MARYLAND GEOLOGICAL SURVEY 73 



nous, but was interrupted by numerous oscillations in level, during 

 which the region was brought above the sea and suffered erosion, 

 only to be depressed again and re-loaded. These changes in the atti- 

 tude of the land in relation to sea-level have been recorded as uncon- 

 formities in the deposits, but they have left no noticeable record in 

 the topography, and their discussion is consequently deferred to a 

 later chapter. 



At the close of this period of sedimentation there was a general 

 uplift of the region, which brought Cecil county once more above the 

 sea. After this there followed a long period of erosion, which was 

 finally brought to a close by the entire county again sinking beneath 

 the ocean. This subsidence ushered in the Lafayette stage. 



THE LAFAYETTE STAGE. 



The subsidence which marked the beginning of the Lafayette stage 

 effected the entire Atlantic Coastal Plain from New Jersey south- 

 ward. In the northern portion of the area it is impossible to deter- 

 mine how far inland the waters of the Atlantic Ocean advanced, but 

 there is no doubt that Cecil county was entirely submerged and, at 

 the time of maximum depression, the waves of the Atlantic may have 

 washed the eastern base of the Blue Ridge. The date of this subsi- 

 dence has been doubtfully referred to the Pliocene period. 



While Cecil county was thus engulfed it received a load of deposits 

 which are now known as the Lafayette formation. 



At the close of the Lafayette depression Cecil county was again 

 lifted above the surface of the ocean, and probably to a much greater 

 extent than now. Chesapeake Bay at that time did not exist, but 

 its trough was occupied by the lower courses of the Susquehanna 

 river, which received as tributaries from the surrounding country 

 the streams which are now estuaries. Just how long the land re- 

 mained in this position it is impossible to say, but sufficient time 

 elapsed to permit the erosion of a large amount of the sediments 

 which had been brought up out of the Lafayette Sea. The Lafayette 

 formation was in a large measure stripped off from the Piedmont 

 Plateau region of Cecil county, as well as from the Eastern Shore 



