Fie oe

aS

changes to a buff to white color, due to the leaching of the coloring

 

   
   
   
   
  
   
  
   
   
   
   
   
     
  
  
 
   
  
   
   
    
   

238 THE COASTAL PLAIN OF NORTH CAROLINA.

of marl are seldom more than a foot in thickness and usually do not
have a lateral extent of more than 10 or 12 feet. Beneath the Pleisto-
cene covering of the divides, no doubt, there are places where the Duplin
covers the. Castle Hayne over a peace area. South of the Cape Fear
River the Duplin formation seems to rest directly upon Cretaceous beds.
All the evidence that has thus far been obtained seems to indicate the
almost complete absence of any Eocene strata in Columbus, Bladen, and
Robeson counties, and there the Miocéne is found in close contact with
the underlying Cretaceous beds.

In most particulars the Duplin strata are similar in lithologic
characteristics to those of the Yorktown formation. Fragmental shell
beds are well developed in many places and consist almost entirely -
of broken molluscan shells in a matrix of fine sand in which are some
small water-worn pebbles and occasional perfect shells that show no
effect of wave action. The deposits were evidently formed in shallow
water near the shore-or perhaps on the beaches where the rising and
falling tides reduced the shells to fragments. At times, however, perfect
shells were washed into the same places, and if soon buried by the
loose débris, were preserved intact. Thus these fragmental shell layers”
have long been known as excellent collecting localities and have yielded
great numbers of beautiful fossils i in an almost perfect state of pres
ervation.

Fine quartz sand constitutes the major portion of the Duplin strata
as in the case of the other Miocene formations. There is a consider-
able admixture of argillaceous material in most places. The argil-
laceous sand is bluish-green in color when freshly exposed, but soo

material, which consists primarily of iron carbonate. alg
In the Natural Well near Magnolia there is a deposit of light green
‘argillaceous sand cemented in certain places to form a sandstone. Th
lies immediately beneath the shell marl and has been thought
some investigators to belong to the Eocene. Sufficient evidence
such a correlation is lacking, and it is, therefore, referred to the Duy
In the vicinity of Lake Waccamaw an unusual phase of the Dupl:
formation is developed. Outeropping along the bluff on the m
shore of the lake there is a compact fossiliferous limestone that
tains many casts of Molluscan shells, Crepidula being especial
dant. This limestone is overlain by a loose characteristic shell
and is underlain by yellowish-brown sand that at the base

 

some phosphatic pebbles and water-worn casts of Cretaceous fos

This phase of the Duplin formation is not known to occur e
in the State, though it is well developed along the Peedee River
South Carolina, particularly in the vicinity of Bostick, — es