80 The Lower Cretaceous Deposits of Maryland 



XXII. Section at High Point, y^. to % mile below Glymont, Charles County. 



Cretaceous. 

 Patapsco 



Pleistocene. Feet. 



Talbot Loam and gravel 15 



Interbedded buff and more or less arkoslc sand, loose 

 and cross-bedded, with light drab clay, iron crusts 



at base 20 



Irregularly interbedded brown and light drab clay, 



grading down to brown sandy clay 7 



Brown sandy clay, with greenish-drab, chloritic, sandy 

 clay at tide 55 



Total 97 



XXIII. Section on Stump Neck, Charles County. 



Pleistocene. Feet. 



Talbot Brown gravelly loam 3 



Sand, gravel and cobbles 12 



Cretaceous, fCross-bedded, compact sand slightly arkosic 8" 



Patapsco . .- Massive green chloritic clay to tide, with lenses of drab 



[ clay carrying leaf impressions ^ 4 



Total 27 



INTEEPEETATION OP THE POTOMAC DEPOSITS 

 Potomac deposition was probably preceded by extensive base-leveling 

 of the eastern side of the continent, with accompanying widespread rock 

 disintegration. Stimulated by elevation and seaward tilting, the re- 

 vived streams transported these materials to their present position. The 

 fact that these deposits consist very largely of redeposited Piedmont 

 crystallines, and. to a less extent of Appalachian strata, is what might 

 be expected, but the circumstance that no clearly defined trace of re- 

 deposited Newark materials has been found in the Potomac deposits of 

 Maryland is somewhat surprising. From this we must infer either that 

 the Newark was not to any great extent exposed to Potomac erosion, or 

 that its materials were not sufficiently consolidated to permit of trans- 

 portation, except in so finely divided a condition as to be unrecognizable. 

 It is quite certain that during maximum Potomac subsidence a large 

 body of Newark materials, especially beyond the limits of Maryland, 

 was beneath tide level, and therefore not exposed to subaerial influences. 

 Inasmuch as the Potomac beds themselves, particularly the basal ones, 

 have since that date undergone considerable induration, often without 



* See list of species in Tables of Distribution. 



