120 FLORIDA STATE'GEOLOGICAL SURVEY. 
The contact line between 1 and 2 of the above section which was 
inaccessible at the time Dali’s section was made has recently been de¬ 
termined by E. H. Sellards, who has supplied the following section: 
5. Loose medium coarse pale yellow sand resembling the top sands 
at Alum Bluff ... 11 feet. 
4. Coarse cross bedded red sands containing pebbles up to x /i inch in 
length . 14 feet. 
3. Covered and sloping .. 8 feet. 
2. Dark colored micaceous clays... 4 feet 
1. Gray fossiliferous marl to the water edge... 25 feet. 
62 feet. 
On the south bank of Four-Mile Creek, about three-quarters of 
a mile north of Clarksville, in Calhoun County, the following section 
was observed: 
Covered by sandy loam ... 30 feet. 
Bluish gray marly clay (plastic). 14 feet. 
Very fossiliferous bluish gray shell marl, to water... 4 feet. 
The fossils observed here were the same as those which charac¬ 
terize the Choctawhatchee marl at Alum Bluff and elsewhere. Asso¬ 
ciated with the shells were a number of dark colored fragments of 
bones which are locally regarded as an indication that the deposit 
might prove valuable as a fertilizer. Even though these fragments 
may be phosphatic, they are not sufficiently abundant to be of economic 
value. 
At Alum Bluff, on the Apalachicola River, the Choctawhatchee 
marl was observed by Dali. At this locality the “aluminous clay” has 
a thickness of twenty-four feet, and is immediately underlain bv 
thirty-five feet of sandy shell marl which contains an abundant Mio¬ 
cene fauna. There does not appear to have been any abrupt physical 
break between the fossiliferous shell marl and the non-fossiliferous 
“aluminous clay,” though the latter appears to have a larger percent¬ 
age of clay than the former. Both have the same color and both are 
arenaceous; but the one is highly fossiliferous and the other barren of 
animal remains except for occasional obscure traces of gastropods and 
bivalves. 
Toward the north the shell marls thin to scarcely more than five 
feet. On the east side of the Apalachicola River, Mr. Burns 1 traced 
the Miocene marls from about five miles above Bristol southward 
about thirteen miles to where it finally disappears. 
The Choctawhatchee marl is exposed at various points on the 
Ocklocknee River. 
1 Dali, Wm. H., Neocene of North America, U. S- Geol. Survey, Bull. 84, 
1892, p. 124. 
i 
