i 



118 THE GEOLOGY OF PRi:S'CE GEO'KGe's COUNTY 



ing from an erosion interval, the whole mantle of Pleistocene mate- 

 rials occurring at any one locality is referred to the same formation. 

 The Sunderland is described as overlying the Cretaceous, and 

 Tertiary deposits and as extending from the base of the La- 

 fayette-Sunderland escarpment to the base of the Sunderland- 

 Wicomico escarpment. The few deposits of Lafayette materials 

 which may possibly underlie the Sunderland are disregarded because 

 they are unrecognizable. Similarly the Wicomico is described as 

 including all the gravels, sands, and clays overlying the pre-Laf ayette 

 deposits and extending from the base of the Sunderland-Wicomico 

 escarpment to the base of the Wicomico-Talbot escarpment. Per- 

 haps, how^ever, materials of Lafayette and of Sunderland age may 

 underlie the Wicomico in places. In like manner the Talbot may 

 here and there rest upon deposits of the Lafayette, Sunderland, and 

 Wicomico. 



Tlie Sunderland Formation. 



This formation has been named from the little village of Sunder- 

 land, Calvert County, near which it is typically developed. The 

 name was first applied to the formation by G. B. Shattuck in May, 

 1901.^ The Sunderland corresponds approximately with the Earlier 

 Columbia of McGee and with parts of the Bridgeton and Pensauken 

 of Salisbury. Its Pleistocene age is indicated by the modern appear- 

 ance of its plant remains and by its relation to the next younger 

 formation, the Wicomico, in which boulders bearing glacial stride 

 have been found. 



Areal Distribution. — The Sunderland formation is developed as a 

 terrace or plain which occupies the tops of the secondary stream 

 divides below the Lafayette formation, between the Patuxent and 

 Potomac rivers. Since its deposition it has suffered more erosion 

 than either of the two younger formations, but enough of it still 

 remains within the area to make its mapping possible and to establish 

 its relations to the other deposits. The surface of the Sunderland 

 plain varies in altitude from 200 feet in the northern and central 

 ijohns Hopkins Univ. Circ. No. 152. 



