MARYLAND GEOLOGICAL SURVEY 93 



has yielded no silicified trunks of cycads, so far as is definitely 

 kno^vn. 



StriJce, Dip, and Thickness.— The strike and dip of the Raritan 

 formation correspond closely with those of the Patapsco. The nor- 

 mal dip of the basal beds is about 30 feet to the mile, but this 

 increases toward the "Fall line." Within this area of outcrop in 

 Prince George's County the Raritan formation is relatively thin in 

 comparison with its thickness farther northeast. The estimated max- 

 imum thickness toward the extreme eastern margin of the belt of 

 outcrop in this county is about 100 feet. The thickness of the for- 

 mation seems to increase toward the southeast beyond the line where 

 it disappears beneath later deposits. 



Stratigraphlc Relations.— The Raritan unconformably overlies the 

 Patapsco formation, and is separated from the overlying Magothy by 

 another marked unconformity. In the region of its outcrop, Pleis- 

 tocene deposits of the Talbot, Wicomico, and Sunderland formations 

 overlie the edges of the Raritan and generally conceal the deposits 

 from view except Avhere erosion has removed these later beds. 



llie Magothy Formation. 



The Magothy formation takes its name from the excellent 

 exposures of the beds of this age along the Magothy River in Anne 

 Arundel County and was characterized by Darton^ in 1893. Later 

 work in Maryland seemed to indicate that these deposits represented 

 merely phases of deposition within the Raritan. On this supposi- 

 tion, the fossil plants found in them were supposed to be Raritan 

 forms and the stratigraphlc break was attributed to contempo- 

 raneous erosion. In New Jersey the Magothy deposits in the 

 vicinity of Philadelphia were placed in the Raritan, while those in 

 the region of Raritan Bay, under the name Cliffwood beds, were by 

 some geologists included in the Matawan on account of the presence 

 of glauconite and the great percentage of post-Raritan plants and 

 marine invertebrates, and by others were placed in the Raritan. 

 Recent studies of the fossils and careful stratigraphlc Avork in the 



iDarton, Amer. Jour. Sci., 3d ser., vol. XLV, 1893, pp. 407-419. 



