MARYLAND GEOLOGICAL SURVEY 1:35 



ried on during Sunderland and Wicomico time. The Talbot sea cut 

 its scarp in the Wicomico formation, or in some places removed the 

 Wicomico completely and cut into the Sunderland or still older 

 deposits. Deposits were made on its terrace, a flat bench at the 

 base of this escarpment. Ice-borne boulders are also extremely com- 

 mon in the Talbot formation, showing that blocks of ice charged with 

 detritus from the land drifted out and deposited their load over the 

 bottom of the Talbot sea. 



Embedded in the Talbot formation at many places there are lenses 

 of drab-colored clay with plant remains. The stratigraphic rela- 

 tions of the lenses of clay occurring in the Coastal Plain show that 

 they are invariably unconformable with th'e underlying formation 

 and apparently so with the overlying sand and loams belonging to 

 the Talbot. This relationship was very puzzling until it appeared 

 that the apparent unconformity with the Talbot, although in a sense 

 real, does not, however, represent an appreciable lapse of time and 

 that, consequently, the clay lenses are actually a part of that forma- 

 tion. In brief, the clays carrying plant remains are regarded as 

 lagoon deposits made in ponded stream channels and gradually 

 buried beneath the advancing beach of the Talbot sea. The clays 

 carrying marine and brackish-water organisms are believed to have 

 been at first off-shore deposits made in moderately deep water, and 

 later brackish-water deposits, formed behind a barrier beach and 

 gradually buried by the advance of that beach toward the land. 



The last event in the geologic history of the region was a down- 

 ward movement, which is still in progress. It is this which has 

 produced the estuaries and tide-water marshes that form conspicuous 

 features of the existing to^x^graphy. At the present time the waves 

 of the Atlantic Ocean and Chesapeake Bay are at work tearing away 

 the land along their margins and depositing it on a subaqueous plat- 

 form or terrace. This terrace is everywhere present in a more or 

 less perfect state of development, and may be observed not only along 

 the exposed shores, but also on passing up the estuaries to their heads. 

 The materials which compose it are varied, depending both on the 

 detritus directly surrendered by the land to the sea and on the cur- 

 rents which sweep along the shore. On an unbroken coast the mate- 



