~ 
Quaternary Geology.— Gordon. 185 
and Keokuk, a band of water-worn shells of the same species as 
those now living in the river (Uniones) extends along both sides 
of the river at an altitude of fifteen to twenty feet above present 
high water mark.* There are indications that between these 
points the channel of the river in pre-glacial times was west of 
where it is now. 
Rock Series.—The following is an approximately complete sec- 
tion of the rock series as now known here. + 
I. ROCK SECTION AT KEOKUK, IOWA. 
Thick. Depth. 
Sandstone with St/gmaria, exposed....10" 
eee HEStlG SHAG... 4... sce cacowaeee. 6! 
ial ASS oe ar gyda 1-62 8'-4” 
OMEN ee encore ss cis wceaonncte aces oF LO) OF 
BUMMER UNG ho ott 6! Sc De doen ce wtomtedt 1g hh 20’ 
Sandstone with Stigmaria; rests upon 
the uneven surface of the St. Louis lime- 
stone. Lower portions include limestone 
fragments, and occasionally Lithostro- 
Be IMAUTETEULLIOSE: siavcis,.iaisis w4-o'=,,0)2ysle, eojs'enereleiars 10’ to20’ 3 
\ 
So ee 
MEASURES. 
le a -———A.—_ —. re 
LOWER COAL 
=) 
{ 7. Upper. Brecciated limestone. Stratifi- 
cation irregular. Portions abounding in 
| greenish and gray clay. Limestone 
fragments 5 to 12 inches in diameter, 
| and more or less water-worn. Fossils 
J usually in fragmentary condition. JL. 
) (UCU TEENG SS Re TACO AC ee 8’ to 20’ 50 
8. Middle. Light or bluish-gray sandstone. 
| Calcareous above, more or less massive 
POETS AIDING crise wc) sx 0 «som wie nde sits miwian cece 5’ to 10’ 58’ 
9. Lower. Yellowish-gray or brown mag- 
nesian limestone. Archimedes wortheni.12' 70" 
LOUIS. 
ST. 
10. Upper or Geode Formation. Shales more 
| or less calcareous, with occasional lime- 
J stone layers. Filled with geodes...... 50° to 60’ 110 
11. Lower, or Limestone Formation. Layers 
| 
( 
KEOKUK.[ 
variable, with one to six inch clay part- 
ings. Argillaceous below.:........... 60’ to 65' 170’ 
*Worthen refers to this as marking the low water level of the river at 
some previous period of its existence. Geological Report, lowa (1853), 
vol. I, Part 1, p. 186. 
+The exposures here comprise all the beds to the base of the Keokuk, 
including six to ten feet of the underlying transitional chert beds now 
classed with the Burlington. The remainder‘of the section was derived 
from the records of the Hubinger artesian well kept by the writer and 
published in the AMERICAN GEOLOGIST for October, 1889, p. 257, 
{For a fuller description of these beds see American Journal of 
Science, Oct., 1890, p. 295. 
