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tributary. It shows the filled-in material to be eighty-eight feet deep; 
that makes the old tributary somewhat below the present level of Raccoon 
Creek, where the present tributary enters. But not more than thirty rods 
to the northeast of the well, limestone outcrops. This indicates that the 
long hill protruding westward from section 24 was continued as the north- 
ern divide of the old tributary. 
THE PRE-GLACIAL GEOLOGY OF FLATWOODS. 
In considering the geology of the Flatwoods region, it is thought best 
to divide it into two main divisions. The first division includes the rock 
structure of the region and the subsequent history up to the Pleistocene. 
The second division begins with the Pleistocene and takes in all up to the 
present. The rock structure of the region and immediate vicinity is of 
Middle Mississippian age with some Pennsylvanian bordering closely on the 
west. The stratigraphy of the region will be given a brief treatment. 
Knobstone Group. Just to the east of the region in the valley of 
Jacks Defeat Creek, are the upper portions of the thick Knobstone Group 
of shales and sandstones. The area of its outcrop in Indiana is a strip of 
territory some twenty-five miles wide, extending north, northwest from 
Floyd County to Benton Countyy. This formation consists of compact, insol- 
uble, impervious sandstones and shales, aggregating a thickness from 400 
to 600 feet. The topography of the outcrop, resulting from the peculiar 
weathering of the rocks, is of a distinct type. The rocks absorb water 
readily, but transmit it poorly, so that they are easily shattered by freezing 
and thawing. The region is weathered and eroded into deep, steep-sided 
valleys of very pronounced relief. Brown County affords a typical example 
of Knobstone topography. Another characteristic of this group of rocks is 
the general absence of fossils, such being present only very locally. It 
seems that the shales and sandstones were laid down in impure, muddy 
waters, which were not on the whole very favorable for the life of water- 
breathing animals. 
Harrodsburg Limestones. Overlying the Knobstone is the Harrodsburg 
limestone, with a thickness varying from sixty to 100 feet. This limestone 
consists of several heavy bedded layers of hard, gray to blue, often highly 
erystalline stone. ‘There are occasional intercalated thin beds of shale. 
In some sections a very cherty layer occurs. The top member of this 
stone often is very massive, and its texture is very similar to the oolitic 
bed overlying. Geodes are characteristic. The limestone as a whole is 
