274 FLORIDA STATE GEOLOGICAL SURVEY. 
3. Bluish green to gray sands, variable in 
character. Lime inclusions begin to 
appear in these sands at 20 feet from 
the base. These become more num¬ 
erous until the material passes 
gradually into the sandy-marl above. 
Compact sandy marl with concretions 
near the base and with an ostrea 
34 
feet 
18 
to 
52 
feet. 
layer 6 feet above the base. 
Chattahoochee limestone above water 
8 
feet 
To 
to 
18 
feet. 
level . 
10 
feet 
0 
to 
10 
feet. 
By following* a small stream entering* at the south end of Rock 
Bluff the following supplementary section was obtained. 
Section About One Mile Southeast of Rock Bluff. 
14. 
13. 
12 . 
11 . 
10 . 
9. 
8 . 
Thickness Height above river 
Superficial sand at the surface. of stratum. 
Reddish, coarse sand, “Altamaha Grit” 
phase. The surface of the ground 
near the brink of the cliff is profusely 
covered with iron concretions, re¬ 
maining as residual material from 
the decay of the formation. The first 
1 to 4 feet of the saftd is discolored 
and mottled and shows a tendency to 
the formation of iron stained crusts. 
Iron concretions occur in the sand 
from the surface to a depth of seven 
feet. These show a tendency to¬ 
wards arrangement in layers. One 
such layer is observed to .extend 
from the mottled and decayed surface 
material downwards and horizon¬ 
tally into material apparently not ap¬ 
preciably affected by decay. The sand 
is usually cross bedded, containing 
white siliceous pebbles . 
36 
feet 
164 
to 200 
feet. 
Partly covered by land slides and with 
some seepage water emerging near 
the base ... 
.15 
feet 
149 
to 164 
feet. 
Sandy yellowish laminated clays giving 
rise to small springs .. 
2 
feet 
147 
to 149 
feet. 
Pink clays, free from sand and very 
plastic . 
2 
feet 
145 
to 147 
feet. 
Yellow sandy clays ... 
3 
feet 
142 
to 145 
feet. 
White water worn elongated siliceous 
pebbles imbedded in yellow sandy 
clays and lying with long axis paral¬ 
lel with the lines of stratification... 
1 
foot 
141 
to 142 
feet 
