354 



FREDERICK W. SARDESON 



Before this relation is explained it should be noted that the drift- 

 wedge, marked D, represents a clay-shale and till intermixture 

 entrapped under the upturned strata. 



To explain how the block bb came to he under the main block 

 (Sb) in the section, the following details are given. The major joints 

 in the rock strata run generally in north-to-south and east-to-west 

 directions. The glacial movement was oblique to those directions, 

 in this case, from the northwest, and the blocks were therefore driven 

 in a diagonal direction. A side thrust may have been given as the 

 one sheared upon the other. The under part or block, bb, also prob- 

 ably rotated in front of the drift, D, as it shoved forward. As the 

 result of the rotation, the distance traveled by the mass seems greater 

 than it probably was. On the other hand, the distance of the gap, 

 Y to Y z , owing to the direction of glacial movement not being exactly 

 diagonal to the blocks, may be a little shorter than the whole distance 

 traveled. 



The most conspicuous feature in the exposed section — viz., the 

 disjoined under block, bb — is not the matter of first importance. 

 Its position is incidental, as is shown by comparison with another 

 part of the same mass, which still lies on the other side of the boule- 

 vard. In this there is normal drift merely, in place of the block, bb, 

 and the larger body of limestone has moved upward quite the same. 



One feature of special significance is the upturned front of the 

 transported mass of limestone and till. Altogether, the front appears 

 to have the shape of the point of a spoon. Another significant 

 feature is the abrupt disjoining of strata at the rear. The strata 

 were pulled apart. These features appear in other occurrences. 

 In other exposures, beds of clay-shale and included limestones, now 

 in place, are seen to end abruptly against the glacial till, as the stratum 

 Sb does on the left of this section. One such exposure which is to 

 be seen at the time of this writing is in another quarry, half a mile 

 to the southeast of the locality of the section shown in Fig. i, on the 

 west bluff of the river. Here the clay-shale beds, some 10 feet thick,, 

 are cut off nearly vertically by the till, the latter lying on the leeward 

 side in relation to glacial movement. Several other similar occur- 

 rences have been seen in the vicinity. They differed, however, in 

 having the abrupt end of the clay-shales more or less sloping. 



