STATE GEOLOGIC MAP OF 1901 



11 



GEOLOGIC PROVINCES OF NEW YORK 



The geologic formations of New York, by their lithologic 

 influence on its physiography and topography, separate them- 

 selves into several natural divisions, which have invited and 

 held the attention of many geologists who have devoted them- 

 selves to the study of one or another area according to their 

 personal interest and experience. 



The more prominent of these which have been made subjects 

 of special study are the Adirondack crystallines, southeastern 

 crystallines, metamorphic rocks of the New England border or 

 Taconic range, Silurian and Lower Devonian rocks of the 

 Mohawk valley region and the Upper Devonian rocks. 



Adirondack crystallines 



With the exception of a few unimportant papers previously 

 published, geologic work on the pre-Cambrian rocks of the 

 Adirondacks dates from 1837, the first year of field work of the 

 Oeological Survey of New York. In the division of the work 

 adopted, by far the larger portion of the area in question fell 

 to the share of Emmons, Vanuxem's district touching it in 

 Lewis, Herkimer and Fulton counties only, while Mather had a 

 small portion in Saratoga and Washington counties. Emmons 

 described various classes of rock in his annual reports and in 

 the final report on the second district, which appeared in 1842. 

 These divisions were based on lithologic differences and were 

 not shown on the 1842 map, on which the entire central mass 

 of the Adirondacks is colored in one tint as " Primary." From 

 1842 till a comparatively recent date, little or no field work of 

 value was carried on in that area, many of the papers published 

 being in relation to the adoption of the names " Huronian " and 

 M Laurentian " of Canadian geologists for subdivisions of the 

 Adirondack series. 



In 1895 Prof. J. F. Kemp, at the suggestion of the writer, 

 took up a study of the region of the iron mines near Port Henry. 

 The results of this work appeared in Museum bulletin 14. Sub- 

 sequently work was continued under the direction of Prof. James 

 Hall from 1896 to 1898, the study of the Adirondack area being 

 •divided between Professors Kemp, Cushing and Smyth. 



