Maryland Geological Survey 59 



is about 100 feet, which is further reduced to not over 50 feet in central 

 Prince George's County, and with intermittent outcrops finally thins out 

 by the overlapping of later formations in northern Charles County. The 

 Earitan formation evidently thickens for a certain distance along the 

 dip, as for example, in the deep well at Middletown, Delaware, where 

 about 350 feet of materials are referred to this formation. 



Stratighaphic and Structural Relations. — The Earitan formation 

 rests unconformably on the Patapsco formation, marked irregularities 

 being found here and there along the line of contact indicating that rather 

 pronounced inequalities existed on the upper surface of the Patapsco at 

 the time of the deposition of Earitan strata. In general, the contact is 

 sharply defined and at some points is marked by a line of broken and 

 redeposited iron crusts. 



The Earitan formation was eroded and transgressed toward the south 

 by the Magothy formation. In southern Prince George's and Charles 

 counties, however, the transgressing Eocene deposits overlie the Earitan 

 beds, the strata being finally entirely overlapped in northern Charles 

 County. 



The internal stratigraphy and structure of the Earitan is complex 

 oecanse of the wide variability in the character of the materials, ranging 

 as they do all the way from gravels and coarse sands to plastic clays. The 

 rapid variation in the sands and clays both horizontally and vertically 

 renders it impossible to subdivide the Earitan into members of more than 

 very local importance. 



The Earitan strata are evidently affected slightly along the western 

 margin of the outcrop, particularly in the more distant outliers, by the 

 warping of the beds which evidently occurs along the " fall-line " as shown 

 by the marked difference in dip in the Lower Cretaceous formations in 

 passing from the " fall-line " eastward. Local variations in dip also occur 

 which suggest slight folding. 



Organic Eemains. — The Earitan deposits have yielded both animal 

 and plant remains. The fauna is very meager both in individuals and 

 species, but the flora is much more abundant, particularly to the north 



