32 The Uppei; Cretaceous Deposits of Maryland 



Pliocene (?) 



The supposed Pliocene is represented by the Brandywine formation 

 which, under the name of Lafayette, has been considered as extending 

 from the Gulf along the Atlantic border region as far northward as 

 Pennsylvania, where the last remnants are found; but recently the Gulf 

 Lafayette has been shown to be made up of the weathered surface mate- 

 rials of many different formations. It is chiefly developed as a terrace 

 lying irregularly and unconformable on whatever older formation chances 

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

 the Coastal Plain. 



Pew fossils have been found, and those not sufficiently distinctive to 

 determine its age. It is known to be younger than the latest Miocene 

 on which it rests and older than the oldest beds hitherto regarded as Pleis- 

 tocene found in its immediate vicinity. It may be either Tertiary or 

 early Quaternary in age. although most authors hitherto have regarded 

 it as probably Pliocene in age. 



The materials comprising the Brandywine 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, and have a southeasterly dip of only a 

 few feet in the mile. 



QUATERNARY 



Pleistocene 



The Pleistocene deposits consist of a series of surflcial materials 

 known 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. 



Fossils have been found particularly in the latest, or Talbot forma- 

 tion, where extensive shell beds of estuarine and marine origin are 

 known. Fossil plants have been found in all the formations. Their 



