BULLETIN NO. 68


Figure 38. Statistical summary of UFA total po
volumetric analyses completed at the FDEP-FGS.
outliers.


Middle Floridan confining unit

 Miller (1986) recognizes three confining
units within the study area (Units I, II and VI)
that separate the UFA from the LFA; however,
in context of the overall FAS he states: "... the
units act as a single confining unit within the
main body of permeable limestone that
constitutes the aquifer system." In the present
study, we adopt a more descriptive
hydrostratigraphic name for the Miller's (1986)
"middle confining unit" of the FAS: the Middle
Floridan confining unit (MFCU). This name
simply associates the confining units with the
aquifer system in which they reside. This
nomenclature has also been adopted by the
CFHUD II (Copeland, et al., in review).
Complexity of the MFCU within and beyond the
study area is readily apparent given the seven
units mapped by Miller (1986) separating the
UFA from the LFA in Florida. On a more local
scale, delineation of the base of the UFA
becomes challenging where overlapping
confining units of the MFCU occur.

 Within the study area, unit I occurs along the


rosity data based on results of core sample
 Asterisks in the box plot denote statistical



 eastern margin and is identified as a leaky
 confining unit that is "...not much different from
 that of the permeable zones vertically adjacent to
 it..." (Miller, 1986). Units II and VI are
 identified as carbonates (primarily dolostone)
 with intergranular gypsum and comprise a
 hydrogeologically significant confining facies
 that separates the UFA from the LFA in the
 study area.

 The MFCU mapped herein includes Miller's
 (1986) units II and VI and is principally
 identified based on lithology and mineralogy:
 borehole samples that contain thin
 gypsum/anhydrite beds or intergranular
 gypsum/anhydrite > five percent (by volume).
 While some may consider five percent too
 conservative (e.g., too high), a notable relative
 increase in matrix confining properties is the
 emphasis herein, recognizing that transition
 zones may occur, as well as zones where
 variable precipitation and dissolution of these
 minerals may have occurred. Geophysical logs
 and water-quality data are also used to identify
 or infer evidence of the MFCU. In addition to
 data generated for this report, data from Miller


 Summary for UFA Total Porosity (% )


 Anderson-Darling Normality Test
 A-Squared 1.91

 Mean 37.056
 StDev 8.601
 Variance 73.978
 Skewness -1.22649
 Kurtosis 2.93402
 N 117
 Minim urn 2.300
 0 10 20 30 40 50 1st Quartile 31.950
 M edian 38.730
 3rd Q uartile 42.625
 Maxim um 53.490
 95% Confidence Interval for Mean
 35.481 38.631
 95% Confidence Intervals 95% Confidence Interval for Median
 37.100 39.950
 Mean I 95% Confidence Interval for StDev
 7.622 9.870
Median I
 35 36 37 38 39 40