GEOLOGY OF THE POUGHKEEPSIE QUADRANGLE 7 1 



this quadrangle occurs as a great fault-bounded block north of the 

 Fishkill mountains. Northeastward it may be followed up the 

 Clove valley, east of which it passes under the mass of schist com- 

 posing Chestnut ridge and reappears in the Dover-Pawling valley. 



The overlying slate formation has been removed from this 

 faulted limestone mass within this quadrangle, which makes it con- 

 venient to discuss the mass as a unit. 



Boundaries. The northern boundary enters the quadrangle 

 from the town of Beekman and extends southwestward along the 

 old roadbed of the Clove branch of the Newburgh, Dutchess and 

 Connecticut Railroad to a point about one mile east of old Hopewell, 

 where it intersects a northwest-southeast fault and turns with a 

 sharp angle to the northwest. The actual contact of limestone and 

 slate usually can not be seen, but the field relations and obvious fault 

 features approximately determine the course of the boundary. 

 Somewhere south of Arthursburg, the actual point being concealed, 

 the boundary again turns abruptly, this time to the southwest, as 

 shown on the map. and follows the valle}^ of the Whortlekill to a 

 point just w^est of .Hopewell Junction, and then turns to the north- 

 west to follow the fault previously referred to, along the raliroad. 

 Three-fourths of a mile west of here a ledge of shaly limestone 

 marks the northwest limit of the limestone along this fault line. 

 The slates extend down into the included angles of these fault lines, 

 as shown on the map. Southwest from the ledge of shaly limestone 

 fust mentioned the boundary is easily followed across the fields, 

 often with a clear scarp or other distinct topographic feature, and 

 with slate and limestone frequently in close proximity, to the fault 

 that bounds My mountain on the east ; then north along this 

 fault, with the slates again in the included angle, to M}' mountain, 

 which is bounded by the limestone on the south. Southwest of Vly 

 mountain the limestone bounds the Glenham belt to the carpet mill 

 at Glenham. South of here it is faulted against the slates for half 

 a mile, then rests against the gneiss of the northernmost inlier in 

 the town of IMatteawan, then on the quartzite patch just south of 

 this, and again on the gneiss. 



Its southern margin has been described sufficiently in connection 

 with the gneisses and the quartzite. 



Terranes present. The fossil localities so far discovered in 

 this limestone are limited in number and in distribution. The Lower 

 Cambric (Georgian), Beekmantown and Trenton have been 

 definitely identified. In the systematic and extensive examination 

 of outcrops in cuts and weathered surfaces, suggestive markings 



