GEOLOGY AND GEOGRAPHY OF OLAY DEPOSITS 



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are therefore, properly speaking, marly clays. The clay is under- 

 lain by a bed of gravel, sand, hard pan, bowlder, till or bed rock. 

 From Albany to Catskill the underlying material is a dark gray 

 or black sand with pebbles of shale and quartz. The sand grains 

 are chiefly ground up shale, the rest being siliceous and calca- 

 reous with a few grains of feldspar and garnet. This sand can 

 often be used for tempering but at Catskill contains too much 

 lime for this purpose. 



I have not observed this underlying sand and gravel to reach a 

 greater height than 90 to 100 feet. 



From Catskill northward the clay is in most cases covered by 

 but a foot or two of loam. South of Catskill the character of the 

 overlying material varies. At Catskill a terrace extends back two 

 miles and probably more; it is deeply incised by Catskill and 

 Kaaterskill Creeks and smaller streams ; rocky islands project 

 above its surface at various points. Along the West Shore track, 

 about 150 feet south of the station, the side of the cutting consists 

 of thin alternating layers of clay and sand 27 feet thick. Above 

 this in places is nine feet of fine stratified yellowish sand. The 

 clay extends along the track for about one fourth mile uutil it meets 

 an outcrop of Hudson Kiver sandstone. On the south side of the 

 Catskill Mt. K. R. 100 feet from the bridge is an exposure of sand 

 and gravel, the pebbles being very coarse. It is presumably drift 

 material, but the exposure is an isolated one and does not show 

 its relation to other deposits of the vicinity. At Smith's Dock, 

 on the land of T. Brousseau near the river, the upper portion of 

 the terrace escarpment consists of fine stratified sand, which has 

 been excavated to a depth of 12 feet without finding clay, while 

 farther back from the river the clay extends to within two feet of 

 the terrace level. 



The Hudson Eiver shale rises steeply along the water's edge 

 from here down to Maiden, and crops out at numerous points in 

 the terrace escarpment. The clay along here is probably not of 

 great depth. Clay is found in the railroad cutting to the north 

 of Maiden station, about seven feet above the track level, and 

 clay is exposed in numerous cuttings of the West Shore Railroad, 

 from Maiden to Mt. Marion. 



From Glasco to Rondout the terrace, which is perhaps one 

 eighth mile broad at Glasco, narrows as it nears Rondout, and 



