SECOND ANNUAL REPORT—STRATIGRAPHIC GEOLOGY. 95 
to form steep slopes. Thus the region where the Alum Bluff forma¬ 
tion lies near the surface is characterized by a topography which has 
been formed by surface erosion and which is in marked contrast to 
the sink hole topography of the central part of the peninsula. How¬ 
ever, wherever this formation is thin, solution has given rise to many 
sink holes; and the topography is a composite of valleys and poorly 
drained depressions. 
Paleontologic Characters:—-As already noted, the typical sands of 
the Alum Bluff formation are sparingly fossiliferous, the lower part 
containing a fauna allied to the underlying Chipola marl member, and 
the upper part being characterized by plant remains. The fullers 
earth beds contain a very poorly preserved fauna, from which 
Vaughan 1 secured enough material to show that they belonged to 
the Alum Bluff formation. He also notes the fact that these beds con¬ 
tain Carolia floridana Dali, which is characteristic of the Apalachicola 
group. Both the Oak Grove sand member and the JShoal River marl 
member are very fossiliferous. 
Structure: — The Alum Bluff formation shows no marked pecu¬ 
liarities of structure. While it has undoubtedly been affected by some 
of the movements which produced the general arching of the strata, 
the disturbance has not produced any effect, except to give a general 
seaward dip to the beds. If any local deformation has produced fold¬ 
ing of the beds belonging to the Alum Bluff formation, the existence 
of the folds has not yet been detected. 2 However, this may be due 
to the imperfect exposures. 
Local Details:—Micaceous white sands belonging to this forma¬ 
tion are well exposed on Ten-Mile Creek, at Carrs Mill, in Calhoun 
County, and at intervals for about one mile farther up stream. Here 
they consist of coarse light-gray sands containing many flakes of sil¬ 
very white mica. Upon weathering, the sand changes to a pale yellow 
color from the presence of hydrated iron oxide. The sands show some 
evidence of cross bedding and appear to be destitute of organic re¬ 
mains. Similar sands are reported in wells farther west in Walton 
County, and exposures were noted beneath the Shoal River marl mem¬ 
ber near Knoxhill, Walton County. 
Vaughan's 3 investigations have shown that the fullers earth beds 
kre the stratigraphic equivalent of the sands at Alum Bluff. About 
four miles southeast of River Junction, at an abandoned fullers earth 
1 Vaughan, T. Wayland. Unpublished notes. 
2 See, however, structure of fullers earth strata in paper on fullers earth. 
8 Vaughan, T. Wayland. Fullers earth, U. S. Geol. Survey, Mineral Pe- 
sources of the United States, 1901, pp. 926-927. 
