GEOLOGY AND PALEONTOLOGY OF THE SCHOHARIE VALLEY 



95 



be a stationary one. 1 In such a case, where the supply of material 

 is constant, the conglomeratic and arenaceous material near the 

 shore will soon fill the water and thus the shore will migrate sea- 

 ward. Conglomerates and sandrocks will therefore gradually 

 creep out over the previously deposited offshore rocks (clays and 

 calcareous rocks), these beds thus becoming overlaid by a shore 

 deposit. This explains the upward changes in the character of 

 successive beds from clay rocks to sandstones or conglomerates, 

 the transition being a more or less gradual one. 



In the second case the sea level may be a falling one. Under 

 such conditions the shore would migrate seaward, but at a more 

 rapid rate than occurs in the case of a stationary sea level. The 

 result would be that previously deposited beds would be subjected 

 to reassortment by the waves, the finer material being carried 

 further out, while the coarse material will follow the shore out- 

 ward over the previously deposited finer material, if that is not 

 all worn away. The general effect will be similar to that of the 

 first case, except that the deposits would decrease in thickness 

 instead of remaining nearly the same. This, as in the preceding 

 case, would result in the change from a finer to a coarser rock, 

 with this difference, that the change would be an abrupt one, and 

 more or less worn pebblelike fragments of the underlying finer 

 rock would be included in the coarse rock. Examples where "mud 

 pebbles i. e. fragments of only partially lithified mud beds, are 

 included in sandstones overlying the shales resulting from those 

 mud beds, are not at all uncommon in the Schoharie region. 



The third case and the one of most significance, is that of a 

 rising sea level, or a subsiding shore. Wherever deposits of 

 great thickness accumulate this state of relative condition must 



1 The effect of a stationary sea level is produced where there is an in- 

 crease in sediment brought in, even though continued subsidence goes on. 

 Likewise the condition of a falling sea level is produced in an area of 

 slow subsidence by a great increase in the detritus supplied. The results 

 will be essentially the same as they would be in a stationary or a falling 

 sea level, with a constant supply of material, except that we have an 

 upward gradation from line to coarse texture, [see A. W. G. Wilson. Can. 

 Rec. Sci. July 1903. v. 0, no. 2.] 



