294 
The American Geologist. 
May, 1896 
to deserve a name, and I therefore suggest that they be known 
as the Lake Pecatonica formation . 
Kansan Buried Loess. 
Returning now to our section, we will pass over, for the 
present, the thin stratum of black clay (No. 6), and will de¬ 
scribe the next three beds of silts, which are essentially one 
formation, differing chiefly in color. The whole deposit is a 
very fine sand or silt, consisting of mostly well rounded grains 
of transparent quartz, flint and chert grains of all colors, var¬ 
ieties and shapes, small granular particles of clay and of 
iron oxide, and minute irregularly shaped particles of car¬ 
bonaceous matter. In structure the deposit is laminated, but 
not in the perfect and regular manner of the glacial clays 
above. At first sight it would be taken as a clay, but on close 
examination it is readily seen that minute lens-shaped masses 
of very fine silt alternate with similar masses of slightly 
coarser silt, varying in size even to quite distinctly visible 
layers of sand. .This exceedingly irregular lamination seems 
to be nothing more than simple ripple-marks. There was a 
constant movement of the exceedingly fine sand on the beach 
and in the neighboring shallow water by small rippling 
waves. 
The section only records 10 feet of this formation, as that 
was the greatest thickness exposed at any one point. But at 
the upper end of the ravine the surface of the silt has an ele¬ 
vation of 15 feet above the present flood-plain deposits of 
Yellow creek, and I have dug five feet below that flood-plain 
level without reaching the base of the silt. There are, in 
addition to -the ripple-marks just described, faint lines of 
stratification, yet sufficiently distinct to enable me to deter¬ 
mine that the strata are nearly or quite horizontal. Conse¬ 
quently I have seen a thickness of 20 feet of these strata, 
without having seen either the top or bottom of the formation. 
Such a deposit as this, especially when we consider its age, 
must be of exceptional interest to glacialists. I will therefore 
endeavor to indicate my conclusions in regard to its origin 
and age; but it must be remembered that, as this is the only 
exposure of this peculiar formation, so far as I have been able 
to discover, the data for drawing conclusions are very limited, 
and future studies may show them to be entirely wrong in 
many particulars. 
