GEOLOGICAL SURVEY CIRCULAR 628 

Elemental Sulfur in 

Eddy County, New Mexico 

Elemental Sulfur in 

Eddy County, New Mexico 

By Jim S. Hinds and Richard R. Cunningham 

GEOLOGICAL SURVEY 

A compilation of sulfur occurrences reported from 

wells and outcrops in Eddy County, N.Mex., 

with observations on their geologic setting 

Washington 19 70 

CIRCULAR 628 
United States Department of the Interior 

WALTER J. HICKEL, Secretary 

Geological Survey 

William T. Pecora, Director 

Free on application to the U.S. Geological Survey, Washington, D.C. 20242 
CONTENTS 

Abstract 

Introduction---------------------------------------------------

Purpose and scope-----------------------------------------

Acknowledgments _______ - _ - _ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - History of activity in Eddy County ____________________________ - -

General geology -----------------------------------------------

Sulfur occurrences --------------------------------------------

~orthwest shelf area--------------------------------------

Page 

1 

1 

4 

4 

4 

5 

7 

7 

"Abo," Yeso, and San Andres Formations _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 7 

Artesia Group _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 9 

Delaware Basin area _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 10 

Castile Formation _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 10 

Salado and Rustler Formations _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 13 

References cited _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 13 

ILLUSTRATIONS 

Page 

FIGURE 1. Index map showing location of Eddy County and major tectonic features that affected Permian 

deposition in the Delaware Basin area _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 

2. Map showing location of sulfur recovery plants, surface sulfur occurrences, areas of concentrated 

exploratory drilling, Castile Formation outcrop, and approximate position of the edge of the 

Castile halite _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 

3. Diagrammatic section of Permian formations in Eddy County _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 6 

4. Map showing subsurface occurrences of sulfur in Eddy County _____________ · __________________ 8 

ELEMENTAL SULFUR IN EDDY COUNTY, NEW MEXfCO 

By JIM S. HINDS and RICHARD R. CUNNINGHAM 

ABSTRACT 

Sulfur has been reported in Eddy County, N.Mex., in 

rocks ranging from Silurian to Holocene in age at 

depths of 0-15,020 feet. Targets of present exploration 

are Permian formations in the Delaware Basin and 

northwest shelf areas at depths of less than 4,000 feet. 

Most of the reported sulfur occurrences in the shelf 

area are in the "Abo" (as used by some subsurface 

geologists), Yeso, and San Andres Formations and the 

Artesia Group. Sulfur deposition in the dense dolomites 

of the "Abo," Yeso, and San Andres Formations is 

attributed to the reduction of ionic sulfate by hydrogen 

sulfide in formation waters in zones of preexisting 

porosity and permeability. A similar origin accounts for 

most of the sulfur deposits in the formations of the 

Artesia Group, but some of the sulfur in these 

formations may have originated in place through the 

alteration of anhydrite to carbonate and sulfur by the 

metabolic processes of bacteria in the presence of 

hydrocarbons. 

Exploration in the Delaware Basin area is directed 

primarily toward the Castile Formation. Sulfur deposits 

in the Castile Formation are found in irregular masses 

of cavernous brecciated secondary carbonate rock 

enveloped by impermeable anhydrite. The carbonate 

masses, or "castiles,'' probably originated as collapse 

features resulting from subsurface solution and upward 

stoping. Formation of carbonate rock and sulfur in the 

castiles is attributed to the reduction of brecciated 

anhydrite by bacteria and hydrocarbons in the same 

process ascribed to the formation of carbonate and 

sulfur in the caprocks of salt domes. 

INTRODUCTION 

A worldwide shortage of sulfur accompanied 

by rising sulfur prices from 1964 to 1968 resulted in renewed interest in long-known sulfur deposits in the Delaware Basin area of 

west Texas and southeast New Mexico (fig. 1). 

Early attempts, dating from 1896 to 1918, to 

exploit the surface sulfur deposits of the area 

by open-pit mining methods had failed owing 

to high extraction and transportation costs and 

generally low sulfur prices. The surface deposits and early mining operations were described 

1 

in detail by Richardson (1905) and Porch 

(1917). Sporadic exploratory drilling r.nd development efforts between the years 1918 and 

1966 were made with generally discouraging 

results. The most noteworthy mining effort 

was an open pit operated for 12 year~ as a 

one-man venture near Rustler SpringF. Tex., 

by Mr. Thad Sanford of Carlsbad, N. Mex. 

Sanford recovered 800-900 tons per year of 

"sulfur soil," which he shipped by rail from 

Orla, Tex., and sold as a soil conditioner; in 

1968, he sold most of his holdings to a major 

company. 

In 1966 the Duval Corp. announced plans to 

build a Frasch sulfur plant to exploit sulfur 

deposits on the southwest flank of the central 

basin platform, near the town of Fort Stockton 

in Pecos County, Tex. (fig. 2). The Duvr.l plant 

began production in 1967, and construction of 

another plant in the same area was begun in 

1967 by Sinclair Oil Corp. (Atlantic Richfield 

Co.) (fig. 2). The success of these plants demonstrated that the Delaware Basin sulfur deposits are amenable to exploitation by the 

Frasch process, and the search for sulfur in 

west Texas and southeast New Mexico accelerated to boom proportions. Lease sales en University of Texas lands near the Fort Stockton 

plants brought as much as $300,000 for a 640-

acre lease, and a 555-acre tract in Culberson 

County sold for more than $1 million. Thousands of acres of New Mexico State lanes were 

leased, and hundreds of prospecting-per:""lit applications were filed on Federal lands in Eddy 

County. Early in 1968 the Duval Corp. announced plans to build a $65 million Frasch facility to mine 2.5 million long tons of sulfur 

per year near the old Sanford workings- in the 

eastern part of Culberson County, Tex., near 

the central part of the Delaware Basin and 

only 23 miles south of the south bouncary of 
51 

soo. 

tI.L 

_, 

n. 

::> 

_, 

<( 

z NORTHWEST SHELF 

0::: 

w 

0 

w 

n. EDDY COUNTY 

' OL..-J--L......1.-..L.......I21.-5 ---50.L.-----J75MILE~ 

-

~ 

J 

OZON 

ARCH 

FIGURE 1.-Location of Eddy County and major tectonic features that affected Permian deposition in the Delaware 

Basin area. 

2 
EDDY 

Lovington0 

GAINES 

~DUVAL 

;m,SINCLAI~ 

0 

0

Fort Stockton 

PECOS 

10 0 10 20 30MILES 

EXPLANATION rzL1 Area of Castile Format1on outcrop O Areas of concentrated sulfur exploration 

drilling 

"-._ West edge of Castile Formation 

~ West edge of lowest Castile halite 

(approximate location) 

X Surface show of sulfur 

8 Sulfur plant and operator DUVAL 

o- Sulfur spring 

FIGURE 2.-Location of sulfur recovery plants, surface sulfur occurrences, areas of concentrated exploratory drilling, Castile Formation outcrop, and approximate position of the edge of the Castile halite. 

3 
Eddy County, N.Mex. (:fig. 2). As of 1969, the 

sulfur boom is continuing, encouraged by high 

sulfur prices and the speculation fever common 

to all mineral booms. 

PURPOSE AND SCOPE 

Many articles and reports have been written 

concerning the sulfur deposits in Pecos, 

Reeves, and Culberson Counties, Tex. However, 

only a small amount of data is available on the 

occurrence of sulfur in the extreme northwestern part of the Delaware Basin and the adjacent shelf area in New Mexico. The purpose of 

this report is to present available information 

on sulfur occurrences and to discuss the geologic framework of the sulfur deposits in Eddy 

County, N. Mex., where most of the federally 

owned lands involved in the present exploration activity are located. Sulfur deposits in 

west Texas are discussed because the sulfur in 

the Permian beds of west Texas and southeast 

New Mexico is genetically related. 

ACKNOWLEDGMENTS 

We express our appreciation to the following 

people and organizations: Personnel of the 

New Mexico Bureau of Mines and Mineral Resources, particularly Mr. Robert Bieberman, 

for allowing free access to, and providing assistance with, the Bureau's extensive library of 

well-cuttings samples; Mr. Roger Anderson, 

Geology Department, University of New Mexico, for permission to examine cores collected 

by him; personnel of the University of Texas 

Lands Geology Department for their many 

helpful suggestions and hours spent in informative discussions of the west Texas sulfur deposits; and the many sulfur, oil, and mining 

company personnel who have contributed 

through many hours of discussion on sulfur in 

the Delaware Basin area and the problems of 

finding it. 

HISTORY OF ACTIVITY IN EDDY COUNTY 

Sulfur has been reported from scattered 

drill holes in Eddy County since the early 

1900's. The earliest known reference to sulfur 

in the county is on the driller's log of a water 

well drilled in the town of Artesia in 1909. The 

Jog, from the files of the U.S. Geological Survey, is reproduced below: 

It should be noted that many of the early 

drillers in Eddy County re:pc':"ted "sulphur 

water" and "black sulphur rock" in numerous 

wells. Water saturated with hydrogen sulfide is 

common in wells throughout much of the 

county. It is probable, however, that the reference in th~ "\Vestel"n College Well log to "sulphur and lime" at 1,172 feet indicates elemental sulfur because the standard terms "sulphur 

water" and "black sulphur rc~k" were not 

used. 

Driller's Log 

Western College Well 

Sperry and Lunkins, Drillers 

NW%SE% sec. 17, T. 17 S., R 26 E. 

Commenced: 9-1-1909 

Lithology Depth (feet) 

Concrete _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 40 

Clay and fine gravel _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ __ _ _ _ _ _ _ __ _ ___ __ 200 

Clay _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 500 

Rock _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 660 

Shale _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 681 

Hard rock _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 710 

Hard rock _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 721 

Shale _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 735 

Water rock ------------------------------------------ 741 Shale rock _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 781 

Red sand rock ___________________ ------------------- 800 

Hard lime rock _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 848 

Very hard lime _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 871 

Hard white lime _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1,165 

Sulphur and lime ------------------------------------ 1,172 Bottom of hole _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1,172 

Sulfur occurrences reported from drill cuttings since 1909 range from thin coatings on 

bedding planes to 20 percent sulfur through a 

20-foot interval (reported on a S'ample log prepared from oil-well cuttings). '::he reports of 

sulfur in well cuttings have resulted in several 

surges of prospecting activity. In 1931, sulfur 

was discovered between 940 anc, 960 feet in a 

water well drilled by Oliver Pearson and Sons 

in the NWlj.,NElA, sec. 8, T. 16 S,. R. 25 E. Following this discovery, Union Sul~ur Co. drilled 

five core-hole tests in sec. 8 an-1 surrounding 

sections. Some sulfur was found in one of the 

core holes, in the NE14NW14 sec. 8, between 

900 and 950 feet, but the holes were abandoned, and there has been no activity in the 

immediate area since 1932. 

In 1952, the National Farmerr Union drilled 

a well in the NE1A,NW14 sec. 13, T. 20 S., R. 26 

E., on a Federal prospecting permit belonging 

to S. P. Yates of Artesia, N.Mex. This test was 

probably based on shows of sulfur reported on 

logs from U.S. Army Corps of Engineers and 
U.S. Bureau of Reclamation· damsite test holes 

nearby. Several shows of sulfur were found, 

the best of which contained 4. 7 percent sulfur 

from a 0.9-foot interval between 1,044.8 and 

1,045.7 feet. The hole was abandoned, and the 

permit subsequently expired. 

In 1954, more than a dozen prospecting permits were issued on Federal lands in T. 16 S., 

R. 27 E., but no wells were drilled. In April 

1964, sulfur was found between 2,580 and 2, 

640 feet and between 3,010 and 3,030 feet in a 

well drilled for gas in sec. 6, T. 22. S., R. 24 E. 

On the basis of the reported sulfur shows in 

this well, The Atlantic Refining Co. drilled a 

well in the NW:tA,NW:lJi. sec. 6 in November 1966 

but reported only traces of sulfur at depths of 

3,015 and 3,048 feet. 

Sulfur-exploration activity in Eddy County 

increased rapidly after 1966 subsequent to the 

announcements of discoveries and plant construction in Pecos and Culberson Counties, 

Tex. At least 30 wells were drilled in the 

county from 1966 through June 1969 to test 

for sulfur. As of 1969, exploration activity is 

continuing at a moderate pace; from one to 

three sulfur tests are drilled monthly. 

GENERAL GEOLOGY 

Eddy County encompasses the northwestern 

part of the Permian Delaware Basin and a 

large part of the adjacent northwest shelf area 

(figs. 1, 2). Sulfur occurrences have been reported in the county at depths of 0-15,020 feet 

in rocks ranging in age from Silurian to Holocene. Areas of known occurrences are shown in 

figures 2 and 4. The only sulfur shows of present economic concern, however, are those 

which are found in rocks of Permian age at 

depths of less than 4,000 feet. Figure 3 shows 

the relationship between the Permian formations of the northwest shelf and the formations of the Delaware Basin. Shows of sulfur 

have been reported in each of the Permian formations shown in figure 3 except for the shelfmargin reefs, the Delaware Mountain Group, 

and the Dewey Lake Redbeds. Most of the 

shows reported in Eddy County are in the 

"Abo" (as used by some geologists), Y eso, and 

San Andres Formations and the Artesia Group 

in the shelf area and in the Castile Formation 

in the Delaware Basin area. The name Abo 

Formation has been applied by some geologists 

to rocks on the shelf that lie above the Wolfcamp and beneath the Yeso (fig. 3). However, 

these rocks are 'clearly separated fron and" 

are "stratigraphically higher than th~ type 

Abo" (McKee and others, 1967, p. 39). Sulfur 

is found in the Castile, Salado, and Rustler 

Formations in eastern Culberson County, Tex., 

and in surface "acidic earth" deposits in 

younger rocks in western Reeves Count: .. , Tex. 

The deposits near Fort Stockton, in Pecos 

County, Tex., are reported to be in the Seven 

Rivers, Yates, and Tansill Formations of the 

Artesia Group and the overlying residuum 

from the Salado and Rustler Formations ( Zimmerman and Thomas, 1969). Discussion in this 

report is limited to the Permian rock units 

named above, which contain the majority of 

the reported sulfur occurrences and are presently the prime exploration targets in the 

search for sulfur. 

The "Abo," Yeso, and San Andres Formations and the Artesia Group are restricted to 

the shelf areas. They grade basinward into the 

Bone Spring Limestone and the shelf-1nargin 

reefs (fig. 3). In Eddy County, the "Abo," 

Yeso, and San Andres Formations are composed mostly of dolomite, dolomitic lim~stone, 

and a few thin beds of sandstone, shale, and 

anhydrite. The formations of the Artesia 

Group each consist of a carbonate facier adjacent to the shelf-margin-reef transition zone 

and an evaporite facies farther shelcward. 

Thus, the dominant lithology of each formation in the group grades from dolomite and dolomitic limestone and interbedded red shale 

and sandstone near the reefs to anhydrite, red 

shale~ and sandstone shelfward. The Tansill 

Formation, the uppermost formation of the 

Artesia Group, also contains halite depo~its in 

the shelfward facies (Jones, 1954). 

The Castile Formation is present only in the 

Delaware Basin and is encircled by the Capitan Reef (fig. 2). The Castile is compoo;t·ed of 

anhydrite, calcite-banded anhydrite, halite, 

and limestone. The calcite-banded anhydrite, 

together with two massive halite int~~rvals, 

composes the lower two-thirds, or about 1,200 

feet, of the formation. Toward the w~stern 

margins of the Delaware Basin, the lower part 

of the banded anhydrite unit grades reefward 

into a laminated limestone. The upper third, or 
Q) 

z 

<[ 

::E 

a: 

IJJ 

a. 

~--------NORTHWEST SHELF REEF )IE( DELAWARE BASIN--+ 

ZONE 

====-- -=== = ~U_!'_ 

R I S . E R .L R..M.A i N .I.!Q.!;Ji lM GR 

r TANS FORMATION RUSTLER FORMATION 

~~ YATES FORMATION __$C,A ~~;~~ ..... r::~ SALADO FORMATION -

>-Q: SEVEN RIVERS FORMATION ~< 

~l<!l OUEEN FORMATION _> 

,___ GRAYSURG FORMATION 

SAN ANDRES LIMESTONE 

YESO AND 

"Aso"* FORMATIONS LIMESTONE 

PRE-PERMIAN ROCKS 

*As used by some geologists 

FIGURE 3.-Diagrammatic section of Permian formations in Eddy County. 

BONE SPRING 

LIMESTONE 

J 

a::z 

<[-

:t~a. <(Z:::l 

..J:::lO 

woo:: 

o::ECJ 

l 
about 600 feet, of the formation consists of 

massive white anhydrite intercalated with numerous halite tongues. The halite tongues of 

the upper part of the formation thicken reefward and coalesce into the basal halite strata 

of the overlying Salado Formation (Jones, 

1954). Throughout a broad area in the western 

and southern parts of the Delaware Basin, the 

halite of the Castile Formation is absent owing 

either to nondeposition or to subsequent re·moval by subsurface solution. The formation has 

been eroded from the extreme western part of 

the basin (fig. 2). 

In the Delaware Basin, the Castile Formation is overlain successively by the Salado and 

Rustler Formations. These formations extend 

across the reef formed by the Capitan Limestone and, in the shelf areas, directly overlie 

the formations of the Artesia Group. The Salado and Rustler Formations are present only 

in the eastern half of Eddy County, having 

been truncated by erosion in the western half. 

The Salado Formation is composed of as much 

as 2,000 feet of massive halite beds and includes interbeds of anhydrite and potash salts 

as much as 20 feet thick and thinner beds of 

red shale and sandstone. The Rustler Formation consists of anhydrite, dolomite, halite, and 

minor amounts of limestone, siltstone, and 

sandstone. The soluble salts in both of these 

formations have been removed by solution near 

their areas of outcrop. In areas of extensive solution, only a thin zone of residual material 

from the Salado Formation separates the moreresistant dolomites and gypsum of the Rustler 

Formation from the Casetile Formation or the 

Artesia Group. 

SULFUR OCCURRENCES 

NORTHWEST SHELF AREA 

"ABO," YESO, AND SAN ANDRES 

FORMATIONS 

Areas of sulfur occurrences reported from 

the "Abo," Yeso, and San Andres Formations 

in Eddy County are shown in figure 4. Sulfur 

occurrences in these formations account for 

the majority of the reported sulfur shows in 

the northwest shelf area. Most of the reported 

shows are in the San Andres Limestone in the 

west-central part of the county (fig. 4). The 

sulfur occurs mostly in dolomite and dolomitic 

7 

limestone as thin coatings on fractm·es and 

bedding planes and as small crystals in vugs 

and fractures. Reported amounts ran~:e from 

traces to more than 10 percent. App<:~.rently, 

the sulfur has been deposited as a secondary 

mineral in zones of preexisting porosit~r in the 

dolomite. The most probable origin of the sulfur in these formations is the reduction of sulfate ions in formation waters by hydrogen sulfide, according to the following reaction : 

S0{-2 + 3H:$ -+ 4S + 2H20 + 20H-1 

(Feely and Kulp, 1957, p. 1846). If this is the 

origin of the sulfur, the sulfur depos~tion in 

the dolomites of the r'Abo," Yeso, and San 

Andres Formations is dependent on the following factors : 

1. Preexisting porosity, or the amount of void 

space in the rock available for sulfur deposition. 

2. Permeability, or the transmissibility potential of the rock for formation waters 

transporting sulfate ions and h7drogen 

sulfide to the sites of deposition. 

3. Availability of ionic sulfate. 

4. A vailiability of hydrogen sulfide. 

5. The presence of a suitable trap, either 

structural or stratigraphic, whic]' would 

allow the local concentration of h;rdrogen 

sulfide and ionic sulfate to reach saturation levels favorable to the progression 

of the reaction and the deposition of sulfur. 

6. Continuing replenishment of ionic sulfate 

and hydrogen sulfide within t]'<1 trap 

through the hydraulic system of the host 

rock. 

Ionic sulfate and hydrogen sulfide are commonly found in formation waters throughout 

most of Eddy County. The origin of the: hydrogen sulfide in the northwest shelf arer. is not 

known, but it is probably related to the action 

of bacteria on the widespread hydrocarl:>on accumulations of the area. Numerous zones of 

vuggy porosity with excellent permeability are 

found in the dense dolomites of the for:nations 

under discussion. The coincidence of tha.se factors accounts for the widespread re:r: orts of 

traces of sulfur in the "Abo," Yeso, 2nd San 

Andres Formations in Eddy County. Lr.rge deposits of sulfur in these formations may be expected only where conditions 5 and 6, above, 

are fulfilled in addition to conditions 1 through 
R.21E. 23 24 

I I ... .-{·. I 

T.28S.1 .•• :·(·:· IT. 26S. 

• /~·· NEW MEXIr.o J ..___---~------ ------~---!!---·-~ ------- ---------------- R.21E. 22 23 24 25 28 

5 0 

I I " I I 

TEXAS 

5 

I 10 I 

27 28 

15MILES 

I 

29 30 

EXPLANATION 

' Yates Formation 

~ Seven Rivers Formation 

• Queen Formation 

, Grayburg Formation 

® Artesia Group (formation 

unknown) 

' San Andres Limestone 

• Yeso Formation 

.. "Abo" Formation,as used 

by some geologists 

m Bone Spring Limestone 

~ Pre-Permian formations 

FIGURE 4.-Subsurface occurrences of sulfur in Eddy County. 

8 

R.31E. 
4. The size of a potential deposit is limited only 

by the size of the original trap (condition 5). 

The grade of the deposit is limited by the original porosity within the trap (condition 1), the 

continuance of a supply of ionic sulfate and hydrogen sulfide (conditions 2, 3, 4, and 6), the 

amount of pore space filled by secondary minerals other than sulfur (mainly calcite), and 

the amount of pore space remaining after 

permeability channels have been sealed or deposition has been otherwise interrupted. 

The amount of sulfur in the dolomites of the 

"Abo," Yeso, and San Andres Formations is 

not likely to be much more than 10 or 15 percent, owing to the conditions of deposition as 

set forth above. Even an initial porosity of as 

much as 32 percent, filled to three-fourths capacity with sulfur and calcite in a ratio of 3 to 

1, would result in a sulfur deposit of only 18 

percent. Such deposits may exist in favorable 

structural or stratigraphic traps in the "Abo," 

Yeso, and San Andres Formations in the northwest shelf area of Eddy County. The "Abo" 

and Y eso Formations are presently unattractive targets because of their depth of burial. 

The San Andres lies at moderate depths and 

has showings of sulfur over a broad area. The 

reported depths of sulfur shows in these formations range from about 600 feet in the 

upper part of the San Andres in T. 20 S., R. 24 

E., to more than 4,000 feet in the "Abo" Formation throughout most of the area. 

ARTESIA GROUP 

All the formations of the Artesia Group (fig. 

3) contain reported sulfur occurrences. The 

Seven Rivers, Yates, and Tansill Formations 

are reported to contain part of the ore bodies 

northeast of Fort Stockton, Tex. (Zimmerman 

and Thomas, 1969). In Eddy County there is a 

concentration of sulfur shows in the Grayburg, 

Queen, Seven Rivers, and Yates Formations 

around and southwest of Lake McMillan (fig. 

4). The shows range from traces to more than 

10 percent sulfur as reported, and they occur 

at depths of about 200-1,500 feet. Several samples of weathered surface material containing 

sulfur crystals have been brought to the Carlsbad office of the U.S. Geological Survey by individuals who reportedly obtained the samples 

from areas of Artesia Group outcrops. Definite 

9 

locations for the source of the surface sulfur 

samples are not available. 

The origin of most of the reported sulfur occurrenees in rocks of the Artesia Group is 

probably the same as that proposed for the sulfur occurrences in the "Abo," Yeso, and San 

Andres Formations-local reduction of ionic 

sulfate by hydrogen sulfide in zones of previously existing porosity and permeability. 

Some of the sulfur in the Artesia Group, however, may have originated in place through the 

alteration of anhydrite to carbonate and sulfur 

by the metabolic processes of bacteria in the 

presence of hydrocarbons. This reaction apparently occurs in the caprocks of salt domes and 

has been discussed in detail by Feely anii Kulp 

( 1957). The sulfate-reducing bacteria, utilizing 

hydrocarbons as an energy source, reduce calcium sulfate to calcium carbonate and hydrogen sulfide. The hydrogen sulfide thus formed 

reacts further with additional sulfate ions to 

produee sulfur, which may be deposited in the 

void spaces of the carbonate rock forned by 

the initial reaction. The sulfur deposits of the 

Fort Stockton area appear to have been formed 

in this manner. They are found in carbonate 

lenses within the anhydrite beds of the Artesia 

Group and overlying Salado and Rustler Formations (Zimmerman and Thomas, 1969). The 

Fort Stockton deposits overlie structural highs 

in the Yates Formation. The structures provided sites for the accumulation of hydrocarbons and bacteria and subsequently for the hydrogen sulfide and sulfur. Similar sulfur deposits may occur in the shelfward facies of the 

formations of the Artesia Group in Eddy 

County. 

One area which warrants further testing of 

the shallow Artesia Group is the vicinity of the 

Bluebird 2 Hackberry oil test in the 

SWl,-iNE%. sec. 3, T. 22 S., R. 26 E. An old log 

of this test from the files of the U.S. Geological 

Survey is reproduced below: 

Sample Log 

Bluebird No. 2 Hackberry 

SW%NE%. sec. 3, T. 22 S., R. 26 E. 

Elevation : 3325 feet 

Completed: 8-28-1926 

Lithology 

White limestone 

White limestone, hard ___ _ 

Sandy yellow limestone _ _ 

Hard dark limestone 

Flint limestone, hard _ _ _ _ _ _ _ _ _ ___ _ 

Open cavern 

Derl;h (feet) 

32 

35 

150 

60 

62 

65 
Lithology 

White limestone, first water at 146 feet, just enough for 

drilling _________ -----------------------------------

White limestone, streaks of magnesia _______________ _ 

White limestone ___________________________________ _ 

Blue shale-showing of oil ___________________________ _ 

Blue limestone _____________________________________ _ 

Blue shale, showing oil _____________________________ _ 

White limestone ___________________________________ _ 

Blue shale, turning hard and darker _________________ _ 

Oil sand, some free oil ------------------------------

Hard limestone, water at 288 feet ___________________ _ 

Open flowing river of water, tools dropped entire 

distance ____________________________ -------- __ - _--

Close yellow sandstone _____________________________ _ 

White limestone and blue shale alternating ___________ _ 

Shale ______________________________________________ _ 

White limestone ____________________________ ------- _ 

Blue shale _-- _- _____ ------- _------------------------

Soft white limestone _______________________________ _ 

Blue shale ________________________________________ _ 

White limestone ______________________ -- _______ --- __ 

Blue shale ___________________________ --------------

Broken limestone, shale water _______________________ _ 

White limestone ______________________ -- ___ -------- _ 

Cave, strong sulphur water _________________________ _ 

White limestone ________________________ - --------- __ 

Brown limestone ______________________ ------- ______ _ 

Blue shale, black sulphur above it -------------------- White limestone ___________________________________ _ 

Blue shale _ - - - - - - __ - _ - - - _- - ___ - - _ - - __ - -- - --- -- -- -- -

Open cave, black sulphur coating tools _______________ _ 

White limestone, sulphur streaks _____________________ _ 

Limestone, showing trace of oil _____________________ _ 

White limestone, streaks of sulphur and bands of shale 

Total depth 1,258 feet. 

Log kept by Scott Etter, Mgr. 

Depth (feet) 

160 

170 

180 

188 

195 

217 

255 

267 

278 

320 

345 

355 

400 

402 

409 

411 

429 

431 

480 

482 

500 

531 

535 

642 

695 

697 

799 

801 

807 

915 

955 

1,258 

This well was drilled on the south edge of a 

domal structure near Carlsbad, N. Mex. The 

association of oil shows in cavernous limestones with "streaks" of sulfur reported at 

1,258 feet ii noteworthy. The well was spudded 

in the Tansill Formation, and its bottom at a 

depth of 1,258 feet is probably within the 

Seven Rivers Formation. 

DELAWARE BASIN AREA 

CASTILE FORMATION 

The Castile Formation is presently the 

prime target of sulfur exploration in the Delaware Basin area. The formation is limited to 

the Delaware Basin as outlined by the trace of 

the Capitan Reef. The Castile has been eroded 

in western Culberson County, Tex., and is covered by younger rocks throughout the eastern 

two-thirds of the basin. The general area 

where the Castile j s exposed in outcrop is 

shown in figure 2. 

Most of the known surface occurrences of sulfur in the Delaware Basin are within the outcrop area of the Castile Formation. A few of 

10 

the surface sulfur occurrences are east of the 

outcrop of the Castile in rocks of Rustler Formation age near Rustler Springs and of Cretaceous age in western Reeves County (fig. 2). 

The deposits near Rustler Sprir ?:S apparently 

extend at depth into the Castile Formation. Referring to this area, Zimmerman and Thomas 

(1969, p. 17) stated: "There are 400 to 600 

feet of massive gypsum and anhydrite beneath 

the Rustler Formation which is probably Salado in age. The limestone equivalent of this 

zone contains the most sulfur. Banded anhydrite of the Castile Formation underlies the 

massive gypsum and anhydrite." We believe 

that the "massive gypsum ard anhydrite" 

constitute the upper massive part of the Castile Formation which overlies t1·~ banded anhydrite that makes up the lower approximate 

two-thirds of the formation. A trin zone of Salado residuum is probably present at the top of 

this interval in the Rustler Sprir,gs area; however, it appears that the major r~rt of the ore 

body is within the Castile and r~t the Salado 

Formation. The sulfur in wc~tern Reeves 

County may also extend downward into rocks 

of Rustler and Castile age. 

The surface occurrences of sulfur in the Delaware Basin form a general northwest trend 

extending from western Reo.ves County 

through eastern Culberson County, Tex., and 

into the southwestern part of Eddy County, N. 

M·ex. Numerous exploratory core holes have 

been and are being drilled along the trend. 

f -llle of the areas of concentrated drilling activity are shown in figure 2. Zilnmerman and 

Thomas (1969) reported that, in addition to 

Duval's deposit in Culberson County, Sinclair 

Oil Corp. (Atlantic Richfield Co.) has announced a nearby discovery ( ar extension of 

the Duval deposit) ; three small deposits have 

been delineated that have combined in-place reserves of about 800,00 long tons; and two other 

promising areas are being evaluated that have 

likely potentials of at least 1 million long tons 

of recoverable sulfur each. Reserve figures 

have not yet been released for the Sinclair 

strike. The latest published reserve figures for 

the Duval Rustler Springs deposit are 57 million long tons (Zimmerman and Thomas, 

1969). Unpublished reserve estimates of 81 million tons were submitted to the Texas Land 

Commissioner in 1969 for the combined Du-
' val-Sinclair deposits for the purpose of unitizing operations. 

The sites of sulfur deposits in the Castile 

Formation are cavernous masses of brecciated 

secondary carbonate rock which locally replace 

the massive and laminated anhydrite typical of 

the formation. The secondary carbonate buildups are usually roughly circular in plan view 

although their shapes vary greatly. They extend vertically, in some places, to the base of 

the Castile Formation where they rest on apparently normal and undisturbed beds of the 

Delaware Mountain Group. These carbonate 

masses, appropriately named "castiles" 

(Adams, 1944, p. 1606), form resistant topographic features in areas where they have 

been exposed by erosion. Several dozen castiles 

were mapped in surface exposures by King 

( 1949). Several others, which do not crop out, 

have been discovered in the subsurface by 

drilling operations. The following are examples of these castiles: 

1. The Screwbean oil field (fig. 2), reported to 

produce from a reservoir in a subsurface 

castile (West Texas Geological Society, 

1960, p. 23). 

2. A sulfur deposit in the southern part of 

block 61, township 1, Texas and Pacific 

Survey, Culberson County, Tex., discovered by R. Y. Anderson of the University 

of New Mexico in a well drilled in connection with a study of the laminations 

of the Castile anhydrite. The approximate location of Anderson's core hole is 

shown in figure 2. Normal gypsum and 

anhydrite of the Castile Formation were 

penetrated in the first several hundred 

feet of the Anderson hole. At a depth of 

about 666 feet, this hole penetrated cavernous carbonate rock typical of the castile masses. Sulfur is present in the Anderson hole at depths of 666-735 feet. 

The interval between 725 and 735 feet 

contains more than 20 percent sulfur. 

This deposit has been extensively drilled 

by Texaco and other companies with adjacent leases. 

3. The main ore zones at the Duval mine site 

near Rustler Springs are evidently in a 

castile-carbonate buildup underlying and 

extending into the Rustler Formation. 

4. The sulfur deposits northeast of Fort 

11 

Stockton. Although the deposits occur in 

evaporites of the Artesia Group and the 

Rustler Formation, they are in castilelike 

masses of cavernous carbonate enveloped by anhydrite. Their origin is probably the same as that of the castileR in the 

Castile Formation. 

Several origins have been proposed to account for the castiles. The West Texas Geological Society (1960, p. 23-24) stated: 

The unusual physical appearance of the masses, the 

lack of bedding and the presence of random f1·agments 

of banded lower Castile imbedded in the limestone 

matrix, all contribute to the difficulty in explaining their 

origin. Metasomatism (replacement) has been suggested by several geologists who have given tl'a.m considerable study. This is the process of practically simultaneous capillary solution and deposition by which a 

new mineral of partly or wholly differing chemical 

composition may grow in the body of an old mineral or 

mineral aggregate. This process seems a logical explanation because of the numerous small faults and 

jointings found in the rocks of the Delawan~ basin. 

Water for the replacement process could come up 

through these breaks. 

Another explanation is that the castHes are 

the cores of collapse features (sinkholes). The 

highly brecciated nature of the bodies and the 

considerable clay filling found in some of the 

castiles support this hypothesis. However, it is 

difficult to explain the subsurface castihs that 

are overlain by s·everal hundred feet of undisturbed and unaltered anhydrite and other 

rocks. The origin of these castiles. may be explained by collapse from below, or natural 

stoping, due to subterranean solution be10w the 

undisturbed strata. The collapsed debris could 

be altered subsequently by metasomatism. 

We believe that an adequate explanation of 

the origin of the castiles must take into account the close association of the ca1·bonate 

masses with hydrocarbons, sulfur, and hydrogen sulfide gas. Although not all the castilecarbonate mounds examined by us in the field 

contain elemental sulfur, nearly all the carbonate rock has a characteristic odor of hydrogen 

sulfide when freshly broken. Our tentative hypothesis is that the brecciated castile masses 

are formed by collapse due to solution from 

below. If collapse continues long enough, the 

stope reaches the surface and results in an ordinary sinkhole which permits the entrance of 

surface waters carrying sand, clay, and col-
loids into the collapse chimney. During the 

course of its formation by upward stoping, but 

before it is vented by fractures to the surface, 

the collapse chimney may become a trap for upward migrating hydrocarbons and hydrogen 

sulfide gas. The anhydrite breccia in the chimney may be converted in part to carbonate by 

reduction by bacteria and hydrocarbons in the 

same process ascribed to the forming of carbonate and sulfur in the caprocks of salt domes 

(Feely and Kulp, 1957). Reduction of the anhydrite yields carbonate and hydrogen sulfide. 

If the chimney vents, most of the hydrogen 

sulfide escapes into the atmosphere. If the 

chimney does not vent, the hydrogen sulfide 

may be trapped and oxidized by reaction with 

sulfate ions to yield elemental sulfur, which is 

deposited in the fractures and vugs of the previously formed carbonate. Recrystallization of 

the limestone in laminae and metasomatic replacement of anhydrite between limestone laminae are also evidently part of the castile-forming process. 

Whatever their origin, the porous carbonate 

masses enveloped by impermeable Castile anhydrite are the sought-after traps in which 

elemental sulfur in some places fills voids and 

solution channels. Several of these carbonate 

bodies are present in southwestern Eddy 

County within the area of the Castile Formation outcrop. Most of them are unmapped. We 

have found traces of sulfur associated with the 

castile carbonates at the surface in three separate areas in New Mexico, and, as previously 

stated, the odor of hydrogen sulfide gas is common from freshly broken surfaces of the carbonate rock. The chances are good that unexposed castile masses are present in the vicinity 

and may be the sites of sulfur deposition. It is 

possible that some of the exposed castiles contain sulfur mineralization at depth or in isolated pockets. 

It is worth emphasizing here one feature I'elated to, or coincident with, the location of all 

the castile-carbonate bodies of which we are 

aware. In the central parts of the Delaware 

Basin, the Castile Formation contains several 

thick beds of crystalline halite. Along the west 

and south sides of the basin, the halite beds either were never deposited or have been removed by subsurface solution. All the limestone castiles and all the surface and subsur12 

face sulfur deposits of which we are aware lie 

beyond the present edge of the lowest Castile 

halite. The approximate position of the edge of 

the Castile salt, as determined by Henry Snider (1965), is shown in figure 2. The spatial 

relation of the salt edge and tl'e castiles and 

sulfur areas is obvious. It appears that the 

most promising area to look for host rocks and 

sulfur-ore bodies is in the zone between the eroded edge of the Castile Forrr.ation and the 

edge of the Castile halite (fig. 2). This is the 

zone of most pronounced subsurface solution, 

and if the origin of the castile-cr.rbonate buildups is due to solution and collaprP., then it is in 

this zone that the most and largest subsurface 

cas tiles are likely to be found. We do not mean 

to imply, however that they cannot exist in 

areas where salt is still present or within the 

anhydrite of other formations. All that appears essential to their formation is: (1) a 

thick section of anhydrite, (2) extensive subsurface solution and collapse, (3) availability 

of hydrocarbons and sulfate-reducing bacteria 

to reduce the brecciated anhydrite to carbonate 

and hydrogen sulfide, and ( 4) maintenance of a 

seal over the trap to prevent the escape of the 

hydrogen sulfide, assuring its further reaction 

with ionic sulfate to produce sulfur, and to 

protect the sulfur deposit from further reaction and removal. 

One location near the present salt edge 

which we believe warrants testing is a hill in 

sec. 5, T. 26 S., R. 25 E., New Mexico principal 

meridian, New Mexico. This hill known as C. 

P. Hill, is capped by remnants of bedded dolomite of the Rustler Formation. The hill is 

not unique in this respect, because there are 

numerous topographic remnants capped by 

Rustler dolomite 10 miles to the east near the 

main Rustler outcrop. What app~ars unusual is 

the preservation of these Rustl~r rocks in an 

isolated hill (actually a cluster of small hills) 

so far west in an area of considerable erosion 

of the Castile Formation. We b~lieve that the 

preservation of this Rustler outlier may be due 

to local subsidence prior to the erosion of the 

Rustler Formation in this area. Its existence 

may be an indication of solution and subsidence at depth in the Castile Formation, which, 

in turn, would be a favorable indication of the 

possible presence of a subsurface castile. The 

area is presently untested. Several other anom-
alous areas in the southwestern part of Eddy 

County have equal possibilities. 

SALADO AND RUSTLER 

FORMATIONS 

Sulfur in the Rustler Formation and in residuum from the solution of Salado beds forms 

part of the ore bodies northeast of Fort Stockton and at the Rustler Springs site in Texas. 

The sulfur in the Rustler and Salado at these 

localities appears to represent the upward extension of castile-type carbonate-ore zones, 

most of which are in the underlying anhydrite 

of the Artesia Group (at Fort Stockton) and 

the Castile Formation (at Rustler Springs). 

We believe that favorable conditions for sulfur 

deposition may occur elsewhere in the Salado 

and Rustler Formations in areas of e.r:ensive 

subsurface solution. We think, however, that 

all the prerequisite conditions necessary for 

sulfur accumulation occur less commonly in 

the Rustler and Salado Formations than in the 

massive anhydrites of the Castile Formation 

and the Artesia Group. The critical factors 

limiting possibilities in the Rustler and Salado 

are probably the lack of available hydrocarbons within prospective traps and the lack of 

effective seals over the traps. 

REFERENCES CITED 

Adams, J. E., 1944, Upper Permian Ochoa series of 

Delaware Basin, west Texas and southeastern New 

Mexico: Am. Assoc. Petroleum Geologists Bull., 

v. 28,no. 11,p. 1596-1625. 

Feely, H. W., and Kulp, J. L., 1957, Origin of Gulf 

Coast salt-dome sulphur deposits: Am. Assoc. Petroleum Geologists Bull., v. 41, no. 8, p. 1802-1853. 

Jones, C. L., 1954, The occurrence and distribution of 

potassium minerals in southeastern New Mexico, 

in New Mexico Geol. Soc. Guidebook, 5th Field 

Conf., Oct. 1954: p. 107-112. 

King, P. B., 1949, Regional geologic map of parts of 

Culberson and Hudspeth Counties, Texas: U.S. 

Geol. Survey Oil and Gas Inv. Prelim. Map 90. 

McKee, E. D., Oriel, S. S., and others, 1967, Paleotectonic investigations of the Permian System in the 

United States: U.S. Geol. Survey Prof. Paper 

515, 271 p. 

13 

Porch, E. L., Jr., 1917, The Rustler Springs sulphur 

deposits: Texas Univ. Bull. 1722, 71 p. 

Richardson, G. B., 1905, Native sulphur in El Paso 

County, Texas, in Contributions to economic geology, 1904: U.S. Geol. Survey Bull. 260, p. 589-

592. 

Snider, H. L., 1965, Stratigraphy and associ2 ted tectonics of the Upper Permian Castile-Saladc-Rustler 

evaporite complex, Delaware Basin, west Texas 

and southeast New Mexico: N. Mex. Univ., unpub. 

doctoral dissert., 196 p. 

West Texas Geological Society, 1960, Geolog~· of the 

Delaware basin and field trip guidebook, F·~pt. 29-

0ct. 1, 1960: Midland, Tex., 97 p. 

Zimmerman, J. B., and Thomas, Eugene, 1969, Sulfur 

in West Texas-its geology and economics: Texas 

Univ. Bur. Econ. Geology, Geol. Circ. 69--2, 35 p. 

* U.S. GOVERNMENT PRINTING OFFICE: 1970 0-377-2t6