McGee — Southern Extension of Appomattox Formation. 15 



Art. II. — The Southern Extension of the Appomattox Forma- 

 tion ;* by W J McGee. 



Contexts: Introduction, p. 15 — General Characters and Relations, p. 19 — Geo- 

 graphic Distribution, p. 28 — Hypsographic Distribution, p. 30 — Stratigraphic 

 Relations, p. 31 — Taxonomy, p. 33 — Sources of Materials, p. 34 — Interpretation, 

 p. 35. 



Introduction. 



In a paper entitled " Three Formations of the Middle 

 Atlantic Slope," published in the American Journal of Science 

 early in 18$8,f a distinctive late Tertiary formation, well 

 displayed on the Appomattox river in eastern Virginia, was 

 defined and named after that river ; and its principal charac- 

 ters, its distribution, its stratigraphic relations, and its probable 

 age were briefly recorded. The formation was then known to 

 consist of a series of predominantly orange-colored, nonfossil- 

 iferous sands and clays, resting un conformably upon Miocene 

 and older formations, and unconformably overlain by the 

 Columbia formation ; it was known to expand southward, 

 from a thin and discontinuous bed exposed in a narrow belt on 

 the Rappahannock river, so rapidly as to form a terrane many 

 miles in width on the Roanoke ; and it was inferred to repre- 

 sent at least a part of the Orange Sand of Hilgard and other 

 southern geologists. 



The several lines of research concerning the phenomena of 

 the Middle Atlantic slope recorded in this paper have recently 

 been extended southward into the Carolinas, Georgia, Ala- 

 bama, and Mississippi ; and some of the results of the work 

 are deemed worthy of publication. 



The Coastal Plain commencing in the Middle Atlantic slope 

 at Sandy Hook extends southwestward to the southeastern 

 angle of the continent forming Florida, and thence westward 

 and southwestward to the boundary of the national domain on 

 the Rio Grande. Throughout the sweep of nearly two 

 thousand miles from the mouth of the Hudson to the lower 

 Mississippi, the geographic division so trenchantly defined in 

 the Middle Atlantic slope is well marked, although its inner 

 boundary is less conspicuous in the south than in the north ; 

 for in the Southern Atlantic and Eastern Gulf slopes it is 

 commonly crossed at right angles by the rivers (the Alabama 

 alone marking it for a considerable distance), while in the 

 Middle Atlantic slope the principal waterways depart from 

 their normal direction to follow its course, and thus give origin 

 to one of the most strongly marked physiographic features of 



*Read before the Geological Society of America, Dec. 27, 1S89. 

 f Third Series, vol. xxxv, pp. 120-143, 328-330, 367-388, 448-468. 



