alcott] NEW JERSEY AND DELAWARE. 123 



stone resting uncoil form ably on the gneiss and passing conformably be- 

 neath the superjacent Magnesian limestone. 1 There are also doubtfully 

 included under the u Potsdam sandstone" several outcrops of quart- 

 zite and conglomerate, and the conglomerates and sandstones of the 

 Green Pond Mountain range. On the large geological map of northern 

 New Jersey, published in 1874, 2 the " Potsdam sandstone n includes 

 shales, sandstones, slaty grits, quartz rock, and the Green Pond Moun- 

 tain conglomerate ; this entire series is represented by one color, 

 extending on the trend of the Green Pond Mountain range from the 

 New York boundary southwesterly into the central portion of Morris 

 County. 



-In the annual report for 1884 the Green Pond Mountain rocks are 

 included with the <* Devonian and Silurian rocks." 3 This leaves the 

 so-called " Potsdam sandstone " as the only Cambrian formation within 

 the State. The following year reference is made by Prof. Cook 4 to the 

 contact phenomena with the Paleozoic rocks. In New Jersey one point 

 is at u Owen's Island," in Sussex County, two-thirds of a mile south of 

 the State line, as described by Prof. Rogers in his report of 1836. At 

 this point the sandstone dips 20° northwest, and the Archean 70° to 

 the southwest. Near Franklin Furnace a similar unconformity occurs, 

 and the same conditions appear persistent aloug the entire northwestern 

 margin of the highlands in New Jersey, though no other actual contact 

 has been observed along this line. 



In a paper presented to the Geological Society of America December 

 31, 1890, Prof. Frank L. Nason stated he had found fossils of Lower 

 Cambrian age in the quartzite resting on the pre-Paleozoic rocks at 

 Hardistoiiville, Sussex County, New Jersey, and at Franklin Furnace, 

 in the same county. He also discovered fragments of a species of 

 Kutorgina in the superjacent limestone. 5 



DELAWARE. 



In the northwestern corner of the State of Delaware there is a trian- 

 gular area of sandstone referred to the "Potsdam " sandstone by Mr. 

 Fred. D. Chester. He states that it extends into Pennsylvania, and is 

 best exposed beyond the State line. 



At Nivin's limestone quarry a mass of quartzite forms what is clearly an anticlinal 

 fold, over which is a corresponding anticlinal of Magnesian limestone. 6 



The extension of this sandstone iuto Pennsylvania is shown upon the 

 map of Chester County, Pennsylvania, where it occurs in the township 

 of London. 



1 Geology of New Jersey. Newark, 1868, p. 72. 



J Cook, Geo. H. Geological Survey of New Jersey. (Map of) northern New Jersey, showing the 

 Iron-ore and limestone districts. 1874, in two sheets. 



s Cook, Geo. H. Geological Survey of New Jersey. Annual report of the State geologist for the 

 year 1884. 1884, p. 29. 



'Contact phenomena with the Paleozoic rocks. Geological Survey of New Jersey. Annual Report 

 of the State Geol. for 1885. Trenton, 1885, pp. 53-55. » 



'Unpublished. 



•Preliminary notes on the geology of Delaware — Laurentian, Paleozoic, and Cretaceous areas. Phila. 

 Acad. Sci. Proc, vol. 36, 1884, p. 248. 



