188 THE COASTAL PLAIN FORMATIONS OF CECIL COUNTY 



buried by the advance of that beach toward the land. Taking up the 

 first class of deposits in more detail they are believed to have been 

 formed in the following manner: 



During the erosion interval which immediately preceded the depo- 

 sition of the Talbot formation many streams cut moderately deep 

 channels in the land-surface which on the sinking of the region again 

 were transformed into estuaries (Fig. 8). Across the mouths of the 



Fig. 9. Diagram showing advancing Talbot shore-line and ponded stream. 



smaller of these drowned valleys the shore currents of the Talbot sea 

 rapidly built bars and beaches which ponded the waters behind them 

 and transformed them from brackish-water estuaries to fresh-water la- 

 goons. These lagoons, however, were gradually changed into marshes 

 and possibly to meadows by the inflow of detritus from the surround- 

 ing region and on the new land-surface thus formed various kinds of 

 vegetation took up their abode (Fig. 9). At first the beach-sands ad- 

 vanced in the lagoon and filled up completely that portion of the sub- 

 merged trough which lay immediately beneath them, but later, as the 



