Ixxvi GEOLOGICAL AND PALEONTOLOGICAL RELATIONS 



a distance of about 2^ miles south of Chesapeake Beach it has a thick- 

 ness of only 2 feet and 6 inches. At this point the base actually lies 

 higher than at Chesapeake Beach, although on account of the thinning 

 the top lies lower. From this point southward it dips away in har- 

 mony with the dip of the other beds of the Calvert formation. The 

 materials making up this zone consist of a greenish sand clay, which 

 carries scattered bands of Corhula elevata. 



Zon-e G. — This zone consists of a greenish sandy clay carrying large 

 numbers of Corhula elevata which are distributed thickly throughout 

 the stratum and not separated into scattered bands as in the zones im- 

 mediately below^ and above 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 ones, 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 carrying scattered bands of Corhula elevata, resembling 

 very much in appearance Zone 5. 



Zone 8. — -This stratum is lithologically like those 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 varying 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 conists of a grayish green or a .yellow to a brown sandy clay 

 varying in thickness from 6 to 9 feet and is continuously exposed 

 along the Calvert ^Cliffs 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: Turrltella indentata, 

 Pliacoides anodonta, CrassateUites melinus, Astarte cuneiformis, Ostrea 



