POTOMAC KIVEE SECTIONS. 



69 



Virginia. The Patapsco i? found on Potomac Creek about a mile below 

 the railroad crossing and on Aquia Creek, in the vicinity of the railroad 

 bridge, and at tide on the Eappahannoek Eiver near the mouth of the 

 Massaponax Eiver. There are also numerous exposures and fossiliferous 

 outcrops in tlie area around Brooke. A single exposure of positively 

 determinable age is found in the valley of the James Eiver at Deep Bottom 

 4 mile? below Dutch Gap canal at the most eastern point where the Potomac 

 deposits appear above tide. From these points it rises rapidly to the west 

 along the sides of the valleys and forms the tops of the hills, except for the 

 thin covering of Eocene. Lafayette, or Pleistocene materials which overlie it. 



DETAILED SECTIONS. 



poto:mac kivek skctioxs. 



The Potomac strata outcrop at intervals along the Virginia bank of the 

 Potomac Eiver from Alexandria almost to the mouth of Aquia Creek. The 

 first locality worthy of mention is on the Mt. Vernon estate a short distance 

 below the steamboat landing. This and other exposures in the immediate 

 vicinity and up Doag Creek are very poor and much covered, but as they 

 are very fossiliferous they merit some description. At several points along 

 the base of this bluff 10-15 feet of Potomac materials are exposed. These 

 consist of arkosic, irregularly-bedded, light sands, more or less indurated 

 with thin layers of more argillaceous materials brownish or pinkish in color 

 and carrying leaf impressions which are usually somewhat contorted. The 

 materials are all of Patapsco age and the more important forms found 

 include the following: 



Acrostichopteris lotifiipctniis Font. 

 Antholites Gaudiiim-Rosae Ward 

 Aralia ? venioncnsis Font. 

 Aristolochiaephylhnn * cellulare Ward 

 Casuarina Covillei Ward 

 CelastrophyUuin Britfonianuin Hollick 

 CelastrophiiUum Hunteri Ward 

 CcIastrophyUtun ? saliciforme Ward 

 Cladophlebis rotuudata Font. 

 Ephcd rites ? icrtionensis Font. 

 \elunibites tcnuineriis (Font.) Berry 

 Xehimbites virgiiiiensis (Font.) Berry 

 Xagciopsis angustifolia Font. 

 Xageiop^is longifolia Font. ? 

 Oiit/chipsis Guepp< rti (Sehenk) Berry 



Pinus vemonensis Ward 

 PopuJophyUum minutum Ward 

 PopulophyUum renifonne Font. 

 Popuhts potomaccnsis Ward 

 Potaniogetophyllum vernonense Font. 

 Sagittaria Tictor-Masoni Ward 

 Dicksoniopsis vcrrwnensis (Ward) Berry 

 Sphcnolepis Sternbergianum (Dunk.) 



Schenk 

 Thyrsopteris grevillioides (Heer) Hollick 

 Sterculia elegans Font. ? 

 Thixtifcldia Foutainei Berry 

 Widdringtonites ramosus (Font.) Berry 

 Zamites temtinervis Font. 



