40 NEW YORK STATE MUSEUM 



AREAL GEOLOGY 



In the work directed toward the completion of the great geological 

 map of the State on a scale basis of one mile to the inch, some progress 

 was accomplished although conditions made it obligatory to curtail 

 the work somewhat and much of it was interrupted in the course 

 of the season. Prof. H. P. Cushing, who has been connected with 

 the areal survey of the Adirondacks for more than twenty years, 

 completed his survey of the Gouverneur quadrangle and his final 

 report is now in preparation. 



Gouverneur quadrangle. A report upon the progress of the work 

 was made in 191 6, in which the absence of large areas of intrusive 

 rocks was commented upon, and at the same time the frequency of 

 granite sills intruded into the Grenville strata was noted, and the 

 contrast between this district, with its abundant and continuous 

 Grenville exposures and lack of large bodies of intrusives, and the 

 main Adirondack region to the east and south was set forth. The 

 granite sills are regarded as upward protrusions from a large body 

 of syenite below ground, which followed the Grenville structures 

 as the lines of least resistance, and the contrast with the more easterly 

 region is attributed to lesser altitude and erosion in the Gouverneur 

 region. 



The most important result of the 191 7 field work was the 

 demonstration afforded of the closely folded structure of the Gren- 

 ville rocks in the region, which lie in a series of closely appressed, 

 pitching, isoclinal folds. The relationships between the Grenville 

 rocks and the granite sills suggest that the folding occurred before 

 the intrusion of the sills. These matters will be discussed in detail 

 in the final report. 



Lake Placid quadrangle. The final report on this field was com- 

 pleted by Prof. W. J. Miller and is now in course of printing. 



Schroon Lake quadrangle. This area was also completed during 

 the summer of 191 7, and its geology shows many features of much 

 interest, as an unusually fine display of many types of Adirondack 

 rocks occurs within the quadrangle. 



Grenville strata mappable as such occupy about 12 square miles 

 of the quadrangle. The largest areas are in the vicinity of Minerva 

 and Olmstedville. Many other masses are simply small and large 

 inclusions in the syenite-granite series. All the usual types of 

 Grenville, as well as some interesting structures were observed. 



The oldest intrusive of the region is the anorthosite, which exhibits 

 two rather well-defined, mappable facies. Of these, the Marcy 



