Domestic Uranium Assessment

Assessment of Undiscovered Sandstone-Hosted Uranium 

Resources in the Texas Coastal Plain, 2015

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2015–3069

November 2015 Printed on recycled paper ISSN 2327-6916 (print) ISSN 2327-6932 (online)

http://dx.doi.org/10.3133/fs20153069

The U.S. Geological Survey estimated a mean of 220 million pounds of 

recoverable uranium oxide (U3O8 ) remaining as potential undiscovered resources 

in southern Texas. This estimate used a geology-based assessment method for 

Tertiary sandstone-hosted uranium deposits in the Texas Coastal Plain sedimentary 

strata (fig.1).

Introduction

The United States is the world’s 

largest consumer of uranium used in 

nuclear power plants, which provide 

approximately 19 percent of the Nation’s 

electricity. More than 90 percent of 

the uranium used domestically to 

generate nuclear power is imported 

(U.S. Department of Energy, 2015). 

Assessment of undiscovered domestic 

uranium resources is a critical component 

of a sustainable nuclear industry in the 

United States.

In 2015, the U.S. Geological Survey 

(USGS) completed an assessment of 

undiscovered uranium resources hosted 

by Tertiary sedimentary sequences of the 

Texas Coastal Plain. These deposits are 

found in sandstones, which are the most 

prolific uranium deposits in the United 

States. Deposits in the Texas Coastal 

Plain region are estimated to contain the 

third largest domestic sandstone-hosted 

uranium resource after the Colorado 

Plateau and Wyoming Basin regions.

Estimates of undiscovered uranium 

resources associated with sandstonehosted deposits in the Texas Coastal 

Plain were made for geologic units 

with known uranium occurrences: the 

Eocene Claiborne and Jackson Groups, 

the Oligocene Catahoula Formation, 

the Miocene Oakville Sandstone, 

the Pliocene Goliad Sand and Willis 

Formation, and the Pleistocene Lissie 

Formation (fig. 1). Sandstone facies 

that host mineralization were deposited 

in mixed marine-coastal-fluvial facies 

(Claiborne and Jackson Groups) and by 

dominantly fluvial systems (Catahoula 

Fifty-gallon barrel containing uranium 

oxide (U3O8), or yellowcake, produced by 

the Hobson Processing Plant in southern 

Texas. (Photo used with permission from 

Uranium Energy Corporation.)

Formation, Oakville Sandstone, Goliad 

Sand, Willis and Lissie Formations). 

Uranium exploration is active throughout 

the region, and the Goliad Sand is host 

to two operating, in situ recovery mines, 

Alta Mesa and La Palangana (fig. 1).

Assessment Methodology

The USGS assessment methodology, the three-part form, uses known 

uranium mineral site locations and deposit 

resources in combination with associated 

geologic features to estimate numbers 

of undiscovered deposits and to identify 

regions that may host them. The method 

includes (1) delineation of geographic 

regions (tracts) that are permissive for 

the occurrence of deposits as guided by 

known deposits and a descriptive mineral 

deposit model, (2) probabilistic estimation of numbers of undiscovered deposits 

within each permissive tract, and (3) calculation of the probable amount of undiscovered uranium based on the estimated 

number of undiscovered deposits and 

grade-tonnage models of known deposits 

in the region using Monte Carlo simulation (Singer and Menzie, 2010).

There are at least 169 identified mineral sites in the region that have produced 

in total approximately 81 million pounds 

of uranium oxide (U3O8) with reported 

in-place (unmined) uranium resources 

of about 59 million pounds of U3O8. Ore 

bodies typically are narrow and long, 

with strike lengths ranging from meters 

to kilometers. In order to establish a 

uniform and consistent definition for a 

uranium deposit, individual mineral sites 

within the same ore body were grouped.

Geologic sedimentary units 

known to host uranium deposits were 

used to delineate three permissive tracts: 

(1) the Claiborne-Jackson tract, (2) the 

Catahoula-Oakville tract, and (3) the 

Goliad-Willis-Lissie tract (table 1). 

The tracts group stratigraphic sequences 

that were deposited in broadly similar 

depositional environments. The tracts 

were geographically subdivided into the 

Rio Grande Embayment sub-tract (the 

southwestern region with more known 

occurrences and higher mineral potential) 

and the Houston Embayment sub-tract 

(the northeastern region with less known 

occurrences and lower mineral potential), 

forming a total of six sub-tracts (fig. 2).
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LA PALANGANA MINE

ALTA MESA MINE

Rio Grande

Embayment

Houston

Embayment

TEXAS

MEXICO

G

ULF OF MEXICO

Llano uplift

Edwards Plateau

San Marcos Arch

0 50 100 KILOMETERS

0 50 100 MILES

Waco

Austin

Houston

Beaumont

San Angelo

Fort Worth

San Antonio

Brownsville

Corpus

Christi

30°

33°

27°

100° 96°

Host unit

Oakville Ss.

Catahoula Fm.

Jackson Grp.

Clairborne Grp.

Wilcox Fm.

Uranium Host Units and Occurrence Types

Known deposits Other types

Goliad Sd.

None

None

!

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!

Epoch and Geologic Units

Alluvium

Goliad Sd.

Fleming Fm. (Oakville Ss. and Lagarto Fm.) 

Catahoula Fm.

Jackson Grp.

Claiborne Grp.

Wilcox Fm.

Windblown deposits

Undifferentiated Pleistocene*

Paleocene

Eocene

Oligocene

Miocene

Pliocene

Pleistocene

Holocene

EXPLANATION

*Includes the Willis and Lissie Formations

MAP

LOCATION

Study

area

Base from National Geophysical Data Center (NGDC), 

ETOPO1 1 Arc-Minute Global Relief Model,

http://www.ngdc.noaa.gov/mgg/global/;

Projection is U.S.A. Continuous Albers Equal Area Conic,

Central meridian –96° E, Latitude of origin 37.5°,

North American Datum of 1983;

Political boundary from Texas Parks and Wildlife Department,

https://tpwd.texas.gov/gis/data/downloads, September 2015

Geology from Schruben and others, 1994
Figure 2. Mineral resource assessment tracts 

showing areas permissive for sandstone-hosted 

deposits in the Texas Coastal Plain. The dashed 

lines represent the approximate location of the 

San Marcos Arch, which separates the tracts into 

the southwestern Rio Grande Embayment (RE) and 

northeastern Houston Embayment (HE) sub-tracts.

Figure 1 (facing page). Generalized geologic map of the southern Texas Coastal Plain showing operating mines and known uranium 

occurrences symbolized by their host geologic unit (color) and type (size and shape). Deposits represent mineral sites with recorded uranium 

production and (or) identified resources. Other types of uranium occurrences include prospects (sites that have some level of exploration), 

showings (sites of interest that have been recorded), and anomalies (sites with indications that mineralizing processes may have taken place). 

The region is subdivided by the San Marcos Arch, a broad southeast-trending geologic feature that influenced the deposition and subsequent 

subsidence of Jurassic through Miocene strata.

Table 1. Assessment results for identified and undiscovered uranium resources in sandstone-hosted uranium deposits, Texas Coastal Plain.

[The tracts are arranged in stratigraphic order, from oldest (Claiborne-Jackson Tract) to youngest (Goliad-Willis-Lissie Tract). RE, Rio Grande Embayment; HE, 

Houston Embayment; km2, square kilometers; area, area of permissive tract in square kilometers; Nknown, number of known deposits in the tract that have identified 

resources (deposits represent grouped occurrences, as explained in the fact-sheet); Nund, expected number of undiscovered deposits; U308, uranium oxide; lbs, 

pounds. Undiscovered resources are reported to two significant figures; numbers may not add up because of rounding. The permissive area is inclusive of the 

favorable and prospective areas. Nund is calculated using a regression equation (Singer and Menzie, 2010). Identified uranium resources include produced (mined) 

and in-place resources; undiscovered resources are calculated as recoverable not in-place. Undiscovered resources are calculated by combining probabilistic 

estimates of numbers of undiscovered deposits with a custom grade and tonnage model using Monte Carlo simulation (Root and others, 1991). See Singer and 

Menzie (2010) for an explanation of quantitative mineral resource assessment methods]

Tract

name

Depositional

setting

Geologic

units Age Subtract

Permissive

area

(km2)

Nknown Nund

Probability of at least the indicated 

amount of undiscovered U3O8

(lbs)

Mean

undiscovered

U3O8 resources

(lbs)

Identified

U3O8

resources

0.9 0.5 0.1 (lbs)

ClaiborneJacksonMarine-coastal; 

barrier island/

strand plain 

system

Claiborne Group

Jackson Group

Eocene RE 38,460 18 27 13,000,000 48,000,000 99,000,000 53,000,000 25,753,429

HE 62,670 1 3 370,000 4,600,000 14,000,000 6,400,000 675,000

CatahoulaOakvilleTransitional; 

fluvial-coastal; 

channels and 

deltaic

Catahoula Formation

Oakville Sandstone

Oligocene 

to Miocene

RE 14,220 35 41 29,000,000 79,000,000 130,000,000 82,000,000 68,815,764

HE 16,710 0 3 350,000 4,900,000 14,000,000 6,400,000 450,000

Goliad-WillisLissieFluvial; meander 

belts, flood 

plains

Goliad Sand, 

Willis and 

Lissie Formations

Pliocene 

to Pleistocene

RE 45,200 10 33 20,000,000 53,000,000 130,000,000 66,000,000 44,906,694

HE 52,250 0 4 370,000 5,300,000 16,000,000 7,000,000 0

Total 229,510 64 111 220,000,000 140,600,887

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Tract 1:

Clairborne-Jackson

Tract 2:

Catahoula-Oakville

Tract 3:

Goliad-Willis-Lissie

Assessment Tracts

Nonpermissive areas

! Uranium occurrence

Permissive areas

San Marcos Arch

EXPLANATION

RE RE RE

HE HE HE
Within each sub-tract, undiscovered resources were assessed 

to a depth of 1,500 feet (~450 meters). Although most 

uranium mining has taken place at depths less than 800 feet 

(~240 meters), economic deposits have been identified to 

depths of more than 1,200 feet (~365 meters); therefore, 

1,500 feet (~450 meters) is the practical depth for the purposes of uranium mineral resource assessment in the region 

at this time.

Undiscovered Resource Summary

A mean estimate of 220 million pounds of undiscovered, 

recoverable U3O8 encompassing all six permissive sub-tracts in 

the Texas Coastal Plain represents nearly 1.6 times the amount of 

uranium that has already been identified and (or) produced from 

the region (table 1). The Rio Grande Embayment sub-tract region 

has the largest estimated undiscovered resource, with a calculated 

mean total of 200 million pounds of undiscovered U3O8, whereas 

the Houston Embayment sub-tract region is estimated to host a 

mean of 20 million pounds of U3O8. Among the six tracts, the 

Catahoula-Oakville tract, as a whole, has the largest estimated 

undiscovered resource (calculated mean total of 88 million pounds 

U3O8), followed by the Goliad tract (73 million pounds of U3O8) 

and the Claiborne-Jackson tract (59 million pounds of U3O8).

In 2014, U.S. utilities purchased 53 million pounds of U3O8

for use in civilian nuclear power reactors (U.S. Department of 

Energy, 2015). Based on these data, the current identified in-place 

resource represents about 1 year of U.S. nuclear fuel requirements. If found and produced, the undiscovered resources of 

the Texas Coastal Plain may satisfy roughly another 4 years of 

domestic requirements.

References

Root, D.H., Menzie, W.D., and Scott, W.A., 1992, Computer 

Monte Carlo simulation in quantitative resource estimation: 

Natural Resources Research, v. 1, no. 2, p. 125–138.

Schruben, Paul G., Arndt, Raymond E., Bawiec, Walter J., 

King, Philip B., and Beikman, Helen M., 1994, Geology 

of the conterminous United States at 1:2,500,000 scale—

A digital representation of the 1974 P.B. King and 

H.M. Beikman map: U.S. Geological Survey Digital 

Data Series DDS-11, Release 2, accessed September 2015, 

at http://pubs.usgs.gov/dds/dds11/.

Singer, D.A., and Menzie, W.D., 2010, Quantitative mineral 

resource assessments—An integrated approach: New York, 

Oxford University Press, 232 p.

U.S. Department of Energy, 2015, 2014 Uranium Marketing 

Annual Report: U.S. Energy Information Administration, 70 p., 

accessed July 2015, at http://www.eia.gov/uranium/marketing/.

Additional Information

Supporting geologic studies of the Texas Coastal 

Plain region are available at http://energy.usgs.gov/

OtherEnergy/Uranium.aspx. Documentation about the 

USGS mineral resource assessment method is available at 

http://minerals.usgs.gov/global/, http://pubs.usgs.gov/of/2001/

of 01-291/ and http://pubs.usgs.gov/bul/b2218/.

Outcrop of the Oligocene Catahoula Formation, which is largely 

composed of volcanic ash that may be an important source of uranium 

for the deposits of the Texas Coastal Plain.

Injection and recovery wells at the La Palangana in situ recovery uranium 

mine, Duval County, Texas. (Photo used with permission from Uranium 

Energy Corporation.)

Contact Information

Mark Mihalasky

mjm@usgs.gov

(509) 368-3118

Susan Hall

susanhall@usgs.gov

(303) 236-1656

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Assessment Team

U.S. Geological Survey: Mark J. Mihalasky, Susan M. Hall, 

Jane M. Hammarstrom, Kathleen R. Tureck, Mark T. Hannon, 

George N. Breit, and Robert A. Zielinski. Texas Bureau of 

Economic Geology: Brent Elliott.

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