62 



spores. The attack of fungi and bacteria no 

 doubt played an important role in the de- 

 struction of spore exines. Calcite crystal 

 growth has been mentioned by Collins (1959, 

 p. 38) as being possibly detrimental to pres- 

 ervation of spores. 



The diversity of spore taxa in a single 

 sample is partly a function of spore preserva- 

 tion, and this is especially true of many of 

 the shales (probably marine) in which many 

 spores are scarcely recognizable. The great- 

 est diversity of genera and species occurs 

 in shales (macerations 1122-A, 1175-A, E), 

 probably nonmarine, below coals and in one 

 channel sandstone (maceration 1122-Q). 

 Staplin (1960, p. 1-2) found the greatest 

 number of species in the shale below the coal 

 of the Golata Formation (Chesterian in age) 

 of Alberta, Canada. Neves (1958, p. 15) 

 identified the largest number of species from 

 marine beds of the Gastrioceras subcrenatum 

 Zone of the Upper Carboniferous of Eng- 

 land. However, nonmarine shale from the 

 Namurian (Lower Carboniferous) strata 

 studied by Neves (1961, p. 275) yielded the 

 greatest diversity of spore genera and species. 

 The greatest variety of spore taxa in the 

 Lower Oil-shale Group of Scotland (Love, 

 1960, p. 107-109) was recorded from marine 

 shale (i.e., Pumpherston Shell Bed) . 



Spores recovered from the sandstone (mac- 

 eration 1122-Q) represent a peculiar assem- 

 blage from which a large number of species 

 was recorded. Many of them are spiny or 

 highly ornamented forms (Laevigatosporites 

 papillatus, L. spinosus, Secarisporites crena- 

 tus, Punctatisporites product us, P. corona) 

 generally not found in other macerations 

 studied. In addition, Pityos pontes, Stroter- 

 sporites, hueckis pontes, Potonieis pontes, Illi- 

 nites, and miscellaneous saccate forms are 

 present but not abundant. The sandstone is 

 interpreted as a channel fill deposit in which 

 many of the spores were transported by 

 stream currents from a large upland water- 

 shed area. 



SUMMARY 



From the foregoing discussion several gen- 

 eralizations can be made concerning the dis- 

 tribution of small spores through various 

 lithic units in the McLcansboro cyclothems 

 studied. 



1. Forty of the 61 samples macerated con- 

 tained some plant microfossils in various 

 states of preservation, from good to very 

 poor. 



2. No consistent pattern was apparent in 

 the relation between the occurrence and rela- 

 tive abundance of spore taxa and type of 

 lithology. 



3. Many spore genera and species were 

 common to all the cyclothems studied. 



4. Within a cyclothem the same spore 

 genera, with a few exceptions, ranged through 

 a wide variety of lithologies, but considerable 

 variation was found in their relative abun- 

 dance. 



5. Some spore species occurred through 

 several successive lithologies within a cyclo- 

 them, whereas other species were more erratic 

 in distribution. The great bulk of a genus 

 may be made up almost entirely of one spe- 

 cies, but a species is often represented by 

 only one or a few specimens. 



6. In clastic sediments, a strong possibil- 

 ity exists that spores were introduced from 

 reworked older strata. 



7. The selection of samples is an impor- 

 tant consideration in correlation studies be- 

 cause of the wide variation in composition 

 of spore assemblages through short strati- 

 graphic intervals, even within the same lithic 

 unit. 



8. Relative abundances of taxa in small 

 spore assemblages of coals appear to be more 

 useful than those of other lithologies for cor- 

 relation of strata in the Illinois Basin. This 

 is probably because, although an interval of 

 clastic sediment may appear quite uniform 

 over a wide area, the interval may represent 

 several different sources of sediment, each 

 with a different spore population. By com- 

 parison, the swamps where coal was formed 

 had relatively uniform environments. 



If the type of lithology and the factors re- 

 lated to environment of deposition and spore 

 dispersal are carefully considered, however, 

 palynology of strata other than coal should 

 be useful in correlating Pennsylvanian strata 

 of the Illinois Basin in areas where spore as- 

 semblages from two adjacent coals are not 

 particularly distinctive, or where coals pinch 

 out, are poorly developed, or are essentially 

 barren of spores. 



