HUDSON RIVER BEDS NEAR ALBANY 553 



up the deeper beds in the east, and, therefore, not interfere with 

 our conclusion as to the stratigraphic position of the Dicello- 

 graptus zone. But slickensides and small faults abound in all 

 folded regions, while the presence of numerous small folds as 

 far west as the Vly and throughout the whole territory, as well 

 as the bounding of the area by powerfully folded parts of the 

 €rust in the east (Taconic mountains), in the south by the lime- 

 stone belts which traverse the shales and in the southwest by the 

 folded parts of the Helderberg region, makes the explanation of 

 the inversion of the beds by a system of shearing joints appear 

 rather forced and suggests that the inversion is the result of 

 overfolding. The writer much prefers the latter view, as it con- 

 siders the inverted system of beds as a whole and as not neces- 

 sarily involving a great disturbance of the original succession. 

 It does away with those elements of uncertainty as to the un- 

 broken succession of the four zones which would be involved in 

 the assumption of inversion by an overthrust system. Argu- 

 ments in support of this view are therefore here presented. 



It is an established fact that the numerous folds of the Ap- 

 palachian mountain system have their steepest slopes facing the 

 northwest or the interior of the continent and are more or less 

 overturned in that direction. The presence of the Appalachian 

 system of folds in the middle Hudson valley region was first sug- 

 gested by Mather (4) and asserted by Hall (15), who proved the 

 existence in the Catskills of four lines of very low anticlinals, 

 nearly parallel to each other and running from southwest to 

 northeast in conformity with the ordinary trend of the Appalach- 

 ian ranges; the synclinals occupying the summits, the anticlinals 

 the bottom of the valleys. This discovery has been verified by 

 Arnold Guyot (25). 



Two years later the existence of folds of true Appalachian type 

 in the region between the Catskill mountains and the Hudson 

 river was reported by N. S. Shaler (18). On the other side of the 

 river it was found by James D. Dana that the schists of Hudson 

 river age dip under the limestone of Trenton-Calciferous age in 

 the limestone belts of Dutchess county and western Connecticut. 



