MARYLAND GEOLOGICAL SURVEY 37 



signed the Maryland beds. In 1896 Darton published a bulletin under 

 the auspices of the U. S. Geological Survey, in which he brought together 

 a large number of well records throughout the Coastal Plain. He also 

 published the Nomini folio, and thus was the first to express, on a con- 

 tour map, the development of the Miocene throughout a large portion 

 of Southern Maryland. 



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. 



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 surficial 

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

 but the relation which existed between them was not understood and 

 little attention was given to the matter. To go into a full discussion of 

 the history of this separation would be to repeat much that has already 

 been said. Those who desire to look into the early history in more detail 

 are referred to the Keport on the Pliocene and Pleistocene of Maryland, 

 Maryland Geological Survey, 1906. It was not until Professor W J 

 McGee published his investigations of these deposits in 1887 and 1888 

 that their true relation with the underlying formations was at all under- 

 stood. He gave the name of Columbia formation to this entire series 

 of deposits and divided them into fiuviatile and interfluviatile phases 

 which he considered contemporaneous. Later, Darton, who took up the 

 work where McGee left it, discovered the Lafayette formation in St. 

 Mary's County and divided the Columbia formation of McGee into 

 an Earlier and a Later Columbia. In 1901, Shattuck, who had studied 

 the region in still more detail, separated the same deposits into four 

 formations, the Lafayette, Sunderland, Wicomico, and Talbot, the three 

 latter of which he united under the general term Columbia Group. He 

 also showed that these were developed in terraces lying one above the 



