574 M. AU ROUSSEAU AND HENRY S. WASHINGTON 



pyroxene, a zoned aegirite-augite, and large crystals of titanite and 

 biotite characterize nearly all the rocks of the series, and that 

 the main nephelite syenite mass of Beemerville, with its transgressive 

 dykes of nephelite porphyry and leucite tinguaite, has a definite 

 relation to the disposition of other rocks of the series. Close to it, 

 to the east and south, are the bosslike or necklike ouachitite brec- 

 cias; farther to the southeast is a zone of nephelite syenite and 

 bostonite dykes, which, like the main mass, are concordant with 

 the bedding of the intruded series (the Ordovician Martinsburg 

 shale) ; finally, at some distance to the southeast, are the lampro- 

 phyric dykes, which are disposed radially toward the Beemerville 

 mass, intruding the Ordovician Kittatinny limestone and the 

 pre-Cambrian Franklin limestone. Wolff concludes that the alkalic 

 rocks are post-Devonian in age and probably much later. 



THE NEPHELITE SYENITE OF THE BEEMERVILLE MASS 



The main mass of nephelite syenite forms a long, narrow intru- 

 sion of elliptical outcrop, lying between the Silurian Shawangunk 

 conglomerate and the Ordovician Martinsburg shale, at the foot 

 of the Kittatinny Ridge, the southern extremity of the mass being 

 two miles to the northwest of Beemerville. It is most easily 

 accessible from the town of Sussex (formerly called Deckertown, 

 and referred to by that name by Emerson and Kemp) . 



The formal relationships of the mass are obscure. Both 

 Emerson and Kemp regarded it as a large dyke, but Wolff is inclined 

 to regard it as a sill, or an irregular, flat laccolithic mass. Washing- 

 ton visited the locality in 1901 in company with Professors Kemp 

 and Brogger, and is in agreement with Wolff's opinion. It was 

 examined by Aurousseau in the summer of 192 1, with special 

 regard to this point, but no evidence of a decisive nature is obtainable 

 on the ground. As the mass has been studied by a number of com- 

 petent geologists at intervals over a long period of time, it is improb- 

 able that any fuller information will be forthcoming, the outcrops 

 being poor and the contacts obscured by thick soil and drift. 

 In particular, no variations of dip are to be observed in the massive 

 Shawangunk conglomerate which overhes the mass. To our minds 

 the occurrence of the body (which can hardly be younger than 



