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EARTH SYSTEMS:


THE FOUNDATION OF FLORIDA'S


LO ECOSYSTEMS

ED LANE, PG 141
FRANK RUPERT, PG 149

FLORIDA GEOLOGICAL SURVEY .......... _
1996


INTRODUCTION
ECOLOGY is the study of the relationship between organisms
and their environment, including the study of communities, patterns of
iFe, natural cycles, relationships to each other, biogeography, and
population changes.
An ECOSYSTEM is a community of organisms, including
humans, interacting with one another and the environment in which
they live.
ECOSYSTEMS EXIST IN AN INFINITE VARIETY, and on
many scales, from the microscopic to planet-wide. Therefore, an
ecosystem's boundaries depend on the scope of the study. Most
ecosystems have a d ,er-ityj of animals and plants, all of whicn have a
range of living requirements. Because of this, there is overlap among
adjacent ecosystems.
ECOSYSTEMS ARE NOT STATIC. They change in time
and space, due to both natural and human influences. Shadow lakes,
for example, tend to fill in over time with sediment and plant material;
human activities can accelerate the process. Plant and animal commu-
nities also change as part of the life cycle of an ecosystem.
A knowledge of EARTH SYSTEMS is necessary to
understand how biological and non-biological components
interact to create and sustain ecosystems. The solid earth
aspects of earth systems are included in the science of geology, the
atmospheric components reside with meteoroloqy, and hydrogeology
and hydrologe cover the aqueous parts of our physical earth system.
Basic geologic knowle ge of the physical characteristics o rocks
and geologic processes has direct relevance to ecosystems. ROCKS
ARE THE ULTIMATE SOURCE OF MOST NUTRIENTS IN
rOOD CHAINS. Weathering processes break down rocks into their
constituent minerals and chemical components, forming soils and
nutrients. Erosion and sediment tran-pclt processes then make them
available to the biosphere. Most nutrients are recycled many times
through an ecosystem before losing their usefulness to the system.
The GEOLOGIC STRUCTURE of the stratigraphic
formations of an area's rocks is a major factor in determin-
ing the landforms, or geomorphology, of that area. The
structure and stratigraphy also influence surface and ground-water
conditions, such as flow, recharge and discharge areas, and location
and depth of aquifers and ambient water chemistry. Some geomorphic
features can create very localized microclimates and restricted ecosys-
tems; steephead ravines and sinkholes are two examples.
The accompanying block diagrams are generalized composites
that have been constructed to illustrate the most important topo-
graphic and geologic features of broad areas of the state. They do
not represent all features that occur in specific areas. Vegetation has
been omitted to accentuate the main geomorphic features.
Florida's climate ranges from temperate and sub-tropical in the
north to tropical in the south. This climatic range results in intermingled
plant and animal environments and numerous overlapping ecosystems.
CENOZOIC ROCKS
Florida is underlain by thousands-of-feet of rocks of
Precambrian, Paleozoic, Mesozoic, and Cenozoic age. However, only
rocks of Cenozoic age either crop out at the surface or occur at rela-
tivel9y .h'[llow depths. Figures I and Z show these relationships. Since
these are the only' rocks involved in creating and sustaining Florida's
ecosystems, only the9 \..,II be discussed here.
Cenozoic sediments began to be laid down about 65 million years
ago. Figure I shows the geological units comprising the Cenozoic
strat;grapk;c column in Florida. In general, carbonate rocks (limestone
and dolomite) predominate in the older sediments of the Paleogene,
while siliciclastics (clays, sands, gravels) predominate in the younger
sediments of the Neogene-Quaternary.
Florida's present landscape is the product of sea level fluctua-
tions and associated marine related processes, erosion and deposi-
tional processes. Over the past 2 to 3 million years, as a result of the
repeated growth and melting of continental glaciers, sea levels have
fluctuated from several hundred feet above present level to several
hundred feet below present sea level. The most recent fluctuation is a
slow rise in sea level, causing a retreat of shorelines in many parts of
the state. Siliciclastic sediments were eroded from the Appalachian
Mountains to the north, blanketing the state. Rivers, waves, and cur-
rents created ancient deltas, shorelines, estuaries, dunes and sand
ridges. Subsequent mechanical and chemical erosion and re-deposi-
tion produced Florida's present geomorphology. The more prominent
of the geomorphic features are shown on Figure 5.


WESTERN PANHANDLE


REPRESENTATIVE PLANTS


The western Florida panhandle is under-
lain by thick Miocene to Recent sands and
clays. Carbonates, which are common at shal-
and. and d unce low depth elsewhere in riLi;dnd, en, erWl[[ lie at
depths in excess of +00 feet below land sur-
face. Clags in the thick overburden sediments
shield this limestone from extensive dissolution.
As a result, karst features, such as sinkholes,
are rare to absent in the four counties of the
western panhandle. The thick sands and grav-
elly sands also form the primary drinking water
,I / 1#. aquifer, which due to its lithology, is named the
z) Ab Sand-and-Gravel aquifer.
Extending approximately 50 miles from
the Alabama border on the north to the Gulf
shoreline, the regon is JidJ into two maor
geomorphic zones. Skirting the northern edge
of the western panhandle is a broad, stream-
',- 6 die.::i-ed upland named the Western
SHighlands. South of these highl,knd- is a gen-
eral9 flat and ele ..3tionall[ lower zone named
Sthe Gulf Coastal Lowlands.
r ,, The Western Highlands consist of clajeu-
S sand nill., which attain elevations up to 5 5
feet above sea level (ASL). Surface water fea-
tures consist primarily of deeplg-incised
I/:. Q streams. Plio-Pleistocene clayey, gravelly,
quartz sands of the Citronelle formation form
Sthe core of the nill Nlanketing the Western
-Highlands is a relict, variably thick veneer of marine
terr.-ce sands, deposited by hih-stanJinr, Pliocene
; / ./ A irSd Fleistocene seas. Local ecosystems are controlled
.,,, n raiL5 r1 by the t ,oporaphy and by the lthoelt j and
fBffri r*dr-l,.:'l,[] i.w the undrl in4 geologic formations. Limonite
kh.1-dp.in .nd cdI ay beds, for example, commonly retard down-
v.virj p.i..iti.n in manu areas, causing high _t irJinr;v water

6SnJdg joi l derived from the 1 Itron&lln rh 'rni,-ton and the undif-
ferentiated terrace sands, which have been leached of any contained
1:.11. po%,,f A ). ,w,,l-Jr.:ji d i c'. ordJ ti.mo p.n,-tic.u ki hill top
and L -pc u,:h :,-.,Li tLpi.::il[r .si support uplind -.indhill or pin"e -ic'.-t
e~o.fsltem t I-:.n.s' ,tn rirr -tlJ irr i o I .nle "-i F'ine nflu.L .lril. ,' oi'nce th-e


FIGURE 1: Florida strattgraphic column.


EASTERN PANHANDLE- BIG BEND


The distance from the Georgia-Florida border in the north to the
Gulf of Mexico in the south is about 50 miles. This landscape is natu-
rally divided into two distinct areas by the east-west oriented Cody
Scarp, an ancient shoreline feature which stretches from the western
panhandle almost to Jacksonville. The CodJy Scarp is a prominent fea-
ture that can rise as much as 150 feet in elevation over a mile of hori-
zontal distance. The higher, rolling hills north of the Cody Scarp are in
the Northern Highland geomorphic province, with elevations ranging
from about 500 feet above sea level (ASL) near the Georgia/Florida
border to about 75 feet ASL at thk toe of the scarp. The flat region
that gradually slopes down from the toe of the scarp to sea level at the
Gulf is the Gulf Coastal Lowlands.
The Northern Highlands are underlain by sediments of the
Miocene Hawthorn Group, composed of interbedded quartz sands,
clays, and carbonates. Except for a few areas where they crop out at
the surface, these sediments usually underlie the younger Pliocene
siliciclastic sediments of the Miccosukee formation (reddish-orange
clags, silts, and sands). These heterogeneous sediments form loamy
soils that are rich in nutrients. They support lush, natural vegetation,
and make good farming soils. The rolling hills have been dissected by
stream erosion, creating steep-walled channels in the weakl9 clay-
cemented, sandy sediments. Steepheads are distinctive erosional fea-
tures that result from spring-fed streams eroding headward and etch-
ing narrow, steer ravines. These ravines form isolated environments
that have specialized ecosystems of ferns, other sensitive plants, and
amphibians.
Many large lake basins are the result of dissolution of buried lime-
stone, which has caused slight subsidence of the overlging siliciclastic
sediments. These lakes are only a few feet deep and usually have
extensive marshes or wetlands associated with them. Due to the high
clay content and the thickness of the Hawthorn Group and
Miccosukee Formation sediments, which act as confining units, this
region has low potential for recharge to the groundwater aquifer, the
Floridan aquifer system, which is developed in the underlying lime-
stones.
The upland ecosystems are based on the plant communities that
are supported by the nutrient-rich sediments, and are dependent on
the local stratigraphy and hydrogeology. Important elements in these
ecosystems are the-mixed hardwood and conifer forests, containing
both temperate and subtropical species. Extensive stands of large,
mature hardwoods (oak, maple, beech, hickory, magnolia), conifers
(pine, cedar, cypress), and palms form the foundation and protective
canopy for lush undergrowth. Together, these elements create rich
and varied ecosystems.
The Gulf Coastal Lowlands of the eastern panhandle-big Bend
area are underlain by thick sections of near-surCace carbonate rocks
of oligocene age (Suwannee Limestone) and Miocene age (St. Marks
Formation). These limestones have been deeply weathered by disso-
lution. These limestones also extend to the north under the Northern
Highlands.
Karstification is largely a chemical erosion process that occurs in
carbonate rocks. Because most of Florida is underlain by carbonate


GULP COA$rAL




0 50 MILES
i.
0 80 KM
SCALE

IMMOVLee RiIA
Dia CT!r5S SWAI


SOUTHWESTERN FLORIDA

Southwestern Florida is underlain by oligocene to Recent car- has resulted in a number of J, ffcr,-rl
bonates, sands, clays, and mollusk shell beds. The deeper carbonates the higher sand ridges xeric ecosys
are comprised of porous Suwannee Limestone. Locally, the Suwannee well-drained quartz sands of ancient
Limestone is the uppermost rock unit of the rloridan aquifer stem. These floral communities include xer
Overlying the Suwannee are carbonates and interbedded sands an and typically support various specie
class of the Hawthorn Group. At the eastern edge of the area, clayey, metto.A chain of large karst lakes
gravelly quartz sands of the Pliocene Cy.presshead Formation overie alley, provides a tLp.ii:il sandhill uF
the Hawthorn Group and form the foundation for the elevationally aquatic flora suchas bladderwort, [
higher central ridges. shallow sediments are variably-thick undifferen- narrow u and around each lake. Dr
tiated Plio-Pleistocene sands and shell beds. interspersed with patches of exF
In general, the region is comprised of flat-lying sandy terrain bro- Intraridge Valley between lakes. In so
ken only by the higher elevations of relict, marine-eroded inland ridges blanket portions of the floor of the
running parallel to the axis of the peninsula. Locally, the most promi- The broad, flat Desoto PF'l.n is
nent of these ridges is named the Lake Wales Ridge, which attains ele- Hawthorn Group. Covered only by
vations of 500 feet above sea level (ASL). The core of the Lake Wales sand, the cle l1 Hawthorn ced ment
Ridge is comprised of clayey, gravelly, coarse quartz sands of the water. Because of the lo,w-perme.Al
Pliocene Cypresshead formation. These, in turn, rest on Oligocene to however, many areas of the plain bec
Pliocene si]icilastics and carbonates of the Hawthorn Grouep. The Lake duringthe rainy season. Mesic flatwc
Wales Ridge is split along much of its length by a steep-walIed axial val- th non-agricultural land on the
ley, referred to as the Intraridge valley. This valley probably formed by Lowlands west of the Lake Wales Rid
karst dissolution of the underlying limestone. Numerous large sinkhole th flat, p l condit
lakes extend along the axis of the Intraridge Valley. meto, ow shrubs, and grasses pred
Extending westward from the toe of the Lake Wales Ridge is a Patches of hardwood forest ril
broad, flat, sand, relict submarine plain named the DeSoto Plain. It reaches of the Peace and Mqakka
ranges in elevation from about 80 feet ASL at the toe of the Lake soils the Hawthorn are hallow c
Wales Ridge to about 40 feet ASL at its western boundary, where it exist. Salt marshes are developed wh,
adjoins the Gulf Coastal Lowlands zone. Surface sediments are com- water near the coast. These es" uand
posed largely of marine sands and interbedded shell beds. black needlerush, cordgrass, and
The Gulf Coastal Lowlands extend from the western boundary of 4 r -I,,, e.. .l,,,,- ,. t-, ,., L. H


I


kw-N


pr;n,-ipal upland tree species in prehistoric times, alonr, \ith other F
species, oaks, wiregrasses, herbs, and low woody shrubs.
Interspersed with the sandhll[ ecosystem on the rolling. top.
phY of the Western Highlands, particularl-i along the mailer "tre
courses, are upland hardwood forests and upland mixed fore
Clayey9, organic, sandy sois, developed from the 5hallow-lyirng A
Bluff Group and Cjtror, elle r._rmartc'n, retain more moisture than
deF, sand r revZin3 and support a decJedl! mesic (moist) commun
In these regions the common flora includes m.3aclia, oak, hickc
beech, and various pine species. Bottomland hardwood forests z
lo.pld jir, forests are developed along the major alluvial stream cou
es of the region, where higher water tables and high soil JaIl
organic contn provide mesic conditions. 'oistLire depAenjenft ore
of water and live oak, sweetgum, ktolie., beech, pJmett nd r
birch extend along the upper reaches of the Escambia River Vail
Freshwater tidal swamp occupies the lower, seaward portion of
valley. The southern boundary of the Western Highlands is marked
a reFict marine escarpment which forms a topographic break betw
thke ele.it. ,[n1 i h1i[-ir uplands to the north and the lower, eenr
iiLt Gulf Coastal Lowlands zone to the south.
The Gulf Coastal Lowlands comprise a .indJ, gentlu-seaw
sloping plain e>tnerdinr from the southern edge of the West
Highlands south to the Gulf of Mexico. elevations rise from sea leave
the Gulf coast to about 50 feet ASL at the toe of the West
Hihl.rndc'. The Gulf Coastal Lowlands are characterized by number
-_iFc.t .jrd beach ridges, dunes and sales formed b1j hig--stand
Pleistocene seas. This sandy topography is underlain by gener,
clean quartz sands, creating moderate to poorlyI-drained mesic cor
tions. Pine flatwoods occupy much of the inland portions of the 1c
lands. Near the coast, maritime hammock flora of live oak, cabbk
palm, and redbay occur in discontinuous forests, rooted in the th
quartz sands of old coastal dunes. well developed dunes along
modern coast support a beach dune ecosystem including sea ce
cordgrass, sand spur, and mtl.-rnInw ,lrq. Behind the dunes, espec
I1 on the barrier islands, is a coastal grassland ecosystem. This F
treeless ecosystem is developed on clean sands and t(pi,allyI st
ports only grasses, prostrate vines and other maritime herbacec
flora .