iS Guidebook 18

Early Paleotopography and Depositional Environments, Rock Island County, Illinois

Richard L. Leary C. Brian Trask

Nineteenth Annual Meeting, North-Central Section of the Geological Society of America Northern Illinois University, De Kalb, Illinois, April 25-27, 1985

Sponsored by the Illinois State Geological Survey

Early Pennsylvanian Paleotopography and Depositional Environments, Rock Island County, Illinois

Richard L. Leary Illinois State Museum Springfield, Illinois 62706

C. Brian Trask Illinois State Geological Survey Champaign, Illinois 61820

ISGS Guidebook 18

Illinois State Geological Survey Morris W. Leighton, Chief

Natural Resources Building 615 East Peabody Drive Champaign, Illinois 61820

1985 Digitized by the Internet Archive

in 2012 with funding from

University of Illinois Urbana-Champaign

http://archive.org/details/earlypennsylvani18lear WARNING: ACCESS TO THESE QUARRIES IS RESTRICTED!!

Persons entering without permission are subject to arrest and fines! Primarily due to OSHA (Occupational Safety and Health Administration) and MSHA (Mine Safety and Health Administration) federal regulations and insurance requirements, ALL persons entering property associated with quarries and mines MUST have WRITTEN PERMISSION and MUST WEAR hard hats, safety goggles, and steel-toed shoes and meet all other current federal safety regulations. WRITTEN permission MUST be obtained from the appropriate company PRIOR to entering the quarry property. Write well in advance of any planned visit to assure completion of necessary arrangements before the selected date.

Write to:

(Allied Stone Company quarry) (Collinson Stone Company quarry)

Mr. James O. Ellis, President Mr. Richard DeShepper Moline Consumers 3115 23rd Avenue 313 16th Street Moline, IL 61265 Moline, IL 61265 1,1 «»*** EARLY PENNSYLVANIAN PALEOTOPOGRAPHY AND DEPOSITIONAL ENVIRONMENTS, ROCK ISLAND COUNTY, ILLINOIS

INTRODUCTION

The Geological Society of America, North- assemblage is distinct from the more com- Central Section, presents this one-day field monly preserved "coal-swamp flora." trip to Rock Island County, Illinois, where you The distinctive character of the flora has will have the opportunity to examine the pre- been considered the result of the distinctive Pennsylvanian unconformity, overlying sedi- environment that produced the flora. All flora ments, and an early Pennsylvanian upland from Rock Island County, and one from compression flora. The itinerary repeats a Brown County to the south, have been referred trip originally offered during the Ninth Inter- to as an "upland" flora. national Congress of Stratig- This field trip will give geologists and raphy and Geology (IX-ICC) in 1979. paleobotanists an opportunity to examine the In recent years the nature and significance stratigraphic and paleotopographic setting of of the Mississippian-Pennsylvanian boundary this flora. It will also provide an opportunity have received considerable attention. In Illi- to discuss the nature of the flora, its relation- nois, as in much of the continental United ship to the setting, and the paleoecological States, the boundary is marked by a major and evolutionary implications. unconformity. Extensive topographic relief The guidebook itself is a reprint of Leary developed on underlying strata prior to initial (1979). Some revisions have been made to up- Pennsylvanian deposition. In parts of Illinois, date the guidebook with new exposures, new especially along the margins of the Illinois data, and new references. The geology of the Basin, erosion removed great thicknesses of field-trip area has been discussed by Leary pre-Pennsylvanian rocks (although some forma- (1981). Additional information concerning tions may have been thinner than equivalent Labriscorpio alliedensis is also available (Leary, strata in the deep part of the basin, or in fact, 1980). Phillips and Peppers (1984) have sum- may never have been deposited). marized regional paleoenvironmental patterns In the Rock Island County area, the of coal swamps and discussed the effect of cli- Pennsylvanian System overlies rocks ranging mate on coal occurrence in Euramerican coal in age from to . Pre-Pennsyl- fields. vanian topography was characterized by deep Figure 6 has been revised to reflect new valleys, high hills, and some karst features. data. Now this illustration better shows the Although much of this topography can be pre-Pennsylvanian paleovalleys in the Rock examined only by means of drilling records, Island County area. Figure 7 shows the full some higher elevations are now exposed. extent of the channel exposed in the Allied Several of these features will be seen on this Stone Company quarry. It also indicates that field trip. most of the fossil-bearing strata have now been In recent years the senior author has col- removed by quarrying. Figure 8 has been lected a large number of well preserved early updated to show a current (1984) cross section Pennsylvanian fossils in the Rock Island of a channel. area. The fossils occur in rocks immediately Russel A. Peppers at the Illinois State overlying the erosional surface developed on Geological Survey has examined the spore Devonian carbonate strata (Cedar Valley and content of the coal from Stop 2. He believes Wapsipinicon Limestones: Middle Devonian (1984. personal communication) that this Series). The composition of the fossil plant coal is lower Westphalian A in age. Guidebooklet: Illinois State Museum No. 4

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Figure 1. Geologic map of the Rock Island County area. Circled numbers are stops. Base map from Edmund and Anderson, 1967. <

1979 Leary: Pennsylvanian Flora, Rock Island County, Illinois

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Figure 2. Generalized sub-Pennsylvanian geologic map of Illinois. (From Plate 2, Paleotectonic investigations of the Pennsylvanian System in the United States, McKee and Crosby, Coordinators, U.S.G.S. Prof. Paper 853.) Guidebooklet: Illinois State Museum No. 4

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Geological Background the Rock River north of Vandruff Island and the Allied quarry. This hill is about 10 m above the Stratigraphy. In the Illinois Basin, Penn- river level which is the approximate elevation sylvanian strata overlie rocks ranging in age of the major portion of the unconformity here. from to Mississippian. The sub- This hill will be seen at Stop 2. Pennsylvanian strata are primarily carbonates Although extensive areas of relatively low and had been exposed to subaerial erosion. relief are present, some deep valleys were also Along the western margin of the Basin, Penn- developed prior to earliest Pennsylvanian sylvanian rocks overlie older Mississippian sedimentation. One such valley occurs in south- rocks in the central part and Devonian rocks eastern Rock Island County (see map, Fig. 6). in the northwest (Reinertsen et a/., 1974). A system of steep-sided, flat-bottomed Silurian and Ordovician strata underlie the channels was developed on Devonian limestone Pennsylvanian along the northern margin (see in the Rock Island County area. Although now geologic maps, Figs. 2, 3). largely destroyed by quarrying operations, these The relevant portion of the stratigraphic were observed in both the Allied Stone Company sequence in the Rock Island County area is quarry and the Cleveland quarry. The primary illustrated in Figure 4. The major unconformity trend of these channels was east-west (Fig. 7), between the Devonian Cedar Valley Limestone but the locations were apparently controlled by and basal Pennsylvanian indicates a long period jointing in the limestone. The exact nature of of erosion prior to earliest Pennsylvanian sedi- these channels has not been determined. mentation. Because strata as young as the St. These channels were 4 to 6 m deep and 8 Louis Limestone (Valmeyeran = basal Visean) to 20 m wide (Fig. 8). They were filled with occur beneath the unconformity to the south, shale, mudstone, and occasional lenses or thin, it is believed that the period of erosion came in discontinuous layers of sandstone. Occasional Late Mississippian/Early Pennsylvanian (at the thin layers and masses of pyrite are also present base of the European Namurian?). with a few pyritized plant axes. The shale and Pre-Pennsylvanian topography. Major valleys mudstone are almost exclusively gray except are known to have drained eastward and south- for the upper portion which is sometimes thinly eastward across the pre-Pennsylvanian surface laminated black shale. in the Illinois Basin (Smith, 1941; Horberg, Similar channels have been exposed in 1950). Similar valleys up to 140 m deep and up several other quarries in the Rock Island County to 32 km wide are known from other parts of area (Fig. 9). Plant fossils comparable to those the Illinois Basin (Bristol and Howard, 1971). of the Allied Stone Company quarry were As can be seen in several quarries and natural observed in the quarry at Cleveland, Henry exposures in this area, the unconformity surface County, Illinois, but these were poorly preserved in the Rock Island County area was relatively and recent quarrying operations have destroyed flat. A few years ago, one could walk on the the fossil-bearing deposits. unconformity, a rolling limestone surface with Pre-Pennsylvanian karst topography. A karst a maximum relief of 2 m that was exposed in topography apparently developed at the close the Allied Stone Company quarry; unfortun- of the Mississippian when the region was up- ately, it was destroyed by quarrying operations lifted and exposed to subaerial erosion. At that between 1975 and 1977. The flat upper surface time large areas of Silurian, Devonian, and of Devonian limestone can still be seen along Mississippian limestone strata were exposed the north and south walls of the Allied Stone on the western margin of the Illinois Basin.

Company quarry (Stop 4). Caves, filled with Pennsylvanian mud, silt, There are small knolls or "hills" on the and sand, are known in the area. Sinkholes limestone surface. One such knoll can be seen have been reported from both surface and sub- across the Rock River, north of the Allied surface data(McGinnis and Heigold, 1974). It is quarry (Fig. 5). This one is only 3 to 4 m high. not known whether the channels exposed in the Another one, a higher limestone hill, is exposed Allied Stone Company quarry drained into caves northeast of the bridge where US 67 crosses via sinkholes or into nearby deep valleys. PENNSYLVANIAN System

KEWANEE Group

SPOON CARBONDALE Formation

Composite Pi Section

MC CORMICK Group

CASEYVILLE ABBOTT Formation 7W rTTT7 Composite 1 Section ^kl.

cr 3

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3 rr

SILURIAN DEVONIAN System

NIAGARAN MIDDLE UPPER Series

! SWEETLAND. MARCUS RACINE WAPSIPINICON CEDAR VALLEY _\QREEK ForiTiation rTTT

j WWI . I • I I 1 hft|r- Composite \~ llllhil section fc m\& hn -rt-n-

Figure 4. Composite section of Pennsylvanian, Devonian and Upper Silurian strata in the Rock Island County area. Pennsylvanian section from Searight and Smith, 1969. 1979 Leary: Pennsylvania!! Flora, Rock Island County, Illinois

Paleobotanical background Several species of Megalopteris occur in the floras of western Illinois. These range from large Historical perspective. Several occurrences trilobed M. dawsoni (Hartt) Andrews (PI. 1, of Early Pennsylvanian (Late Namurian- Early Fig. 1) to smaller, pinnate (alethopteroid) forms Westphalian) plant fossils in western Illinois such as M. ovata Andrews (PI. 2, Fig. 1). Other have been known since the late 1800's (Worthen, specimens (PI. 2, Fig. 2) probably belonging to 1873). In 1907, David White (1908) examined the megalopteroid group, if not to the genus fossils from several localities in this area and Megalopteris, are similar to published figures published a brief report with a list of 14 fossil and descriptions of such genera as Neriopteris plant genera. Since that time, only sporadic (Newberry, 1873), Orthogoniopteris (Andrews, collecting has been done and no significant 1875) and Protoblechnum (Andrews, 1875). collections are known other than those at the Differences between these genera and their Illinois State Museum. The above, and broader relationships are not clear from the literature.

aspects of compression plant fossil studies in Lesleya foliage is similar to Megalopteris the area of the Illinois Basin, are reviewed by pinnules but consists of simple leaves (PI. 1, Phillips, Pfefferkorn, and Peppers (1973). Fig. 2). These leaves are greater than 30 cm

Description of significant "upland" taxa. long and 10 cm wide. The midvein is broad, The term "upland" has been used to designate though not as broad as that of Megalopteris; distinctive nonswamp floras, but the actual the lateral veins are curved and divide once or

paleoecology of such floras is not known. twice. Lesleya and Megalopteris are also The "upland" grew on soils derived from separated on the basis of epidermal structures limestone bedrock in western Illinois, and (Florin, 1933).

many were near stream banks and ultimately Mesocalamites (PI. 3, Fig. 1) is distinguished were deposited in stream channels with mini- from Calamites on the basis of the continuity mal transport. of ribs across the nodes. Calamites ribs alternate Because the "upland" flora includes a whereas some ribs of Mesocalamites alternate

number of genera which are unknown in coal and some are continuous. Mesocalamites is swamps and are not well known, some general largely restricted to the Namurian, rarely ex- descriptions and illustrations are given. tending into the Westphalian. Archaeocalamites,

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Figure 5. A limestone knoll exposed on the north side of the Rock River below the Watchtower, Black Hawk State Park. Sec. 14, T. 17 N., R. 2 W. E 2 o S H- c o o u c "5 3 > c QJ 4-* E c 3 CD <_> t/> D "5; O c c c CO o -C (J O

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777/ Last remaining undistrubed shale, 1984

Figure 7. Channel filled with fossil-bearing shale, siltstone, and sandstone in the Allied Stone Company quarry.

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Figure 8. Cross section of a channel. 10 o H

ROCK ISLAND COUNTY

Major known localities:

1. Wyoming Hill, Iowa

2. farm road

3. Allied Stone Company quarry

4. Black Hawk State Park

5. northeast jet. Rt. 67 and Rock River

6. Collinson quarry

7. Coal Valley

8. Carbon Cliff

9. Cleveland quarry 10. Port Byron 11. Slaymakers quarry 12. Midway Stone Co. quarry 13. Oakwood Golf Course Rd. 14. Sec. 3,T. 16N..R.4W.

sr?"^ Boundary of Pennsylvanian rocks (Generalized)

• Accessible

o Known from literature, unpublished records

Figure 9. Map of Rock Island County showing locations of exposures of the Devonian-Pennsylvanian unconformity and lower Pennsylvanian strata. 1979 Leary: Pennsylvanian Flora, Rock Island County, Illinois 11

an older form, has all ribs continuous across the Putnam County, Indiana nodes. The correlation of various species of Arnold (collected 1936, oral comm.) Mesocalamites/Calamites to species of foliage, Pictou, Canada Asterophyllites/Annularia, and fructifications, Bell (1940)

Calamostachys, is still not complete. West Virginia Lacoea (PI. 3, Fig. 5) is a cone consisting of White (1913) semicircular sporophylls which alternate on a Greene County, Indiana thick axis. Lacoea and similar, perhaps synony- Canright (1959), Wood (1963) mous, forms are known from a few localities Brown County, Illinois but in distant parts of the world: Holland Leary and Pfefferkorn (1977) (Hirmer, 1940, 1941); Belgium (Stockmansand Rock Island County, Illinois Williere, 1962); Czechoslovakia (Feistmantle, Leary (1974b, 1976, this guidebooklet) 1879); Germany (Hirmer, 1940); and China (Stockmans and Mathieu, 1957). Although In almost half of these localities, Megalop- Read (1946) suggested that Lacoea might be a teris occurs with a flora which is distinct from pteridosperm, specimens from Brown County, the common coal swamp flora. The Megalopteris Illinois, have permitted a reinterpretation; floras appear to contain greater percentages of

Lacoea is now considered a member of the pteridosperms and Cordaites and smaller per- Noeggerathiales (Leary, 1973). However, the centages of and lycopods than do Early broader natural affinities of the Noeggerathiales Pennsylvanian floras associated with coal are not known. This order has been treated as seams ("swamp floras") (Phillips et al., 1974). a separate group or loosely allied with either White (1931, p. 275-276) suggested that the Pteridopsida or Sphenopsida (Boureau, Megalopteris and Lesley a are unique to uplands 1964). The Noeggerathiales are well represented developed on carbonates. Recent studies by in the "upland" floras of western Illinois. Cross supports this concept (personal communi- Gulpenia (PI. 3, Fig. 2), another member of cation). The flora associated with Megalopteris the Noeggerathiales, is characterized by small, apparently grew on drier uplands underlain deeply lacerated leaves attached spirally to a by limestone. thin axis. In compression, Gulpenia bears a Environmental changes indicated in the superficial similarity to Sphenophyllum but the Allied flora. Studies of the paleoecological leaves clearly alternate. differences in Mississippian-Pennsylvanian floras

Megalopteris is not known to occur outside have shown that several paleoenvironments can North America (Arnold, 1934)* where it has be recognized (Peppers and Pfefferkorn, 1970, been reported from the following localities: for summary, also Remy and Remy, 1977). At

the top of the sequence in several channel fills

St. John, New Brunswick in the Allied quarry, the flora is characterized Dawson (1871), Stopes (1914) by an overwhelming abundance of Meso- Rushville, Ohio calamites with Lepidodendron and Psaronius;

Andrews (1875), Cross (1962) little else is present. This change in composition Port Byron, Illinois apparently represents a change from drier Lesquereux (1880) "upland" to wet lowland, or swamp, conditions Wyoming Hill, Iowa as stream channels were filled with sediment Noe(1925) and the water table correspondingly rose to Grand Ledge, Michigan near ground level. Tenchov (1976) described Arnold (1934) floral changes within a Carboniferous floral Saginaw, Michigan sequence of western Bulgaria and related these Arnold (1934) to continuous uplift of the basin. Changes in the elevation of the western margin of the Illinois Basin, relative to the central area of the

* A single fragment, from Britain reported as Megalopteris Basin, may have brought about changes in floral

(Arber, 1904) is now referred to Lesley a ( Leary, in press). composition in this area. 12 Guidebooklet: Illinois State Museum No. 4

Comparisons of "upland" floras. Recent probably not exactly the same, the differences studies of an Early Pennsylvanian flora from in generic composition probably reflect environ- Brown County, Illinois (Fig. 10) (Leary, 1973, mental differences rather than age differences. 1974a, 1974b, 1976; Leary and Pfefferkorn, The presence of a permanent body of water in 1977) have identified twenty -one genera of the channels apparently permitted the growth plants (Table 1). Among the most common are on the drier sites in Rock Island of genera (e.g., Lacoea, Sphenopteris, Cordaites, and Alethop- Lepidodendron and Mesocalamites) common teris. Megalopteris and Lesleya are also well to coal swamps. represented. Thirty-two genera of foliage, Comparison with European Floras. The fructifications, and stems have so far been flora exposed in the Allied Stone Company identified from the Allied Stone Company quarry is one of very few Namurian-age floras quarry (Table 1). The most abundant taxa at known in North America and provides a rare this site are Megalopteris, Lesleya, Samaropsis, opportunity for comparison with floras of Cordaites, and Cardiocarpus. similar age in Europe. Analysis of the Illinois The two floras (Table 1) have many genera "upland" floras enables us to make comparisons in common; differences are in the relative abun- with the "flozformend" (seam-forming) and dance of certain genera and presence or absence "flozfern" (distant from the seam) floras of the of certain others. Arborescent lycopods are European Namurian (Havlena, 1961). Numerous common in the nonswamp Rock Island flora similarities exist between these as well as signi- but very rare in the Brown County flora; only ficant differences. one determinable specimen and two fragmen- The greatest similarity appears to be with tary specimens of Lepidodendron have been the flora of the Ostrava-Karvina coal district of found at the latter site; Lepidophloios is absent Czechoslovakia (Sustra, 1928; Purkynova, from the Brown County locality and rare in the 1970). Here, Havlena (1970) recognized several Allied quarry site. Lycopods are the dominant microenvironments within the Namurian hygro- plants in most Lower and Middle Pennsylvanian phile environment in addition to a major coal swamp floras of the Illinois Basin (Phillips separation of the hygrophile and mesophile et al., 1974). Sphenopsids and Cordaites are environments. The mesophile ("upland") flora more abundant in parts of the Rock Island described by Havlena from the Ostrava-Karvina flora than in the Brown County flora; ferns are coal district was present only as fragments more common in the the Brown County flora. (Havlena, 1971, p. 245) whereas preservation

Although the ages of the two floras are of the plants in the Allied quarry is excellent. TABLE 1 LIST OF GENERA PRESENT AT THE LOCALITIES IN 13 BROWN AND ROCK ISLAND COUNTIES, ILLINOIS ABUNDANCE BROWN ROCK ISLAND GENERA COUNTY COUNTY Lycophytina Lepidodendron vr c Lepidophloios vr c Lepidophylloides f Lepidostrobus c Lepidostrobophyllum c Lepidocarpon c Stigmaria vr

Sphenophytina

Mesocalamites c c Asterophyllites c c Annularia vr Calamostachys c c

Sphenophyllum r

Filicophytina (Ferns)

Alloiopteris c vr

Dactylotheca r

Pteriodospermales

Alethopteris c r Sphenopteris a c

Lagenospermum vr ?

Telangium c r Megalopteris c a Lesleya c a Samaropsis c a PNeuropteris vr PMariopteris vr vr Whittleseya vr Aulacotheca vr

Rhodea r vr

Rhodeopteridium vr ?

Noeggerathiales

Lacoea a c Palaeopteridium c vr

Gulpenia r vr

Cordaitales

Cordaites c a

Cardiocarpus r c

Cordaianthus r

Artisia vr

Approximate abundance indicated by the following:

vr = very rare (1,2)

r = rare (3-5)

c = common (5-25

a = abundant (> 25)

Based upon 350 specimens from each locality. 14 Guidebooklet: Illinois State Museum No. 4

1 St. Louis, Mo.

ALLIED STONE 2 Golden Eagle CO. QUARRY

3 Brown County

4 Monmouth

5 Wyoming Hill, Iowa

6 Cleveland quarry

7 Midway quarry

12

8 Port Byron

9 La Salle County

10 Channahon

11 Kankakee

12 Putnam County, Ind.

13 Green County, Ind.

Figure 10. Map of reported localities of Early Pennsylvanian plant fossils on the margins of the Illinois (Eastern Interior) Basin.

Margin of Pennsylvanian strata Existing locality

Locality no longer accessible Spores only DESCRIPTIONS OF STOPS 15

Stop 1: Collinson Stone Company Quarry. The absence of brecciation and contorted bed- ding and the presence of abundant fossil forms SE SE NE NW Sec. 25, T. 17 No., R. 2 W., indicate that the seas were shallow, warm, and Milan 7.5' Quadrangle. open to free circulation. (Fossil collecting is best from the bench upward.) Caution: Do not approach the edge of the main At the close of the Devonian Period, when quarry. Look where you step and watch what seas withdrew from the midcontinent region, is above you on the upper level. strata in this area were subjected to erosion before Mississippian seas advanced across the Exposures of Pleistocene, Pennsylvanian, region. Although strata from this latter marine and Devonian strata can be seen in this quarry. advance have not been identified from this vicinity, chert fragments from the overlying Strata exposed by quarrying operations basal conglomerate of the Pennsylvanian Period here include slightly more than 30 m of middle contain fossil fragments indicative of the early Devonian limestones that are divided into about and middle portions of the Mississippian time, 10 m of Wapsipinicon Limestone in the deeper indicating that Mississippian sedimentation did part of the quarry and about 18 m of over- occur in this area. After Mississippian sedi- lying Cedar Valley Limestone (Fig. 11). The mentation ceased in this region, the land surface limestones composing these two formations again stood above sea level and was so exten- accumulated in warm shallow seas that covered sively eroded that all Mississippian rocks were the midcontinent region about 370 to 395 removed, except for the relatively insoluble million years ago. Although initially it would chert rubble. An uneven topography was devel- appear that conditions of deposition were oped; when shallow Early Pennsylvanian seas fairly consistent for long periods so that encroached upon the region, new sediments did thick limestones could accumulate, a closer not blanket all earlier strata. The higher hills examination of the Wapsipinicon shows that it and knobs of the older topography must have contains a considerable amount of brecciation. been low islands in the sea. Stream channels, The brecciation has been interpreted as being sinkholes, and caves which developed on and in the result of the removal of soluble beds, such the old eroded surface were the first to receive as gypsum or salt. Their removal then caused earliest Pennsylvanian sediments consisting of collapse of overlying limestone layers. Signifi- sands, silts, and muds that later formed sand- cantly, gypsum is currently being mined from stone, siltstone, and shale. A description of the Spring Grove Dolomite Member of the the topography of this surface can be found Wapsipinicon at Mediapolis, Iowa, less than 80 under BACKGROUND, page 5. km to the southwest. If removal of an evaporite Pennsylvanian deposits noted at this quarry bed were the actual cause of brecciation, it seem to be only sinkhole fillings, although as would appear that the formation accumulated the quarry is expanded farther south and west, in a restricted basin of deposition, such as more extensive Pennsylvanian strata should be a large lagoon. The water temperature and encountered. Because of slumping, the exact salinity may have been high because there was relations are not always visible; so it is possible limited open circulation with the deeper oceans that the Pennsylvanian strata in the south- nearby and conditions were right for the western part of the quarry highwall could be deposition of evaporite materials. The scarcity located in a shallow stream channel on the of fossil forms indicates that the water did old surface. not support abundant life. Since brecciation Overburden exposed along the south- and contorted bedding is restricted to the western part of the quarry reveals possible Wapsipinicon, removal of the soluble evaporite Kansan and Yarmouthian deposits beneath materials must have preceded the deposition of Illinois, Sangamonian, Wisconsinan, and Holo- the overlying Cedar Valley. cene materials.* The Cedar Valley Limestone must have been deposited under much different conditions. Modified from the I.S.G.S. Milan Guidebook, 1974. 16 Guidebooklet: Illinois State Museum No. 4

HELM Sandstone, sandy greenish shale in solution cavities. Limestone, gray to buff. Cystodictya , Stropheodonta ,

Spirifer . Bioherm with Hexagonaria , Cystphyl lum ,

Favosites , Cladopora , and Atrypa common

Limestone, gray to buff, dolomitic, with abundant crinoids and some micro-conglomerate.

Many stromatoperoids and bryozoa with fossils

1 isted above. Limestone, greenish-gray to buffish-gray, fine grained, argillaceous, massive, weathers readily, oblique joints prominent.

Relatively few fossils.

15.8m

Fossils present but not abundant.

Limestone, greenish-gray to grayish-brown, fine grained, argillaceous to shaley partings, weathers easily,

1 fossi iferous. Atrypa , Strophodonta , Leptostrophia ,

Chonetes , Spirifer , Schizophoria , Pentamerel lo ,

He! iophyllum , Cystiphyllum , Favosites , Productel la ,

also crinoidal . Limestone, grayish-brown, subl ithographic to fine grained, weathers with brown splotches, very fossil iferous.

Astreospongia , Stromatoporoids, Hel iophyllum , Favosites .

Limestone, very light gray, lithographic to subl itho- graphic, brecciated, pyritic sandy streaks. Grades down to brownish-gray lithographic limestone.

Limestone, very light gray to light gray, lithographic to subl ithographic, hard, brecciated to bedded.

Limestone, brown to brownish-gray, subl ithographic with thin light-colored laminae.

Limestone, brownish-gray, subl ithographic, fractures often calcite filled, some pyrite.

Limestone, gray, lithographic, contorted bedding, brecciated.

Limestone, light buff, very fine grained, dolomitic, wavy bedded, mostly thin bedded and slabby.

Limestone, blue-gray to brownish-gray, medium to coarse grained, thin dark wavy laminae at top, locally brecciated; dolomite in lower part, cavities numerous with crystals of pyrite, calcite, and quartz.

Figure 11. Stop 1. Collinson Stone Company quarry stratigraphic section. NW Sec. 24, T. 17 N., R. 2W., Rock Island County, Illinois. From 31st Tri-State guidebook, Edmund and Anderson, 1967. 1979 Leary: Pennsylvanian Flora, Rock Island County, Illinois 17

Stop 2: Borrow pit east side of US 67. easily) from Black Hawk State Park. The largest hill is exposed at Stop 2. The easternmost "hill" SW NE SW Sec. 14, T. 17 N., R. 2 W., is approximately 3 m high and slightly irregular Milan 7.5' Quadrangle. in form. The upper portion of the limestone is iron stained, with a sideridic top. Because the Devonian, Pennsylvanian, and Pleistocene "hill" is essentially exposed only in cross strata are exposed in this locality. section, the north-south extent is unknown. The "hill" is overlain by 14 m of shale with The borrow pit exposes strata of Pennsyl- some thin sandstone beds. Above the shale is a vanian age that are older than those seen at Stop thick, cross-bedded sandstone. Both the shale 1. Above a gray underclay in the background is and sandstone are unfossiliferous at this point. a 20 to 26 cm coal bed that is one of the oldest About 100 m to the west is possibly another coals known in this part of the state. A gray limestone "hill." This "'hill" appears from silty shale lies above the coal. The shale is either the distance to be lower than the previously locally nearly cut out by a sandstone channel described one because the upper portion is that crosses the area or is replaced by a sand- weathered to a thin-bedded state resembling stone facies to the south (see Fig. 12). The large shale and thin-bedded sandstone. Less iron covered area near the center of the exposure appears to be present here than at the eastern obscures an important part of the section. The "hill." This second "hill" is also overlain by southern half of the east wall of the pit and the shale; but weathering, slumping, and vegetation floor of the pit reveal Pennsylvanian strata dip- obscure details of the section. ping to the north and truncated to an even, The top of the westernmost hill, 100 m nearly horizontal surface upon which Illinoian east of US 67 (Stop 2), is approximately 10 m till was deposited. The till is overlain by above the Rock River. It is heavily iron stained Wisconsinan silts and thick loess. Along the and in part replaced by iron. Because excavation southern part of the exposure, a Pleistocene has only exposed the top of this hill, its extent channel was cut through Illinoian till to the is not known. bedrock surface and was later filled with

Wisconsinan silts. Beneath this channel, bed- rock strata have been considerably disturbed. Stop 3: (Lunch) Black Hawk State Park. Although a slight possibility exists that the Pleistocene channel had something to do with NE NW SE Sec. 14, T. 17 N., R. 2 W., the disturbance, the location of the two features Milan 7.5' Quadrangle. is coincidental.* The Devonian -Pennsylvanian unconformity Devonian and Pennsylvanian strata are ex- is exposed at several points along the north side posed along the Rock River below and to the of the Rock River for nearly 1 km east of Stop east of Watch Tower Inn. 2 (Section 14, T. 17 N., R. 2 W.). In addition to the exposure at this point, a second good (The following discussion is taken from the exposure of basal Pennsylvanian sediments now 31st Tri-State Geological Guidebook: The Mis- exists on the bluff below the lodge in Black sissippi River Arch, by R.W. Edmund and R.C. Hawk State Park (Stop 3, Fig. 13). Anderson, Augustana College, 1967). Although the Pennsylvanian -Devonian con- tact is approximately at river level, small knobs Black Hawk State Park preserves the or "hills" of Devonian limestone are exposed in most scenic portion of the lands once cross section along the Rock River. One of occupied by Saukenuk, the largest these is shown in Figure 5 and can be seen from Indian village in the Upper Mississippi Vandruff Island. It can be reached (though not Valley. It was here that Chief Black Hawk and his band of Sauk and Fox came in conflict with the territorial Modified from the I.S.G.S. Milan Guidebook, 1974. claims of the white man in the years 18 Guidebooklet: Illinois State Museum No. 4

&

o a o

0/ si tS'

a> •a

w8

S3

i-H

OJD

CO

Fig. 12. Stop 2. Borrow pit, east side of U.S. 67. SW NE SW Sec. 14, T. 17 N., R. 2 W., Milan quadrangle, Rock Island County, Illinois. 1979 Leary: Pennsylvanian Flora, Rock Island County, Illinois 19

Loess, cream to light buff, silt and clay with calcareous concretions.

Till and glacial drift.

Sandstone, light brown to tan, medium to fine grained with irregular streaks of carbon- aceous shale.

Shale, gray, fissile, silty. Coal, impure, shale partings.

Shale, dark gray, with silty lenses and thin streaks of sand. Grades from fissile shale in thin beds to blocky claystone in rather massive beds.

Mery few fragments of plant fossils.

Figure 13. Stop 3. Stratigraphic section at Black Hawk State Park, Rock Island, Illinois. 20 Guidebooklet: Illinois State Museum No. 4

preceding the Black Hawk War of 1832. the spore flora in the coal in this section and

The area is rich in Indian lore, and some determined that the coal is a unit in the Casey- of it can be savored in the Black Hawk ville Formation of the McCormick Group, being Museum on the "Watch Tower." older than the Reynoldsburg Coal Member and From the Watch Tower, a high prom- younger than the Gentry Coal Member. This ontory on the north bluffs of the Rock particular coal has a number of spores not found River, many of the features of the land- in other Illinois coals. It seems likely that this scape in the Rock Island area can be seen. coal is of limited extent and probably was

This area is characterized by flat upland deposited in a small, discontinous basin, as prairies greatly dissected along the major along an upper delta plain or abandoned stream streams and by broad valleys bounded channel. The overlying Rock Island (No. 1) by steep bluffs and occupied by sizable Coal is likewise discontinuous and is thought to streams such as the Rock River. have been deposited in an estuary (Moody,

Chief Black Hawk is reported to have unpublished thesis 1959; Wanless, 1975). said, "At the Watch Tower, which was frequently visited by me alone I could sit and smoke my pipe and look with Stop 4. Allied Stone Company Quarry. wonder and pleasure at the grand scenes that were presented by the sun's rays, NW SW SE Sec. 14, T. 17 N., R. 2 W., even across the mighty water." The Milan 7.5' Quadrangle. quarry on Vandruffs Island makes it impossible for us to view this scene with Devonian, Pennsylvanian, and Pleistocene the same serenity as did Black Hawk, strata are exposed in this quarry (Fig. 14). This

but it has provided some very fine stop affords a better opportunity to study the exposures of the Devonian Cedar Valley lower part of the Wapsipinicon Limestone limestone (and fossil-bearing basal (Middle Devonian) than Stop 1. As noted previ- Pennsylvanian, ed.). This will be our ously, the Wapsipinicon contains only scattered

first stop upon leaving the park. fossils. The Solon Limestone Member is the only Within the confines of Black Hawk portion of the overlying Cedar Valley Limestone State Park the fossiliferous Cedar present here. Valley limestone, Devonian, crops out along the north bank of the Rock River, Here the Allied Stone Company is quarrying exposing approximately ten feet of Cedar Valley and Wapsipinicon limestones of section above water level. The Devonian Middle Devonian age (Fig. 14) and crushing the beds here are overlain by sandy carbon- stone for road and general construction stone. aceous shale and gray shale totaling As we enter we will pass the field office, scales approximately 40 feet of strata, Pennsyl- for weighing trucks loaded with crushed stone, vanian in age. Fragments of plant fossils piles of crushed stone of various sizes, the have been observed directly above the crushing plant, and maintenance shops. The Devonian in fine silty sandstones and quarry itself is nearly 1.6 km long, 0.5 km wide, dark gray shales. The Pennsylvanian and up to to 12 m deep. Because this is an active shales are overlain by about 50 feet of quarry, and the plant fossils occur within the Pleistocene loess (Fig. 13). overburden, locations of fossil -bearing strata The Pennsylvanian rocks at Black change from year to year. Over large areas of the Hawk State Park are representative of quarry the Devonian limestone was immediately the exposures found on the south side overlain by outwash as a result of erosion and of Rock Island and Moline, adjacent to deposition during the Pleistocene. Few occur- the Rock River. rences of Pennsylvanian strata can be observed. Probably the most striking feature of this

Dr. Russel Peppers, paleobotanist at the quarry is the presence of a number of channels Illinois State Geological Survey, has examined and caves that developed in Devonian strata. 1979 Leary: Pennsylvanian Flora, Rock Island County, Illinois 21

Loess and very thin glacial drift.

Shale, black to dark gray, fissile to blocky with interbedded thin sandstones. Grades down to greenish gray sandy shales and light colored pyritic sandstones.

Limestone, buff, fine to medium grained, numerous brachiopods.

Limestone, very light gray, subl i thographic to lithographic, very brecciated, green clay and shale streaks, graded downward to greenish gray and light brownish gray limestone, hard and brittle, numerous wavy bands and irregular thin beds.

Cave fillings common with fine to medium angular sand interbedded with greenish clay and shale. Fragments of plants and much pyrite is common.

Limestone, very light gray to very light buff,

dolomitic, lithographic to subl i thographic, styolitic, weathers to thin slabs, some brecciation

Limestone, brownish to bluish gray and dark colored, fine to coarsely crystalline with thin dark shale laminae, brecciated with shale and limestone matrix.

LTJ\ Dolomite, brownish-gray, fine grained

Figure 14. Stop 4. Allied Stone Company quarry, stratigraphic section. SE'/4, Sec. 14, T. 17 N., R. 2 W, Rock Island County, Illinois. 22 Guidebooklet: Illinois State Museum No. 4

These features must have formed after the end Collapse sinks are generally deep and steep of Mississippian deposition because they contain walled. A second type of sinkhole is called a no sediments of Mississippian age. On the other doline, in which solution takes place along hand, they must have existed before widespread joints beneath the soil mantle so that the Pennsylvanian sedimentation began in this area, surface is gradually lowered without collapsing for the sediments filling them are among some the rock mass. They do not require the presence of the oldest-known Pennsylvanian strata in the of large subterranean cavities, most of them state. These Pennsylvanian rocks occur strati- being shallow, saucer-shaped depressions. Their graphically lower than the Pennsylvanian layers depth is controlled by the depth of the water at a neighboring borrow pit (Stop 2) and across table at the time of their formation. Both types the Rock River at Black Hawk State Park. of sinks are generally present in a sinkhole area, The solution features strongly suggest that but dolines generally are more common.* this area was topographically high— part of the The basal Pennsylvanian deposits in this Mississippi River Arch—when they were formed. quarry have been the major source of plant fos- Four conditions contribute to the development sils representing Early Pennsylvanian "upland" of such large numbers of sinkholes: First, sol- floras in Illinois. Although now largely removed uble rock, preferably limestone, must occur at by quarrying operations, some fossil-bearing or near the surface and should be flat-lying, channel deposits can be seen and plant fossils or nearly so. Second, and one of the most can be collected. important factors, the limestone should be The plant fossils occur in the shale and dense, abundantly jointed, and preferably mudstone which fill elongate depressions thinly bedded. The limestone should not be (channels) eroded in the Middle Devonian Cedar porous; if it is, rainwater will be absorbed, Valley Limestone. The channels are 4 to 6 m moving through the whole body of the rock deep and 8 to 20 m wide. One channel can be rather than being concentrated along joints and seen in cross section at the top of the north wall bedding planes. Third, major valleys must be at about mid-quarry. As of late 1978 they can entrenched below the uplands, serving as best be seen at the west end of the quarry where outlets toward which the ground water can several channels are visible in both cross section move in the subsurface. Fourth, there must be and horizontally (see diagram, Fig. 8). During ample rainfall. the autumn of 1978 the best plant fossil col- Sinkholes form in two ways. Collapse sinks, lecting was in the channel nearest the large gravel known as ponors, are caused by the collapse of pile (arrow on Fig. 7). The only Pennsylvanian the roofs of caves that lie near the surface. animal fossils yet discovered here, a scorpion Caves were initially formed above the zone of (Leary, in press) and a single fish scale, were saturation by ground water percolating down- found at this site in October, 1977. ward (such water is called vadose water). Roof collapse followed uplift of the area and subse- quent entrenchment of major drainage channels. Modified from the I.S.G.S. Milan Guidebook, 1974. CARBONIFEROUS DEPOSITION IN THE ILLINOIS BASIN 23

The following section on Mississippian de- generally extended out into the sea as a bird-foot position is taken from Illinois State Geological delta, and the shoreline across the basin area Survey Report of Investigations 216: Classifi- may have been convex more often than concave.

. . . . static. Its cation of Geneuievian and Chesterian . . Rocks The shoreline was not position of Illinois (1963) by D.H. Swann, pp. 11-16. oscillated through a range of perhaps 600 to The section on Pennsylvanian deposition is 1,000 or more miles (970-1,600 km). At times taken from Illinois State Geological Survey it was so far south that land conditions existed publications. throughout the present area of the Illinois Basin. At other times it was so far north that

there is no suggestion of near-shore environment MISSISSIPPIAN DEPOSITION in the sediments still preserved. This migration of the shoreline and of the accompanying sedi- During the Mississippian Period, the Illinois mentation belts determined the composition Basin was a slowly subsiding region with a and position of Genevievian and Chesterian vague north-south structural axis. It was rock bodies. flanked by structurally neutral regions to the Lateral shifts in the course of the Michigan east and west, corresponding to the present River also influenced the placement of the rock Cincinnati and Ozark arches. These neighboring bodies. At times the river brought its load elements contributed insignificant amounts of of sediment to the eastern edge of the basin, sediment to the basin. Instead, the basin was at times to the center, and at times to the west- filled by locally precipitated carbonate and by ern edge. This lateral shifting occurred within a mud and sand eroded from highland areas far range of about 200 miles (320 km). The Cincin- to the northeast in the eastern part of the nati and Ozark areas did not themselves provide Canadian Shield and perhaps the northeastward sediments, but, rather, the Michigan River extension of the Appalachians. This sediment tended to avoid those relatively positive areas was brought to the Illinois region by a major in favor of the down-warped basin axis. river system, which it will be convenient to call Sedimentation belts during this time were the Michigan River (Fig. 15) because it crossed not symmetrical with respect to the mouth of the present state of Michigan from north to the Michigan River. They were distorted by the south or northeast to southwest .... position of the river relative to the Ozark and The Michigan River delivered much sediment Cincinnati shoal areas, but of greater importance to the Illinois region during early Mississippian was sea current or drift to the northwest. This time. However, an advance of the sea midway carried off most of the mud contributed by the in the Mississippian Period prevented sand and river, narrowing the shale belt east of the river mud from reaching the area during deposition mouth and broadening it west of the mouth. of the St. Louis Limestone. Genevievian time Facies and isopach maps of individual units began with the lowering of sea level and the show several times as much shale west of the alternating deposition of shallow-water carbon- locus of sand deposition as east of it. The facies ate and clastic units in a pattern that persisted maps of the entire Chesterian . . . show max- throughout the rest of the Mississippian. About imum sandstone deposition in a northeast- a fourth of the fill of the basin during the late southwest belt that bisects the basin. The total

Mississippian was carbonate, another fourth thickness of limestone is greatest along the was sand, and the remainder was mud carried southern border of the basin and is relatively down by the Michigan River. constant along that entire border. The pro-

Thickness, facies, and crossbedding ... in- portion of limestone, however, is much higher dicate the existence of a regional slope to the at the eastern end than along the rest of the southwest, perpendicular to the prevailing north southern border, because little mud was carried 65° west trend of the shorelines. The Illinois southeastward against the prevailing sea current. Basin, although developing structurally during Instead, the mud was carried to the northwest this time, was not an embayment of the interior and the highest proportion of shale is found in sea. Indeed, the mouth of the Michigan River the northwestern part of the basin. 24 Guidebooklet: Illinois State Museum No. 4

\ WISCONSIN ILLINOIS

O CINCINNATI OZARK ^ KENTUCKY SHOAL SHOAL \)

( ^> A J -J y 50 Miles j W \ i i J ~d-

Figure 15. Paleogeography at an intermediate stage during Chesterian (Mississippian) sedimentation. From Swann, 1963. 1979 Leary: Pennsylvanian Flora, Rock Island County, Illinois 25

Genevievian and Chesterian seas generally similar to those that existed during Chesterian extended from the Illinois Basin eastward across (late Mississippian) time. A river system flowed the Cincinnati Shoal area and the Appalachian south westward across a swampy lowland, Basin. Little terrigenous sediment reached the carrying mud and sand from highlands in the Cincinnati Shoal area from either the west or northeast. A great delta was built out into the the east, and the section consists of thin lime- shallow sea. As the lowland stood only a few stone units representing all or most of the feet above sea level, only slight changes in rela- major cycles. The proportion of inorganically tive sea level caused great shifts in the position precipitated limestone is relatively high and the of the shoreline. waters over the shoal area were commonly Throughout Pennsylvanian time the Illinois hypersaline .... Erosion of the shoal area at Basin continued to subside while the delta front times is indicated by the presence of conodonts shifted owing to worldwide sea level changes, erorded from the St. Louis Limestone and intermittent subsidence of the basin, and varia- redeposited in the lower part of the Gasper tions in the amounts of sediment carried seaward Limestone at the southeast corner of the from the land. These alternations between Illinois Basin .... marine and nonmarine conditions were more The shoal area included regions somewhat frequent than those during pre-Pennsylvanian east of the present Cincinnati axis and extended time, and they produced striking lithologic from Ohio, and probably southeastern Indiana, variations in the Pennsylvanian rocks. through central and east-central Kentucky and Conditions at various places on the shallow Tennessee into Alabama .... sea floor favored the deposition of sandstone, Toward the west, the seaway was commonly limestone, or shale. Sandstone was deposited continuous between the Illinois Basin and near the mouths of distributary channels. These Central Iowa, although only the record of sands were reworked by waves and spread as Genevievian and earliest Chesterian is still thin sheets near the shore. The shales were preserved. The seas generally extended from the deposited in quiet-water areas— in delta bays Illinois and Black Warrior regions into the between distributaries, in lagoons behind barrier Arkansas Valley region, and the presence of bars, and in deeper water beyond the near-shore Chesterian outliers high in the Ozarks indicates zone of sand deposition. Most sediments now that at times the Ozark area was covered. Al- recognized as limestones, which are formed from though the sea was continuous into the Ouachita the accumulation of limey parts of plants and region, detailed correlation of the Illinois sedi- animals, were laid down in areas where only ments with the geosynclinal deposits of this minor amounts of sand and mud were being de- area is difficult. posited. Therefore, the areas of sandstone, shale, and limestone deposition continually changed as the position of the shoreline changed and as Pennsylvanian Deposition the delta distributaries extended seaward or shifted their positions laterally along the shore. At the close of the Mississippian Period, Nonmarine sandstones, shales, and lime- about 310 million years ago, the Mississippian stones were deposited on the deltaic lowland sea withdrew from the Midcontinent region. A bordering the sea. The nonmarine sandstones long interval of erosion took place early in were deposited in distributary channels, in Pennsylvanian time and removed hundreds of river channels, and on the broad floodplains of feet of the pre-Pennsylvanian strata, completely the rivers. Some sand bodies, 100 or more feet stripping them away and cutting into older rocks thick (30 m), were deposited in channels that cut over large areas of the Midwest. An ancient through many of the underlying rock units. The river system cut deep channels into the bedrock shales were deposited mainly on floodplains. surface. Erosion was interrupted by the invasion Freshwater limestones and some shales were de- of the Morrowan (early Pennsylvanian) sea. posited locally in freshwater lakes and swamps. Depositional conditions in the Illinois Basin The coals were formed by the accumulation of during the Pennsylvanian Period were somewhat plant material, usually where it grew, beneath 26 Guidebooklet: Illinois State Museum No. 4

the quiet waters of extensive swamps that pre- coals. Many underclays contain plant roots vailed for long intervals on the emergent delta and rootlets that appear to be in their original lowland. Lush forest vegetation, which thrived places. The formation of coal marked the end in the warm, moist Pennsylvanian climate, of the nonmarine portion of the depositional covered the region. The origin of the under- cycle, for resubmergence of the borderlands clays beneath the coals is not precisely known, by the sea interrupted nonmarine deposition, but they were probably deposited in the swamps and marine sediments were then laid down as slackwater muds before the formation of the over the coal. REFERENCES CITED

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p. 413-426. Havlena, V. 1961 Die flonznahe und flozfremde Flora des Arber, E.A. oberschlesischen Namurs A und B. Palaeon- 1904 Culm Measures of northwest Devon and the tographica Abt. B, Vol. 108, p. 22-38. age of the coal beds. Phil. Trans. Royal Soc. London, B. 197, p. 307. 1970 Ecology and mode of deposition of the macroflora in cyclothems of the Ostrava Arnold, C.A. Formation (Namurian A). Vestnik Ustred- 1934 A preliminary study of the fossil flora of niho ustavu geologickeno, 45, p. 291-294. the Michigan Basin. Museum of Paleon- tology, University of Michigan, 4(11), 1971 Die zeitgleichen Floren des Europaischen

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Edmund, R.W., and R.C. Anderson 1974b Two early Pennsylvanian floras of western 1967 The Mississippi River Arch, 31st Annual Tri- Illinois. Illinois State Academy of Science State field conference, Augustana College, Transactions, vol. 67, no. 4, p. 430-440,

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Leary, R.L., and H.W. Pfefferkorn Read, C.B. 1977 An Early Pennsylvanian flora with Mega- 1946 A Pennsylvanian florule from the Forkston lopteris and Noeggerathiales from west- Coal in the Dutch Mountain Outlier

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Phillips, T.L., A.B. Kunz, and D.J. Mickish Steinkohlenreviers, I, p. 385-484, 75 pi. 1974 Paleobotany of petrified peat (coal balls) Ostrava. from the Herrin (No. 6) Coal Member of the Illinois Basin. Geol. Soc. Amer., Abst. Swann, D.H.

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Leary, R.L. 1979 Early Pennsylvanian upland compression

flora, Rock Island County, Illinois: Illi- nois State Museum Guidebooklet Series

4. 42 p.

Leary, R.L. 1980 Labhscurpio a/liedensis, sen. et sp. nov: a new Carboniferous scorpion from Rock Island County, Illinois: Journal of Paleon-

tology, v. 54, no. 6, p. 1255-1257.

Leary, R.L. 1981 Early Pennsylvanian geology and paleo- botany of the Rock Island County,

Illinois, area. Part 1: Geology: Illinois State Museum Reports of Investigation 37, 88 p.

Phillips, T.L., and R.A. Peppers 1984 Changing patterns of Pennsylvanian coal- swamp vegetation and implications of climatic control on coal occurrence: International Journal of Coal Geology,

v. 3, p. 205-255. 30 PLATES

Plate 1

Fig. 1. Megalopteris dawsoni x V2 Fig. 2. Lesleya cheimarosa x V2 31

Plate 2

Fig. 1. Megalopteris ovata xl Fig. 2. Megalopteris ovata ? xl 32 Leary: Pennsylvanian Flora, Rock Island County, Illinois

Plate 3

Fig. 1. Mesocalamites sp. xl Fig. 5. Lacoea seriata xl

Fig. 2. Gulpenia sp. x2 Fig. 6. Sphenopteris sp. xl

Fig. 3. Samaropsis new berry i xl Fig. 7. Mariopteris sp. xl

Fig. 4. Sphenophyllum tennerrimum xl Guidebooklet: Illinois State Museum 33

Plate 4

Fig. 1. Palaeopteridium reussii x2 Fig. 4. Sphenophyllum cuneifolium ? x2

Fig. 2. Sphenopteris sp. xl Fig. 5. Samaropsis newberryi xl

Fig. 3. Sphenopteris sp. xl 34 Leary: Pennsylvanian Flora, Rock Island County, Illinois

Plate 5

Fig. 1. Lepidostrobus sp. x% Fig. 5. Sphenophy Hum sp. xl

Fig. 2. Lepidodendron sp. xl Fig. 6. Triletes auritus tetrad x5

Fig. 3. Lepidocarpon sp. x2 Fig. 7. Triletes auritus tetrad xl5

Fig. 4. Lepidocarpon sp. x2 NOTES 35 36 SKETCHES OF LOWER PENNSYLVANIAN PLANT FOSSILS OF WESTERN ILLINOIS

X 1/2"1

Lesleya

Megalopteris Guidebooklet: Illinois State Museum 37 38 Leary: Pennsylvanian Flora, Rock Island County, Illinois

ttttut *W

^3 ^ x1

Cordaianthus

^x2 Calamostachys x1

'<{

tl'"•70Wtt

I

Mesocalamites

(Catamites) x1 -x.25

I <.

i\

^VWW

base x1 Lacoea

Cordaites

x1 - x.5 Guidebooklet: Dlinois State Museum 39

Cordaicarpus

Samaropsis

"seeds"

Telangium W0 & x1

Aulacotheca

x1 x1 -2 ? Aphlebia

Whittleseya

M H

Gulpenia

Rhodeop teridium ? Rhodeopteridium 40 Leary: Pennsylvanian Flora, Rock Island County, Illinois

Lepidocarpon

Lepidodendron

Sphenopteris

Aleth op ten's Neurop ten's ?

Lepidostrobus < m x2

Sphenophyllum

x2 A x5 Lepidophyllum

? Megasporangium Guidebooklet: Illinois State Museum 41

Alloiopteris

x1

Cyclopteris

V

mm mmr, mi

xl 42

ACKNOWLEDGEMENTS

Many people have helped in the preparation of this field trip. The organizers of the International Carboniferous Congress have cooperated with the author in planning and publicizing the trip. Dr. Tom L. Phillips, as chairman in charge of one-day field trips, has helped with arrangements. Roy Nelson, supervisor of the Allied Stone Company quarry, Richard DeSchepper, supervisor of the Collinson Stone Company quarry, and Howard Dixon, geologist with Moline Consumers, made access to the quarries possible. Special thanks go to them for their continued cooperation without which research at these sites would be impossible.

Parts of the text and some of the illustrations used in this guide were taken from guidebooks of the Illinois State Geological Survey and the guidebook for the 31st Tri-State Field Conference (1967). The author appreciates permission to use this information. The author also gratefully acknowledges the assistance, comments, and suggestions given by staff members of the Illinois State Geological Survey and faculty at the University of Illinois and at Augustana College.