440 N. H. DARTON — LATER FORMATIONS OF VIRGINIA AND MARYLAND. 



Nottoway River. — The southernmost exposure of the Pauiunkey forma- 

 tion is a small outcrop near Boilings bridge, which I have not visited. 



Appomattox River. — At Petersburg the formation is represented by a few 

 feet of slightly glauconitic black sands containing casts of Eocene moUusca. 

 This is exposed lying on the Potomac gravels just northwest of the city, and 

 again in the depression at the city water-works, where it is capped by Chesa- 

 peake beds. 



James River. — In the James river depression and up its side branches the 

 Pamuukey formation is extensively exposed. At Richmond the thin edge 

 of the formation consists of black sands similar to those at Petersburg, and it 

 is exposed lying between Chesapeake and Potomac beds in the Shockoe creek 

 depression. 



Descending the James, for several miles the edge of the formation lies 

 some distance back from the river bluffs, and is more or less overlapped by 

 the Appomattox. From a short distance below Dutch gap to Coggins point 

 the formation, with its gentle easterly inclination, gradually crosses tide-level 

 and the river bluff exposures are frequent, and at some points particularly 

 fine, notably at Tar bay. The beds consists mainly of richly glauconitic 

 marls, highly fossil iferous, which are worked to some extent for fertilizers. 

 The overlying Chesapeake beds become prominent in the bluffs below City 

 Point, and in this region there is a thin local bed of white clay in the Pa- 

 munkey formation near its summit. 



Chickahominy River. — This stream was not explored, but the Pamuukey 

 formation is probably reached by the river channel for a greater or less dis- 

 tance in the district opposite the James river exposures. 



Pamuukey River. — The exposures in this depression begin just about 

 Hanover Court-House, and thence for many miles down the river they con- 

 stitute an almost continuous section. Rogers considered this section typical, 

 and described some of the outcrops in considerable detail. Glauconitic sands 

 predominate, and fossils are abundant. 



Mattaponi River. — Exposures are frequent on the Mattaponi, but are not 

 especially noteworthy. Argillaceous materials enter largely into the com- 

 ponents of the formation. 



Rappahannock River. — In this basin the outcrops of the formation occupy 

 a considerable area. West and northwest of Fredericksburg the beds of 

 buff sand lying on the Potomac formation are found to be Pamuukey in age, 

 representing beds from which the glauconite has been weathered out. Far- 

 ther eastward the glauconitic marls are seen in many excellent exposures 

 in river bluffs and side drainage depressions, capped usually by the Chesa- 

 peake beds. 



Potomac River. — The formation occupies the western side of this basin 

 from near Washington to Pope's creek, and the eastern side from Acquia 



