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Environmental geology series, Orlando sheet ( FGS: Map series 85 )
CITATION SEARCH THUMBNAILS MAP IMAGE ZOOMABLE
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Permanent Link: http://ufdc.ufl.edu/UF90000337/00001
 Material Information
Title: Environmental geology series, Orlando sheet ( FGS: Map series 85 )
Series Title: ( FGS: Map series 85 )
Uncontrolled: Orlando sheet
Physical Description: 1 map : col. ; 47 x 81 cm.
Language: English
Creator: Scott, Thomas M
Publisher: Bureau of Geology
Place of Publication: Tallahassee
Publication Date: 1978
 Subjects
Subjects / Keywords: Geology -- Maps -- Florida -- Orlando Region   ( lcsh )
Geology -- Maps -- Florida   ( lcsh )
Land use -- Maps -- Florida   ( lcsh )
Geology -- 1:250,000 -- Florida -- Orlando Region -- 1978   ( local )
Geology -- 1:250,000 -- Florida -- 1978   ( local )
Land use -- 1:250,000 -- Florida -- 1978   ( local )
Geology -- 1:250,000 -- Florida -- Orlando Region -- 1978   ( local )
Geology -- 1:250,000 -- Orlando Region (Fla.) -- 1978   ( local )
Geology -- 1:250,000 -- Florida -- 1978   ( local )
Land use -- 1:250,000 -- Florida -- 1978   ( local )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
single map   ( marcgt )
indexed   ( marcgt )
Maps   ( lcsh )
Spatial Coverage: United States of America -- Florida -- Orange County -- Orlando
 Notes
Statement of Responsibility: Thomas M. Scott, Florida Department of Natural Resources, Division of Resource Management; Bureau of Geology.
Bibliography: Includes bibliographical references.
General Note: Relief shown by contours and spot heights. Depths shown by bathymetric isolines.
General Note: Includes location diagram/sheet index, and sectionized township diagram.
General Note: Text, 3 cross sections, and location map on verso.
Funding: Map series (Florida. Bureau of Geology) ;
 Record Information
Source Institution: University of Florida
Holding Location: George A. Smathers Libraries, 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: aleph - 001819322
oclc - 06133611
notis - AJP3306
System ID: UF90000337:00001

Full Text



FLORIDA DEPARTMENT OF NATURAL RESOURCES
BUREAU OF GEOLOGY


MAP SERIES NO. 85


ENVIRONMENTAL GEOLOGY SERIES


ORLANDO SHEET


By
Thomas M. Scott
FLORIDA DEPARTMENT OF NATURAL RESOURCES
DIVISION OF RESOURCE MANAGEMENT
BUREAU OF GEOLOGY

Tallahassee
1978


ORLANDO
REGIONAL SETTING

The study area is located in east central peninsular Florida, east and
southeast of the crest of the Ocala uplift or Ocala high. It encompasses
various structural features proposed by Vernon (1951) including the Osceola
Low, the Kissimmee Faulted Flexure and the Sanford High. The area is
underlain by extensive deposits of Eocene limestone covered by younger
dolomites, limestones, sands, clays and shell beds. Dissolution of limestone
and marine processes are the predominant forces responsible for the development
of the surface features found in the map area.
Two major generalized physiographic divisions occur within the map
area. As named by Puri and Vernon (1964), they are the Central Highlands
and the Coastal Lowlands. The Central Highlands form approximately the
western one-third of the map area while the remaining two-thirds are the
Coastal Lowlands. The highland area includes such physiographic features as
the Marion, Sumter and Lake Uplands; the Mount Dora, Lake Wales, Winter
Haven and Lakeland Ridges; and the Central Valley. The Coastal Lowlands
are comprised of features such as the Eastern Valley, St. Johns River Offset,
Deland Ridge, Atlantic Coastal Ridge, Geneva Hill, the Osceola Plain, and
various lagoons and chains of barrier islands.
Location and Extent-The map area is bounded on the east by the
Atlantie Ocean and on the west by the longitudinal meridian of 82 west.
The northern boundary is the parallel of latitude 29 north while the
southern boundary is the parallel of 280 north latitude. The counties
shown on the map either in their entirety or partially are Brevard, Lake,
Marion, Orange, Osceola, Polk, Seminole, Sumter and Volusia. Major rivers
of the area include the St. Johns, Oklawaha, Kissimmee, and the Big and
Little Econlockhatchee Rivers. The area included on the map totals approxi-
mately 5,900 square miles.
Population and Development-The map area covers approximately 5,900.
square miles with an average population density of 200 people per square mile
(based on 1970 estimates). However, much of the total population is concen-
trated near the major cities of the region. The 1970 census reveals the following
population by county: Brevard, 230,006 with 85% urban; Lake, 69,305 with
43.4% urban; Marion, 69,030 with 40.4% urban; Orange, 344,311 with 83.2%
urban; Osceola, 25,267 with 48.1% urban; Polk, 227,222 with 60% urban;
Seminole, 83,692 with 62.1% urban; Sumter, 14,839 with no urban; Volusia,
169,487 with 70.4% urban. A comparison of the 1960 census and the 1970
census gives the growth rates for each county. The rates, from greatest
increase to least increase, are as follows: Brevard 106%; Osceola, 52.9%;
Seminole, 52.3%; Marion, 33.7%; Orange, 30.6%; Sumter, 25%; Lake, 20.8%;
Volusia, 20%.
The largest cities of the map area are: Orlando, 99,006; Lakeland,
41,550; Melbourne, 40,236; Titusvilie, 30,515; Sanford, 17,393; Cocoa, 16,110;
Leesburg, 11,869; Deland, 11,641; New Smyrna, 10,580; Kissimmee, 7,119.
Only one state university is located in the map area. Florida Technologi-
cal University, located east of Orlando in Orange County, opened in 1968 and
by 1974 had an enrollment of 10,589.
Industry and Transportation-The industry of the area is quite varied,
ranging from tourism to extensive agricultural interest. Tourism is one
of the greatest factors influencing the area's economy. Area attractions
such as Disney World, Kennedy Space Center, and the many beaches draw
numerous vacationers. Agriculture is another important economic factor
with citrus being the most important product. This area constitutes one of
the major citrus producing areas of the United States, utilizing nearly 840,000
acres for citrus crops in 1970. Truck farming and cattle provide other major
important economic resources for the region. Truck crops grown extensively
in this region include tomatoes, sweet corn, peppers, beans, celery, lettuce,
cucumbers, watermelons, potatoes and strawberries. Large truck farms are
located around Lake Apopka and in Seminole County near Lake Jessup and
Oveido.
Quarrying and mine operations also occur, with phosphate being the
most economically important product. Limestone, coquina, shell material,
sand, and clayey sands are also actively mined, most of the material being
used in road construction and maintenance.
Numerous major highways traverse the area. These include the north-
south coastal routes 1-95 and U.S. 1, the north-south central routes U.S. 441,
U.S. 27, U.S. 17 and U.S. 92, the cross state 1-4 and the Sunshine State
Parkway. Many other state highways occur with the most prominent being
Florida 50 running east-west from coast-to-coast.
Commercial airlines provide regular service to the larger cities such as
Orlando and Lakeland and there are numerous small airports serving the smaller
cities and rural areas. Most of the cities, towns, and rural communities are
also served by bus lines and railroads.
I Climate-The average annual temperature for the area is approximately
720F (340C), with August as the hottest month, having an average of 820F
(38.70C) and January as the coldest month, having an average of 61 F (28.70C).
The annual precipitation fluctuates from year to year but averages between 50
inches (127.0 cm) and 55 inches (139.1 cm).
GEOLOGIC DISCUSSION
The surface and near-surface deposits of east central Florida range
from unconsolidated sands to well indurated limestones and dolomites. Seven
lithologic units are recognized for the purpose of surface mapping and cross
section construction in this area. They are: medium to fine sand and silt,
clayey sand, sandy clay and clay, shell sand and clay, peat, limestone, and
dolomite. The deposits range in age from the Eocene Epoch (58 to 36 million
years ago) to the Recent. The oldest deposit that crops out within the map
boundaries is limestone of Upper Eocene age.
Limestone crops out or is very near the surface only along the far western
edge of the map area. Here the Upper Eocene limestones of the Ocala Group crop
out and are actively mined. The limestone is a very fine to fine grained, chalky,
porous, cream colored limestone containing many large foraminifera and abundant
mollusks. Hardness varies as does the amount of recrystallization. Small areas of
Suwannee Limestone of Oligocene age (36 million to 25 million years ago) occur
as erosional remnants in southern Sumter and northern Polk counties. These were
deposited in low places on the top of the Ocala Group and have not yet been
removed by erosion. This limestone is generally solution pitted and recrystallized
with occasional chert occurring sporadically in this area resulting from the
silicification of the upper portion of the Ocala Group limestones. The occurrence
of the chert is too sporadic to be mapped; thus, it is not represented as a lithic
unit on the map. Locally, however, it interferes with quarrying operations and
drilling of wells.


The surface of the limestone dips gently eastward from the outcrop area
beneath an increasing thickness of younger materials. This is graphically
illustrated on the cross sections A-A' and B-B'. The clayey sand and sandy clay
sediments overlying the Tertiary limestones have been referred to as Miocene
(25 million to iU million years ago) in age. These lithologies are in the Hawthorn
Formation. The highly variable, diverse lithologic character of the Hawthorn
includes interbedded and interfingering sands, clayey sands, sandy clays,
phosphatic sediments, dolomites and limestones. The carbonate portion generally
occurs in the lower Hawthorn and contains highly variable amounts of sand,
clay and/or phosphorite. The Hawthorn sediments underlie the entire map area
except in the limestone outcrop area and in scattered areas where it was removed
by erosion prior to deposition of younger units. Scattered outcrops of Hawthorn
sandy phosphatic dolomites and limestones too small to map occur in springs on
the Wekiva Plain northwest of Orlando.
Dolomite occurs at the surface only in isolated small outcrops that are
too small to map. It commonly occurs in the subsurface in the Eocene formations
and the Hawthorn Formation. The dolomites can be seen on the cross sections
A-A', B-B' and C-C'. The Eocene dolomites are brownish in color, porous to
dense, hard and crystalline. The dolomites of the Hawthorn Formation are buff
colored, crystalline, soft to hard, and impure, containing varying amounts of
sand, clay and phosphorite.
Clayey sands coser extensive areas of the central and western portions
of the map area. They comprise much of the higher areas of the Central
Highlands (elevations up to 310 feet near Lake Apopka). Lithologically,
the clayey sands contain silt, fine to coarse sands and gravels bound by a
matrix of clay. The clay may be kaolinite, montmorillonites or other clay
minerals depending upon the depositional environment and post-depositional
alterations. Coloration of the clayey sands varies from greenish and gray to
orange hues. Large, steep-sloped outcrops through this material may be seen
on many highways and m borrow pits of the area. These clayey sand sediments
that do not belong to the Hawthorn have been variously called unnamed coarse
clastics, Miocene coarse plastics, Citronelle Formation, and "Fort Preston"
formation. At the present time there is still uncertainty as to the format;onal
identity of the unit or units.
Sandy clays and clays do not crop out in sufficient quantities to provide
a mappable surface unit in the map area. Subsurface sandy clay and clay units
have been recognized and are shown on the cross sections. Lithologically they
are green and bluish gray to cream and buff colored with varying amounts of
sand and phosphorite. They do not contain shell material.
Unconsolidated sands are widespread throughout the map area and
represent two basic depositional environments. The first and most widespread
occurrence is due to deposition by marine agents. This includes large areas
of Orange and Osceola counties, making up the Osceola Plain, the Atlantic
Coastal Ridge, and par. of the Atlantic Coastal Lowlands in Volusia County.
Associated with these deposits are the sands deposited as dunes. The second
environment is one in which h the sand is deposited due to fluvial agents. Deposits
of this type occur in the Central Valley from Lake Apopka northward and in
areas bordering on the clayey sand highlands. Basically, sands are eroded from
the higher areas and redeposited in valleys and lowlands. The two types of sand
deposits overlap and interfinger.
This lithologic type consists of medium to fine sands and silts, lack-
clay or shell. The surface expression of the unit is generally flat to slightly
undulating except in areas of dune formation where the relief may be more
pronounced. Formational equivalents of the sands have not been resolved.
Puri and Vernon's (1964) geologic map shows them as marine and estuarine
terrace deposits. They are underlain in some areas by the shelly sand and clay
lithology, in other areas by the Hawthorn Formation and in a few scattered areas
by limestone of Eocene Age. As seen in the cross sections, the subsurface
expression of this lithology occurs as facies in several different formations
including the Miocene Hawthorn Formation.
Shell beds of Miocene through Pleistocene age occur on the eastern
portion of the map area. They represent ancient lagoonal and estuarine environ-
ments and contain a highly variable association of lithologies. The lithologies
represented by this unit include coquina, shelly sands, shelly clays, and sands and
clays. The lithologies vary with such frequency that mapping an individual
component is not possible on a regional scale. This unit is generally found below
35 feet above mean sea level and forms much of the Atlantic Coastal Lowlands.
Most of the beaches along the Atlantic Coast segment of this map are designated
as this lithology due to heir incorporporated shell content. Removal by solution of
part or all of the shell material has occurred in areas where the shell beds are
continuously or periodically above the water table. In these areas the residual
sand is part of the shell lithologic unit and is mapped as such. This unit is mined
in Brevard and Volusia counties for road material and is commonly seen surfacing
semi-improved roads of the region.
This unit can be equated with several formations, depending upon the
location. Along the coast it belongs in part to the Anastasia Formation and
partially to the Recent. Inland in the St. Johns River Valley the shell sand,
clay lithology is equivalent to the Caloosahatchee Formation and possibly to a
portion of the Fort Ttompson Formation. Lichtler (1972) stated that fossils
from one of the shell beds of eastern Orange County and from northwestern
Orange County show these sediments to be equivalent to the upper part of the
Tamiami Formation of Mio-Pliocene age.
The shell lithology is overlain to the west and in areas along the coastal
ridge by the medium to fine sand lithologic unit. It pinches out westward toward
the highlands beneath the sands. The surface expression of this unit is generally
a low lying, nearly flat, occasionally swampy terrain with numerous small shallow
solution depressions. Cabbage palms are very abundant in areas where this unit
is at or very near the surface. In the upper St. Johns River Valley and near Lake
Jessup in Seminole County the shell lithology is overlain by thick deposits of
peat.
Peat deposits are found scattered throughout the map area. Most are
relatively small and are not shown on the map. However, several deposits are
shown. One large depot it occurs along the St. Johns River from the southern
map boundary to approximately the latitude of Titusville in Brevard County.
Another large accumulation is shown adjoining Lake Apopka in Orange and Lake
counties. Other smaller deposits are found near Lake Jessup in Seminole County,
just west of Clermont in Lake County, and near Lake Denham in the Lake Harris
Cross Valley in Lake and Sumter counties. These deposits range up to tens of
feet thick.
This lithologic unit consists of black to dark brown, fibrous peat with
varying amounts of sand, silt, and clay incorporated. Occasionally, shells of
fresh-water snails are found scattered throughout the peat.
Some of the pea deposits are an important economic resource for the
area. The peat provide's excellent land for truck farming near Lake Jessup,
Lake Apopka and Lake Denham. Other peat deposits, such as the one near
Clermont, are being mined and sold commercially.

PHYSIOGRAPHY

The State of Florida has been divided into three geomorphic zones by
White (1970). These zones are the northern or proximal zone, the central or
mid-peninsular zone, and the southern or distal zone. The map area is entirely
within White's central or mid-peninsular zone. This zone may be characterized as
having discontinuous highlands forming subparallel ridges separated by broad
valleys all roughly paralleling the present coastline.
The Atlantic Coastal Ridge, Atlantic Coastal Lagoons, and Atlantic
Barrier Chain form and parallel the present coastline of the map area. The
barrier islands are composed of relict beach ridges and dunes and essentially
shield the lagoons from the effects of the sea. The land surface is undulating,
with the highest crests generally no higher than 30 feet above mean sea level.
The islands range in width from a few hundred feet to a maximum of 7 miles at
Merritt Island. The barrier islands are composed primarily of shelly, fine to
medium sands and are thus mapped as belonging to the shell lithologic unit.
Westward from the barrier chain are the Atlantic Coastal Lagoons. These
are a series of lagoons that include the Indian River, Banana River, Mosquito
Lagoon and the Halifax River. The Indian River ends abruptly near the Volusia-
Brevard County line and becomes a valley with its floor reaching elevations of
5 to 10 feet above mean sea level (White 1970). The valley represents the sediment-
filled extension of the lagoon. The infilling is a result of drainage from the
Eastern Valley transporting sediment into the lagoon. The other lagoons also
have been partially filled by sediment and become narrower northward in the
map area


The Atlantic Coastal Ridge lies on the mainland side (west) ot the coastal
lagoons and reaches elevations of 50 feet above mean sea level. It "seems to be
almost wholly a product of Pamlico (?) time when sea level was about 30 feet
higher than it now is" (White 1970). The Atlantic Coastal Ridge is higher and
wider than the common relict progradational beach ridges of the Eastern Valley.
White (1970) attributes this to the lack of shell material in the Coastal Ridge
since it was deposited at the height of the transgression. The other relict beach
ridges were deposited with abundant shell debris that has been subsequently
dissolved, thus reducing the height of these ridges. The Atlantic Coastal Ridge
can be recognized on the map as a body of medium to fine sand paralleling the
coast east of the Eastern Valley.
The Eastern Valley is a broad, flat valley lying immediately west of the
coastal ridge. Many geologists have assumed that the valley represents a broad
Pamlico lagoon. White (1970), however, believes that it represnets a beach ridge
plain lowered due to removal of the carbonate portion of the deposits by
dissolution. The St. Johns River begins in the southern Eastern Valley and
follows it northward until the river turns nearly 90 degrees west to follow the
St. Johns River Offset.
The St. Johns River Offset can be seen only in the north central map area.
It received its name from the fact that the St. Johns River suddenly jogs westward
then northward to follow a more western valley than its headwaters. The reasons
for this change are not clearly understood; however, Pirkle (1969) suggested that
both solution and structural attributes of the underlying rocks were the cause.
As the St. Johns River jogs westward it passes between the Geneva Hill
and the southern end of the Deland Ridge. Both are considered by White (1970)
to be relict beach features. However, the western side of the Deland Ridge is
composed of clayey sands that are lithologically similar to those of the Mt. Dora
Ridge. This may be a remnant of a once ubiquitous highland. The southern
end of the Deland Ridge can be seen in the north central area of the map.
South of the Deland Ridge and the St. Johns River Offset in Seminole,
Orange, and Osceola counties is the Osceola Plain. It is bounded on the east by
the Lake Wales and Mount Dora Ridges. Elevations range from approximately 35
feet to nearly 90 feet. The topography varies from undulating to nearly flat with
few shallow depressions. Much of the Osceola Plain east of U.S. 441 in Orange
and Osceola counties has abundant relict beach ridges which control the drainage
patterns. These are readily identified on aerial photographs of the area. The
relict ridges are generally less than 10 feet in height and usually less than 5 feet.
White (1970) suggests that U.S. 441 marks the approximate line between ancient
broad beach ridge covered barrier on the east from a broad lagoon on the west.
He suggests that the Kissimmee River may have resulted from the drainage pattern
developed in this lagoon as sea level dropped.
North and west of the Osceola Plain are the Marion Upland, Mount Dora
Ridge, the Orlando Ridge and the Lake Wales Ridge. The Marion Upland is
represented by the medium to fine sand lithology west of the St. Johns River
Offset in northern Lake County. The Mount Dora Ridge bounds the Marion
Upland on the west and extends northwest-southeast. It merges with the Orlando
Ridge east of Lake Apopka and with the Lake Wales Ridge south of the lake. The
ridges are all represented by a clayey sand lithology. Vernon (in White, 1958)
refers to the Lake Wales Ridge as a remnant of a Miocene fluvial blanket of bar
plain deposits called the "Hawthorn Delta."
The Mount Dora Ridge and the Orlando Ridge may also represent erosional
remnants of the "Hawthorn Delta." The elevation of the ridge areas range from
50 feet to as high as 310 feet. The ridge surfaces represent a mature karst surface
as evidenced by the wide range in elevations and numerous lakes. White (1970)
postulated that these lakes formed as a result of solution activity controlled by
relict beach ridges, thus giving the lakes and their intervening high ground a
parallel to subparallel alignment.
Bounding the Lake Wales Ridge on the west in Lake and Polk counties
are the Lake and Polk Uplands, the Winter Haven Ridge and the Lakeland Ridge.
All are represented on the map by the clayey sand lithology. The Lake Upland
has numerous lakes covering it. These lakes are suggested by White (1970) to
have formed due to the control of dissolutioning exerted by relict beach ridges.
The numerous lakes give Lake County its name. Unlike the Lake Upland, the
Polk Upland has relatively few lakes. Relict beach ridges can also be seen on
aerial photos of the Polk Upland (White, 1958) and on the 7'a minute topographic
quadrangles of the area. However, the effects of dissolution controlled by the
ridge is not as apparent, possibly due to the thicker sequence of sands, clayey
sands, and clays overlying the limestones.
North of the Lake Upland is the Sumter Upland. They are separated by
the Lake Harris Cross Valley which connects the Central and Western Valleys.
The Sumter Upland is similar to the Polk Upland in its lithology, clayey sand,
lack of abundant lakes and the occurrence of relict beach ridges on its
southern portion.
The Central Valley lies east of the Sumter and Lake Uplands and west
of the Mount Dora Ridge. White (1970) refers to the Central Valley as an
elongate lowland parallel both with the ridges which bound it and the length
of the peninsula. He further states that it represents an unprotected soluble
area reduced to its present lower elevation. The Central Valley is occupied
through most of its length by the Oklawaha River and its tributaries. Also found
in the valley are numerous large lakes including Lake Apopka, Lake Harris, Lake
Dora, and Lake Griffin. Extensive peat deposits are found in the valley along
the Oklawaha River, adjoining Lake Apopka and other smaller deposits. The
other lithologies commonly found in the Central Valley are medium to fine sand
that has worked in from the surrounding highlands, and clayey sand erosional
remnants. The southern end of the valley is shown on the map at the northwest
corner.
The Western Valley also occurs within the map area. It can be seen
on the far western edge of the map and is represented by the limestone lithology
As has been discussed, the map area is quite diverse lithologically and
geomorphically. The land surface has been shaped predominantly by marine
forces and later modified by solution removal of portions of the underlying
carbonate material. Some of the most beautiful terrain found in Florida is
seen in this area.

GROUND WATER

The ground water found in the map area occurs under two conditions,
artesian and nonartesian. Artesian conditions occur in areas where the water is
confined below some impermeable layer known as a confining layer or bed.
In an artesian well, water will rise above the point at which it is first encountered.
Nonartesian conditions exist where the water in the zone of saturation is not
confined and is therefore not under pressure; this is known as the water table.
The nonartesian aquifer is composed primarily of sands and shell with
varying amounts of clay and hardpan. These sediments are generally referred
to as undifferentiated sediments of Miocene to Recent age. It provides only
limited quantities of water of highly variable quality. The thickness and
character of the nonartesian aquifer are highly variable (Lichtler 1972). Wells
developed in this aquifer are primarily used to water lawns and livestock and
limited domestic supplies. The quality of water varies greatly depending on the
composition of the aquifer and other factors. It may be soft or hard depending
on calcium carbonate content. Iron content may be high and pH may vary, often
making the water corrosive.
The artesian aquifers are more important. There are two types of artesian
aquifers in the map area. They are the secondary artesian aquifers and the
Floridan Aquifer. The secondary artesian aquifers occur in the undifferentiated
sediments and more extensively in the Hawthorn Formation. They are composed
of thin beds or layers of limestone, discontinuous shell beds, and layers of sand
and gravel. They generally yield less water than the Floridan Aquifer but more
than the nonartesian aquifers. In the map area the secondary artesian aquifers
generally provide water that is less mineralized than that of the Floridan but
more mineralized than the nonartesian water. The quality of the water varies
with depth, location, and local geologic and hydrologic conditions. The secondary
artesian aquifers are the least likely to be polluted because the overlying, low-
permeability beds protect them from surface pollution, and because drainage
wells are usually cased through the secondary artesian aquifer zone into the
deeper Floridan Aquifer (Lichtler 1972).
The Floridan Aquifer underlies all of Florida and in the map area includes
the Lake City Limestone, the Avon Park Limestone, the Ocala Group Limestone
and some portions of the Hawthorn Formation that are in hydraulic contact
with the underlying limestones. It is one of the most productive aquifers in the
world. In parts of the map area it may reach 2,000 feet in thickness. The
lithologic and hydrologic character of the Floridan Aquifer is not uniform, either
horizontally or vertically (Lichtler 1972). The aquifer consists in general of
alternating layers of limestone and dolomite or dolomitic limestone.


There are numerous solution cavities and solution channels within the
Floridan Aquifer. Some of the cavities may be quite large. For example, a well
in Orlando encountered a 90-foot cavern. These caverns and cavities are inter-
connected and much of the water flows through them as has been shown by
current meter tests in many wells.
The major portion of the ground water recharge in the map area comes
from local rainfall. However, some water enters by underground flow from
outside the region. Total recharge for the East Central Florida region has been
estimated to be on the order of one billion gallons per day (Lichtler 1972).
Discharge of ground water from the Floridan Aquifer occurs by spring
outflow, seepage into the St. Johns River, by outflow to other areas, outflow
to the Atlantic Ocean, and by pumping in the area.
The quality of water in the Floridan varies greatly throughout the area.
Geology is the major factor influencing the water quality but poor quality water
is introduced through drainage wells that are common in some areas. Salt water
is naturally found in some areas such as along the coast and in some parts of the
St. Johns River Valley. It has not yet been flushed out of the aquifer since the
last encroachment of the sea. Heavy pumping in some areas, such as along the
coasts, may cause salt water to encroach and contaminate fresh water supplies.
Yields from the Floridan Aquifer have been measured up to several
thousand gallons per minute; however, lower figures are more common. The
Floridan coes produce more potable water than the nonartesian or secondary
artesian aquifers. In most areas the Floridan Aquifer will produce potable water
from the upper 1,000 feet of the aquifer. Most of the domestic and commercial
supplies in the map area are drawn from this aquifer.

ECONOMIC GEOLOGY

The economic deposits of the map area include phosphate, limestone, shell
material, lithified coquina, sand, clayey sand, and peat.
Phosphate is the most economically important deposit actively exploited
in the area represented on the map. These resources are located in the south-
western portion of the map area in Polk County. Active pits, abandoned mines
and reclaimed lands are very common in the area near Lakeland. The pebble
phosphate deposits occur in the clayey sands of the Bone Valley Formation.
Phosphate mining in Polk County began in 1890. In 1976 approximately 38
million short tons of phosphate were produced in Florida. Other phosphate
deposits of potential economic value are found in the Hawthorn Formation but
are too deeply buried to be economically mined at present.
Shell and coquina are mined locally and used for road base and fIll
material. These are mined only on a local scale and are not an important
economic material.
Sand is found throughout the district as both thin veneers and thick
deposits. Large sand deposits of economic value occur on the ridge areas in
Lake and Polk counties. Other smaller deposits are mined locally and used for
fill material and asphalt production.
Clayey sand is also mined in the map area and is basically used in construc-
tion and road base as fill material. The suitability of the material varies with its
clay content.
Limestone is mined only near the far western edge of the map area in
Sumter County. It is used primarily for road base material.
Peat is locally produced from deposits ranging up to tens of feet thick.
Oi and gas have not been discovered in commercial quantities in the
map area.

REFERENCES

Bermes, B. J.
1958 Interim Report on Geology and Ground Water Resources of
Indian River County, Florida. Florida Geological Survey
Inf. Circ. 18.
Brown, D. W.
1962 (and others) Water Resources of Brevard County, Florida:
Florida Geological Survey Rept. of Invest. 28.
Davis, J. H., Jr.
1946 The Peat Deposits of Florida. Florida Geological Survey
Bull. 30.
Lichtler,W. F.
1968 (and others) Water Resources of Orange County, Florida:
Division of Geology Rept. of Invest. 50.
Lichtler, W. F.
1972 Appraisal of Water Resources in the East Central Florida
Region. Florida Bureau of Geology Rept. of Invest. 61.
Puri, H. S.
1957 Stratigraphy and Zonation of the Ocala Group: Florida
Geological Survey Bull. 38.
White, W. A.
1958 Some Geomorphic Features of Central Peninsular Florida:
Florida Geological Survey Bull. 41.
White, W. A.
1970 The Geomorphology of the Florida Peninsula: Florida Bureau
of Geology Bull. 51.
Wyrick, G. G.
1960 The Ground Water Resources of Volusia County, Florida:
Florida Geological Survey, Rept. of Invest. 22.

OUTCROPS OF INTEREST

1. Brevard County Shell sand, shell clay, and coquina. Brevard County shell
pit. T29S, R37E, Sec. 23, SEE of NE'/.

2. Lake County Clayey sand. T22S, R26E, Sec. 26, NE of NE/.


MoonseL ,


OSCEOLA COUNTYIORANGE COUNTY
South i wor23S 31E 22
C IwOr 23S 31E 31aC
WOs26S31E 5c I
WOs27S 31E4oo WOW25S31E8 TE


4s


SCALE


LOCATION of CROSS SECTIONS


North
ORANGE COUNTY! SEMINOLECO SEMINOLE CO VOLUSIA CO C

WSeW2S-30E9
WOr 22S 31E 28 mWSe20S30E4aob
I S.20S0 WVo 18S 30E-I
o -' WVo 19S 30E 27


C
yr


EXPLANATION


Med.-Fine Sand and Silt


W JClayey Sand


Sandy Clay


SShell, Sand,and Clay


Limestone


n Dolomite


I


I I _I I


-100


I I