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Tishomingo !

§ ̈¦I-35

MARSHALL COUNTY

Ada

GARVIN 

COUNTY

JOHNSTON COUNTY

MURRAY COUNTY

CARTER COUNTY

PONTOTOC COUNTY

COAL COUNTY

GARVIN COUNTY

ATOKA COUNTY

Antelope

Spring

Byrds Mill 

Spring

Davis Sulphur

P

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96°50'

34°20'

34°30'

34°40'

34°10'

96°40'

97°00'

96°20' 96°10' 96°30' 96°20'

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EXPLANATION

Chickasaw National Recreation Area

 Arbuckle-Simpson aquifer outcrop

P Spring

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2009–3013

April 2009

In cooperation with the Oklahoma Water Resources Board

Geochemistry of the Arbuckle-Simpson Aquifer

Printed on recycled paper

the water agency

Introduction Is the Water Safe to Drink?

Figure 1. Location of study area. 

The Arbuckle-Simpson aquifer (fig. 1) in south-central 

Oklahoma provides water for public supply, farms, mining, 

wildlife conservation, recreation, and the scenic beauty of 

springs, streams, and waterfalls. A new understanding of the 

aquifer flow system was developed as part of the ArbuckleSimpson Hydrology Study, done in 2003 through 2008 as a 

collaborative research project between the State of Oklahoma 

and the Federal government (Oklahoma Water Resources 

Board, 2003). The U.S. Geological Survey collected 36 water 

samples from 32 wells and springs (fig. 2) in the ArbuckleSimpson aquifer in 2004 through 2006 for geochemical 

analyses of major ions, trace elements, isotopes of oxygen and 

hydrogen, dissolved gases, and dating tracers (Christenson and 

others, 2009). The geochemical analyses were used to characterize the water quality in the aquifer, to describe the origin and 

movement of ground water from recharge areas to discharge 

at wells and springs, and to determine the age of water in the 

aquifer. 

Most of the water in the Arbuckle-Simpson aquifer is 

suitable for all regulated uses, including public drinking water 

supplies. Median concentration for dissolved solids was 347 

milligrams per liter (mg/L), equivalent to parts per million. 

Hardness of water samples from the Arbuckle-Simpson aquifer 

ranged from 210 to 610 mg/L as calcium carbonate, which is 

considered to be very hard (Hem, 1985). Although not a health 

hazard, hard water can cause scaling in pipes and water fixtures. 

Two domestic wells produced water with nitrate concentrations 

that exceeded the nitrate maximum contaminant level (MCL) 

of 10 mg/L (U.S. Environmental Protection Agency, 2006), a 

health concern primarily for infants and pregnant women. 

Samples from two wells exceeded the secondary maximum contaminant level (SMCL) for chloride of 250 mg/L, and 

also exceeded the SMCL of 500 mg/L for dissolved solids (U.S. 

Environmental Protection Agency, 2006). These two wells are 

flowing artesian wells located at the edge of the freshwater flow 

system and water from these wells is not used for public supply. 
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Vendome

Well

Byrds Mill

Spring

Deep flowing

well

Oil

well

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EXPLANATION

Arbuckle-Simpson aquifer outcrop

Line of schematic section (fig. 3)

Sampling site

!( Spring

!. Water well

! Oil well

Origin and Movement of Water in the Aquifer

Figure 3. Schematic section showing flow paths of water in the Arbuckle-Simpson aquifer.

Ground water in the Arbuckle-Simpson aquifer originates as precipitation falling on the aquifer outcrop (where the 

Arbuckle and Simpson geologic units are found at the land surface). Thus, water in the aquifer is of local origin and does not 

come from great distances. Precipitation falling on the outcrop 

infiltrates into the soil zone, where the water evaporates or is 

transpired by plants back to the atmosphere, or continues down 

into the aquifer to become ground water. 

The dominant rock types of the Arbuckle-Simpson 

aquifer are limestone (calcium carbonate) and dolomite 

(calcium magnesium carbonate). The water chemistry 

is produced by dissolving small amounts 

of minerals in these rocks primarily 

through the action of carbon dioxide 

(in the form of carbonic acid) introduced 

in the soil zone. The dissolution of the 

carbonate minerals causes the water 

to be very hard. Water containing 

mostly calcium bicarbonate is 

found in the western part of 

the aquifer, where the ArbuckleSimpson aquifer is predominantly 

limestone. Calcium magnesium 

bicarbonate water is found in the 

eastern part of the aquifer, where 

the rock type is predominantly 

dolomite.

Water in the aquifer is 

constantly flowing and generally 

flows in the same direction as 

runoff, from topographically 

high areas to topographically 

low areas, to discharge at springs and streams. Typically, 

the time from precipitation entering the Arbuckle-Simpson 

aquifer to discharge at springs, streams, or wells is less than 

60 years, which for ground water is a rapid flow system. 

However, not all water in the Arbuckle-Simpson aquifer 

discharges in a short period of time. Some of the water may 

take a deeper and longer flow path before discharging. Water 

flowing along these longer paths may take thousands of years 

to reach a discharge point.

Figure 2. Geochemical sampling sites in the study area. 

Secondary maximum contaminant levels are established only as guidelines to 

assist public water systems 

in managing the drinking 

water for aesthetic considerations, such as taste, color, 

and odor. These chemical 

constituents are not considered to present a risk to 

human health.

No other water 

samples collected as 

part of the ArbuckleSimpson Hydrology 

Study exceeded MCLs 

or SMCLs. However, not 

every chemical constituent for which the U.S. 

Environmental Protection 

Agency has established 

a MCL or SCML was 

analyzed as part of this 

investigation.
Vendome Well

Vendome Well, in Chickasaw National Recreation Area near the 

town of Sulphur (figs. 2 and 3), may be the best-known well in Oklahoma 

(more than 3 million people visit the park each year). Vendome Well is 

an artesian well that naturally flows about 400 to 500 gallons per minute. 

The dissolved-solids concentration from a water sample from Vendome 

Well was 1,250 mg/L on October 20, 2004. Vendome Well produces water 

from the aquifer at the boundary of the freshwater and saline water zones. 

Water samples collected as part of the Arbuckle-Simpson Hydrology 

Study reveal that water discharging from Vendome Well is a mixture of 

about 99 percent water from the freshwater zone in the Arbuckle-Simpson 

aquifer and 1 percent brine from the saline water zone. Vendome Well 

produces small amounts of hydrogen sulfide gas, which is often described 

as a “rotten egg” smell. Hydrogen sulfide is consistent with the water from 

Vendome Well including some amount of brine. The brine component of 

the water from Vendome Well is likely responsible for the large concentrations of several of the trace elements (potassium, fluoride, bromide, 

iodide, ammonia, arsenic, boron, lithium, selenium, and strontium) found 

in water from the well.

Water from Vendome Well was dated at about 10,500 years before 

present by using carbon-14. The age of water from most of the other water 

samples collected as part of the Arbuckle-Simpson Hydrology Study were 

less than about 60 years old. The old water at Vendome Well indicates 

that the water that discharges at the well flows along long flow paths deep 

in the aquifer; whereas, younger water flows along shorter flow paths at 

shallower depths. 

Concentrations of dissolved argon, neon, and xenon in water 

samples were used to determine the temperature of the water when it 

recharged the aquifer. The recharge temperature of water samples from 

Vendome Well in Chickasaw National Recreation Area near 

Sulphur.

Vendome Well was 6.6 degrees Celsius (44 degrees Fahrenheit), too 

cold to be associated with present day temperatures. The colder recharge 

temperature is consistent with recharge from an earlier, cooler time period.

The mineral springs in the Chickasaw National Recreation Area 

were not studied as part of this investigation. However, based on location, 

the springs are almost certainly like Vendome Well in that the water 

discharged from the springs represents a mixture of water from the freshwater and saline zones of the Arbuckle-Simpson aquifer.

How do We Know the “Age” of Ground Water?

The age of a water sample is not really an age, but rather 

is the period of time since the water was in contact with the 

atmosphere. Water entering the aquifer has naturally occurring 

radioactive constituents that are produced only in the atmosphere and these constituents decay as the water moves through 

the aquifer. For the Arbuckle-Simpson Hydrology Study, ages 

were determined by using analyses of the isotopes tritium, 

helium-3, and carbon-14. 

Tritium is a short-lived radioactive isotope of hydrogen 

with a half-life of 12.32 years. Tritium forms naturally as cosmic radiation interacts with nitrogen in the upper atmosphere 

and was a by-product of above-ground nuclear testing from the 

1950s through the 1960s. Free tritium atoms are incorporated 

into water molecules in the atmosphere. This water, in the form 

of precipitation, falls to Earth containing small amounts of 

tritium and ultimately recharges the aquifer. Tritium is transformed by radioactive decay to daughter product helium-3, a 

rare isotope of helium. By measuring the tritium and helium-3 

content from a ground-water sample, an apparent age can be 

determined because the rate that tritium decays to helium-3 is 

known. Eventually the tritium in a sample decays to the point 

that tritium can no longer be detected with instruments. Samples 

that contain detectable amounts of tritium are considered to be 

modern, meaning that the sample has been in the aquifer less 

than about 60 years. Samples that contain no detectable tritium 

are termed sub-modern and are older than 60 years. Most of 

the ground-water samples collected as part of the ArbuckleSimpson Hydrology Study contained measurable tritium and 

are considered to be modern ground water with ages of a few 

decades or less. Even a deep test hole drilled as part of the 

Study had modern ground water at depths more than 1,490 

feet. Aquifers that contain mostly modern water are vulnerable 

to contamination because contaminants introduced at the land 

surface may travel quickly through the aquifer.

Carbon-14 is the radioactive isotope of carbon with a 

half-life of 5,730 years. Carbon-14 is well known to the public 

as a tool for dating archeological sites, but carbon-14 also 

can be used to date ground water. Like tritium, carbon-14 is 

produced naturally in the upper atmosphere. Tritium dating of 

ground water is appropriate for ages of tens of years; whereas, 

carbon-14 dating of ground water is appropriate for ages of 

thousands of years. Water from Vendome Well (see sidebar) was 

about 10,500 years old as measured by using carbon-14.

How Deep is the Arbuckle-Simpson Aquifer?

The freshwater in all aquifers is underlain by saline water 

(water with dissolved-solids concentrations greater than about 

10,000 mg/L) or by rocks of very low permeability that do not 

produce large quantities of water. The total thickness of an 

aquifer is not important to most users of ground water. Wells are 

drilled until a sufficient supply of freshwater is found and most 

wells in Oklahoma, including in the Arbuckle-Simpson aquifer, 

are less than 200 feet deep. A few wells in the Arbuckle-Simpson aquifer that produce large quantities of water, such as for 

municipal supplies, were drilled to about 1,000 feet. However, 

the maximum depth of freshwater in the Arbuckle-Simpson 

aquifer is still (2009) not known. A test well drilled as part of 

the Arbuckle-Simpson Hydrology Study to 1,820 feet found 

only freshwater.

Water samples collected as part of this study provide information that water may be traveling at great depths in the aquifer. 

All naturally occurring water contains dissolved gases, such as 

the oxygen dissolved in lakes and streams needed for the survival of fish. Water samples from the Arbuckle-Simpson aquifer 

were analyzed for dissolved gases. Excess amounts of dissolved 
Antelope Spring.

Selected References

Christenson, Scott, Hunt, A.G., and Parkhurst, D.L., 2009, Geochemical investigation of the Arbuckle-Simpson aquifer, south-central 

Oklahoma, 2004–06: U.S. Geological Survey Scientific Investigations Report 2009–5036.

Hem, J.D., 1985, Study and interpretation of the chemical characteristics of natural water (3d ed.): U.S. Geological Survey Water-Supply 

Paper 2254, 263 p.

Oklahoma Water Resources Board, 2003, The Arbuckle-Simpson 

Hydrology Study: Oklahoma City, Oklahoma Water Resources 

Board Fact Sheet, 4 p.

U.S. Environmental Protection Agency, 2006, Drinking water contaminants: accessed June 24, 2006, at http://www.epa.gov/safewater/

contaminants/index.html#listmcl

—Scott Christenson1, Andrew G. Hunt1, David L. Parkhurst1, 

and Noel I. Osborn2

1

 U.S. Geological Survey 

2

 Oklahoma Water Resources Board

For additional information please contact

U.S. Geological Survey, Director 

202 NW 66th Street, Building 7 

Oklahoma City, Oklahoma 73116 

Phone: 405–810–4400

Additional earth science information is available at the USGS home 

page at http://www.usgs.gov/ and the Oklahoma Water Resources 

Board home page at http://www.owrb.ok.gov

Graphic design, James Leewright, Oklahoma Water Resources Board

Publishing support provided by Lafayette Publishing Service Center

helium gas were measured in samples from some wells and 

springs. Excess helium in water samples is probably derived by 

the uptake of helium from crustal rocks as water travels along 

flow paths deep in the aquifer prior to arriving at the sampled 

site. At most locations, the crustal rocks are igneous rocks, such 

as granite, and are at least 3,500 feet below the land surface 

(fig. 3). Water samples from Vendome Well had high concentrations of excess helium indicating that the water flows along long 

flow paths deep in the aquifer (see Vendome Well sidebar). 

Five springs had high concentrations of excess helium. 

Multiple flow paths often converge at springs. Although the 

water samples from these springs had modern ground-water 

ages, the excess helium in these samples indicated that at least 

some fraction of the water from these springs has flowed along 

a long, deep flow path before being discharged at the spring 

(fig. 3).

Springs

The springs of the Arbuckle-Simpson aquifer are well 

known for beauty, clarity, and good quality water. More than 

140 springs discharge water from the Arbuckle-Simpson aquifer. Antelope and Buffalo Springs are major freshwater springs 

in the Chickasaw National Recreation Area. Byrds Mill Spring, 

the largest spring in Oklahoma, is the primary source of water 

for public supply for the city of Ada. The average flow from 

Byrds Mill Spring from 1989 to the present is about 8,000 gallons per minute. 

Springs are locations where water flowing through the 

aquifer discharges to the land surface. Thus, water samples from 

springs should chemically resemble water samples collected 

from wells completed in the same aquifer. Water samples were 

collected and analyzed from six springs in the freshwater zone 

of the Arbuckle-Simpson aquifer, including Byrds Mill Spring. 

Chemical analyses of spring-water samples closely resembled 

the analyses from wells, with dissolved-solids concentrations 

ranging from 322 to 361 mg/L.

Beyond the Freshwater Zone

The rocks that compose the Arbuckle-Simpson aquifer 

underlie most of Oklahoma, often at great depths. These rocks 

contain freshwater only where the rocks are at or near the 

land surface. Outside the freshwater zone, the water chemistry 

changes quickly and becomes saline. An oil well, completed in 

the Simpson Group about 4 miles west of Sulphur, Oklahoma, 

was sampled as part of the Arbuckle-Simpson Hydrology Study. 

The dominant dissolved constituents in the water were sodium 

and chloride, the same dominant constituents as seawater. Water 

from this oil well has a chloride concentration of 54,400 mg/L 

and is classified as brine (water with dissolved-solids concentration greater than about 35,000 mg/L). By comparison, seawater 

has a chloride concentration of about 19,000 mg/L. The large 

chloride concentrations and the ratios of other trace-element 

concentrations indicate that the brine formed by evaporation of 

seawater. This brine subsequently migrated into the geologic 

formations of the Arbuckle-Simpson aquifer and is still present 

in places. 

The freshwater part of the Arbuckle-Simpson aquifer was, 

in the geologic past, buried at great depth and contained brine. 

These rocks were subsequently thrust to the land surface by 

tectonic (geologic) forces many millions of years ago, which 

allowed precipitation to infiltrate the aquifer and freshwater 

displaced the brine.

This fact sheet is based on U.S. Geological Survey Scientific 

Investigations Report 2009–5036, “Geochemical investigation of the 

Arbuckle-Simpson aquifer, south-central Oklahoma, 2004–06” by 

Scott Christenson, Andrew G. Hunt, and David L. Parkhurst. 

Copies of that report can be purchased from U.S. Geological Survey, 

Information Services, Box 25286, Denver, CO 80225–0286.