316 I. Bowman— Atlantic Preglacial Deposits. 



The white sands were found to exhibit in the clearest possi- 

 ble manner the erosion of a considerable body of their material, 

 the entire series above them being swept away in addition. 

 Upon their eroded edges lies unconformably a layer of white 

 and yellow clays and sands which are superseded above by the 

 greenish black clays noted in the section. The overlying dark 

 clays and the yellow sands and clays between them and the 

 underlying white sands, thicken gradually toward the middle 

 of their outcrop (fig. 1), where the sands attain a maximum 

 thickness of 3 feet and the clays 8 feet. These clays exhibit 





WHITE. AND YELLOW SANDS 



5 feet 



Fig. 2. Kepresenting unconformity between dark clays and white and 

 yellow sands at E, fig. 1. Nos. 1 and 3 in diagram represent unconformi- 

 ties ; at 2 the deposits are conformable. 



the same changes as those of the lowest clays in the series — a 

 gradual transition into more sandy members of similar color 

 and 12 feet thickness, which completes the upper part of the 

 preglacial section. 



As soon as this relation between the beds was discovered 

 the entire section was re-examined with a view to interpreting 

 the relations which proved puzzling elsewhere, and in each 

 locality, no matter how disturbed by ice action or disguised by 

 landslides, the greenish-black clays and sands were always 

 found upon excavation to overlie stratigraphically the white 

 sands of cross-bedded structure. 



Glacial Series. — The glacial material which overlies all of 

 the preceding beds may be divided into two classes. The low- 

 est is stratified brown sand bearing a high percentage of 

 erratic material and occupying the eroded depressions in the 

 lower beds ; the second is a confused mass of red and white 

 sands (see A, fig. 1) intermingled with erratic sands and 

 typical bowlder clay, the bowlders attaining a maximum diam- 



