£S7 no. ^ GUIDEBOOK for the Sixteenth Annual Field Conference of the TRI-SME GEOLOGICAL SOCIETY by J» S. Temple ton and H. B % Willman Illinois Geological Survey 5, f?5 LLINOIS CENTRAL NORTHERN ILLINOIS October 11 and 12, 1952 Illinois Geological Survey Urban a, Illinois GUIDEBOOK SERIES ILLINOIS STATE GEOLOGICAL SURVEY 3 3051 00006 3226 2 a. o Q) 5 ^_ 0) c o • «o c o E o cr * o O o a) c O —<*> 3 o o o Q. E o v> . Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/guidebookforsixt02tris 3. SIXTEENTH TRI -STATE GEOLOGICAL FIELD CONFERENCE ANNOUNCEMENTS Headquarters - Nachusa Hotel, Dixon, Illinois (see map, fig. 2). General Schedule - The conference will assemble at 8 A. M % Saturday morning, October 11, at Stop 1, in Dixon, and will return to Dixon at 5:^5 P. M„ It will n.. -assemble at 8i30 A, M. Sunday morning at Stop 9, nineteen miles northeast of Dixon, and will disband at noon Sunday at Stop 12, six miles south of Rochelle. The entire trip has a length of llU miles. .annual Dinner Meeting - The annual dinner will be served by the Ladies auxiliary of the First Presbyterian Church at the Loveland Community House, Dixon, on Saturday, October 11, at 7 P, M % Tickets ($1.75) will be distributed Saturday morning at Stops 1 and 2. MAPS nND SECTIONS Figure Page 1. Geologic Map showing stops 1 2. Dixon City map h 3, h* Columnar sections 10, 11, 12 5 . Structure map of norths rn Illinois 13 6. Structural features of the Dixon-Oregon area,.... lU 7. Glacial map of northern Illinois 15 8. Pleistocene history of Rock Valley , . 16 9. Stop 1 18 10. Stop 2.., 20 11. Stop 3 22 12. Stop h 22 13. Stop 5 . 28 Ik, Stop 7 32 15. Stop 8 , 35 16. Stop 9 1x2 17. Stop 12 t U6 Topographic maps of the Dixon and Oregon quadrangles will be available for reference in the lead and rear cars. » • * » * V County highway to White Pmes Forest State Park U.S. 52 to Savanna I. 26 to Freeport to Grand Detour Oregon Rockford B-Blackhawk Hotel D- Dixon Hotel N-Nachusa Hotel, Headquarters U.S. 52 to Joliet to Princeton FIG. 2- MAP OF DIXON, ILLINOIS 1/ STRATIGRAPHY The Dixon-Oregon area is underlain by about 3> 700 feet of sedimentary strata. The lower 2,800 feet is Cambrian resting on pre-Cambrian granite and the upper 900 feet is Lower and Middle Ordovician (fig. 3). More than 96 percent of the sequence consists of dolomite and sandstone, and less than h percent, largely confined to the Cambrian Eau Claire formation and the Champlainian (Middle Ordo- vician) Glenwood subgroup, is composed of shale. The only limestone occurs in the Platteville group, chiefly around Dixon. Formations below the Franconia formation are known only from well cuttings, but the Franconia and all younger formations are exposed. Because of the regional southwestward dip, Upper Ordo- vician shale, Silurian dolomite, and Pennsylvanian sandstone are found within a distance of 1$ miles to the west, but will not be examined on this trip. The region is of particular strati graphic interest because its isolated Cambrian and Lower Ordovician exposures are important in correlating the relative- ly near-shore Wisconsin sequence with the deeper-water Missouri sequence. Al- though many of the sandstones in the Wisconsin section grade southward into dolomite, the carbonate formations undergo relatively little change from north to south. Champlainian Classification Studies in progress since 19^0 on both outcrops and well cuttings have shown that the classification of the Champlainian (Middle Ordovician) rocks of Illinois is not adequate for refined work, that it violates certain natural boundaries, and that it contains sons mis car relations. A revision of the classi- fication is shown in figure 3» L Although new strati graphic names are given for convenience, the names are not formally introduced and defined in this guidebook, but will be brought out in a forthcoming paper. The revised classification is based on detailed studies throughout Illinois and in the outcrop areas of surrounding states, and on reconnaissance studies in Kentucky, Tennessee, Virginia, Michigan, Ontario, and New York. These studies were made to determine the relative rank of the units, the persistence of physical breaks, the extent of facies change, and the correlation with the stan- dard section of New York state. Although a great variety of lithologic, faunal, and diastrophic criteria have proved valuable in this study, the vertical varia- tion in the relative degree of argillaceousness has been found to have the widest regional extent and to be most useful in differentiation of the carbonate sedi- ments. Relatively minor differences in argillaceousness can be traced by matching sequences throughout much of the eastern United States and even into the marginal parts of the Appalachian geosynclinal areas, where the units thicken greatly. Differences in relative argillaceousness commonly extend through areas of carbon- ate facies-change and are believed to reflect regional diastrophic movements of a periodic or cyclic character. 1/ This guidebook contains considerable unpublished stratigraphic and structural information which is currently being prepared for publication. 6. Lateral gradation from dolomite to sandstone within short distances is common in the Ancell group of Illinois (St. Peter-Glenwocd strata of northern Illinois), but in most of the higher beds facies change is gradual and moderate, and is not a major iniluence on classification. Regional evidence provided by the continuity of the lithologic succession, by bentonites, by erosion surfaces, and by faunal zones indicates that the formations and menb ers in the new classi- fication are essentially rock-time units which do not transgress tims lines. Several of the members which are thin and weakly differentiated in northern Illinois nevertheless are persistent and recognizable throughout most of the state, and greatly increase in thickness and distinctiveness in southern Illinois and Missouri. The Platteville group thickens to more than 600 feet in southern Illinois and the Glenwood equivalents to IjOO feet, whereas the same se- quence in the upper Mississippi valley commonly has a combined thickness of less than 100 feet. The distinguishing characteristics of Gal en a -Platteville formations in the Dixon-Oregon area, listed below in descending order, supplement the data in figure 3* GALENA GROUP Dubuque , * 30 ' : dolomite, argillaceous, finely and coarsely crystalline, crinoidal, thin- to medium-bedded, shaly, with red flecks and red shale partings south and southeast of type area. Wise Lake , * 90 ' : dolomite, pure in upper part, slightly argillaceous in lower part, brown, coarsely crystalline, vuggy, massively bedded. Dunleith, + 125': dolomite, pure and argillaceous in alternating units, cherty, medium crystalline, medium- to thick -bedded; has gray flecks, green shale partings, and Resserella toward base. Guttenberg , * 5 ' : dolomite, argillaceous and finely crystalline to pure and coarsely crystalline, red-speckled and with red shale partings. Sower- byella common. Spechts Ferry , Missing: green shale and limestone with Pionodema in north- western Illinois. — Unconformity — PLATTEVILLE GROUP Quimbys Mill , * 12': dolomite, argillaceous and cherty, yellow buff, chalky, thin- to thick -bedded, with shale partings in middle. Nachusa , * 18': dolomite or limestone, pure except for argillaceous unit in middTe, cherty, fucoidal, thick-bedded, with Foerstephyllum , Lichenaria , and Tetradium . Grand Detour , » 50 ' : dolomite or limestone, alternately pure and argilla- ceous, partly cherty, thin- to thick -bedded, with some red shale partings. More dolomitic, less argillaceous and shaly, and thicker- bedded than underlying Mifflin for nation. Mifflin , * 25 ' : limestone or dolomite, alternately pure and argillaceous, non-cheriy, thin- to thick -bedded, with gray-green shale partings. Pecatonica , * 30': dolomite and limestone, relatively pure, locally cherty, finely crystalline, and thick -bedded; is slightly argillaceous and has weak shale films in middle. Ferruginous corrosion surface at top; diastem and phosphatic nodules at base. MAJOR EVENTS IN THE PLEISTOCENE HISTORY OF ROCK RIVER VALLEY The preglacial Rock River (fig. 8), entrenched in the Lancaster pene- plain, ran southward from Rockford to the vicinity of Princeton where it joined the southeastward-trending ancient Mississippi River. The preglacial Rock valley- lay about 2$ miles east of Dixon and was joined by three major eastward-flowing tributaries which followed the present valleys of the Pecatonica River, of Leaf River and Stillman 1 s Run, and of Gale Creek and Kyte River. Pre-Illinoian Pine Creek ran southward for about 6 miles past Grand Detour, and then turned south- westward, passing south of Dixon to join the ancestral Rock River. Although the pre-Illinoian history of this area is awaiting further study, the entire area was covered by the Illinoian ice sheet. When the Illi- noian ice melted, the ancient Rock valley south of Rockford was filled with drift* The waters of Rock River backed up in the Leaf River - Stillman Run pre- glacial valley until they overtopped a narrow divide at Oregon, fl-owed into the preglacial valleys of Pine Creek and Elkhorn Creek, and thence ran southward to the ancestral Mississippi valley, which had been reoccupied. Erosion through the divide at Oregon produced the present deep narrcw valley around the site of the Black Hawk statue. Because drift blocked Plane Creek valley south of Grand Detour, the post -Illinoian Rock River swung northward in a great loop and thai ran west along its present route past Dixon to Sterling where it joined south- ward-flowing Elkhorn Creek, The flow of water in the Stillman and Kyte valleys was reversed, so that these streams now run westward to join the Rock. The earliest Wisconsin glaciers, the Farmdale (inferred) and the Iowan, did not reach the Dixon-Oregon area, but the Shelbyville ice sheet, representing the initial advance of the Tazewell glaciation, invaded the eastern and southern parts of the area. The Belvidere lobe, advancing from the east, blocked the Sangamon course of Rock River between Rockford and Byron (fig. 7) and forced ths river westward, where it cut a deep gorge in Galena dolomite. This gorge is the youngest part of the present Rock valley. Although the Green River lobe advanced from the southeast across Rock River west of Dixon, the river appears to have found a route southwestward beneath the ice, along or close to its existing course. However, the Green River lobe diverted the ancient Mississippi River westward to its present position. During later Tazewell glaciation, whoi the Bloomington moraine was de- posited, a broad area on the south side of Rock valley was covered with outwash which consisted mainly of pebbly sand. The Green Bay lobe of the Valparaiso (Cary) glaciation reached Janesville, Wisconsin, and built a valley train of sand and gravel in Rock valley. Deposition of this material reduced the topographic relief of the valley by about 100 feet. The surface of this valley train is about 1*5 feet above the present flood plain. Subsequent down-cutting of the Mississippi and Rock valleys and deposition of an early Mankato valley train produced a lower terrace about 20 feet above the present flood plain of Rock River, J9 •'■;;"' ■ ; - f\ ' ■:u ■jn ' i t ia.-: •'" "'~ J v.' ' ' ■' ■'■■' '^.;-, ^ . > '"! i i ••,'.-.:. >, - < ' •. •"• • ' ' J. r ■^ *s r\ ' :> v r '0 ' : sn < i - • 'j "; .7 ■ ■V.K' . to v ! |.V "O • . : ' ■• K- ..'.'; . ' : :l 7/ T r '.-..•■ - - i ,.■„• i' '2 ■•_-,■■■ >■:■•} t ZsOO-A' '5 ■ ; « •i/'. ! i. . r . "' «i:'.-.:"-{f .; . 7 ' i ■ r ' I "Y .'/ ,- : r • • '-i •J . ■} 8. STRUCTURE The Dixon-Oregon area (figs. 5-6) exhibits unusually numerous, complex, and intense structures fcr the upper Mississippi valley. Folds having surface dips of from 10° to 30° are common, although such dips are of short lateral extent. More than sixty faults having throws of from 5 to 350 feet are known in the area, and at least two of these are thrust faults. The major structure of the area is the Ash ton arch , a broad, high anti- cline which brings formations as old as Fr an co nia ' to th e bedrock surface, and which extends from Kendall County northwestward for 80 miles to Rock River between Oregon and Dixon. The arch is bounded along its northern side by the Sandwich fault , which has a maximum downthrow of 900 feet on the north side, east of the Dixon-Oregon area. The Oregon antic line, a branch of the eastward-trending Savanna -S abula anticline , parallels the north side of the northwestern part of the Ashton arch and is separated from it by a narrow graben or syncline. West of Rock River the west end of the Ashton arch and the west Hank of the Oregon anticline plunge abruptly into the P o lo basin, which preserves rocks as young as the Maquoketa shale ( Cincinnat iah )". A dome called the Brookville uplift rises from the east end of the Savanna-Sabula axis, just northwest of tht. Polo basin. The LaSalle anticline is sharply defined as far north as southeastern Lee County, where it merges x^ith the southwest flank of the Ashton arch. However, the anticline seems to reappear in the Dixon area, separates the Polo basin from Illinois basin on the south, and finally merges with the Savanna-Sabula anticline. The Wisconsin arch is separated from the Dixon -Oregon area by a syncline on the north side of the Savanna-Sabula anticline. Although many of these structures were active in Lower and Middle Ordo- vician time, and faulting with at least 235 feet of throw occurred in pre-St. Peter time, evidence in other areas indicates that the major movements along the structures were in post-Mis si ssippian - pre-Pennsylvanian time and in the late Pennsylvanian or Permian periods. 9. REFERENCES Bevan, A. C, The Glenwood beds as a horizon marker at the base of the Platte- ville formation: Illinois Geol. Survey Rept. Inv. 9, 1926. Bevan, A» C, Cambrian inlicr in northern Illinois j Bull. Am. Assoc. Petr. Geol., vol. 23, pp. 1561-156U, 1939. Bretz, J H. , Geology and mineral resources of the Kings Quadrangles Illinois Geol. Survey Bull. U3C, 1923. Flint, R. F. , Glaciation in northwestern Illinois: Am. Jour. Sci. (5) vol. 21, pp. U22-U39, 1931. Horberg, Leland, Bedrock topography of Illinois: Illinois Geol. Survey Bull. 73* 1950. Knappen, R» S., Geology and mineral resources of the Dixon quadrangle: Illinois Geol. Survey Bull. h9, 1926. Leighton, M. M, , Differentiation of the drift sheets in northwestern Illinois: Jour. Geol. vol. 31, pp. 265-281, 1923. Rolfe, Doette, The Rock River country of northern Illinois: Illinois Geol. Survey, Educational Series No. 2, 1929. Templeton, J. S., The Mt. Simon sandstone in northern Illinois: Illinois Acad. Sci. Trans, vol. k3, pp. 151-159, 1950; Illinois Geol. Survey Circ. 170, 1951. Willman, H. B., and Templeton, J» S., Cambrian and Lower Ordovician exposures in northern Illinois: Illinois Acad. Sci . Trans, vol. kh, pp. 109-125; Illinois Geol. Survey Circ. 179, 1952. Workman, L. E., and Bell, A. H., Deep drilling and deeper oil possibilities in Illinois! Bull. Am. Assoc. Petr. Geol., vol. 32, pp. 20ul-2062, 19U8, and Illinois Geol. Survey Rept. Inv. 139, 19U9. FORMER CLASSIFICATION 10 REVISED CLASSIFICATION LITHOLOGY IN ILLINOIS LU X Thin - bedded, shaly 32 Pure, massive; Recepts Slightly arg.thick-bd. 50 40 Dunleith members are argillaceous at top and purer below •, i c feonnV ti- St. James members have dark gray flecks and green shale partings Ove' lying Wise Lake fm. is non- cherty and much purer. _I9_ _9_ 10 _I6_ 12 16 15 4 18 6 Red -speckled, med.-b'd. Thin-b'd.,red shale ptgs Green shale and Is. Fucoidal, medium-b'd. Thin-bedded, shaly Whitish, thick- bedded 5 5 2 Fucoidal, cherty, massive Argillaceous, med.-b'd. Fucoidal, thick- bedded Thin-bedded, shaly Pure^ thick - bedded Thin- bedded, shaly Calcarenite , massive Fucoidal , massive Thin- bedded, shaly Pure, thick- bedded Thin-bedded, shaly Fucoidal, thick -bedded Thin- bedded, shaly Pure, medium- bedded Thin-bedded, shaly 25 4 7 I0_ 6 FIG. 3-(Upper Half)- BEDROCK COLUMNAR AREA SECTION FOR DIXON-OREGON FORMER CLASSIFICATION REVISED MIDDLE ORDOVICIAN CLASSIFICATION // PRESENT LOWER ORDOVICIAN AND CAMBRIAN CLASSIF. LITHOLOGY IN ILLINOIS c/) Calcarenite, thick- b'd. Thick-bd, weakly shaly Pure, massive y 3 Slightly org. and shaly Pure, sandy, thick-bd. Argillaceous, silty O-l Shale, green, sandy Silty, fine and coarse 8 Arg., silty, sandy Silty, fine ond coarse Pure, well- sorted 200 Dolomite and Sandstone Dolomite Dolomite Cherty, sandy, thin- b'd. 100 Slightly arg. locally dole 30 Coarsely Xtln. thick-b'd 150 CAMBRIAN Arg. dol., sh. and ss. 25 Sandy, cherty, gray 22 Pure, buff, vuggy 80 Silty, sandy, glouc. 50 Ss, dole, glauc, shaly, with dolomite in middle 90 Dole , poorly sorted 100 Pure, well sorted 50 Dol., shale and ss. 450 Ss , conglomeratic Ss.,non- conglomeratic Ss., conglomeratic Ss., partly conglc. Ss , non-conglomeratic Ss., conglomeratic Ss.,non-conglc.,arkosic £55 70_ 17 5_ 335 _90 ILL 945 Pre-Cambrian granite \J Everton group of probable Chazy age in Southern Illinois FIG. 3 (LOWER HALF)- BEDROCK COLUMNAR SECTION FOR r\\\/r\K\-r\ocnr\K\ adca J2. STAGE SUBSTAGE DRIFT COL UMN 2$ LITHOLOGY RECENT y MANKATO Lake Chicago EE§^ — * * 111! WISCONSIN CARY Lake Border Tills present in Chicago area Tinley Valparaiso ■;„'•*', s s .*? * D ocE£ HO' > C O — - Valley-train gravel and sand along Rock River; loess? Manhattan - Rockdale Minooka 55 Tills present in Joliet area TAZEWELL Marseilles through Normal EE loess w Present southeast of area Metamora- 00 ' . c O o - — Till, outwash, and loess, present at SE. margin of area-, Bloom- ington till is pink and sandy Bloomington '^^.. >t|| 150' *> 9'de o o- —- 'o'o Till, buff, clayey, leached to about 4 feet; valley -train and loess; present at SE. margin of area Leroy ? %*S ■-T*V C^== 100' V— --z Shelbyville >tvT (Green River O \ ro , Lobe)-Stopll '©\7© : • 't) r - ^->|| 60' Till, buff, clayey, leached to obout 4^ feet; occupies southern part of area IOWAN Missing except for loess-!-' FARMDALE (Pro-Wisconsin) Thin or absent SANGAMON (interglocial) =.■=_- ^-_-_rr 5*+ Alluvial silts beneath soil; llli- noian till weathered to gumbotil ILLINOIAN (glacial) BUFFALO HART JACKSONVILLE Hi #3 20 ° Till, leached to8'-l2';has pebbles of Huronian jasper-conglomerate PAYSON Stops 6, 1 1 >o - LOVE LAND (Pro - 1 llinoian) ^ElrE rljfl 15'+ Silvena pro- 1 llinoian lake silt YARMOUTH (interglacial) _ Alluvial clay with carbonized plant frags, in pre -III. volleys *o • ft 4- *_» i KANSAN (glacial) Missing AFTONIAN (Interglacial) NEBRASKAN (glacial) i/Beyond the Tazewell drift-margin lowan loess and later loess is undifferentiated and is called Peorian FIG. 4- COLUMNAR SECTION OF PLEISTOCENE DEPOSITS IN THE DIXON-OREGON AREA 13 O en LU X h- q: o LU O o < UJ o» o LU X X I- »- O O Q_ * O O CO cr O o o a: o a: i- co r < tu or < o LU or o i z o X Q UJ I CD UJ or 3 < UJ u. < or Z> I- O or cn or o I CD U. GLACIAL GEOLOGY IN NORTHEASTERN ILLINOIS Compiled by George E. Ekblaw from data furnished by the Survey January 1, 1942 A- PREGLACIAL Rockfor d 3r '-^S 0/r f> ^ ^Byron V QOregon / WTJjrond Detour Rochelle 1 v O / Dixon \ /Sterling^O A- fc)y /p^e rn\ ( /^ ■**! V/' ^\ I o 1 / ■31 1 Rockford / ^ v ^- -.Byron 1" n Aoregon 1 <[ /(< x Rochelle \ Dixon /Sterlina/C \ Grand Detour k/ / Princeton C-WISCONSlN(Shelbyville; D-PRESENT GREEN RIVER LOBE Q Princeton Ro".kf jrd O Princeton I inch = 16 miles FIG. 8 -PLEISTOCENE HISTORY OF ROCK VALLEY 17. ITINERARY FOR SATURDAY, OCTOBER 11, 1952 (FIRST DAY) Mi leage Assemble at Stop 1 on River Street 1/2 mile east of highway bridge over Rock River on the south side of the river (fig. 2). 0.0 STOP 1 - RIVER STREET - UPPER P LA TTEVILLE AND LOWER GALENA STRATA . Abandone d quarry in SE.-J- SE.t SE *t Sec » 32 and S\ui SW.^ SW.-J Sec. 33, T. 22 N. , R. 9 E., Lee County (Dixon quadrangle). Discussion Leaders : H, B, Willman and J. S, Templeton See figure 9 . In the dolomite facies Galena (Trenton) beds generally are more coarsely crystalline, more porous, an d thi cker-bedded than Platteville (Black River) strata. The Jj4ek^Qra and St. Jamas members (•'Blue" and "Gray" members of the zinc-lead district) grade laterally into the Ion green shale member of the Decorah formation north of Guttenberg, Iowa. The Prasopor a zone at the top of the Ion extends eastward in the dolomite facies to Rockford, Illinois, but has not been found this far south. The basal Galena Spechts Ferry formation wedges out eastward and here is absent above the unconformable contact between the Platteville and Galena groups. At this locality the beds dip gently westward. Historical Note on Dixon (population 11,523) : In 1830, John Dixon, for whom the town ' is named," operated a ferry and tavern at Dixon for travelers from Peoria to the lead mines around Galena, Jo Daviess County, northwestern Illinois. In 1832, during the Black Hawk War, infantry and militia stationed at Dixon included Jefferson Davis, Abraham Lincoln, Gem Winfield Scott, Zachary Taylor, and Robert Anderson of Fort Sumter fame. Lincoln spoke at the Court House square during the presidential campaign of 1856. The geology of the Rock River valley was described first in 1861 by Dr. Oliver Everett of Dixon, a pioneer physician. Present Dixon industries include the manu- facture of cement, wire cloth, electric power and gas, shoes, indus- trial chains and valves, caskets, garage doors, cereals, feeds and condensed milk. The Green River Ordnance Plant is six miles south. O.ii STOP SIGN - at intersection of River Street and Illinois State Highway No. 2. Turn left (east) on 111* 2. The Nachusa formation is exposed in the road cut on the southeast corner of the intersection. For the next mile the route crosses a valley train terrace of Mankato age. I.J4 CAUTION - Tum left (north) onto black-top road past west side of Medusa Portland Cement Plant, leaving 111, 2. Cement is manufactured from the Mifflin limestone which is quarried north of the plant. The limestone is mixed with overlying Peorian loess (well exposed in recent cuts just east of thu turn) and with Pennsylvanian shale brought by rail from mine dumps near LaSalle. /8 CL Z> o rr LU _l < BEECHER MBR. 3'6" Dolomite, pure, nonshaly, noncherty, thick bedded. ST. JAMES MBR I7'9" BU^KtfOfcfi MBR > ^ " 59 Dolomite with weak green shale partings, argillaceous, whitish, and dense at top, but less argillaceous andshaly than underlying 8#ejwefft_ member. Resserella is common in Buck- _ ho r n- _St . Ja me s_be_d Sj_d Dolomite, argillcgeous, with/^re en shale partings -, bentonite 3' above base - , weak bedding break at top. GLENHAVEN MBR 1 <-» >> 28 Dolomite, red speckled, medium-bedded with Sowerbyella and Cyrtodcnta . GABNAVikrkO MBR. 7 T Dolomite.thin- bedded, with red shale partings and Sowerbyella . 7^777 CL o rr o > UJ h- r- < — I /.y /> / STRAWBRIDGE MBR. Dolomite, fucoidal, cherty, medium I r it 3'5 bedded, with Opi king SHULLSBURG MBR lf-s.ll 5'2 Dolomite, thin - bedded, with shale partings and Opikina . HAZEL, GFJEEN MBR. Dolomite, whitish- weathering, massive | where fresh, nonshaly. _ EVERETT MBR. 5*8" Dolomite, fucoidal, massive, with "white bed" and chert band at top, Foerstephy Hum common. Quarry floor \ \ F IG. 9 - STOP I 19. STOP 2 - DIXON NORTH - LOWER PLATTEVILLE STRATA* Abandoned quarry on east side of road, SW.J SW*J NW.i Sec. 22, T. 22 N*i R» 9 E», Lee County (Dixon quadrangle)* Discussion Leader t J* S, Temple ton See figure 10 » The top of the Pecatonica formation in the Tri -State region generally is marked by a ferruginous pitted corrosion surface, absent at Dixon North, but well developed at Stop 9. The Oglesby calcaremte, the youngest member of the Pecatonica formation, is absent in the upper Mississippi valley north of LaSalle, Illinois. 3 7 Turn right (east) on gravel road. The broad so uthwestward-tr ending depression on the right (south) side of the road is the abandoned channel of a tributary to pre-Illinoian Pine Creek. This tributary was blocked during the Illinoian glaciation by the Grand Detour esker. U.8 Turn risht (southeast) on gravel road. The Grand Detour esker rises from 30"to 70 feet above south (right) side of road for next mile. ^• 8 STOP SIGN - Junction with Illinois State Highway No. 2. Turn left (north) on 111. 2, 5.9 St. Peter sandstone is exposed in road cut on left (west) side of highway • 6.0 Cross Rock River. Half a mile west of the highway bridge the river swings two miles northward in a great loop which interrupts its general southwestward course and was named Grand Detour ("Big Bend'') by 18th century French fur traders. The northward diversion of the river was caused by deposition of Illinoian drift in a preglacial channel south of Grand Detour. 6.6 Historical Note on Grand_ Detour (population about 250) : Monument to Leonard Andrus~and John Deere, who manufactured the first steel mold- board plow in 1837 at this spot in the village of Grand Detour (founded I836). Prior to the invention of the steel plow, farming was largely confined to alluvial bottoms because wooden plows with cast iron tips and edges could not cut the tough mat of prairie grasses on the uplands. Deere later established an independent factory at Rock Island. Andrus' factory was later acquired by the J % I. Case Company and moved to Dixon, where plows were manufactured until 1927. The Case works is now located at Rockford. 6.7 Turn left (x*est) at sign pointing to Colonial Inn. 6.8 St. Peter's Episcopal Church, the first Episcopal Church established west of Chicago, built in 18U9 and still in use, is on the left (south). 20 DEMENT FM, 6' 8" Limestone , dolomitic, medium - bedded, nonshaly, poorly exposed. Q_ =) O zr ID LjJ > h- ■ nv . . ^T^ , T^^ i i BRITON MBR. lO'O" Limestone in thin nodular beds, shaly and fossiliferous. Thin purplish calcarenite layer at top. HAZELWOOD MBR. Limestone, fucoidal, thick- bedded ; corrosion surface at top. 5' 8" r-r 1 -/ ESTABLISHMENT MBR. Limestone, thin- bedded, with thin shale partings. Limestone, medium- bedded, nonshaly ' ■ I . 1 . 1 ■ 3 2' 6" shale partings BRICKEYS MBR 2'0" BOARMAN MBR 4' 5" Limestone, thin-bedded, with thin shale partings. o o c o D O 0 feet. 25. Mileage The Oregon anticline probably attained its present farm in late Pennsylvanian time, although upward movement began at least as early as Middle Ordovician. During the erosion of the Lancaster pene- plain, probably completed in Pliocene time, the anticline was truncated and the St. Peter sandstone exposed. In late Pliocene or early Pleis- tocene time, uplift resulted in removal of the friable sandstone and the creation of the Oregon basin, which drained eastward to the ancient Rock Valley and had a maximum relief of about 350 feet. Subsequently the basin slopes were mantled with Illinoian drift, Rock River was diverted to a position crossing the basin, and the floor of the basin was buried by Wisconsin vail ej-train and slackwater deposits. 30.5 Highway cuts expose St. Peter sandstone unconformably overlain by the Kingdom sandstone and the Daysville dolomite of the Gl^nwood subgroup. 31.7 STOP SIGN - Intersection of Illinois State Highways 2 and 6k in Oregon. Continue straight ahead on 111. 6U. The town is on a valley train of Cary (Valparaiso) age. His torical Note: Oregon, population 3*205, was founded in I836 by eastern settlers"! It is the county seat of Ogle County, named for Captain Joseph Ogle, a Revolutionary officer and early Illinois settler. Local industries include the manufacture of pianos, trucks for oiling roads, silica for pottery glaze, electric power from Rock River, foundry castings, milk products, furnaces, and coal stokers. 32.0 Cross Rock River. 32.2 Turn left (north) onto gravel road at west side of Phillips 66 Service Station. 32. h Turn left (west). The road is built on a valley train terrace of Mankato age, and follows a route made by bands of horse thieves who harrassed the settlers in the l8U0's. 32.5 Turn right (north). Glimpses of the Black Hawk Statue on a high wooded bluff to the north may be seen through the trees. 33.7 Road cut and old quarry on right (east) side of road exposes beds ranging from the Harmony Hill shale (uppermost Glenwood) at the base to the Quimbys Mill dolomite (uppermost Platteville ) at the top. The Mifflin formation is absent here because of contempora- neous uplift on the Oregon anticline, Elsewhere in the area, this up- lift is expressed by submarine sliding and folding of Mifflin strata. The beds here strike N. 83 W. and dip 12° NNE. off the north flank of the anticline. 33.9 Turn left (west) into Lowden Memorial State Park. 26. Mileage LUNCH STOP (ONE HOUR) AT LOWDEN MEMORIAL STATE PARK» Park and S ta tue - The park is th e former estate of the late Wallace Heckman, Chicago attorney, and recently was deeded to the State of Illinois. It is named in honor of Frank Lowden, former governor of Illinois, whose estate lies south of Oregon on the east bank of Rock River. The Black Hawk Statue, rising fifty feet from the crest of the bluff on the west side of the park, is the work of Lor ado Taft. It commemorates the American Indian as typified by Chief Black Hawk and was built of steel-reinforced concrete in 1910. The island below the bluff was the site of annual religious ceremonies by the Fox and Sauk tribes for many years prior to the Black Hawk War. The stone buildings at the north end of the park were used for many years by Mr. Taft to house a summer school for painters and sculptors. These buildings ("The Artists' Colony") and the store mansion on the south side of the park now are used by Northern Illinois State College at DeKalb for summer courses. Geology - The basal members of the Dunleith formation are exposed in the bluff below the statue. The top of the bluff rises 1^0 feet above Rock River. In establishing its post-Illinoian course Rock River here overtopped a preglacial divide two miles wide, and cut a deep narrow valley called the "Narrows" through Galena aid Platteville bedrock. There are good views of the valley from the statue and the Artists' Colony. Historical Note : In 1832, against the advice of Chief Keokuk, Black Hawk, a subchief of the Sauk, led his tribe from Iowa into the Rock River valley to stop infiltration of the valley by settlors who were violating a treaty guaranteeing the valley to the Sauk. Alt hough accompanied by their women and children, the Sauk were regarded as a war party by the settlers. Most of the settlers fled south to Princeton and LaSalle where the Indians remained quiescent under the leadership of Chief Shabbona, who was friendly to the whites. Militia and army infantry dispatched to Dixon caught up with Black Hawk's rear guard of forty warriors at Stillman's Run, a tribu- tary to Rock River nine miles northeast of Oregon. The militia were ambushed and routed, with a loss of eleven killed and fourteen wounded, and made a headlong retreat to Dixon, 25 miles away. Under army pressure, Black Hawk later retreated northward to Rockford and thence westward across southern Wisconsin to the mouth of the Bad Axe River, between La Crosse and Prairie du Chien. Here most of the tribe were massacred by a river gunboat while they were attempting to cross the Mississippi into lew a. Black Hawk remained a government prisoner until his death in lQh9- His last words were: "I loved the Rock River country, its hills, its forests, and its streams. I fought for it but it is now yours. Keep it as well as we did.'" 27. Mileage 3I4.O Turn right (south) on county read at entrance to park* 35.3 Turn left (east)* 35. h Continue straight ahead (east) at road intersectioni 3£,5 Turn right (south) at intersection* STOP 5 - OREGON »- FRANCONIAj TREMPEALEAU, ,'uND ST* PETER STRATA. . 1 1 1 !,, 1 nil , ■ ■ . . 1 y ' ■ ■!■ 1 —1 1. n 1 Quarry exposure and hill slope outcrops, W.j SE»-| NE*^ Sec. 3 (elongate), T. 23 N. , R. 10 E. , Ogle County (Oregon quadrargle). Discussion Leader : J. S. Tempi eton See figure 13* Strati graphy , A long-abandoned quarry on the right (east) side of the farm' lane affords the only known exposure of the Franconia formation in Illinois. This formation is the oldest which outcrops in the state. The Franconia consists of argillaceous silty glauconitic sandstone which is greenish gray, fine-grained, friable, and thin- bedded, and contains abundant accessory garnets. Some beds of impire buff dolomite also are present. The fauna, identified by G% 0. Raasch, consists of Dikellocephalus freoburgoisis Feniak, Il laenuru s truncatus Foniak, and S au kiella minor" tJlrich and Resser, fragmented oEoloid brachiopods and abundant worm castings. It is of Bad Axe (uppermost Franconia) age. The outcropping thickness is 30 feet, largely because of northeastward dip, but only a fraction of this thickness is well exposed. Trempealeau dolomite, mostly mantled by slumped loess, crops out in the oast quarry face, where it is 23 feet thick. The dolomite is silty, sandy, slightly glauconitic, pink to buff, finely crystalline and massive. Small algal reef cores of the Cr yptozoon type are present, but no other Trempealeau fossils have been found at this exposure. The uppermost part, about h feet thick, has been leached to a siltstone by pre-St. Peter weathering. The Trempealeau is separated from the overlying St. Peter sandstone by a major unconformity along which Lower Grdovician forma- tions (Guntcr dolomite and sandstone, Oneota dolomite, New Richmond sandstone, and Shakopee dolomite, in ascending order) have been removed by pre-St. Peter erosion in much of northern Illinois. Along the road south of the quarry, St, Peter ledges abut against Trempealeau dolo- mite, and on the hill slope south of t he road the St. Peter extends down to the valley fL oor. The sandstone is believed to have been de- posited in a pre-St. Peter channel. Structur e. The Cambrian strata in the quarry dip from 7° to 13° NE» Beneath the town of Oregon pre-St. Peter faulting has dropped if) t?9 Aomi|6ih siouji I I'M pa*D|OS|— I o» XjjDnb p lunos ^nia AjJDnb ;o qjnos pooy 9 auiAD^ s>)0O|q paduinis. ujoq pumaq 3do|S||!H- _p>y o O O o o o 4> D 0> 0. tn xxxx Ospb xxxx 0> V) o o O •- a • ■ .'a.*' 3 O *> o « Q. E a> "o -o c a> o n o — S J ^ "P~ P- o II c o u c o m CL O I- cr> Ll! GC 3 CO O CL X LU cr CD :e < o X CD O CC X h- o UJ CO if) if) o or o o < or o : 29. the Franc onia -Trempealeau contact at least 23$ feet and probably UOO feet lower. The St. Peter just above the Trempealeau has been altered to a quartzite breccia which crops out in the hill slope northeast of the barn. The distribution of the breccia suggests that it lies along a thrust fault which dips gently eastward and cuts through the lower part of the St. Peter sandstone. The breccia zone lies above the St, Peter outcrop south of the quarry. Origin . The Cambrian exposure here, discovered by Dr. A. C. Bevan in 1923, is attributed to three factors: (1) location on the upthrow side of a large pre-St. Peter fault, (2) location on the Oregon anticline, (3) deep erosion by Rock River. Correlatio n. Subsurface tracing has suggested that the Franconia formation is equivalent to the Davis formation of Missouri -and that the Trempealeau dolomite in Illinois corresponds to the Derby- Doe Run, Potosi, and Eminence formations of Missouri, listed in as- cending order. Although the Trempealeau formation in Wisconsin con- sists of dolomite, siltstone, and sandstone, the elastics grade south- ward into dolomite more than 200 feet thick in Illinois. The exposure here is believed to be equivalent to the basal Arcadia member of the Trempealeau formation in VJisconsLn, described by G. 0. Raasch in 1951, and to the Derby -Doe Run sequence in Missouri. 35.8 STOP SIGN - Junction with Illinois State Highway 6!u Turn left (cast) on 111. 6k. 36.1 Pccatonica, Glenwood, and St. Peter strata are exposed in the small isolated hill and cut bank on the left (north) side of the highway. The beds lie on the northern flank of the Oregon anticline, strike N. 50° W. and dip 11° n» E„ The normal N. 70° W, strike of the anticline here is deflected by a nearby northeastward-trending anticlinal cross fold. 36.3 The large quarry J mile north of the highway is locally operated for road metal, agricultural lint stone, concrete aggregate, and riprap for the Oregon dam. The face, about Uo feet high, exposes a sequence ranging from the upp^r part of the Grand Detour formation to the lower part of the Dunleith formation. The entire PI attevi lie -Galena sequence consists of dolomite in this area. The scarp in which the quarry has been opened is the north rim of the Oregon basin. 36.7 St. Peter sandstone, showing prominent cross-bedding and dipping gently north -northeastward, crops out in the east bank of the stream on the left (north) side of the highway. Small St. Peter exposures occur at intervals along the highway for the next 2 miles. 38.1* Turn right (south) on gravel road. 38.6 STOP 6 - ILLINOIAN DRIFT Road cuts, SE.J SE.J SE,J Sec. 1 (elongate), T. 23 N. , R. 10 E. , Ogle County (Oregon quadrangle). 30. Mileage Discussio n Leader: M. M. Leigh ton Illinoian till overlain by Ulinoian ice-ccntact gravels are exposed in cuts on both sides of the road. The gravels are believed to have been deposited in lakes cr streams between preglacial valley slopes and masses of stagnant wasting ice in the central, inner portion of the valley. Road cuts down the hill to the south show that the gravel mantles the surface of the till and probably represents successive de- posits along the margin of the ice as it melted away from the valley wall. Ice-contact gravel containing large boulders is exposed on the right (west) side of the road at the base of the cut. Sangamon weathering has oxidized the upper part of the gravel to a dark red- brown, has made it moderately clayey, and has leached it of carbonates to a depth of 7 feet. The total depth of leaching in Illinoian gravels normally is more than 10 feet, but here the top of the deposit has been lowered by recent sheet wash. The Oregon basin is visible to the south. 39.1 The low hills west of the road represent the ice-contact face of the Illinoian high-level gravel deposit seen at the last stop. The strongly lcbate face is characteristic and well developed. St. Peter sandstone crops out in the low stream bank to the left (east). 39»3 Cross Honey Creek. The low terrace on the south side of the creek con- sists of outwash from the Green River lobe of Shelbyville (Wisconsin) age (See fig. 7). The outwash forms a valley train along Kyte River (to the south) and along the lower part of its tributaries. 39.7 CA UTION ; Burlington railroad track (route of the Chicago-Minneapolis Zephyrs) at the hamlet of Honey Creek. Turn right (west) just south of tracks. 1*0. 2 Turn right (north), dropping down to Recent flood plain of Honey Creek. k0,5 Recross Burlington railroad track. J4O.7 Hill composed of Illinoian high-level gravel rises on the right (east). I1O.8 Illinoian gravels are exposed in the east bank of the stream on the left (south) side of the road a St. Peter sandstone crops out in the west bank. The gravels are at a lower elevation, have a well-defined but dissected terrace surface, and are better sorted and stratified than the higher deposits. They probably are later Illinoian gravels derived from the stream erosion of high-level deposits, and laid down on a valley flat or in a temporary lake marginal to the ice. A terrace of Wisconsin outwash, about 20 feet lower, is well developed at the mouth of the valley. iil.l Winding road crosses ridge composed of Illinoian ice-contact gravels. 31. Mil eage Ul.3 Hill to left (south), St. Peter sandstone surrounded by ice-contact gravels which are banked against the lower slopes of the bedrock hill. I4I.I1 Turn right (north )♦ il2.2 STOP SIGN t intersection with Illinois State Highway 6J4. Turn left (west) on 111. 61w 1*3.5 Cross Rock River and enter Oregon. il3.8 STOP SIGN at intersection of Illinois State Highways 2 and 6J4. in Oregon. Turn right (north) on 111. 2, which here is built on a valley- train terrace of Cary (Valparaiso) age, hhmS Highway descends to the Mankato terrace. hh*9 View of Black Hawk Statue across river to right (east). 1*6.6 Grand Detour dolomite in cut on left (west) side of road is broken into a series of miniature horsts and grabens by small faults striking northwestward. The dolomite adjacent to some of the faults shows drag- flowage. U6. 7 Cross Mud Creek. I46. 8 Turn left (west) on gravel road. U7.1 Turn left (west) on gravel road. U8.8 STOP 7 - MUD | CREEK FAULT - PLATTEVILIE AND GA LENA STRATA » Park and walk 0,3 mile south. Quarry on south side of Mud Creek and east side of abandoned road, NW.J SW.J SE,J Sec. 30, T. 2h N. , R. 10 E. , Ogle County (Oregon quadrangle ). Discussion Leader : J. S* Templet on. See figure lU. The quarry cuts across a monocline which dips very steeply northward and across a westward-striking fault with the downthrow on the north side. At the top of the valley slope, just south of the quarry, are a f ew . smal l outcrops of Nachusa dolomite. Steeply dipping Quimbys Mill, _®t&l^h&*n-, and St. James strata are exposed in the south and southwest faces; at the top of the southwest corner of the quarry they are nearly vertical. The Guttenberg formation is missing. At the bottom of the southwest corner Quimbys Mill beds are cut by open, horizontal tension cracks. Bedding surfaces in this sequence are polished and grooved by bedding -piano faulting. Some of the strata are brecciated. Green clay between the bedding surfaces in some places may represent fault gouge, but more probably is a solution product. 31 33. Mileage A fault extending from the southeast corner of the quarry to the middle of the west face has finely brecciated beds belonging to the Beecher, Eagle Point, Fairplay, and Mortimer members of the Dunleith formation and in the west face has brought Fairplay opposite St. James strata (see Columnar Section, fig. 3)» Some of the brecciated chert and dolomite has been recemented. The total downward displacement on the north side of the fold and fault is 100 feet within a horizontal distance of 200 feet. This structure lies on the north flank of the Oregon anticline and in- dicates that soite of the uplift was due to faulting. 50.3 Turn left (south) on gravel road. 50.8 STOP SI GN - Junction with Illinois State Highway 6U. Turn left (east) on 111. oli. 51.2 Turn right (south) on gravel read. 52.2 Intersection with township road. Continue straight ahead. Between this intersection and the Burlington railroad crossing, O.U mile farther south, shallow cuts on the east side of the road expose Illinoian till approaching gumbo til, overlain by Peorian loess. Farmdale loess has not been found in this area. Illinoian gumbotil veneered by Peorian loess underlies the flat upland north and west, 52.6 CAUTI ON: Burlington railroad crossing. Cub on northeast corner of crossing exposes Illinoian high-level terrace gravels banked against the north slope of the preglacial bedrock valley of Gale Creek. 52.7 Cross Gale Creek. 52.8 Illinoian ice-contact terrace gravels are extensively banked against the south valley slope of Gale Creek for more than 3 miles. The northern or ice-contact face of the terraces has a lobate f crm which is well shown on the Oregon topographic sheet. Numerous abandoned and active gravel pits, some having vertical faces UO feet high, are located in these terraces. The gravel is poorly sorted and bouldery and shows rapid lateral variation. $3«0 Illinoian high-level gravels capped by Peorian loess are exposed in the cut bank on the left (east) side of the road. 5U.5 STOP SIGN - Turn left (east) on county black -top road. Between this intersection and Stop 8 the hills along the road consist mainly of Illinoian high-level terrace gravels on the valley slopes of preglacial Gale Creek and its tributaries. 55.3 Good view of Oregon basin straight ahead. 3U. Turn right (south) on gravel road. Turn left (east) into pasture. STOP 8 - SANDW ICH FAULT ZONE .-'JTO PLATTBVILLE-GALENA STRATIGRAPH Y. Chicago, Burlington and Qui^oy railroad cut, NW»^ NW,ij SE.^ and NE.^ SW.£ Sec. 7, T. 23 N. , R. ~ E. , Ogle County (.O re go -ft quadrangle). Gtjtffl Discussion Leaders : H, B. Willman and J. S. Templet on. See figure 15> (3 pages). The major fault in the Sandwich fault zone is believed to lie OcU mile southwest of the bridge over the railroad tracks. Through- out its course the Sandwich fault zone lies just north of and parallel to the axis of the Ashton Arch (fig. 6) and in this vicinity has a downthrow of about 300 feet on its northern side* The faulting exposed here in the railroad cut lies parallel to the major fault and to the south limb of the Oregon anticline. It has a total downthrow on its southern side of 270 feet, and cuts beds ranging from Pecatonica to Wise Lake in age. Consequently the Oregon anticline here is separated from the Ashton Arch by a deep narrow graben* There are at least twenty closely spaced individual faults, mostly marked by breccia zones, in the cut. The largest, n^ar the west end of the cut, brings Quimbys Mill dolomite next to Wise Lake dolomite and has a downthrow on the south side of at least 130 feet. This faulting may continue northwestward and account for the sharp downward displacement on the southwestern side of the Oregon anticline at Mt. Morris (fig. 6). 55.9 Turn right (north) on gravel road and retrace route to county black-top highway. 56.1 STOP SIGN - Turn right (east) on county black -top road. From this point east to Gale Creek, Illinoian high-level gravels form prominent hills on the right (south) side of the road, 57*1 Cross Gale Creek* One-half mile south is the plant and former pit of the National Silica Company. The chief product is very finely ground silica derived from the St. Peter sandstone and used as pottery glaze. Much of the product in recent years has been shipped to the Krosge Pottery Works at Holland, Michigan, fcr use in the production of china sold in Kresge stores. The original pit has been abandoned because of the high iron-oxide content and high degree of cementation of the sand. Sand is now obtained from' a pit in St. Peter bluffs along Rock River, two miles southeast. 35 A o o 5 a (\> CO a CL O 3 .3 o > t- X - c (1) c o o u o J5B x O Q CO 3 U_ O o) j: S /> 9 cr O "in in r K.£ .OH 35C c O o en o i tz O Ul B o 'J U o 'J) or _ CO a UJ a. 8 I o 2 .5 O n O *: o ■o < LU (D O Z in _J or % 3 o GO — X tj_ H 2 3 O Z o »- o UJ en en (/> O cr o x-K UJ 36. M ileag e The sand is thoroughly washed to remove the very little clay and iron oxide content (generally less than 2 percent) and is ground to pass 325-mesh screens. The grinding is in ball mills which are lined with pre-Cambrian quartzite blocks from quarries at Rib Hill, near Wausau, Wisconsin, and which are partly filled with chert nodules from the Cretaceous chalk of Belgium. The nodules are found in large quanti- ties on North Sea beaches and commonly are brought to this country as ship ballast. After grinding, the sard is passed under a mignet to remove iron or steel particles which would burn to objectionable black flecks when the pottery is fired. During World War II the supply of Belgian chert nodules was cut off and quartzite blocks from Wausau and granite blocks from North Carolina were temporarily substitued. The quartzite blocks proved too brittle. The granite blocks were too soft and introduced too much feldspar and ferromagnesian material into the sand. 57.2 CAUTION : Cross Burlington railroad. For the next 1.3 miles the road is on Cary (Valparaiso) slackwater silt and clay. These sediments accumu- lated in ponded water in Galu Creek valley, which was dammed by the Valparaiso valley train in Rock River valley. The slackwater material forms the floor of the Oregon basin and is partly underlain by Oneota and Trempealeau dolomite. 58.5 A slight eastward rise in the valley floor marks the boundary between Valparaiso slackwater silt to the west and the Valparaiso valley train (gravel and sand) to the east. 58.7 STOP SIGN - Junction of county black-top road with Illinois State High- way 2 at the south edge of Oregon. Turn right (south) on 111. 2. 58.9 Cross Burlington railroad (Chicago-Minneapolis line) on overhead viaduct. There is a good view of the Oregon basin on each side. 60.2 A pit in the sand and gravel of the Mankato valley train is on the left (east). 60.3 On the right (west) is the Devil 's Backbone , a prominent westward- trending ridge of St. Peter sandstone capped by Glenwood strata and Pecatonica dolomite. This ridge forms the south wall of the Oregon basin west of Rock River. Its summit has an elevation of 905 feet, represents a remnant of the Lancaster peneplain, and is the highest point in the Dixon quadrangle. Although cross beds in the St. Peter sandstone dip north, the actual dip of the strata is south. 60.5 National Silica Company Pit on right (west) in St. Peter sandstone. Sand is trucked from here to the plant, two miles northwestward. 61.6 Oneota dolomite crops out in cut bank on right (west). 61.7 Drive slowly for car -window geology. 37. Mileage A large fault is marked by a broad breccia zone in the road cut on the right (west). This fault (look for sign) lies within the graben between the Ashton arch and the Oregon anticline and is part of the Sandwich fault zone. The fault brings Now Richmond sandstone and Shakopee dolomite on the south against the older Onoota dolomite on the north. The breccia zone is mainly in the Cneota formation. Cross faulting has exposed a few blocks believed to be Trempealeau dolomite near the base of the cut, south of the main fault. St. Peter sandstone with a basal chert conglomerate rests unconformably on beds ranging from Shakopee to Oneota in age and cuts down to road level at the south end of the exposure. 62.5 Straight ahead is Castle Rock , a prominent erosion remnant of St. Peter sandstone and a well-known landmark. A fine view of Rock River is available from the top of the rock. 63. h St. Peter sandstone is well exposed in two deep, steep-walled cuts along the highway. From this point southward to Grand Dotour the highway mainly is on Wisconsin valley-train terraces. 68.2 Village of Grand Detour. 68.9 Cross Rock River. For the next half mile, there are several exposures of St. Peter sandstone in cuts along the highway. 69.9 Small exposure in cut on right (west) side of highway shows St. Peter sandstone overlain by the Kingdom sandstone and Daysville dolomite of the Glenwood subgroup. The relatively resistant Daysville dolomite forms a bench in the middle of the hill slope. 70.0 Pecatonica dolomite capping the weaker Harmony Hill shale and Loughridge sandstone forms a second bench at the top of the hill, although the for- mations are concealed by slumped Peorian loess and by a heavy cover of grass. 71. h Small sink-holes are present in the Mifflin limestone on both sides of the highway. The cover of Illinoian till and Poorian loess is very thin and patchy on this portion of the upland surface. 72.U Dixon city limits. Mifflin limestone crops out in low cuts along the highway. Medusa Portland Conent Plant is on the right (north). 73*5 Turn left (south) at Standard Service Station, continuing on Illinois State Highway 2. Nachusa dolomite and limestone is exposed in cliff at left. Nachusa type locality is in abandoned quarry on left (east) side of road, just south of the turn. 7U.2 STOP LIGHT - Intersection of Illinois State Highway 2 with State Highway 26 and with U, S, Highways Alt. 30 and 52 at northwest corner of Court House square. Mileage 38. NOTIC ES; Parking meters in Dixon operate until 9 P. M* on Saturday nights. Cars should be serviced tonight, if needed, because few filling stations will be open early Sunday morning. The annual dinner will be held this evening at 7 P. M. at the Loveland Community House (see map of Dixon, fig. 2). Restaurants will be open at 6:30 Sunday morning. Cars should leave Dixon not later than 8:00 A. M, in order to arrive at Stop 9, 19 miles northeastward, by 8:30 A, M. END OF FIRST DAY'S TRIP 39* Mileage ITINERARY FOR SUNDAY, OCTOBER 12 (SECOND DAY) (Columbus Day) The conference will assemble at Stop 9, 19 miles northeast of Dixon at 8:30 A. M» The log from the Nachusa Hotel in Dixon to Stop 9 is given below. Those staying at White Pines State Park, at Oregon, or at Grand Detour will find the shortest route to Stop 9 via Oregon as follows: LOG STARTING AT OREGON 0.0 Intersection of Illinois State Highways 2 and 61| in Oregon. Drive east on 111. 6iu 0«3 Cross Rock River 0,8 Turn right (south) on county black -top road, leaving 111. 6lu 1.1 CAUTION; Cross Burlington railroad tracks (Chicago -Minneapolis line). 2.3 Cross Kyte River. 2.6 Enter village of Daysfille. 2.75 Angle left (southeast) on village street. 2.95 Angle left (east) on county gravel road. U.O Turn right (south) on gravel road in hamlet of Watertown. House on southwest corner is enclosed by a stone fence built of glacial erratics. 5.0 Turn left (east). 5*1 Continue straight ahead (east) at school house. 6.8 Turn south (right). 7.U Jog left (east). 7.6 Turn left (east). 7.7 Turn right (south). 7.9 Turn right (west) into farm lane at mailbox marked * f H. J % Campbell." 8.5 Park in barnyard north of house. STOP 9. ); , ■ 1 i: : : Uo. Mileage LOG STARTING AT DIXON 0.0 Drive south on U. S. Highways Alt. 30 and 52 and Illinois State Highway 26 on west side of Court House square. Nachusa Hotel on right, Lee County Court House on left* 0.3 STOP SIGN - Junction of U* Si Alt. 30 and 52 with 111. 26. Turn left (east) on U. S« Highways Ait* 30 and 52. 0.6 Junction of U. S. Alt. 30 and 52. Turn left (east) on U.. S. Highway Alt. 30. 5*0 Nachusa Lutheran Home for boys on right (south). 8.9 Cross Franklin Creek. Shakopee dolomite is exposed in abandoned quarry on east bank of creek, about 500 feet north of highway.. The dolomite is argillaceous, sLlty, sandy, locally glau- conitic, tuff, chalky, dense, and thin- to medium-bedded. It contains some layers of intraf or national conglomerate, nodules of oolitic chert, and small algal domes. Many bedding surfaces exhibit ripple marks, mud cracks, and the rare cubic impressions of salt crystals. Layers of dolomitic sandstone and green cr maroon shale arc common. Rapid lateral and vertical lithologic change is characteristic* The ledges between the creek and the quarry floor carry Lingulepsis acuminata (Conrad) and Orospira elevata Cullisom They are similar in lithologyj fauna, and stratigraphic position above the New Richmond (Roubidoux) sandstone to the Rich Fountain formation of the Jeferson City group in Missouri, described by J. S, Cullison in ±9hk* 9.6 Enter Franklin Grove, population 7Ul. Turn left (north) on county black-top road at Shell Service Station. 15.1 Turn right (east) on gravel road. 16.1 Turn left (north). 16.3 Turn right (east). Oneota dolomite is poorly exposed in shallow ditch on right side of curve. 17.0 Trempealeau dolomite is exposed in low cut bank on left (north) side of road. 17.7 Junction with gravel road leading south. Washington Grove Cemetery on left, church on right. Continue straight ahead (east). 17.8 Turn left (north) on gravel road at foot of hill, and cross creek. 18.6 Turn left (west) into private lareat mailbox marked '»H. J, Campbell." 19.1 Cross creek and park in barnyard on north side of house. 111. Mileage STOP 9 - QUARRIES IN ONSOTA AND PLATTEVILLE STRATA; SANDWICH FAULT. Quarry in Oneota dolomite, N. lino NE.J SW»J NE.J Soc. 31 , T. 23 N. , R. 11 E. , Ogle County (Dixon quadrangle). Quarry in Platteville dolomite in NE.^ NW.^- NE.^ of same section, 800 feet north of Oneota quarry. Discussion Leaders: H, B, Willman and J. S, Temple ton. See figure 16 . Twelve feet of deeply weathered Oneota dolomite is exposed in the small quarry on the south bank of the creek, just west of the barn. Other outcrops occur in the creek bank and in tributary ravines farther west. The dolomite is buff, coarsely crystalline, porous, and thin-bedded, and contains thick bands of white oolitic chert. Although the beds are jointed, they are essentially level. In the quarry 800 feet northward lower Platteville strata strike N* 85° W. and dip up to 10° N, Although the base of the Platte- ville exposure has nearly the same elevation as the top of the Oneota exposure to the south, the normal stratigraphic interval between the two points is estimated to be approximately 350 feet. The Sandwich fault, with the dewnthrow on the north side, is believed to pa ss between the two quarries. The northward dip of' the Plattoville strata reflects updrag adjacent to the fault, An alternate but less likely hypothesis is that the Ashton arch was folded and truncated to about the level of the Oneota exposure in pre -St. Peter time, that the St. Peter -Platteville sequence was deposited directly on the Oneota and that renewed uplift along the Ashton arch imparted a northward dip to the Platteville strata. The Establishment-Boa rman sequence is poorly exposed. The corrosion (solution) surface at top of Pecatonica formation has been traced from Minneapolis, Minnesota, to LaSalle, Illinois, although it is missing in a few places, as at Dixon North (Stop 2). In southern Illinois and eastern Missouri it is replaced by an undulatory scour surface. The distinction between the New Glarus and Dane members of the Pecatonica formation is weak here because the Dane strata are ab- normally pure. Turn around and return east to lam entrance, 19.6 Turn right (south) on gravel road. 20. h Turn right (west). 20.6 Washington Grove Cemetery on right, church on left. Turn left (south) on gravel road just beyond church. . vz Z) o rr GRAND DETOUR FM. DEMENT MBR. 2'0" BRITON MBR. 10' 0" Dolomite, pure, nonshaly, weathered to thin beds, f olomife, argillaceous, moderate- ly shaly, thin- bedded , 2 " calcareous shale at base. HAZELWOOD MBR. 6' 8" ^"TSTABU^MENT MBR Dolomite, pure, nonshnly ? nnedium- bedded ■, prominent 6 "bed at base. / / / - BRICHgQEYJMBR. T.ite, moderately argillaceous and shaly, thin- bedded. Dolomite, / / ( "/ BOARMAN MBR. * , \ 3' 3 " ench MEDUSA MBR Co io mite slightly argi llaceous,non- sha ly , tn in - to m e dium- be dded. L olomite, argi I lace ous, thin bedded, with green shale partings; ver j fossiliferous. D o I o m. i r e , i n medium beds with weak wavy shale partings? few chert nodules in lower part • strong ferruginous pitted corrosion surface at top. NEW GLARUS MBR 3' 2" D lomite , pure, cherty, thick bedde d. DANE MBR. I4'3" Dolomite, moderately argil- laceous next to bedding sur- faces, pure elsewhe r e , che r ty, thick-bedded; strong bedding break at top- Quarry floor FIG. 16 STO P 9 ii3. Mileage 21.1 Operating quarry in Trempealeau dolomite on the left (east) — see below. 21.5 STOP 10 - PRAIRIE STAR - TREMPEALEAU (POTOSI) DOLOMITE. Quarry just northeast of Prairie Star School, SW.J SE.J Sec. 5, T. 22 N. , R. 11 E. , Ogle County (Dixon quadrangle). Discussion Leader : J» S, Tern pic ton The quarry exposes 18 feet of dolomite which is pure, buff, finely crystalline, vuggy, and thick-bedded to massivo. The vugs are lined with white to pink quartz crystals, a characteristic feature im- portant in subsurface identification. Some beds, not exposed here, are glauconitic. The massive dolomite in the central part of the west quarry face is a reef core surrounded by ruef-flank beds which dip away from the core. Most of the core probably was made of dome -shaped algal growths ( Cryptozoon ) which since have been largely destroyed by dolomi- tization. The bedding surfaces are marked by deeply incised labyrin- thine ridges and furrows. The dolomite contains a sparse fauna which has been identified by G % 0. Raasch. It consists chiefly of the gastro- pods Hypseloconus and Scaevogyra and the trilobites Plethomotopus and Saukiclla sp. cf. indenta Ulrich and Rcsser. These beds have been traced in subsurface into the Potosi dolomite of Missouri, to which thuy are very similar in lithology, fauna, and stratigraphic position. They also are believed to be equi- valent to the St. Lawrence dolomite of Wisconsin. They are overlain in subsurface by cherty sandy gray dolomite without drusy quartz, which is correlated with the Eminence formation of Missouri and with the Lodi- Jordan -Sunset Point (Madison) clastic sequence of Wisconsin. The Trempealeau dolomite in the quarry one-haLf mile north- ward is greatly shattered by the combined effects of jointing, cave- collapse, weathering, and intensive blasting. 22.6 Turn left (east) on gravel road. 22.7 The low ridge on the horizon at the right (south) is composed of Trem- pealeau and Oneota dolomites on the crest of the .ashton arch. The ridge runs east-west through the town of Ashton, also visible on the horizon. 2U.6 STOP SIG N - Junction with U, S, Highway Alt. 30. Turn right (south) on U. S. Alt. 30. 25.6 Trempealeau dolomite is visible in the quarry to the left (east), on the south side of a gravel road. uu- Mileage 26.6 Oneota dolomite is exposed in quarries to the left (east) on both sides of a gravel read. A fauna typical of the Gasconade formation of Missouri was recovered here. 26.7 Oneota dolomite is exposed in a low road bank on the left (cast). 26*9 City limits of Ashton, population 913. 27.0 Quarry in Oneota dolomite to right (west), behind American Legion clubhouse. 27.1 CAUT ION - Straight ahead on county black -top road, leaving U. S % Alt. 30 at westward curve in highway. Cross Chicago and Northwestern Railway tracks (main line, Chicago to Omaha), and leave ashton. 27.6 Turn left (east). 28.1 Turn right (south). A low rock ridge lies to the east. 29.1 Read jogs at township line. 30.0 STOP SIGN - at intersection with county road. Turn left (east) on black -top road. 30.2 STOP 11 - ILLINOIAN ,iND WISCONSIN DRIFT-SHEETS, N. line NW.J NW.J Sec. 11, T. 21 N. , R. 11 E. , Lee County. Discussion Leader t M, M, Leighton The boundary between the Illinoian till sheet to thu west and the Wisconsin Shelbyville till sheet to the east passes just east of the road intersection, although there is no topographic feature to indicate this fact. The boundary of the area covered by Wisconsin ice is commonly marked by a prominent moraine south of the Green River Lobe (fig. 7), but in this region it usually can be mapped only by determining the depth of leaching in auger borings. The relatively great depth of leaching on the Illinoian drift (ll§r feet here) contrasts strikingly with the much shallower depth of leaching on the early Wisconsin Shelbyville drift (1*J feet). Samples of drift from auger borings in this vicinity have been laid beside the road near the highway intersection for inspection by the parly. One set of samples was taken from a boring one mile west- ward, where the following sequence typical of the Illinoian drift was logged (M % M. Leighton, 1922) i . J.. ■■■,, I -J , ". .VI. .,.:-,-, i I . . *. ( ■ i< 15. Mileage Ft. In. 1 I* 1 2 6 3 6 12 Soil (Recent) Loess, leached (Tazewell) Sand, gravelly, leached (Shclbyville out wash) Gumbotil (Sangamon weathering of Illinoian till) 2 Till, leached (Illinoian) Till, calcareous " The second set of samples was taken from a boring 0.2 mile east of the intersection and shows a typical sequence on Wisconsin drift (M. M. Leighton, 1922). Ft. In. Soil 1 3 Loess, leached (Tazewell) 2 3 Till, leached (Shelbyville) 9 Till, calcareous " _!__ _9_ 6 33.3 Bloomington moraine on skyline to right (south) with outwash plain in foreground. Both of these features are best seen from the summit of the rock ridge at Stop 12. 36.5 STOP SIGN ; Intersection with U. S. Highway 51. Continue straight a c r oss hig hway , 36.9 Turn right (south) on gravel lane into quarry of Stone Ridge Limestone Company. Park in lot beside company buildings at head of ramp leading to quarry. U0,1 STOP 12 - ( last stop ) - ROCHELLE SOUTH - TREMPE ALEAU (POTO SI), GUNTER aND onsota FORMATIONS* ~ Quarry on N. line NE»J SE.J NE.^ Sec. 26, T. 39 N. , R. IE., Lee County. Discussion Lead er: H* B„ Willman See figure 17. y£ lu in l- ^ CO oc >- UJ A \ 1 ONEOTA FM. 31' 0" Dolomil gray line, al gi parti bedd some V / \ e, cherty (oolitic), partly glauconitic, to light brown, coarsely crystal - porous, thick-bedded, with occasion -een clay streaks-, basal 12 feet is y finely crystalline and medium - /A A ed, and has shale partings and bouldery algal masses. 2: /* ICIA ian A / ORDOV Canad / 4 /| /* / A \ GUNTER FM. \ I0'3" Dole g t loor Pit / A )mite, mostly argillaceous, silty, lauconitic, micaceous, and cherty Dolitic), greenish- gray, chalky, and A / / / A / / A / / / A hin - bedded. A/ / _^^— Quarry f around A A/ ^ ^ —Water level >EALEAU SI) FM (12 feet water) or of pit Dolomite, pure, buff to light red- brown , finely crystalline, BRIA 3roixiar 4? A TREMF (POTO 1 I6'0" ~\ under -J—Floi massive, with quartz druses and thick, partly oolitic chert bands; top undulatory. < CO O / A c5 FIG. 17 - STOP 12 Mileage U7. The Oneota-Gunter contact appears conformable and transition- al* The basal 12 feet of the Oneota partly resembles the Gunter, and an Onoota-like bed occurs in the middle of the Gunter. The contact is drawn at the horizon of maximum lithologic change. Recognition of the Gunter formation is based on similarities in lithology, stratigraphic position, and stratigraphic relations, and upon subsurface tracing of the unit through western Illinois to Missouri. Normally the Gunter of Illinois contains shale and sandstone beds, but they are absent here. Gunter equivalents also have been traced into southern Wisconsin. The Oneota strata probably are equivalent to the lower part of tho Gasconade formation in Missouri (Van Buren faunal zone). The Gunter rests unco nfoim ably on the Trempealeau formation. Upper Trempealeau (Eminence) strata wedge out northward against the flanks of the Ashton arch so that here, on top of the arch, the Gunter rests on lower Trempealeau (Potosi) beds. You arc now located 1/2 mile east of U. S. Highway 51* 6 miles south of Rochelle, 21 miles east of Dixon, 23 miles north of Mendota, and 23 miles west of DeKalb. Wo wish you a safe journey home .' END OF CONFERENCE