2 THE OLDER MESOZOIC FLORA OP VIRGINIA. 



The younger Mesozoic strata have very little in common with those 

 just described, but by most geologists they have been grouped with them 

 as forming a portion of the so-called Trias of Virginia. 



This group of younger Mesozoic beds forms an interrupted and narrow 

 belt, that extends north and south on the eastern margin of the Azoic rocks, 

 outcropping between them and the Tertiary formation. The beds of this 

 group show themselves, as a rule, only where the overlying Tertiary has 

 been eroded away. In Virginia they are not known south of the city of 

 Petersburg. 



Numerous plants are to be found in them. These plants possess many 

 interesting features, and show that the flora of this group is totally different 

 from that of the older Mesozoic. 



The areas occupied by the older Mesozoic beds, taken in order from 

 east to west, have the following locations : 



The most easterly of these is the one that may be named the Rich- 

 mond Area, since its eastern edge passes about 10 miles west of Richmond. 

 This is by far the most important area of Mesozoic in Virginia, since it con- 

 tains nearly all the workable coal and yields nearly all of the plants found 

 in the older Mesozoic. It forms an elliptical belt which has its longer axis 

 directed a little east of north. For this reason to the north it is overlapped 

 by the Tertiary formation, since this latter extends with its western edge 

 almost due north and south. The length of the Richmond Area is about 

 30 miles, beginning at the south on the Appomattox River, and ending at 

 the north in Caroline County, about 3 miles north of Hanover Junction. 

 The average width is about 6 miles. This area shows a synclinal structure 

 in the Mesozoic strata, the rocks on the east side dipping northwest and 

 those on the west side dipping southeast. Coal has been worked on both 

 sides of this area. The workings on the west side, however, are few and 

 confined to the vicinity of James River. The openings for coal on the 

 east side are more numerous and important. They are found on the extreme 

 northern end, exclusive of the portion in Hanover, and extend, but with 

 long intervals, to the extreme southern end. 



That portion of this area that extends north of the Chickahominy 

 River, lying mostly in Hanover County, contains no workable coal. This 



