DISTRIBUTION UNITED STATES 623 



frothed up into the liquid lava, carrying with it blocks of the basal bed. 

 "These blocks graduate outwardly into glass, and so have been rounded 

 in place by remelting." The whole mass of this structure is 30 to 70 feet 

 thick for several miles and is covered everywhere by normal trap. There 

 is also normal trap beneath the "breccia" in many places, so that the 

 latter "must have been formed in the midst of the sheet itself." 



Davis and Whipple^^ had previously described this structure near Meri- 

 den, where the base of the sheet for a thickness of 20 feet or more con- 

 tained "oval and discoidal areas of close-grained trap that we have inter- 

 preted as volcanic bombs/' in a matrix consisting of trap fragments and 

 volcanic glass, considered to be lapilli. The "bombs" were found "re- 

 markable for their nonvesicular character and their compact, uniform 

 texture from center to surface." 



New Jersey. — Bounded masses of lava on the northwestern slope of the 

 First Watchung Mountain trap sheet at Glenside Park (formerly Felt- 

 ville), 2 miles northeast of Scotch Plains (figure 2), were described by 

 EusselP^ in 1878 and compared to the "friction-breccias" of Yon Cotta, 

 as he then considered the trap to be intrusive. The masses were found 

 to have a concentric structure, with a slaggy and scoriaceous exterior, and 

 the spaces were filled with angular fragments of greenish rock bound to- 

 gether with reddish cement like the overlying shale. Davis^^ found the 

 structure to consist of 



"a number of oval masses of trap up to 2 feet or more in diameter, contained 

 in a peculiar red and black matrix. The trap masses vary in their texture 

 and color with the distance from their surface; the outer part is black and 

 dense, then amygdaloidal for a few inches with concentric bands of color, 

 and rather dense near the center." 



Darton^* also described this structure in 1890 and in 1908 and Kiim- 

 meP^ in 1897. 



In 1907 the writer described the structure at Paterson, New Jersey, 

 and vicinity (plates 15 and 16) as 



^1 W. M. Davis and C. L. Whipple : The intrusive and extrusive trap sheets of the 

 Connecticut Valley. Bull. Mus. Comp. Zool. Harvard, vol. xvi (Geol. Ser., vol. ii), 1889, 

 pp. 99-138. 



^2 1. C. Russell : On the intrusive nature of the Triassic trjip sheets of New Jersey. 

 Am. Jour. Sci. (3), vol. xv, 1878, pp. 277-280. 



»3 w. M. Davis : On the relations of the Triassic traps and sandstones of the eastern 

 United States. Bull. Mus. Comp. Zool. Harvard, vol. vii, 1883, p. 274. 



^* N. H. Darton : The relations of the traps of the Newark system in the New Jersey 

 region. Bull. U. S. Geol. Survey, No. 67, 1890, pp. 26-28 ; also Passaic Folio (U. S. 

 Geol. Survey, No. 157; Geol. Survey of N. J., No. 1), 1908, p. 9. 



»5 H. B. Kiimmel : The Newark system or red sandstone belt. Ann. Rept. State Geolo- 

 gist of N. J. for 1897, pp. 82, 83. 



XLV— Bull. Geol. Soc. Am., Vol. 25, 1913 



