322 



BULLETIN or THE 



Becraft's Mountain (but not for Rondout 1). Leconte, on I know not 

 Vhat authority, takes a view opposite from the generally accepted one 

 given by Dana. Liudscy and Dale both represent the junction at 

 Rondout as an unconformity. 



West of Catskill, I am persuaded that no unconformity exists : the 

 evidence for this conclusion is given below. Becraft's Mountain and its 

 smaller neighbor I have not seen, except from the railroad in passing : 

 the opinions concerning this important point are contradictory, Mather 

 and Rogers being opposed to Emmons and Hall, About Rondout no 

 disagreement is directly expressed except by Emmons ; and yet none of 

 the observations or figures of the hill-sections in that district are con- 

 clusive; none enable the reader completely to exclude the possibility of 

 the apparent unconformity being really a junction by faulting. It 

 would seem, therefore, that all this subject needs reviewing. 



The observations on which I rely to prove the conformable sequence 

 of the strata in the district hero mapped are as follows : — 



First. At the north end of French's Quarry Hill, by a good spring on 

 the middle one of the tiirec roads that run around the slope, there is a 

 contact of sandstone and an impure limestone clearly shown for some 

 ten feet. The rocks here lie horizontal in the axis of a synclinal fold ; 

 their strata are closely parallel, and evenly superimposed ; going down 

 hill several outcrops of sandstone may be found ; ascending to the south, 

 the several limestones of the Lower Helderbcrg group are easily recog- 

 nized in proper order; going east or west, the Hudson River strata soon 

 rise from the synclinal axis, becoming steeper and steeper by gradual 

 change. 



4 



Second. In the road and railroad cuts just east of Austin's Mill on 

 the Catskill, the absolute contact is hidden by about ten foot of detritus, 

 but the strata show only parallel arcs of the eastern half of a synclinal 

 (see fig. 3). The apparent unconformity in the limestones here shown 

 is due to horizontal faulting in the trough of the fold, as is described 

 farther on. 



Third. Along the front bluff of the Kalk Berg, generally marked by 

 vertical strata of Waterlimc and Lower Pentamerus, the sandstones are 

 also vertical and parallel in strike; in the anticlinal valleys within the 

 belt, the sandstone is perfectly conformable to the curves of the lime- 

 stones, but no absolute contacts were found. 



Wo therefore must conclude that the entire series is conformable in 

 this district, and is folded together; and so it is represented on our 

 Bections. 



