82 



ILLINOIS STATE GEOLOGICAL SURVEY 



Cropp (1956) concluded that the coals of 

 the Black Creek, Mary Lee, and Pratt 

 Groups are of the lower Pottsville. It is 

 possible that they are older than the lower- 

 most Pennsylvanian coals of Illinois. 



Summary 



Although large spores are very abundant 

 in upper Mississippian rocks, only two gen- 

 era, Cystosporites and Triletes, are well rep- 

 resented. In contrast, even the lower coals 

 in the Caseyville Group of the Pennsyl- 

 vanian contain spores referable to five gen- 

 era: Cystosporites, Triletes, Calamospora, 

 Spencerisporites, and Monoletes (text fig. 

 8). In addition, spores definitely assignable 

 to all five sections of Triletes are present in 

 Caseyville coals; only those of the section 

 Lagenicula, along with some unassigned to 

 a section, occur in upper Mississippian 

 rocks. Although absence of spores common 

 to the Pennsylvanian should not be relied 

 upon too heavily, as yet none of the medul- 

 losan, sigillarian, triangulate, zonate, auric- 

 ulate, or deltoid-bladdered spores have been 

 observed in Chester rocks. 



Caseyville megaspore assemblages indi- 

 cate a more diverse heterosporous lycopsid 

 flora. Triletes? corycilis seems to be re- 

 stricted to the lowermost Caseyville coal in 

 Illinois (maceration 798) and to the French 

 Lick Coal of Indiana. T. praetextus seems 

 to be restricted to the Battery Rock Coal of 

 Illinois and to the shale above the Pinnick 

 Coal of Indiana. T. globosus var. (B), T. 

 subpilosus, and T. rotatus are restricted to 

 the Caseyville Group. T. glabratus, Cysto- 

 sporites varius, and C. verrucosus appear 

 high in the Caseyville. 



In general, the assemblages of the French 

 Lick Coal and those of the four unnamed 

 coals from the Wabash County cores are 

 similar in character and are distinguishable 

 from those in younger coals of the group. 

 The contrast between the spore assemblages 

 of the Chester and the Caseyville (text fig. 

 7) is very striking in the Eastern Interior 

 Coal Basin. 



TRADEWATER GROUP 



The next higher major stratigraphic di- 

 vision of Pennsylvanian rocks, known as the 



Tradewater Group, encompasses strata from 

 the base of the Grindstaff Sandstone in 

 southern Illinois upward to the base of the 

 Palzo and Isabel Sandstones in southern 

 and western Illinois respectively (Wanless, 

 1956). The Tradewater Group includes 

 sandstones, shales, coals, and, in contrast to 

 the Caseyville Group, several extensive ma- 

 rine limestones. 



Some of the coals, such as the Murphys- 

 boro, Rock Island (No. 1), Davis, and De- 

 Koven Coals, are commercially important 

 (Cady, 1952). The maximum thicknesses 

 of the group are 445 feet in southern Illi- 

 nois, 100 feet in western Illinois, and possi- 

 bly as much as 600 feet (subsurface) in cen- 

 tral Illinois (Weller, 1945). The group is 

 considered generally equivalent to the 

 Krebs and lower Cabaniss Groups of the 

 lower Desmoinesian Series of the Midconti- 

 nent region (Wanless, 1956), the upper 

 Pottsville (Kanawha Series) and lower Alle- 

 gheny of the Appalachian region, and the 

 Westphalian B and C of Europe (Moore et 

 al., 1944; Kremp, 1955). 



In terms of floral zones, as defined by 

 Read (1947), the Tradewater Group con- 

 tains plants from zone 4 (Zone of Canno- 

 phyllites), from zone 5 (Zone of Neurop- 

 teris tenuifolia) and from the lower part of 

 zone 6 (Zone of N. rarinervis). On the basis 

 of small spore studies, Kosanke (1947, 1950) 

 found the flora more diversified than that 

 of the Caseyville Group. He stated that the 

 dominant genus throughout the Trade- 

 water is Laevigatosporites, which is replaced 

 as dominant element by Lycospora in only 

 one coal. The subdominant genera are 

 Granulatisporites, Cirratriradites, Triqui- 

 trites, and Lycospora. Alatisporites, Cirratri- 

 radites, Florinites, and possibly Reinscho- 

 spora appear for the first time in the Penn- 

 sylvanian of Illinois in the Tradewater 

 Group. 



The large spore occurrences in coals of 

 the Tradewater Group are based on a study 

 of more than 60 samples from 16 counties 

 in southern, western, and northern Illinois. 

 Unfortunately, the coarse residues of sev- 

 eral of the samples that served in part as 



