100 
.FLORIDA STATE. GEOLOGICAL SURVEY. 
hence its maximum thickness may be considerably greater. The marl 
furnished specimens of Carolia floridana Dali and Scuttella sp. 
In addition to the localities given above, the Alum Bluff formation 
is exposed at other localities, some of which will be enumerated in 
the succeeding paragraphs. 
An exposure at White Springs on the Suwanee River is referred 
to the Alum Bluff formation. The section given below was measured 
with a hand level at the point where the wagon bridge spans the river. 
1. Dark colored sandy loam . 1 foot. 
2. Dark colored semi-indurated sand. 5 feet. 
3. Unconformity . 
4. Greenish thinly-laminated siliceous clay.... 8 feet. 
5. Light yellow sand containing many-casts of shells. 17 feet. 
6 . Fine grained light gray sand .......... 11 feet! 
7. Light gray arenaceous and calcareous sandy marl. 51 feet. 
8. Light gray arenaceous marl with nodules of chert. 12 feet. 
9. Alternating beds of bluish sand and light green sticky marl con¬ 
taining thin layers of limestone, nodules of chert and some 
imperfect oyster shells ... . ..;.. 2 feet. 
10. Gray sand with thin nodular and brecciated layers of limestone.... 3 feet. 
11. Alternating beds of sand and light gray shell marl containing many 
well preserved fossils near the base of the section. 6 feet. 
River level reported four feet above low water stage. 
Nos. 1 and 2 of the foregoing section are the ordinary Quaternary 
sand which covers a large part of the State. 
Nos. 4 to 11 inclusive probably belong to the Alum Bluff forma¬ 
tion. 
From the material collected near the base of No. 11, Dr. Vaughan 
identified the following fossils: 
Locality:—White Springs, Florida, at water level, wagon bridge. 
Ostrea rugifera Dali. 
Pododesma scopelus Dali. 
Pecten madisonius var. sayanus Dali. 
Geologic horizon:—Apalachicola group, .Alum Bluff formation. 
On the Ocklocknee River, about one-quarter mile above Stuart 
Bridge, there is an exposure of thinly laminated light-gray to white 
marl. The outcrop has a thickness of about six feet, and the material 
is so brittle that it was difficult to secure fossils. 
Rocky Bluff on the Manatee River, about one mile from Ellenton, 
was visited by Heilprin, 1 who says: 
The “Bluff” we found to be a ledge of rock, rising about two or three feet 
above water-level at the time of our visit, and consisting of at least two well- 
defined layers—a basal white “marl” and yellowish sandstone, and an overlying 
sjliceous conglomerate. The latter is almost entirely deficient in organic re- 
Heilprin, Prof. Angelo. Wag. Free Inst, of Science, vol. i, 1887, p. 13.' 
