FLORIDA GEOLOGICAL SURVEY


 In this report, nomenclature and definitions
of units are primarily based on that proposed by
the "Ad Hoc Committee on Florida
Hydrostratigraphic Unit Definitions"
Southeastern Geological Society, 1986). A 2nd
Ad Hoc Committee on Florida
Hydrostratigraphic Unit Definitions (CFHUD II)
is presently convened to address identified
concerns regarding existing nomenclature and
definitions (Copeland et al., in review). The
CFHUD II is comprised of representatives from
the FDEP-FGS, USGS, water management
districts and consulting firms. Appendix 1
includes a commentary on nomenclatural issues
with regard to Florida's hydrostratigraphy.

 The present study adopts the following
aquifer-system names and definitions, which are
minor revisions of the widely accepted, yet
dated Southeastern Geological Society (1986)
proposal. These definitions are revised in the
context of statewide application, and not limited
to the study area. Appendix 2 provides
explanation of changes from original
Southeastern Geological Society (1986)
definitions.

 surficial aquifer system the permeable
 hydrogeologic unit contiguous with land
 surface that is comprised principally of
 unconsolidated to poorly indurated
 siliciclastic deposits. It also includes
 carbonate rocks and sediments, other than
 those of the FAS where the Floridan is at
 or near land surface. Rocks and sediments
 making up the SAS belong to all or part of
 the Miocene to Holocene Series. The SAS
 contains the water table and water within it
 is under mainly unconfined conditions;
 however, beds of low permeability may
 cause semi-confined or locally confined
 conditions to prevail in its deeper parts.
 Locally perched water-table conditions
 occur as well. The lower limit of the SAS
 coincides with the top of laterally
 extensive and vertically persistent beds of
 much lower permeability.

 intermediate aquifer system/
 intermediate confining unit includes all
 rocks that lie between and collectively
 retard the exchange of water between the


 overlying SAS (or land surface) and the
 underlying FAS. These rocks in general
 consist of coarse-to-fine-grained
 siliciclastic deposits interlayered with
 carbonate strata belonging to parts of the
 Oligocene and younger series. The
 aquifers within this system contain water
 under semi-confined to confined
 conditions. The top of the IAS/ICU
 coincides with the base of the SAS and on
 a local scale with land surface. The base
 of the IAS/ICU is hydraulically separated
 to a significant degree from the top of the
 FAS.

 Floridan aquifer system a thick,
 predominantly carbonate sequence that
 includes all or part of the Paleocene to
 Lower Miocene Series and functions
 regionally as a water-yielding hydraulic
 unit. Where overlain by the IAS/ICU, the
 FAS contains water under confined
 conditions. When overlain directly by the
 SAS, the FAS may or may not contain
 water under confined conditions
 depending on the extent of low
 permeability material within the base of
 the SAS. Where the carbonate rocks crop
 out or are covered by a veneer of
 permeable siliciclastics, the FAS generally
 contains water under unconfined
 conditions near the top of the aquifer
 system, but because of vertical variations
 in permeability, deeper zones may contain
 water under confined conditions. The
 FAS is present throughout the State and is
 the deepest part of the active groundwater
 flow system on mainland Florida. The top
 of the FAS generally coincides with the
 absence of significant thicknesses of
 siliciclastics from the section and with the
 top of the vertically persistent permeable
 carbonate section.

 Generalized correlations between
hydrostratigraphic units and lithostratigraphic
units mapped in this study are presented in Table
2. The H,,,iiuIn,,,gIlh' section, p. 52, of this
report provides a more detailed discussion of
these aquifer systems. Delineation of aquifer-
system boundaries is described in Methods, p.
20.