Appalachian Geosyncline. 235 



held, and that the differences in the rocks are such as are to be 

 expected under the view that they were deposited nearer to 

 the sources of erosion, but existed in continuity with synchro- 

 nous sediments laid down in Pennsylvania. Grabau also has 

 recently urged the view regarding the continuity of the Silu- 

 rian rocks of this axis with those to the west.* 



The history of the region must be traced from the Silurian. 

 Early in the Silurian the Green Pond conglomerate was laid 

 down with a thickness of 1200 to 1500 feet. 



" This consists of coarse, silicious conglomerate, interbedded 

 with and grading upward into quartzite and sandstones. The 

 pebbles of the conglomerate range from one-half to three inches 

 in diameter, and are almost entirely white quartz, but some pink 

 quartz, black, white, yellow and red chert, red and purple quartz- 

 ite, and a very few red shale and pink jasper pebbles occur. 

 The white quartz pebbles have frequently a pink tinge on their 

 outer portion. At Gould's quarry large masses of the underlying- 

 limestone are included in a conglomerate, which is believed to be 

 the basal layers of this formation. 



" The matrix is comprised of quartz sand, is vitreous in texture 

 and generally of a dull red color, but white, gray and greenish 

 strata frequently occur, particularly in the basal portion, so that 

 the formation is not so exclusively red as implied in most of the 

 earlier reports." f 



The Shawangunk conglomerate and sandstone, in similar 

 stratigraphic position, outcrops twenty miles northwestward, is 

 1500 to 1600 feet thick, but is without the red color, — con- 

 sisting of cleaner, whiter sand and smaller quartz pebbles. 

 This contrast suggests either that the Shawangunk has been 

 subjected to the greater sorting due to wave action and con- 

 trasts with a fluviatile origin of the Green Pond conglomerate, 

 or that the latter corresponds to the red upper portion of the 

 Silurian sandstone to the west, the basal portion being absent 

 in the Green Pond axis. 



The evidence shows that in neither the Green Pond axis 

 nor to the west is the material of local origin. An enormous 

 quantity of rock and from a considerable area has been 

 destroyed to supply this mass, the pebbles consisting domi- 

 nantly of white quartz-vein material from crystalline forma- 

 tions. Considerable transportation has been necessary in order 

 to segregate it from the vastly greater quantity of finer 

 grained and softer rock with which it was associated, a trans- 

 portation to which the rounded form and resistant character of 

 the pebbles bear witness. Furthermore, except to some degree 

 at the unconformable base, local bowlders are not encountered 



* Early Paleozoic Delta Deposits of North America, Ball. Geol. Soc. Am., 

 xxiv, 477-479, 1913. 



f Kummel and Weller, loc. cit., p. 9., 



