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Lakes
Trout & Pike
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Subsurface
Characterization
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Seismic
profiles from Trout Lake and Pike Lake show a hard bottom
reflection, possibly well sorted sands, infilling a deeper
karst surface (type 1, A-A).
The strong bottom reflection leads to multiples seen throughout
the data that obscure some of the record. The record is
also partially obscured in areas where the lake bottom
nears the surface. The acoustic characteristics and their
interpretation in the two lakes are similar. The subsurface
is characterized by numerous small low-angle reflections
with high angle reflections dipping toward their center
(A-A, B-B,
C-C, type
4). Concentric reflections extend to depth in the profile.
These features may represent solution pipes or small subsidence
into the karst subsurface, which is in close proximity
to the surface in this area. This condition has a high
potential for increased leakage. A distribution plot of
these features (red
line) shows how they tend to define the areas of deeper
water in the lakes (blue
line). The areas of subsidence seen within the lakes
are well constrained and do not have the appearance of
large subsidence or collapse sinkholes seen in other lakes.
These localized areas of subsidence may lie directly over
centers of active karst development. The competent overburden
restricts lateral growth of the unstable region, confining
dissolution, yet creating a direct conduit for fluid migration
from the surficial waters to the Floridan aquifer. Discrete
reflections at 18 m (B-B,
green line) and 24 m (C-C,
green line) may represent a karst surface on top of the
Ocala Limestone. Interpretations of a gamma log acquired
from a well located approximately 1 mile to the south
of the lakes (Index
Map G, well L-0677)
show the top of the Ocala Limestone to be around 50 m
(15 ft) NGVD, or about 10 m (30 ft) below lake level.
The reflection seen in the profiles (green dashed line)
may be associated with this surface. Differential dissolution
in the Ocala Limestone could lead to subsequent subsidence
in the overlying sediments of the Hawthorn Group and the
undifferentiated fill.
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