372 DARTON — GREEN POND, N. J., TO SKUNNEMUNK MT,, N. Y. 



ceptionally so, as the formation gives rise to high cliffs and bare, rocky 

 slopes. The thickness of the conglomerate in this region has been esti- 

 mated at 300 feet by Smock, and this estimate appears to be a reasonable 

 one. In the basal beds the pebbles rapidly decrease in size and number 

 and the matrix becomes a gray sandy quartzite which constitutes a series 

 of beds of passage into the great mass of underlying flags. Owing to its 

 prominence in this mountain and the suitability of the name, it is pro- 

 posed to designate the formation the Skunnemunk conglomerate. 



In Bellvale and Bearfort mountains the Skunnemunk conglomerate 

 attains considerably greater development than it has northward, for it 

 -Y_ has a thickness of 2,500 feet in the widest and deepest part of the syn- 

 clinal. As the axis of this flexure rises to the south and to the north, 

 the amount of conglomerate infolded, gradually decreases and its area 

 finally terminates. 



The character of the formation in Bearfort and Bellvale mountains is 

 very similar to that which it has in Skunnemunk mountain. In its 

 lower members, however, it includes for some distance a basal series of 

 red slates, which are usually overlain by a greater or less amount of red 

 quartzitic sandstones. There are also local series of red slates and streaks 

 of less conglomeratic material higher up in the formation. The harder 

 beds are traversed by many small veins of quartz, which add consider- 

 ably to the bright variegation in the colors of the rock. 



As the lowest beds of the formation come into the flexure in Bellvale 

 mountain, they are seen to consist of light-colored sandy quartzites con- 

 taining few pebbles, but much checkered by small quartz veins. On 

 the road across the mountain from the northern end of Greenwood lake 

 the flags merge upward into reddish quartzite containing several red slate 

 streaks, which gives place rapidly to a thick mass of coarse typical con- 

 glomerate which constitutes the crest of the mountain. On the western 

 slope the reddish quartzite comes up on the other side of the synclinal 

 and is underlain by three to five feet of bright brown-red slates which lie 

 against the gneiss. 



South from the road the mountain widens rapidly and opposite the 

 southern end of Greenwood lake it has three crests, of which the con- 

 glomerate constitutes the two western ones. The region is very high 

 and steep, but it is crossed by two gaps near the lines of sections VII 

 and VIII, plate 17, in which there are many exposures. In the north- 

 ern gap the lower members on the eastern limb of the synclinal are red 

 quartzitic sandstones which merge into a great mass of underlying flags 

 through a series of slabby sandstones, quartzitic and reddish above and 

 softer, thinner bedded and light gray in color below. In the axis of the 

 flexure and westward there is a great thickness of red conglomerate. 



