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NEW YORK STATE MUSEUM 



events in the history of the Adirondacks, but also gain an under- 

 standing of some of the fundamental methods and principles of 

 earth science (geology). 



The exact placing of the very ancient Adirondack rocks in the 

 geologic time-table (see page 12) is a difficult matter, through the 

 Grenville series is, in the light of the strongest evidence, to be 

 classed with the Archeoz.oic or oldest known rock group. For the 

 younger Adirondack rocks (below discussed) which are so closely 



Fig. S Generalized geologic map of northern New York showing 

 the distribution of the principal rock systems. Unshaded portion; 

 Prepaleozoic rocks, chiefly Grenville strata, syenite, and granite ; 

 dotted portion: Prepaleozoic rock, chiefly anorthosite ; horizontal- 

 lined areas: Cambrian and Ordovician strata; cross-lined area: 

 Silurian strata; small black patches: isolated areas of Paleozoic strata. 



associated with the Grenville, the evidence is not so clear. They 

 may be partly Archeozoic and partly Proterozoic or they may be 

 wholly Proterozoic. In any case we are certain that they are all 

 earlier than the Paleozoic because very early Paleozoic strata rest 

 upon them around most of the borders of the Adirondacks. 



