IO NEW YORK STATE MUSEUM 



GENERAL GEOLOGY 



Principal publications. The geology of the Adirondacks was 

 investigated in the early part of the last century by Prof. E. 

 Emmons under commission of the Natural History Survey of New 

 York State. The final report of Emmons, which was published in 

 1842, contains a vast collection of observations on the topography, 

 rocks, stratigraphy and mineral resources of the region, consti- 

 tuting a valuable reference work to this day. The notes on the iron 

 ores and the iron mining industry are commendable for their detail 

 and accuracy. Professor Emmons considered the rocks to be mainly 

 " primary " and divided them into the classes of unstratified, 

 stratified and subordinate. Among the unstratified rocks he 

 grouped granite, hypersthene rock (anorthosite) , limestone, ser- 

 pentine, and rensselaerite. The stratified class included gneiss, 

 hornblende (hornblende gneiss and amphibolite) , syenite and talc. 

 The subordinate rocks were porphyry, trap, magnetite and specular 

 iron ores. The stratigraphic sequence of the formations received 

 little attention as, indeed, the question involved problems that 

 could scarcely be met by the methods and opportunities which 

 were at Professor Emmons's disposal. 



A paper by C. E. Hall, published in the report of the New York 

 State Museum for 1878, contains a description of some of the iron 

 ore deposits of the eastern Adirondacks. The ores are stated to be 

 associated with the following rock groups: Lower Laurentian 

 magnetic iron ore series; Laurentian sulfur ore series; and the 

 Upper Laurentian, or limestones and Labrador series, with titanic 

 iron ores. In a note to the article the classification is amended by 

 placing the limestones in a separate group with an unconformity 

 at their base where they rest upon the Upper Laurentian. 



In the last 15 years a geological investigation of the Adirondacks, 

 wider in scope than any previously undertaken, has been in progress 

 under the direction of the State Geologist. The field work has been 

 carried out principally by Prof. J. F. Kemp, C. H. Smyth jr, and 

 H. P. Cushing. Their efforts until recently have been directed 

 toward a general reconnaissance as a preliminary to a detailed 

 survey which was necessarily deferred until accurate base maps 

 could be prepared. The results have appeared from time to time 

 in the bulletins and reports of the New York State Museum. Much 

 has been done to clear up the main problems connected with the 

 lithologic and stratigraphic relations of the rocks, and it may be 

 said that the principles for the interpretation of the geology of the 



