78 
The American Geologist. 
February, 1896 
ported by currents, but by floating masses of ice. While, 
therefore, the gravels lie between two sheets of drift, and for 
that reason may be called interglacial, probably Aftonian, they 
yet belong to the time of the first ice melting, and are related 
to the Kansan stage of the glacial series as the loess of north¬ 
eastern Iowa is related to the Iowan stage. 
While the Illinois Central gravel pit is the typical exposure 
of the Buchanan gravels, the same beds are found widely dis¬ 
tributed throughout Buchanan, Linn, Jones, Delaware and 
probably other counties. One exposure that has been utilized 
for the improvement of the county roads, occurs on the hill¬ 
top a mile east of Independence. Another, used for like pur¬ 
poses, is found a mile and a half west of Winthrop. The 
county line road, northeast of Troy Mills, cuts through the same 
deposit. Throughout the region already indicated there are 
many beds of similar gravels, but in general they are so situ¬ 
ated as not to show their relations to the two beds of drift. 
The Buchanan gravels, it should be remembered, represent 
the coarse residue from a large body of till. The fine silt was 
carried away by the currents, and deposits of it should be 
found somewhere to the southward. It may possibly be rep¬ 
resented, in part at least, by the fine loess-like silt that forms 
a top dressing to the plains of Kansan drift in southern Iowa 
and regions farther south. 
Explanation of Plates, 
plate IV. 
Fig. 1. General view of the typical exposure of the BuchaDan grav¬ 
els. The black loam has been stripped off and is heaped up in an irreg¬ 
ular pile in the upper part of the view. Beneath the heap of loam is a 
thin band of Iowan drift, and the drift rests upon the water-laid, cross- 
bedded sands and gravels. The small boulders in the foreground have 
been thrown out of the gravel by the workmen. They are of types 
characteristic of the Kansan drift and they now rest on blue clay of 
Kansan age. 
Fig. 2. Near view of the Buchanan gravels. 
plate v. 
Fig. 1. An abandoned part of the gravel pit from which the Bu¬ 
chanan gravels have been removed for ballast. The stratification of the 
gravels is obscured by rain wash.' A boulder belonging to the Iowan 
stage is perched on the margin of the pit, and others, having been un¬ 
dermined, have fallen to the botton of the excavation. 
Fig. 2. Field immediately north of the gravel pit, showing large 
numbers of Iowan boulders. 
