SECOND ANNUAL REPORT—STRATIGRAPHIC GEOLOGY. 
89 
White sand .... 
Yellow sand ... 
Pliocene breccia 
Tampa limestone 
Tampa silex bed 
6 to 24 inches. 
6 to 36 inches, 
traces. 
10 to 15 feet. 
6 to 10 feet. 
In drilling wells at the Tampa water works, between Sixth and 
Seventh avenues, the “silex bed” was found to have a thickness of 
only four feet. Beneath the “silex bed” there was a thin bed of lime¬ 
stone underlain by greenish clay, which varied in thickness from 
forty-one to sixty-four feet. The log of one of these wells follows: 
1. White Pleistocene sand . 2 feet. 
2. Tough yellow clay with no sand, residual clay. 10 feet. 
3. Soft limestone which disintegrates readily—“Tampa limestone”... 14 feet. 
4. Chert, “Tampa silex bed”. 4 feet. 
5. Soft limestone closely resembling No. 3. 6 feet. 
6. Tough plastic greenish sandy clay . 41 feet. 
Base of the Tampa formation: 
7. Chert . 2 feet- 
8. White marl . 6 feet. 
9. Soft limestone . 6 feet. 
10. Very light colored hard rock. 15 feet. 
11. Very hard dark yellow limestone. 6 feet. 
12. Gray porous limestone with some water. 15 feet. 
13. Cherty beds . 14 feet. 
14. Darker limestone. 
] 5. Gray plastic clay. 
16. Hard yellow rock with chert. 
17. Gray porous rock, water-bearing. 
18. Like preceding. 
Nos. 3-6 inclusive represent the Tampa formation, but at this lo¬ 
cality the upper clay and a portion of the limestone have been re¬ 
moved by erosion. 
Another well 200 feet away encountered sixty-four feet of No. 6, 
which suggests an unconformity at base of this bed, and this hypothe¬ 
sis is strengthened by the fact that the rock immediately below the 
clay differed in the two wells. 
The upper clay bed of the Tampa formation is best exposed at the 
pit of the Tampa Brick Company on the bank of the Hillsboro River 
five miles northeast of the city. At this locality there is an exposure 
of from ten to fourteen feet of light green siliceous clay which is 
unconformably overlain by from two to four feet of light-gray Pleis¬ 
tocene sand. The clay is very plastic and is said to make excellent 
brick. Scattered throughout the deposit are numerous cobbles and 
boulders of chert which represent silicified corals. While the major 
portion of the exposure is of a light greenish color toward the bottom 
