THE ARTESIAN WATER SUPPLY OF EASTERN FLORIDA. 89 
weathers to a sticky blue clay. The Chattahoochee Limestone is 
difficult to recognize in well samples. Fossils in this formation are 
comparatively rare and such as occur are preserved as casts and are 
largely destroyed in drilling. In surface exposures it may be recog¬ 
nized by its lithologic characters and by the characteristic cubical 
blocks into which some of the strata break upon exposure. 
The Apalachicola group has not been recognized from well 
drillings in East Florida. Clays taken by Mr. S. L. Hughes from 
the new city well at Jacksonville at the depth of 320 feet have 
a very close resemblance to the fullers earth clays which occur 
in the Apalachicola group above the Chattahoochee Limestone. 
On the other hand Matson obtained from Jacksonville a Miocene 
shark’s tooth from a well sample supposed to come from the depth 
of 496 feet. In order to determine more fully the area and extent 
of the Apalachicola group of formations in eastern Florida it will 
be necessary to obtain large and carefully collected well samples. 
The wide distribution of this group in West and South Florida leads 
one to believe that it is likely to occur very generally underlying Easi 
Florida. 
b 
MIOCENE. 
The Miocene deposits are well developed i‘n eastern Florida. At 
the ci'ty water works at Jacksonville this formation was encountered 
in excavating for the basin for the city water supply,* and was 
also reached in the city wells at a depth of from 35 to 36 feet. At 
Jacksonville this formation has a considerable, although un¬ 
determined, thickness. It consists of a buff limestone grading to 
a lighter color, more or less phosphatic, grading below to phosphatic 
sands and sandy marls. The formation is in places fossiliferous, 
although the shells are usually preserved as casts. 
In Clay County the Jacksonville formation is extensively ex¬ 
posed along Black Creek. The exposure of this foimation appears 
along both the south and north fork, of Black Creek some miles 
above Middleburg, and may be observed for five or six miles below 
Middleburg. The following section was observed at High Bluff, 
on the south fork of Black Creek about five miles above Middle- 
burg: 
*DalI, W. H„ U. S. Geol. Surv. Bull. 84, 124-125, 1892. 
