344 E. B. MATHEWS — MARYLAND AND PENNSYLVANIA PIEDMONT 



across the Washington quadrangle and thence continuing probably as 

 far as the Fredericksburg region. 



Eastern Piedmont of Virginia 



Our knowledge of the Piedmont formations in Virginia is by no means 

 equal to that of Pennsylvania and Maryland, since little or no work has 

 been done in the area between the Blue Ridge on the west and the Coastal 

 Plain deposits on the east since the days of the Rogers. There have ap- 

 peared, however, occasional local descriptions of limited areas, and these 

 the present writer has attempted to correlate with the facts given in the 

 early reports of the Virginia survey, and these correlations have in a 

 measure been checked by personal reconnaissance as far south as the 

 James river. It should not be thought, however, that the following 

 statements are regarded as any more than a working hypothesis, which 

 may aid in the ultimate interpretation of the Virginia Piedmont. 



A study of the Piedmont geology of Virginia from the literature im- 

 presses the student at once with several generalizations, the strongest of 

 which is that in all of the previous work little or no attempt has been 

 made by the different students to recognize and map the different forma- 

 tions within the limits of the Piedmont east of the mountains. A second 

 impression from the descriptions published is that formations similar to 

 those recognized in Maryland extend across the state of Virginia with a 

 trend similar to that of the Blue Ridge and the Shenandoah valley farther 

 west, with the exception, however, that the limestones and marbles are 

 apparently absent in any extensive development comparable to the areas 

 of Cocke} 7 sville marble in the Maryland region. On the other hand, the 

 little lenses of marble which have been recognized and but little studied 

 in the western part of the Maryland Piedmont may be traced, where the 

 older rocks are not obscured by the Triasgic sandstones, all along the 

 western side of the Virginia Piedmont from the Rapidan to the Staunton 

 river and probably to the North Carolina line. 



Again, it may be noticed that the igneous rocks occupy similar posi- 

 tions in Virginia to those in Maryland, with the exception that they are 

 relatively less abundant, and, so far as the facts at hand indicate, are 

 usually granite and not gabbro, although the writer has found hornblende 

 schist in the valley of the James which probably represents metamor- 

 phosed gabbros, and the lithologic descriptions suggest that gabbroic 

 rocks, more or less metamorphosed, may be found in several parts of the 

 state. The principal masses of granite so far recognized are (1) the south- 

 ward continuation of the granite of the Catoctin belt recognized by Keith,* 



♦Fourteenth Ann. Rept. U. S. Geo!. Survey, pp. 285-395. 



