MARYLAND GEOLOGICAL SURVEY 59 



The Upper Cretaceous beds lie unconformably on the deposits of the 

 Potomac group and consist of sand, greensand, marl, and clay. They 

 extend in a broad belt from Atlantic Highlands, New Jersey, to the 

 Potomac river in Maryland. These beds are more extensively developed 

 throughout the northern portion of the area than in Maryland. In this 

 region, not only are the beds thinner and. of less areal extent than farther 

 north, but they also consist of fewer formations than in New Jersey. 

 Only the two basal formations, the Matawan and Monmouth, are present, 

 the Eancocas formation terminating near the Delaware border, except 

 for a doubtful locality on the Severn Eiver in Anne Arundel county. 



EOCENE. 



Above the Cretaceous deposits and lying unconformably on them occur 

 two formations belonging to the Eocene. These are known as the 

 Aquia and Nanjemoy. They consist of sand, greensand, marl, and clay 

 and are part of a more extensive belt which extends from Delaware south- 

 ward through Virginia, whiie an older deposit of the Eocene occurs in 

 the vicinity of Shark river, New Jersey. Throughout the northern por- 

 tion of this distribution, they are covered to a great extent by younger 

 formations, but farther south in Maryland, particularly in the region 

 between Washington and Annapolis, this covering has been removed, 

 leaving the Eocene beds exposed on the surface. 



MIOCENE. 



Above the Eocene deposits and unconformably resting on them occur 

 the formations which have been assigned to the Miocene. They are three 

 in number and have been named the Calvert, Choptank, and St. Mary's. 

 These consist of sand, marl, and clay, and together represent the Chesa- 

 peake group in this State. The Miocene deposits of this region form part 

 of a more extensive series, extending from Massachusetts to Mexico. It 

 is not known whether the Miocene beds ever extended across this area in 

 an unbroken belt, but it is certain that erosion has destroyed much of 

 their former continuity and that they are now found in disconnected 

 areas. 



