MARYLAND GEOLOGICAL SURVEY 3i 



In 1898 Dall published a most important summary of existing knowl- 

 edge of the Tertiary of North America, in which he suggested a classi- 

 fication of the ^Maryland Miocene deposits and correlated them with 

 other parts of North America and of Europe. 



In Calvert County the Eocene is only slightly represented along the 

 south side of Lyons Creek and adjacent regions of the Patuxent Kiver. 

 A full account of the development of the present Imowledge of the 

 Eocene in Maryland would involve a discussion of the literature in regions 

 far beyond the borders of this county. Those who desire to look into 

 this subject are referred to the Eeport on the Eocene, by Clark and 

 Martin, Maryland Geological Survey, 1901, as well as to the reports of 

 the various counties which lie within the Eocene belt, particularly Anne 

 Arundel and Prince George's, which are now in preparation. Many in- 

 vestigators have contributed to the Eocene stratigraphy of southern 

 Maryland, among whom may be mentioned Say, Conrad, ^lorton, Rogers, 

 Lea, Tyson, and Heilprin. Darton, in 1891, included all the Eocene of 

 Maryland in one general formation for which he suggested the name 

 Pamunkey. Five years later, W. B. Clark discussed the Eocene deposits 

 of the Middle Atlantic slope both from a stratigraphical and paleonto- 

 logical point of view. He found the Eocene deposits as a whole divisible 

 into two stages, which were called Aquia Creek and Woodstock, and these 

 again were subdivided into seventeen distinct zones. In 1901, Clark 

 and Martin carried this work still farther and differentiated the Eocene 

 of ]\raryland into two formations, the Aquia and Nanjemoy. Each one 

 of these formations was further separated into two sub-stages and numer- 

 ous zones. A geologic map showing the distribution of the two forma- 

 tions throughout ^faryland was published and the fossils found within 

 the region were figured and described. 



Throughout all southern Maryland there is a well-defined mantle of 

 clay, loam, sand, and gravel which occupies the divides as well as certain 

 of the larger valleys. At first this was confused with the older deposits 

 on which it lies and was included with them in all geological discussions 

 of the region. Little by little it became apparent that these surflcial 

 deposits were distinct in age from the more fossiliferous beds beneath. 



