PYROXENITE 



233 



II. Pyroxenite, Johnny Cake Road, Baltimore County, Maryland. J. E. Whit- 

 field, analyst. G. H. Williams : American Geologist, volume vi,. 1890, 

 page 41. 

 III. Websterite, Webster, North Carolina. E. A. Schneider, analyst. G. H. 

 Williams : American Geologist, volume vi, 1890, page 44 ; also Bulletin 

 148, United States Geological Survey, 1897, page 92. 



Norms* 5 of Pyroxenites corresponding to Analyses on page 232 



Q 



Or 



Ab 



2.78 

 7.34 



An 12.51 



Di 53.60 



Hy :. 13.10 



Ol 4 . 48 



Mt 2.32 



II 3.65 



Ap 34 



Summary of Classification 



II 



9.2 

 41.4 

 33.8 

 12.2 



2.1 



III 



1.7 



2.6 



32.7 

 57.1 



5.1 



umber. 



Symbol. 



Name. 



I 



IV. 1'. 1'. 2(3). 2. 



no name 



II 



V. 1. 1. 2. 2. 



baltimorose 



III 



V. 1. 1. 2. 1. 



websterose 



Age Eelations 



In the northern Blue Ridge of Virginia the syenite traced at irregular 

 intervals along the west side of the mountains southward from Dickeys 

 Hill, in Warren County, is found in more or less intimate association 

 with the Catoctin schist of Algonkian age. The Catoctin is a dark-col- 

 ored, dense, and heavy basaltic rock, two varieties of which have been 

 recognized by Keith, 46 a lower diabasic sheet and an upper basaltic sheet, 

 both altered, sometimes highly schistose, with the upper one largely epi- 

 dotized. In his discussion and mapping of the igneous rocks in this part 

 of the Blue Ridge, Keith 47 has clearly shown that all are Precambrian, and 

 that the sequence of events involves the granite intrusion [including 

 syenite] between the diabase eruptive and the diabase flow. 



Farther south, in the middle Blue Ridge region, the basal conglomerates 

 of the Lower Cambrian series contain frequent well-rounded pebbles of 

 the pyroxene syenite on which the sediments rest. The evidence is con- 



45 Calculated by Dr. H. S. Washington. 



48 Arthur Keith : Fourteenth Ann. Rept., U. S. Geol. Survey, part ii, 1892-1893, pp. 

 285-395. 



* 7 Arthur Keith : Ibid., pp. 296-318. 



XVIII— Bull. Geol. Soc. Am., Vol. 27, 1915 



