610 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



The Matawan consists chiefly of dark-colored clays, in places micaceous and glauconitic, 

 in its lower part, and of sands, with an interbedded clayey member, locally highly glauconitic, 

 in its upper part. It attains a total thickness of about 275 feet, although a thickness of 400 

 feet has been found in deep well borings east of its outcrop. It lies unconformably on the 

 Magothy. The Matawan group contains an extensive fauna with subordinate faunules. It 

 has been traced throughout the north Atlantic Coastal Plain and thence southward to the Gulf. 



The Monmouth group consists of sands and clays, with an interbedded glauconitic division 

 in the northern part of the area. Toward the south the upper sandy formation disappears. 

 The greatest thickness of the group is about 150 feet. The Monmouth is conformable to the 

 Matawan. It has an extensive fauna marked by the introduction of Belemmtella americana 

 and other forms, representing a later fauna than the Magothy and Matawan fauna hitherto 

 described. This fauna also has been traced southward through the north Atlantic Coastal 

 Plain into the Gulf region. 



The Rancocas consists largely of greensand marls and sandy calcareous beds which have 

 a maximum thickness in southern New Jersey of about 125 feet. It is conformable to the 

 Monmouth and is characterized by a fauna quite distinct from the preceding, including GrypJisea 

 vesicularis, Terehratula Jiarlani, and other forms. 



The Manasquan formation consists of greensand marls and attains a thickness of about 50 

 feet. It is conformable to the Rancocas. It contains a marine fauna which has some forms in 

 common with the Rancocas and others that are quite distinct. 



Maryland and Delaware. — The deposits in Maryland and Delaware contain representatives 

 of both the Lower and the Upper Cretaceous. The Lower Cretaceous also continues northward 

 into Pennsylvania, where a few isolated outliers are found, and the basal formation of the 

 Upper Cretaceous occurs as a narrow strip along the eastern border of that State. In Maryland 

 and Delaware both divisions are extensively developed, the Lower Cretaceous attaining its 

 maximum development in Maryland. 



The Maryland area has been long.studied and is discussed in an extensive literature. Among 

 those who have been most actively engaged in the study of this region may be mentioned 

 McGee,^"^ Clark,"'' i"' i^° Bibbins,"'- "» Mathews,'^'' Berry, and MiUer.s"" 



The following scheme of classification has been adopted for the Maryland-Delaware region: 



Upper Cretaceous: 



Eancocas formation. 



Momnoutli formation. 



Matawan formation. 



Magothy formation. 



Raritan formation. 

 Lower Cretaceous (Potomac group): 



Patapsco formation. 



Arundel formation. 



Patuxent formation. 



The Patuxent formation consists mainly of sand, generally arkosic and in many places 

 cross-bedded, with small masses of clay scattered through it. The formation attains a thickness 

 of 350 feet. It has a well-defined early Cretaceous flora. 



The Arundel formation consists chiefly of clays, which in places carry iron ore and are 

 commonly lignitic. It has a thickness of about 125 feet. It is unconformable to the Patux- 

 ent. It has an extensive flora similar to that of the Patuxent and a fauna consisting chiefly of 

 dinosaurian remains. 



The Patapsco formation consists of highly colored and variegated clays and Hghter-colored 

 sandy clays and sands. It has a thickness of 200 feet and contains an extensive flora of "Meso- 

 Cretaceous " types in which angiosperms constitute a considerable element. It is unconformable 

 to the Arundel. 



The Raritan formation consists chiefly' of thick-bedded hght-colored sands, with light- 

 colored clays in the lower portion. The deposits have a thickness of about 400 feet. The 

 Raritan overlies the Patapsco unconformably. It carries a distinctly Upper Cretaceous flora 

 containing numerous dicotyledons. 



