JV. H. Darton — Magothy Formation of Maryland. 419 



the Severn River at Round Bay, but they have not been 

 studied. 



The formation is not divisible into individual members, for 

 the variations in character which it presents are local features 

 not characterizing definite horizons. 



Synonomy. — The Magothy formation has never before been 

 discriminated or at least with any degree of definiteness. Mr. 

 P. R. Uhler in his several papers* has referred more or less 

 definitely to some of its features at several localities but he 

 does not set forth its true relations.. He has separated a mem- 

 ber, which he terms " alternate sand series " beginning some- 

 where at this horizon and extending up into the Severn forma- 

 tion, but its definition is so vague and moreover so variable in 

 each succeeding publication of his that the name cannot be 

 adopted without confusion. 



Economic geology. — The Magothy formation has not as yet 

 yielded any great amount of economic products. Its sandstone 

 members have been employed locally to some extent as build- 

 ing stone and its gravels are used for railroad ballast. Some 

 portions of its sands are, I believe, sufficiently pure for use in 

 the arts notably on the Magothy River and at several points on 

 the bay shore south of Howell's Point. 



History. — The Magothy formation is a product of littoral 

 deposition following the uplift and erosion of the Potomac 

 deposits. It represents a time when currents and beach action 

 were sufficiently active to sort out moderately coarse sands and 

 spread them in beds, regular where the currents were gentle, 

 and crossed where currents were more powerful. A few thin 

 lenses of clay indicate that slack waters existed locally and the 

 gravels westward indicate proximity to a shore line. The 

 materials were probably all derived from the Potomac forma- 

 tion and the shore line was located within the Potomac area 

 throughout. The far eastward extension of the Magothy beds 

 now deeply buried below the Severn deposits, undoubtedly 

 consists of the finer sands and clays which were carried farther 

 off shore before being deposited. 



Magothy deposition was succeeded by a general uplift and 

 erosion interval during which the surface of the Magothy 

 deposit was planed off in greater or less measure and degrada- 

 tion of the Potomac surface westward was continued. This 

 epoch was followed by Severn deposition. 



* Maryland Acad. Sci. Trans., vol. i. 1888-1892. 



