Geological History of the Ozark Uplift — Broadhead. 9 
Third limestone forming the bluffs with Second sandstone, or 
Second Magnesian limestone occupying the higher lands. 
In Wright county, Dr. Shumard, observed rocks of the Chou- 
teau group on the higher knobs — relics of former extensive 
deposits. 
The First sandstone is chiefly found on hills near the margin 
of the Ozark plateau. 
Prof. Worthen speaks of a mountain ridge 500 to 600 feet 
above the level of the river at Cairo, crossing the southern part 
of Illinois from near Bailey's landing to Shawneetown, soon 
disappearing beneath the Coal Measures. In Schoolcraft's 
Travels in the Mississippi Valley, 1821, this range of hills is 
laid down and called Oshawano (Shawnee) mountains. 
The Devonian is tilted up at Bald Bluff and Bake Oven, 
Jackson county. 111., 25^^.* The Trenton limestone is elevated 
70 feet and forms a reef of rocks at Grrand Chain, in the river, 
with a high bluff on the Illinois side, and still higher on the 
Missouri side.* There is also a remarkable dislocation and 
downthrow at Salt Lick, Monroe county,* crossing the Mis- 
sissippi river at Plattin rock and upturning the Saccharoidal 
sandstone to view. 
Another well defined axis crosses the Mississippi river be- 
tween this and the mouth of the Merrimac river, and is well 
displayed near Columbia, St. Clair county. 111., where the Coal 
Measures rest on the upturned Lower Carboniferous. Prof. 
Worthen speaks of a well defined anticlinal at the latter place. 
On the west side of the river the Trenton is thrown up to view. 
The strike of these axes produced passes along a monoclinal 
in the direction of Sulphur Springs, St. Louis county, to 
near Augusta, St. Charles count}^ which may be considered 
part of the eastern boundry of the Ozark uplift. A northward 
extension from Augusta shows an uplift of Trenton limestone 
on Dardenne creek, and of the Devonian near the west line of 
St. Charles county, on Peruque creek, with a lesser elevation on 
Cuivre river, in Lincoln count3^ 
The Cap-au-gres axis crosses the Mississippi river bringing 
up to view the Second Magnesian limestone just above the 
mouth of Sandy creek with the Saccharoidal sandstone above, 
*Woithen. 
