SECTIONS IN THE POTOMAC KIVER VALLEY. 



129 



SECTIONS IN THE POTOMAC RIVER VALLEY. 



Along the Potomac Eiver estuary the Calvert formation is finely exhib- 

 ited in the Nomini Cliffs of Westmoreland County. These rise to a 

 height of 200 feet and are so nearly vertical that it is impossible to scale 

 them in most places. They are the boldest cliffs of the northern Atlantic 

 Coastal Plain and form a striking contrast to the general topography of the 

 region. They consist of Calvert and Pleistocene (Sunderland) materials 

 exclusively. The following five sections give a fair idea of the cliffs. 



I. Section on the Potomac River^ three-quarters of a mile southeast of the 



mouth of Pope Creel-. 



Miocene. 



Calvert 



Feet 

 White diatomaceous earth 15 



II. Section of the Nomini Cliffs of tJie Potomac River, three miles below 



mouth of Pope CreeJc. 



Feet 



Pleistocene. Sunderland Reddish clay loam 12 



Band of small gravel with reddish clay loam 



matrix 2 



Reddish clay 4 



Coarse buff sand 4 



Red ferruginous sandstone 3 



Very coarse yellow argillaceous sand not well 



exposed in lower portion 20 



Miocene. Calvert Greenish-drab tough plastic clay 21 



Greenish-gray slightly indurated argillaceous 

 sand, rusty where weathered along surface 

 and making a prominent line along bluff. 

 Contains sharks teeth and mammalian 



bones 1 



Dark greenish-gray very sandy fine-grained 



clay with a few diatoms 12 



Light greenish-drab sandy clay 7 



Greenish-gray slightly indurated argilla- 

 ceous sand with shell impressions. Con- 

 tains shells of Pecten, Melina, Ecphora, 



etc 1 



Dark greenish-gray argillaceous sand grading 



into sandy clay 25 



Greenish-drab more or less arenaceous com- 

 pact clay, containing diatoms; material 

 light in weight when dry 18 



Total 130 



