298 
The American Geologist\ 
May, 1896 
scattered over its bottom. The absence of glacial pebbles 
shows that the chert came from the neighboring unglaciated 
shores, and not from the ice-sheet which on the east obstructed 
the valley. 
The silt formation under discussion, although only seen in 
situ in this one ravine, was, I believe, widely distributed over 
the valleys of northwestern Illinois and contiguous areas. 
Well sections, beyond the Pecatonica basin, are occasionally 
reported as penetrating a blue laminated “clay” at the base 
of the drift series. Mr. Frank Leverett, on examining this 
exposure, stated that he had encountered a precisely similar 
“buried loess” in Rock Island county. I have secured sections 
of wells, in Stephenson county, that penetrate a thick deposit 
of blue silty “clay” which lies under the regular drift series, 
being apparently the lowest superficial deposit (preglacial 
soil excepted) yet found in this county. I have been present 
at the drilling of wells in the Pecatonica valley, when the 
sand-pump brought up a deep blue silty clay, with many 
broken bits of white chert, but no drift pebbles. Indeed, I 
am inclined to believe that all the larger valleys are lined to a 
great extent with this deposit, which probably reaches nearly 
or quite to the bottom of the early Quaternary troughs. It 
also probably was originally spread out over the lower upland 
country, and, although never reaching as high a level, was 
perhaps equal in amount to the Valley Loess of the Iowan 
epoch. In the Pecatonica basin it was evidently deposited in 
an ice-dammed lake; and perhaps some of the other basins, 
in which it seems to occur, may have had similar lakes. At 
any rate, it is truly a “buried loess.” 
The blue, ripple-marked, stratified sandy silt, containing 
fossils, at the base of the section in the ravine south of Free¬ 
port, with its correlative deposits in different parts of north¬ 
western Illinois, is of sufficient importance to be placed on the 
list of American Pleistocene formations, and I suggest that 
it be named the Kansan Buried Loess. 
Kansan Glacial Recession and Re-Advance. 
In our Freeport section, we find that the upper part, to a 
thickness of 4 or 5 feet, of the blue silt has been changed by 
some process to a light brown color. This brown silt passes 
into the blue, through the transition stratum No. 8, by inter- 
