THE DOUBLE CREST OF SECOND WATCHUNG 
MOUNTAIN.* 
J. VOLNEY LEWIS 
Rutgers College, New Brunswick, N. J. 
Twenty miles west of the Palisades of the Hudson River rise the 
prominent ridges of the Watchung Mountains, which extend south- 
westward from a point ten miles north of Paterson, N. J., almost to 
Somerville, a distance of forty miles. The parallel ridges of these 
mountains are the outcropping edges of extrusive trap sheets imbedded 
in a series of red shales and sandstones which constitute the upper 
(Brunswick) member of the Newark system in New Jersey. In general 
these strata have an average northwesterly dip of 12 tors degrees. It 
has long been known, however, that the recurved ends of the Watch- 
ung Mountains swing around the extremities of the boat shaped 
Passaic Basin syncline, which has been cut off on the northwest by a 
fault along the border of the crystalline rocks of the Highlands. 
The hook-shaped southwestern portion of Second Mountain (see 
maps, Figs. 1 and 2) is much broader than elsewhere and for a distance 
of seventeen miles the crest is distinctly double. This condition has 
been explained? as the result of a curved longitudinal fault parallel to 
the present outcrop of the trap sheet. While entirely consistent with 
the facts, so far as at present known, the probability of such a coinci- 
dence is so extremely small that, in the absence of positive proof of 
faulting, this hypothesis must be regarded as exceedingly doubtful, 
It is the object of the present paper to explain the observed con- 
ditions upon an altogether different basis, and in a manner requirmg 
no assumptions that are in any way improbable in the light of our 
present understanding of the geologic history of the region. For this 
purpose brief discussions are here given of (1) the facts requiring 
explanation, (2) the interbedded shale hypothesis, (3) the curved 
longitudinal fault hypothesis, (4) the hypothesis of double flow with 
« Published by permission of the State Geologist of New Jersey. 
2 Darton, Bull. U. S. Geological Survey No. 67, p. 22; Kiimmel, Ann. Report 
Geol. Survey of N. J., 1897, p. 125. 
39 
