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 Geologic guide to Suwanne River,...


A geologic guide to the Suwannee River, Ichetucknee Springs, O'Leno, and Manatee Springs State Parks ( FGS: Leaflet 12 )
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Permanent Link: http://ufdc.ufl.edu/UF00001180/00001
 Material Information
Title: A geologic guide to the Suwannee River, Ichetucknee Springs, O'Leno, and Manatee Springs State Parks ( FGS: Leaflet 12 )
Series Title: Leaflet
Physical Description: 28 p. : ill., maps ; 23 cm.
Language: English
Creator: Hoenstine, Ronald W
Weissinger, Sheila.
Publisher: Bureau of Geology, Division of Resource Management, Florida Dept. of Natural Resources
Place of Publication: Tallahassee Fla.
Publication Date: 1982
Subjects / Keywords: Geology -- Florida.   ( lcsh )
Parks -- Florida   ( lcsh )
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Source Institution: University of Florida
Rights Management:
The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier: notis - AAA2599
System ID: UF00001180:00001
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Table of Contents
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    Geologic guide to Suwanne River, Ichetucknee Springs...
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Full Text


[year of publication as printed] Florida Geological Survey [source text]

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restricted. Contact the Florida Geological Survey for additional
information and permissions.

Leaflet No. 12


Introduction.................................. ....... ......1

Suwannee River State Park.........................7

Ichetucknee Springs State Park...................13

O'Leno State Park.......................................19

Manatee Springs State Park........................25

On the cover: Limestone outcrop at Suwannee River State Park

Prepared by

Bureau of Geology
Division of Resource Management
Florida Department of Natural Resources




Ronald Hoenstine and Sheila Weissinger


Much of North Central Florida is sparsely
populated and retains the nearly-untouched
beauty of "Original Natural Florida," the
Florida that greeted the early European ex-
plorers. Located in this area of scenic rivers
and sparkling springs are several popular state
parks, including Ichetucknee Springs, Manatee
Springs, O'Leno and Suwannee River.


Much of the area's distinctive beauty is
associated with small and large solution de-
pressions, springs, and disappearing rivers;
topographic features representative of a general
landform designated as karstt" by geologists.
These features develop in limestone regions
having plentiful rainfall. Sinkholes are
numerous in the area, and are conspicuous
features in the parks.


Sinks occur as a result of the dissolution
of limestone by the downward percolation of rain
water. Rain combines with carbon dioxide in the
atmosphere to form carbonic acid. As this aci-

dic rain percolates downward through the soils
it comes into contact and reacts with the under-
lying limestone. The result is dissolution of
the limestone and the formation of cavities. As
the cavities grow with time, the weight of the
overlying sediments may cause collapse and the
subsequent formation of a sinkhole. This pro-
cess of formation may become accelerated in the
future if this pristine area of Florida is sub-
jected to increased amounts of acid rain.
Some of these sinkholes are filled with
water, while others are "dry sinks." While both
groups of sinkholes may have continuity with the
underlying limestone, the dry sinks permit rain
water to percolate completely into the
underlying limestone.


Also associated with this karst terrain are
numerous springs. Florida has long been famous
for its springs. In fact, there are more large
springs in Florida than any otherstate, account-
ing for 27 of the nation's 78 major springs. It
has been calculated that the total output of
water from all of Florida's 300 known springs is
around 8 billion gallons a day.
To more fully appreciate how and why
springs form, one must understand the term
"aquifer." Hydrologists define aquifers as
natural zones below the ground surface that
yield water in quantities that are important
economically. In this part of Florida the
aquifer, which is known as the Floridan Aquifer,
is a thick layer of limestone. This limestone
is divided into formal units called formations.
These formations, which vary in age and litho-
logy (physical characteristics), include the
Suwannee Limestone and limestone of the Ocala
Rocks must have two essential properties to

be considered an aquifer. They must have poro-
sity and permeability. Porosity refers to the
openings in the rocks which have the capacity to
store water. Such openings include cavities,
voids or intergranular spaces. The second pro-
perty, permeability, is equally important as it
refers to the rocks' ability to transmit water
through interconnected pore spaces.
Although highly variable, parts of the
Floridan Aquifer may contain as much as 30 per-
cent open space capable of storing large quan-
tities of water. Furthermore, the aquifer's
permeability permits the movement of vast quan-
tities of water to the surface via springs and
A spring occurs when groundwater from the
aquifer is discharged as natural seepage or
freeflow through an opening at the ground sur-
face. The volume of water discharged may be
small and form a trickle, or large enough to
form a river, such as the Ichetucknee River.
The volume discharged frequently varies, as it
is dependent not only on porosity and per-
meability but other factors such as seasonal
rainfall that recharges the aquifer, and pum-
page, which depletes it.

An age (time of deposition) of about 30
million years before the present, during a
period of time known as the Oligocene Epoch, can
be assigned to the limestone and dolomite which
crop out in the Suwannee River State Park. An
age of about 40 million years before the present
(Late Eocene Epoch) can be assigned to the lime-
stone occurring at the surface in the vicinity
of Manatee Springs, Ichetucknee and O'Leno state
How do geologists determine the age of
these rocks? A casual glance at the limestone

exposed in these parks reveals the presence of
marine fossils such as clams and oysters, while
a closer microscopic inspection reveals numerous
microfossils. Microfossils are the remains of
tiny plants and animals that lived long ago.
These organisms include, among others, the
silicabearing plants called diatoms, calcareous
marine algae known as coccoliths, and calcareous
one-celled animals known as foramini-fera. The
presence of microfossils in rocks serves as an
important tool for various scientific groups,
such as the Florida Bureau of Geology, in pro-
viding data for the dating of Florida's sedimen-
tary rocks.
Essential to the study of microfossils is
the accepted principle that various species of
plants and animals lived and died during certain
periods of Earth's history. Therefore, the
identification of these species, together with a
knowledge of their life span, permits one to
date the sediments in which they are found.


Microfossils' small size, wide geographic
occurrence, and abundance in sediments of all
ages and diverse environments are charac-
teristics that make them invaluable for the pur-
pose of identifying ancient depositional en-
vironments. Specifically, microfossils can be
important indicators of the water depths, tem-
perature, salinity, and water currents that
existed at the time the sediments were formed.
For this reason, the utilization of microfossils
has been of special importance in the study of
Florida's past and in identifying the deposi-
tional environments that existed in the area of
the four parks 30 to 40 million years ago.
By comparing these microfossils with living
relatives, we know that the sediments present in
these parks were formed in a relatively shallow

marine environment. In other words, the lime-
stone you see in the parks was once covered by a
shallow sea. The period of time when the
Florida peninsula was underwater represents most
of the last 200 million years of geologic his-
The importance of microfossils to the study
of Florida's past can be further illustrated by
comparing the past environment of Florida to
that of much of the rest of North America during
the Cretaceous, a period of time that ended
approximately 65 million years ago. During this
period, when dinosaurs roamed much of North
America, these parks, and indeed most of
Florida, were underwater. This explains the
absence of dinosaur remains in Florida.
We hope this geologic guide will serve to
enhance your enjoyment and appreciation of the
beautiful and distinctive state parks of the
Suwannee River Basin.



0 1000




The confluence of the Withlachoochee and
Suwannee rivers offers a unique and historic
setting for the Suwannee River State Park.
Visitors to the park are impressed with the
quiet natural beauty of the rivers and the
surrounding wooded uplands. Situated in the
physiographic zone known as the Coastal Low-
lands, the park's elevation ranges from a low
of 40 feet above MSL (mean sea level) near the
river to a maximum of 70 feet MSL near the
eastern boundary of the park.


Originating in the Okefenokee Swamp of
southeast Georgia, the Suwannee River winds
through north central Florida past the park,
continuing its journey to the Gulf of Mexico,
its final destination. Similarly, the Withla-
coochee River originates in south Georgia and
flows southward to merge with the Suwannee River
at the park, where this confluence of the two
rivers can be viewed from a rustic overlook (see
map). The distinct differences in sediment
loads of the rivers can be observed from this
vantage point. The light brown waters of the
Withlacoochee are laden with suspended silts and
clays which give the river a muddy appearance.
In contrast, the Suwannee River is relatively
free of suspended sediment. Its dark, brownish-
black color is a result of high tannic acid con-
tent. This tannic acid is produced by decayed

View of Suwannee River


The Confluence of the Withlacoochee and Suwannee rivers.

organic matter which washes into the river from
forests and swamps that line the shore.
As the rivers flow southward they wind, or
meander, resulting in rock and soil material
being eroded from the outside and downstream
side of river bends, while material is deposited
on the inside and upstream side. You can
observe this effect as you hike along the river


The effects of river erosion are evident in
the park. As you walk southward along the river
towards the earthworks and the overlook or
northward along the river side of the Suwannee
River Trail, you can observe limestone and dolo-
mite outcrops on the south side of the river.
The river has eroded the overlying sediments to
expose these aged and weathered rocks.
These limestones, which are part of the
Suwannee Limestone, were deposited during
Oligocene time (30 million years before the
present). Through time, much of the limestone
has experienced substantial dolomitization.
This process occurs when limestone, composed of
the mineral calcite (a calcium carbonate), be-
comes a different mineral, dolomite, through the
substitution of magnesium for calcium. As a
result the rock, which in its original state was
porous and permeable, may become dense and
impermeable. In addition, fossils usually
become distorted or completely obliterated
through this process of dolomitization. A close
examination will reveal fossil shells, molds and
worm borings exhibiting all degrees of pre-
servation. West of the overlook is a prominent

exposure of dolomite and limestone which,
depending on the river stage, can measure more
than 15 feet in height.


Walking along the Suwannee River Trail one
can not only observe limestone outcrops but also
see low banks parallel to the river on the
eastern side of the trail (see map). These low
ridges, called natural levees, are formed as a
result of the river flooding. As the river
overflows its banks, an abrupt decrease in both
water velocity and turbulence occurs, resulting
in the deposit of the coarser particles of the
suspended sediments. In time, these coarse
deposits form ridges, or levees, which generally
parallel the river's edge.


The Sandhills Trail leads from the hardwood
hammock along the river to the open forest of
pines. Approximately 500 feet down the trail
one can see several dry sinks on the northeast
side (see map). These geological features,
which have a diameter of approximately 20 feet
and a depth of 10 feet, are collapsed limestone
cavities (see "sinks", page 2).
The trail continues to the Old Columbus
Cemetery. The town of Columbus has long since
disappeared, but some of its history remains on
the weathered tombstones. One can see the
results of weathering (especially the corrosive
action of rain) on both the metal and stone
markers. The once clearly legible monuments are
now smooth due to the effects of rain and abra-

sion from wind-blown sediments over a relatively
short period of time. Imagine the effects of
weathering on Florida's landscape over a period
of millions of years.

Dry sink along Sand Hills Trail



0 2000

ss Troil



South of Suwannee River State Park, strad,-
dling the Suwannee-Columbia county line, .is
Ichetucknee Springs State Park, one of the most
beautiful and popular parks in Florida. For
many people its refreshing springs represent a
cool oasis during the hot summer months. Eleva-
tions range from 25 feet MSL near the river to a
maximum of 60 feet MSL in the western part of
the park.
The surrounding area has many features
typical of a karst area. These include wet and
dry sinks and numerous springs.


Within the 2,241 acres that make up the
park and along the upper reaches of the
Ichetucknee River are nine named and many
unnamed springs. The most northern spring is
Ichetucknee Spring which forms the headwaters of
the river. Nearby is Blue Hole Spring, which
can be reached by a trail and boardwalk from the
main park.
Ichetucknee Spring is 75 feet wide and 105
feet long, and has a maximum depth of 14 feet.
The spring has an average water temperature of
73oF and discharges 30 million gallons of water
a day (based on measurements taken in 1975 by
the U.S. Geological Survey).
The trail just north of Ichetucknee Springs
leads to Blue Hole (Jug) Spring (see map). This
secluded spring with its crystal clear, blue

waters is a favorite swimming site in the park.
The spring is 85 feet wide, 125 feet long, and
has a maximum depth of 37 feet at its north
central end near the vent. The boil, which is
clearly visible near the center of the pool, has
a measured flow of 60 million gallons a day.

View of Ichetucknee Spring and spring run


The spring's waters issue directly from the
limestone aquifer. The exposed limestone which
forms part of the aquifer in this park is the
Ocala Group limestone of Eocene age. These
limestones, which are approximately 40 million
years old, contrast with rocks cropping out in
the Suwannee River State Park in that the ex-
posed limestones there are the Suwannee Lime-
stone of Oligocene age (approximately 30 million
years before the present). Thus, as we have
come southward, we have taken a 10 to 15 million
year journey back in time. The missing,
younger, Suwannee Limestone, which would ordi-
narily overlie the Ocala limestones, was either
never deposited here or was completely eroded
over time.

'-^ '-t rr s *~ -


Limestone outcrop along Blue Hole Access Trail

These limestones offer further contrast to
those in Suwannee River State Park in that
little dolomitization can be observed here.
Because these rocks are primarily limestone
(calcium carbonate), the fossils show better
preservation. However, the calcium carbonate
content of these rocks causes them to be more
susceptible to dissolution by acidic rain.
Similar to the limestone exposed at Suwannee
River State Park, these limestones, though much
older, also once formed the bottom of an
ancient, shallow sea.


A walk along the clearly marked Trestle
Point Nature Trail leads the visitor through
hardwoods and pines that line the river (see
map). Limestone outcrops of the Ocala Group can
be seen along this trail at the river's edge.
Directly across from Trestle Point you can see a
tunnel formed by dissolution of the limestone.
Other dissolution features observed along the
river bank include cavities and irregular voids,
many of which resemble caves and columns. These
surface structures are very similar to features
occurring in the limestone subsurface.
Farther down the trail you can see a large,
circular depression approximately 60 feet to
the left of the trail. This depression is a dry
sink which formed through dissolution of the
underlying limestone by rain water. Several
additional sinks similar to this one can be
observed within the park boundaries.

Continuing along the trail you will come to
an overlook. This overlook permits you to see
the remnants of an old hard rock phosphate mine
which was being actively mined in the early
1900's. Note the trees' position and orien-
tation with respect to the sloping sides. The
distortion in their growing position is due to a
process known as "soil creep." This process
occurs as a result of gravity causing the slow,
downhill movement of poorly-consolidated sedi-
ments, such as sands, that are present here.
This movement, though very slow, has noticeable
effects over time.
The closest active phosphate mining today
occurs in Hamilton County at a site approxi-
mately 40 miles north of the park. Phosphate
represents one of Florida's greatest mineral
resources and production in Florida exceeds that
of any other state.


' .^ C''s^ -
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Soil bank erosional features at Trestle Point

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Quarry "'
)x Sink

0 500







A short drive south from Ichetucknee
Springs State Park brings you to O'Leno State
Park, located on the peaceful Santa Fe River.
This interesting, scenic park has a general
topography much like that of Ichetucknee, with
numerous wet and dry sinks and limestone ex-
posures. Elevations within its boundaries vary
from a low of about 40 feet MSL to a maximum of
approximately 79 feet MSL at the park's north-
western border.


The Santa Fe River is fed by many springs
and tributaries, including the Ichetucknee
River, which joins the Santa Fe after a brief
5-1/2 mile journey from its headwaters. In
contrast to the crystal clear Ichetucknee River,
the waters of the Santa Fe are stained dark by
tannic acid. The river's surface reflects like
a mirror the luxuriant vegetation along the

A suspension bridge, built in the 1930's by
the Civilian Conservation Corps, spans the river
at the main park (see map). Below it is a small
rapid, created when local dolomitic limestones
were placed there as part of the construction of
a mill that once stood on this site. Many
limestone outcrops occur along the river and
park trails.

The suspension bridge spanning the Santa Fe River.





Located to the left just past the park's
entrance is the Limestone Trail (see map). This
forest trail, which can be traveled in a
leisurely 20-minute walk, presents the oppor-
tunity to observe numerous limestone boulders
and are approximately 40 million years old,
about the same age as those found in Ichetucknee
Springs State Park to the north. In addition,
one can observe an abandoned limestone quarry at
the trail's overlook located on the northeastern
side of the trail. Note the prominent limestone
outcrop clearly visible at the south end of the
quarry. Large quantities of limestone were
mined from this now-inactive quarry for use in
the construction of fireplace chimneys.
As you continue your walk, you will see a
large sinkhole to your left on the western side
of the trail.

t-" (-' r ;;`t xrvP


From the main park and just across the
suspension bridge, one comes to the River Nature
Trail (see map). This picturesque trail leads
through lowland hardwoods and sandy pine forests
within the river's flood plain. Several fea-
tures of geologic interest can be observed along
the way.
Approximately 1,500 feet down the trail is
a long, narrow lake. The water in this lake,
which has direct access to the aquifer, fluc-
tuates in response to groundwater levels.


View of fake located on north side of River Nature Trail (water level responds
directly to fluctuations in underlying aquifer).

.,: X 7-

The next geologic feature of interest is
the River Sink, which is located at the eastern
end of the trail. It is here, observable from
several vantage points, that the Santa Fe River
disappears and flows underground for more than 3
miles before it again becomes a surface stream.
The waters of the river are literally "swallowed
up" by vertical, 100 foot deep conduits. These
conduits channel the water downward into the
subsurface limestones where the water travels
laterally for several miles through cavities
before reappearing at the surface. Such a phe-
nomenon, creating what is known as a natural
bridge, is not unusual in these regions of
springs and sinks.
As you leave River Sink you can see on the
southern side of the trail, a large, shallow
depression. Clearly marked with a park sign,
this depression is a dry sink.

River Sink





iwet sinks



Manatee Springs is situated in a lush,
semitropical, hardwood hammock just 23 miles
northeast of the Gulf of Mexico. In addition to
providing many recreational activities, the park
contains excellent examples of karst landforms.
The park is located in the physiographic
zone known as the Coastal Lowlands, with eleva-
tions ranging from a low of near mean sea level
at the river to a high of 25 feet above MSL in
the park's interior. The area is rich in
history, for these springs were known and
visited for centuries by the Indians and early
Spanish explorers. Today, thousands of tourists
come to enjoy the sparkling, clear waters and
tranquil surroundings. In the winter its name-
sake, the endangered Florida manatee, sometimes
visits the springs to enjoy its constant 72F


The spring head, which is located 1,200
feet from the Suwannee River, discharges 4.8
million gallons of water per hour. The water
issues from rock which is part of the Ocala
Group limestone, the same limestone formation
that is found in O'Leno and Ichetucknee Springs
state parks to the north. These rocks, which
can be observed as outcrops around the pool's
perimeter, are approximately 40 million years
An excellent view of the spring run can be


enjoyed from a boardwalk that leads from the
boat launching area to the Suwannee River. Much
of what may be seen as you walk along this
boardwalk is similar to what was reported by
William Bartram, a naturalist, in his visit to
the spring in 1774. On this visit, he observed
alligators, gar, catfish, mullet, trout, bream,
pike and "the monstrous amphibious maneta
(manatee)". He also noted great quantities of
shells and shell fragments in and around the
A large underwater cave system extends
2,000 feet from the main spring. Scuba diving
in these caves is very popular, but dangerous,
and safety is emphasized by park personnel.

View of the boil and spring run


The Nature Trail begins at a point approxi-
mately one mile from the entrance station, just
east of the camping area. This clearly marked
trail leaves the main road and winds through a
dense hardwood hammock toward the southeast.
Visible on both sides of the trail are de-
pressions, or sinks, of varying sizes and stages
of development. Of particular interest is a
series of three wet sinks located near the
trail's end. Two of the sinks are connected by
a narrow landbridge. This connecting bridge is
underlain by rocks which have not experienced
dissolution and subsequent collapse. In the
future, the adjoining sinks may enlarge, engulf-
ing the bridge.
Two much larger sinks can be observed in
the nearby camping area (see map). These sinks,
which are filled with water, are connected via a
network of underground solution channels to the
main springs.

------ ------- .. `-.,:. .,

Information markers throughout the parks provide visitors with trail guides
and descriptions of special features.

Two of the sinks are connected by a narrow
landbridge. This connecting bridge is underlain
by rocks which have not experienced dissolution
and subsequent collapse. In the future, the
adjoining sinks may enlarge, engulfing the

One of several wet sinks located along the Sink Trail.