:544 C. SCHUCHERT SILURIAN FORMATIONS 



Great break. All of Richmondian absent. 



Hudson River shales, or older formations. 



Otisville, New York. — Thirty-five miles southwest of Rondout Valley. 

 Section across Shawangunk or Kittatinny Mountain. See Cook : Geology 

 of New Jersey, 1868, pages 146, 150; Lesley: Second Geological Survey 

 of Pennsylvania, Final Eeport, volume I, 1892, pages 676-678, and volume 

 II, 1892, page 733 ; Clarke and Euedemann : Memoir 14, New York State 

 Museum, 1912, pages 91, 93, 104. 



Silurian. Cayugan series. 



Longwood shales. A thick series of brick-red sandy shales interbedded 

 with reddish and gray sandstones, greenish shales, and occasional 

 very impure water limestones. All are much sun-cracked (the cal- 

 careous beds at times break out in prismatic columns ; see plate 20, 

 figure 1) and rippled. In the water limestones a few Salinan Ostra- 

 coda were seen. The basal beds of this red series are exposed at 

 mile-post 81.25 from Jersey City on the Erie Railroad, or a little south 

 of Graham station, some miles to the southwest of Otisville ; but the 

 actual contact with the Shawangunk was not seen. However, the 

 relation elsewhere shows that the red shales are disconformable with 

 the quartzite. Cook gives the thickness as at least 800 feet, but it 

 appears to be much more. 



Great break. All of Niagaran absent. 



Silurian. 



Shawangunk quartzite, about 800 feet thick (see plate 20, figure 2). The 

 upper 150 feet of the Shawangunk is devoid of conglomerate and is 

 more commonly a greenish sandy shale with more or less of red shales 

 interbedded with yellowish and reddish sandstones. The red beds are 

 in the middle of this zone and are sun-cracked and finely rippled, with 

 the crests from .75 to 1.50 inches apart ; here the sandstones are also 

 thicker than they are below, ranging between 1 and 4 feet. As 

 Arthrojihycus occurs in the lower part of this upper zone, this part 

 at least is also of Medina age. It should be added, however, that the 

 uppermost beds are very near or may actually be in the transition to 

 the Clinton. This conclusion is supported by the olive-green sandy 

 shales that have a silky-looking surface, on which are the remains of 

 Buthotrephis gracilis, a fossil that is especially common in the lower 

 part of the Clinton. Pterinea emacerata also appears to be present. 

 The rest of the Shawangunk, 650 feet in thickness, consists of thin- 

 bedded conglomeratic quartzites (1 to IS inches, thick), coarse in grain 

 below and finer above, and cross-bedded throughout. In the lower 

 125 feet there is also considerable channeling. The pebbles are of 

 vein quartz, subrounded, larger below, but averaging .25 inch through- 

 out the greater part of the Shawangunk. Below, the sandstones are 

 dark in color, probably due to admixtures of the Hudson River shales ; 

 but upward they are lighter in color and of greenish white cast. 

 Interbedded are many lenses of black shale, varying from .25 to 6 

 inches thick, with the greatest amount near the middle of the forma- 



