RECOGNITION OF BEDS OF TERTIARIC AGE IN OUR STATE. 
BY CHARLES KEYES. 
Iowa has been repeatedly and so thoroughly planed off and worked 
over by continental glaciers of no less than five great ice-invasions that 
it could be hardly expected that any remnants of the softer pre-glacial 
formations, if there ever were any deposited within the state’s boun- 
daries, would survive. Moreover, the state is now everywhere so deeply 
covered by the several till-sheets and the vast eolian soil-mantles as to 
effectually conceal all traces of the existence of pre-glacial deposits 
which we ordinarily refer to the Tertiaries. 
In spite of these unfavorable conditions I have never, in the twenty- 
five years during which I have been more or less closely connected with 
geological work in the region, given up hope of some day having dis- 
closed true Tertiaric beds of some kind or other. Further, it has been 
surmised that certain of the numerous sections which had been usually 
referred wholly to the drift were in reality partly of earlier origin. 
Several years ago opportunity was offered to examine rather care- 
fully, with this idea in mind, some of the sections of central South 
Dakota. In tracing the formations eastward certain of the sands, known 
to be Tertiaric in age, were found to extend in broken patches nearly 
to the Iowa line. 
During the past year it was possible to make comparison of the un- 
doubted Tertiaric beds mentioned and sundry isolated bodies of litho- 
logically similar character but which reclined beneath the great till- 
sheet of western Iowa, One cf these great beds in particular deserves 
especial mention. It is rather fully described by Bain in his report on 
the geology of Woodbury county, so that no further account of its 
characters and peculiarities need be here reiterated. So remarkable and 
distinctive in its stratigraphic relations was this bed that thef author 
mentioned designates it the Riverside sands. With the evidence which 
Bain records and with the later data received there appears to be but 
little doubt that this and other similar deposits of the region are 
really remnants of a once 'widely spreading formation which was laid 
down in Tertiaric time. It is not at all unlikely that this deposit repre- 
sents Mid-Tertiaric, or Miocene deposition. 
