GEOLOGY OF THE POUGHKEEPSIE QUADRANGLE 6^ 



The lower portion of the Calciferous shows many thick, grayish 

 layers in places. 



Apparently the Beekmantown has a wide distribution in this 

 strip. It forms the main mass of the high hill northwest of the 

 Trenton in the cut at Pleasant Valley and may be traced rather 

 satisfactorily as a lithic unit to Rochdale, where it is seen to have a 

 great thickness, estimated at from looo to 1200 feet. D wight 

 claimed to have traced it definitely to a point five miles below 

 Poughkeepsie (see above). The beds resting on the slates at the 

 New Hamburg tunnel are probably of Beekmantown age. 



At Rochdale the Beekmantown in places passes through a heavy 

 conglomerate into the Trenton which rests upon it. Just a little way 

 south of a ledge of this conglomerate on the property of Henry Titus, 

 along the road, are fine exposures of the bluish-gray beds. These give 

 place at the west to the gray and dove-colored beds which compose 

 most of the hill between Rochdale and the Pleasant Valley turnpike. 



The bluish-gray beds were noted farther south near the eastern 

 margin just north of the break in this strip. Taking the apparent 

 thickness at Rochdale as a guide, the beds intervening between these 

 blue beds and the scarp just east of Tompkins's house are probably 

 all Beekmantown. South of here the lithology does not convey 

 very much, though indicating on the whole the southward continu- 

 ation of the lower portion of the Beekmantown as shown at Roch- 

 dale. 



Within this strip farther south, about one-fourth mile north of 

 the Spackenkill road, along an old wood road, or cow patH, are 

 probable beds of the Beekmantown within a few rods of coarse 

 Trenton conglomerate apparently carrying Solenopora com- 

 pact a. The road from the orchard on the north side of the 

 Spackenkill road, opposite the old Boardman farm, leads to these 

 outcrops. This locality is seemingly not so far south as Professor 

 Dwight claimed to have traced the Beekmantown; but the writer 

 has not been able to add anything definite to the age of this belt to 

 the south of this point. 



The Trenton, within this strip, is usually a dark blue rather 

 crystalline rock of quite different appearance from the Beekman- 

 town, Its lower portion is conglomeratic and carries colonies of 

 the coral S. compacta which, without careful examination, 

 might be taken for pebbles. This coral, or a conglomerate appear- 

 ance, is often the only means for identifying this member of the 

 limestone formation. The Trenton is also somewhat finely con- 

 glomeratic at times. The conglomerate was noted at Pleasant 



