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to be found. Evidently where these gravels were deposited no consider- 
able breach existed in the line of hills from the extreme southwestern 
point of the triangular hill-land to Warrick county. The Ohio River 
therefore flowed through Pigeon Plain since the deposition of the gravel. 
The presence of typical river bluff loess on the sides of the valley 
shows that it was a valley at the time of the deposition of the loess. This 
channel was therefore cut between the deposition of the gravel and the 
loess. According to McGee the loess belongs to the Columbia division of 
the Pleistocene.* Briefly there are four reasons for referring the gravel to 
the Tertiary: 
1. Absence of glacial pebbles in the deposit. 
2. Unconformity and old soil between gravel and loess. 
8. Lithological resemblance of bed to known Tertiary beds. 
4, Hrosion record furnished by old river channel. 
If the gravels are Tertiary they must belong to the Lafayette division 
of the Neocene, for they resemble _no other Tertiary formation. 
These facts seem to establish the age of the old river channel. Since 
it seems probable that Lafayette sands and gravels are not found in the 
old channel, it was cut after the Lafayette time. The loess shows that it 
existed as a valley during the Columbia period. It was therefore cut dur: 
ing the Post Lafayette and Pre-Columbia High Level, or in other words, 
in the high level period which preceded the first glacial invasion. 
During the “Pre-Lafayette High Level” the land in this region stood 
just about the same height as now, and thus the Ohio cut or deepened the 
valley it now occupies. This was followed by the Lafayette low-level, 
when the ocean covered the eastern plain and a great bay extended up the 
Mississippi Valley. An arm of this bay extended up the Ohio past Spencer 
county. During this time the sands and gravels were laid down as an 
estuarine deposit. 
After the deposition of this gravel the land rose probably 100 feet 
above its Pre-Lafayette level in Spencer County, and the Ohio cut out 
most of the gravel beds laid down in the Lafayette. It trenched over 70 
feet into the underlying Carboniferous rocks, and at some time during this 
period, for reasons not evident at present, it turned aside and cut out the 
thannel now occupied by Lake Plain and that portion of Pigeon Plain 
south of the terrace. 
*D.S. Geological Survey, 12th Annual Report, p. 384. 
