1076 



NEW YORK STATE MUSEUM 



forms a synclinal trough, the axis of which dips 10° southward. 

 The appearance of this portion of the surface is therefore some- 

 thing like half of a shallow basin. On the western side of the 

 trough the rocks are sharply overturned, so that they dip 8<> 3 

 to the eastward, but with their uppermost side down. This 

 overturn fold bounds a flat bottomed tract or longitudinal val- 

 ley. On tracing the fold southwestward along the strike, it is 

 found that less and less of the upper Manlius strata are uncov- 

 ered in the axis of the fold ; and that, finally, they are covered en- 

 tirely by the Coeymans limestone. This again shows the south- 

 ward pitch of the fold. As shown by the eastern ends Gf sections 

 14 and 15, the strata there are involved in another simple anti- 

 clinal fold (no. 4), which, from the southward pitch, is formed on 

 the present surface by progressively higher and higher strata in 

 that direction. The western boundary of the aforementioned 

 longitudinal, flat bottomed depression [section 14] is formed 

 by a double ridge of Becraft, the eastern portion of which dips 

 60° eastward, while in the western ridge the dips are 25° to 30° to 

 the west. A little farther south [in section 15] only the west- 

 ward dipping ridges of Becraft, capped by Port Ewen and under- 

 lain by New Scotland, occur. This shows that a fault line passes 

 between the two sections. This fault is well marked to the 

 southeastward, where the Manlius is thrust over the Coeymans. 

 This overthrust fault is finely shown in the cliff facing the road- 

 way along the eastern border of the mountain. Here the rela- 

 tions shown in the following diagram are clearly exhibited. 



This overthrust fault appears to be earlier than, or at least 

 contemporaneous with, the longitudinal strike faults (10 and 12), 

 for the latter are not seen south of the overthrust fault. This 

 fault may be traced northwestward as far as the little brook 

 which drains the great meadow. Here it appears to pass into 

 a strike fault and is not traceable any farther. As we go south 

 ward, the pitching axis of the fold reveals another fold as shown 

 by the sections [15-20]. These folds are of the typical Appala 

 chian type, with a steep, overturned limb on the west and a 

 gentler, normal limb on the cast. Eastward this eastern limb 

 again passes under and rises as the steep or overturned western 



