GEOLOGY OF THE POUGHKEEPSIE QUADRANGLE 43 



of Bailey's, the quartzite was brought against the limestone marking 

 a diminishing tendency in the thrust to the east. As shown on the 

 map portions of the quartzite are yet preserved near the quadrangle 

 boundary. Where the quartzite could not be found the gneiss is 

 represented as resting against the limestone; but in some cases, as 

 discussed above, the quartzite may have once been present. 



The wide swamp east of Bailey's marks the northeastward con- 

 tinuation of the great thrust fault along the limestone-quartzite 

 contact. 



Petrography and general description. This formation has 

 great uniformity of appearance and general character throughout 

 the area. Its principal variations may be stated very briefly. The 

 predominating variety is a compact, granular quartz-rock of medium 

 grain. This grades into a fine conglomerate at the base in a few 

 places and in others at the top into finer-grained quartzitic shales. 

 The predominating variety is either white or pinkish in color. 

 Feldspathic varieties are rare. 



Within the quadrangle there does not appear to be any apprecia- 

 ble difference in metamorphism in this formation from west to 

 east. At the type locality at Poughquag there is indication of a 

 gneissoid character. Within this quadrangle the quartzite appar- 

 ently never was involved violently enough to induce this structure. 



The thin-bedded varieties, often with shaly character, were noted 

 at the northern end of the Hook spur south of the Hupfel estate, 

 in the steep bed of the brook in the East Hook near the quadrangle 

 boundary, north of Shenandoah and at Hortontown. Conglomeratic 

 phases were seen southwest of Johnsville near Honness mountain, 

 south of the Thomas Carey farm in the West Hook and north of 

 the McCarthy place to the east of Ward Ladue's. 



Strikes and dips in this formation vary greatly. In Matteawan 

 good observations could not be made in the thick quartzite south of 

 Anderson street nor at the foot of the Mount Beacon incline. Read- 

 ings taken just south of the Maddock residence gave a strike of 

 n. 75° e. and a dip of 54° n. w. The gneiss, only 30 

 feet away, dipped 50° to the southeast. Observations at the 

 quartzite ledge at the extremity of the Bald hill spur gave a strike 

 of n. 42° e. and a dip of 48° to the northwest. A reading 

 taken on the east of Honness gave a strike of n. 42° e. and a 

 dip of 35° southeast. South of the Carey farm in the West 

 Hook the dip is 15° to the northeast. On the farms of Garrett Smith 

 and Ward Ladue, west of the fault, the dip is to the north- 



