CHAPTER XI 

 STRUCTURE OF PEEKSKILL CREEK VALLEY 



Immediately east of Sprout brook, described in the previous sec- 

 tion, is Peekskill creek, which drains the largest valley emerging 

 from the southern margin of the Highlands. This valley as a 

 physiographic feature is continuous with the Hudson river gorge 

 from the sharp bend at Peekskill to Tompkins Cove. There are 

 important structural features along the strike of this valley which 

 extend very far beyond the limits of Peekskill creek itself, among 

 which are strong folding and block faulting. The chief fault con- 

 tinues to the southwest with still greater prominence and appears 

 on the west side of the Hudson in the escarpment forming the 

 southeastern margin of the Highlands continuously for many miles 

 into New Jersey. 



Near the Hudson, Peekskill creek and Sprout brook unite and 

 the structures and formations characteristic of each valley converge 

 until in the last half mile of their united course rock formations 

 characteristic of Sprout brook lie on one side of the valley, those 

 characteristic of Peekskill creek on the other, and the contact which 

 follows the divide to that point then passes beneath the waters of 

 Peekskill inlet. Because of the block faulting which has carried 

 down overlying formations and protected them from the total de- 

 struction characteristic of the central Highlands region this valley 

 is of unusual interest. 



Explorations ^ 



The aqueduct line crosses this valley about 3 miles from the 

 Hudson, and in determining the possibility of crossing by pressure 

 tunnel in rock a considerable number of explorations were made. 



Enough has been done to outline the rock floor profile very defi- 

 nitely and to determine the condition of the formations. 



An examination of the drill cores and records of explorations 

 shows the following facts which are compiled as fully as possible 

 on the accompanying cross section. 



Phyllite. One boring (no. i) is in a phyllite whose character 

 and relation to other formations leads to the conclusion that it 



1 These explorations were directed by Mr A. A. Sproul, division engineer 

 of the Peekskill division with headquarters at Peekskill, N. Y. 



17s 



