Correspondence. 257 
iween. The Thayer exposure shows the gravels and the overlying drift 
with certain sands and fine clays between. 
Afton Junction. The pits at this place are about 1,500 feet north 
of the railway station on the west side of the Chicago Great Western. 
They have been opened along the sides of a small stream running 
east and emptying into Grand river. The north side of the pit is 
bilobate, the minor lobe being to the east and not directly in line with 
the main face of the pit. The two lobes in fact form an arc of a rude 
circle rather than a straight face. Between the two lobes is a small 
stream which has cut down to, but not through, the gravels. The 
main face is about 1,000 feet long and has a maximum hight of probably 
seventy feet. The minor or east lobe is about 400 feet long and 60 feet 
high. The bottom of the pit, said to rest on "quick sand," is cut down 
to about the level of Grand river bottom (1,030 A. T.). The stream is 
here of the post-Kansan age. The section exposed at the main face is as 
follows : 
Feet- 
Loess of the usual uplift or older type characteristic of the 
region 10 
Yellow boulder cla.v with upper portion much oxidized 
leHched and highly cok)red, lower portion running in- 
to a blue with weatliered joint cracks. Containing 
much weathered material and planed and stri- 
ated bowlders, Characteristic Kansan 30 
Gravel, corase, cross-bedded, iron stained, cemented in part 
into hard conglomerate ; made up to considerable ex- 
tent of very badly weathered material. Manifestly an 
old gravel 40 
Down to the gravels this is the normal section for the region and 
could be duplicated at hundreds of points. The ferretto zone is well 
developed and its coloring is dark enough to show excellently in a pho- 
tograph. The drift and loess are identical in every particular with that 
found throughout southern Iowa and there can be no doubt whatever 
that the drift is Kaiisan. 
The drift shown in the cast lobe is of the same character as that 
overlying the gravels in the main face, and the identity of the two has 
not been questioned so far as is known to the writer by any who have 
visited the place. Among the latter may be mentioned Profs. T. C. 
Chamberlin, Albrecht Penck, Sanmel Calvin and S. W. Beyer. Prof. 
G. F. Wright and others have seen the exposure, but their opinions on 
this point are not known to the writer. The drift in the east lobe lies 
at a considerably lower level than in tlie main face, extending in fact 
down to the bottom of the pit. As the railway near the station just 
cuts into the top of the gravel a few feet, this was, when first seen, in- 
terpreted to mean that the gravels formed a kame-like ridge with a north- 
west-southeast trend and that the drift had been laid over this ridge run- 
ning down over its side. It was thought likely that there had been 
some erosion whereby an eastern extension of the gravels had been 
cut away before the drift of the east lobe was laid down, and that, ac- 
cordingly, the position of the drift indicated, or at least accorded with. 
