Darton and Keith — Dikes of Felsophyre and Basalt, etc. 305 



Art. XXIX. — On Dikes of Felsophyre and Basalt hi Paleo- 

 zoic Bocks in Centred Appalachian Virginia ;* by N. H. 

 Darton, IT. S. Geological Survey. With notes on the 

 Petrography by Arthur Keith, U. S. Geological Survey. 



The occurrence of igneous rocks in the central and northern 

 Appalachians is very unusual, for the detailed work in various 

 portions of the province from Alabama to New York has only 

 resulted in the discovery of a dike in central Pennsylvania and 

 the small group of dikes west of Staunton, Yirginia, which I 

 described in 1890. f 



l. 



Eig. 1. — Map of a portion of central Appalachian Virginia showing location of dikes. 



In 1896 I had opportunity to extend my observations farther 

 west and discovered^: additional basalt dikes and a very inter- 

 esting series of dikes of an acid character which Mr. Keith has 

 found should be classified as " felsophyre." The region in 

 which all these dikes occur is an area of about 120 square miles, 

 lying mainly in Highland County, in the central western portion 

 of Yirginia. Two dikes were found in the adjoining portion 

 of Pendleton County, West Yirginia. The region is in the 



* Published by permission of the Director of the U. S. Geological Survey. 

 fThis Journal, vol. xxxix, pp. 269-271, with petrographic notes by Mr. J. S. 

 Diller. 



{Announced at meeting of Geological Society of America, Dec. 28, 1896. 



