126 NEW YORK STATE MUSEUM 



features is in general northeasterly and on the gentle slope is the 

 westerly one. 



It is apparent at once that the valley bottom is a complex one 

 and that its history has been somewhat obscured by the glacial 

 deposits. 



Formations. The following distinct stratigraphic units are deter- 

 minable in this valley every one of which will be cut by the tunnel 

 beginning at the west side with the youngest formations : 



Feet 



Hamilton and Marcellus flags and shales 700-+ 



Onondaga limestone 200 



Esopus gritty shales 800-+ 



Port Ewen shaley limestone including the Oriskany transition 250+ 



Becraf t crystalline limestone 75 



New Scotland shaley limestone 100 



Coe>Tnans limestone 75 



Manlius limestone including Rosendale, Cobleskill, and the cement 



beds • 100-+ 



Binnewater sandstone 50 



High Falls shale including small limestone layers 75 



Shawangunk conglomerate 250 to 350 



Hudson River slates — thickness unknown; probably more than 2000 



Approximately 4775 



These occur in belts in succession more or less regularly from 

 west to east. Most of the formations are quite uniform in the 

 Rondout valley. The Shawangunk conglomerate is probably more 

 variable than any other as shown by borings. Because of this 

 general persistence of formation it is possible to estimate approxi- 

 mately the depth at which any particular lower member lies if some 

 starting point can be identified. [For detailed description of the 

 formation, see pt i] 



Structure. The principal irregularities are structural, rather 

 than stratigraphic. The region on the west side of the valley, the 

 margin of the Catskills, is but slightly disturbed and lies very flat, 

 but the region on the east side, the Shawangunk mountain range 

 and the cement district, has an extremely complicated structure. 

 The Rondout valley, lying between them, is a transitional zone and 

 passes from gentle dip slopes and folds in the westerly side to 

 more frequent folds and thrust faults on the easterly side. In at 

 least two thirds of the valley it would appear from surface evi- 

 dence alone that the formations would dip uniformly westward, the 

 only suspicion of additional complication being given by an occa- 



