IOWA ACADEMY OF SCIENCES. 
6B 
A PRE- KANSAN PEAT BED. 
BY T. H. MACBRIDE. 
In making an excavation through a low ridge just east of 
Oelwein, in Fayette county, the workmen of the Chicago Great 
Western railway have recently brought to light some very 
interesting superficial or quaternary deposits. As to the 
nature, age and significance of these deposits taken as a whole, 
our geologists are no doubt ready to give early and accurate 
account. It is for me in this brief paper to discuss, from the 
standpoint of the botanist, a single member of the series of 
strata thus fortunately brought to light. 
By way of description it is sufficient to say that the railway 
cutting mentioned displays on the face of an almost vertical 
wall a succession of well-defined deposits in which have been 
recognized the two principal drift sheets with which Iowa is 
known to be more or less covered, the Iowan and the Kansan, 
and at least one more, prior to the Kansan and, of course, under- 
lying it. These drift sheets or deposits are separated from one 
another in the Oelwein exposure, as elsewhere, by thin carbon- 
aceous strata, the evidence of the vegetation which at one time 
covered the surface of the older deposit. At Oelwein one of 
these carbonaceous division sheets, and that the lowermost, is 
of remarkable prominence and thickness, and to this particular 
layer your attention is now invited. 
Those who have had experience in such studies, and who 
have attempted to trace the limits of superficial deposits, know 
that contact lines are often exceedingly obscure ; the strata are 
recognized by more or less abrupt change of color, or, at best, 
by simply a darkened trace; but here we have a stratum in 
some places nearly a foot in thickness, so purely organic as to 
form almost a brown coal, an unusually pure quality of peat, 
and so striking in appearance as to have won the attention of 
even the men of pick and shovel. The deposit is actually more 
dense than the clay or drift layers above and below, so that 
weathering brings it out as a distinct ledge to-day on the face 
