628 J. V. LEWIS ORIGIN OF PILLOW LAVAS 



surface of the flow, as shown by the unoxidized condition and the dense 

 enamel-like character of the undulating pillowy surface. The flow oc- 

 curred in a broad intermont valley, or bolson, of continental deposition 

 and was soon buried in the accumulating sediments.^^ 



At Great N'otch the situation of the quarries near the middle of the 

 trap outcrop shows that they are also about the middle of the sheet, and 

 the same condition holds northward to Paterson. The quarries at the 

 latter place may be somewhat below the middle of the sheet, but they are 

 still well above its base, as shown by figure 1, which has been constructed 

 to true scale from the most accurate data obtainable. I do not believe it 

 possible to consider the scoriaceous muddy lava encountered at one point 

 in the floor of the quarry at West Paterson as the base of the sheet, al- 

 though Fenner^^^ has so interpreted it. In attributing the origin of the 

 pillows to the influence of this mud and possibly an accompanying body 

 of water, Fenner further overlooked the very important fact that there is 



Figure 2. — Diagrammatic Cross-section at Glenside Park, Neic Jersey 



Showing relations between the massive basalt, pillow basalt, and the overlying 

 shale in a ravine one-fourth of a mile east of the bridge at Glenside Park (Feltville). 

 New Jersey. Modified after Darton. bulletin of the U. S. Geological Survey, number 67. 



a thickness of 20 to 30 feet of massive lava between the muddy scoria and 

 the pillows. In this there is no trace of mud, nor in the overlying pillow 

 lava, and it is diSicult to conceive of any possible genetic connection be- 

 tween them. Somewhat similar structural relations seem to exist at Great 

 ]^otch also. The aqueduct tunnel encountered much muddy, cindery 

 lava, as shown by the refuse dumps ; but the quarry, which lies about 100 

 feet above the tunnel, shows characteristic pillowy structure without ad- 

 mixture of mud. It is sig-nificant that here also the old quarry beside the 

 railroad, a few hundred feet west of the present quarry and at a higher 

 horizon, exposed a like scoriaceous muddy phase of the basalt. This lies 

 well above the pillows and, like that below them, must be regarded as 

 entirely independent. 



TTe are thus placed in the dilemma that Emerson faced at Greenfield, 

 Massachusetts, where he ascribed the '^T^reccia" (pillow lava) beds to the 

 influence of the underlying wet sediment: but in many places normal 



^ J. Yolney Lewis : The origin and relations of the Newark rocks. Ann. Rept. Geol. 

 Survey of New .Jersey for 1006. pp. 97-129 ; Charles Schuchert : Bull. Geol. Soc. Am., 

 vol. 20, 1910, pp. 4.38, 578. 579 ; Joseph Barrell : Am. .Jour. Sci.. vol. xxxvi, 1913. p. 438, 



i<» C. N. Fenner : Annals N. Y. Acad. Sci.,- vol. xx, 1910, p. 99. - 



