110 



NEW YORK STATE MUSEUM 



and similar narrow terraces are not wanting farther from the 

 main stream on Peekskill and Sprout brooks at gradually in- 

 creasing hights above sea level. Those on the north side of the 

 cove are best developed ; and of these that forming the state camp 

 is the broadest of all. 1 am not able to say how much it has been 

 artificially graded. The slope of this terrace with its kamelike 

 projections is quite unlike that of normal river-cut terraces on 

 the one hand and lobate delta fronts on the other; the deposit 

 appears to have been built in the presence of ice partially filling 

 Peekskill creek. The same remark applies to the narrow terrace 

 at the mouth of Annsville creek near the head of the same cove. 



Roa Hook is an outlying rudely conical hill of glacial materials 

 rising to the same level as the terraces in its vicinity. It has been 

 opened for gravel and sand. On its top is a fine yellowish loam, 

 from 3 to 5 feet thick ; below this a dark coarse gravel bed, 10 to 

 15 feet thick, in which one large erratic was exposed in 1900; 

 below which sands occur in the form of foreset beds dipping south- 

 east, making a section about 30 feet thick. Near the railroad 

 track sands occur dipping southeast at an angle of 15°. The 

 gravels are locally cemented by carbonate of lime. 



The dark shaly pebbles in these gravels are derived from the 

 paleozoic rocks north of the Highlands in the Hudson valley. 

 This northern source of the materials and the dip of the sand beds 

 to the southeast show the direction of building of the deposit to 

 have been downstream. The isolation of this deposit is hardly 

 to be explained by the erosion of a once larger and more extended 

 mass of glacial gravels and sands uniting all the terraces about 

 Peekskill creek in a single deposit. The contours of the slopes 

 or bluffs of these terraces as well as the untouched slopes of the 

 Roa Hook mass preclude that idea ; and the postulate of masses of 

 ice partly filling the channel at this point and shrinking away 

 from the rock walls here and there and so permitting the build- 

 ing up of deltas and terraces by lateral streams to a nearly 

 common level meets all the requirements as regards the irregu- 

 larity in outline and disposition of the various deposits. 



A notable feature in the deposits of the vicinity of Peekskill 

 is the complete absence of the superficial stratified glacial clays. 

 Dr Ries has described clays rising about 4 feet above high tide 

 level beneath the gravel and sand of the 20 foot terrace south of 



