ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 445 



organic constituents were probably derived from small hy- 

 drophilous land plants. The marine plant microfossils that 

 were incorporated in the coal probably came from near the 

 environment of deposition, which was favorable for the 

 growth of marine organisms. Fine lamination of the coal 

 indicates that the plant material, clay, and lime mud were 

 deposited in calm water, but some reworking took place. 

 A reducing environment of deposition is suggested by the 

 presence of a large proportion of syngenetic fine-grained 

 pyrite aggregates and the absence of fusinite and other in- 

 ertinite macerals. The presence of rounded and well sort- 

 ed quartz grains throughout the coal and especially in the 

 adjacent limestone (up to 50 percent) suggests a nearshore 

 environment. 



INTRODUCTION 



Samples of a thin coal and coaly shale of Middle Devonian age (early Give- 

 tian of Europe) were recovered from three diamond drill cores from central Illinois. 

 This is the first published report of a Devonian coal found in Illinois and is the 

 second (Sanders, 1967) published report in the United States that describes in de- 

 tail the palynology of a Devonian coal. The samples were also submitted for pet- 

 rographic and chemical analyses. 



The investigation was undertaken first to describe the spores so that a com- 

 parison might be made between the Illinois assemblage and Middle Devonian assem 

 blages from other parts of the world. An added incentive for describing the Illinois 

 assemblage is that the age of the Illinois stratum is well substantiated by other 

 paleontologic and stratigraphic data, whereas this has not been true for some of 

 the other described Devonian spore floras. In addition, it was hoped that a pal- 

 eoecological interpretation could be made, based on available data. 



Acknowledgments 



We are grateful to Dr. D. C. McGregor, Geological Survey of Canada, who 

 made useful suggestions concerning the descriptive palynology. We also wish to 

 acknowledge two members of the Illinois State Geological Survey, Dr. Donald 

 Dickerson, of the Chemical Group, for the chemical analysis of the coal, and 

 Dr. Harold Gluskoter, of the Coal Section, for the analysis of the mineral-matter 

 residue obtained from the sample by low-temperature ashing. 



STRATIGRAPHY AND PETROGRAPHY 



The carbonaceous stratum was found in two cores drilled in McLean County 

 and one drilled in DeWitt County (text figs. 1 and 2, and table 1). The coal and 

 coaly shale were deposited as part of the Davenport Limestone Member, the upper- 

 most member of the Middle Devonian Wapsipinicon Limestone. In 1895, Norton 

 named the Wapsipinicon Limestone for the strata between the Cedar Valley Lime- 

 stone and the Silurian System along the Wapsipinicon River in east-central Iowa. 

 The names Lower and Upper Davenport were proposed also by Norton (1894) for 



