5 88 SAMUEL CALVIN 



From the other counties included in the Iowan area comes 

 evidence of the distinctive character of the Iowan drift similar to 

 the evidence from Buchanan. Probably the banner county in Iowa 

 for inter-Kansan-Iowan gravels is Floyd. Here are scores of 

 exposures, occupying every conceivable position from the flood 

 plains of the streams, like the Little Cedar, the Cedar, and Flood 

 creeks, which carried off the waters from the melting Kansan ice, 

 to the highest points on the broad, monotonously level, uneroded 

 divides; and in every case within the Iowan area where these old, 

 weathered gravels are known to be present; they are overlain by 

 deposits indicating a much later and newer glacial episode. It will 

 be sufficient to note only a few of the numerous cases which have 

 been observed. At the old brickyard west of the fair-ground in 

 Charles City the material used was a five-foot bed of loam and 

 yellow clay carrying Iowan bowlders four to five feet in diameter, 

 and overlying the valley phase of the Buchanan gravels, which, 

 in the neighborhood of Charles City, attain an enormous develop- 

 ment. For some miles above Charles City, on the west side of 

 the Cedar River, the old valley gravels may be seen passing under 

 a thin bed of young, bowlder-bearing loam and clay which covers 

 the gentle slopes and passes up over the flat divides. A boring 

 with a post auger within the bowlder-strewn area went through the 

 thin edge of the Iowan loam into the underlying gravels. The 

 holes dug for some recently set telephone poles along the road and 

 a small stream trench some distance up the slope in the field show 

 the same relation of bowlder-bearing loam to the Buchanan beds. 

 A young glacial deposit overlies super-Kansan gravels; at one 

 point in the trench the gravels rest on the blue Kansan till. 



The same story is told, though in a slightly different way, by 

 the majority of the many "mound springs" of this part of Iowa. 

 Mound springs are peaty, boggy places on the hill slopes, due in 

 most cases to the presence of upland gravels lying on impervious 

 blue Kansan, and all covered by the younger sheet of Iowan. The 

 gravels in such cases are reservoirs holding large quantities of water, 

 and this escapes on the slopes near the plane of contact between 

 the reservoir and the underlying clay at the point where the con- 

 ditions are most favorable, presumably where the Iowan cover is 



