THE GEOLOGY OF THE CRYSTALLINE ROCKS 

 OF CECIL COUNTY 



BY 



BASCOM 



Introductory. 



The discussion of the succeeding pages will be confined to the belt 

 of metamorphic and igneous formations which appear at the surface 

 in the northern and northwestern half of Cecil county. South of a 

 line extending from Perryville to Iron Hill Station they are com- 

 pletely concealed, with the exception of a few scattered outliers, by 

 the gravels, clays and sands of the Cretaceous, Tertiary and Pleis- 

 tocene. North of this line there are light coverings of Potomac and 

 Columbia gravel, which exhibit very irregular boundaries upon the 

 crystallines and possess numerous inliers. 



The areal distribution, stratigraphy, structural relations, age and 

 petrography of the formations of this district will be the special 

 subjects of the following pages. 



The physiography and soils of the region are fully dealt with else- 

 where and will be only incidentally considered here. 



The bibliography of this belt is included in the general bibliography 

 of Cecil county (pp. 49-62) and a summary of previous investigations 

 is given elsewhere (pp. 39-41). The most detailed investigations, 

 and the only petrographic studies, of the crystallines are represented 

 by A. G. Leonard's Dissertation 1 " The Basic Pocks of Northeastern 

 Maryland and their Relation to the Granite," and by G. P. Grims- 

 ley's Dissertation 2 " The Granites of Cecil County " in Northeastern 

 Maryland, which were prepared at the Johns Hopkins University. 



1 Amer. Geol., vol. xxviii, 1901, pp. 135-176, plates xv-xix. 



ajourn. Cincinnati Soc. Nat. Hist., vol. xvii, 1894, pp. 56-67, 87-114. 



