MARYLAND GEOLOGICAL SURVEY 77 



numbers of Corhula elevata whicli are distributed thickly througliout 

 the stratum and not separated in scattered bands as in the zones ini- 

 mediateh' below iiiid a1)0ve it. At Chesapeake Beach, where this zone 

 is best developed, it attains a thickness of eight feet, but thins rapidly 

 toward the south, like the two preceding zones, until at a point 2^ miles 

 south of Chesapeake Beach it has diminished to a thickness of two 

 feet. From this place it continues at about the same thickness until 

 it finally disappears beneath the beach at Plum Point. 



Zone 7. — Lying immediately above the last is a layer of greenish 

 sandy clay, resembling very much in appearance Zone 5, and carrying 

 scattered bands of Corhula elevata. 



Zone 8. — This stratum is lithologically like tliose immediately pre- 

 ceding, but varies from them in either being devoid of fossils or in 

 carrying only a few poorly preserved fossil casts of a Corhula, which is 

 probably Corhula elevata. It consists of a greenish sandy clay varying 

 from 9 to 15 feet in thickness. It may be best seen along the Calvert 

 Cliffs from Chesapeake Beach to Plum Point. 



Zone 9. — This zone consists of greenish and greenish blue sandy clay 

 carrying scattered layers of Corhula elevata and varjdng in thickness 

 from 6 feet at Chesapeake Beach to 2 feet at Plum Point. 



Zone 10. — On account of its great and varied assemblage of fossils 

 this stratum is the most conspicuous zone in the entire Calvert forma- 

 tion. It consists of a grayish green or a yellow to brown sandy clay 

 varying in thickness fiom 6 to 9 feet, and is continuously exposed 

 along the Calvert ClifTs from Chesapeake Beach till it dips below tide 

 two or three miles south of Plum Point Wharf. The following is a 

 partial list of the fossils found in this zone: Turritella indentata, Pha- 

 coides anodonta, Crassaiellites melinus, Astarte cuneiformis, Ostrea 

 sellaeformis, Pecten madisonius, Macrocallista marylandica, Atrina Jiar- 

 risii, Area suhrosirata, Glycymeris parilis, etc. It corresponds to " Zone 

 b " of Harris.' 



Zone 11. — This stratum consists of a greenish blue to a brown sandy 

 clay changing locally to a sand. It thickens somewliat as it passes 



* Loc. cit. 



