GEOLOGY OF THE POUGHKEEPSIE QUADRANGLE . 89 



crops with one doubtful exception. Along the bank of the creek, 

 one mile northeast of Skidmore's farm, a mass of limestone about 

 fifteen feet square was found between the road and the brook. At 

 the base it is made up of coarse limestone conglomerate, which is 

 followed by arenaceous limestone. This is succeeded by a finer- 

 grained conglomerate. The apparent strike is n. 25° w. and the 

 dip 34° n.e. This was regarded as a boulder. It strongly 

 resembles similar beds found in place to the northwest. It hardl)^ 

 seems probable that this small ledge would have been preserved in 

 its present position. 



It is reasonably apparent that these two limestone patches have 

 been brought to their present position by overthrust faulting, involv- 

 ing a horizontal displacement of at least one-half a mile. At 

 Skidmore's the Hmestone has been eroded so as to expose the slates 

 on which it has been thrust. The small ledge at Houghtalin's is 

 only part of a scarp which is for the most part concealed. 



The valley southwest of these two limestone patches is plainly in 

 the slate. There is strong suggestion that it is along a line of strike 

 faulting that extends from the Highlands northward beyond the 

 limits of the quadrangle. The view which shows this best is that 

 obtained from the western slope of the ridge southwest of Moores 

 Mill. The conspicuous scarp on the west of the high hill west of 

 Lagrangeville, which is seen so distinctly from Freedom Plains, lies 

 along this line of faulting, while the northeastward continuation 

 of the latter is marked by a hollow plainly visible at the elevation 

 of the viewpoint just mentioned. 



East of Pleasant Valley. Three limestone masses are faulted 

 in with the slates east of Pleasant Valley. The largest of these is 

 farthest east of the three and is shown on the map along the north 

 road from Moores Mill to Pleasant Valley. A small ledge of the 

 limestone outcrops among the slates one-fourth of a mile south of 

 the fork in the roads near Ivy's house. This is separated from the 

 main portion of the mass along the road by slates. East of Ivy's 

 house, occupying practically all of the small triangle formed by the 

 roads as shown on the map, and north of here for several hundred 

 yards, are ledges of conglomeratic limestone interbedded with 

 silicious limestones (silicicalcarenytes^) and limy shales. The dip 

 is eastward. Low ledges of limestone outcrop on both sides of the 

 road east of Ivy's. On the east side of the road the conglomeratic 



1 A name proposed by Professor A. W. Grabau for silicious limestones 

 with sandy texture. 



