t146 new YORK STATE MUSEUM 



given it by the New England geologists. The name recently 

 adopted for it is Poughquag quartzite (Dana 1872) in recognition 

 of the fact that its thickness, lithologic character and strati- 

 graphic position are well shown at Poughquag, Dutchess co. 

 N. Y. A tj^pical exposure of the Poughquag quartzite occurs on 

 the south side of Peekskill creek near its junction with the 

 Hudson river. This is well shown on pi. 54, the slaty cleavage 

 of the quartzite being particularly noticeable. 



Stockbridge and Barnegat limestones 

 The Barnegat or blue limestone of Orange and southwestern 

 Dutchess county and the crystalline Stockbridge limestone of 

 the other southeastern counties and western New England, are 

 more or less highly metamorphosed equivalents of the Cambro- 

 Silurian limestones of northern Dutchess county. As a whole, 

 the Barnegat and Stockbridge formations are predominantly 

 magnesian. They rarely carry sufficient magnesia to qualify 

 as true dolomites, however; and contain occasional beds of 

 almost pure lime carbonate. 



The crystalline Cambro-Silurian limestone of Westchester 

 county was described as the Inwood limestone by Dr F. J. H. 

 Merrill in the paper previously cited. These Westchester county 

 limestones are essentially continuous, stratigraphically, with 

 the Stockbridge limestone of the Taconic region; and in order 

 to prevent two names being used for the same formation, the 

 formation name Stockbridge has been accepted as that of earlier 

 date. 



Mather in 1842 described the semicrystalline blue limestone 

 of Orange county as the Barnegat limestone. Though there 

 seems to be little doubt of the essential equivalence of the 

 Barnegat and Stockbridge, it seems best to retain both names 

 as the Stockbridge probably includes Trenton beds, which in 

 the less metamorphosed area of Orange county and New Jersey 

 can be differentiated from the Barnegat. South of the New 

 York line the names Kittatinny and Wallkill have been applied 

 to the Barnegat limestone, but these can hardly be regarded as 

 tenable in view of the manv other names of earlier date. 



