576 



THE JOURNAL OF GEOLOGY. 



Columbia deposits, which represents the products of the sub- 

 serial erosion of the inter Columbia uplift in the region westward. 

 In his report on the " Geology of the Head of Chesapeake Bay," x 

 McGee describes several exposures of this feature and represents 

 it in his general section, but gives no suggestion as to its inter- 

 pretation. It has been found to be general over a wide area, 

 but is not everywhere equally distinct. The relations are shown 

 in the following figure : 



mm iiiii 



BOO O 



'»' V»°. o°o '.*" : '.' a •» «? 0> 



• c Ts , oid..f , »<' 



ISilSlflll! 



Figure 2. General section of Pleistocene deposits on the eastern side of Chesa- 

 peake Bay showing relations of cross-bedded sands between the earlier and later 

 Columbia deposits. I. Loam. 2. Gravel and bowlder bed. 3. Cross-bedded coarse 

 sands. 4. Loam, with scattered pebbles, etc. 5. Gravel and bowlder bed. 6. Pre- 

 Pleistocene formation. 



The basal beds of each of the Pleistocene formations contain 

 very coarse material to the westward which comprise bowlders, 

 pebbles and sub-angular masses of quartzite, quartz, crystalline 

 rocks, sandstones, and cherts, more or less closely packed in 

 sands and loams. Some of the masses stand on end, and these 



T U. S. G. S., 7th Ann. Rept., li 



Pp. 537-646. Plates. 



