22 NEW YORK STATE MUSEUM 



V 



REPORT ON THE GEOLOGICAL SURVEY 



The progress of the areal geological survey of the State on the 

 topographic scale of one mile to the inch has now progressed so far 

 as to make it possible to reconstruct a geological map of the entire 

 State on a smaller scale. There still remain considerable areas 

 unsurveyed but for the most part these are bounded by other areas 

 whose topography and geology are known, and on a lesser-scale 

 map their surfaces might be covered with geological boundaries with 

 approximate accuracy. There has been no geological map of the 

 entire State issued since 1901, eighteen years ago. The progress 

 of detailed field observation has made a new edition of the map 

 on a scale of 5 miles to the inch almost imperative to meet the 

 demands of commerce and of the schools. The creation of a new 

 base map has been the chief obstacle to this procedure. The 

 map of 1 90 1 and the previous map of 1894 had a very imperfect 

 base due to the fact that but little of the topographic survey had 

 been done. The provision recently made by the Legislature for 

 the production of a base map of the State on the scale of 4 miles 

 to the inch which can be used for various departmental purposes 

 would have helped forward this plan although the scale is larger 

 than that we have hitherto used but not too large for the great 

 amount of detail which a geological map must now of necessity 

 carry. Unfortunately the provision thus made failed to meet the 

 approval of the Governor. 



Lyon Mountain Quadrangle. Dr William J. Miller reports his 

 operations in this region as follows : " 



With the exception of the glacial and postglacial deposits, all the 

 rocks of the quadrangle are of Precambrian age. Oldest of all are 

 a few small remnants of the Grenville series badly cut to pieces and 

 more or less assimilated and highly injected by the intrusive rocks. 



So far as known, the next oldest rocks are gabbro and hornblende 

 gneiss or amphibolite. Much of the gabbro, which usually has an 

 ophitic texture and is very massive, is clearly older than the granites 

 of the region, and younger than the Grenville, as shown by the 

 field relations. Some of the gabbro, as is well known for the Adiron- 

 dacks in general, may be younger than the syenite-granite series, 

 but no positive proof for such younger gabbro was obtained. In 

 many places the true gabbro grades into hornblende gneiss or amphi- 

 bolite. But it is by no means certain that all the hornblende gneiss 



