*204 PI-IYSIOGRAPHY AND GEOLOGY OF THE COASTAL PLAIN PROVINCE. 



The Yorktown Formation. 



The Yorktown formation can be traced from southern Virginia south- 

 ward into North Carolina, the same materials and fauna persisting, but it is 

 unknown in northern Virginia and Maryland. To the south of the Hatteras 

 axis the Duplin formation is closely related to the Yorktown deposits. Dr. 

 Dall** in discussing this relationship says : 



"A study of these (fossils from the jSTatural Well) indicated their general 

 parallelism with the upper or Yorktown Miocene of Virginia, with which 

 their deposition may have been partially synchronous. The fossil species, 

 are, however, largely distinct from those of the Yorktown beds and of a 

 more tropical aspect. It is probably that in Miocene times, as at the present 

 day, there was a difference in the marine faunas of the two regions, that at 

 Yorktown and Suffolk being more allied to the subjacent temperate fauna of 

 the older Miocene of Maryland and Virginia, while that in North Carolina 

 contained more southern types. Yet even this seems hardly sufficient to 

 account for more than part of the difference. It is probable that with the 

 elevation of the Gulf and Florida coasts, which closed tiie deposition of the 

 cold-water Miocene on those shores, the changes in ocean currents which 

 made the water warmer and invited the return of the subtropical fauna, ban- 

 ished at the end of the Oak Grove epoch, extended at least as far as North 

 Carolina. To this change I ascribe part of the new aspect of the Duplin 

 fauna, which would thus be due to the combination of two factors." 



As already stated a correlation of the Atlantic coast with European Mio- 

 cene deposits cannot be readily made although according to Dall "the Mio- 

 cene fauna of Northern Germany compares well and agrees closely with that 

 of Maryland (and Virginia), while the Mediterranean Miocene finds a closer 

 analogue in the more tropical fauna of the Duplin beds of the Carolinas." 



Table of Miocene Formations. 



a Wagner Free Institute of Science, Trans.. Vol. ii, pt. 6, pp. 1598-1603. 



