74 THE GEOLOGY OF CALVERT COUNTY 



Beside diatoms, there are other Miocene fossils, us-Qally in the form of 

 casts, and organic remains reworked from the underlying Eocene beds. 

 Fairhaven, Anne Arundel County, where the beds are well developed, 

 has suggested the name for this division. 



The contact of the diatomaceous earth with the Eocene beds lies 

 about two feet beneath a band of silicious sandstone from -i to 8 inches 

 in thickness, which cari'ies casts of Pecten humphreysii and other Miocene 

 fossils. Above this sandstone is the diatomaceous earth proper, which 

 is about 30 feet in thickness. In the extensive pits at Lyons Creek, where 

 the material is being worked for commerce, the transition from the 

 fresh greenish-blue to weathered buff color may be seen in the masses 

 removed, progressing in concentric rings. In such specimens, the fresh 

 greenish material is found at the center passing gradually into the buff- 

 colored material toward the periphery. 



The low cliffs which border Chesapeake Bay south of the pier at 

 Fairhaven are composed of diatomaceous earth with a capping of 

 Columbia gravel. From Fairhaven the beds cross southern Maryland 

 in a northeast-southwest direction following the line of strike, and 

 are worked at Lyons Creek on the Patuxent and again at Popes Creek 

 on the Potomac. They may also be found at innumerable places be- 

 tween these points in cuttings made by water-ways. North of this 

 diagonal line, extending between Fairhaven and Popes Creek, the diato- 

 maceous beds gradually rise until they rest on the hilltops, while south 

 of the diagonal line, they gradually disappear below tide. 



The Fairhaven diatomaceous earth has been subdivided into three 

 zones, which may be characterized as follows : 



Zone 1. — At the base of the Calvert formation and lying unconform- 

 ably on the Eocene deposits is a bed of brownish sand carrying Fhacoides 

 (Lucinoma) contraciiis. This stratum varies somewhat in thickness 

 from place to place, but does not depart widely from six feet on the 

 average. 



Zone 2. — Lying immediately above Zone 1 is a thin stratum of white 

 sand of about one foot in thickness, -v^-hich is locally indurated to form 

 sandstone. It contains a large number of fossils, of which the follow- 



