[Annals N, Y. Acad. Sci., Vol. XITI, Xo. 6, pp. 419-430, Jan. 14, 1901.] 



PRELIMINARY NOTES ON THE OCCURRENCE OE 

 SERPENTINE AND TALC AT EASTON, PENNA. 



■ F. B. Peck 



[Plate XVI ; text figures 4, 5] 



(Read January 30, 1900) 



The band of pre-Cambrian rocks which extends across the 

 northern part of New Jersey in a southwesterly direction, crosses 

 the eastern border of the State of Pennsylvania between Easton 

 on the north and Kintnersville on the south. The band is here 

 broken into a series of parallel ridges consisting chiefly of horn- 

 blende gneiss with intervening valleys of dolomites of post- A 1- 

 gonkian age. 



The northernmost of these ridges is the southwestern exten- 

 sion of Scott's Mountain in New Jersey and crosses the Dela- 

 ware river just north of Easton. On the Pennsylvania side of 

 the river it is known as Chestnut Hill. Just across the river on 

 the New Jersey side it is known as Marble Mountain. 



Chestnut Hill is a rather sharp, even-crested ridge, ha\ing a 

 maximum altitude of 700 feet above tide, and having a general 

 trend of S. 60° W. It diminishes in altitude toward the south- 

 west, and at a distance of four and one-half miles from the Del- 

 aware river disappears under the post-Algonkin dolomites. 

 This, with two other similar ridges north and west of Bethle- 

 hem, twelve miles distant, constitutes the only recurrence of 

 pre-Cambrian rocks in Pennsylvania north of the Lehigh River. 

 A description of it as regards composition and structure will 

 constitute the substance of this paper. 



Chestnut Hill is composed of a dense hornblende gneiss with 

 distinct bedding planes which dip at an angle of from 40° to 60° 

 to the southeast. Interstratified in the gneisses are beds of car- 



(419) 



