sign in sign up
<<
Home , Fort Payne Formation

GEOLOGY OF KARNAK QUADRANGLE Department of Natural Resources Illinois Geologic Quadrangle Map ILLINOIS STATE GEOLOGICAL SURVEY JOHNSON, PULASKI, AND MASSAC COUNTIES, ILLINOIS IGQ Karnak-G William W. Shilts, Chief W. John Nelson and Jena Hintz 2007

HARRISBURG 35 MI. R. 2 E. R. 3 E. VIENNA 3 MI. A o

Mts

J N Ä 0

35 Qce 450 500

35 N 380 J Mgd 400 0 Qc e 500 50 Ä Mh N J 45 19 / 350 Mh Mh Mh 20 21 Mg Qc

0 40 J

35 0 N

N J k" 400 Mg Mh 32 50 450 N J Qce Mcy 350 0 24 Qc(sc) 50

350 Mcy Mg 0 23 0 Mh 0 Ä 45 ÄÄ

40

J 22 3 Qce N

0 Qc(sc) 50

N 21 5 J 3 Mg N J

Ä Qce Mg 3 45 Mg

5 0 Ä 350 0 50

350 10 o 8 0

J 40 N 0 Ä 0 Qce N o

Ä 350 5 J 3 Mg J 350 Qc(sc) N ÄÄ EXPLANATION Mcy 0 35 0 Qce 55 0 Mcy

Ä 0 4 J

N N Mh 0 J

5

N J 40 3 Qce 0 Mr Qce 350 Qc Cahokia Formation 4

00 Mcy 0 N J J Mcy N 3 40 Mcy 0

5

0 J N 0 35

Qc(sc) 400 e 45 Qc(sc) Mcy 30 Qce N J 29 Cahokia Formation

40 J N 28 Qc(sc) 0 0 Qc(sc) 345 Mcy (silty clay facies) 40 Mr Ä Mcy 345 0 25 45 350 Qc(sc) 40 Qce 0 0 5 3 4 26 00 40 0 Qc Cahokia and Equality 27 Ä N 350 Mcy J Qce 28 0 Qce Formations 5 Qce 3 Mcy Mcy 45 400 Mr 0 o 350 Mr 7 N Cahokia and Henry 400 Qc(sc) J Qc(sc) Mpo 500 0 40 Qce 450 Mr Qch Formations (where Mcy 4 Mcy 3 Mr 0 5 Mcy 0 0 Ä 350 Cahokia is 5 feet or thicker) 3 350 5 Qch Mcy 0 Ä 45 N 45 Mb Mr 231 J 350 / 0 0 Qce k" 185 50 Mr k" Qce Henry Formation Mcy 50 35 Mr e 0 0 Qce o 400 Mr Qh (where Cahokia is thinner Qc(sc) 3 k"100 than 5 feet) 450 Qce Mr 0 Qce Mr 40 Qc 400 Mcy 26 Mr Mpo k" k" 600

k" 40 Mpo Qpl Pearl Formation

31 32 350 0 Ä 165 400 350 Mb 33 Qch k" Mcy 100 0 4 k" 0 Qc 350 40 0 0 36 350 40 5 Mr Qc 3 0 Mr Mb Mr Mb Mr

35 0 Mr Tertiary QTm Mounds Gravel Pliocene and Miocene 40 Ä 500 Mpo

350 34 Mb Ä Mpo 350 33 Mr Qce Mpo Mpo 400 Qce 400 Unconformity 380 Ä Ä Mcy k" 250 Mr Mb McNairy and Post Creek Upper Qce 146 155 Kmp 400 k" Qh e" T. 13 S. Formations Cretaceous Mpo Mb 400 Ä 400 450 k" Ä 111 0 Qch T. 14 S. Unconformity 35

Ä 3 340 ÄÄ 40 370 Qh Mpo 250 Qce Mts Tar Springs Sandstone k" Qh k" Mb T. 13 S. 22 Mpo Mpo Mav 0 45 Qh 35 0 T. 14 S. 0 5 35 0

33 Mav Mb 34 Mgd Glen Dean Qce k"16 Æ 340 Msg 22 3 Mav Mav 5 490 k" " 0 k" 6 4 k 13k" 1 5 19 17 400 k" k" 2 400 Mh Hardinsburg Sandstone 43 400 3 3 0 14 Mpo 40 35 k" Mav 0 0 4 Qce 34 Qch Msg 0 Qh 35 Qce Mav Msg Msg Qce 13k" Qch Mg Msg 5 Qce 33 35 0 Msg 71 340 k" Qce 350 k" Msg 240 Msg 33 Mcy Cypress Formation 340 5 Chesterian Qc(sc) 340

340 34 Qh 3 Qh Qh 0 335 35 340 0 Qch 34 Qh Qh Qh Mr Ridenhower Shale 340 24 Qc(sc) k" 0 34 340 350 10 0 7 8 9 e" 12 34 k" Mb Qh 87 Qh 3 Bethel Sandstone Qh 11 7 40 340 26 340 10 k" 0 45 35 / 9 Qc(sc) 330 Qc(sc) Msg Qce 340 24 35 Qh Qch k" 0 Mpo Paoli Limestone Qh Qce 0 340 Qh 34 340 3 k" 5 Qc(sc) 141 24 0 k" k"42 0

35 . Qc(sc) k" 20 .

MI Mav Aux Vases Formation 350 0 35

35 MI 27 . 340 2.7 0 340 Qce Msg Qc(sc) Qh "40 27k" 89 34 Qce k MERMET 0 k" KY UCAH,

k" D Msg Qh 40 85 Ste. Genevieve Limestone Qc(sc) k" k" 80 PA Qh 0 k"18 QTm Qc(sc) 37 0 0 Kmp 40 350 35 35Qh0 0 Qh 35 Qch Note: Quaternary loess deposits comprising the 16 15 Peoria, Roxana, and Loveland Silts cover nearly all k" 92 340 13 k"10 18 16k" 17 14 123 terrace and upland areas to depths as great as 40 15 200 Kmp k" 16 k" 13 Qce feet. These units are not shown on the geologic map. 340 16 k" 3 k" Qh Qce 50 Qce 400 57 128 Kmp Kmp k" 457 350 QTm k" 35 k"

128 0 k" 60 340 350 0 k" 34 99 100 130 k" k" 96 95 k" 115 350 350 k" k" Kmp 104 k" k" k" 169 0

Qh 45 77 .

77 169 35 .S

k" Qce U

O O

J N T

3 . 50 Kmp Kmp

. k"

169 58 Qce 400 MI 37 Qce QTm k"73 k" MI 0.8 Symbols

0 ILL. 105

37) 9 9 37) 35

. Qce

TO J

. . 80 3 35 N " 5 0 3 Kmp 0 k 0 5 Kmp 5 Strike and dip of bedding, number indicates Kmp 0

35 35 J

1.1 MI 1.1 Qce 0 0 N degree of dip 35 Kmp

0 35 Qce 21 J

QTm 24 19 20 400 k" N

23 130 Horizontal bedding (VIA ILL (VIA OLMSTED OLMSTED " 86 22 3 k

50 N 21 400 J

Kmp Kmp QTm Vertical joints or fractures 4

J

0 0 N

5 0

N 3 J QTm 350 40 40 260 0 170 Outcrop of special note, shown where unit 35 0 k" k" 40 130 0 N J 0 k" 35 or contact was well exposed during mapping

3 0 5 k"

0

N 5 J 10 N

400 160 122 J QTm

350 k" k" Qce Active pit or quarry

N J QTm o 86 0 k"

Kmp 40 Abandoned pit or quarry J Qce 65 N

40 Æ

e" N J 0 35 165 Kmp 0 0 k" 0 35 QTm Æ 40 Kmp 0 k"195 40

Kmp Qce N J Drill Holes N

350 J Qce J

QTm 400 N 390 from which subsurface data were obtained 370 50 35 3 0 0 165 40 14290 k" 40 30 k" e" 350 Kmp 248 28 Stratigraphic boring 25 N J

0 165 k" k" k"

J k" 61 129 0 N Qce "70 0 27 26 k 4 QTm 0 e" QTm Qpl Water well 28 Qce 40 QTm 35 0 350 400 3 N J Kmp

50 e" J Kmp N Engineering boring 350 35 40 Kmp Qce 40 0 0 0 40 00 0 4 250 Numeric label indicates total depth of boring in feet. Kmp k"

Kmp 400 200 J Enlarged Area, Figure 1 N Dot indicates location accurate within 100 feet.

40 k" k"585 185 k"170 Kmp

Kmp 0 k"

40

N QTm J

0 0

21 0 N 0

k" J 35 QTm 27 4 Kmp 0 k" 40 1 400 0 Line Symbols N J 0 0 0 0 N J QTm 5 5

3 Qce 45 QTm QTm dashed where inferred, dotted where concealed

J Kmp Kmp N

Qce Msl Ç Æ 35 N

J 35 10

J Contact

N J 0

N N J 0 o 40 0 350 400 0 36 Post Creek N 450 Qce

0 J 50 50 N

40 k" Kmp J Normal fault; bar and ball on downthrown side

QTm N J

North J N J 400 o

N 35 31 33 N

Msm J 32 Kmp 0 36 Qce 35 N 350

J N J QTm Line of cross section

N 34 J

Qce 0 A A�

40 N

40 J 36 QTm 350 0 0 33 N J 350 N 37 J 200 R. 2 E. R. 3 E. k" 0 400 QTm A’

Base map compiled by Illinois State Geological Survey from digital data provided by SCALE 1:24,000 Geology based on field work by J. Nelson and J. Hintz, 1999–2000. the Geological Survey. Compiled from imagery dated 1998. 1 1/ 2 0 1 MILE Digital cartography by J. Domier, D. Byers, J. Magnotta, M. Bentley, and S. Geegan, Illinois 1000 0 1000 2000 3000 4000 5000 6000 7000 FEET North American Datum of 1983 (NAD 83) State Geological Survey. Projection: Transverse Mercator 1 .5 0 1 KILOMETER 10,000-foot ticks: Illinois State Plane Coordinate system, east and west zones zone The Illinois State Geological Survey, the Illinois Department of Natural Resources, and the (Transverse Mercator) State of Illinois make no guarantee, expressed or implied, regarding the correctness of the 1,000-meter ticks: Universal Transverse Mercator grid system, zone 16 interpretations presented in this document and accept no liability for the consequences BASE MAP CONTOUR INTERVAL 10 FEET of decisions made by others on the basis of the information presented here. The geologic SUPPLEMENTARY CONTOUR INTERVAL 5 FEET interpretations are based on data that may vary with respect to accuracy of geographic Recommended citation: NATIONAL GEODETIC VERTICAL DATUM OF 1929 location, the type and quantity of data available at each location, and the scientific and Nelson, W.J., and J. Hintz, 2007, Geology of Karnak Quadrangle, Johnson, Pulaski, technical qualifications of the data sources. Maps or cross sections in this document are and Massac Counties, Illinois: Illinois State Geological Survey, Illinois Geologic Released by the authority of the State of Illinois: 2007 not meant to be enlarged. Quadrangle Map, IGQ Karnak-G, 2 sheets, 1:24,000, report, 8 p.

1° ADJOINING ROAD CLASSIFICATION 123 QUADRANGLES MA TR 1 Mt. Pleasant NOR GNETIC Primary highway, Light-duty road, hard or UE NOR UE 2 Vienna hard surface improved surface 3 Bloomfield 45 Secondary highway,

4 Cypress TH hard surface Unimproved road

5 Mermet T

For more information contact: H 6 Olmsted Illinois State Geological Survey 678 7 Bandana 615 East Peabody Drive 8 Joppa APPROXIMATE MEAN U.S. Route State Route Champaign, Illinois 61820-6964 DECLINATION, 2007 (217) 244-2414 http://www.isgs.uiuc.edu

IGQ Karnak-G Sheet 1 of 2 CACHE VALLEY

SERIES A Cahokia Formation Silt, sand, and gravel. Clayey and sandy silt, mottled in O Golconda Formation Limestone and shale. The formation is divided into three THICKNESS and FORMATION GRAPHIC COLUMN UNIT brownish and yellowish gray, moderately stiff, and massive to laminated. Pellets members. The Haney Limestone Member at the top is composed of medium to dark (FEET) STAGE and fracture-fillings of iron and manganese oxides are common. Sand and gravel gray and brownish gray limestone that forms discontinuous ledges. The limestone is SYSTEM occur mainly in the lower part of the unit, forming a fining-upward sequence. Gravel largely skeletal wackestone, packstone, and grainstone with a few beds of lime mud- HOLOCENE Cahokia 0–20 0–30 AB is chiefly pebbles derived from the Mounds Gravel south of Cache Valley and stone. Rounded grains and ooids are common, and cross-bedding is present.

Y chiefly fragments of sedimentary rocks north of the Cache. Small streams tributary include brachiopods, bryozoans, blastoids, crinoids, and rugose corals. Beds typically to the Ohio River have wide, flat bottoms that represent an erosional bench, not a are 4 to 12 inches thick and are separated by wavy to hummocky, argillaceous part- Henry Equality 0–130 0–155 CD terrace. The Cahokia is only a few feet thick in these valleys. The Cahokia consists ings. The Fraileys Shale Member is dominantly shale with thin interbeds of limestone OCENE of Holocene alluvial deposits. The lower contact may be erosional to gradational; this in the upper part. Most of the shale is greenish gray to dark gray, fissile, and cal- TERNAR A

WISCONSINAN unit is difficult to distinguish from the Equality Formation. careous and contains marine fossils. The limestone is similar to that of the Haney QU PLEIST Member but occurs in thinner beds with higher clay content and abundant fossils. An ILLINOIAN Pearl Bedrock 0–30 E B Cahokia Formation, silty clay facies Clay and silty clay. Medium to dark olive interval of red and green variegated mudstone occurs near the top. The Beech Creek gray, greenish gray, and brownish gray clay and silty clay have absent or weak Limestone Member at the base of the Golconda is less than 10 feet thick, and only lamination and are rich in organic matter. This facies is confined to present or former one exposure was found: the cutbank of the Cache River at the foot of Wildcat Bluff sloughs and swamps in the Cache Valley and its major tributaries. Within the main in the SW¼ of Sec. 19, T13S, R3E. Cache Valley, the silty facies fills abandoned channels that date to the final course SOUTH OF CACHE VALLEY of the Ohio River in the valley and overlies the Henry Formation. Elsewhere, this unit P Cypress Formation Sandstone, siltstone, and shale. The upper one-half to two- overlies the Equality Formation with a gradational contact and is difficult to differenti- thirds of this unit is concealed by loess; outcrops and drill holes in adjacent quad- ate from the Equality. rangles show the upper Cypress to be interbedded shale, siltstone, and thin-bedded sandstone. The lower part of the Cypress is sandstone that forms prominent cliffs SERIES C Henry Formation Sand, gravel, and silt. Chiefly sand that is light gray to light 15 to 40 feet high. The white to light gray, very fine- to fine-grained quartz arenite is THICKNESS and FORMATION GRAPHIC COLUMN UNIT yellowish gray and very fine to very coarse. Grains are subrounded to subangular slightly friable and has a sugary texture. Sandstone near the top of the cliffs tends (FEET) STAGE and are composed of roughly 90% quartz and 10% chert and other lithic fragments. to have planar to wavy lamination or thin bedding. In the lower part of the cliffs, the SYSTEM Sand occurs in upward-fining sequences that grade up to silt or silty clay. Gravel is sandstone is thickly bedded to massive and in places shows unidirectional, south- or Peoria Silt 0–20 F Y WISCONSINAN Roxana Silt 0–17 G rounded to well-rounded and dominantly fine “pea gravel,” in which most pebbles are west-facing planar and trough cross-bedding. Convolute or slumped laminations, OCENE TER-

A ILLINOIAN Loveland Silt 0–8 H NAR smaller than about ¼ inch and few exceed about ½ inch in diameter. Chert is the which partially or completely obscure cross-bedding, are seen on many outcrops. PLEIST

QU PRE-ILLINOIAN

Y Mounds I major constituent, followed by quartz and a wide variety of sedimentary, igneous, and Also common are “healed” high-angle fractures. The lower contact was not observed, PLIOCENE 0–70 Gravel metamorphic rock fragments derived from glacial outwash. The sand and gravel typi- but, in neighboring quadrangles, it is erosional.

TER- MIOCENE TIAR cally are loose, lacking a significant clay or silt matrix. The Henry underlies the main Cache Valley, where it may exceed 128 feet in thickness in places. It is interpreted as Q Ridenhower Formation Shale, thin limestone. The unit is dominantly shale that J fluvial channel, point bar, and midchannel bar deposits of Wisconsinan age, at which is dark gray, olive-gray, and greenish gray, soft and fissile, and lacks silt. Siderite McNairy 0–145 time the Ohio, Cumberland, and Rivers flowed through the Cache Valley bands and nodules are numerous. Limestone interbeds a few inches to several feet CEOUS

A (Fisk 1944, Masters and Reinertsen 1987). Thin loess (Peoria Silt) or dune sand thick are dark bluish gray, coarse-grained, very fossiliferous wackestone and pack- (alum) overlies the Henry in many places. The lower contact, known only from well stone. The lower contact is sharp.

CRET records, typically is erosional, but the Henry is difficult to differentiate from the Pearl Post Creek 0–57 K Bedrock Formation. R Bethel Sandstone Sandstone, sandy limestone. Very fine- to fine-grained sandstone commonly weathers brownish orange to dark brown. Much of the sand- D Equality Formation Silt, clay, and minor sand and gravel. Silt and clay are stone, especially in the lower part, is strongly calcareous and contains bryozoans, medium to dark gray to brown; less commonly they are greenish to bluish gray. Some brachiopods, and echinoderms. Weathering commonly removes the calcite, leaving BEDROCK reddish to orange-brown layers occur in the upper part of the unit. Consistency varies a highly porous, iron-stained rock. Near the base of the unit, sandstone intergrades from stiff to soft, plastic “gumbo,” and structure varies from massive to finely lami- with sandy limestone: skeletal wackestone, packstone, and grainstone. Sedimentary nated or varved. Wood fragments and decomposed vegetation are common. Lenses features include planar lamination, cross-lamination, ripple cross-lamination, and THICKNESS of sand and gravel ranging up to about 6 feet thick occur chiefly in the lower part of small-scale trough and herringbone cross-bedding. A conglomerate of shale pebbles SERIES FORMATION MEMBER GRAPHIC COLUMN UNIT (FEET) unit. The Equality underlies all wide, flat-bottomed valleys tributary to the main Cache is found locally at the erosional lower contact.

SYSTEM Valley. These valleys are deeply incised into bedrock. The Equality commonly is 50 to 100 feet thick and reaches 155 feet in a well near Forman. This formation is inter- S Paoli Limestone Limestone, shale, and minor siltstone. The Paoli is divisible Tar Springs 30 L preted as fine-grained fluvial overbank sediments and slack-water lacustrine deposits into four members. The Downeys Bluff Limestone Member at the top comprises an Glen Dean 50 that accumulated during the Wisconsinan age. The Equality intergrades laterally with upper limestone 10 to 15 feet thick, a middle shale 10 to 15 feet thick, and a lower Limestone M the Henry Formation and overlies older units unconformably. limestone 5 to 10 feet thick. Limestone is largely light gray, fine to coarse skeletal and oolitic grainstone, portions of which are laminated and other portions are cross- Hardinsburg 70 E Pearl Formation Sand and gravel. Within the Cache Valley this unit is lithologi- bedded. Sparse pink to orange crinoid fragments occur in the upper limestone bench. N cally similar to the Henry Formation, except that the Pearl contains coarser gravel The middle shale of the Downeys Bluff is dark gray to greenish gray, soft, and fissile. (many pebbles larger than 1 inch) and scattered cobbles and boulders. The Pearl It contains abundant marine fossils and thin lenses and interbeds of shaly lime- Haney may be more than 30 feet thick in places, underlying the Henry Formation and resting stone. The Yankeetown Member is 10 to 15 feet thick and comprises green to purple 70–80 Limestone on Mississippian bedrock. Several boreholes in tributaries of the Cache encountered variegated, calcareous mudstone at the top, variegated and fissile silty shale in the coarse reddish brown gravel in a clay matrix underlying the Equality Formation. This middle, and gray massive siltstone at the base. The only good exposure is at an Golconda 140 O gravel also may be Pearl Formation. A possible outcrop of the Pearl is in the bank of abandoned limestone quarry about one-half mile northeast of Belknap. The Shet- Fraileys Sh. 50–60 Patterson Branch near the center of Sec. 28, T14S, R3E. In this outcrop the well- lerville and Levias Limestone Members together are 75 to 100 feet thick. The only worn, tightly packed gray chert gravel is overlain by Peoria Silt. The Pearl Formation outcrop of the Shetlerville observed during mapping is 8 feet of light gray, fine- to Beech Creek Ls. 5–10 is fluvial and possibly colluvial sediment of Illinoian age. The lower contact is uncon- coarse-grained crinoidal packstone and grainstone with thin shale interbeds in the formable. Belknap quarry. A small outcrop of purplish gray, hematitic, oolitic limestone along the roadside at the West Eden Cemetery (Sec. 4, T14S, R2E) represents the most typi- F Peoria Silt Silt. The Peoria is massive, slightly clayey silt (loess) with rare fine cal rock type for the Levias. The lower contact was not observed. Cypress 100–160 P sand grains. The upper part is generally yellowish brown to dark brown, grading downward to mottled gray and yellowish brown. The Peoria is 5 to 10 feet thick in T Aux Vases Formation Sandstone, minor siltstone, shale, and limestone. The Aux most places, reaching 20 feet along the southern margin of the Cache Valley. It is Vases is largely sandstone that is light gray to greenish gray, very fine-grained, and interpreted as an eolian (wind-blown) deposit. The lower contact is gradational. Not calcareous. Marine fossils and oolites are common. Interbedded with the sandstone mapped. are greenish gray shale and siltstone and light gray, sandy limestone. No outcrops Ridenhower 65–90 Q were found, but well records indicate the presence of this unit. Good exposures are in G Roxana Silt Silt. The Roxana is medium-dark brown to reddish brown loess that the White Hill Quarry about 1 mile west of the map area. typically has uniform color, without mottling, and higher clay content than the Peoria.

CHESTERIAN Bethel Ss. 10–30 R This unit commonly is difficult to distinguish from the Peoria and, like the latter, prob- U Ste. Genevieve Limestone Limestone, minor dolomite, and sandstone. The Downeys Bluff 30–40 ably is an eolian sediment. The lower contact is gradational. Not mapped. most typical rock type is light to medium gray, medium- to coarse-grained oolitic Limestone and skeletal grainstone that commonly is cross-bedded. This rock is interbedded Yankeetown 10–15 H Loveland Silt Silt. This massive silt (loess) is strongly mottled in yellow, red, with finer-grained and darker gray to brownish gray packstone, wackestone, and Paoli Shetlerville 45–60 S and orange and has prominent vertical gray streaks. Clay content is high; sand and lime mudstone that is argillaceous and contains vitreous blue-gray chert nodules. Limestone Limestone

120–145 scattered chert granules are common. The Loveland is strongly weathered and com- Also present are interbeds a few feet thick of light gray microgranular, porous dolo- Levias 30–40 monly displays root casts or traces. This unit is interpreted as an eolian deposit in mite; sandstone lithologically similar to the Aux Vases; and greenish gray shale and Limestone which a thick paleosol, the Sangamon Geosol, is developed. The Loveland is gener- siltstone. Fossils include abundant echinoderms, bryozoans, and brachiopods. Within Aux Vases 20–30 T ally thin and lenticular. Its lower contact is gradational to the Metropolis Formation but the map area, the Ste. Genevieve is known from outcrops that border the Cache unconformable to older units. Not mapped. Valley and from sample logs of several wells. Excellent exposures of this unit occur in the active quarry at White Hill, 1 mile west of the map area. The estimated thickness I Mounds Gravel Gravel and sand. The lower part is dominantly gravel, composed of 250 to 335 feet is based on limited data in the map area and better well records in mostly of subrounded to well-rounded chert pebbles up to 4 inches across and nearby quadrangles. bearing a glossy yellowish brown to bronze patina. Small quartz pebbles are a minor constituent. The matrix is red-brown fine to very coarse sand that is 80 to 90% quartz V St. Louis Limestone Limestone and dolomite. Medium to dark gray, fine-grained Ste. and 10 to 20% chert. Gravel is crudely layered and generally becomes finer upward, packstone and wackestone, along with microgranular to lithographic lime mudstone Genevieve 250–335 U grading to sand. The upper part of the Mounds is largely fine to coarse sand that is and beds of microgranular dolomite. Dark gray to black, vitreous chert nodules are Limestone dark red with gray and yellow mottling and contains scattered chert pebbles bearing common. The St. Louis generally lacks oolitic limestone. The St. Louis is exposed the typical patina. Layering of sand is absent to indistinct, locally outlined by lenses of at low water in the bed of Post Creek Cutoff at the bend in the creek in the northern gravel. The lower contact is unconformable. The Mounds Gravel rests on an erosion part of Sec. 35, T14S, R2E. The colonial coral Acrocyathus floriformis, a guide surface that descends northward from 430 to 450 feet elevation near the Ohio River for the lower St. Louis, is present in this outcrop. Aside from this lone outcrop, the St. to about 370 to 380 feet near the Cache Valley. The Mounds also is found at eleva- Louis is known from scanty well records. Better quality well logs in adjacent quad- tions below 350 feet where it has dropped into grabens and sinkholes along Post rangles indicate an average thickness of about 300 feet. Creek Cutoff. W Limestone. Interbedded light to medium gray, medium- to J McNairy Formation Sand, silt, and clay. Sand varies from white to light gray and coarse-grained skeletal packstone and grainstone, and medium to dark gray skeletal bright orange, red, and yellow; sand is very fine- to medium-grained and, in most wackestone and lime mudstone. Fossils include brachiopods, bryozoans, crinoids,

MISSISSIPPIAN cases, highly micaceous. Light gray clay and silt occur as laminae, lenses, and rip-up and blastoids. Oolites and rounded fossil grains occur in grainstone. Bedding is com- clasts. Cross-bedding is common, as are very regular, fine planar laminations that monly thick, with wavy argillaceous partings and some cross-lamination. Limestone may be tidal rhythmites. Silt and clay are light to dark gray and may be mottled in commonly emits a petroliferous odor when struck with a hammer. The estimated yellow, gray, and magenta (where weathered). Bands and nodules of ironstone occur thickness, 350 to 400 feet, is based on well records in adjacent quadrangles. The St. Louis 300 in clay and represent Liesegang bands. The lower contact is unconformable. contact to the Ullin Limestone is gradational with intertonguing. Limestone V K Post Creek Formation Gravel and conglomerate. Gravel is composed of white, X Ullin Limestone Limestone. Three varieties of limestone were observed in cores gray, and brown, angular to rounded pebbles and cobbles of chert with lesser drilled by the ISGS east of the mouth of Post Creek Cutoff in the adjacent Bandana amounts of quartz, orthoquartzite, and sandstone. The formation is supported in a Quadrangle and in cores drilled by the U.S. Army Corps of Engineers west of the matrix of pyritic sand and clay and commonly is cemented by silica and iron oxide. mouth of Post Creek Cutoff. The Harrodsburg facies is composed of coarse, medium The type locality is in the bank of the Post Creek Cutoff adjacent to the bridge near gray to brown echinoderm fragments in a matrix of large, light gray fragments of bryo- the center of Sec. 2, T15S, R2E (Harrison and Litwin 1997). Water-well drillers log zoan fronds. This rock is massive to faintly laminated and exhibits intergranular and the Post Creek as gravel, chert, or novaculite. Previous geologists called this unit the micro-vuggy porosity. Scattered brachiopods and micrite intraclasts are present. The . The lower contact is unconformable. Ramp Creek facies is medium to dark gray lime mudstone and skeletal wackestone that is silty and argillaceous and contains lenses of dark gray, dull to vitreous chert. L Tar Springs Formation Sandstone, siltstone, and shale. Sandstone float from Thin layers of coarse crinoidal packstone and grainstone occur in this facies, which the basal 30 feet of this formation occurs at the northeast corner of the map area. In is transitional to the Harrodsburg facies. The bryozoan mound facies, least common adjacent areas, the Tar Springs is 80 to 130 feet thick and is approximately one-half in cores, is composed of medium to dark brownish gray bryozoan wackestone in sandstone and one-half shale and siltstone. The sandstone is light gray, very fine- to which large bryozoan fronds lie parallel to bedding. Well records east of the map area fine-grained, thin- to thick-bedded quartz arenite that displays ripple marks, load indicate that the Ullin averages about 135 feet thick. Well data near Post Creek Cutoff casts, and small burrows and trails. The siltstone and shale are dark gray to greenish indicate a similar thickness; however, the Ullin thickens westward to 400 to 450 feet in Salem gray and show horizontal and ripple lamination. These rock types are interbedded the Dongola Quadrangle (Nelson et al. 1999). The contact to Fort Payne is probably 350–400 W Limestone and intergrade laterally. The lower contact is gradational in some places and ero- gradational. sional in others. ALMEYERAN

V Y Limestone. Largely dark gray (lighter near top) micro- M Limestone and shale. This unit is poorly exposed on the granular lime mudstone that is more or less dolomitic and silty. Scattered fine bio- upper slopes of the hill at the northeast corner of the map area. Outcrops and wells clasts, largely echinoderm fragments, are the only fossils. Samples are pyritic and in neighboring quadrangles show the upper 18 to 25 feet to be limestone with thin contain about 10% dark gray chert. Thickness is estimated to be 630 to 685 feet. shale interbeds. The limestone is light to dark gray and brown, medium- to coarse- grained skeletal packstone and grainstone. Rounded fossil grains and oolites are References common. The lower 25 to 32 feet of the Glen Dean is shale that is medium to dark gray and greenish gray, soft and fissile, calcareous, and fossiliferous and contains Fisk, H.N., 1944, Geological investigation of the alluvial valley of the lower lenses and thin interbeds of limestone. Fossils consist of brachiopods, bryozoans, River: Vicksburg, Mississippi, U.S. Army Corps of Engineers, Mississippi River and echinoderms. Generally the lower contact is gradational. Commission, 78 p. Ullin Harrison, R.W., and R.J. Litwin, 1997, Campanian coastal-plain sediments in south- 135–200? X N Hardinsburg Formation Sandstone, siltstone, and shale. The upper two-thirds Limestone eastern and southern Illinois: Significance to the early geologic history of this unit is poorly exposed in the map area but probably consists of shale and of the northern Mississippi Embayment: Cretaceous Research, v. 18, p. 687–696. siltstone, containing lenses of fine-grained sandstone less than 5 feet thick. The lower part is sandstone that forms cliffs and ledges 10 to 25 feet high. The sandstone is Masters, J.M., and D.L. Reinertsen, 1987, The Cache Valley in southern Illinois: Boul- light gray, fine-grained quartz arenite that has alternating intervals of ripple lamina- der, Colorado, Geological Society of America, Centennial Field Guide, North- tion and medium- to large-scale cross-bedding (beds 1 to 4 feet thick). Interference Central Section, p. 257–262. ripples, shale rip-up clasts, and poorly preserved burrows are common. The erosional Fort Payne 630–685 Y Nelson, W.J., L.R. Follmer, and J.M. Masters, 1999, Geologic map of the Dongola contact with the underlying Golconda Formation is well exposed on bluffs east of Quadrangle, Alexander, Pulaski, and Union Counties, Illinois: Illinois State Geo- Dutchman Creek a short distance north of the map area. logical Survey, Map IGQ-19, 1:24,000.

North South A A� Elevation (feet) Wildcat Bluff . 600 C.B.&Q. Cache Valley . Mississippi Embayment 600 Ql Railroad Ql Cache River Ql Mh Mh Ql Ql Mb Qtm Ql Qtm Qtm Ql Ql Ql Qc Qc Ql Qce Ql Pulaski Co Qce 400 Qe Johnson Co Qce 400 Mg Qc Qc(sc) Mcy Mpo Qc Belknap Qc(sc) Qc(sc) Qce Karnak Mcy Mr Kmp Qe Qh Qh Qe Mcy Mb Qe 200 Mb Mav 200 Mr Qpl? Qpl? Msg Msm Sea Mpo Mav Msl Sea Level Level Msg Mu –200 Msl –200 Msm Mfp

–400 –400 Horizontal scale: 1 inch = 2,000 feet Vertical scale: 1 inch = 1,000 feet Equality Formation Ridenhower Shale Aux Vases Formation Ql Loess Qe Qpl Pearl Formation Mh Hardinsburg Sandstone Mr Mav Msm Salem Limestone Vertical exaggeration: 2�

Cahokia and Equality Qc Cahokia Formation Qce Qtm Mounds Gravel Mg Golconda Formation Mb Bethel Sandstone Msg Ste. Genevieve Limestone Mu Ullin Limestone Formations

Cahokia Formation McNairy and Post Creek Qc(sc) Qh Henry Formation Kmp Mcy Cypress Formation Msl St. Louis Limestone Mfp Fort Payne Formation (silty clay facies) Formations Mpo Paoli Limestone

IGQ Karnak-G Sheet 2 of 2