GLEN DEAN CONODONTS 



L0C.2-C0LES MILL 



1 





Sandstone, brown, fine 6'-7' /.■. 





to 



Shale, gray to dark gray, sandy. 2'6" J-t^. ^29 



z: 

 < 



UJ 

 Q 



LJ 



_J 





Br ^^ 





5 23 









limestone' near middfe. 5'6" y_^^^_ 





f \^\^ 1 h-'"^ 







/I'll, 



9- y 



/ 1 1 1 , 1 



&• 



/l III 



s -^ 



Shale, qrav. poorlv / 



5 ? 



laminatea. -^/'^ \^^\ " 1" 





Limestone, gray, crinoidal, /| o | o |^o 



oolitic, cross- bedded, /-^» | o | o |o 



now covered. 8' /o | c | ^o | o o 



Fig. 3. — Coles Mill, locality 2. Just above mouth of 

 ravine, east of flour mill at south edge of Ches- 

 ter, W. line NWi/4 sec. 30, T. 7 S., R. 6 W., 

 Chester quadrangle, Randolph County, Illinois. 



some areas but apparently conformably in 

 others. Although the Glen Dean is the up- 

 permost formation of the middle Chester, 

 it is nearly in the middle of the series, as 

 eight of the sixteen formations of the stand- 

 ard sequence overlie it. 



The lithologic sequence of twelve of the 

 thirteen sections sampled is shown in text 

 figures 2-13. Samples which contain cono- 

 donts are shown in solid black. The sec- 

 tions selected over-emphasize the amount 

 of limestone in the formation because the 

 dominantly limestone sections tend to be 

 better exposed than those composed largely 

 of shale. Generally in Indiana and Ken- 

 tucky a "lower massive limestone" is rec- 

 ognized and above that a unit of mixed lith- 

 ology in which shales predominate but in 

 which limestones and sandstones are pres- 

 ent. This twofold division does not persist 

 in the Illinois outcrop belt, however, and 

 there are places where shale predominates 

 in the lower part and limestone in the up- 

 per. 



The lower massive limestone, although 

 persistent over much of the outcrop, varies 

 in lithology and may be crinoidal, oolitic, 

 dolomitic, or siliceous. Generally it occurs 

 in beds one to two feet thick and is medium 

 to dark gray, medium- to coarse-grained, ar- 

 gillaceous limestone with crystallinity that 



LOG. 3 -GRASSY KNOB 



Sandstone, reddish-brown, thm 

 bedded. 4' 



& 



Covered 2 3 



Limestone, dork gray, granular 

 crinoidal 4' 



:^s: 



Covered, I0'6" 



Limestone, gray, oolitic 3 



f°l ° I 



Covered 3'6" 



Limestone, dork gray, oolit 



iL-ffii 



Covered. 10' 



Limestone, gray, crinoidal. 3' r 



^^^ 



Covered. 4' 



Limestone, gray, medium- 

 to coarse-grained, 

 crinoidal. 

 Hardinsburg shale 

 approx. 5' below base 

 of section. 15' 



. 1 . 1 . 1 



I I I I 



rrm 



YTTA 



LZL 



1 r 



Fig. 4. — Grassy Knob, locality 3. Stream bed in 

 picnic area NEi/^ SEi^ sec. 27, T. 10 S., R. 3 

 W., Alto Pass quadrangle, Jackson County, 

 Illinois. 



is caused in large part by abundant fos- 

 sil fragments. The upper unit of the for- 

 mation in Indiana and Kentucky is highly 

 variable and contains shales, limestones, 

 and sandstones. Some of the upper beds 

 vary several feet in thickness, and may even 

 thin out, within a single quarry. 



CONODONT FAUNA 



Conodonts in considerable variety are 

 present in all of the thirteen Glen Dean 

 sections sampled (table 1). Twenty-seven 

 species belonging in twelve genera, one 

 new, were identified, and specimens of a 

 thirteenth genus, Hindeodella, are abun- 

 dant. Also present are numerous fragments 

 which apparently represent a new genus 

 but which are not sufficiently well pre- 

 served to warrant detailed description. Of 

 the twenty-seven species, seven are new. 



