98 THE GEOLOGY OF rKINCE GEOKGE's COU^^TY 



others, particularly where the upper beds are exposed, the arenaceous 

 phase is predominant and the beds may consist entirely of sands vary- 

 ing in color from white to dark-greenish black. Where the glau- 

 conite decomposes, the iron oxidizes and the materials are stained 

 reddish brown, and may even become firmly indurated by the iron 

 oxide. Iron pyrite is also a common constituent and in places a 

 small layer of gravel lies at the base of the formation. Although the 

 Matawan contains varied materials it is much less variable than 

 formations of the Potomac group or the Magothy formation, and 

 throughout its extent in Maryland can generally be readily recogiiized 

 by the prevailing dark-colored micaceous glauconitic sand of which 

 it is chiefly composed. 



Paleontologic Character. — Although the Matawan formation as a 

 whole can not be regarded as extremely fossiliferous, yet it contains 

 bands in which organic remains are present in great abun- 

 dance. Such a band occurs in the cutting where the Chesapeake 

 Beach Railway crosses Central avenue just east of the District line. 

 In jSTew Jersey as well as in Maryland the formation has yielded a 

 varied fauna of foraminifers, pelecypods, gastropods, scaphopods, 

 and ammonites.^ 



Strike, Dip, and Thichness. — The formation strikes from north- 

 east to southwest and dips southeastward at about 25 feet to the mile. 

 The maximum thickness of the Matawan occurs in the Patuxent 

 River valley and is about 40 feet. From this region the formation 

 gradually thins toward the southwest until it is not more tlian 30 

 feet thick in the exposures along Tlenson Creek and about 20 feet 

 thick in the Port Washington hill. Like many other Coastal Plain 

 formations, the beds thicken as they dip beneath later deposits, but 

 the records of wells Avhich have penetrated these formations in the 

 eastern part of the county are too general to permit the determina- 

 tion of the amount of thickening. 



Stratigraphic Relations. — In places a marked unconformity separ- 

 ates the Matawan from the underlying Magothy formation, but it is 

 conformably overlain by the Monmouth. The separation between 

 iClark, Bull. Geol. Soc. America, vol. VIII, 1897, pp. 330-331. 



