.•1 
132 SILURIC FORMATIONS IN MISSOURI 
rocks. The last mentioned place is in the bottom of the great 
geotectonic structure known as the Keokuk trough. From this 
location along the line of the Mississippi river the strata rapidly 
rise until in the vicinity of Winfield, in Lincoln county, Missouri, 
rocks of the very base of the Paleozoic succession came to sky. 
At Louisana, in Pike county, Siluric and Ordovicic beds rise 
above the river-level. 
The uprising of this great crustal block is intimately associated 
with a profound dislocation, generally termed the Cap-au-Gres 
fault, the line of which crosses the Mississippi river a few miles 
above the mouth of the Illinois river. This fault is the longest, 
most profound and most important break in strata in all the 
Mississippi valley. 
Several years ago this great fault-line was traced ^ from the 
point where it shows best near the mouth of the Illinois river 
northwestward through Lincoln and Pike counties. 
That part of the general terranal succession which is especially 
instructive in the present connection comprises numbers 2, 3 and 
4. The lower beds are particularly well displayed in the deep 
valley of Noix creek; the upper beds are exposed only in the 
southern part of Pike county and in Lincoln county. 
Siluric Section in Northeast Missouri 
FEET 
8. Louisana limestone.50 
7. Saver ton shales (green).40 
6. Grassy shales (black) (Carbonic) ..... 60 
Unconformity 
5. Limestone, reddish, heavily bedded (Devonic) . . 10 
U nconformity 
4. Sexton limestone, buff, (Siluric).30 
U nconformity 
3. Bowling Green dolomite, brown, (Siluric) ... 20 
U nconformity 
2. Noix limestone, yellow, locally oolitic (Siluric) . . 10 
Unconformity 
1. Shales, blue (Ordovicic).60 
The title ‘^Noix, when first proposed as a distinct formational 
1 Proc. Iowa Acad. Sci., Vol. V, p. 58, 1898. 
