IOWA ACADEMY OF SCIENCES. 95 



really stratified, the lines of stratification becoming more dis- 

 tinct as one passes towards the gravel and stringers of the 

 latter becoming more frequent in the bowlder clay. The 

 relationship has been somewhat obscured by the circumstances 

 of a stream pouring down at the contact of the two lobes, 

 but it seems quite clear that the east lobe is composed of 

 stratified material which is intimately connected with the 

 gravels. In the opposite direction the signs of stratification 

 become more and more obscure until the drift can not be told 

 from the ordinary yellow clay of the Kansan. The transition 

 is not, however, so open to observation and there is a possibil- 

 ity that the stratified drift is distinct from the yellow clay of 

 the region, though there is no known evidence proving it so. 



At the extreme east end of the east lobe there is exposure show- 

 ing the beds below the drift. This exposure is in a borrow jDit 

 made in getting material for the railway fill and is represented 

 in the third photograph (Plate vii.) The overlying bed here 

 is the yellow clay of the Kansan. It is the continuation to the 

 east of that shown in the former photos. It is here so far from 

 the gravels that it shows no signs of stratification nor indeed 

 anything to indicate that it is anything more than the ordinary 

 yellow clay of the Kansan. Beneath the bowlder clay will be 

 noted a pebbleless clay resembling the loess. Indeed one 

 might imagine it to be the ordinary drift-loess section of the 

 region reversed and minus the ferretto zone. In fact that is 

 exactly what it is, a loess buried beneath yellow bowlder clay. 

 In all important respects it so closely resembles the ordinary 

 upland loess that the two could probably be discriminated only 

 with diflftculty . The loess shows under the stratified bed of the 

 east lobe, though it carries here some very fine gravel and is 

 more of a silt than a loess. 



Grand River Section. — The exposure on the river proper is 

 about one mile away though one exposui-e is in view from the 

 other. Between, ordinary erosion has cut away the connecting 

 beds; but looking across the amphitheater the connection is 

 obvious. This section is the only one in the region showing 

 the lower till and is accordingly of exceptional interest. The 

 full exposure shows the loess, Kansan drift and gravels as 

 seen elsewhere. Beneath them are the following beds: 



