IOWA ACADEMY OF SCIENCES. 69 



east of Jesup. In the neighborhood of Rowley there are 

 numerous pits, and well records show the beds to be continuous 

 over an area of two or three miles in extent. An area of prob- 

 ably greater extent is known in the eastern part of Pairbank 

 township. Along the sags followed by the prairie streams 

 they are very common, having been laid down apparently 

 along the courses of pre-Iowan valleys, which were only partly 

 filled by the later lowan drift. The broad swale followed by 

 the south branch of the Maquoketa, in Madison township, and 

 the similar swales in which flow Buffalo creek and Pine creek, 

 in Buffalo and Byron towo ships, are all occupied by Buchanan 

 gravel under a thin layer of lowan drift. 



These gravels are equally well developed in Delaware 

 county. A very ferruginous bed, thirty feet in thickness, occurs 

 just north of Earlville, and covers a large area of rather high 

 ground. An area embracing some hundreds of acres, and 

 occupying a low plain along Bear c^eek, near Dyers ville, is 

 underlain by gravels of the Buchanan stage. The thickness is 

 unknown. The plain is covered with lowan drift to a thickness 

 of two or three feet, and is liberally sprinkled with large 

 lowan bowlders. Near Colesburg, in Delaware county, six or 

 eight miles beyond the extreme eastern margin of the lowan 

 drift, there are several exposures of typical Buchanan gravels 

 overlain by loess. 



Buchanan gravels present two phases, an upland phase and 

 a valley phase. They occur at all elevations, and some of the 

 thickest, heaviest beds are found on the very highest points of 

 land. The gravels of the upland phase are coarser, the pro- 

 portions of sand being less, and the size of the pebbles them- 

 selves being larger, than are those found in the valleys. Bowlders, 

 presumably transported by floating ice, are larger and more 

 numerous in the upland phase than in the other. It is the 

 upland phase that occurs at the typical locality in i he Illinois 

 central gravel pit. A heavy bed of the same type occurs a mile 

 east of Independence, on the highest ridge between the Wapsi- 

 pinicon and Buffalo creek. It is this same type that is found 

 on the high ground north of Earlville, west of Winthrop and 

 east of Jesup. 



The valley phase of the gravels is well illustrated at the beds 

 near Dyersville. These beds have been used extensively for 

 ballast by the Great Western railway. Sand predominates. 

 Cross-bedding is less common than on higher ground. The 



