GEOLOGY AND PALEONTOLOGY OF THE SCHOHARIE VALLEY 97 



bed parallel to the floor of the old land and the sand facies will 

 form apparently continuous beds parallel to the pebble beds, both 

 thus constituting lithic beds, which extend diagonally across the 

 horizontal planes that demark the time limit of the formations. 

 This relation is shoAvn in the subjoined diagram [fig. 4b. See also 

 fig. 4a and fig. 5]. It is evident that neither the conglomerate nor 



Fig-. 4b Diagram illustrating progressive overlap 



the sandstone thus produced will be of the same age throughout, 

 the age of these beds becoming more recent in the direction of 

 shore migration. The bearing of this fact on the age of some of 

 the Siluric conglomerates and sandstones of the regions adjoining 

 the Schoharie district, will be discussed in a later chapter. The 

 relationships of the strata to each other and to the old land are 

 shown in the subjoined figure [fig. 5]. 



Fig. 5 Progressive overlapping of formations on old land. c. R. coral reef : source of 

 the limestones 



Bearing in mind the conditions just discussed, it becomes evi- 

 dent that through differential erosion, conditions which are very 

 misleading may be brought about, as indicated in the following 

 diagram [fig. (i] where a similar lithic succession is found on 

 opposite sides of the old land axis, without correspondence in age. 



This also explains why in one section a certain formation, con- 

 stituting at that point the base of the sedimentary series, may be 

 thin, while a short distance away it rapidly thickens without lithic 



