134: N IT. Darton — Trap of New Jersey. 



dike, but the peculiar color of the soil, and the irregular out- 

 line suggesting at once eruptive rock, and the general distribu- 

 tion of surface fragments, have led to the adoption of the 

 different view. It seems probable that they have been occa- 

 sioned by the same eruptive action which caused the syenite 

 dike to the west, notwithstanding their great basicity and 

 totally different character. The syenite dike itself varies much 

 in character throughout its extent and still merits further study 

 on its north and south extremities. Connecting these phe- 

 nomena with the dikes at the southeast and south it seems as if 

 there has been a longitudinal manifestation of eruptive activity 

 in an irregular north and south line and that it occurred after 

 the close of the lower Silurian Period. 



These rocks are to be classed with the porphyrites according 

 to the types systematized by Kosenbusch* and would perhaps 

 be made most clear in their relations under the name biotite- 

 augite-porphyrite. They appear to be in many respects very 

 similar to those summarized by Rosenbusch (op. cit., p. 471) 

 and described by Beyschlag, Schmid and others from various 

 parts of Thuringia. With these they seem to agree quite 

 closely in mineral composition, structure and alteration pro- 

 ducts. 



Geological Laboratory, Coruell University. 



Aet. XYIII. — On the great lava floios and intrusive trap 

 sheets of the Newarh\ system in New Jersey / by Nelson 

 H. Daeton, IT. S. Geological Survey. 



Several years ago the writer commenced a systematic study 

 of the Newark system in the . New Jersey region, and several 

 seasons were spent in an endeavor to determine the structure, 

 and the relations of the igneous rocks. The results of these 

 studies will be published during the latter part of this year as 

 a bulletin of the U. S. Geological Survey, and it is the purpose 

 of this paper to give only some general statements in regard to 

 the nature of the more prominent trap masses. 



The larger masses of igneous rocks in the Newark system in 

 ]S ew Jersey constitute thick sheets enclosed in gently inclined 

 soft sediments and their outcropping edges rise abruptly from 

 the surrounding plains as long, narrow ridges generally bared 

 of overlying strata on their gentler inner slopes, and presenting 

 escarpments or steep slopes toward the underlying beds. 



* Mikros. Physiog. Mass. Gest., Band II, pp. 446 and ft 



f This name, originally used by Redfield for the red sandstone of New Jersey 

 has recently been revived by Russell (Am. Geologist, vol. iii, p. 178) and applied 

 to the Jura-Trias of the entire Atlantic slope. 



