W J MCGEE — THE APPOMATTOX FORMATION. 547 



is in the direction of more complete admixture of the sand and clay elements in the 

 form of a moderately homogeneous loam. Still further southward the same characters 

 are generally maintained, although in central South Carolina and in some other local- 

 ities the hue of the formation is exceptionally rich and dark. Local variations also 

 occur at different points in Georgia, Alabama, and Mississippi ; and these may inva- 

 riably and certainly be assigned to the influence of contiguous formations or other 

 local conditions. So the Appomattox formation, as now known, may briefly be de- 

 scribed as a series of obscurel} 7 stratified and frequently cross-bedded loams, clays and 

 sands of prevailing orange hues with local accumulations of gravel about waterways, 

 the materials varying somewhat from place to place and always in the direction of 

 community of material between the formation and the older deposit upon which it 

 lies; while as a whole the deposit retains so distinctive and strongly individualized 

 characteristics as to be readily recognizable wherever seen. 



. The formation has been actually observed in thousands of exposures within a zone 

 of fully 50,000 square miles, commencing a few miles north of the Rappahannock at 

 Fredericksburg and extending southwestward between the Piedmont fall-line and 

 the inland margin of the Coast Sands (a phase of the Columbia formation) through 

 the Carolinas to central Georgia, and thence westward through Alabama and the 

 greater part of Mississippi. If the direct observation be supplemented by legitimate 

 and necessary inference, the formation must be so extended as to bridge the valleys 

 from which it has been degraded, and to stretch beneath the various phases of the 

 Columbia formation well toward the Atlantic and Gulf coasts; and with this legiti- 

 mate extension the field of the formation becomes essentially coextensive with the 

 Coastal Plain of the Atlantic and eastern Gulf slopes (exclusive of a part of Florida), 

 and assumes an area of 250,000 or 300,000 square miles. The amount of erosion suf- 

 fered by the formation in different parts of its area is significant, since in many cases 

 it is evidently connected immediately with the local composition and remotely with 

 the composition of the sub-terrane. Thus, the formation is generally preserved upon 

 loamy and clayey belts, much more seriously invaded by erosion upon sandy terranes, 

 and largely eroded from calcareous terranes. 



In stratigraphic relation, the formation unconformably underlies the Pleistocene 

 deposits (representing the southern extension of the Columbia formation), and un- 

 conformably overlies the various older formations of the Coastal Plain from the 

 probably Miocene Grand Gulf to the early Cretaceous or late Jurassic Potomac. In 

 some cases the Appomattox was laid down mantlewise upon strongly sculptured sur- 

 faces of older formations ; when the land lifted at the close of the Appomattox period 

 the waterways resumed their old lines, and the old sculpture was renewed ; then the 

 Columbia formation was similarly spread upon the Appomattox surface, and subse- 

 quently carved into like configuration ; and this complex history has given rise to a 

 complex distribution and interesting structural relations of the formation. 



No characteristic or diagnostic fossils have thus far been found in the Appomattox 

 formation; but its stratigraphic position, unconformably below the Pleistocene and 

 unconformably above the Miocene (?), indicates an age corresponding at least roughly 

 with the Pliocene. It represents a considerable part of a more or less vaguely de- 

 fined series of deposits, variously called "Orange Sand," "Drift," "Quaternary," 

 "Southern Drift," etc. ; yet since this vaguely defined series included not only the 

 Appomattox but also the basal gravel Led of the Pleistocene loess, parts at least of 

 the Cretaceous or Jurassic Potomac formation, and other deposits of various ages, 

 none of the old designations can be retained without material modification in delini- 



