BULLETIN NO. 68


APPENDIX 2. EXPLANATION OF REVISIONS TO FDEP-FGS SPECIAL
 PUBLICATION 28 AQUIFER DEFINITIONS

 Changes to original Southeastern Geological Society (1986) text are denoted by brackets (additions)
and strikethroughs to reflect definitions applied in this report. Footnotes provide explanation.

surficial aquifer system: the permeable hydrogeologic unit contiguous with land surface that is
comprised principally of unconsolidated to poorly indurated [silici]clastic deposits. It also includes well-
indurated carbonate rocks [and sediments], other than those of the [FAS] Floridan aquifer system where
the Floridan is at or near land surface. Rocks [and sediments] making up the [SAS] surfieial- aquifer
system belong to all or part of the upper7 Miocene to Holocene Series. [The SAS] it contains the water
table and water within it is under mainly unconfined conditions; [however,] but beds of low permeability
may cause semi-confined or locally confined conditions to prevail in its deeper parts. The lower limit of
the [SAS] surficial aquifer system coincides with the top of laterally extensive and vertically persistent
beds of much lower permeability."8

intermediate aquifer system or the intermediate confining unit: "- includes all rocks that lie between
and collectively retard the exchange of water between the overlying [SAS] sufficial aquifer system [(or
land surface)]9 and the underlying [FAS] Floridan aquifer system. These rocks in general consist of
[coarse to] fine grained [silici]clastic deposits interlayered with carbonate strata belonging to all-er parts
of the [Oligocene] Miceene1 and younger S[s]eries. [Section omitted.11] The aquifers within this system
contain water under [semi-confined to] confined conditions. The top of the intermediate aquifer system
or the intermediate confining unit [IAS/ICU] coincides with the base of the [SAS] surficial aquifer system
[and on a local scale with land surface]. The base of the [IAS/ICU] intermediate aquifer is at [is
hydraulically separated to a significant degree from] the top of the [FAS]12 vertically persistent permeable
carbonate section that comprises the Floridan aquifer system, or, in other words, that place in the section
where plastic layers of significant thickness and permeable carbonate rocks are dominant. [Section
omitted.1]."

Floridan aquifer system: "- [a] thick [predominantly] carbonate sequence [that] which includes all or
part of the Paleocene to early [Lower] Miocene Series and functions regionally as a water-yielding
hydraulic unit. Where overlain by [the IAS/ICU] either the intermediate aquifer system or the
intermediate confining unit, the [FAS] Floridan contains water under confined conditions. When overlain
directly by the [SAS] surficial aquifer system, the [FAS] may or may not contain water under confined
conditions depending on the extent of low permeability material [within the base of] hi the [SAS] suffieial
aquifer system. Where the carbonate rocks crop out [or are covered by a veneer of siliciclastics], the
[FAS] Floridan 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] Florida aquifer system is present throughout the State and is the deepest part of
the active groundwater flow system on mainland Florida. The top of the [FAS] aquifer system generally


Although aquifer systems are based on hydraulic properties, correspondence with age does exist; "upper" is deleted
to allow more flexibility with regard to this correlation.
8 Second paragraph describing SAS in Southeastern Geological Society (1986) is omitted.
9 For example, the Peace River Formation is locally exposed at land surface in Polk County.
10 Now recognized as Late Oligocene based on the work of Scott et al. (1994).
" Related nomenclatural issues pertaining to the IAS/ICU are being addressed by the CFHUD II.
12 The lower extent of the IAS/ICU in the present study is also based on the relative degree of hydraulic separation
from the FAS.
13 Related nomenclatural issues pertaining to the IAS/ICU are being addressed by the CFHUD II.