32 The Lower Ceetaceous Deposits of Maryland 



Pliocene (f) 



The supposed Pliocene is represented by the Lafayette formation 

 which has been considered as extending from the Gulf along the Atlantic 

 border region as far northward as Pennsylvania, where the last remnants 

 are found. The Lafayette formation is chiefly developed as a terrace 

 lying irregularly and unconf ormably on whatever older formation chances 

 to be beneath it whether along the margin of the Piedmont Plateau or 

 the Coastal Plain. 



Few fossils have been found in the Lafayette, and those not sufficiently 

 distinctive to determine its age. We simply know that it is younger 

 than the latest Miocene on which it rests and older than the oldest 

 Pleistocene beds found in its immediate vicinit}^ It may be either Ter- 

 tiary or early Quaternary in age, although most authors hitherto have 

 regarded it as probably Pliocene in age. Doubtless materials of very 

 different ages have been referred by various students to the Lafayette. 

 The type section in Lafayette County, Mississippi, has recently been 

 shown to be of Eocene age.^ 



The materials comprising the Lafayette formation consist of clay, 

 loam, sand, and gravel which are often highly ferruginous, the iron being 

 often present in the deposits in sufficient amount to act as a cement. 

 These materials are generally very imperfectly sorted. The deposits 

 rarely exceed 50 feet in thickness, while the southeasterly dip is only a 

 few feet in the mile. 



QUATEEFARY 



Pleistoce7ie 



The Pleistocene deposits consist of a series of surficial materials 

 Enown under the name of the Columbia Group, which has been divided 

 in Maryland and adjacent States into the Sunderland, Wicomico, and 

 Talbot formations. They consist mainly of a series of terraces which 

 wrap about the Lafayette and the lower portions of the older formations, 

 and hence extend as fluviatile deposits up the stream courses. 



^ Berry, Journ. Geol., vol. xix, 1911, pp. 249-256. 



