CONTEMPORANEOUS DEFORMATION 



789 



of an inch or two. Zones showing this sort of distortion are not at 

 all uncommon in the finer elastics of Squantum Peninsula. 



Inferences as to the origin of the Squantum slates. — The characters 

 of the Squantum slate series suggest the following conditions of 

 origin: (i) Muds and silts were quietly accumulated in a body of 

 water practically unaffected by currents, or, at least, by changing 

 currents. (2) Occasionally a rigid body, submerged deep enough to 

 touch bottom in places, floated by and here and there rubbed over 



Fig. 3. — Contemporaneous deformation seen in uncunsolidated sand at Woodland. 

 The folds are truncated and overlain by horizontal strata as at Squantum. The photo- 

 graph does not show the truncated portion of the folds because the beds are of very 

 nearly the same texture at and near the surface of contemporaneous erosion. In the 

 field, however, the relations are clear. The figure illustrates a section about twenty 

 inches long. 



the soft deposits, crumpling them and scraping off the crests of 

 the folds. (3) After the disturbing agent had passed, quiet depo- 

 sition continued as before. 



In his visits with field classes to Squantum the writer was 

 impressed by this peculiar phenomenon several years ago and he 

 explained it as possibly due to floating blocks of ice. Corroborating 

 this hypothesis is the presence of occasional isolated pebbles and 



