160 ANNALS NEW YORK ACADEMY OF SCIENCES 



Brunswick beds. What appear to have been the first eruptions in this 

 vicinity took the form of surface flows, the principal members of which 

 now form the Watchung ranges in Xew Jersey. ( See Annual Eeport of 

 the State Geologist of New Jersey, 1897, Plate III, p. 32.) Even were 

 we to suppose the intrusive diabase of the Palisade-Rocky Hill sill to be 

 earlier than the extrusives, yet, since it cuts through the Lockatong 

 series, it is younger than that series, and could not have furnished ma- 

 terial for it. Moreover, an intrusive sill could not form ash. There 

 seems no good reason to expect the occurrence of deposits of volcanic ash 

 before the time of the Watchung flows, although, of course, volcanic ash 

 is often carried for considerable distances by the wind. The petrographic 

 evidence, however, is strongly opposed to such a constitution. 



It has been suggested that the Lockatong may represent the finest rock 

 flour of re-worked glacial deposits. While there is no direct evidence 

 favoring this latter supposition with regard to Lockatong deposition, still 

 such an origin may be regarded as a possible one. However, no glacial 

 markings have been observ^ed among the coarse pebble beds of the under- 

 lying Stockton formation, nor have the}' ever been reported elsewhere in 

 the local Triassic. For physiographic reasons also, as explained below, 

 this hypothesis seems rather unsuitable to the case in hand. The numer- 

 ous investigators of the Triassic formation, both here and abroad, have 

 repeated^ emphasized the possible derivation of the Triassic sediments 

 from rocks which were undergoing the normal process of weathering in 

 w^arm. humid climates. 



The most typical portion of the Lockatong is the central mass of argil- 

 lites. The central portion of the lens is at its maximum more than 2000 

 feet in thickness, and is prevailingly gray in color, as it is in the large 

 exposures at Byram. Above this central portion, red, sandy beds begin to 

 appear at intervals, intercalated with a series of dense gray beds of typi- 

 cal Lockatong aspect. Farther upward the gray beds become less and less 

 numerous, and in time cease altogether, when the Lockatong passes into 

 the t3^3ical red sandy shales of the Brunswick formation above. These 

 "transition beds,'^ as they are called, are usually several hundred feet in 

 thickness. Below the argillites, the same conditions appear. The upper 

 part of the underlying Stockton series is usually red shale. These red 

 shale beds may be developed to great thickness, as at Raven Rock, N. J., 

 some two miles south of Byram, where they form a cliff high above the 

 river. Above the red shale the dense gray rocks appear, at first only oc- 

 casionally, and in two-foot layers, then gradually crowding out the red 

 beds, until the whole series is dense and gray. The transition beds are 

 marked by large areas of mud-cracks and ripple marks, and are especially 



