68 The Lower Cretaceous Deposits oe Maryland 



part of his Aquia Creek series as well as what he also called the Brooke 

 beds. 



Areal Distribution. — The Patapsco formation outcrops in Maryland 

 in a belt of varying width extending from the Delaware line southwest- 

 ward to the District of Columbia to the east of the preceding formation. 

 To the south of Washington it is found along the valley of the Potomac 

 to below Mattawoman Creek. From the Delaware line to the District 

 the belt has a width of about 5 miles, south of which it narrows appre- 

 ciably until it finally disappears in Charles County, although continued 

 on the west bank of the Potomac in Virginia. It is a much more con- 

 tinuous belt than the preceding Arundel formation. 



Outliers are found resting on the Patuxent formation. The surface 

 is rolling, resistant caps frequently occurring as the result of the fer- 

 ruginous crusts which are often developed. The Patapsco deposits have 

 been found all the way from hills 300 feet and more in elevation to a 

 depth of about the same amount in well borings. 



LiTiiOLOGic Characters. — ^The Patapsco formation consists of sands 

 and clays which differ, however, from those of the Patuxent formation 

 in the predominance of the argillaceous elements, especially the varie- 

 gated clays. The arkosic sands and gravels are much less common than 

 in the Patuxent formation. They are more common toward the southern 

 part of the area, where they at times become indurated, forming a part 

 of the well-known " Virginia freestone " of the Aquia Creek area. A 

 band of pebbles frequently marks the base of the formation, as in the 

 Hanover region. A bed of broken and redeposited ironstone crusts may 

 take the place of the pebbles, as near Hawkins Point on the Patapsco 

 Eiver. 



The most characteristic materials are the highly colored and varie- 

 gated clays with their red, drab, and chocolate colors. The clays often 

 grade into or are interbedded with sandy clays, sands, and gravelly 

 sands. They are at times lignitic, a typical illustration being the lignitic 

 sandy clay at Fort Foote, Pellets of fossil resin at times occur with the 



