Magnolia, Mifflin, and Pecatonica. berg member of the Decorah. Such faunal evidence as is available suggests a Spechts LITHOLOGY Ferry age for these shales. As yet it does not appear that a definite age can be as The Plattin (Platteville) of northern signed to these beds. Illinois consists largely of brown, buff, or gray more or less argillaceous dolomite and CRITERIA FOR RE COGNIT ION limestone, the dolomite being finely to medium crystalline and the limestone finely The Decorah formation is most surely crystalline to lithographic in texture. Al recognized in cuttings by the presence of though the members of the formation are metabentonite:o In addition, the Decorah usually distinguishable in outcrops and lo is frequently characterized by the presence cally in subsurface studies, they are usually of unusual amounts of shale and by red so similar lithologically and their lithol flecks and organic fragments. ogy, especially the degree of dolomitization, Electrically, the top of the zone is in most varies so much that their regional corre areas indicated by a marked decrease m lation depends not on lithology but on resistivity or potential or both. faunal content. Dolomitization is generally "related not stratigraphically to horizons 3JWeller and St. Clair, op . cit., p. 110. ' 0 A\though si mil:tr material is also occasionally noted within the formation but geographically to from the Galena and Plattin formati ons, it appears to be 0 rr.ost consistently a The limestones are usually more or less tively high- and low-resistivity zones about argillaceous and are brown, buff, gray or 130 feet below the base of the Galena rarely white in color. Gray is much less formation in wells Nos. S, 7, 8 and 9 in the prominent than the brown ar:d buff colors. north-south cross-section (pl. 1). The low In texture the rocks range from finely resistivity zone about 3SO feet below the crystalline to lithographic. Thin beds of Galena formation in well No. 9 is also buff or brown finely granular dolomite are present in wells Nos. 8, 7, and 6. Other commonly interbedded with the limestone zones may be similarly treated but with less and become more numerous in the lower assurance. S0-100 feet. Zones of brown, gray, or oc casionally green calcareous or dolomitic THICKNESS shales are locally present. Two such zones, one at and the other SO to 1 SO feet above The Plattin formation ranges from more the base of the formation, appear to be than 7 00 feet in thickness in Alexander regionally significant as they are present in County to less than 100 feet in thickness in most wells. Brown or black more or less portions of northern and western Illinois. silty, calcareous, or dolomitic clay occurs The decrease in thickness to the north and as partings between beds or possibly also as west is due principally to the fact that the stylolitic seams throughout but most fre Plattin sea transgressed in those directions. quently near the top and bottom of the The transgressive nature of all the strata formation. Chert is present but seldom in between the Gaiena and the St. Peter is large quantities. It is opaque and gray, shown in figure 6 and also in figure 7, al brown, or white in color. It appears to be though less clearly because it also includes of no regional stratigraphic significance. the Galena. "Oolitic" beds occur commonly throughout the formation but are usually only of local STRATIGRAPHIC RELATIONS stratigraphic significance, although one such bed, near the base of the formation, is The Plattin (Platteville) formation in apparently widespread in the south-central northern Illinois is overlain conformably by portion of the State.47 These "oolitic" beds the Decorah formation, and in central and appear to be intraformational conglomerates southern Illinois the contact is gradational. and range from angular fragments to nearly In northern and western Illinois the spherical pellets of limestone imbedded in Plattin (Platteville) formation overlaps a ground-mass of brown or buff sublitho upon the Glenwood-St. Peter sandstone so graphic or lithographic limestone. that strata of various ages lie directly on the sandstone at different places. Contact ELECTRIC LoGGING CHARACTERISTics of the Plattin with the Joachim is reported to be unconformable in Calhoun County, The Plattin formation is characterized Illinois,48 and in St. Genevieve County, by generally high resistivity. Although in Missouri.49 northern Illinois the formation may have thin zones of relatively low resistivity, its CoRRELATION resistivity is usually fairly constant (pl. 1, well No. 1). In southern and central The lowermost portion of the Plattin . Illinois, on the other hp.nd, the formation formation in southeastern Missouri, below has marked variations in resistivity. These an "oolitic" zone SO to 100 feet above its differences are tentatively ascribed to varia base, has been correlated by Ulrich and by tions in insoluble residue (clay) and dolo the Missouri Geological Survey50 with part mite content. They are significant locally of the Stones River group of Tennessee. and perhaps regionally as well. Such, for instance, is the contact between the rela- 48 Krcy, Frank, op. cit., p. 19. 4 JWeller and St. Clair, op. cit., p. 103. 50Kansas Geol. Soc. Guidebook, 1939, 13th Ann . Field HWel ler, J. Marvin, op . cit. p. 18. Con f., p. 64 and pp. I 05-9. SUBSURFACE RELATIONS 25 Although this correlation may be correct, JOACHIM61 FORMATION considerably more work based not only on LITHOLOGY fauna, but also on cross-sections and other stratigraphic evidence, needs to be done be The limits of the Joachim formation in fore the name should be applied in Illinois. Illinois have not yet been precisely defined. It is believed that some part, or all, of the It appears to underlie the Plattin in all of Plattin-Joachim-Dutchtown succession in southern and much of central Illinois, ex Illinois will eventually be found to be cor tending at least as far north as Coles relative with part or all of the Stones River County and perhaps as far as Champaign group, but as yet the relations are not clear. County. Along the western margin of the 2 Lithologically, there is little difference be State, it is reported 5 to be 7 5 feet thick in tween the beds in the base of the Plattin Calhoun County and is probably present and those in the rest of the formation, and some distance farther north. It is laterally such as there is, an apparent increase in clay continuous with the Joachim in Missouri and dolomite content, is to be considered and with beds in Kentucky and Indiana well within the range of variation of the which have not as yet been adequately formation. Caution should be exercised in studied. using "oolitic" zones as horizon markers ex Where the Joachim crops out in Missouri cept locally. Such intraformational conglom it is divisible into two parts separated by eratic facies may be present in any part 4 to 10 feet of fine-grained sandstone. The of the Plattin. upper part consists of dark gray or brown Inspection of the cross-section (pl. 1) dolomite with thin beds of shale or siltstone. indicates that the Plattin (Platteville) Near the top the dolomite often consists of formation in northern Illinois is probably thin laminae alternately dark gray and blue. equivalent to the upper part of the forma The lower part of the formation, apparently tion in southern Illinois, and that beds near widespread in southeastern Missouri, con the middle of the formation in southern sists of light gray finely granular very sandy, Illinois are contemporaneous with Glen often conglomeratic dolomite, commonly wood strata in the northern part of the interbedded with seams of shale.63 State. In Illinois, where the Joachim is known essentially only from its subsurface occur CRITERIA FOR RECOGNITION rence and where the wells which reach the Because the contact of the Plattin forma formation are widely spaced, no such divi tion with the overlying Decorah formation sion of the formation can be recognized at is -gradational, it is usually difficult or im present. The formation consists dominantly possible to identify it in well-cuttings or in of dolomite with occasional beds of lime- electric logs, and in general it is determined tone. The dolomite is characteristically buff as the horizon below which characteristics in color but may be browq or gray. Banding of the Decorah formation-metabentonite, is common and the alternating laminae des unusual amounts of shale, red flecks, and cribed from outcrops are often observed in organic fragments-are rare or absent. In cuttings. The typical texture is very finely central and southern Illinois this is general granular or crystalline and may best be ly the top of the brown lithographic lime described as "earthy." Thin beds of gray stone in which no shale, other than partings, or brown dolomitic shale are present and is present. occur most often in the lower parts of the In comparison with the underlying ' 1 Named for exposures along Joachi m Creek, Jeff erson Joachim formation the Plattin is more County, Missou ri. W inslow, A., Lead and zin c deposits of Missou ri : Missouri Geol. Survey vol. 6, 1st se r., p. 352, limestone than dolomite, darker in color, 1894. 52Krey. Frank, op. cit., p. 19. and more often lithographic, and contains 58McQueen, H. S., The Dutchtow n, a new Lower no gypsum or anhydrite or laminated dolo Ordovician formation in southeastern Miss ouri: Missouri Geol. Survey and \Vater Resources, Appendix I , 59th Bien. mite. Rept. pp. II, 12, 1937. 26 MAQUOKETA AND UTRENTON" FORMATIONS formation. Considerable gypsum or anhy clear. In the deep portions of the Illinois drite is interbedded with and grades into basin and south towards Alexander County the dolomites and shales. the two formations are clearly defined and easily differentiated on the evidence afforded ELECTRic LoGGING CHARACTER both by well cuttings and by electric logs. Correlations at the limits of the east-west The Joachim formation is easily recog cross-section (pl. 2), however, are dubious nized in electric logs throughout most of the when electric logs and sample-study records Illinois basin by the fact that it is strati are compared. The high-resistivity unit graphically the lowermost high-resistivity which represents the Joachim beds in the zone of the "Trenton." It is separated from north-south cross-section is well defined also the Plattin formation by a well defined low in the e·ast-west cross-section although it resistivity unit and from the Dutchtown thins somewhat to the west; similarly, the formation by the characteristic usually irregular low-resistivity unit which repre sharp break from high-resistivity to low sents the Dutchtown formation is equally resistivity values. Potential values are us well defined in both cross-sections. Litho ually higher than those of the beds immedi logically, however, the Dutchtown, which ately above or below but have little strati even where well developed may have fea graphic value because they lack consistency. tures characteristic of the Joachim, becomes more and more similar to the Joachim THICKNESS formation in a westerly direction, until in the Lockwood-Dyroff boring (pl. 2, well 1) The Joachim formation thickens from a there is no well-marked difference between feather-edge in the central part of the State the two formations and all beds above the to a maximum known thickness of about St. Peter and below the Plattin formation 100 feet in Alexander County. The average are of Joachim lithology. Similarly there is thickness throughout most of the Illinois uncertainty in the correlation of electric log basin is between 7 5 and 100 feet. In ad and sample study data to the east between jacent parts of southeastern Missouri the the Pure Oil Company's Billington well formation is reported to attain a maximum 54 and the Ohio Oil Company's Middaugh thickness of approximately 250 f~et. well (pl. 2, Nos. 7 and 8). Tentative correlation of these beds east STRATIGRAPHIC RELATIONS and west of the Illinois basin has been made on the basis of electric logs, mainly because In outcrops in Missouri the contact of the relations so expressed appear to be con the Plattin formation with the Joachim sistent. It should also be noted that Dutch formation appears to be unconformable. town-Joachim relations are not clear north Well cuttings in Illinois suggest that at of Coles County nor wuth of Alexander some places intergradation between the two County. Final analysis and interpretation formations takes place and that conformable must await additional study of both forma relations may exist. In the same general area tions. in Missouri, McQueen suggests "that an unconformity of considerable magnitude exists between the Joachim and the Dutch CRITERIA FOR RECOGNITION 55 town formations." However, as with the The Joachim may generally be recog upper boundary of the Joachim, this bound nized in well cuttings by several characters: ary also appears indefinite and probably it contains the first thick and consistent beds gradational in many sets of well cuttings. of dolomite below the Plattin limestone, its The relations of the Dutchtown and color is markedly lighter than most of the Joachim formations in Illinois are not yet Plattin, the texture is earthy or very finely granular such as occurs in no strata imme :> 56 Thin beds of dark brown, gray or green DUTCHTOWN FORMATION dolomitic shale, and sandstone are also present. Sandy dolomites are frequently LITHOLOGY present in the lower beds. The lithology of The areal distribution of the Dutchtown the questionable Dutchtown beds at the formation is less well known than that of margins of the east-west cross-section (pl. the Joachim formation. If the evidence 2) is very similar to that of the Joachim afforded by electric logs is reliable, the formation except that shale and sand beds Dutchtown is more or less coextensive with are more abundant than is characteristic of the Joachim. Here again, uncertainty exists the Joachim formation. These shales are in the marginal areas: shales of Dutchtown commonly dark brown and are suggestive lithology are known farther north (in of those observed in the more typical Dutch Douglas County) than are dolomites of town elsewhere. Joachim lithology; to the west, the Dutch town formation, as determined by electric ELECTRIC LOGGING CHARACTER logs, is somewhat thicker than the Joachim The Dutchtown formation has a charac and thus presumably more extensive. The teristically low and very irregular resistivity Dutchtown can be surely recognized only and a very irregular self-potential. On resis within the area included between Coles and tivity alone, it is very difficult to separate Alexander counties in a north-south direc the Dutchtown from the St. Peter sand tion and between Clinton and Wayne stone but potential values are usually higher counties in an east-west direction. and more consistent in the sand than in the In Missouri the Dutchtown formation overlying dolomites and shales. consists of limestone, dolomite, and dolo mitic sandstone, with considerable grada THICKNESS tion between these various lithologies. Minute particles of disseminated organic The Dutchtown has a consistent thick material are commonly present, and these ness of about 100 feet throughout most of together with the generally brown, dark the Illinois basin, but thickens abruptly in blue, and black color of the rock serve to the very southern portion of the State to a distinguish it from the overlying Joachim maximum thickness of more than 600 feet. formation. Three members have been de scribed67 : dark brown to black dense and oc STRATIGRAPHIC RELATIONS casionally very finely crystalline limestone and calcareous shale and siltstone at the The stratigraphic relations of the top; dark brown to black argillaceous lime Joachim and Dutchtown formations have stone, calcareous hard platy and fissile shale, been discussed. From the evidence at hand, and calcareous siltstone in the middle; and it appears that the Dutchtown formation grades laterally, particularly to the west, 56 amed fo r the vi ll age of Dutchtown, near Cape Gi rardeau, Missouri , for the rocks which lie between the from the typical facies observed in the Joachim dolomite above and the St. Peter and Everton Illinois basin and Cape Girardeau areas sandstones below. McQueen . H. S., op. cit., p. 12 . 67M cQueen, H . S., op. ci t., pp. 15-19. into a facies difficult or impossible to dis- 28 MAQUOKETA AND "TRENTONn FORMATIONS tinguish from the Joachim formation. It interpreted as representing offshore sedimen appears possible that the "Joachim" of tation. Calhoun County, Illinois, and of north central Missouri is in reality composed of a MAQUOKETA FoRMATION thin but massive unit at the top, represent ing the Joachim as known in the Illinois The resistivity curves show well the basin, and a considerably thicker thinly middle carbonate zone of the Maquoketa bedded sandy and shaly unit below, which formation, especially in the north-south is correlative with the Dutchtown and cross-section, and indicate the high car grades laterally into it. An alternative sug bonate content of the lower shale unit in gestion is that the Dutchtown is not a valid the deeper portions of the Illinois basin and formation, and that it represents an exten in the western part of the State. The lack sive and distinct facies of the lower portion of consistency of the individual beds from of the unrestricted Joachim formation. one well to another and the lack of con sistent trends in facies changes, except in a very general fashion, should be noted. CRITERIA FOR RECOGNITION Owing to the presence of argillaceous and The Dutchtown formation is charac silty limestones in the basal Silurian Edge terized by a lack of anhydrite and gypsum wood formation there is no sharp change in in contrast to the Joachim formation above, the resistivity curves at the top of the and by a decidedly darker color throughout. Maquoketa formation, but there is an Shales and dolomites described as "very abrupt change in them at the contact be dark brown to black" are the rule. Sand tween the Maquoketa and Galena forma and shale are common in the cuttings. tions. Electrically the zone has a very irregular low-resistivity and a very irregular self GALEN A FORMATION potential. The north-south cross-section illustrates the thinning of the Galena formation in a DISCUSSION OF southerly direction. Also apparent in some CROSS-SECTIONS of the electric logs is a tendency toward lower resistivity values in the lower part of Two cross-sections of the Maquoketa and the formation. The lower boundary of the "Trenton" accompany this report. Their formation in central and southern Illinois upper limit is marked by the base of the is marked by a sharp decr.ease in resistivity Silurian system, their lower, by the top of in all electric logs except No. 7 in the north the St. Peter sandstone. The first (pl. 1) south cross-section, in which the lower limit is a diagram drawn on a north-south line is coincident with a well marked break in from Cook County, Illinois to Ballard potential. County, Kentucky; the second (pl. 2) is an east-west cross-section from Lawrence to PLATTIN AND DECORAH FoRMATIONs St. Clair County. One well, No. 8 on the north-south cross-section and No. 6 on the The Decorah formation has been m cast-west cross-section, is common to both. cluded with the Plattin formation in the The data on the cross-sections are derived cross-sections because of the difficulty ex from sample studies, or electric logs, or both perienced in separating it as a unit of con where available. sistent lithology. Most wells show a shaly The most striking feature of the diagrams zone of low resistivity at this horizon, but is primarily the pronounced and progressive there is no close correspondence or consis overlap of the middle Ordovician_ strata tent trend from one area to another. from south to north, and secondarily, the The Plattin formation may be divided relative consistency in thickness of the on the basis of resistivity into at least four several formations and zones rq_ the ·areas zones. Because considerable variations in SUBSURFACE RELATIONS 29 res1st1v1ty are represented by scarcely dis regularly in the lower portions. It is this cernible changes in gross lithology, it has unit, or some portion of it, to which the not been thought wise to set up criteria name "Stones River" has been applied in from sample studies in order to differentiate Missouri. these zones. It is believed that slight varia tions in amount of insoluble residue and de JOACHIM FoRMATION gree of dolomitization are largely respon sible for the variations in the resistivity It is believed, as noted previously, that the electrical responses present a more con curves. Of the four zones the uppermost (in sistent picture of Joachim relations than cluding the Decorah) is about 130 feet does gross lithology. The Joachim is repre thick and is especially well marked in the sented by a high-resistivity unit between the wells in central and southern Illinois, where lowermost zone of the Plattin and the ar it consists of an upper high-resistivity unit gillaceous beds of the Dutchtown formation. and a lower low-resistivity unit. Although It thins to the north and west. impossible to prove with the data available, it seems likely that this zone is continuous over northern Illinois as well and may be DuTCHTOWN FoRMATION the equivalent of the Spechts Ferry and Below the Joachim high-resistivity unit Magnolia members of the Platteville phase. is a zone which throughout most of central The second zone of the Plattin is repre and southern Illinois varies between 100 sented in the same areas and varies in thick and 150 feet in thickness and which is ness from 150 to 250 feet where most fully characterized by very irregular moderate to developed. This member is dominantly a low-resistivity values. This zone has the high-resistivity zone with intercalated units lithologic characteristics of the Dutchtown of low resistivity. Its base is marked by a formation and may be traced southwesterly very low-resistivity zone in all electric logs, into the outcrop area of the formation. To and occasionally by shale in the cuttings.68 the east and west, however, the distinctive It may represent the Mifflin and Pecatonica beds tend to be replaced by others similar members of northern Illinois. to the Joachim formation in composition. The third unit consists of a zone of high The subjacent St. Peter sandstone can resistivity bounded above and below by seldom be separated from the Dutchtown zones of lower values. It has a maximum formation on the basis of resistivity but is thickness of about 7 5 feet, thins gradually usually marked by a relatively negative po northward, and in Ford and Kankakee tential. counties it appears to be overlapped by the next higher zone. REGIONAL INTERPRETATION The fourth and lowermost zone consists OF THE PRE-DECORAH BEDS of strata with generally lower and more irregular resistivity values than those above. Reference has been made in this report It has a maximum thickness of about 100 to the progressive overlap from south to feet in Jackson County and thins northward north of the rock units between the Galena to the region in which it is overlapped by and St. Peter formations (fig. 6, 7). This is shown diagramatically in figure 8. In the overlying third zone in Champaign and geologic literature there is an occasional Ford counties. One or more shale units are reference to the possibility that the St. Peter generally present in the lowermost portion, is a transgressing sandstone. This idea was and conglomerate zones (known from the strongly stated in regard to the Joachim cuttings) occur frequently but probably ir- formation as follows : 68T he similarity of most " Trenton" shales often makes The Joachim formation has been interpreted it difficult, particularly in rotary-well samples, to differen as an off-shore equivalent of the St. Peter sand tiate between "(aved" shales and those which are in stone. This sandstone is believed to be a place. It is thus frequently impossible to be sure whether shale does, or does not, accompany any particular variation transgressing formation which was deposited in the curve of the electric log. adjacent to the shore line as it advanced from 30 MAQUOKETA AND " TREN TON" FORMA TION S ISOPACH MAP E. P. DuBOIS JANUARY I, 1945 DATUM POINT .. ······ ...... BOUNDARY BETWEEN GALENA AND OVERLYI NG FORMATIONS THICKNESS OF STRATA BETWEEN BASE OF GALENA AND BASE OF DUTCHTOWN FORMATIONS AREA IN WHICH GALENA - PLATTIN (PLATTEVILLE) FORMATIONS CROP OUT OR ARE COVERED ONLY BY GLACIAL DRIFT OR PENNSYLVANIAN STRATA; THICKNESS VARIABLE SCALE 0 10 20 30 40 50 MILES FIG. 6 SUBSURFA CE RELA TION S 31 , ISOPACH MAP i OF THE __l ______STRATA FROM THE TOP OF • i THE GALENA TO THE BASE OF . ·~- - ---, THE DUTCHTOWN FORMATION • ! .l, BY E. P. DuBOIS JANUARY I, 1945 - '------· ~~ r! I -----r --·~ I iI ,_l! ______I - ~~ ------! • • I I I --r- -- -!______l • ,I ,I , I I .DATUM POl NT _..· ·"·.______.- BOUNDARY BETWEEN GALENA AND OVERLYI NG FORMATIONS ~300 THICKNESS OF STRATA BETWEEN ~ TOP OF GALENA AND BASE OF DUTCHTOWN FORMATIONS AREA I N WHICH GALENA-PLATTIN (PLATTEVILLE) FORMATIONS CROP OUT OR ARE COVERED ONLY BY GLACIAL DR IFT OR PENNSYLVANIAN STRATA ; THICKNESS VARIABLE SCALE 0 10 20 30 40 50 MILES FIG. 7 32 MAQUOKETA AND "TRENTON" FORMATIONS Northern Illinois Southern Illinois ~ SHALE . [].. SANDSTONE ~ LIMESTONE ~ DOLOMITE FIG. 8.-Diagram showing transgressive relations of the St. Peter sandstone and superjacent formations in Illinois. a position at least as far south as northern carbonate rocks. Where such unconformities Arkansas, to Minnesota. As the areas to the south became more remote from the shore the do exist, the relief is of the order of a few more calcareous sediments were initiated and feet only. continued during the submergence of the area. 3. It appears from this study that in Under this conception the Joachim limestones of Ste. Genevieve County (Missouri) were de Illinois all of the strata between the St. posited contemporaneously with some portion of Peter and the Decorah formations were laid 5 the St. Peter sandstone farther north. a down continuously in a sea that transgressed With the new data presented in this steadily from south to north, and there is report and with the additional knowledge no evidence that the area emerged from the which derives from these data, it appears sea during this time. possible to extend this concept stratigraphi 4. In the Minneapolis area the St. Peter cally to include the entire series of carbonate sandstone and Glenwood formation contain rocks below the Decorah formation, and, fossils closely related to those in the over in northwestern Missouri particularly, to lying Platteville beds; in southern Illinois include also the Decorah and Galena forma and southeastern Missouri the St. Peter tions where these rocks are reported to rest sandstone is overlain by the Dutchtown directly upon the St. Peter. formation and is thus Chazyan or older in The facts are as follows : age. 1. There is a major unconformity every 5. There is no evidence that an uncon where at the base of the St. Peter sandstone, formity ranging from Chazyan to Black with a local relief of as much as 500 feet River in age is present on the surface of the in some areas. St. Peter. 2. In but few localities is there an un 6. In most areas the St. Peter sandstone equivocal unconformity between the St. is succeeded by green or brown shales which Peter sandstone and the overlying transition pass upward into a dolomite sequence of beds, or between them and the overlying variable thickness, which in turn is overlain 59Weller and St. Clair, op. cit., p. 104. by limestone. SUBSURFACE RELATIONS 33 It is the writer's belief that the best m1t1zation was original or came about interpretation of these facts is that the St. shortly after the deposition and before lithi Peter sandstone represents the littoral de fication of the limestone is not certain. Some posits of a sea which transgressed from south dolomite in the sequence is undoubtedly to north over Illinois continuously from secondary. Mediterranean conditions prob Chazyan through Platteville times. Next to ably accounted for deposition of gypsum the littoral sand there was a narrow belt during Joachim times. in which dominantly green muds were being The Everton formation in Missouri may deposited, then perhaps a wider belt in represent a part of this same series of trans which dolomitic mud (or lime mud which gressive events, but the actual relations are was later dolomitized) was deposited, and not clear. then the wide off-shore areas in which lime Study of the southernmost well used in mud was deposited. Thus there resulted this report, in Ballard County, Kentucky, a contemporaneous seaward sequence of indicates that the post-St. Peter sequence sandstone (aeolian, lagoonal, and marine) , continues to thicken to the south and be shale of the Glenwood type, dolomite, and comes more argillaceous in that direction. limestone. The limestone and dolomite were It seems likely that the sediments are con deposited in horizontal strata that constitute tinuous with the Womble shale of the the Dutchtown, Joachim, and Plattin Ouachita province. However, correlation formations, but the sandstone and shale and knowledge of the Ordovician strata in facies formed continuous lithologic units the Ouachita area are still so tentative that that transgressed the entire time equivalent. no definite conclusions can be presented. Minor fluctuations in sea-level and sources Preliminary study indicates that these beds orsand accounts for interbedding of clastic were deposited in a geosynclinal trough, the and carbonate deposits in the near-shore axis of which trends north and south and areas and for the occurrence of shales which lies between the Ozark barrier on the farther offshore and therefore well up m west and eastern Kentucky and Tennessee the carbonate sequence. Whether dolo- on the east. 34 MAQUOKETA AND UTRENTON" FORMATIONS FIG. 9.-Area of possible occurrence of sandstones in the Maquoketa formation. PETROLEUM POSSIBILITIES OF MAQUOKETA AND "TRENTON" IN ILLINOIS BY CARL A. BAYS The foregoing study clarifies the strati commercial production in the zone are re graphic relations of the strata of · the mote. Maquoketa and "Trenton" formations in The fine-grained sandstones and siltstones Illinois so that consistent nomenclature and of the Maquoketa formation are more classification may be applied in petroleum generally present in the upper shale member exploration. From these studies and the but are also present elsewhere in the forma relations demonstrated, certain suggestions tion. It is not possible to predict the occur as to the possible occurrence of petroleum rence of these sandy zones stratigraphically in these strata may be made. The possibili from evidence now available, but the ties of the occurrence of permeable zones studies to date give considerable suggestion which may contain oil in commercial quan of their areal extent. Although these sand stones are thin, irregular, and cemented as tities may be suggested and the likely areas revealed in cuttings from many wells, they for exploration may be delimited. Because do not appear to have less satisfactory tex of the broadly conformable relationships of ture in some wells than sandstones now pro the various formations, the existence of ducing commercially from Chester and stratigraphic traps seems unlikely. Pennsylvanian formations. On the basis of data on distribution now available, the ac MAQUOKETA PossiBILITIEs companying map (fig. 9) indicates the areas Petroleum possibilities in the Maquoketa of possible commercial reservoir texture and formation are thought to be limited to two therefore possible production on favorable zones, the middle limestone zone and the structures from sandstones interbedded in sandstones of Thebes type which are inter the Maquoketa formation. The area thought bedded with the other lithologies of the most favorable is in the southwestern por formation. tion of the State. In some areas in northern Illinois, local permeability has been found in the middle GALEN A PossiBILITIES limestone zone of the Maquoketa. In some Permeability in the Galena beds seems very local areas this zone produces con to be largely secondary and the result of siderable quantities of water. Generally solution, associated in some areas with these areas are small, limited to shallow dolomitization. Production obtained to date depths, and are along the crests of anti has been in consistent "breaks" which are clinal structures where the top green shale locally usually the same depth below the zone is completely absent as a result of pre top of the formation. Little actual permea Silurian erosion, and Alexandrian strata bility through connection of pore spaces in rest on the middle limestone. In such areas these rocks seems to exist, as porosities up the permeability is thought to be largely a to 25 percent have been measured in cores result of secondary-solution cavities and in which there was no measurable permea crevices developed by weathering and bility. Therefore, commercial production is groundwater action. In no portion of central expected to be found in the areas where and southern Illinois is there any evidence there has been the best opportunity for of the presence of permeability in the middle development of secondary permeability. limestone zone of the Maquoketa. There The area considered most likely for the fore it is concluded that the possibilities of development of good permeability is where [ 35 J 36 MAQUOKETA AND " TREN TON" FORMA TIONS MOST FAVORABLE FOR ~ TESTING ON STRUCTURE . PERMEABILITY RARELY []. . FAVORABLE UNFAVORABLE FOR PRODUCTION FIG. 10.-Petroleum possibilities of Galena strata. OIL AND GAS POSSIBILITIES 37 the pre-Maquoketa unconformity is best outcrop areas in northern Illinois, sufficient developed and where the Galena formation permeability has been found to permit the is thinnest. This area is on the flank of the production of small quantities of watEr St. Francis ( Ozark) uplift and is indicated from these zones but such instances are ex by the isopach map of the Galena strata ceptional. There are no known occurrences (fig. 5). This has been borne out by de of permeable cherty dolomites at the posi velopments of the "Trenton" to date al tion of the Decorah at depth in the subsur though other areas of saturation in the face in Illinois which might have commer "Trenton" such as those described by cial permeability. Although oil stains and C ohee1 in Clark and Kankakee counties have shows have been found it is not believed been found. Most of the tests to date out likely that permeability or production in side the area of thinner G alena have failed commercial amounts are to be expected from to find commercial permeability, although it Decorah, Plattin, or Joachim formations in must be recognized that wherever past geo Illinois. However, there has not been suffi logic conditions may have permitted the cient testing of these zones to reach a defi development of such secondary permeability, nite conclusion, as many of the "Trenton" commercial production is possible although tests have stopped in the Decorah formation. the areas cannot be recognized from evi dence at present available. DuTCHTOWN PossiBILITIEs On the basis of these conditions the ac In some wells oil shows have been found companying map (fig. 10) has been pre in the Dutchtown formation. In outcrop pared. Four areas are indicated: 1) Area Dutchtown beds are typically petroliferous. most favorable for testing of Galena be Most of the limestones and dolomites in this cause of development of the pre-Maquoketa formation have been found to be "tight" in unconformity and the likelihood of com wells drilled to date and the interbedded mercial permeability being present; 2) area sandstones are well-cemented, so that per of possible Galena production but where the meable reservoir strata have not been found. conditions for permeability are not favor However, many of the interbedded sand able on the basis of available evidence ; ( 3) stones are of sufficiently coarse texture that area unlikely to have commercial Galena they may be regarded as possible reservoir production because of proximity to outcrops, beds where the cementation may not be de presence of fresh water, or on the basis of veloped. There has been insufficient testing testing done to date; and 4) area of outcrop of all of the strata below the Decorah or absence of the Galena due to erosion. formation, to preclude the possibility of commercial production in them, and this is DECORAH-PLATT IN-}OACHIM particularly true of the Dutchtown forma PossiBILITIEs tion. No commercial production has been ExP LO RATION found in the tests drilled through the De In all developments of "Trenton" strata corah, Plattin, and Joachim formations in in Illinois to date, production has been Illinois to date. These beds are irregularly obtained on closed anticlinal structures. dolomitized and although high porosity may The oil-shows found to date in the sand be present, there is little evidence of the stones and limestone of the Maquoketa development of any effective permeability. formation and in the older formations have None of the zones of high-negative potential apparently been related to anticlinal struc in electric logs of the Plattin and Joachim tures, where data were available on the have been tested nor has their· effective per local conditions. Therefore it is suggested meability been determined, so far as is that exploration can be conducted first by known. In some very local areas, near the location of anticlinal structures, using sur face, subsurface, and geophysical methods 1 Cohee, George V., " Trenton" production in Illinois: l ll ir.ois Geol. Su rvey Illinois Petroleu m o. 39, 1941. commonly in use, and second by deepening 38 MAQUOKETA AND "TRENTON'> FORMATIONS or drilling of tests to these zones where ton" strata of Illinois are most likely to shallower anticlinal structures have been occur in the sandstones of the Maquoketa proved. formation and the areas of secondary per Because the possible producing zones of meability in the Galena formation. There the Galena have permeability due to secon has been insufficient testing of strata below dary solution cavities and crevices, samples the Decorah formation. The southwestern and cores may not be indicative of the pro portion of the state is recommended for ex duction possibilities of any shows encoun ploration of the Maquoketa formations, and tered. Drillstem testing or actual production the area flanking the Ozark uplift in south tests with acidizing of the possible zones western Illinois is thought most favorable are considered the best methods of obtaining for testing the Galena formation. Inasmuch full information. as the evidence suggests anticlinal rather than stratigraphic-trap control of produc SuMMARY tion, normal structural methods of surface, Possibilities of commercial petroleum subsurface, and geophysical exploration are production from the Maquoketa and "Tren- applicable. ILLINOIS STATE GEOLOGICAL SURVEY REPORT OF INVESTIGATIONS No. 105 1945 4 3 6 7 9 5 8 10 51 IAN 2 SYSTEM _] MAQUOKETA !_ GALENA GALENA (KIMMSWICK) "DCCORAH" PLATT IN ------ ------ INDEX MAP OF ILLINOIS JOACHIM SHOWING LOCATION OF CROSS- SECTION DUTCHTOWN ST PETER NORTH -SOUTH CROSS -SECTION BY E. P. Ou BOIS WFI LS AND LOCATIONS LEGEND KEY TO ELECTRIC LOGS LIMESTONE V!SKING CORPORATION, WELL NO. 3, ~ SE.C . ti, T, 38 N., R. 13 £ ., COOK COUNTY DOLOMITE 2. .J0LI£T CITY WELL, OTTAWA STRE:tT, ~ SELF- POTENTIAL RESISTIVITY SEC.~. l 35 N., It 10 E., WILL COUNTY SHALE 3. BRAtOWOOO 0E.£:P WELL, NO. I, ~ (-)MILLIVOLTS(+) -OHMS M2M~ SEC. 8, T. '3Z N., R 9 E., WILL COVNTY SILTSTONE 4. HERNDON DRILLINC. CO., F'ECHT NO. I, D- SE:t. 33, T. 2& N., R. 9 E., FORO CbUNTY SANDSTONE 5 9AAB£A AND Si£.V£Ai, LINDStY NO. I, [] SEC. ZO, T. 20 N., II'. 8 E., CHAMPAIGN tOUHtY GYPSUM OR ANHYDRITE •~ &. CAIUER OIL C:O., .StAMAN NO. I, 8 ~ J SEC. 35, T. 12 N., Fl.. 7 E., COLES COUNTY 0 CHERT u 7. CARTER Oil. CO., BR,t.UtR NO. 6, I", I u St:C. 21, T. e N, R. 3 t., F'AYETfE COUNi'l' BOUNDARIES BETWEEN s. TEXAS COMP.. NV, TAT£ NO. 2:1, SIGNIFICANT ZONES OF SEC. 5, T. I N., R. i [:,, MARION COUNTY F"EET ELECTRICAL RESISTIVITY IN Q. S'tANOLIND OIL AND GA~ CO., l..ttNER NO. I, SEC . .20, f. 7 S., ~- 4 W. 1 JACKSON COUNTY 10. ROBINSON PUCKETT, H.JC:., CLARK NO. I, 22-H- 5, BALLARD COlJNfV, KENTUCKY l::rL======~~======~T~H~E=P=L=A=T==T=IN==f~O~R=M==A=T=IO=N==~ [ 10 20 30 40 MILES 8 INDEX MAP OF ILLINOIS SHOWING LOCATION OF CROSS- SECTION 2 4 6 7 SYSTEM KEY TO ELECTRIC LOGS ~C..Lr- rVI C.. I'm IAL ( -)MILLIVOLTS(+) -OHMS M2M- GALENA (KIMMSWICK) "DECORAH" ------ ------PLATT IN ------LEGEND WELLS AND LOCATIONS ~ LIMESTONE S. G. LOCKWOOD, DVROF'F NO. I, SEC. 26, T. I N., R. 10 W., ST. CLAIR COUNTV ~ DOLOMITE EASON OIL CO., THOMAS NO. I, SEC. 4, T. ! S ., R. 8 W., ST. CLAIR COUNTY ~ SHALE 91C OOVR On.. "'NO CAS CO., VOCI:C "10. I, SEC. 18, T. 2 N., R 6 W., ST. CLAIR COUNTY D SILTSTONE 4 WILL T.4.TUM, SCHRAGE NO. I, SEC 17, T 3 N, R. 4 W, CLINTON COUNTY ED SANDSTONE 8 E MARTIN, ROBINSON NO. I, SEC 4, T 2 N., i'l . I £., MARION COUNTY B GYPSUM OR ANHYDRITE TEXAS COMPANY, TATE NO. 21, SEC 5, T. I N., R. 2 E., MARION COUNTY EJ CHERT PURE OIL CO., BILLINGTON NO. 3, SEC. 27, T I N, R. 7 E., WAYNE COU NTY ---- BOUNDARIES BETWEEN SIGNIF ICANT ZONES Of" S. OHIO OIL CO., MIDDAUGH NO. 23, ELECTRICAL RESISTIVITY I~ SEC. 32, T 4 N, A. 12 W, LAWRENCE COUNTY THE PLATTIN FORMATION EAST -WEST CROSS- SECT ION BY E. P. Du BOIS F'EET l::r'------" ~ ~0 20MILES