310 Walcott — Occurrence of Olenellus in New Jersey. 



ing operations and dips beneath a conglomerate formed of 

 white quartz pebbles, essentially the same as those in the con- 

 glomerate beneath the limestone. As in the section one mile 

 to the north, an interval of slate occurs between the low ridge 

 formed by the limestone and associated rocks and the massive 

 conglomerate of Kanouse Mountain on the west. The dis- 

 covery of the Olenellus fauna in the limestone is a positive 

 addition to the data for working out the stratigraphy of the 

 Green Pond Mountain area. Occurring, as it does, in a lime- 

 stone that merges above and below into beds of conglomerate 

 that are essentially of the Green Pond Mountain type, it 

 proves that the conditions under which this characteristic 

 formation was formed began in lower Cambrian time. 



In a recent paper Mr. A. F. Foerste* states that " Since the 

 rocks all dip west the conglomerates forming the eastern side 

 of Copperas and Kanouse Mountains must be Oneida, the red 

 sandstone above the same, the Medina, the underlying lime- 

 stone, the Magnesian limestone, and the basal sandstone, the 

 Cambrian ; but instead of the term Potsdam it is necessary 

 now until further developments, to call it Olenellus Cambrian. 

 It is a quaitzite sandstone from ten to fifteen feet thick, and 

 so far has not furnished fossils." 



The danger of correlation by lithological characteristics is 

 shown by the reference of the limestone in which I found 

 Olenellus to the Magnesian limestone of the Pennsylvania 

 and New York sections. The use of the term " Olenellus 

 Cambrian" for the sandstone or quartzite is objectionable. In 

 the absence of fossils the correlation of the basal sandstone of 

 one basin of sedimentation with the basal sandstone of another 

 basin of sedimentation must necessarily be more or less con- 

 jectural. 



In the report of 1868 Dr. Geo. H. Cook, the then state 

 geologist, referred the conglomerates of Copperas and Kanouse 

 Mountains to the Potsdam epoch of the New York series on 

 account of their being at the base of the Paleozoic series. 

 Mr. Foerste is now confident that they are of the age of the 

 Oneida conglomerate of the New York section. From the 

 data at present available it may be that the latter is correct ; 

 but, from the fact that the sediments of the Green Pond 

 Mountain area were deposited in a basin distinct from that to 

 the west and north, it is evident that any attempt to make 

 exact correlations between the rock series of this basin and 

 that of the more extensive basin of New York, western New 

 Jersey, and Pennsylvania will be more or less theoretical. 

 The sedimentation of the Green Pond Mountain area of New 



*This Journal, vol. xlvi, 1893, p. 441. 



