Maryland Geological Survey 57 



River. In Cecil County the width of outcrop attains a maximum of five 

 to six miles along the dip, which is gradually reduced toward the south- 

 east although expanding to some extent in northern Anne Arundel 

 County until in central and southern Prince George's County it consists 

 only of a narrow belt at times interrupted for considerable distances along 

 the bluffs facing the Potomac River. The surface continuity of the 

 formation is also interrupted by the waters of the Chesapeake Bay and 

 the larger streams which flow across its outcrop. Outliers are found in 

 the higher hills to the south and southwest of Elkton, and also in northern 

 Anne Arundel and Prince George's counties where they occur at times 

 several miles to the west of the main outcrop. 



Lithologic Characters. — The Raritan formation consists largely of 

 white or buff sands and white, pink, drab, or variegated clays, the strata 

 changing rapidly in character both horizontally and vertically. The 

 sands over wide areas form beds of nearly pure silicious grains and when 

 dry are very white in color showing the presence of a very small per- 

 centage of hydroxide of iron. The white sands are more extensively 

 developed in the upper part of the formation. The lower strata are gen- 

 erally much more highly colored and often indurated by the deposit of 

 larger quantities of iron oxide which at times produces a characteristic 

 tube-like structure, these deposits being known as " pipe ore." The indu- 

 rated beds as already stated are well shown at Rocky Point near the mouth 

 of Back River in Baltimore County as well as along the lower courses of 

 Rocky and Stony creeks on the south side of the Patapsco River and at 

 White Rocks in the immediate vicinity. It is the latter locality which 

 afforded the name Albirupean employed by Uhler for the formation which 

 he established to include these and other deposits. The upper, purer 

 silicious beds have been extensively exploited as glass sands and large 

 pits have been opened along the upper reaches of the Severn River. 



Very coarse sands and even gravels are found at times well sorted but 

 rarely with angular cobbles, in this respect differing from the Patuxent 

 formation in which such materials not infrequently occur. At the same 

 time the sands and gravels contain very little arkosic material which is so 

 characteristic a feature of the Patuxent. The coarser sands and gravels 



