94 THE CAMBRIAN AND ORDOVICIAN DEPOSITS or MARYLAND 



While the general section given above holds fairly well for all parts 

 of the Valley, the detailed stratigraphy of the formation in the eastern 

 and western parts is, as mentioned above, somewhat different. The best 

 exposure of the Beekmantown limestone east of the Martinsburg shale 

 belt is adjoining the Chambersburg-Gettysburg Pike one mile east of 

 Chambersburg, Pennsylvania. This section, measured by Ulrich and 

 Stose, is given below with slight emendations to show the position of the 

 fossil zones. 



Section of Beekmantown Limestone One Mile East of Chambersburg, 



Pennsylvania 



Feet 



Base of Stones River, containing fine limestone conglomerate and laminar 



and oolitic chert 



Interbedded fine-grained pure and magnesian limestones, finely laminated 

 in part and containing small quartz geodes; porous sandy chert near 

 top; dark-blue layers near base containing numerous gastropods 

 (Turritoma fauna) and ostracods and mottled by magnesian material 

 that weathers out, leaving pits and holes 600 



Alternating pure dove-colored and gray limestone and magnesian lime- 

 stone, with layer of sandy chert 375 



Bluish to dove-colored fine-grained fossiliferous limestone, at the base 



containing rounded quartz grains. Ceratopea fauna at top 100 



Pink fine-grained marble, containing layers of milky quartz chert; 

 gastropods' of the genera Ophileta, Maclurites and Eccyliopterus 

 rather abundant 275 



Pure dove-colored and blue fine-grained limestone, with some pink lime- 

 stones; contains fragments of trilobites 285 



Fine-grained dove-colored to dark gray limestone with fine conglomerate 

 and oolite beds; abundant chert in upper portion, in part oolitic and 

 conglomeratic. Cryptozoon steeli in middle part 145 



Stonehenge limestone member: .' 



Fine-grained light to dark gray limestone containing wavy laminae 

 of sandy matter that stand in relief or fall to sandy shale on 

 weathering and thick beds of " edgewise " conglomerate; gastro- 

 pods in upper and fine fragments of trilobites in lower portion. . 225 

 Dark to very light gray massive limestone, containing Dalmanella, 



Ophileta and trilobite fragments 260 



Top of Conococheague, containing wavy and sandy laminae and beds of 



coarse limestone conglomerate 



2265 



"West of the shale belt, the details of the Beekmantown section are 

 somewhat different, although the several fossil zones can be readily 



