REPORT OF THE STATE PALEONTOLOGIST 1902 1071 

 TECTONIC FEATURES 



Becraft mountain is an isolated remnant of the Helderberg 

 mountains and partakes of the general structure of the Appa- 

 lachian system of which it forms a part. It is not the only 

 remnant of the Helderbergs on the east of the Hudson river, 

 for a few miles to the northeast lies Mount Bob, which is an 

 abbreviated edition of Becraft having suffered all but complete 

 destruction by erosion. 



Whether Becraft mountain represents a fault block of the 

 Helderbergs dropped down among the " Hudson river" strata 

 and so preserved from erosion, or whether its low lying position 

 with reference to the Hudson river beds surrounding it, is due 

 to the fact that it forms an axis of a particularly deep syncline, 

 which during the peneplenation of the surrounding country was 

 too low to suffer erosion, is not easy to determine. Certainly, 

 if the strata on the west of the mountain were continued 

 upward at the same angle with which they now dip into the 

 mountain, they would pass above the highest point of Mount 

 Moreno, which is the highest mass of Hudson river strata lying 

 between Becraft and the Helderbergs. The fact also that Mount 

 Bob, lying in the direction of strike of the Becraft strata, has 

 a synclinal structure, indicates that they are one and the same 

 part of the low lying synclinorium. 



The main synclinal axis (no. 1) of the Becraft mountain 

 synclinorium runs about through the center of the mountain. 

 The western limb is simple, but the eastern limb is strongly 

 folded and faulted. Two anticlines (no. 1 and 2) and two more 

 synclines (no. 2 and 3) are readily traceable over the eastern 

 half of the mountain. The eastern limb of the third syncline 

 (no. 3) forms the western limb of a third anticline (no. 3), this 

 anticline being complete in only one locality [see sections 12-15], 

 where it is followed eastward by another syncline (no. 4) and 

 finally by a small symmetric anticline (no. 4). Besides these 

 there are several minor folds between the major ones. The 

 principal folds (anticlines 1, 2 and 3) a*re strongly asymmetric, 

 their western limbs varying from steeply inclined through 

 perpendicular to strongly overturned. In addition to this, the 



