94 THE GEOLOGY OE PRINCE GEOKGE^S COUNTY 



field, however, have shown that the Magothy should be regarded as 

 a distinct formation, on both stratigraphic and paleontologic grounds, 

 and these transitional beds from N^ew Jersey southward have been 

 referred by Clark- to the ]\[agothy formation as defined by Darton 

 for the Maryland area. 



Areal Distribution.— The Magothy formation outcrops in discon- 

 tinuous areas in Prince George's County, extending from the Patux- 

 ent River valley in the vicinity of Priest Bridge southwestward to 

 the Potomac River valley just beyond Congress Heights. It does 

 not outcrop in a continuous belt because of an overlap of the Mata- 

 wan, which is in some places sufficient to bring that formation in 

 immediate contact with the Raritan, An occurrence of this kind 

 can be seen about three-fourths of a mile west of Brightseat. The 

 best exposures lie from half a mile to 3 miles west of Priest Bridge 

 and along the west slope of Good Hope Hill from St. Elizabeth's 

 to the junction of Benning and Bowen roads on the District line. 



Character of Materials. — The Magothy formation is composed of 

 extremely varied materials and may change abruptly in character 

 both horizontally and vertically. Loose sands of light color are the 

 most prominent constituents. These sands usually show fine lamina- 

 tions and locally considerable cross-bedding. The sand consists of 

 coarse, rounded to subangular quartz grains which range in color 

 from pure white to a dark ferruginous brown. At many places 

 lenses or bands of brown sand occur within the lighter colored sands. 

 Normally the deposits of sand are loose, yet locally the iron derived 

 from this and adjacent formations has firmly cemented the grains 

 together to form an indurated iron sandstone or conglomerate. A 

 thin ledge of such a sandstone near the Catholic Church west of 

 Priest Bridge forms a small waterfall in a tributary of Patuxent 

 River. Just below Overlook Inn, on East Washington Heights, 

 there is a ledge of massive brown sandstone of this character. 



The argillaceous character of the Magothy is very prominent in 

 some localities, although it is usually subsidiary to the arenaceous 

 phase. The clay commonly occurs as fine laminae alternating with 

 -Clark, Anier. Jour. Sci., 4th ser., vol. XVIII, 1904, pp. 435-440. 



