FEATURES OF TRAP EXTRUSIONS IN NEW JERSEY 307 



These are by no means isolated occurrences, but are repeated in 

 a similar fashion in innumerable exposures. The obvious explana- 

 tion is that they represent the channels of small streams which cut 

 across the face of the country. The sandstones in which they occur 

 I would refer to an aeolian origin, and believe them to have formed 

 the surface of the ground at the time the streams cut their channels. 

 By this I would not be understood to imply that water played no 

 part in the transportation of the sand grains from their original homes 

 in the crystallines. They may have been picked up and laid down 

 repeatedly, now by wind and again by water, before reaching their 

 final resting place, and it would be impossible to draw a sharp line 

 and say that here the work of water ceased and here the work of the 

 wind began. Their final attitude, however, is to be attributed 

 chiefly to the action of the wind. The fact of the subaerial accu- 

 mulation of the great masses of sandstone should be emphasized, for 

 their freedom from moisture at the time of the trap flow has an 

 important bearing upon certain structural features of the trap. 



At Little Falls, a few miles west of Paterson, a bed of sandstone 

 lying about fifteen feet below the second Watchung sheet, carries 

 abundant plant impressions. The remains of woody stems are found 

 which have been converted into coal, and twigs and leaves have also 

 left their impressions in the stone. From the completeness of the 

 forms preserved the trees were evidently not carried to this point 

 from a distance and I am inclined to believe that this is actually the 

 site upon which they grew. Although not in the area under discussion, 

 this occurrence is interesting as indicating the continuation of conti- 

 nental conditions up to the time that the second flow of trap spread 

 over the region. 



THE CONGLOMERATES 



Everywhere throughout the sandstone strata pebble beds similar 

 to those described are of frequent occurrence. Even the shales may 

 contain locally a large amount of gravel. In addition to these, heavy 

 beds of coarse conglomerate are sometimes seen, though they are not 

 as frequent as the sandstones and shales. They were exposed a 

 number of years ago a little to the southeast of the Great Notch in a 

 trench dug for a water-supply system, and at the present time are 

 especially well seen in the sandstone quarry in the gorge of the Passaic, 



