1892] MARYLAND ACADEMY OF SCIENCES, 185 



4LBIRUPEAN STUDIES. 



By r. R. Uhler. 



An analysis of tlio beds and groups of strata belonging 

 to the Albinipean series opens out numerous questions 

 relative to the original structure and later modifications 

 of the whole column of beds underlying the Greensand 

 or marine Cretaceous system of the Atlantic States, south 

 of New England and north of North Carolina. 



The writer has now no hesitation in referring all the 

 members of the groups of strata which are in place be- 

 tween the top of the genuine " Variegated Clays" of the 

 Iron Ore series and the bottom of the marine Cretaceous 

 formation to the Albirupean formation. 



The writer claims for this complex of strata and beds a 

 distinctness of origin, a difference in type of deposition, 

 a different direction in the deposition of the materials com- 

 posing the fundamental beds, a consequent unconformity 

 with the underlying or Potomac formation, a non-concur- 

 rence in the extension of the two formations, a different 

 position for their shore lines, and a different set of rep- 

 resentative fossils for the two formations. 



This position here taken is based upon a comparison 

 of the sand, sandy clay and clay, as to their physical 

 elements, contents and composition, and the conclusion is 

 that the Albirupean formation has been laid down mainly 

 within the barriers of, and chiefly upon the eroded, hol- 

 lowed and uneven surface of the Potomac formation. 



Consequently, that the Albirupean is much the younger, 

 and, where undisturbed, holds within its beds a more 

 recent fauna and flora. 



Whatever may be said of the beds on Martha's Vine- 

 yard, which contain the fossil flora of a Cretaceous type, 

 we are enabled to see that there is a fossil flora of the 

 beds in the northeastern part of Middlesex county, near 



