UNIVERSITY OF VIRGINIA PUBLICATIONS 



BULLETIN OF THE PHILOSOPHICAL SOCIETY 



SCIENTIFIC SECTION 



Vol. I, No. 16, pp. 341-347 May, 1913 



NORMAL FAULTING IN THE CAMBRIAN OF NORTHERN 

 PIEDMONT VIRGINIA.* 



BY 



THOMAS L. WATSON .ind JUSTUS H. CLINE 



A belt of Lower Cambrian rocksf, roughly paralleling the Blue Ridge 

 and lying just beyond its southeast slope, extends almost entirely across 

 Virginia in a northeast-southwest direction. The western limits of this 

 belt .are fairly well known and are delineated with reasonable accuracy; 

 its eastern limits are yet somewhat in doubt and not so accurately drawn 

 because of lack chiefly of detailed field studies. A line connecting the 

 cities of Warrenton, Charlottesville, and Lynchburg gives both the approx- 

 imate trend and location of this belt. Its width is variable and the belt 

 presumably occupies a sjoiclinal trough in the pre-Cambrian crystallines 

 of the Piedmont Plateau. 



What members of the Lower Cambrian are represented in this belt has 

 not been definitely determined. Much of it, in places at least, is the 

 Loudoun formation which has an estimated thickness up to 800 feet. It 

 is composed of material derived from the pre-Cambrian intrusive granitic 

 rocks and extrusive basalts (Catoctin schist). Its basal portions are 

 coarse arkosic and quartzitic sandstones, which grade upward into finer 

 grained sediments, originally shales, in part graphitic intercalated with 

 thin beds of sandstone, and in places a very coarse conglomerate. Lime- 

 stone lenses of variable thickness and length are common in places through- 

 out the extent of the belt. /" 



In the southern portion of the belt the structurey^ while not worked 

 out in detail, shows in places steeper dips of a more closed type of folding, 



*Read before Scientific Section, April, 1913. 



t Watson, Thomas L., Geological map of Virainia, Virginia Geological Survey, 

 1911. 



341 



NOV 14 1913 



