34 H. B. KUMMEL 



Not uncommonly the most careful search failed to reveal a 

 single gneissic or granitic pebble in the border conglomerates, 

 even although the adjoining rocks were of this character. But 

 east of Boonton a conglomerate composed chiefly of crystalline 

 pebbles extends for two or three miles along the border. 



Relations of these conglomerates to the older rocks. — The rela- 

 tions of these conglomerates to the older rocks along the bor- 

 der are significant. In some cases the calcareous conglomerates 

 adjoin small areas of Paleozoic limestone, from which the mate- 

 rials may have been and probably were derived. In other cases, 

 and this is true of the largest areas, the calcareous conglomerates 

 abut against the gneissic rocks, and for much of the distance it 

 is certain that no limestone occurs between the gneiss and con- 

 glomerate, at least not at the surface horizon. Crystalline peb- 

 bles, however, are comparatively rare in the conglomerate. Sub- 

 stantially the same conditions prevail in the case of the quartzite 

 conglomerate. For the most part it adjoins the gneiss, but 

 gneissic pebbles in it are rare. The known areas of quartzite 

 along the border are small, and in general not near the massive 

 conglomerate beds. Lithologically, moreover, they are unlike 

 the bulk of the quartzite pebbles. 



It is evident that along the greater part of this border the 

 beds of the Newark series were not derived from the older rocks 

 which now immediately adjoin them. Shore currents doubtless 

 transported more or less material somewhat widely, and yet they 

 do not afford us the complete explanation for these facts. The 

 northwestern border is for the most part marked by faults. Here 

 the dissimilarity of constitution is the most marked. Where the 

 border is not faulted and the newer rocks rest undisturbed upon 

 the eroded edges of the older beds, they are composed of frag- 

 ments derived from them plus a small contribution by shore cur- 

 rents. Allowance can be made for the work of the currents, but 

 the widespread dissimilarity of constitution is due chiefly to the 

 faulting which has occurred. The waves of the sea in which the 

 Newark beds were deposited did not on the northwest border 

 in general beat against the rocks which now adjoin this area. 



