s 



ILLINOIS STATE GEOLOGICAL SURVEY 



such unusual deposits as the Williamston 

 Spore Coal of Michigan, they are commonly 

 abundant. Because of their small size, less 

 than 15/x to more than 10,000^, vast num- 

 bers can be studied easily in the laboratory 

 when they are isolated from coal by one of 

 the various maceration techniques. 



The complex problem of correlation of 

 Pennsylvanian coals in Illinois has been 

 greatly simplified by Kosanke's (1950) in- 

 vestigations of small spore occurrences. Be- 

 cause all vascular plants produce small 

 spores or their equivalents among plants of 

 more advanced organization, such a study 

 is of great value not only in the correlation 

 of beds but also in the assessment of the 

 total aspect of the flora existing during 

 Pennsylvanian time. The megaspores, gen- 

 erally the larger spores, are produced by 

 only the heterosporous vascular plants and 

 therefore yield information on only a seg- 

 ment of the flora. However, the megaspore 

 content of coal beds in European coal 

 basins has been studied extensively for al- 

 most thirty years and such studies have 

 yielded valuable information on the corre- 

 lation of coal beds and their relative age. 

 Even in an area where the stratigraphic suc- 

 cession is accurately known, the relative 

 quantity and kinds of megaspores in dif- 

 ferent coals have provided an accurate basis 

 for comparing an unknown bed to known 

 beds or correlating known beds across a 

 fault zone (Dijkstra, 1946; 1949, fig. 1). 



Because fewer megaspores are produced 

 and because they are generally much larger 

 and heavier than the small spores, they 

 probably were not dispersed as widely as 

 isospores and microspores. An uneven dis- 

 tribution of plants throughout a coal 

 swamp might be masked by the wide dis- 

 persal of small spores, but the large spores 

 might be used in interpreting the geo- 

 graphic distribution of the heterosporous 

 plants. 



In contrast to the intensive megaspore 

 investigations carried on in Europe, very 

 few such studies (Schopf, 1938; Cross, 1947; 

 Arnold, 1950) have been reported in the 

 United States. This is especially true of 

 megaspores of Mississippian age. 



Purpose and Scope 



The plant megaspore assemblages and 

 some other plant remains in the plus 65- 

 mesh maceration residues, mainly of coals, 

 were investigated to determine their possi- 

 ble significance in the correlation of coal 

 beds and in the delineation of heterospor- 

 ous plant distribution in the coal swamps 

 that existed periodically and sometimes 

 extensively over Illinois and surrounding 

 states during upper Mississippian and Penn- 

 sylvanian time. 



General knowledge of the evolution and 

 ecology of the heterosporous plants and of 

 the occurrence and re-occurrence of their 

 spores in various coal beds allows compari- 

 son of successions with those found in other 

 coal basins in the world. A general com- 

 parison such as this adds to our knowledge 

 of the geographic distribution and evolu- 

 tion of ancient floras, but it does not imply 

 intercontinental correlation of coal beds. 

 Such information has shown the succession 

 in the coal basins of Poland, Czechoslo- 

 vakia, France, Turkey, and in the Ruhr 

 Basin to be generally similar (Dijkstra, 

 1949). 



The coals in Illinois have been inten- 

 sively studied and their content of small 

 spores has been noted in previous reports. 

 The coarse residues of the samples used in 

 those investigations were available for study 

 so that a comparison of the occurrences of 

 some megaspores with the occurrences of 

 their botanically related microspores was 

 possible. Aside from the study by Horst 

 (1955) on the coal beds of the Namurian A 

 and B and Westphalian A in Poland, there 

 is very little published information cover- 

 ing both the large and small spore content 

 of the same samples of coal. 



The investigation of upper Mississippian 

 megaspores and their comparison with 

 those of the lowermost Pennsylvanian were 

 begun to determine whether megaspores 

 could provide a ready differentiation for 

 distinguishing Mississippian strata from 

 the unconformably overlying Pennsylvanian 

 strata, a key that would be especially useful 

 in studies of drill cuttings and cores and 



