626 



J. V. LEWIS ORIGIN OF PILLOW LAVAS 



pillows of a wide range of form, and some of these show the short necks 

 by which they are joined together. 



Three-eighths of a mile south of the river and just above the West 

 Paterson station of the Delaware, Lackawanna and Western Eailroad, a 

 large quarry in the trap rock shows pillow structure (plate 16) constitut- 

 ing the whole of the west and south walls of the ' quarry, a thickness 

 ranging from 50 to 75 feet, and also a part of the east wall has the same 

 structure. Xorthward along the east wall, however, the solid lava, about 

 20 feet thick, with somewhat irregular jointing, underlies the pillowy 

 rock, and beneath this, in turn, the bottom part of the wall and the adja- 

 cent bed of the quarry consist of extremely vesicular lava in somewhat 

 rounded and irregular masses up to 8 or 10 feet in diameter and inti- 

 mately mingled with a matrix of red mud, which here consists of a mix- 



First TTatchung 

 Mouataia 



-Geologic Cross-section of First Watchung Mountain 



Showing the position of quarries and railroad cut with pillow lava. Paterson, New 

 Jersey. Horizontal and vertical scale the same 



ture of clay and very fine quartz sand. The masses in this portion are 

 least vesicular at the center and extremely scoriaceous and spongy at the 

 surface, where they are mingled with and stained by tlie red mud. North- 

 ward this vesicular mass drops below the bed of the quarry and solid lava 

 constitutes the whole of the depth at the northeast corner, with the lower- 

 most 10 or 15 feet jointed in regular columns. About 500 feet westward 

 an older and somewhat smaller quarry beside the railroad shows the pil- 

 low structure in its southern and eastern walls. Interbedded massive 

 basalt overlies this in the western wall, but pillow structure again occurs, 

 at a higher horizon, in the railroad cut immediately northwest of the 

 quarry. 



Most of the pillows are circular or elliptical in cross-section and range 

 from 1 to 2 feet in diameter, although both smaller and larger individuals 

 are found. They vary in shape from spheroidal to ellipsoidal and some- 

 what more elongated bolster-like and irregular forms, but in general the 

 structure is prevailingly ellipsoidal and remarkably regular. The indi-. 

 vidual masses show little or no distortion at the points of contact with one 



