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 d from the appropriate company PRIOR to entering the qu ite well in advance of any planned visit to assure'cornpletion of necessary arrangements before the selected date. Write to: (Allied Stone Company quarry) (Collinslon Stone Cbmpany quarry) Mr. James 0. Ellis, President Mr. Richard DeShepper Moline Consumers 3115 23rd Avenue 313 16th Street dine, EL 61265 Moline, IL 61265 UNITED STATES DEPARTMENT OF THE ARMY ILLINOIS-IOWA CORPS OF ENGINEERS 15 MINUTE SERIES (TOPOGRAPHIC) 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 ck Island County, and one from compression flora. The itinerary repeats a unty to the south, have been referred trip originally offered during the Ninth Inter- to as an ""upland7'flora. national Congress of Carboniferous Stratig- This field trip will give geologists and raphy and Geology (IX-KC) 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- (1 98 1). Additional information concerning tions may have been thinner than equivalent Labviscorpio alliedensis is also available ( Leary , strata in the deep part of the basin, or in fact, eppers (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 Silurian to Devonian. 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 nnsylvanian paleovalleys in the Rock examined only by means of drilling records, 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 plant fossils in the Rock of a channel. area. The fossils occur in rocks immediately eppers 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. Me believes Wapsipinicon Limestones: Middle Devonian a1 communication) that this Series). The composition of the fossil plant stphalian A in age. 2 Guidebsokiet : Illinois State No. 4 Figure 1. Geologic map of the Rock Island County area. Circled numbers are stops. Base map from Edmund and Anderson, 1967, Leary : Pennsylvanian Flora, Rock Island County, Illinois 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. Pa~er853.1 1 \ f --- - 71e~irf I \A/-- L - Pre-Pennsylvanian Paleogeologic Map Surface and pre-glacial boundaries I Q - I t. L> &:- -, Pre-Pennsylvanian boundaries N 8; 6,;" I Data from Illinois and Iowa Geological surveys. -1 SCOTT ) Scale 1:500,000 R.W. Edmund, 1967 rth of Vandmff Island and the s hill is about PO m above the major portion sf conformity here. from Ordovician t ill will be seen at Pennsylvanian strata are primady carbonates and had been exposed to sub are present, some deep valleys were also Along the western margin sylvanian rocks overlie rocks in the central part ee map, Fig. 6). in the northwest (Reinemftse . Silurian and Ordovician Pennsylvanian along the northern margin (see geologic maps, Figs. 2, 3). The relevant portion of the stratigraphic sequence in the Rock Island County area is quarry and the Cleveland quarry. The primary illustrated in Figure 4. The major unconfomity trend of these channels was east-west (Fig. 7), between the Devonian Cedar Vdley Limestone ut the locations were apparently controlled by and basal Pennsylvanian indicates a long peri jointing in the limestone. The exact nature of of erosion prior to earliest Pennsylvanian s not been determined. mentation. Because strata as young as the hese channels were 4 to 6 m deep and 8 Louis Limestone (Valmeyeran = basal Visean) (Fig. 8). They were filled with occur beneath the unconfomity to the south, e, and occasional. lenses or thin, it is believed that the period of erosion came in ers of sandstone. Occasional Late Mississippian/Early Pennsylvanian (at the asses of pyrite are also present base of the European zed plant axes. The shale and Pre-Pennsylvanian mudstone are almost exclusively gray except are known to have drained eastward and south- h is sometimes thinly eastward across the pre-Pennsyl in the Illinois Basin (Smith, f 1950). Similar valleys up to 140 m deep and up es in the Rock Island County to 32 krn wide are known from other parts of fossils comparable to those the Illinois Basin (Bristol and Howard, 197%). pany quarry were As can be seen in several quarries and natural at Cleveland, Henry exposures in this area, the unconformity surface were poorly preserved in the Rock Island County area was relatively ons have destroyed flat. A few years ago, one could walk on the unconformity , a rolling limestone surface a maximum relief of 2 m that was expos the Allied Stone Company he region was up- ately, it was destroyed by quar between 1975 and 1977. The flat upper surface , Devonian, and of Devonian limestone can still be seen dong the north and south walls o Company quarry (Stop 4). There are small knolls limestone surface. One such across the Rock River, no gold, 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 lirnestone rained into caves northeast of the bridge where Formotion I 1 Composite 1 Section i I r MC CORMICK Group I I I I SILURIAN DEVONIAN 1 System 1 \ I NIAGARAN MIDDLE UPPER Serles 1 MARCUS RACINE 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 : Pennsylvanian Flora, Rock Island County, 7 of Megalop teris occur in the limois. These range from large . daeusorzi (K1art-B;) Andrews (Pl. 1, Fig. 1)to smaller, pi ake (dethopteroid) forms Westphalian) plant such as M ovata A ews (PI. 2, Fig. 1).Other specimens (PI. 2, Fig. 2) probably belonging to 1873). In 1907, D the megalopteroid group, if not to the genus Megalop teris, are similar to published figures published a brief report with a list of 14 fossii s of such genera as Neriopteris plant genera. Since that time, only spora 3 ), Orthsgonisp tei-is (Andrews, collecting has been done and no signlfic toblechnurn (Andrews, 1875). collections ae known other than those at the Differences between these genera and their seum, The above, and bl~o relationships are not clear from the literature. pression plantfossil strdie Lesleya foliage is similar to Megalopteris the area of the Illinois but consists of simple leaves (Pl. 1, Phillips, Pfefferkom, and se leaves are greater than 30 cm em wide. The midvein is broad, though not as road as that of Megalopteris; the lateral veins are paleoecology of such twice. Lesleya an many were near stre , Fig. 1)is distinguished were deposited in stream channels with mini- mal transport. Because the "upland" flora indu number of genera which are un~knowuain coal. swamps and are not well known, some general descriptions and illustrations are given?. Figure 5. A limestone knoll exposed on the north side of the Rock River below the Watchtower, lack Hawk State Park. Sec. 64, T. 17 N,,R. 2 Channel removed by quarrying vm Last remaining undistrubed shale, 1984 Figure 7. Channel filled with fossil-bearing shale, siltstone, and sandstone in the Allied Stone Company quarry. Figure 8. Cross section of a channel. ROCK ISLAND COUNTY Major known localities: 1.