W. B. D wight — Recent Explorations, etc. 139 



and northeast of Flemington, the dike so finely exposed near 

 Blackwell's Mills, the dike (?) near Hackensack and the sheets 

 south of JSTew Brunswick. 



The ages of the intrusive sheets of the formation are difficult 

 to estimate. Davis has called attention to the raggedness of 

 some of the contacts as evidence that the intrusion was effected 

 before the development of joints by the uplift of the forma- 

 tion, and this certainly seems very probable. 



As the stratigraphy of the Newark system of the New 

 Jersey region is not worked out, the horizons of the trap 

 masses are not known, and the sequence of their intrusion is 

 indeterminable from any evidence now in hand. For the 

 greater part of its course the Palisade trap lies just above the 

 basal arkose, which is known to overlap the crystalline rocks 

 in wells in Jersey City, and as the first Watchung trap lies on 

 basal beds near Paterson, it might be suggested that the two 

 sheets are not far distant in horizon, but in the absence of 

 definite knowledge of the comparative age of the basal rocks 

 at Paterson, and the structure and the configuration of the 

 buried Triassic shores in the intervening region, the relative 

 positions of the two sheets can only be conjectured. 



At Lawrence Brook the supposed southward continuation of 

 the Palisade trap is not far above the base of the formation, 

 but in Ten Mile Pun Mountain and Pocky Hill the strata are 

 crossed, so that at the Delaware the sheet is apparently 10,000 

 feet above the Trenton gneisses, but probably there are inter- 

 vening faults which might decrease this estimate very greatly. 



Sourland Mountain trap is apparently high in the formation, 

 but its exact or relative horizon cannot be determined until the 

 stratigraphy and structure of the region has been worked out 

 and the same is the case with the other traps of the Delaware 

 region, and the Cushetunk and Arlington traps. 



Aet. XIX. — Recent Explorations in the Wappinger Valley 

 Limestones and other formations of Dutchess Co., JV. Y.: 

 by W. B. Dwight. "With Plate VI. 



No. 7. Fossiliferous Strata of the Paradoxides Zone at Stissing 



The occurrence of fossiliferous Cambrian strata of the Pots- 

 dam group near Poughkeepsie, N. Y., and ten miles north of 

 that city at Salt Point, has been described in previous papers 

 of this series :* also the discovery by Mr. C. D. Walcott and 

 myself, in a joint trip, of fossiliferous strata of the Olenellus 

 horizon on the southern extremity of Stissing Mountain, 21 



* This Journal, Feb., 1886, and July, 1887. 



