152 THE CAMBRIAN AND ORDOVICIAN DEPOSITS OF 'MARYLAND 



Chambersburg limestone. 



Christiania bed. Feet 



Calcareous shales and shaly limestone with traces of Christiania. 10 

 Nidulites bed. 



Massive dark blue to dark gray limestone with abundant Nidu- 

 lites 270 



Echinospherites bed. 



Thin bedded subgranular limestone weathering cobbly and hold- 

 ing Echinospherites 30 



Stones River limestone. 



Pure dove limestone with Leperditia fabulites and Tetradium 



syringoporoides 



Essentially the same section is exposed at Martinsburg, West Virginia, 

 where the southern continuation of the same line of outcrops affords the 

 following sequence : 



Section of Chambersburg Limestone at Martinsburg, West Virginia 



Martinsburg shale. Feet 



Black fissile ehale 



Argillaceous shaly limestone 125 



Chambersburg limestone. 

 Christiania bed. 



Thin bedded dark gray limestone with Christiania trentonensis . . 20 

 Nidulites bed. 



Dark gray massive and thin bedded limestone weathering light 



gray cobbly, holding Nidulites 300 



Echinospherites bed. 



Dark shaly and subgranular limestone with Echinospherites 20 



Stones River limestone. 



Pure dove limestone 



Variations in Distribution. The distribution of the various members 

 of the Chambersburg limestone in the eastern and western parts of the 

 Appalachian Valley in southern Pennsylvania is expressed in the following 

 table : 



General Sequence of Beds in Chambersburg Limestone 



West of Martinsburg shale belt East of Martinsburg shale belt 



Greencastle bed. 



Christiania bed. 



Nidulites bed Nidulites bed. 



Echinospherites bed Echinospherites be,d. 



Tetradium cellulosum bed Tetradium cellulosum bed. 



Caryocystites bed 



