MAP SERIES NO. 78


FLORIDA DEPARTMENT OF NATURAL RESOURCES
BUREAU OF GEOLOGY


BUREAU OF GEOLOGY


ENVIRONMENTAL GEOLOGY SERIES


PENSACOLA SHEET

By
Walter Schmidt
LO FLORIDA DEPARTMENT OF NATURAL RESOURCES
DIVISION OF RESOURCE MANAGEMENT
BUREAU OF GEOLOGY


UPTallahassee
1978


INTRODUCTION

Development of guidelines for wise management of Florida's natural
resources depends upon a good working knowledge of the State's geology as
it relates to man's environmental problems. Management decisions must be
based upon adequate geologic data for such fields as waste disposal, water
resources management, land management, highway construction, geologic
hazards, sods mapping, mining and reclamation. Environmental geologic maps
provide the basic data needed for the creation and execution of sound
programs in the above-mentioned fields. It is hoped that this map will not
only serve the purpose for which it is intended but will also serve as a base
map for future presentation of geologically related data of a more specialized
or local nature. The ultimate purpose of the State's environmental geology
mapping program is to insure development of Florida's natural resources with
the least possible environmental damage.
This map presents geologic data in such a way that it can be under-
stood by persons not specially trained in the science of geology. Common rock
types are shown as they occur from just below the soil zone to depths of
expected use for most purposes. Mapping involved aerial photographic and
topographic interpretation and field work (visiting quarries, borrow pits, canals,
road cuts, and other rock exposures) to provide the necessary data points.
Use was also made of all published and unpublished data in the files of the
Florida Bureau of Geology plus published reports of the U. S. Geological
Survey and the U. S. Soil Conservation Service.

PENSACOLA
REGIONAL INTRODUCTION

Setting-Sediments in the western Panhandle of Florida thicken greatly
to the southwest reaching several thousands of feet. The deposits within a
few hundred feet of the surface consist of the post-Miocene Citronelle
Formation and a number of sand and clayey sand units that are associated
with ancient sea level rises and shore lines.
Physiographic divisions for the State of Florida have been proposed
by Puri and Vernon (1964). There are two major divisions in the State west
of the Choctawhatchee River the Gulf Coastal Lowlands and the Western
Highlands. The western panhandle of Florida, of which Walton, Okaloosa,
Santa Rosa, and Escambia counties are part falls within both divisions.
Location and Extent-The four counties that make up the western
panhandle are the western and northernmost counties in Florida. North to
south they measure approximately 45 miles, east to west about 75 miles.
The area is bounded to the north and west by the State of Alabama, to
the east by Holmes, Washington and Bay counties; and to the south by the
Gulf of Mexico. The four counties total 4,047 square miles in land area
although the eastern edge of Walton County along the Choctawhatchee
River does not appear on this map.
Population and Development-The area covered by the map averages
130 people per square mile. The majority of the land, however, would have
less residents than the average because the population is concentrated around
the major cities. Pensacola, the largest city in the region, has the distinction
of being the first area in Florida colonized by the Spaniards in 1559.
Although the settlement was abandoned after two years, Pensacola has grown
to become one of the area's most productive and populous cities, with over
60,000 residents.
The four-county area is not densely populated, compared to many
metropolitan areas, but a number of cities are rapidly growing, with the
Fort Walton area helping Okaloosa County obtain a 44% growth rate in
population since 1960. In addition, Santa Rosa County has grown 28%,
Escambia 18%, and Walton County 4%. The population by county as of
the 1970 census was as follows: Escambia County 205,334 with 84%
being urban residents; Santa Rosa County 37,741 with 34% urban; Oka-
loosa County 88,187 with 62% urban; and Walton County 16,087 with
31% urban residents. The largest cities in the district are Pensacola (60,000)
and Fort Walton Beach (20,000) with other important towns such as Milton,
Gulf Breeze, Crestview, Valparaiso and DeFumak Springs making up towns
of 5,000-10,000 population.
Most of the northern half of the district is rolling hills with sandy,
clayey soils. In fact, the highest natural point in the State occurs at a hill
in northwest Walton County near Lakewood where the elevation is 345 feet.
The northern section is chiefly agricultural. The principal crops grown are
corn, soybeans, potatoes, cotton, and grain with tung and pecan trees
providing additional income. About 75 percent of the area is covered with
pine forests which thrive on the sandy soil. Huge tracts of forest are owned
by a paper company which operates a large plant in central Escambia County.
In contrast, industrial operations predominate in the southwestern
part of the area. Chemicals, synthetic fibers, and paper are the major products
of the local industries. Pensacola is situated on one of the largest natural
harbors in the State and is an important seaport for shipping and commercial
fishing. Raw materials from many parts of the world are shipped to the in-
dustrial area around Pensacola for processing and manufacturing. Tourism
and military operations such as the Pensacola Naval Air Station and Eglin Air
Force Base also contribute to the economy of the area.
Transportation-Interstate 10 is the only four-lane interstate route in
the area. It crosses the four counties at about midway between the coast and
the state line, running from the Alabama line east to Holmes County. Numerous
other State and county roads criss-cross the area as well as hundreds of
secondary roads.
The major cities have railroad and bus service with Pensacola, DeFuniak
Springs and Destin-Fort Walton Beach also having airports. Along with these
public facilities, there are numerous military air-strips throughout the area
associated with the Pensacola Naval Air Station and Eglin Air Force Base.
Climate-The climate for the four-county area is mild and humid, with
long, warm summers and mild winters. The summers average about 80 degrees F.
with night breezes from the Gulf having a cooling effect. The winters average
55 degrees F. with rare cold spells of 15-20 degrees F. Average rainfall in
the district is 63 inches per year with March, July, August, and September
being the wettest at about 6 inches per month. October and November are
the dryest, averaging 3 inches.
Thundershowers of high intensity are common with as much as 3 or
4 inches of rainfall during an hour period. Occasional tropical storms and
hurricanes blow in from the Gulf of Mexico.


GEOLOGY

The near surface deposits of the western Panhandle of Florida include
the non-marine Citronelle Formation generally regarded as late Pliocene,
Pleistocene marine terrace and stream terrace deposits, and Recent stream
alluvium.
The Citronelle Formation blankets the upland areas of the four-county
region. It consists of quartz sands and gravels which are commonly well
sorted but may also be poorly sorted. Common secondary lithologies in
the Citronelle include lenses and beds of relatively pure clay and thin beds
of limonite usually overlying a clay bed. The sediments generally are deeply
weathered with colors ranging from brown and red to purple and orange-yellow.
The formation is variable in thickness due to both an undulating pre-Citronelle
topography and present day dissection.
The distribution and character of the Citronelle sediments suggest that
they are coalescent deposits of several early rivers that emptied into the Gulf
of Mexico. For this reason, few outcrops can be correlated as most clay
lenses and gravel beds are discontinuous. Most often, some amount of silt and
clay are present as a matrix in a sand unit. The varying amount of clay is
gradational and difficult to predict. Uncertainties such as these make a
clayey sand lithology versus a sandy clay lithology difficult to project into
inaccessible areas because of this irregular distribution.
The abundance and grain size of the quartz gravel decreases from the
northwest to the southeast. This would point to a northwestern source for
the Citronelle sediments. Another notable trend readily observed in northern
Escambia and Santa Rosa counties is a typical gravel-limonite-clay sequence
repeated often in the Citronelle. Many hills are capped by gravel and sand,
underlain by a thin bed of limonite, underlain by massive sandy clay. The
limonite is post-depositional resulting from ground water migration through
the sand layers. Precipitation from iron rich solutions occurs as the water
migrates downward to the impermeable clay layers. Limonite, although common,
is not found everywhere, but when it is present it is usually obvious. Many
hillsides are littered with broken limonite because the slope of the land cuts
across the local dip of the limonite beds.
The sandy clay units are found in two forms. One is a gray, massive,
plastic clay that contains only a small amount of quartz sand. This unit
has been mined for brick manufacturing. The other unit is generally gray-
mottled red and gray and contains more sand. The clay in both cases is
kaolinitic with quartz sand being of secondary importance. Beds exposed
are commonly 1-10 feet thick, but a maximum of over 40 feet is known near
the Escambia River. In many locations a 1-4 foot silty sand overlies the
sandy clay unit. This is residual material left behind as the sandy clay unit
is weathered and eroded. Most of the clay has been weathered away from
the overlying sany unit, leaving it relatively clay poor.
Most of the silt to medium sand size material is quartz and clay;
however, small amounts of mica and heavy minerals are also present. Heavy
minerals consist of the accessory detrital minerals of a sedimentary rock
of high specific gravity. Many of the creeks and streams which are actively
eroding the gravel and sandy clay hills contain heavy minerals which can be
seen in the stream bottoms as the heavier particles settle out of the water
column. The concentration of heavy minerals in this way probably would
never be large enough to warrant mining development. Additional heavy
minerals have been noted along the present day coastal area; however, the
volume probably is not great enough to warrant any mining operation.
During repeated invasions of the sea upon the land in the Pleistocene
Epoch, the Citronelle deposits were reworked and mixed with new deposits
of similar composition. As a result, it is generally difficult, if not impossible,
to distinguish the Citronelle beds from the terrace deposits. A few generaliza-
tions can be made, however. The post-Citronelle deposits (overlying sediments)
are usually less consolidated; they contain almost no pebbles, and much less
clay. Because Holocene (recent) reworking had been an important factor
in their deposition, most of this material is found in river valleys and on the
coastal lowlands.
In the northern Walton County area there is one location where a soft
friable limestone outcrops. It is in this region that limestone of lower Miocene
and Oligocene Ages is closest to the surface. The limestone dips steeply to the
southwest and by the time it reaches Escambia County it is approximately
900-1,400 feet below the surface. Other than this one location, limestone is
entirely subsurface in the western panhandle.
In addition to the limestone, the shelly sand and clay beds are also
mostly subsurface. There are only a few isolated instances in Walton County
where these beds are found at the surface. They are also subject to a south-
western dip.

PHYSIOGRAPHY

There are two physiographic divisions in the western Florida panhandle,
the Western Highlands and the Gulf Coastal Lowlands. This division is the
result of a higher sea level stand. The ancient shoreline cut into the present
Citronelle hills and eroded them flat. As sea level receded to its recent level,
the present coastal area was left with little relief. Subsequent erosion in recent
times has brought sand and other material from the hills and displaced it
along the coastal region leaving most physiographic boundaries subtle.
The Western Highlands represents the northern two-thirds of the district,
which are higher in elevation than the coastal area. The Highlands consist
of rolling hills which, for the most part, slope gently southward. They are
underlain by the Citronelle Formation and high-level Pleistocene terrace
deposits. The hills are dissected by numerous large streams, which flow in
deep, flat-bottormed valleys. Many of the fairly steep drainage patterns are
a result of the abundance of clay in the Citronelle sediments. The clay acts
as a cement and tends to hold the sand and gravel together and, as a result,
the sands do not crumble as they normally would.
These sandy clays will interest future planners because of their many
uses, including road-base material, landfill site construction, and building
brick.
In wet months, when the rainfall is the greatest the area is often
gullied and eroded by rushing streams. The high clay content of the sediment
produces a low permeability, so most of the rain which falls in the area is
channeled away by surface runoff. Because of this runoff, a well-developed,
dendritic drainage (branching) pattern has evolved. The area is covered with
creeks and streams, each separated by a drainage divide (a topographic high).
It is this drainage pattern that has produced the hilly topography in the northern
two-thirds of the district. It is through these rolling hills that the Blackwater
River flows. The State of Florida has created a state forest here, the Blackwater
River State Forest and on the river are numerous camp sites to accommodate
campers who canoe along the 40-mile canoe trail. In addition to the Blackwater
River, there are also excellent canoe trails along the Yellow River and the Shoal
River.
Another consequence of the clayey soil is the relative ease with which
local farmers can make small lakes and ponds. By damming up small drainage
basins many local residents have produced up to four small ponds in a series,
each at successively lower elevations. The high clay content of the sediment
or in some cases the limonite hard-pan, prevents much downward seepage of
the water so the pond is well preserved as long as normal rainfall occurs.
The majority of the man-made lakes have been created for cattle and/or
recreation.
When an impermeable clay layer intersects with a hillside quite often
a spring occurs. These springs form small streams which commonly head
in small box canyons known as "steepheads". The headwalls of the gullies
are maintained at a steep angle because undermining at their base by the
springs is more rapid than erosion of the rims.
The largest spring in the western panhandle is Chumuckla Mineral
Springs in northwestern Santa Rosa County, on the east side of the Escambia
River. In 1942 this spring flowed at nearly 50 gallons per minute.


The soils of the highlands are very well-drained, slightly acid, sands
and loamy sands. The vegetation is mostly forests, with some grazing.
Planted crops include corn, peanuts, cotton, oats, and pecans.
The Gulf Coastal Lowlands province borders the Gulf of Mexico and
has some lobes which extend up the larger river valleys. The boundary between
the two provinces Averages about ten miles in from the coast, with the coastal
section generally being less than one hundred feet above sea level.
The soils in the lowlands are poorly drained sands or slightly loamy
sands. The level nature and high water table produce many ponds and swamps
with highly acid soils. Vegetation consists mostly of grasses and flatwoods,
with considerable grazing. Some vegetables and potatoes grow well on these
drained lands.
It is along the beaches of the Gulf Coastal Lowlands where the population
is concentrated. It is also these beaches that attract millions of tourists and
campers each year to enjoy the gulf waters and Florida sunshine.
Another distinctive feature of the topography in addition to the Physio-
graphic provinces are the Pleistocene marine terraces. They have been traced
by previous workers along the Gulf and Atlantic Coasts. Remnants of
these terraces are preserved in the panhandle Florida as upland plateaus,
flat-topped hills, low coastal plains and benches along the rivers and bays.
These terraces are expressions of ancient shorelines.


ECONOMIC GEOLOGY

The development of mineral commodities (except for ground water) in
the western Panhandle has not been carried out on a large scale. Other than
water, the only other mineral commodity that presently serves a commercial
market is quartz sand and gravel. Deposits of clay have been mined in
central Escambia County for the manufacturing of bricks; however, the
companies involved have temporarily suspended operations.
Clayey sand-The sandy clay and clayey sand deposits in the western
hills are used for road-base material for county secondary roads. The sporadic
need for road-base materials provides an insufficient market for commercial
mining; therefore, the supply for this use is obtained principally from county-
owned pits.
Sands and gravel-Quartz sand and gravel is one mineral commodity
that occurs in abundance throughout the district. The gravel is actively
mined in northeast Escambia County for concrete and other construction
use. Sands are mined in many places for construction use, road fill, and
asphalt.
Clays-Clays are present as lenticular beds throughout the Western
Highlands province. The only recent mining operation, however, was near
Barth in Escambia County. Here, brick manufacturing was conducted until
1975, when the company suspended operations. It is anticipated that with
the growth of Pensacola and Fort Walton Beach a need for brick in the future
may reopen these as well as new plants.
Limestone-There are no companies actively mining limestone anywhere
in the district. Limestone is nearest the surface in northeast Walton County,
which may interest mining companies in the future.
Petroleum-In north Santa Rosa County, oil was discovered near the town
of Jay in 1970. The producing strata are approximately 15,000 feet below
the surface in the Smackover Formation, a dolomitic limestone. This
Jurassic Age (150 million years old) limestone is now producing oil in north
Santa Rosa and extreme northeast Escambia counties at a rate of 3.3 million
barrels of oil per month and 3.9 million cubic feet of natural gas per month.


GROUND WATER

Occurrence--A portion of the water that falls as rain percolates downward
into the underlying permeable sediments. This water is called subsurface water,
but only that which is in the zone of saturation (all interstitial spaces filled
with water) is called ground water.
Aquifers and Aquicludes-The ground water reservoir system is made
up of both aquifers and aquicludes. An aquifer is a lithologic unit(s) that
is able to yield usable quantities of water to wells and through which water
moves with relative ease. An aquiclude is a lithologic units) of lower
permeability thantan aquifer which retards the movement of water and which
will not readily yield water to wells.
The abundance of exceptionally good quality ground water in Escambia,
Santa Rosa and Okaloosa counties stems from two factors: the area has one
of the highest annual rainfalls in the country, averaging 63 inches; and the
area is underlain by several hundred feet of unconsolidated quartz sand and
gravel that serve as an immense reservoir for the water that percolates into
the ground. These waterbearing formations are collectively referred to as
the "sand and gravel aquifer".
The sand and gravel aquifer is a wedge-shaped deposit extending north-
ward into Alabama. It generally thickens to the west and southwest from
its thin outcrop along the Walton-Washington county line. Near Pensacola,
the aquifer is 400 to 500 feet thick.
Water from this aquifer is relatively low in mineral content, because
the aquifer consists principally of insoluble quartz sand. Wells in this unit
furnish all the ground water used in Escambia, most of Santa Rosa, and a
part of the smaller supplies in Okaloosa County.
In the eastern part of the district (eastern Okaloosa and Walton
counties), the primary source of water is the Floridan aquifer. It is composed
of permeable and porous limestone which contains large quantities of ground
water. The top of the aquifer ranges from 50 feet below land surface in the
northeastern part of Walton County to 400 feet below land surface in eastern
Okaloosa County. The aquifer ranges in thickness from about 700 feet in
the north to about 1,200 feet in the south.
Water from wells in the Floridan aquifer is of the calcium bicarbonate
type. In the upper limestone beds the water is low in dissolved solids, which
reflects the quality of recharge from the overlying sand-and-gravel aquifer.
At depth within the Floridan aquifer, the water is of the sodium chloride
type and is high in dissolved solids.
Recharge and discharge-The aquifers in the western Panhandle are
replenished by local rainfall, subsurface water movement from updip (Alabama),
and surface water moving into the area. The sand-and-gravel unit which covers
the entire district accepts water from rainfall freely; however, because of
the numerous clay lenses and high clay content of some of the sands, little
vertical movement is possible. Most water entering the aquifer would have
to follow many horizontal paths on clay beds before obtaining a vertical
route downward. The Floridan aquifer accepts recharge from the overlying
sand and gravel unit as well as recharge near the surface further updip.
Aquifer discharge occurs naturally as springs in both aquifers, and
ground water withdrawal by pumping (farming and domestic) also accounts
for considerable depletion. The sand and gravel aquifer contains ground water
under both artesian and water-table conditions. Where the water is confined
by clay or limonite hardpan it is under artesian pressure. Where the water
is not confined by impermeable layers it is under water-table conditions.
In Escambia and Santa Rosa counties there are a few deep-well
injection systems operating for the disposal of chemical waste. These wells
are placing waste material in the lower part of the Floridan aquifer at about
1,200-1,400 feet. The lower Floridan aquifer is saline in this area and is of
no use for consumption. The disposal zone is overlain by an impermeable
clay bed, which is overlain by the upper Floridan aquifer. The upper Floridan
aquifer is cover is covered by another clay bed approximately 300 feet thick which
is overlain by 300-400 feet of the sand and gravel aquifer.


OUTCROPS OF INTEREST

1. Escambia County, Townships 1 and 2S, Range 29 and 30W, bluffs along
west side of Escambia Bay. Above and along the railroad is approximately
a 50 foot section of quartz gravel and sandy clay.
2. Santa Rosa County, Township 6N, Range 29W, Section 35, northwest
quarter, road cut and county road fill site. Along the west side of the road
is a 50-60 foot vertical section exposing well-bedded Citronelle sediments.
A thick sequence of clayey sand and gravel overlies a thin limonite bed which,
in turn, overlies a thick massive sandy clay unit.
3. Okaloosa County, Township 5N, Range 23W, Section 16, southeast
quarter, borrow pit at intersection of State Routes 602 and 2. At this location
a 4 foot thick limonite bed can be observed. It is very sandy and is underlain
by a gray-red orange sandy clay.
4. Walton County, Township 6N, Range 20W, Section 26, southeast quarter.
On dirt road off Route 181 approximately 100 yards south is the only known
outcrop of limestone in the district. At this location is a natural bridge that
was created by the solution and collapse of the limestone. Fossil mollusks
and foraminifera can be found in the limestone.
5. Walton County, Township 2N, Range 19W, Section 21, northwest quarter.
A road cut along Route 278 exposes about 20 feet of clayey sand. Here, the
sediment is not Citronelle material but an older sediment from the Miocene
Epoch (15 million years ago). The clay is dark gray in color and some fossil
molds of mollusks can be seen.


REFERENCES

Bureau of Geology, Florida, Well Files

Huddlestun, P. F.
1976 The Neogene Stratigraphy of the Central Florida Panhandle;
unpub. Ph. D. dissertation, Fla. State University, in press.
Marsh, O. T.
1966 Geology of Escambia and Santa Rosa counties, Western Florida
Panhandle: Fla. Bureau of Geology Bull.46, 140 p.
Morris, A.
1975 The Florida Handbook, 1975-1976. 15th Edition. The Peninsular
Publishing Company, Tallahassee, Fla. 647 p.
Musgrove, W. E., Barraclough, J. T., and Grantham, R. G.
1965 Water Resources of Escambia and Santa Rosa counties, Florida:
Fla. Bureau of Geology Rept.Inv. 40, 102 p.
Pascale, C. A., Essig, C. F. and Herring, R. R.
1972 Records of Hydrologic Data, Walton County, Florida: Fla.
Bur. of Geology, Inf. Circ. 78, 103 p.
Pascale, C. A., and Foster, J. B.
1971 Selected Water Resource Records of Okaloosa County, Florida
Fla. Bur. of Geology, Inf.Circ. 67, 95 p.
Puri, H. S., and Vernon, R. 0.
1956 A Summary of the Geology of Florida with emphasis on the
Miocene deposits, and a guidebook to the Miocene exposures.
Prepared for a field trip of the Gulf Coast Section of The Society
of Economic Paleontologists and Mineralogists, 85 p.
Puri, H. S., and Vernon, R. 0.
1964 Summary of the Geology of Florida, and a Guidebook to the
Classic Exposures. Fla. Bur. of Geology, Special Publication
5 (revised).
Toulmin, S.D.
1955 Cenozoic Geology of Southeastern Alabama, Florida, and Georgia:
Am. Assoc. Petroleum Geologists Bull., V. 39, p. 207-235.
Yon, J. W., Jr., and Hendry, C. W., Jr.
1970 Mineral Resource Study of Holmes, Walton, and Washington
counties: Fla. Bur. of Geology, Bull. 50, 161 p.


DEPARTMENT OF NATURAL RESOURCES

BUREAU OF GEOLOGY

This public document was promulgated at a total
cost of $1,860.00 or a per copy cost of $.74
for the purpose of disseminating geologic data.


EXPLANATION
| Grovel and Coarse Sand

[-- Med-Fine Sand and Silt

SClayey Sand
Sandy Cloy

Shelly Sand and Cloy

Limestone and Dolomite

Limestone


300-


am-


South
A'


South
B'


Northeast
C'


North
A