96 THE PLIOCENE AND PLEISTOCENE DEPOSITS OF MARYLAND 



of the bay. In Southern Maryland is partakes of the character assumed 

 by the Wicomico in that it forms a border around the margins of the 

 other formations and extends up their reentrant valleys, filling them in 

 as a valley floor. 



Structure and Thickness. — What was said in regard to the struc- 

 ture of the previous formation applies equally well to the Talbot, with the 

 exception that .the Talbot has apparently suffered to a very small extent 

 by tilting. It has been raised practically parallel to its former position. 

 Comparisons made between ten localities within the Talbot formation 

 (Plate XXVI) show that there is no slope in the northeast-southwest 

 direction, but a very gentle one toward the southeast. The difference in 

 altitude between Perryville and Crisfield is only 40 feet over a distance 

 of 109 miles, making an average slope of 0.4 of a foot per mile. It will 

 thus be seen that the Talbot formation, like its predecessors, slopes toward 

 the southeast. There is probably little if any element of tilting repre- 

 sented in this structure. 



The thickness of the Talbot is as variable as that of the other surficial 

 deposits. Where the waves of Chesapeake Bay have cut well back into 

 this formation so as to dissect it near its contact with the Wicomico 

 scarp-line, it at times has a thickness of 35 or 40 feet. Usually it is 

 much less and may thin out and disappear altogether. As a whole, the 

 average thickness of the Talbot formation does not exceed 20 or 25 feet. 



Character of Materials. — The materials which compose the Talbot 

 formation consist of clay, peat, sand, gravel, and ice-borne boulders 

 (Plates XIV, XVI, Fig. 1, XVII, and XVIII). As in the Sunderland 

 and Wicomico formations, these materials grade into each other both 

 vertically and horizontally, and the same tendency toward a bipartite 

 division of the coarser materials below and the finer materials above is 

 present in the Talbot as in the others. There is, on the whole, much less 

 decayed material than in the three preceding formations and the absence 

 of this gives to the formation a younger appearance. Cross-bedding is 

 very common. In the western portion of the area, throughout the Poto- 

 mac and Susquehanna valleys, the Talbot deposits frequently contain 

 large ice-borne boulders. These are also common on the surface and 

 within the body of the same formation on the Eastern Shore. 



