SECTIONS IN POTOMAC RIVER VALLEY. 



95 



IV. Section of center of bluff at Potomac Creel-. 



Feet 

 Pleistocene Fine yellowish sand containini>- red and 



brown bands 15 



Miocene White gritty clay, with Miocene fossils at 



base 5 



Eocene. Nanjenioy Potapaco Greenish-gray argillaceous sand, slightly 



glauconitic (Zone 15) 38 



Argillaceous sand containing bands of selenite 



crystals ( Zone 14 ) 4 



Light-gray glauconitic sand with Veneri- 



cardia potapacoeiisis (Zone 13) 3 



Greenish-gray argillaceous sand (Zone 12).. 8 

 Indurated greensand with Venericardia pota- 



pacoensis (Zone 11) 1 



Greenish-gray argillaceous sand, glauconitic, 



with casts of Meretrix (Zone 10) 25 



Aquia Paspotansa Thick-bedded arenaceous and glauconitic 

 limestone interstratified with layers of par- 

 tially weathered greensand, the indurated 

 strata largely composed of the shells of 



Turritella mortoni (Zone 9) 12 



Greensand bed, much weathered in its upper 

 portions, and filled chiefly with Turritella 

 mortoni in several thick layers ; also T. 

 humerosa, Cucullaea gigantea, Crassatel- 

 lites alaeformis, Ostrea compressirostra, 

 and many other species (Zone 8) 25 



Total 136 



v. Section on Potomac Bun, near Potomac Church.'^ 



Feet 

 Eocene. Aquia Very fine, loose, slightly argillaceous, yellow 



sand with imprints of shells sparingly 



shown 20 



Greenish-yellow and yellow, fine argillaceous 

 sand, with many imprints of shells, espec- 

 ially in its lower portion forming a green- 

 sand marl 10 



Brownish-yellow sandy clay, spotted with 



white 4 



Dark gray clay, mottled with brown 5 



Gray argillaceous sand, with small pebbles.. 3 

 Brownish sandy clay speckled and mottled 



with gray and white 3 



Thick mass, only partially exposed, of fine 

 argillaceous and variegated incoherent sand 40 



Lower Cretaceous. Patapsco Potomac cobblestone bed 3-4 



Friable reddish-brown sand 2i/^ 



Dark-gray, coarse, somewhat argillaceous 



sand ( exposed ) 2-3 



Total 941/2 



oBull. U. S. Geol. Survey, No. 145, p. 76. 



