IOO FLORIDA GEOLOGICAL SURVEY ELEVENTH ANNUAL REPORT. 
ner of Gadsden County and crosses the. Ocklocknee River near Lake 
Iamonia. The 50-foot contour starting from the Apalachicola 
River near Rock Bluff passes more nearly to the east, crossing the 
Ocklocknee River below the Seaboard Air Line Railway crossing. 
CONTOURS ON THE ALUM BLUFF FORMATION. 
Contours on the fullers earth horizon of the Alum Bluff forma- 
tion, if placed on the map in the same way by known and inferred 
levels, would indicate essentially the same structure as that shown 
by contours on the Chattahoochee formation. From the Apalach- 
icola River the contours on the fullers earth horizon run to the 
northeast, the 200-foot contour passing out of the state and crossing 
the tributaries of Little River somewhat north of Attapulgus, the 
actual level of the fullers earth at Attapulgus being 173 feet. The 
150-foot contour on this formation starting from near Rock Bluff 
passes northeast to Jamieson, near the State line. East of the Ock- 
locknee River and north of the Seaboard Air Line Railway in Leon 
County, the fullers earth horizon, if formerly present, has appar- 
ently been removed by erosion and disintegration. If the former 
place of this horizon should be inferred from known levels on the 
Chattahoochee formation, it would be assumed that its 200- foot 
contour re-enters Florida north of Lake Iamonia in Leon County, 
and that the 150-foot contour runs about as far south on the east 
side of the Ocklocknee River as the Georgia, Florida and Alabama 
Railway. The ioo-foot contour on this horizon has not been 
located on the Apalachicola River except by inference. The fullers 
earth is not found at Alum Bluff, and if formerly present was 
removed by erosion previous to the deposition of the Choctaw- 
hatchee formation. The eroded top of the Alum Bluff formation 
there lies at an elevation of about 70 feet above sea, and the fullers 
earth stratum would be expected to lie in that section at between 
100 and 120 feet above sea. 
On the Ocklocknee River the ioo-foot contour would cross 
somewhat south of Midway, where the actual level of the fullers 
earth horizon is 114 feet above sea. On this formation, as on the 
Chattahoochee formation, there is thus observed a flattening out 
and reduction in dip in passing to the south. Farther south the 
contours have possibly an east- west or north of west to south of 
east direction. 
