POTOMAC RIVER SECTIONS. 



III. Section at Freestone Point. 



71 



Pleistocene 



Feet 

 Light cross-bedded iron-stained sands with peb- 

 bles and clay pellets 0-20 



Eocene. Aquia ( ? ) 



Argillaceous greensand 4-8 



Lower Cretaceous. Patuxent Gray cross-bedded coarse arkosic sand with 



indurated ledges and scattered pellets and 

 lenses and balls of greenish argillaceous 

 materials, very variable horizontally and 



vertically 40-50 



Gray indurated cross-bedded arkosic sand.... 30 



Total 74-108 



IV. Section at Cockpit Point. 



Pleistocene 



Feet 

 Iron-stained sandy loam with gravel at the 



base 15-20 



Lower Cretaceous. Patuxent 



Buff cross-bedded sand with some lignite and a 

 few clay balls, carrying leaf impressions in 

 the more argillaceous layers. These include 

 Cladophlehis parva Font., Dioonites Buchi- 

 anus (Ett) Born., Equisetum Burchardti 

 (Dunk.) Brongn., Feistmantelia oblonga 

 Ward, Nageiopsis zamioides Font., Nageiop- 

 sis longifoUa Font., Podozamites sp., Sclerop- 

 teris elliptica Font., Sequoia amhigua Heer, 

 Sphenolepis Kttrrianum (Dunk.) Schenk, 

 Sphenolepis Sternhergiana (Dunk.) Ony- 

 chiopsis Goepperti (Schenk) Berry, etc. 



18 



Greenish, massive, ehloritic, sandy clay 10 



Total , 



43-48 



This and the preceding are the only decisive exposures of Patuxent on 

 the Potomac Eiver and evidently owe their preservation to the resistant 

 character of the Patuxent materials, which are firmly indurated, forming 

 the well-known "freestone" formerly much quarried in this vicinity. The 

 unconformable nature of the Patuxent-Patapsco contact is well shown, since 

 about a mile south directly along the strike a characteristic Patapsco flora 

 is found at a somewhat lower level. 



