MARYLAND GEOLOGICAL SURVEY 93 



Eocene. Near the contact of the Miocene and Eocene, a rolled fauna 

 derived from the latter is reworked in the former and occasionally 

 grains of glauconite, which were in all probability formed in the Eocene 

 occur in the lower portions of the Miocene. 



The organic remains, which consist, for the most part, of shells of 

 mollusks and bones of vertebrates, are usually in a ver\' good state of 

 preservation. They have been but slightly disturbed since deposited 

 and evidently now occupy the same relative positions which they did at 

 the time when they lived. 



The Pleistocene. 



The Columbia Group. 



The Columbia Group is the name applied to a series of beds of clay, 

 loam, sand, gravel, and ice-borne boulders, which are stratigraphically 



Fig. 1. — Diagram showing ideal arrangement of the various terrace forma- 

 tions in the Maryland Coastal Plain. 



younger and lie topographically below the Lafayette formation. They are 

 widely distributed over the surface of the Coastal Plain from Atlantic 

 Highlands southward to Mexico and are Pleistocene in age, being the last 

 formations which have been laid down in the region before the Recent 

 deposits were formed. The formations which constitute the Columbia 

 Group are, beginning with the oldest, the Sunderland, Wicomico, and 

 Talbot. These deposits were laid down for the most part during the 

 glacial period, but a definite correlation of them with the glacial deposits 

 of New Jersey and other regions is not practicable in the present state 

 of knowledge. When the field relations which exist between these two 

 great classes of deposits are more accurately known, a correlation will, 

 no doubt, be possible. The various formations of the Columbia Group 



