18 NEW YORK STATE MUSEUM 
was not able to contribute any very positive information on this 
important question he concluded that “All the suggestive evidence, 
however, favors the view taken by Prof. W. W. Mather and subse- 
quently elaborated by Prof. J. D. Dana, viz: that the rocks of the 
Manhattan group (Merrill presumably includes equivalent types in 
Westchester and Putnam counties) are the metamorphosed equiva- 
lents of the Paleozoic beds of southern Dutchess county.” (p. 391) 
Merrill was unable to find an unconformable contact between the 
rocks of the Manhattan group and the underlying Precambrian 
crystallines, which was the chief factor of doubt in his conclusions. 
Later work *° did not cause him to alter his opinion, for he 
inferred, from the relation of the quartzite, limestone and schist 
of Westchester county to the underlying gneiss, that the crystalline 
limestone of Westchester county was equivalent to the limestone of 
Dutchess county (the Wappinger limestone), the age of which had 
“been satisfactorily established by the work of Dwight, Dana and 
others to be calciferous-Trenton.” By analogy the schist and 
“micaceous gneiss” overlying the crystalline limestones were cor- 
related with the Hudson River group in New York county, which 
Merrill had already determined to be the metamorphosed equivalents 
of the Cambro-Ordovician sediments of Dutchess county. Merrill 
was convinced of the correctness of his determinations of the age 
relations of these rocks, and six years later ** described them and 
mapped them as metamorphosed Cambrian, Cambro-Ordovician and 
Silurian sediments. This view is still maintained by some geologists 
at the present time, although Berkey,*? in connection with some of 
his studies of the geology of the Highlands of southeastern New 
York, while recognizing the age relations to be a question of great 
complexity and considerable difference of opinion, concluded that 
these rocks were not the metamorphosed equivalents of Cambro- 
Ordovician sediments, but instead were Precambrian in age. The 
differences of opinion have been due in part to the failure of other 
workers in this field to recognize the significance of the great 
structural breaks of the region. In his description of the complex 
faulting Berkey stated: “The net result is a preservation of 
representatives of the later group of formations (Cambro-Siluric) 
30 Merrill, F. J. H. The Geology of the Crystalline Rocks of South- 
eastern New York. N. Y. State Mus. Annual Rep’t 50. 1806. 
31 Frederick J. H. Merrill on the Metamorphic Crystalline Rock. New 
Worle (City IROIO 8}, We Ss Co Sod) woo, 
82 Berkey, C. P. Structural and Stratigraphic Features of the Basal Gneisses 
of the Highlands. N. Y. State Mus. Bul. 107, p. 361-78. 1907. 
