520 LTE YG OOLIN ATT OT A GLROL OG Ve 
factory conclusions concerning the exact geological age of the 
different parts of the general section can be drawn. 
The igneous masses beneath the sedimentaries are known to be 
Archean in age. They were subjected to prolonged degradational 
action; and it was upon their profoundly eroded surface that the 
sand and limestones were laid down during early Paleozoic 
times, burying to very considerable depths probably all of the old 
peaks and elevations. While it is true that the relations of the 
different sections of the region has not yet been determined with 
accuracy it appears evident from the data at hand that the 
Silurian is well represented and that a part belongs to the Cam- 
brian. 
In southeastern Missouri the Paleozoic rocks from the top 
of the column down to the base of the Trenton are well 
known. Beneath the latter there is, as first made out by 
Shumard, a bluish, limerock having a thickness of upwards of 
100 feet, which has been regarded as the non-fossiliferous por- 
tion of the formation just mentioned. Below all this there comes 
the sequence of dolomites and sandstones to which reference has 
been made. It has further been stated that there were formerly 
considered to be four great limestones alternating with arenaceous 
beds; but of late it has come to be believed that the relations of 
these beds are not exactly in accordance with the views expressed 
at first. East of the crystalline area and trending in a broad 
curve northwest and southeast, a direction which is nearly at 
right angles to the axis of the uplift, are the oldest Paleozoic 
rocks whose geological age is definitely known. Immediately 
west of this belt of strata, which is the fossiliferous Trenton lime- 
stone and the band of similar rock but almost without fossils, is 
a narrow zone of what has been termed the First Magnesian 
limestone, and then in a somewhat broader belt the First or Sac- 
charoidal sandstone. A short time ago’ it was suggested that 
the latter probably rested unconformably upon the strata beneath ; 
andmore recently Winslow? has reported from the vicinity of 
tKEYES: Missouri Geol. Sur., Vol. IV, p. 35. Jefferson City, 1894. 
? Missouri Geol. Sur., Vol. VI, p. 356. Jefferson City, 1895. 
’ 
