26 Ni:W YORK STATE MUSEUM 



gneiss aloiii^" the contact, and locally the crumpled state of the shale 

 would be sufficient evidence to demonstrate that the gneiss had been 

 overthrust upon the shale, even if the actual contact were not visible 

 at a number of places. 



The general trend of both the thrust plane and of the normal fault 

 or faults wdiich limit the gneiss on the east is east of north. At 

 intervals another series of faults, trending northwesterly, intersect 

 and dislocate the former. These are probably also normal faults 

 along which the offset has usually been to the right as one faces 

 the fault plane. In this they correspond to the great majority of 

 the faults which intersect the magnetic iron ore bodies of northern 

 New Jersey. ' 



The relative age of the faults is plainly indicated. The thrust 

 faults are the oldest, and the cross faults, i. e. northwest-southeast 

 trend, are the youngest. The northeasterly trending normal faults 

 are intermediate in age, although not necessarily much older than 

 the northwest faults. Their absolute age is not so readily deter- 

 mined. In northern New Jersey there is evidence that the early 

 movements in the Appalachian revolution which marked the close 

 of the Paleozoic era were in the form of thrusts and that later the 

 beds were folded, the thrust planes themselves being involved in the 

 folding. By analogy it is assumed that the thrust planes in Orange 

 county were formed at the same time as those farther south, par- 

 ticularly since Siluric and Devonic strata are involved in the move- 

 ments. The normal faults are correlated with the movements, which 

 raised, tilted and faulted the Triassic beds in the region only a few 

 miles to the east and brought about the close of that period of 

 sedimentation. 



Correlation of Devonic strata in the Nezv York and AVtc Jersey 

 areas. In 1901, Kiimmel and Weller^ described, under the term 

 " Newfoundland grit " a thick-bedded, fine-grained conglomerate 

 below and a white to greenish sandstone above, having an estimated 

 thickness of about two hundred fifteen feet. The basal portion, 

 so far as exposed, is composed of wdiite quartz pebbles from one- 

 fourth to one-half an inch in diameter, usually set somewhat loosely 

 in a silicious matrix, so that the rock is of open texture and friable. 

 Locally, however, the interstices are filled with a silicious cement 

 and the rock is decidedly quartzitic. These coarser beds grade up- 

 ward into a hard, greenish, thin-])C(lded sandstone, above which are 



■I Kiimmel and Wcllor. Annual l\eport of the State Geologist of New 

 Jersey, iQOi. 



