4 PROCEEDINGS OF THE INDIANAPOLIS MEETING. 



layers of such clay and brick-red loam like that of the upper member. This silicious 

 clay sometimes contains well-preserved leaf impressions and other plant fossils. It 

 is largely used in the manufacture of pottery in northern Mississippi, western Ken- 

 tucky, and particularly in western Tennessee. (3) The basal member is commonly 

 made up of irregularly stratified lead-colored or gray silicious clay (less pure than 

 that of the middle member), red or brown sand, gray silt, etc. The middle and lower 

 members commonly merge insensibly, as do the upper and middle members in most 

 sections ; but sometimes a sharp division plane demarks the upper loam and the sub- 

 jacent clays, the clay strata are truncated as if by erosion, and pellets and lenses of 

 the clay are incorporated in the overlying loam. This relation suggests unconformity ; 

 but it probably represents nothing more than a common type of transition from slack- 

 water deposits to the products of stronger currents. From the Big Black river to the 

 Ohio the brick-red loams and sands and the attendant gravel beds form the surface 

 over a zone 20 to 50 miles broad lying east of the limits of the newer Columbia for- 

 mation, though they have been deeply and widely trenched by all of the larger rivers. 

 The thickness of the formation at Holly Springs, Mississippi, and La Grange, Ten- 

 nessee, is about 200 feet, while the artesian borings at Memphis indicate a thickness 

 of no less than 435 feet for the middle and lower members. North of the Ohio, in 

 southern Illinois, the formation is a pebbly red loam or sand, sometimes distinctly 

 stratified. In central Arkansas, notably at Little Rock and about Malvern, pebbly, 

 red loams, undoubtedly representing the same formation, are occasionally found over- 

 lying the glauconitic Eocene sands and the older formations alike, and are overlain 

 in turn by a series of deposits correlated with the Columbia formation of the east. 

 The pebbles here are distinctive, those of Malvern in particular consisting chiefly of 

 rounded and subangular fragments of novaculite. 



A significant feature of the Appomattox formation in the Mississippi emba3'ment 

 is the enormous aggregate volume of gravel. East of the Mississippi the pebbles 

 composing this gravel are commonly subangular or rounded fragments of chert, 

 largely derived from the Sub-Carboniferous of the interior basin but partly from the 

 Silurian and other strata. The distribution of this gravel, as well as the distribution 

 of the formation in general, indicates that during the period of deposition of the forma- 

 tion the Tennessee river embouched directly into the Mississippi embayment of that 

 period not far from what is now the northeastern corner of Mississippi, Another 

 significant yet somewhat puzzling feature of the formation in its northern portion is 

 found in the great beds of fine-textured and often snow-white silicious clay interca- 

 lated in the middle member and in the flecks and streaks of like material found 

 throughout the loam of the upper member. It would seem possible, if not probable, 

 that the greater part of this distinctive material consists of disintegrated chert, which 

 was conveyed into the slack-water estuary anterior to the transportation of the non- 

 decomposed chert by the stronger currents attending the close of the Appomattox 

 period; so that the resemblance of the white markings to those in the eastern exten- 

 sion of the formation appears partly fortuitous. Still another significant feature of 

 the formation is the accumulation of plant remains within it in northern Mississippi 

 and western Tennessee and Kentucky. The fossils collected during the present season 

 have not yet been studied, but the specimens collected by Safford and Loughridge 

 have been examined by Lesquereux and Ward. It should be observed, however, that 

 the age indicated by the few fossils thus far identified is hardly consistent with the 

 voluminous evidence of stratigraphic position. 



The known geographic distribution of the formation has been materially extended 

 by the season's work. Originally it overspread the entire state of Mississippi, save a 



