CAMBRO-ORDOVICIAN LIMESTONES 711 



Platy granocrystalline limestone, fossiliferous 25 



Dark, subcrystalline limestone with wavy partings of shale, fossiliferous . . 150 

 Very thin-bedded pure fine-grained drab limestone followed by more massive 

 pure beds with magnesian layers and fine laminations (Stones River) 



Total 325 



The following section was measured ij miles west of Markes on 

 the west side of the Mercersburg belt: 



Feet 



Fissile and calcareous shale (Martinsburg) 



Thick bed of coarse crystalline gray limestone, fossiliferous 5 



Thin bedded and cobbly dark limestone with Nidulites and Monotrypa 



hemisphericus'm.\r^Y>^YTpaxt 45 



More massive limestone, banded in part 45 



Pure fine-grained dark limestone with large Beatricea 20 



Dark compact limestone 20 



Covered 60 + 



Thin-bedded pure fine even-grained drab hmestone (Stones River) 150 



Total 195 + 



In the McConnellsburg Cove, few outcrops of the Chambersburg 

 limestone occur, and but one measured section was secured, 2 miles 

 northeast of McConnellsburg, as follows: 



Feet 



Fissile shale containing graptolites 



Hard black slate and thin slaty black limestone, (Martinsburg) .... 84 



Covered 10 



Gray marble and massive blue-veined limestone 20 



Dark shaly limestone with argillaceous partings, containing solenopora and 



bryozoa 68 



Pure fine even-grained limestone (Stones River) 



Total 182 



The Chambersburg formation forms a narrow band along the 

 margin of the overlying Martinsburg shale throughout the Mercers- 

 burg and Chambersburg quadrangles except where it is cut out by 

 faults. It is present also along this contact throughout the Carlisle 

 quadrangle, but details of its character and thickness there are not 

 known. 



Nearly everywhere this formation yields on careful search an 

 abundance and great variety of fossils, and those from the Chambers- 

 burg quadrangle differ from those obtained in the Mercersburg quad- 



