REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1900 rl45 



basic) lower gneisses are oyerlain by a highly foliated gneiss, 

 described by Dr F. J. H. Merrill as the Fordham gneiss. This is a 

 well banded bluish to gray gneiss, consisting of alternating lay- 

 ers of quartz, orthoclase (or microcline) and mica (usually 

 biotite). 



Lithologic differences, fairly constant over large areas, have 

 led to a tentative fourfold division of the pre-Fordham gneisses; 

 but the grouping depends on composition rather than on super- 

 position, and has therefore no chronologic significance. The 

 names for these subdivisions have been used, in manuscript 

 only, by the present writer: and the subdivisions will not be 

 discussed in the present connection. 



Various authors have included in the pre-Cambrian both the 

 large area of white limestone of Sussex county, N. J. and 

 Orange county, N. Y. and smaller isolated areas which occur in 

 the Highlands of Putnam and Orange counties. Recent field 

 work by the writer in these smaller areas seems to disprove 

 this conclusion, at least so far as some areas are concerned; 

 and it is probable that the entire question may still be con- 

 sidered open. In the present paper, however, these Highland 

 limestones have been discussed separately from the undoubtedly 

 Paleozoic limestones and marbles. Lithologically, these white 

 limestones differ but slightly if at all from the more highly 

 crystalline portions of the Stockbridge, and like the Stockbridge 

 and Barnegat are usually highly magnesian. 



Poughquag quartsite 



In Dutchess, Orange, Putnam and Westchester counties a 

 relatively thin quartzite usually underlies the Cambro-Silurian 

 limestones. In Stissing mountain and at other points this 

 quartzite has been found to contain Lower Cambrian (Georgian) 

 fossils. It is essentially continuous, stratigraphically, through- 

 out the counties above named, few contacts of the Stockbridge 

 limestone with the pre-Cambrian gneisses failing to show this 

 intervening quartzite. In its lithologic character it is very uni- 

 form. Dr Merrill described it in 1896 as the Lowerre quartzite, 

 while the formation names Vermont and Cheshire have been 



