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THE GEOLOGY OF CALVERT COUNTY 



ever, represent an appreciable lapse of time and that therefore the clay 

 lenses are actually a part of that formation. In order to understand 

 more clearly what is believed to have taken place, these clay deposits 

 should be divided into two groups, those which carry plant remains con- 

 stituting one, and those containing marine and brackish-water fossils 

 the other. Such as are devoid of fossils may belong to either one of the 

 groups according to their situation but probably more frequently belong 

 to the latter. 



Fig. 5. — Diagram showing advancing Talbot shore-line and ponded stream. 



In a word, 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 de- 

 posits made behind a barrier-beach and gradually 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 : 



