224 CLARK AND MARTIN — THE COAL MEASURES OF MARYLAND 



stone, as the case may be, forming one continuous mass with the Lower 

 Mahoning sandstone, is the Upper Mahoning sandstone. This sandstone 

 varies much in lithologic character and thickness. Sometimes it is very 

 massive and conglomeritic, while at other times it is thin-bedded and 

 shaly. 



Masontown coal (30). — A seam of coal having a thickness of from 18 to 

 24 inches, and without partings, is found in a position varying from 85 

 to 125 feet above the base of the formation. From its position above 

 the Mahoning sandstone, and more especially from its relation to the 

 overlying fossiliferous beds, this is regarded as the equivalent of the 

 Masontown coal of Pennsylvania. 



Lower Cambridge limestone (31). — Separated from the Masontown coal 

 by about 5 feet of fissile, black carbonaceous shale is a band of calcareous 

 shale or bituminous limestone, usually about 8 inches in thickness. This 

 limestone and the overlying shales are filled with well preserved marine 

 fossils. The fauna is very rich, both in individuals and in species. No 

 detailed study has as yet been made of it, but enough species have been, 

 determined to make it certain that it is the fauna of the Tower Cambridge 

 limestone of Ohio and Pennsylvania. The greatest thickness of this 

 limestone known in Maryland was obtained in the bore-hole at Jennings 

 mill. Here it is 3 feet thick, and is overlaid by 4 feet of black, fossiliferous 

 shale. 



Buffalo sandstone (32). — A short distance above the Lower Cambridge 

 limestone is a sandstone, which sometimes attains a thickness of 40 feet. 

 It corresponds with the Buffalo sandstone of western Pennsylvania, 

 which was formerly considered to be the equivalent of the Upper Ma- 

 honing sandstone, but which I. C. White has shown to overlie the Lower 

 Cambridge limestone. 



Upper Cambridge limestone (33). — In the river bluff north of Friends- 

 ville there are two thin limestone beds at intervals of 32 and 50 feet 

 respectively above the Lower Cambridge limestone. One or both of 

 these probably represent the Upper Cambridge limestone of Ohio. Both 

 beds carry marine fossils. 



Lower red shales. — The interval between the top of the Buffalo sand- 

 stone and the under clay of the Bakerstown coal contains a large amount 

 of red and green shale. The Upper Cambridge limestones occur in these 

 shales, and the red shales themselves carry fossils. These red beds are 

 very persistent, and their outcrop can be easily traced throughout the 

 Lower Youghiogheny basin. They were encountered at their normal 

 position in the bore-hole at Jennings mill, in the Castleman basin, and 

 are evidently the beds known by that name in Pennsylvania. 



