The Geologic ilistorii of Missouri. — Winsloir. 87 
eastern border, while along the northern border they occur in 
limited patches, as if filling estuary-like depressions in the 
margin of an old land mass. This, therefore, we also class as 
a long erosion period, during which the Ozark rocks were ex- 
tensively denuded and perhaps even base leveled. During 
this interval the inequalities of the surface were produced 
which caused the oft observed unconformity of contact with 
the later deposited Lower Carboniferous beds. 
The Loirer Carboniferotis Epoch. — At the beginning, and 
possibl}'^ before, the waters crept in over the uplift, seizing* 
hold of the insoluble products of sub-aerial decay of the Silu- 
rian rocks to make shales, sandstones and chert conglomer- 
ates, filling in great erosion depressions with these and dis- 
solving the lime to assist in the formation of the Lower Car- 
boniferous limestones. This movement continued doubtless 
for a long time, though at a very slow rate. From the fact 
that fragments of Lower (Carboniferous chert are found ovei' 
the surface so far into the interior as Howell and Crawford 
counties, the waters must have reached that far. Whether 
they extended beyond this, to the Archean area, is doubtful 
No remains of these rocks are found there. It is probable 
however, that estuary-like arms from the Illinois Carbonif- 
erous reached westward into Missouri. 
It is further probable that the submergence of the central 
portion of the Ozarks did not last long, that onl}'^ a thin 
stratum or somewhat isolated patches of rock were formed 
which were quickly and readily removed later. The mass of 
the rocks were doubtless deposited around the Hanks and ran 
out to a feather edge toward the interior. 
Well before the end of the Lower Carboniferous the uprise 
began and continued, probably, until almost all of southern 
Missouri became a land surface. A long continued period of 
emergence followed this, during which denudation must have 
been ver}'^ vigorous. The surface became deeply trenched and 
covei'ed with residuary materials. This caused the unconform- 
ity of the overlying Coal Measures and supplied abundance 
of material for the fragniental rocks which are at the base of 
that series. 
The Coal Measure Epoch. — Karly, probably at the begin- 
ning of the epoch, a renewed submergence and sequence of 
