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  • BEDROCK GEOLOGY MAP - ISGSbedrock, but some glacially derived cobbles are basalt, granite, and metamorphic rocks weathered from diamicton that occurs above the bedrock. Small, reworked
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George H. Ryan, Governor Department of Natural Resources Brent Manning, Director ILLINOIS STATE GEOLOGICAL SURVEY Illinois Geologic Quadrangle Map: IGQ Grafton-BG 2002 William W. Shilts, Chief Digital base map compiled at the Illinois State Geological Survey (ISGS) from digital line graphs (DLG) provided by the U.S. Geological Survey 1927 North American Datum is shown by dashed corner ticks 1983 North American Datum Projection and 1,000-meter ticks Universal Transverse Mercator grid, zone 15, 10,000-foot ticks Original base map compiled from photogrammetric methods from 1952 photography. Field checked 1954 and updated 1995 Buildings and structures are omitted in Grafton, Chautauqua, and gray-colored areas 1 Nutwood 2 Otterville 3 Jerseyville South 4 Brussels 5 Elsah 6 Kampville 1 2 3 5 4 6 7 8 ADJOINING 7.5-MINUTE QUADRANGLES NATIONAL GEODETICVERTICAL DATUM OF 1929 Contour Interval 20 Feet BEDROCK GEOLOGY MAP Grafton Quadrangle (Illinois Portion), Jersey and Calhoun Counties, Illinois F. Brett Denny and Joseph A. Devera 700 500 500 500 600 600 600 600 600 700 700 500 700 700 600 700 600 700 700 500 700 700 500 700 500 700 700 800 600 800 500 600 600 700 800 800 800 800 800 800 800 700 800 600 800 800 800 600 700 600 440 440 420 440 440 440 AN A Orchard Farm Mississippi River Deer Plain Ferry 740 740 700 720 680 700 720 660 640 620 600 580 560 560 540 520 500 480 460 440 420 400 380 360 Deer Lick Anticline A. Alluvium: B. St. Louis Limestone: C. Salem Limestone: D. Warsaw Shale: E. Burlington and Keokuk Limestone: F. Fern Glen Formation: G. Meppen Limestone: H. Chouteau Limestone I. Hannibal Shale: J. Glen Park Formation: K. Cedar Valley Limestone: L. Joliet Formation: M. Kankakee Formation: N. Edgewood Limestone: O. Maquoketa Formation: P. Kimmswick Limestone–Trenton Limestone in the subsurface: Q. Decorah Formation: R. Plattin Limestone: c . The upland sediments are composed of a mixture of clay, silt, sand, gravel, and cobbles. The clay, silt, and fine sand fraction is colluvium derived from loessal deposits that thickly mantle the upland areas. Most of the gravel originated from the underlying bedrock, but some glacially derived cobbles are basalt, granite, and metamorphic rocks weathered from diamicton that occurs above the bedrock. Small, reworked geodes filled with calcite and quartz crystals were observed. These geodes weather out of the Mississippian bedrock and are more abundant in the western half of the quadrangle. Alluvium in the bottomland is composed of a thick sequence of clay, silts, sand, and gravel that ranges from Pleistocene to Holocene. Slack-water lake deposits composed of gray, laminated silt with wood fragments were observed in some of the valleys at elevations near 450 feet (Grimley 1999). . Light gray to medium gray dense lime- mudstone with fossil wackestones. Part of the unit contains quartz sand and subangular limestone breccia clasts. Brecciation is attributed to ancient karstification of gypsum and anhydrite (Saxby and Lamar 1957). Oolitic grainstones, greenish oncolitic packstones, peloidal grainstones, stromatolitic boundstones, and carbonate intraclastic conglomerates make up a highly variable mix of microfacies. , a colonial coral, occurs in the upper part of the basal portion of this formation. is widespread near the base of the unit. Yellowish dolostone beds are also present in this formation. Gray to dark gray chert occurs as nodules and stringers. Siltstones are calcareous and greenish. The shales are greenish gray and reddish brown, calcareous, soft, and non-fissile. This unit was only exposed along a fault slice in the extreme southwest corner of the Illinois portion of the quadrangle. . Limestones are tan-brown to light gray and contain laminated tidallites, wackestones to grainstones composed of rounded and broken fossils and coated grains. Bedding styles range from tabular to undulatory. Cross-beds are present in grainstone facies. The unit has a dirty gray-brown grainy appearance. The diagnostic character of this formation is alternating beds of laminated, fine-grained (calcisiltite) facies with coarse bioclastic, peloidal to oolitic grains in shoaling- upward cycles. Dolomites are brown and have moldic porosity. Cherts are light gray and may be bioclastic and weather with a porous rind. Cherts occur between grainstones and laminated beds as elliptical nodules containing concentric rings that spall off like egg shells when weathered. Siltstones are brown to light gray and thinly bedded, typically less than 1 inch thick. Oolitic beds are rare. The foraminifera, , is an index fossil for this unit. Other microfossils include calcareous algae, conodonts, and ostracodes. Fossil invertebrates include spiriferid and productid brachiopods, rugose corals, conularids, and crinoids. Ramose, fenestrate, encrusting, and bifoliate bryozoans are also present. The contact with the underlying unit is gradational. . Medium-gray, crinoidal, bryozoan wackestones and packstones that contain a few brachiopods. In the lime- mudstone beds sp. are preserved with coil and fronds attached. Dolostone beds are gray-brown, thinly bedded, and contain chlorite-rich shale clasts with some small quartz geodes. The upper half of the unit is dominated by shaly limestone and dolostone beds. The lower half contains bluish gray mudstones up to 20 feet thick interbedded with thin lime- mudstones. Conularids and gastropods occur in the shaly portion of this unit. Siltstones are calcareous and fossiliferous and thinly bedded in the lower part. Quartz geodes are common in the shaly sequences. The geodes weather out and are very common in the drainages in the lower portion of the unit. The basal contact is poorly exposed but thought to be sharp and conformable with the underlying carbonate beds. . Light gray to white crinoidal grainstones dominate and are interbedded with nodular and bedded light gray to black cherts. The cherts are white when weathered, and some have bioclasts of crinoids and brachiopods. Sandy limestones weather light brown, are cross-bedded, and contain brachiopod and crinoid molds. The unit is characterized by alternating layers of light gray to white crinoidal grainstones with beds of argillaceous and sandy limestones. This cyclic sequence of crinoidal limestone over sandy cross-bedded limestone is common in the lower part of the unit. Large spirifers are common along with crinoids, bryozoans, and corals. Siltstones are dark gray with a greenish tint and are calcareous. Calcite and quartz-filled vugs from 0.5 to 2 inches in diameter were observed. The unit is weathered on the upland surface where cherty residuum is 20 feet thick. The unit is conformable with the underlying unit. . On the eastern side of the Illinois portion of the quadrangle, the limestone is greenish gray, thin-bedded, and argillaceous; it contains small calcite geodes and crinoid stems. Green and red shaly calcareous siltstones are diagnostic and are well exposed on the river bluffs near Chautauqua, Illinois. The cherts are greenish gray, nodular, and fossiliferous. In Dagett Hollow and westward, the unit is dominantly thin, irregularly bedded, lime mudstone with cherty, crinoidal wackestone and packstone facies; these facies are indistinguishable from the lower part of the overlying unit E. Yellowish dolostone facies are also present. The basal part is gradational with underlying formation. . Light gray to tan, massive dolomite limestone, containing small (0.5 to 1.0 inch diameter) calcite geodes, light gray chert nodules, and locally calcareous siltstones. The unit is less than 12 feet thick and normally forms a small resistant weathered face that is fairly well exposed in most drainages. A minor unconformity exists between this unit and the underlying formation. On the river bluff just west of Chatauqua, an angular relationship between the underlying unit and this formation can be observed (fig. 1). : . Light brown to greenish gray irregular to wavy, thin beds of lime mudstone with thin beds of silty dolostone. Calcite geodes with diameters from 0.5 to 2 inches are common. Some of the calcite geodes are replaced with quartz. Chert nodules are locally abundant and typically are dark gray with light gray rims. Crinoidal wackestones containing fenestrate bryozoans and brachiopods occur in southwest dipping beds near Chatauqua. The unit appears to be gradational with the underlying unit. . The upper portion may interfinger with the overlying argillaceous lime- stone. Non-fossiliferous, gray, fissile, silty shale to laminated siltstone having brown iron oxide and manganese on fractures of weathered surfaces. The lithology is dominated by a soft, greenish to light gray mudstone, silty at base and fines upward to a non-fissile mudstone that fractures conchoidally. A thin, black, silty shale near the base of the unit (NE1/4, NE 1/4) Section 1, T6N, R13W, had a very strong petroliferous odor. Typically, the mudstone is not well exposed; however, good sections were observed at the head of Graham, Dagett, Distillery, and Jerseyville hollows. On the western side of the quadrangle, this unit is conformable with the underlying unit. . Identified only in the eastern portion of the quadrangle. The limestone is poorly exposed and was only identified at two locations. At one location it was composed of an argillaceous lithographic limestone with small concretions (1/8 inch diameter) of pyrite and some glauconite. At the second location it was composed of a fossiliferous and oolitic limestone. The fossils were mostly chonetid and spiriferid brachiopods with crinoid fragments in an oolitic grainstone. The limestone interfingers with the overlying shales. It is unconformable with the underlying unit. . Thin and discontinuous fossil packstone with quartz sand. The lowest unit is a brownish gray sandstone overlain by fossiliferous and sometimes argillaceous limestone. It is gray where fresh and weathers to a brown tint and contains sp. and sp. brachiopods, rugose corals, and platycerid gastropods. In the quarry east of Grafton, an arthrodire tooth was found in the sandy limestone. The sandy limestone is unconformable with and may downcut several feet into the underlying formation. . The dolostone is yellowish brown to buff gray and has a pitted weathered surface; sucrosic texture with molds of fossils are common. The upper part of the dolostone is truncated by overlying strata. Bedding planes are flat to wavy in places, and beds are typically several feet thick but can be thinly bedded. In Dagett Hollow the upper surface contains polygonal mud cracks. Chert occurs as nodules sporadically throughout the unit. The thin shales have a greenish gray tint. The trilobite is common in the quarries east of Grafton. A cheirurid trilobite was also collected from the upper part of the dolostone. Dolomitization of this and lower formations within the Silurian makes mapping the Silurian units separately difficult. This unit is unconformable with the underlying units. . The dolostone is yellowish brown to buff gray and has a characteristic pitted weathered surface. Dolostone beds range from thick to thin. Bedding planes are flat to wavy in places and are separated by thin green clay laminae. Chert occurs as nodules sporadically throughout the unit. Shales have a greenish gray tint. Glauconite is present within this formation. Fossils include brachiopod molds, straight cepholopods, and trilobites. This unit is unconformable with the underlying units in some places. . The dolostone is brown to buff gray. Beds are thick to thin, argillaceous, and sandy in places. Chert occurs as nodules sporadically throughout the unit. Shales have a greenish gray tint. Glauconite was present in a few of the beds, and few fossils were observed. This unit is unconformable with the underlying units. . This unit is poorly exposed and forms gentle hill slopes that are well vegetated. The lower part of the formation is calcareous and grades upward into bluish green, thin calcareous siltstones interbedded with bluish gray mudstones. The upper part is shaly buff-gray to greenish gray and has interlaminated silts and shales. A thin black shale having phosphatic nodules, fossil fragments, and abundant disseminated pyrite was identified near the base of the unit. This black shale was only observed at one location in Section 13 (SW, NE) T6N, R13W. The base of this formation was not observed, but drill logs indicate that it is unconformable with the underlying units. . White to gray, coarsely crinoidal grainstone is the dominant facies in this formation. Other fossils include sp., sp , (trilobites), brachiopods, and gastropods that are commonly broken in the cross-bedded coarse bioclastics of the formation. Shales are calcareous and may contain pyrite. Cherts are not very common and are white with slight yellow tones. When cracked, the limestones have a faint petroliferous odor. The basal contact is a distinct hardground omission surface. . Light brownish to greenish limestone or lime mudstone interbedded with organic-rich reddish brown shales. The cherts are dark gray, and the dominant fossils are strophominid brachiopods. . Light brown to chocolate brown sublithographic limestone with alternating fossiliferous shales and sandy limestones near the base. lay, silt, sand, gravel, and cobble limestone, limestone breccia, siltstone, and shale Acrocyathus floriformis A. floriformis limestone, dolomite, chert, and siltstone Globoedothyra baileyi dolomitic limestone, siltstone, and mudstone Archimedes limestone, siltstone, and shale limestone, siltstone, and shale dolomitic limestone limestone and siltstone shale, mudstone, and siltstone limestone limestone and sandstone Mucrospirifer Paraspirifer dolostone and minor shale Sthenarocalymene celebra dolostone and shale dolostone and minor shale dolostone, siltstone, mudstone Subsurface only (described from drill logs and reports). limestone, dolostone, and minor shale Receptaculites Illaenus . Isotelus gigas limestone and shale limestone, dolostone, and shale GRAPHIC COLUMN THICKNESS (feet) DESCRIPTION UNIT FORMATION SERIES SYSTEM QUATERNARY Holocene Pleistocene MISSISSIPPIAN Valmeyeran Description GROUP OR SUBGROUP DEVONIAN Erian Kinderhookian Mammoth Cave Group SILURIAN ORDOVICIAN Mohawkian A B C D E F G H I J K O P M L N Q R Cincinnatian DSu DSu DSu Om DSu Om Om Mkb Mchm Mmch Qu Om Mu DSu Mmch Ok Od Op Op Ok DSu 0 800 400 600 200 Feet 0 800 400 600 200 Feet Scale 1:24,000 Vertical exaggeration 2X A A ' Deer Lick Anticline 200 –200 Qu Om Ok Op Od Od Mkb Older Rocks Illinois River Mmch Cross Section A-A Looking Northwest ¢ Economic Geology of the Grafton Quadrangle Structural Geology of the Grafton Quadrangle Stone Oil Sand and Gravel Several quarries once mined Silurian dolomites in the quadrangle. Currently, none of these operations are active. According to local residents, most of the quarries were operated for local supply of aggregate and building stone. The Burlington and Keokuk Formations in the Grafton area are nearly identical in lithologic character and were mapped as a single unit. Both units are composed in part of calcium-rich limestone. Portions of these units contain white crinoidal grainstones to packstones, which commonly are high in calcium carbonate. Hindering the quarrying in this unit are the cherty intervals located above and below the high-calcium zones. Relatively thick chert-free beds of economically important limestone are present locally. The chance for economic oil production in this quadrangle is marginal because of the shallow depth to the pay zones along the anticlines and because of faulting in the area along the Cap au Grès. Neverthless, t Sand and gravel are available in the alluvial deposits of the Illinois and Mississippi Rivers (see Grimley 1999). The major structural feature of the quadrangle is the Cap au Grès Faulted Flexure (Keyes 1894). The Cap au Grès is the southeastern extension of the Lincoln Fold, which extends over 165 miles into northeast Missouri (Nelson 1995). The axis of the Lincoln Fold follows a general northwesterly trend but turns easterly at its southernmost exposures. The south-easternmost portion of this structure in Missouri and Illinois is called the Cap au Grès. Two oil tests have been drilled in the quadrangle. According to an oil well report written by consulting geologist Lawrence Bengal, the first well had a show of oil, and the second well drilled in 1984 (Section 2, T6N, R12W) was interpreted by the geologist as intersecting a fault and repeating the Devonian and Silurian units (Bengal 1984). This interpretation would require at least 150 feet of vertical displacement. No field evidence to support a fault of this size was identified. he shales and the limestone of the Ordovician Decorah contain hydrocarbons. Qualitative distillation tests in the area have reported the Decorah to produce between 15 to 25 gallons of crude oil per ton (Rubey 1952). In this quadrangle, the Cap au Grès is a faulted monocline with dips averaging less than 30° to the southwest and less than 4° to the northeast. The faulted blocks strike N80° W and dip between 40° to 80° to the south. The fault in this quadrangle juxtaposes Silurian age dolomites with Mississippian carbonates. Geologic reconstruction of the flexure indicates as much as 950 feet of vertical displacement may be present along this fault zone at the Deer Plain Ferry location. Evidence for the structure can be observed in road cuts along Illinois Highway 100 just west of Graham Hollow north of the Deer Plain Ferry landing. At this location the Mississippian St. Louis Limestone dips to the south up to 70°. Along the bluffs west of Grafton, several large blocks of Silurian dolomite are exposed that are interpreted to be rotational slumps. Several more slump blocks were observed along a drainage on the west side of Graham Hollow. The basal failure plane of these slumps occurs in the underlying Maquoketa Shale. The failure plane was not observed because of the lack of bedrock exposures of the Maquoketa in the immediate area of the slump blocks. Rubey (1952) mapped the Hardin and Brussels 15-minute quadrangles to the west of the Grafton Quadrangle. He identified an oval-shaped uplift located in Deer Lick Hollow just west of the Grafton Quadrangle, which he named the Deer Lick Dome. We traced this feature into the Grafton Quadrangle and determined that it was more accurately described as a plunging anticline. The Deer Lick Anticline is closely related to the Dome described by Rubey and may be considered the eastern limit of the Deer Lick Dome. A second anticline was identified on the structure contours to the northeast of the Deer Lick Anticline. This second anticline roughly parallels the Deer Lick Anticline but the dips of both limbs are less than 4°. This anticline also plunges to the southeast where it is concealed by the alluvial sediments of the Illinois and Mississippi Rivers. The Florissant Dome observed on the (Harrison 1997) appears to be a continua- tion of the second unnamed anticline in the Grafton Quadrangle. Two northeasterly trending strike-slip faults were identified in the eastern half of the quadrangle. The first was located in the bluff just east of Grafton. The fault zone was 10 feet wide and contained breccia fragments, gouge, and secondary calcite veinlets. No vertical offset could be observed in the Silurian dolomite. The fractures were nearly vertical with smooth wavy mullion-like planes, which had general trends of N50° E. The direction of movement was probably horizontal, but the sense of displacement to the right or left was not readily apparent. A second strike-slip fault was identi- fied along Babbs Hollow (1,100 feet WL, 500 feet SL; Section 7, T6N, R11W). The fault zone was less than 5 feet wide and appeared to have the central breccia zone down-dropped less than 2 feet. The fault zone strikes N30° E to N40° E and is located in the basal portion of the Burlington- Keokuk Limestone. Indications are that the movement is probably right lateral. A third fault is concealed under alluvium at Rice Hollow. This fault was inferred from the 10 to 15 feet elevation difference on the top of the Devonian and Silurian units across the Hollow. These faults and the anticlines suggest a northeast to southwest maximum principal stress direction. The most plausible explanation for the Cap au Grès feature was postulated by Rubey (1952), Harrison (1997), Nelson and Lumm (1985), and Nelson (1995) who discuss the possibility of a deep- seated reverse basement fault. The Cap au Grès resembles monoclinal drape folds found on the Colorado Plateau that formed in sedimentary strata overlying reactivated basement faults (Harrison 1993). Nelson and Lumm (1985) compared the Cap au Grès flexure with Laramide monoclines in the Rocky Mountains and Colorado Plateau, where folds in sedimentary cover overlie faults in the Precambrian crystalline basement. The timing of the Cap au Grès/Lincoln Fold event is constrained by stratigraphic relationships. Facies variations near the structure occur in the Kinderhookian through lower Valmeyeran succession. Detailed mapping near the Cap au Grès indicates that these lower Mississippian rocks apparently thin toward the structure. Therefore, we suggest that the structure was active starting in Late Devonian and continued sporadically through the earliest Pennsylvanian. Outliers of Pennsylvanian Carbondale Formation occur at only slightly different elevations on either side of the Cap au Grès in Calhoun County (Rubey 1952). The St. Louis Formation is the youngest unit significantly displaced, which indicates that major movement took place on the structure between Valmeyeran and Desmoinesian times. The eastern quarter of the quadrangle is not significantly influenced by the Cap au Grès and has a regional easterly dip of roughly 50 feet per mile. Bengal, L.E., 1984, Well report on the O’Donnell well, Jersey County, Illinois: Illinois State Geological Survey, unpublished report, County Number 20408. Grimley, D.A., 1999, Surficial geology map, Grafton Quadrangle (Illinois Portion), Jersey and Calhoun Counties, Illinois: Illinois State Geological Survey, Illinois Geological Quadrangle Map, IGQ Grafton-SG, 1:24,000. Harrison, R.W., 1997, Bedrock geologic map of the St. Louis 30 60 Minute Quadrangle and report: United States Geological Survey, Miscellaneous Field Studies, 22 p. Keyes, C.R., 1894, Crustal adjustments in the upper Mississippi Valley: Geological Society of America Bulletin, v. 5, p. 231–242. Nelson, W.J., 1995, Structural features in Illinois: Illinois State Geological Survey, Bulletin 100, 144 p. Nelson, W.J., and D.K. Lumm, 1985, Ste. Genevieve Fault Zone, Missouri and Illinois: U.S. Nuclear Regulatory Commission, 1985–3. Rubey,W.W., 1952, Geology and mineral resources of the Hardin and Brussels Quadrangles (in Illinois): United States Geological Survey, Professional Paper 218, 179 p. Saxby, D.B., and J.E. Lamar, 1957, Gypsum and anhydrite in Illinois: Illinois State Geological Survey, Circular 226, 26 p. Bedrock Geologic Map of the St. Louis 30 60 Minute Quadrangle and Report H H References Mississippian Burlington and Keokuk Limestones and the Fern Glen Formation St. Louis Limestone Salem Limestone Warsaw Shale Quaternary undifferentiated Unconformity Cedar Valley Limestone Unconformity Joliet Formation Kankakee Formation Unconformity Edgewood Limestone Unconformity Maquoketa Formation Plattin Limestone (cross section only) Kimmswick Limestone (cross section only) Decorah Formation (cross section only) Unconformity Quaternary Devonian and Silurian Ordovician Holocene and Pleistocene Valmeyeran Kinderhookian Mohawkian Erian Niagaran Alexandrian Meppen Limestone Chouteau Limestone Hannibal Shale Glen Park Formation Unconformity Unconformity Cincinnatian Recommended Citation Denny, F.B., and J.A. Devera, 2002, Bedrock Geologic Map, Grafton Quadrangle (Illinois Portion), Jersey and Calhoun Counties, Illinois: Illinois State Geological Survey, Illinois Geological Quadrangle Map, IGQ Grafton-BG, 1:24,000. A A¢ Line symbols are solid where observed, dashed where inferred, dotted where concealed Contact Landslide failure plane Strike-slip fault: arrow indicates direction of movement Line of cross section Structure contour top of the top of the Cedar Valley/Joliet Formation (contour interval 20 feet) Anticline: direction of plunge indicated by the arrows Strike and dip of bedding: number indicates degree of dip Horizontal bedding Vertical joints Water well: number indicates depth of boring (feet) Oil well: number indicates depth of boring (feet) Engineering or ISGS boring: letters indicate ISGS number Abandoned quarry Location of photograph Elevation (feet) of benchmark or survey point Fault: bar and ball on downthrown side Data Type Figure 1 Contact between the Chouteau Limestone and the Meppen Limestone. The contact at this location is clearly angular. It may be an angular unconformity or a depositional feature related to a mud reef facies. Location: 13-6N-12W.

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Page 1: BEDROCK GEOLOGY MAP - ISGSbedrock, but some glacially derived cobbles are basalt, granite, and metamorphic rocks weathered from diamicton that occurs above the bedrock. Small, reworked

George H. Ryan, Governor

Department of Natural ResourcesBrent Manning, DirectorILLINOIS STATE GEOLOGICAL SURVEY

Illinois Geologic Quadrangle Map: IGQ Grafton-BG2002

William W. Shilts, Chief

Digital base map compiled at the Illinois State Geological Survey (ISGS)from digital line graphs (DLG) provided by the U.S. Geological Survey

1927 North American Datum is shown by dashed corner ticks1983 North American Datum Projection and 1,000-meter ticksUniversal Transverse Mercator grid, zone 15, 10,000-foot ticks

Original base map compiled from photogrammetric methods from1952 photography. Field checked 1954 and updated 1995

Buildings and structures are omitted in Grafton, Chautauqua, and gray-colored areas

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ADJOINING 7.5-MINUTE QUADRANGLES

NATIONAL GEODETIC VERTICAL DATUM OF 1929

Contour Interval 20 Feet

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BEDROCK GEOLOGY MAPGrafton Quadrangle (Illinois Portion),Jersey and Calhoun Counties, Illinois

F. Brett Denny and Joseph A. Devera

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A. Alluvium:

B. St. Louis Limestone:

C. Salem Limestone:

D. Warsaw Shale:

E. Burlington and Keokuk Limestone:

F. Fern Glen Formation:

G. Meppen Limestone:

H. Chouteau Limestone

I. Hannibal Shale:

J. Glen Park Formation:

K. Cedar Valley Limestone:

L. Joliet Formation:

M. Kankakee Formation:

N. Edgewood Limestone:

O. Maquoketa Formation:

P. Kimmswick Limestone–Trenton Limestone in thesubsurface:

Q. Decorah Formation:

R. Plattin Limestone:

c . The uplandsediments are composed of a mixture of clay, silt, sand, gravel,and cobbles. The clay, silt, and fine sand fraction is colluviumderived from loessal deposits that thickly mantle the uplandareas. Most of the gravel originated from the underlyingbedrock, but some glacially derived cobbles are basalt, granite,and metamorphic rocks weathered from diamicton that occursabove the bedrock. Small, reworked geodes filled with calciteand quartz crystals were observed. These geodes weather out ofthe Mississippian bedrock and are more abundant in the westernhalf of the quadrangle. Alluvium in the bottomland is composedof a thick sequence of clay, silts, sand, and gravel that rangesfrom Pleistocene to Holocene. Slack-water lake depositscomposed of gray, laminated silt with wood fragments wereobserved in some of the valleys at elevations near 450 feet(Grimley 1999).

. Light gray to medium gray dense lime-mudstone with fossil wackestones. Part of the unit containsquartz sand and subangular limestone breccia clasts. Brecciationis attributed to ancient karstification of gypsum and anhydrite(Saxby and Lamar 1957). Oolitic grainstones, greenish oncoliticpackstones, peloidal grainstones, stromatolitic boundstones, andcarbonate intraclastic conglomerates make up a highly variablemix of microfacies. , a colonial coral,occurs in the upper part of the basal portion of this formation.

is widespread near the base of the unit. Yellowishdolostone beds are also present in this formation. Gray to darkgray chert occurs as nodules and stringers. Siltstones arecalcareous and greenish. The shales are greenish gray andreddish brown, calcareous, soft, and non-fissile. This unit wasonly exposed along a fault slice in the extreme southwest cornerof the Illinois portion of the quadrangle.

. Limestones are tan-brown to light gray and containlaminated tidallites, wackestones to grainstones composed ofrounded and broken fossils and coated grains. Bedding stylesrange from tabular to undulatory. Cross-beds are present ingrainstone facies. The unit has a dirty gray-brown grainyappearance. The diagnostic character of this formation isalternating beds of laminated, fine-grained (calcisiltite) facieswith coarse bioclastic, peloidal to oolitic grains in shoaling-upward cycles. Dolomites are brown and have moldic porosity.Cherts are light gray and may be bioclastic and weather with aporous rind. Cherts occur between grainstones and laminatedbeds as elliptical nodules containing concentric rings that spalloff like egg shells when weathered. Siltstones are brown to lightgray and thinly bedded, typically less than 1 inch thick. Ooliticbeds are rare. The foraminifera, , is anindex fossil for this unit. Other microfossils include calcareousalgae, conodonts, and ostracodes. Fossil invertebrates includespiriferid and productid brachiopods, rugose corals, conularids,and crinoids. Ramose, fenestrate, encrusting, and bifoliatebryozoans are also present. The contact with the underlying unitis gradational.

. Medium-gray, crinoidal, bryozoan wackestones andpackstones that contain a few brachiopods. In the lime-mudstone beds sp. are preserved with coil andfronds attached. Dolostone beds are gray-brown, thinly bedded,and contain chlorite-rich shale clasts with some small quartzgeodes. The upper half of the unit is dominated by shalylimestone and dolostone beds. The lower half contains bluishgray mudstones up to 20 feet thick interbedded with thin lime-mudstones. Conularids and gastropods occur in the shalyportion of this unit. Siltstones are calcareous and fossiliferousand thinly bedded in the lower part. Quartz geodes are commonin the shaly sequences. The geodes weather out and are verycommon in the drainages in the lower portion of the unit. Thebasal contact is poorly exposed but thought to be sharp andconformable with the underlying carbonate beds.

. Light gray to white crinoidal grainstones dominateand are interbedded with nodular and bedded light gray to black

cherts. The cherts are white when weathered, and some havebioclasts of crinoids and brachiopods. Sandy limestonesweather light brown, are cross-bedded, and contain brachiopodand crinoid molds. The unit is characterized by alternatinglayers of light gray to white crinoidal grainstones with beds ofargillaceous and sandy limestones. This cyclic sequence ofcrinoidal limestone over sandy cross-bedded limestone iscommon in the lower part of the unit. Large spirifers arecommon along with crinoids, bryozoans, and corals. Siltstonesare dark gray with a greenish tint and are calcareous. Calciteand quartz-filled vugs from 0.5 to 2 inches in diameter wereobserved. The unit is weathered on the upland surface wherecherty residuum is 20 feet thick. The unit is conformable withthe underlying unit.

.On the eastern side of the Illinois portion of the quadrangle, thelimestone is greenish gray, thin-bedded, and argillaceous; itcontains small calcite geodes and crinoid stems. Green and redshaly calcareous siltstones are diagnostic and are well exposedon the river bluffs near Chautauqua, Illinois. The cherts aregreenish gray, nodular, and fossiliferous. In Dagett Hollow andwestward, the unit is dominantly thin, irregularly bedded, limemudstone with cherty, crinoidal wackestone and packstonefacies; these facies are indistinguishable from the lower part ofthe overlying unit E. Yellowish dolostone facies are alsopresent. The basal part is gradational with underlying formation.

. Light gray totan, massive dolomite limestone, containing small (0.5 to 1.0inch diameter) calcite geodes, light gray chert nodules, andlocally calcareous siltstones. The unit is less than 12 feet thickand normally forms a small resistant weathered face that isfairly well exposed in most drainages. A minor unconformityexists between this unit and the underlying formation. On theriver bluff just west of Chatauqua, an angular relationshipbetween the underlying unit and this formation can be observed(fig. 1).

: . Lightbrown to greenish gray irregular to wavy, thin beds of limemudstone with thin beds of silty dolostone. Calcite geodes withdiameters from 0.5 to 2 inches are common. Some of the calcitegeodes are replaced with quartz. Chert nodules are locallyabundant and typically are dark gray with light gray rims.Crinoidal wackestones containing fenestrate bryozoans andbrachiopods occur in southwest dipping beds near Chatauqua.The unit appears to be gradational with the underlying unit.

. The upperportion may interfinger with the overlying argillaceous lime-stone. Non-fossiliferous, gray, fissile, silty shale to laminatedsiltstone having brown iron oxide and manganese on fracturesof weathered surfaces. The lithology is dominated by a soft,greenish to light gray mudstone, silty at base and fines upwardto a non-fissile mudstone that fractures conchoidally. A thin,black, silty shale near the base of the unit (NE1/4, NE 1/4)Section 1, T6N, R13W, had a very strong petroliferous odor.Typically, the mudstone is not well exposed; however, goodsections were observed at the head of Graham, Dagett,Distillery, and Jerseyville hollows. On the western side of thequadrangle, this unit is conformable with the underlying unit.

. Identified only in theeastern portion of the quadrangle. The limestone is poorlyexposed and was only identified at two locations. At onelocation it was composed of an argillaceous lithographiclimestone with small concretions (1/8 inch diameter) of pyriteand some glauconite. At the second location it was composed ofa fossiliferous and oolitic limestone. The fossils were mostlychonetid and spiriferid brachiopods with crinoid fragments in anoolitic grainstone. The limestone interfingers with the overlyingshales. It is unconformable with the underlying unit.

. Thinand discontinuous fossil packstone with quartz sand. The lowestunit is a brownish gray sandstone overlain by fossiliferous andsometimes argillaceous limestone. It is gray where fresh and

weathers to a brown tint and contains sp. andsp. brachiopods, rugose corals, and platycerid

gastropods. In the quarry east of Grafton, an arthrodire toothwas found in the sandy limestone. The sandy limestone isunconformable with and may downcut several feet into theunderlying formation.

. Thedolostone is yellowish brown to buff gray and has a pittedweathered surface; sucrosic texture with molds of fossils arecommon. The upper part of the dolostone is truncated byoverlying strata. Bedding planes are flat to wavy in places, andbeds are typically several feet thick but can be thinly bedded. InDagett Hollow the upper surface contains polygonal mudcracks. Chert occurs as nodules sporadically throughout theunit. The thin shales have a greenish gray tint. The trilobite

is common in the quarries east ofGrafton. A cheirurid trilobite was also collected from the upperpart of the dolostone. Dolomitization of this and lowerformations within the Silurian makes mapping the Silurian unitsseparately difficult. This unit is unconformable with theunderlying units.

. Thedolostone is yellowish brown to buff gray and has acharacteristic pitted weathered surface. Dolostone beds rangefrom thick to thin. Bedding planes are flat to wavy in places andare separated by thin green clay laminae. Chert occurs asnodules sporadically throughout the unit. Shales have a greenishgray tint. Glauconite is present within this formation. Fossilsinclude brachiopod molds, straight cepholopods, and trilobites.This unit is unconformable with the underlying units in someplaces.

. Thedolostone is brown to buff gray. Beds are thick to thin,argillaceous, and sandy in places. Chert occurs as nodulessporadically throughout the unit. Shales have a greenish graytint. Glauconite was present in a few of the beds, and few fossilswere observed. This unit is unconformable with the underlyingunits.

.This unit is poorly exposed and forms gentle hill slopes that arewell vegetated. The lower part of the formation is calcareousand grades upward into bluish green, thin calcareous siltstonesinterbedded with bluish gray mudstones. The upper part is shalybuff-gray to greenish gray and has interlaminated silts andshales. A thin black shale having phosphatic nodules, fossilfragments, and abundant disseminated pyrite was identified nearthe base of the unit. This black shale was only observed at onelocation in Section 13 (SW, NE) T6N, R13W. The base of thisformation was not observed, but drill logs indicate that it isunconformable with the underlying units.

. White togray, coarsely crinoidal grainstone is the dominant facies in thisformation. Other fossils include sp., sp ,

(trilobites), brachiopods, and gastropods that arecommonly broken in the cross-bedded coarse bioclastics of theformation. Shales are calcareous and may contain pyrite. Chertsare not very common and are white with slight yellow tones.When cracked, the limestones have a faint petroliferous odor.The basal contact is a distinct hardground omission surface.

. Light brownishto greenish limestone or lime mudstone interbedded withorganic-rich reddish brown shales. The cherts are dark gray, andthe dominant fossils are strophominid brachiopods.

. Lightbrown to chocolate brown sublithographic limestone withalternating fossiliferous shales and sandy limestones near thebase.

lay, silt, sand, gravel, and cobble

limestone, limestone breccia,siltstone, and shale

Acrocyathus floriformisA.

floriformis

limestone, dolomite, chert, andsiltstone

Globoedothyra baileyi

dolomitic limestone, siltstone, andmudstone

Archimedes

limestone, siltstone,and shale

limestone, siltstone, and shale

dolomitic limestone

limestone and siltstone

shale, mudstone, and siltstone

limestone

limestone and sandstone

MucrospiriferParaspirifer

dolostone and minor shale

Sthenarocalymene celebra

dolostone and shale

dolostone and minor shale

dolostone, siltstone, mudstone

Subsurface only (described from drill logs and reports).

limestone, dolostone, and minor shale

Receptaculites Illaenus .Isotelus gigas

limestone and shale

limestone, dolostone, and shale

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Economic Geology of the Grafton Quadrangle

Structural Geology of the Grafton Quadrangle

Stone

Oil

Sand and Gravel

Several quarries once mined Silurian dolomites in the quadrangle.Currently, none of these operations are active. According to local residents,most of the quarries were operated for local supply of aggregate andbuilding stone.

The Burlington and Keokuk Formations in the Grafton area are nearlyidentical in lithologic character and were mapped as a single unit. Bothunits are composed in part of calcium-rich limestone. Portions of these unitscontain white crinoidal grainstones to packstones, which commonly arehigh in calcium carbonate. Hindering the quarrying in this unit are thecherty intervals located above and below the high-calcium zones. Relativelythick chert-free beds of economically important limestone are presentlocally.

The chance for economic oilproduction in this quadrangle is marginal because of the shallow depth tothe pay zones along the anticlines and because of faulting in the area alongthe Cap au Grès. Neverthless, t

Sand and gravel are available in the alluvial deposits of the Illinois andMississippi Rivers (see Grimley 1999).

The major structural feature of the quadrangle is the Cap au Grès FaultedFlexure (Keyes 1894). The Cap au Grès is the southeastern extension of theLincoln Fold, which extends over 165 miles into northeast Missouri (Nelson1995). The axis of the Lincoln Fold follows a general northwesterly trendbut turns easterly at its southernmost exposures. The south-easternmostportion of this structure in Missouri and Illinois is called the Cap au Grès.

Two oil tests have been drilled in the quadrangle. According to an oil wellreport written by consulting geologist Lawrence Bengal, the first well had ashow of oil, and the second well drilled in 1984 (Section 2, T6N, R12W)was interpreted by the geologist as intersecting a fault and repeating theDevonian and Silurian units (Bengal 1984). This interpretation wouldrequire at least 150 feet of vertical displacement. No field evidence tosupport a fault of this size was identified.

he shales and the limestone of theOrdovician Decorah contain hydrocarbons. Qualitative distillation tests inthe area have reported the Decorah to produce between 15 to 25 gallons ofcrude oil per ton (Rubey 1952).

In this quadrangle, the Cap au Grès is a faulted monocline with dipsaveraging less than 30° to the southwest and less than 4° to the northeast.The faulted blocks strike N80° W and dip between 40° to 80° to the south.The fault in this quadrangle juxtaposes Silurian age dolomites withMississippian carbonates. Geologic reconstruction of the flexure indicatesas much as 950 feet of vertical displacement may be present along this faultzone at the Deer Plain Ferry location. Evidence for the structure can beobserved in road cuts along Illinois Highway 100 just west of GrahamHollow north of the Deer Plain Ferry landing. At this location theMississippian St. Louis Limestone dips to the south up to 70°.

Along the bluffs west of Grafton, several large blocks of Silurian dolomiteare exposed that are interpreted to be rotational slumps. Several more slumpblocks were observed along a drainage on the west side of Graham Hollow.The basal failure plane of these slumps occurs in the underlying MaquoketaShale. The failure plane was not observed because of the lack of bedrockexposures of the Maquoketa in the immediate area of the slump blocks.

Rubey (1952) mapped the Hardin and Brussels 15-minute quadrangles tothe west of the Grafton Quadrangle. He identified an oval-shaped upliftlocated in Deer Lick Hollow just west of the Grafton Quadrangle, which henamed the Deer Lick Dome. We traced this feature into the GraftonQuadrangle and determined that it was more accurately described as aplunging anticline. The Deer Lick Anticline is closely related to the Domedescribed by Rubey and may be considered the eastern limit of the DeerLick Dome. A second anticline was identified on the structure contours tothe northeast of the Deer Lick Anticline. This second anticline roughlyparallels the Deer Lick Anticline but the dips of both limbs are less than 4°.This anticline also plunges to the southeast where it is concealed by the

alluvial sediments of the Illinois and Mississippi Rivers. The FlorissantDome observed on the

(Harrison 1997) appears to be a continua-tion of the second unnamed anticline in the Grafton Quadrangle.

Two northeasterly trending strike-slip faults were identified in the easternhalf of the quadrangle. The first was located in the bluff just east of Grafton.The fault zone was 10 feet wide and contained breccia fragments, gouge,and secondary calcite veinlets. No vertical offset could be observed in theSilurian dolomite. The fractures were nearly vertical with smooth wavymullion-like planes, which had general trends of N50° E. The direction ofmovement was probably horizontal, but the sense of displacement to theright or left was not readily apparent. A second strike-slip fault was identi-fied along Babbs Hollow (1,100 feet WL, 500 feet SL; Section 7, T6N,R11W). The fault zone was less than 5 feet wide and appeared to have thecentral breccia zone down-dropped less than 2 feet. The fault zone strikesN30° E to N40° E and is located in the basal portion of the Burlington-Keokuk Limestone. Indications are that the movement is probably rightlateral. A third fault is concealed under alluvium at Rice Hollow. This faultwas inferred from the 10 to 15 feet elevation difference on the top of theDevonian and Silurian units across the Hollow.

These faults and the anticlines suggest a northeast to southwest maximumprincipal stress direction. The most plausible explanation for the Cap auGrès feature was postulated by Rubey (1952), Harrison (1997), Nelson andLumm (1985), and Nelson (1995) who discuss the possibility of a deep-seated reverse basement fault. The Cap au Grès resembles monoclinal drapefolds found on the Colorado Plateau that formed in sedimentary strataoverlying reactivated basement faults (Harrison 1993). Nelson and Lumm(1985) compared the Cap au Grès flexure with Laramide monoclines in theRocky Mountains and Colorado Plateau, where folds in sedimentary coveroverlie faults in the Precambrian crystalline basement.

The timing of the Cap au Grès/Lincoln Fold event is constrained bystratigraphic relationships. Facies variations near the structure occur in theKinderhookian through lower Valmeyeran succession. Detailed mappingnear the Cap au Grès indicates that these lower Mississippian rocksapparently thin toward the structure. Therefore, we suggest that the structurewas active starting in Late Devonian and continued sporadically through theearliest Pennsylvanian. Outliers of Pennsylvanian Carbondale Formationoccur at only slightly different elevations on either side of the Cap au Grèsin Calhoun County (Rubey 1952). The St. Louis Formation is the youngestunit significantly displaced, which indicates that major movement tookplace on the structure between Valmeyeran and Desmoinesian times.

The eastern quarter of the quadrangle is not significantly influenced by theCap au Grès and has a regional easterly dip of roughly 50 feet per mile.

Bengal, L.E., 1984, Well report on the O’Donnell well, Jersey County,Illinois: Illinois State Geological Survey, unpublished report, CountyNumber 20408.

Grimley, D.A., 1999, Surficial geology map, Grafton Quadrangle (IllinoisPortion), Jersey and Calhoun Counties, Illinois: Illinois State GeologicalSurvey, Illinois Geological Quadrangle Map, IGQ Grafton-SG,1:24,000.

Harrison, R.W., 1997, Bedrock geologic map of the St. Louis 30 60

Minute Quadrangle and report: United States Geological Survey,Miscellaneous Field Studies, 22 p.

Keyes, C.R., 1894, Crustal adjustments in the upper Mississippi Valley:Geological Society of America Bulletin, v. 5, p. 231–242.

Nelson, W.J., 1995, Structural features in Illinois: Illinois State GeologicalSurvey, Bulletin 100, 144 p.

Nelson, W.J., and D.K. Lumm, 1985, Ste. Genevieve Fault Zone, Missouriand Illinois: U.S. Nuclear Regulatory Commission, 1985–3.

Rubey, W.W., 1952, Geology and mineral resources of the Hardin andBrussels Quadrangles (in Illinois): United States Geological Survey,Professional Paper 218, 179 p.

Saxby, D.B., and J.E. Lamar, 1957, Gypsum and anhydrite in Illinois:Illinois State Geological Survey, Circular 226, 26 p.

Bedrock Geologic Map of the St. Louis 30 60

Minute Quadrangle and Report

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References

Mississippian

Burlington and KeokukLimestones and theFern Glen Formation

St. Louis Limestone

Salem Limestone

Warsaw Shale

Quaternary undifferentiated

Unconformity

Cedar Valley LimestoneUnconformity

Joliet Formation

Kankakee Formation

Unconformity

Edgewood Limestone

Unconformity

Maquoketa Formation

Plattin Limestone(cross section only)

Kimmswick Limestone(cross section only)

Decorah Formation(cross section only)

Unconformity

Quaternary

Devonianand

Silurian

Ordovician

Holoceneand

Pleistocene

Valmeyeran

Kinderhookian

Mohawkian

Erian

Niagaran

Alexandrian

Meppen Limestone

Chouteau LimestoneHannibal ShaleGlen Park Formation

Unconformity

Unconformity

Cincinnatian

Recommended CitationDenny, F.B., and J.A. Devera, 2002, Bedrock Geologic Map, Grafton

Quadrangle (Illinois Portion), Jersey and Calhoun Counties, Illinois:Illinois State Geological Survey, Illinois Geological Quadrangle Map,IGQ Grafton-BG, 1:24,000.

A A�

Line symbols are solid where observed,dashed where inferred, dotted where concealed

Contact

Landslide failure plane

Strike-slip fault: arrow indicatesdirection of movement

Line of cross section

Structure contour top of thetop of the Cedar Valley/JolietFormation(contour interval 20 feet)

Anticline: direction of plungeindicated by the arrows

Strike and dip of bedding: numberindicates degree of dip

Horizontal bedding

Vertical joints

Water well:number indicates depth of boring(feet)

Oil well:number indicates depth of boring(feet)

Engineering or ISGS boring:letters indicate ISGS number

Abandoned quarry

Location of photograph

Elevation (feet) of benchmark orsurvey point

Fault: bar and ball ondownthrown side

Data Type

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Figure 1 Contact between the ChouteauLimestone and the Meppen Limestone. Thecontact at this location is clearly angular. It maybe an angular unconformity or a depositionalfeature related to a mud reef facies.Location: 13-6N-12W.

Using Bedrock at Home

Bedrock Columbia

Haines - 2011 Bedrock Vase

Bedrock Geology Coastlines

Ice model above bedrock

bedrock Documentation

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Substrate controls on the longitudinal profile of bedrock ......1. Introduction The morphology of bedrock channels typically displays high spatial variability. Bedrock channel morphology

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Volcanic Bedrock Glade - Michigan State University · 2019-06-25 · volcanic bedrock glade is associated with volcanic bedrock lakeshore, volcanic cobble shore, volcanic lakeshore

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Limestone Bedrock Lakeshore - Michigan State UniversityLimestone Bedrock Lakeshore, Page 4 Limestone bedrock lakeshore occurs along the shorelines of northern Lake Michigan and Lake

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Micromorphology of diamicton affected by iceberg- keel

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Measurements of high-frequency acoustic scattering from glacially

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Lower Permian glacially influenced deposits in Phuket and ... · Themotic Article Lower Permian glacially influenced deposits in Phuket and adjacent islands, peninsular Thailand