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NEW YORK STATE MUSEUM 



within the limits of the sheet, nor are any known within the im- 

 mediately surrounding territory. The prevailing rocks over a 

 large part of the northern Adirondack foothill region are gneisses 

 of doubtful, though for the most part probably of igneous origin, 

 which are distinctly older than the unmistakably igneous rocks. 

 Such rocks are at the surface in the territory comprised in the 

 southwestern part of the sheet. The term, Dannemora formation, 

 is suggested as a convenient one to apply to these widespread 

 rocks on the north, in our present state of ignorance concerning 

 their age and relationships, as they are well exposed all over the 

 mass of Dannemora mountain as well as throughout Dannemora 

 township. The problem of their age, and their relationship to the 

 undoubted sedimentary rocks, is by far the most important un- 

 solved stratigraphic question in the district. Most unfortunately 

 there is practically no opportunity afforded for its settlement, 

 since in the region where the Dannemora formation prevails the 

 other rocks are wellnign absent, and no contracts where these 

 relations might be shown and studied, are exposed. Nearly all 

 the exposures of the sedimentary rocks in Clinton and Franklin 

 counties are surrounded by the later eruptive rocks instead of the 

 Dannemora formation. Whether therefore the Dannemora rocks 

 are older, younger, or of the same age as the sedimentary (Gren- 

 ville) rocks does not appear, and the evidence must be forthcom- 

 ing elsewhere, probably from the western Adirondacks, 1 



1 Every geologist who has visited the Adirondack region has remarked 

 on the great similarity, if it be not identity, of the pre-Cambrian rocks 

 to the Canadian rocks to the northward. This is specially true of the 

 igneous rocks and those of sedimentary origin (long ago named the 

 Grenville series by Logan). There is also there a supposedly older series 

 of gneisses known as the Ottawa gneiss. The term, Ottawa gneiss, is 

 not used in this report simply because it is not yet determined whether 

 the Dannemora gneiss is the representative of the Ottawa gneiss in the 

 Adirondacks, or whether it represents rocks which are classed with the 

 Grenville series in Canada, or whether it represents neither. The term, 

 Grenville, is used for the sedimentary series because the similarity be- 

 tween these rocks in the two districts has been noted by every observer 

 who has gone into the field, and it is exceedingly probable that they 

 were deposited in the same basin. Smyth has suggested the name, 

 Oswegatchie series, for these rocks in the western Adirondacks, on the 

 ground that their similarity with the Canadian rocks does not neces- 



