94 Transactions of the Academy of Sctence of St. Louis 
Figure 1. 
SERPS Ree APR | 2000 ft. sandstone:: 
4000 ft. shale 
Eero at Nata Shes ns ce ee as 2000 ft. sandstone:'. 
4000 ft. shale 
Sheet aitaite Sete tle ths tae cas : “fei eeel 2000 ft. sandstone:'. 
4000 ft. shale 
Meee et en en se Ses et ot eee ek Power CUUU Lb, SenastOne = 
4000 ft. shale 
In stage 1 there was deposition of flat-lying sandstones and shales of uniform 
thickness. 
Pa 4 / aon * * * % 
* : y ° 
3. ° 
E E SD, ey ye os Bee,” 
ia pone seu 4 NENG = 
. 9 . eT \ So = 4 
& Meo eet 
In stage 2 these sediments were folded. The mountain structure so pro uced 
would be at least as high as the seh i thickness of age ——- Bah wey In 
this case the thickness was 24,000 t or more han four half milesi 
e = rapid at first, but later as the slopes became m 
would progress slowly. Assuming an average rate of one foot every t 
240,000 years would be required to erode the 24,000 feet of strata panera: 
In stage 4 he chiles and limestones were see on the erosion su 
e the line E-S are separated from the 
time interval whieh was long —— Peis allow the erosion 
For this rval 240,000 years 
hovel. gut unconformities 
face E-S. At this locality the strata abov 
underlying rocks, by a 
of four and a half niles of sedimentary rock. 
would not be considered excessive by geologists. 
are known in os geologic record, 
Figure 1. An unconformity is shown in stage 4 between the flat-lying shales 
and limestones gree Rom line E-S and the tilted strata below the line E-S. It 
tilted. This unconformable relationship was developed 
four pin above indicated. 
