236 Transactions of the Academy of Science of St. Louis 
But it is reasonable to assume that a considerable portion of 
the sediment found on the flood plain of the Mississippi River 
today was deposited in Wisconsin time. 
The tributaries to the Middle Mississippi, however, were 
not as efficient eroding agents as the master stream; and frag- 
ments of the deposits made during Wisconsin time, in other 
words, fragments of the Festus Terrace, may be traced along the 
banks of these tributaries, usually for several miles from their 
mouths, 
In a few instances the tributary stream was unable to cut 
through the deposit which choked its mouth. Sandy Creek in 
Jefferson County, Missouri, formed a water-gap into Joachim 
Creek to the south, abandoning its former oxtlet at Riverside 
(Fig. 6). As a matter of fact, the drainage has been diverted 
from nearly two miles of its lower course. 
At the mouth of Hubbel Creek, in Cape Girardeau County, 
the Mississippi was silted up to the level of the tops of the 
confining bluffs. Under this condition, the mouth of Hubbel 
Creek was deflected downstream, as is quite common in the case 
of tributaries. Hubbel Creek was a superimposed stream. When 
the master stream began to remove its accumulated sediment, 
Hubbel Creek remained in its new channel and eroded, the sand- 
stone underlying the new course, instead of the unconsolidated 
sediments of its old course. This has produced a youthful can- 
yon at the mouth of the river, quite out of harmony with the 
mature course farther upstream, 
There is an abrupt change in the elevation of the Festus 
Terrace in the vicinity of Wittenberg, Perry County, Missouri. 
The fragment of the terrace south of this point are consistently 
about 40 feet lower than are the fragments to the north of this 
point. This raises the question as to whether there may not 
have been diastrophic movement in late or posi- Wisconsin time 
to acount of this discrepancy in summit levels. A fault. which 
