216 PHYSIOGRAPHY AND GEOLOGY OF THE COASTAL PLAIN PROVINCE. 



post-Lafayette erosion the Coastal Plain was gradually lowered beneath the 

 waves and the Sunderland sea advanced over the sinking region. The 

 Sunderland submergence was not as great in extent as the Lafayette sub- 

 mergence and a portion of the Coastal Plain remained above water. The 

 waves of the Sunderland sea cut a scarp line against the existing headlands 

 of the Lafayette and older rocks. These scarp lines are prominent in some 

 places and obscure in others, for the reason that sea cliffs were not always 

 cut as the ocean was bordered in some places by sandy beaches, while in 

 other places the low cliffs cut in the unconsolidated sediments have now been 

 entirely worn away. The waves supplied the materials, the undertow and 

 shore current swept it out and deposited it ; the basal member of the Sunder- 

 land formation, a mixture of clay, sands and gravel, representing the work 

 of currents along the advancing margin of the Sunderland sea. The upper 

 member of clay and loam was deposited on the other hand in deeper water 

 after the shore-line had advanced farther westward as only the finer materials 

 could be carried into the deeper waters. Ice-borne boulders are also 

 found scattered through the formation at all horizons. These were carried 

 by the ice that floated down the principal streams. The cold climate which 

 prevailed during the Sunderland period seems to indicate the contempora- 

 neity of the Sunderland period with the glacial epoch. It has, however, thus 

 far not been possible to correlate the different periods of ice advance with 

 the several Pleistocene formations of the Atlantic Coastal Plain. 



After the deposition of the Sunderland formation the country was again 

 elevated above ocean water, and erosion began to tear away the Sunderland 

 terrace. This elevation, however, was not of long duration, and the country 

 eventually sank below the waves again. At this time the Wicomico sea 

 repeated the work which had been done by the Sunderland sea, depositing 

 its materials at a lower level and cutting its scarp line in the Sunderland 

 formation. At this time there was also a contribution of ice-borne boulders 

 which were deposited miscellaneously over the bottom of the Wicomico sea, 

 although more numerous in the vicinity of the larger streams. These are 

 now frequently found imbedded even in the finer material of the Wicomico 

 formation. 



At the close of Wicomico time the country was again elevated and eroded 

 and then lowered to receive the deposits of the Talbot sea. The geological 

 activities of Talbot time were a repetition of those enacted during the Sun- 

 derland and Wicomico epochs. The Talbot sea usually cut its scarp line in 

 the Wicomico formation but at times transgressed the latter completely and 

 cut into the Sunderland or the underlying Cretaceous or Tertiary beds. Its 



