SKUNNEMUNK CONGLOMERATE. 371 



out some local features of structure and stratigraphy which showed very 

 clearly that the Green Pond conglomerate was approximately Oneida in 

 age, and that the shales west of Green Pond mountain were Lower Devo- 

 nian. He states near the conclusion of his report that this " Oneida " con- 

 glomerate extends northward along the western ridge of Bearfort moun- 

 tain, but no extended examination was made of the region. Cook gave 

 a section in his report as state geologist for 1885,* in which a central ridge 

 of the mountain is shown as " Oneida conglomerate " (?) flanked by 

 '' Hudson river slate." This, as will be shown later, is an error, for the 

 conglomerates are the Skunnemunk beds and the associated flags and 

 shales are of Hamilton age. ^ 



' In the New Jersey map for 1889 Cook colored the conglomerates of 

 Bearfort, Green Pond, Kanouse, Bowling Green and Copperas mountain 

 as " Potsdam," and the slates in the adjoining slopes and valleys as 

 *' Hudson river." 



In 1892 Mr C. S. Prosser j gave a resume of previous writings on the 

 belt, and discussed at length the age of the plant beds in Skunnemunk 

 mountain which are considered Middle Devonian in horizon. 



In 1893 Mr A. F. Foerste J made a short visit to the region about New- 

 foundland, and states his opinion that the conglomerate is Oneida, and 

 the red quartzite Medina in age. 



Skunnemunk Conglomerate. — In its typical development this formation 

 is an aggregation of quartz and quartzite pebbles and bowlders in a red 

 or reddish quartzitic matrix. It is very hard in texture and massively 

 bedded. The i:)ebbles and bowlders in greater part average from one to 

 two inches in diameter. Some are five and six inches in diameter ; 

 many are from three to four inches, and they are mostly well rounded, 

 but a moderate proportion of them are subangular. They are closely 

 packed in the matrix. White, glassy quartz predominates somewhat, 

 and the contrast of this material with the red color of the matrix gives 

 a characteristic aspect to the rock. The quartzite pebbles are mostly 

 dark red brown in color and they sometimes include pebbles of quartz. 

 More or less finer fragmental products, consisting mainly of white quartz, 

 red quartzite and red argillaceous materials, are included in the matrix. 



In Skunnemunk mountain the conglomerate constitutes the two high 

 crests which extend along the center of the range, and for some distance 

 it also floors the deep intervening valley. The general relation of these 

 features is shown in sections I and II of plate 17. 



The mountain is everywhere rugged, but the conglomerate area is ex- 



* Trenton, 1885, plate opposite page 109, 



t Notes on the Geologj' of Skunnemunk Mountain, Orange County, Xevv York: Trans. New York 

 Acad. Sciences, vol. 11, pp. 13L''-151. 

 X Am. Jour. Sci., 3d ser., vol. xlvi, pp. 440-441. 



