198 J. V. LEWIS NEWAKK TRAP ROCKS OF NEW JERSEY 



ever, as shown on the map, plate 1. The departures from the prevail- 

 ing northeast strike and northwest dip are due in varying degree to both 

 folding and faulting. Smaller disturbances are produced locally by 

 igneous intrusions, but by comparison these are insignificant. 



It will be noted that in the southeastern half of the ajea, southeast of the 

 Sourland and Watchung Mountain escarpments, the structure is remarka- 

 bly simple and regular, with prevailing northwest dips of 10 to 15 degrees. 

 From this line there is increasing complexity northwestward to where the 

 Newark strata abut against the crystallines of the Highlands. Near the 

 Delaware river, about Lambertville and Stockton, the structures are ex- 

 tremely involved and many details have not been satisfactorily deciphered. 

 To a less extent this is also true of other portions of the northwest. 



The remarkable 'aniformity of the red shales over most of the area 

 constitutes the chief obstacle to an understanding of the structural rela- 

 tions. Folds and faults in these rocks are scarcely recognizable except 

 where trap sheets are encountered, unless exposed in cuts and the deeper 

 stream channels. In a region of low relief such sections are seldom found. 



Folds. — The recurved, hook-like extremities of the Watchung moun- 

 tains are due to a shallow, boat-shaped synclinal fold, the western side of 

 which has been cut off by a fault along the border of the crystallines. 

 Lying directly across the axis of this syncline and dividing it into three 

 nearly equal parts are two smaller anticlines. The axis of one of these, 

 the New Vernon anticline, lies two miles southwest of Morristown and 

 Madison and passes through Green Village, near New Vernon. It 

 pitches southeastward, like the end of an inverted boat, to the east of 

 Green Village. The other, the Hook Mountain anticline, pitches in the 

 opposite direction, the axis passing through Towaco and about 2 miles 

 northeast of Boonton. The outcrops of the uppermost extrusive trap 

 sheet have been thrown into two strong crescentic curves in opposite 

 directions by these folds, and that about New Vernon is the only part of 

 the western border of any of these sheets that escaped being sheared off 

 by the great boundary fault through Morristown and Boonton that cut 

 away the northwestern side of the larger syncline. 



The spoon-shaped end of a large syncline lies west of Flemington, 

 with its westward pitching axis passing through Frenehtown and the cen- 

 tral part of the Hunterdon plateau. Similar but much smaller structures 

 determine the small crescents of trap rock at Sand brook and New Ger- 

 mantown. There are also numerous small, wave-like undulations of the 

 strata between the Watchung mountains and the Delaware river, as shown 

 by frequent reversals of dip in this region, but the homogeneous character 

 of the red shales has made it impossible to decipher the exact structure. 



