LOWER CRETACEOUS. 611 



The Magothy formation consists of alternating sands and clays, the latter in places hgnitic. 

 The maximum thickness of the formation is about 100 feet. The Magothy is unconformable 

 to the Raritan. It contains an extensive flora of types more recent than those of the preceding 

 formation. 



The Matawan formation consists mainly of dark-colored micaceous sandy clays, the average 

 thickness of the formation being about 60 feet. It carries an extensive marine fauna. 



The Monmouth formation consists mainly of sands, more glauconitic in the upper part 

 than in the lower. The deposits have a maximum thickness of about 100 feet on the eastern 

 shore of Chesapeake Bay and gradually decrease in thickness until they thin out in the Potomac 

 VaUey. A fauna marked by the advent of Belemnitella americana and other forms is found 

 in this formation. 



The Rancocas formation consists chiefly of greensand marls, which are in many localities 

 highly calcareous. The formation has a thickness of about 20 feet in central Delaware but 

 graduaUy thins out toward the Maryland line. 



Virginia. — ^The Cretaceous deposits which outcrop at the surface ia Virginia are aU Lower 

 Cretaceous, although strata belonging without much doubt to the Upper Cretaceous have been 

 penetrated in deep well borings to the east and have yielded a few fossils that indicate the 

 presence of the Raritan, Magothy, and Matawan formations. The Lower Cretaceous deposits 

 are Hmited to the Patuxent and the Patapsco, the Arundel formation not being recognized 

 in Virgioia. 



Much study has been given to the Virginia area, the more important contributions having 

 been made by Rogers,""" Ward,*"' *"'' Fontaine,^*^ Clark and MiUer,'" and Berry." 



The Patuxent formation is exposed in the principal drainage channels and consists chiefly 

 of sands, cross-bedded, highly arkosic, and locaUy indurated, with clay beds in places Hgnitic 

 and commonly chloritic. The thickness of the formation reaches about 300 feet. The Patux- 

 ent contains a large flora which is probably the most extensive known flora from the Lower 

 Cretaceous. 



The Patapsco formation consists of highly colored and variegated clays, in places hgnitic, 

 and sand beds, cross-bedded and locally indurated. The formation is Hmited to the northern 

 part of the area, where it attains a thickness of about 150 feet and has an extensive flora of 

 later types than those found in the Patuxent. 



North OarolirM. — ^The Cretaceous deposits of North Carolina belong in part to the Lower 

 and in part to the Upper Cretaceous. In the northern part of the State the strata are confined 

 largely to the main river channels, but south of the Hatteras axis they spread out and occupj 

 a wide area. 



The North Carolina deposits have not received as much attention until recently as the 

 Cretaceous deposits farther north. Among those who have studied the region are Clark,"* 

 Stephenson,'"* and Berry. '^' '*■ "^' " The two latter have spent much time in recent years in a 

 detailed field investigation, Stephenson giving his attention chiefly to the stratigraphy and marine 

 invertebrate fossils and Berry to the fossil plants. Clark, who earher studied the region, has 

 devoted his attention to the interpretation of the deposits and faunas and their correlation 

 with other areas. 



The following scheme of classification has been accepted for the North CaroHna area : 



Upper Cretaceous: 



Peedee sand. 



Black Creek formation. 

 Lower Cretaceous: 



Patuxent formation. 



The Patuxent formation consists chiefly of sands and clays, the former locally cross-bedded 

 and arkosic. Its thickness is about 300 feet. No flora or fauna has been found in it. 



The Black Creek formation consists of Hght-colored sands and interbedded clays, the latter 

 in places Hgnitic and generaUy thinly laminated. The thickness of the formation reaches about 

 700 feet. The Black Creek overhes the Patuxent formation unconformably. An extensive 

 flora is found in it, the beds carrying the plant remains being interbedded with strata containing 



