FLORIDA GEOLOGICAL SURVEY


Lithology

 For each well in a cross section, a
stratigraphic column was developed to represent
borehole lithology. The columns were based on
either existing descriptions or new descriptions
generated for this report. Hatch patterns depict
primary lithologies in the columns, with
accessory minerals shown on the right of the
columns as text codes. Where space is
available, the cross sections contain an
explanatory legend that defines mineralogic and
lithologic codes and patterns. For those cross-
sections without sufficient space to include the
"Explanation," it is also provided for reference
in Figure 9. Accessory-mineral codes are
generally the same as those used in the FDEP-
FGS lithologic database (FGS Wells). If the
volume of reported accessory sand-sized
minerals exceeds 5 percent, the content is
represented by a stippled sand pattern. If the
amount of accessory sand-sized minerals is less
than 5 percent, or if the amount is not known
based on existing descriptions, the accessories
are listed in the text codes. The mineral text
codes are listed in decreasing order of
abundance if the relative mineral abundance has
been reported.

 The degree of detail within each lithologic
column generally reflects the type of material
available for description as well as the degree of
detail in the description. In most cases, more
detailed lithology exists for the cores. The
minimum bed thickness represented on the
stratigraphic columns is 5 ft (1.5 m) due to
graphical constraints. There are several
examples where lithologies and accessory
minerals have been averaged over a 5 to 10 foot
(1.5 to 3.0 m) interval to accommodate this
graphical limitation.

Gamma-ray Logs

 Selected gamma-ray logs are plotted to the
right of stratigraphic columns on the cross
sections. These logs are used as a supplement to
delineate formation boundaries and allow
comparison of gamma-ray activity between the
various lithostratigraphic and hydrostratigraphic
units (e.g. Gilboy, 1983; Green et al., 1995;


Scott, 1988 and Davis et al., 2001). Gamma-ray
intensity units, when known, are shown on the
logs (horizontal axis) in counts per second (CPS)
or in American Petroleum Institute (API) units.
Inconsistencies between logs exist due to
different log settings (e.g., time constant, range)
and borehole characteristics (e.g., depth of
casing and lack of caliper logs to determine
sediment wash-out or cavities), making
quantitative comparison difficult. To allow
assessment of the high degree of variability in
the logs and to represent their natural response,
the intensity scales have not been normalized.
The logs are very useful in the identification of
correlative "packages" of gamma-ray peaks and
for comparison of the overall gamma-ray
signature within formational units. Relatively
high gamma-ray activity is generally correlative
with phosphate, organic materials, heavy
minerals and high-potassium clays. More subtle
changes may reflect dolomite and accessory
mineral content. Figure 10 summarizes general
relationships between gamma-ray activity and
mineralogy, the details of which are included in
the discussion of each lithostratigraphic unit (see
I i,ih, i, ogi,, O h', p. 30).

Aquifer Systems

 Aquifer systems on the cross sections appear
as hachured brackets on the left of each
lithologic column. Patterns used in the
hydrostratigraphic columns identify the three
major aquifer systems present in the study area,
as well as the MFCU.

 Map Development and Data
 Management

 For wells used in this study, elevations of
lithostratigraphic and hydrostratigraphic units
were recorded in a database that also included
the corresponding FDEP-FGS well accession
number (W-number), well name, comments
about the well, the geologist(s) who made the
determinations and well location (elevation,
latitude and longitude). The unit elevations on
which the maps are based are recorded in feet
BLS; a separate column calculates the elevation