1889] MARYLAND ACADEMY OF SCIENCES. 45 



ADDITIONS TO OBSERYATIONS ON THE CRETACEOUS AND 

 EOCENE FORMATIONS OF MARYLAND. 



By p. R. UHLER. 



A closer inspection of some localities in which characteristic 

 exposures of the Cretaceous and Eocene formations of the West- 

 ern Shore of Maryland exist has brought more clearly to view 

 the real structure, relations, and modifications of the two forma- 

 tions, and has given an insight into the methods to be adopted 

 in the study of the deposits. 



An examination of many parts of their base lines and points 

 of contact over the principal tracts of country, between the bayed- 

 out estuary of the Magothy river and the Potomac at Fort 

 Washington, shows that the Cretaceous Lower Marl beds rest 

 directly upon the denuded and broken body of the Albirupean 

 formation, at almost all accessible places. Along the Magothy 

 and Severn rivers, the Cretaceous marl strata rest upon a moder- 

 ately thick stratum of ferruginous sandstone, which in turn 

 overlies the white sand, or at the inner boundary the sandy 

 surface of the white clay. On the Patuxent river, however, the 

 Cretacaous Lower Marl beds rest upon the mixed, disturbed 

 surface of the Albirupean white clay, which is much thinner 

 than in the foregoing localities. Along the Potomac river no 

 exposures of the Cretaceous marl strata appear between the 

 Eastern Branch and Swan Creek, and the Albirupean white clay 

 forms chiefly a thin stratum, directly overlaid by the Quater- 

 nary, possibly of the Columbia formation. This last series of 

 beds spreads from the margin of the Potomac back upon the 

 highlands, and hides from view such remnants of the Creta- 

 ceous or Eocene beds as might have remained on the less 

 denuded parts of the terraces after the great baying-out of this 

 tract of country had taken place. 



South of the Eastern Branch a narrow stratum of the Albi- 

 rupean clay is exposed in the banks of the Potomac river. This 

 stratum overlies the Baltimorean dark or variegated clays that 

 rise from beneath the level of the water, and which occur at 



