FLORIDA GEOLOGICAL SURVEY


of the inferred "offsets" in his study are due to
wells having encountered buried karst pinnacles
and paleo-sinks. Carr and Alverson (1959),
Pride et al. (1966), and Vernon (1951) report a
northwest trending normal fault(s) in
northwestern Polk County (fault group "FG-1",
Figure 3). Pride et al. (1966) suggest that the
fault affects not only the Avon Park Formation,
but also juxtaposes the Suwannee Limestone and
Ocala Limestone. Carr and Alverson (1959)
indicate that the fault penetrates Hawthorn
Group sediments as well. Both studies report
the northeast block of the inferred fault as the
upthrown side. In the present study, evidence
supports two possible northwest-trending faults
along the northeastern extent of the Suwannee
Limestone (Figure 3; see also Suwannee
Limestone, p. 37). Both faults are similar in
strike and offset direction (polarity) to fault
group "FG-1" in Figure 3. One of the offsets
proposed herein is a northwestern extension of a
fault proposed by Carr and Alverson (1959).

 Faults affecting Middle and Upper Eocene
(e.g., Avon Park Formation and Ocala
Limestone) strata are proposed along the Polk-
Osceola County boundary (Pride et al., 1966;
Miller, 1986). The Kissimmee Faulted Flexure
(Vernon, 1951; "E" in Figure 3) occurs in the
same area and was originally considered a
wedge-shaped, fault-bounded block that had
been tilted and rotated, with beds containing
small folds and structural irregularities. Wells
that penetrate the feature contain variably thick
Pliocene-Miocene sediments that overly the
Avon Park Formation. Scott (1988) and Davis
et al., (2001) consider the Kissimmee Faulted
Flexure to be an Avon Park Formation
stratigraphic high with the Ocala Limestone and
Hawthorn Group sediments locally absent due to
erosion. Additional faults ("FG-2" in Figure 3)
affecting the subcrop extent of the Ocala
Limestone along the western margin of the
Flexure have also been proposed. Data
presented in this study support the
interpretations of Scott (1988) and Davis et al.,
(2001).

 Further to the south in the vicinity of
Charlotte Harbor, a west-northwest trending
reverse fault penetrating a dolostone layer in the
Suwannee Limestone is proposed (Hutchinson,


1991). Maps presented herein do not lend
support to the inferred reverse fault. In the same
area, a series of northeast-trending lineaments
along the northern margin of Charlotte Harbor
(Michael Fies, personal communication, 2007)
coincide with anomalously high groundwater
temperatures in the upper FAS (Smith and
Griffin, 1977) suggesting a potential line of
further investigation (E. Richardson, written
communication, May, 2006). The "North Port
Fault" (Winston, 1996) strikes nearly coast-
parallel (northwest) across North Port and Punta
Gorda. Winston (1996) suggests that the
downthrown side may occur on the southwest
block, which more or less coincides with
thickening and deepening of several units
mapped in the present study (see
Il,,i,,ibvs,,!hy, p. 30, for further discussion).
South of the study area, west-northwest trending
normal and reverse faults offsetting Miocene
Hawthorn Group sediments on the order of 50 to
100 ft (15 to 30.5 m; vertical) are reported
(Sproul et al., 1972).

 Evidence of some degree of vertical offset is
present within cores in the study area; however,
there is insufficient proximal well control to
delineate faulting. Core from W-16913 (ROMP
5), for example, contains abundant high-angle
fractures and slickensides that make some
lithostratigraphic unit surfaces obscure.
Regarding hydrostratigraphic units, brecciated
and fractured zones in core from W-17392
(ROMP 13) contribute to difficulties correlating
the Middle Floridan confining unit. These are
only two of many examples of fractured
intervals encountered during data collection that
warrant further structural study.

 Small irregular surfaces in Miocene and older
lithostratigraphic units in the southern part of the
study area raise many questions regarding the
prevalence of structural deformation within
Florida's relatively young carbonate platform.
Missimer and Maliva (2004) suggest that
observed disturbances in lithostratigraphic
surfaces throughout Florida are due to
"differential subsidence by tensional basement
displacement." Their conclusions are based on
seismic surveys and borehole data attained from
areas of variable formation depths. Charlotte
and Lee Counties are among the most widely