Maryland Geological Survey 29 



The total average thickness of the Lower Cretaceous formations in 

 Maryland is between 600 feet and 700 feet, and they show an average 

 dip of about 40 feet in the mile to the southeast. 



Upper Cretaceous 



The deposits referred to the Upper Cretaceous comprise the Earitan, 

 Magothy, Matawan, Monmouth, and Eancocas formations. The two 

 lower formations are chiefly estuarine and fluviatile in origin, while the 

 overlying formations are distinctly marine. All of these formations can 

 be traced to the northward into Delaware and New Jersey, where they 

 attain an even larger development than in Maryland. To the southward 

 they are gradually overlapjjed, one after the other, by the Tertiary forma- 

 tions and are unknown in Virginia. Similar deposits are found in North 

 Carolina and the States which lie to the south of it, but are known under 

 other formational names, although probably continuous beneath the cover 

 of Tertiary deposits. 



The Upper Cretaceous formations form an apparently unconformable 

 series resting unconformably upon the Patapsco formation of the Lower 

 Cretaceous. The deposits consist chiefly of sands and clays, with some 

 gravels in the two lower formations, while the three higher formations 

 consist more particularly of clays and sands, the latter often somewhat 

 glauconitic, although much less so than similar deposits in New Jersey. 

 The Earitan formation consists chiefly of thick-bedded and light-colored 

 sands with some gravels. Clays generally light in color occur in the lower 

 portion of the formation. The Magothy formation is made up of sands 

 and clays that change rapidly both horizontally and vertically. Finely 

 laminated clays with alternating sand layers and often more or less 

 carbonaceous likewise occur. The Matawan formation is composed of 

 micaceous, sandy clays somewhat more sandy in the upper portion and 

 more argillaceous in the lower portion of the formation. The Monmouth 

 formation consists of reddish and pinkish sands more or less glauconitic 

 in character. The Eancocas formation, which outcrops in Delaware 

 near the Maryland line, consists of greensand marls which are frequently 

 highly calcareous. 

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