FORMATIONS IN SOUTHEASTERN IOWA. 297 
& 
1. Concealed. 
2. Hard, white’granular limestone in thin flaggy beds; the lower layers 
contain grains of quartz, - - - - - nea 
3. Hard, compact gray limestone, breaks with conchoidal fracture, - 10’ 
4. Brown magnesian limestone in thick, somewhat undulating beds, - 10’ 
320 
Taking the blue shale as a guide, it is evident that the sand- 
stone in Section A has graded into the magnesian limestones in 
Section B. In Section C the compact and granular limestones 
replace the brecciated beds of Section B. The compact lime- 
stone is identical with the fragments composing a large part of 
the brecciated rock and evidently represents an undisturbed 
portion of the original formation. 
Some excellent exposures of the Saint Louis limestones occur 
near the mouth of Rock Creek: 
VI. ROCK CREEK SECTION. 
1. Concealed. 
N 
Hard, gray compact limestone; contains ARhyuchonella ottumwa, 
Spirifer, Keokuk var. littonz, - - - - - 6’ 
3. Brown, friable quartzose sandstone, - - - - 4’ 
4. Brecciated limestone, - - - - - =e OU 
5. Brown, magnesian concretionary limestone in mass've beds; contains 
Lithostrotion canadense, - - - - - - 15’ 
6. Bed of blue sandy shale, blue grit sandstone, and buff-colored mag- 
nesian limestone confusedly mixed together ; fragments of chert 
imbedded in the arenaceous shale, - - - - - 6' 
7. Blue shale interbedded with thin layers of blue fossiliferous limestone, 16’ 
61’ 
The lower bed (No. 7) is referred to the Warsaw shales. 
The sandstone No. 3 develops locally to twenty and twenty-five 
feet, while opposite Keosauqua it contains considerable quantities 
of calcareous matter and, in places, thin ledges and fragments of 
limestone. The compact limestone above increases to about 
fifteen feet in thickness near Keosauqua, where it is quarried to 
some extent. The heavy-bedded concretionary limestones, No. 
5, graduate locally into arenaceous limestones and calcareous 
sandstones. This gradation may be observed in the basal portion 
in tracing the formation along the bluffs below Keosauqua. At 
