318 I. Bowman — Atlantic Preglacial Deposits. 



the sands strongly cross-bedded. There followed a period of 

 erosion which may represent very shallow water conditions 

 without actual exposure to subaerial processes. Currents and 

 waves have already found expression in the cross-bedded struc- 

 ture and to their increased efficiency at this time may be 

 attributed the unconformity in question. Then came the 

 deposition of the black sands composed of grains of smoky 

 quartz, followed by the deposition of the red sands. The 

 slight thickness of the beds representing the intervals of 

 deposition, together with their cross-bedded structure and 

 present position and attitude with respect to other beds, and 

 the existing shoreline favors the view that coastal changes 

 were here of a less profound order than along the more south- 

 erly part of the Atlantic littoral, where extensive denudation 

 followed the deposition of beds of great thickness. 



Apparently the greatest erosion followed the deposition of 

 the red sands. In many places the red, black, and white and 

 yellow sands are entirely removed down to the basal yellow 

 clays. In the depressions thus formed was deposited the 

 greenish black clay of figures 1 and 2. Gradual shallowing 

 of the deeper water in which the clays were deposited is 

 represented by the greenish-black glauconitic sands at the top 

 of the darker beds, figure 1. 



The succeeding events of importance in the history of this 

 part of the New England shoreline were the erosion of the 

 whole series thus related and successive advances of the ice. 

 The first effect of the latter process was probably the deposi- 

 tion of the brown erratic sands as a preliminary wash to be 

 superseded by the deposition of the ice-borne clay and bowld- 

 ers. The relations of the glacial material were not considered 

 in detail, as the field of observation was too limited. The 

 explanation v of the manner of deposition of the stratified 

 glacial sands may therefore be erroneous when more extensive 

 observations are made. The retreat of the ice left the surface 

 of the till practically as we see it today, except where it is 

 modified by shallow gullying or by the insistent attack of the 

 sea. 



The weight and movement of the ice upon the unindurated 

 preglacial sands and clays below resulted in the bodily removal 

 of great masses of these deposits. They are clearly seen in 

 the face of the cliff surrounded by erratic sands and bowldery 

 clay (A, fig. 1). In addition, the remaining sands exhibit ice 

 disturbance, for while they are practically in situ they are 

 minutely fractured and faulted as shown in the upper right 

 hand corner of fig. 2. In every case the blocks are easily 

 restored in thought to their original positions by the help of 

 slight variations in color and texture. The openings between 



