SECOND ANNUAL REPORT—STRATIGRAPHIC GEOLOGY. 
113 
Locality: — Two miles above Middleburg, north side of Black 
Creek. 
Glycymeris subovatus Say. Cdrditamera cf. arata Conrad. 
Area st amine a Say. Cardium robustum Solander. 
Area cf. subrostrata Conrad. Venus cf. rileyi Conrad. 
The Jacksonville formation is exposed, at several points along the 
creek above this, locality, but the thickness of the outcrops seldom 
exceeds three or four feet. 
Excavations 1 at the city water works at Jacksonville revealed the 
presence of a yellowish siliceous limestone containing casts and molds 
of fossils. The specimens obtained from this locality included Pecten 
jeffersonius and Carditamera. 
According to Dali, 2 some of the rock at Live Oak and Lake City 
may also belong to the Miocene, but as yet this opinion lacks con¬ 
firmation. 
The log of a well drilled at the Jacksonville Water Works under 
the direction of R. N. Ellis, superintendent, indicates that the Jack¬ 
sonville formation was encountered at a depth of thirty-five feet. An 
incomplete set of samples from another well at this locality makes it 
possible to fix the top of the Vicksburg group at a depth of about 524 
feet from the surface. This leaves a thickness of 489 feet which, 
judging from the description of the well log, appears to be composed 
of sand, clay, shells, etc., to be assigned to the Miocene and the Apa¬ 
lachicola group of the Oligocene. From the presence of. a shark’s 
tooth belonging to a post-Oligocene species in a sample obtained at 
a depth of 495 feet, it would seem that the Miocene extends to that 
depth, and the Apalachicola group, if present is thus restricted to 
about thirty feet of alternating beds of hard and soft silicified rock. 
Lithologically, this material bears a much closer resemblance to the 
overlying Miocene beds than it does to the Oligocene, and this has led 
to the inference that the Miocene may here rest directly upon the 
Vicksburg group. 
In the well at the Ponce de Leon Hotel, St. Augustine, about 
thirty-seven miles southeast of Jacksonville, the Miocene appears to 
have been encountered at a depth of 110 feet. According to Dali, 3 
the Miocene fossils Venus rileyi, V. permagna and Area limula were 
encountered at a depth of 208 feet, while fossils characteristic of the 
Vicksburg group were obtained at 224 feet. This would indicate that 
1 Dali, Wm. H. Neocene of North America. U. S. Geol. Survey, Bull. 84, 
1892, p. 124. 
2 Ibid, p. 125. 
3 Dali, Wm. H., Neocene of North America, U. S. Geol. Survey,. Bull. 84, 
1892, p. 125. 
