224 PHYSIOGRAPHY AND GEOLOGY' OF THE COASTAL PLAIN PROVINCE. 



The principal clay-bearing formations in the Virginia Coastal Plain 

 are the Nanjemoy, Calvert, Lafayette, Sunderland, Wicomico, and Talbot. 

 The Nanjemoy contains the compact pink or white clays previously 

 described as occurring in the vicinity of Fredericksburg, and in the region 

 south of Stafford Courthouse, where they form promising outcrops, but 

 have not yet been developed. The Calvert contains a great deal of sandy 

 blue clay which is found covering an extensive area in the western portion 

 of the Coastal Plain. These clays are best known south of Eichmond, in the 

 vicinity of Curie's Neck, and Bermuda Hundred. This same formation 

 also carries extensive beds of diatomaceous earth or clay, which is well 

 exposed at Eichmond and along the Eappahannock Eiver. 



The surface loams of the Lafayette, Sunderland, Wicomico, and Talbot 

 formations have also been used largely in various parts of Tidewater Vir- 

 ginia about Alexandria, Fredericksburg, Petersburg, Emporia, Suffolk, 

 Norfolk, Hampton, etc. Lying at the surface they can easily be worked as 

 it is only necessary to remove a few inches of the soil. Sometimes this clay 

 loam is used when only a little more than a foot in thickness but usually beds 

 of not less than three or four feet in thickness are worked. At times the 

 beds attain considerable thickness, as for example near the reservoir west of 

 Eichmond where the Lafayette clay loam is about 18 feet thick. More 

 or less gravel and boulders occur distributed through the loams either 

 in the form of isolated pebbles or as lenses or definite layers. These clays, 

 Pleistocene chiefly, occur ^s more or less basin-shaped deposits widely 

 scattered over the Coastal Plain region. 



Nearly all of the clay deposits noted in the Coastal Plain region, what- 

 ever their geological age, are of lenticular or lens-shaped character. The 

 majority of them are red-burning, while only a few are buff-burning. No 

 white-burning clays have thus far been found, but even though they lack 

 in variety, so far asi their color-burning qualities are concerned, it is prob- 

 able that their possible uses are more numerous than is now supposed. 



The amount of clay suitable for the Inanufacture of common brick 

 throughout the Coastal Plain is almost unlimited, and the distribution of 

 the deposits is such that brick sufficient for local consumption can be made 

 in almost every neighborhood. It is difficult to understand why these clay 

 deposits have not been more extensively utilized hitherto. Practically no 

 attempt has been made to use the higher grade clays at any point. 



The results of a study of the Virginia Coastal Plain clays, including 

 physical tests and chemical analyses, by Dr. Heinrich Eies in 1905, are 

 embodied in the table opposite page 225. 



