McGee — Southern Extension of Appomattox Formation. 21 



few gneissoid fragments. They range in size from two and a 

 half inches downward. Commonly they are accumulated in 

 lines or pockets, sometimes at the base of the formation ; but 

 a few also occur disseminated throughout the ill-defined strata. 

 . About the fall-line on the Santee river system, the Appomat- 

 tox loam is in part overlain unconformably by the Columbia 

 formation, though it has been severely degraded ; and in an 

 admirable section on the Richmond and Danville railway 

 immediately east of the State House, where both upper and 

 lower contacts are displayed; the Appomattox rests unconform- 

 ably on the Potomac. Further up-river the Appomattox rests 

 directly upon the Piedmont crystallines which here give origin 

 to residuary products of dark red and brown color ; and so the 

 origin of the exceptionally rich hues of the formation in this 

 region are not difficult to trace. 



Is is in Georgia that the formation appears to be best 

 developed : About the fall-line it stretches from the Savannah 

 to the Chattahoochee in practically unbroken continuity ; at 

 many points it overlaps far upon the Piedmont crystallines ; 

 on the seaward side of the fall-line it is unquestionably over- 

 lapped in turn by the pine clad sands of the Columbia forma- 

 tion over many thousand square miles; it evidently reaches a 

 considerable thickness — perhaps 100 feet or more ; and its 

 various features are in part intermediate between and in part 

 common with those displayed by the formation in the Atlantic 

 and Gulf slopes respectively. Moreover it exhibits in this 

 region certain significant features not known elsewhere. 



About Augusta, the exposures resemble those of the Conga- 

 ree, save that the exceptionally rich hues have faded to the usual 

 orange and orange-red ; while the cross-stratification marked by 

 lines of clay has become more, and the horizontal bedding even 

 less, conspicuous. There is an excellent exposure of the 

 gravelly loam of the formation at Green's Cut, south of Augusta, 

 on the Georgia Central railroad. It is made up at this point of 

 moderately homogeneous loam with little indication of bedding 

 save that the abundant pebbles are commonly arranged in lines 

 or accumulated in pockets, though sometimes disseminated. 

 Twenty miles farther southward, near Munnerlyn, there is an 

 exposure of 25 feet in which the loam is not only definitely 

 bedded but divided by intercalated layers of sand and silt, 

 giving an apjDearance of regular and distinct stratification ; 

 pebbles being small and rare, while the characteristic orange 

 tints run into dull browns and grays. There is a similar expo- 

 sure at Sun Hill, sixty miles east of Macon, in which the strata 

 are partially lithified, and the general aspect approaches that 

 of the regularly stratified Tertiary deposits of greater antiquity 

 found farther seaward. 



