Geology and Mineralogy. 



351 



the Perth Amboy district in New Jersey. In these exposures, 

 the structures were so admirably shown that the writer has 

 thouajht it worth while to make a note of the occurrence. 



When iirst met with in the field, these dislocations in the clays 

 were thought to be due to glacial pressure ; and we have been 

 strengthened in this opinion by the receipt of certain letters from 

 Dr. H. B. Kiimmel, State Geologist of New Jersey, who says in 

 part : "I have yours of July 3d and also the photograph which 

 you so kindly sent me. It certainly shows a very good example 

 of a local fold in the upper part of the clay, caused by the ice 



Fig. 1. 







■«*:. 



m 



in 





^ 



_r| 



t 





m. 











f 



* • -W^^*^ 



Hfe 





! " - v,^ 



He 



■'% 



i^~ 



^^^^M l\ 





Fig. 1. Folding in Cretaceous clays resulting from glacial pressure. 



movement." "The faults in the clay bed at Maurer are, in my 

 opinion, probably due to disturbances during the glacial period, 

 as I have observed similar faults in a number of pits in Middle- 

 sex County where the glacial drift overlies the Cretaceous, 

 whereas in non-glacial portions of the state faults in the Creta- 

 ceous are very rare." 



Both of these exjjosures were made in the process of mining 

 brick and fire clays by ihe usual open cut method. The faulting 

 (fig. 2), which occurred at Maurer, Middlesex Co., took place in 

 dark and light gray, plastic brick clays, in the upper part of the 

 so-called Woodbridge clay horizon. The folding (fig. 1), seen 

 two miles farther west, near Woodbridge, in the same county, 



