88 The Lowek Cretaceous Deposits of Maryland 



most of them show a descent much less than this amount, in one in- 

 stance (Crisfield) even less than the observed average landward dip 

 (12^ feet) of the Eocene deposits which immediately overlie the Potomac 

 beds to the southward. 



Distance from p„+« ,><• 



point where Depth of /ii:,^®?i„ 



Location of welL Potomac surface below f^^J „^ ' 



surface reaches tide level. X^jiS 



sea level. °^i^®- 



Miles. Feet. Feet. 



Rock Hall, Maryland 7 240 34 



Claiborne, Maryland 19 440 23 



Tunis Mills, Maryland 24 430 18 



Tilghman's Island, Maryland 27 400 15 



Gloucester Court-House, Virginia 38 600 16 



Williamsburg, Virginia 38 550± 14.5 



North End Point, Virginia 62 920 15 



Crisfield, Maryland 91 964 10.6 



According to these records, there is a marked lessening in the decline 

 of the Potomac surface far to the seaward. When the surface of^ the 

 Earitan formation is likewise considered there seems to be an actual 

 rise in this surface in the Eastern Shore of Maryland and Delaware, 

 between the Chester and Choptank rivers, although it again declines east- 

 ward a little farther seaward, as shown by the boring at Gloucester Court 

 House, Virginia. Whether we have to do with an erosional irregularity 

 in the Potomac surface or with incipient deformation, the facts at hand 

 do not permit us to determine. If the irregularity is due to the latter 

 cause, the axis of the anticline would not seem to be coincident with that 

 of the peninsula of Delaware, but would cross the latter in a northeast- 

 southwest direction. A depressed barrier, such as has above been indi- 

 cated, may well have served as the seaward buttress in such deformation. 

 Whether there may be more than one of these axial prominences in the 

 Potomac surface is a question of much interest, but which cannot be 

 answered with the data at hand. 



The lessening in the descent of the Potomac surface far to the seaward, 

 as indicated by borings at ISTorth End Point and Crisfield, is in general 

 in harmony with the relations of the subjacent crystalline floor above 

 described. 



