FORMATIONS IN SOUTHEASTERN IOWA. 305, 
directly upon the sandstone. An exposure of this kind occurs on 
Coates Creek about four miles north of Bonaparte. In thickness 
the formation varies from a few feet to twenty or twenty-five feet. 
The area over which this deposit is recognized is innomrecl, Iie 
is not known outside of Van Buren county except at one locality 
in Lee shown in Section III. (p. 294). In Van Buren county the 
sandstone appears to be directly related to the Bentonsport arch, 
evidently lapping up against it in the form of an off-shore deposit 
and thinning out away from the axis of uplift. In origin and 
occurrence it is clearly related to the brecciated limestone and is 
seemingly only a phase of that formation due to local conditions 
attending deposition. The relations of the various beds is shown 
in the accompanying hypothetical section from south to north. 
PEE EL 
3 Fag = O 
Fic. 3.—Section from south to north showing the relations and variations of the _ 
Saint Louis limestone: (1) Geode bed (Keokuk). (2) Warsaw shales and limestones 
(Keokuk). (3) a. Arenaceo-magnesian beds, 4. Brecciated limestone, c. Keosauqua 
sandstone, d. White or gray compact and granular limestones. (4) Lower Coal 
Measures. 
UNCONFORMITIES. 
Onconformity below the Saint Leus.—lt has been shown by 
White’ that while the borders of the Kinderhook, Burlington and 
Keokuk formations recede, showing a gradual withdrawal of the 
sea to the south, the Saint Louis limestone overlaps these and 
reaches nearly as far north as does the Kinderhook. ‘‘Conse- 
quently these beds (Saint Louis) are recognized as resting uncon- 
formably upon all the rest of the Lower Carboniferous in Ilowa.’’? 
Hitherto no evidence of unconformity at this horizon has 
been reported from southeastern Iowa. In the nature of the 
Geology of Iowa, 1870, Vol. I., p. 226. 
2C. R. Keyes has recently found beds with typical Burlington crinoids and other 
fossils in Keokuk, Marshall and Humboldt counties, proving the extension of these beds 
nearly to the Minnesota line. Hence the overlap of the Saint Louis is probably not 
so great as White supposed it to be. 
