MARYLAND GEOLOGICAL SURVEY 



189 



lagoon was silted up more and more with mud derived from the sur- 

 rounding basin, the advancing beach came to rest on this lagoon de- 

 posit as a foundation and arrived at length at the point where the 

 lagoon had been filled up to the level of wave-base or higher. When 

 this place was reached another process was added to that of beach ad- 

 vance. Heretofore the waves and wind had been simply pushing for- 

 ward material over the advancing front but now that the mud deposit 



Fig. 10. Diagram showing later stage in advance of Talbot shore-line. 



in the lagoon had actually reached the level of wave-work and had 

 transformed the lagoon from a pond to a marsh or to a meadow, the 

 breakers attacked the upper portion of the lagoon deposit and eroded 

 it down to the level of wave-base as rapidly as they could reach it from 

 under the superficial veneer of the beach-sands. Cypress, cat-tails, 

 sedges, and other vegetation which had taken up their abode in the 

 marsh would be overwhelmed with detritus by the advancing beach 

 and a little later be destroyed by the breakers. In this way all traces 

 of life must be removed from the deposit except such as happened 



