Tticer Deposits of the Spring Hirer Valley. — Hera hey. 39 
formed soon after the flooding had begun. But as the subsi- 
dence continued a fine silty deposit resembling loess was laid 
down over the gravel, reaching also to a higher level in the 
valley. Still later, when the subsidence of the land had 
reached its culmination, the waters spread out over the broad 
terrace or ••second bottom" as a great lake like stream with 
feeble currents, and deposited over the plain a few feet of 
light brown loam tree from gravel. This now constitutes the 
surface, except where it has since been removed by erosion, 
the underlying gravelly clay being thus laid bare. 
The land then rose to approximately its present altitude 
and erosion has continued at varying rates, but uninterrupted, 
to the present day. The stream has nearly cleared its lower 
trough from the gravel and clay, anil has made some progress 
in excavating the solid rock of the ten-ace and bluffs. As the 
stream is at baselevel it is forming a narrow and low flood- 
plain of black sandy alluvium. 
Lithologically, the brown loam or (day which overlies the 
terrace, resting on both the Lafayette gravel and the more 
modern river gravel in the lower trough, is an exact imitation 
<d' portions of the upper member of the Columbia deposits in 
the Ozarks and the lower Mississippi region, and of the Mis- 
souri loess and its correlative deposit in the Osage valley. 
But it is not true loess, as it contains no glacial /■<><■/,■ flour. 
The amount of subaerial erosion effected on the surface of the 
loam since its deposition and by the stream in the same time 
fixes ii- age at or near the Columbia epoch. Furthermore, the 
epeirogenic movemenl which caused the rise in the stream to 
produce it may be definitely correlated with that which caused 
the deposition of the < 'olumbia formation on the coastal plain, 
in the Mississippi embayment region, and about the borders 
of the lowan ice-sheet. In short, there is much evidence that 
the deposit is id' Columbia age. 
I desire to call attention to the following points in the Qua- 
ternary history of this district : 
1. The supposed Lafayette gravel and clay of the Spring 
River valley date from a time when the land stood at lower al- 
titude than the present. 
2. Next was a marked and to a certain extent permanent 
uplift of the region. 
