SPORE DISTRIBUTION 



73 



SPORE DISTRIBUTION 

 Introduction 



This discussion of the plus 65-mesh resi- 

 dues of samples from coals and carbona- 

 ceous layers is a supplement to a preceding 

 report on small spores by Kosanke (1950), 

 who studied the small spores from the mi- 

 nus 65-mesh residues. Many of the macer- 

 ated samples were used in both studies. The 

 occurrences of spores noted in the plus 65- 

 mesh residues are given for many of the 

 formations in the Chester Series of the Mis- 

 sissippian System and for many of the coals 

 in the Pennsylvanian System of Illinois. A 

 few Pennsylvanian samples from Indiana 

 and Alabama are included. Those of upper 

 Mississippian age were collected from four 

 states: Illinois, Indiana, Kentucky, and Vir- 

 ginia. In general the samples had been col- 

 lected and macerated long before the im- 

 mediate project was undertaken. This re- 

 port therefore represents a general survey 

 of plus-residue material, with primary em- 

 phasis on "large" spores, or megaspores, al- 

 ready available in the Illinois State Geo- 

 logical Survey collections. 



The spore distribution chart (text fig. 9) 

 records the presence of 33 designated spe- 

 cies assigned to six genera and the presence 

 of spores of two other genera. Eleven spe- 

 cies and varieties have restricted ranges; 

 others have less restricted but important 

 stratigraphic ranges. Only one species is 

 represented throughout most of the section 

 studied. 



In order to present a readable distribu- 

 tion chart, when a coal was collected in two 

 or more samples, the assemblages have been 

 reported as a unit for the whole coal. Forms 

 notably restricted to the bottom or top of 

 a bed are discussed in the text. Because 

 the assemblages of various samples of the 

 same coal may differ considerably from 

 place to place, only the assemblage from a 

 coal (maceration number noted on text 

 fig. 9) at one locality is reported. This 

 sample is either one from a locality nearest 

 the type section of the coal (or from the 

 cyclothem in which the type section occurs) 

 or one judged most representative of the 

 whole bed. The assemblages of these sam- 



ples and of the others studied are discussed 

 in the following pages. 



Portions of the distribution chart have 

 been abstracted and adjusted to illustrate 

 certain features of spore distribution. Text 

 figure 7 illustrates the contrast between as- 

 semblages of upper Mississippian and im- 

 mediately overlying Pennsylvanian rocks. 

 Text figure 8 represents the stratigraphic 

 distribution of seven genera and that of the 

 spores assigned to the sections of Triletes. 

 These figures are a composite interpreta- 

 tion, in contrast with text figure 9, and are 

 necessarily generalized. 



Because the samples were not systemat- 

 ically and uniformly taken for the statistical 

 analysis of megaspore content, the terms, 

 "rare" (R), "present" (P), "common" (C), 

 and "abundant" (A) , are subjective and 

 based on the number of specimens ob- 

 served. In general "rare" denotes less than 

 three specimens noted, whereas "abundant" 

 denotes the presence of a hundred or more 

 specimens. When prepared slides only were 

 available for study and the actual relative 

 abundance was unknown, the term "pres- 

 ent" is used unless the maceration records 

 clearly indicate the relative abundance of 

 the various spore types. The occurrences re- 

 ported in text figure 9 have been handled 

 in the same manner; for example, spores of 

 Cystosporites varius are "abundant" in the 

 Rock Island (No. 1) Coal, but "rare" in 

 the DeKoven Coal. 



Rough percentages of relative abundance 

 of spores of different species are given for 

 some coals in the following discussion. 



Mississippian System 

 chester series 



Previous investigations on upper Missis- 

 sippian megaspores in the United States 

 have been limited in extent, primarily be- 

 cause of lack of commercial coals in rocks 

 of this age. Although cyclic sedimenta- 

 tion is evident in the rocks of the Chester 

 Series of the Illinois Basin, formation of 

 coal was limited to a few thin beds and car- 

 bonaceous streaks. Rocks of the Chester 

 Series underlie most of the southern half of 

 Illinois. The 16 alternating limestone-shale 



