MARYLAND GEOLOGICAL SURVEY 



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rents of the Talbot sea rapidly built bars and beaches which ponded the 

 waters behind and transformed them from brackish-water estuaries to 

 fresh-water lagoons. These lagoons were gradually changed into marches 

 and meadows by the deposition of detritus brought in from the surround- 

 ing region and on this new land surface various kinds of vegetation took 

 up their abode (Fig. 7). At first the beach sands advanced in the lagoon 



Fig. 7. — Diagram showing advancing Talbot shore-line and ponded stream. 



and filled up completely that portion of the submerged trough which lay 

 immediately beneath them, but later as the lagoon was silted in more and 

 more with mud derived from the surrounding basin, the advancing beach 

 came to rest on this lagoon deposit 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 the beach advance. Heretofore the waves and wind had been 

 simply pushing forward material over the advancing front, but now that 

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