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THE JOURNAL OF GEOLOGY. 



To the northward the degradation extends farther and farther 

 westward, and finally covered the entire width of the Coastal 

 Plain. To the southward its amount diminishes gradually. 



The next epoch was one of general subsidence by which the 

 terrace plains of the last epoch were submerged to a moderate 

 depth, and the earlier Columbia was deposited. The extent of 

 this submergence is represented in the following figure, and some 

 of its relations are shown in the second section in figure 3. 



Figure 3. Sections near the latitude of Washington to illustrate the Post-Tertiary 

 history of the Coastal Plain region. L. Lafayette formation. B. Earlier Columbia 

 deposit. C. Later Columbia deposit. 



In the earliest stage of earlier Columbia submergence, a 

 heterogeneous mass of coarse material was deposited, but with 

 increased depth of water the fine loams and sands were laid 

 down. The coarsest materials were deposited near shore, and in 

 the course of the estuarine channels of the rivers. Further off 

 shore there were finer deposits, and out of the river currents, 

 there was less deposition, and the deposits consist in larger part 

 of local materials. This period is correlated with the first ice 

 invasion of the glacial epoch. 



Following the earlier Columbia deposition the general Post- 

 Tertiary emergence continued to the northwestward, but to the 

 south and east there was either no movement, or slightly increased 

 submergence. The uplift northward was such that the area 

 shown by the heavy rulings in Fig. 4 emerged, finally, to 



