59 



Pennsylvanian cyclothems studied were found 

 to vary vertically through strata formed un- 

 der changing environments of deposition. 

 Spore assemblages recovered from rocks do 

 not, however, give a complete or necessarily 

 true picture of the flora growing in a given 

 area at the time of deposition. This is due 

 to several factors, which are summarized be- 

 low. 



1. Plants that produced prolific numbers 

 of spores are represented out of proportion 

 to those that bore relatively few spores. 



2. Spores and pollen that possessed struc- 

 tures such as bladders, flanges, processes, 

 spines, and reticulations to aid in dispersal 

 are scattered over a wider area than those 

 not so equipped. 



3. Spores produced by tall arborescent 

 plants presumably are disseminated by wind 

 over a greater area than those produced by 

 low herbaceous plants. 



4. Areas of deposition receive spores from 

 a great distance if prevailing wind and water 

 currents from the source area are favorable. 



5. Spores introduced from reworking of 

 older strata may be incorporated in clastic 

 sediments along with spores produced by in- 

 digenous plants. 



6. Spores with resistant exines are more 

 likely to be preserved during and subsequent 

 to deposition than those with weak exines. 



7. Sampling techniques vary in reliability. 

 A column sample provides a better represen- 

 tation of the floral assemblage living at the 

 time of deposition than do small samples 

 taken at wide intervals. 



8. Errors in maceration technique and 

 identification of taxa, of course, lead to er- 

 roneous conclusions. 



When changes in variety and relative 

 abundance of plant microfossils throughout a 

 cyclothem or a relatively short sequence of 

 lithologies are being considered, evolution 

 probably is less important than environmen- 

 tal changes and factors related to spore dis- 

 persal. 



RELATION OF SPORE 

 DISTRIBUTION TO LITHOLOGY 



Palynology of the McLeansboro Group in- 

 dicates that Punctatisporites is the most 

 abundant genus in all but a few of the sam- 



ples macerated. P. minutus is the most abun- 

 dant species. The relative abundance of 

 Punctatisporites fluctuates throughout the 

 sections in such a way that no relation be- 

 tween abundance and either lithology or 

 position within a cyclothem is evident. In 

 the Fithian Cyclothem, Punctatisporites de- 

 creases upward from the coal into the over- 

 lying shale. In contrast, a siltstone (macera- 

 tion 1175-K) overlying the No. 8 Goal, a 

 shale (maceration 1122-F) overlying the 

 lower coal in the Henshaw Formation, and a 

 sandstone (maceration 1122-Q) directly over- 

 lying the middle coal in the Henshaw For- 

 mation display more Punctatisporites than 

 do their underlying coals. Other workers 

 have found a greater abundance of the genus 

 in shale than in coal. Hoffmeister, Staplin, 

 and Malloy (1955a, p. 355) found that Punc- 

 tatisporites is more abundant in the shale of 

 the Hardinsburg Formation than in the coal. 

 Neves (1958, p. 13-14) also found the great- 

 est abundance of Punctatisporites in marine 

 shales of the Upper Carboniferous of Eng- 

 land. Punctatisporites reaches its maximum 

 development in the shale immediately over- 

 lying the Harlem Coal of West Virginia (Col- 

 lins, 1959, figs. 11-14). 



C alamos por a is an important component 

 in all the cyclothems studied. In the Fithian 

 Cyclothem, the Trivoli Cyclothem in Frank- 

 lin County, and the middle coal of the Hen- 

 shaw Formation, Calarnospora is most abun- 

 dant in the underclays. In the Trivoli Cyclo- 

 them in Macoupin County, the greatest con- 

 centration of Calarnospora was found in a 

 silty shale (maceration 1128-1) above the No. 

 8 Coal. Collins (1959, fig. 14) found Cala- 

 rnospora most abundant in the Harlem Coal 

 and in minor amounts in the underclay. 



Granulatisporites was found in all the sam- 

 ples except maceration 1170-D, the shale 

 directly above the coal in the Fithian Cyclo- 

 them. The greatest relative percentage of 

 Granulatisporites occurs either in strata above 

 coal (Trivoli Cyclothem, maceration 1128-1; 

 section of the Henshaw Formation, macera- 

 tion 1122-G; Fithian Cyclothem, maceration 

 1170-G) or strata below coal (Trivoli Cyclo- 

 them, macerations 1175-C through E, G) 

 but not in coal. Collins (1959, figs. 11-14) 

 found the maximum abundance of Granu- 

 latisporites in the Ames Shale above the Har- 

 lem Coal. 



