Global Mineral Resource Assessment

Geology and Undiscovered Resource Assessment of the 

Potash-Bearing Central Asia Salt Basin, Turkmenistan, 

Uzbekistan, Tajikistan, and Afghanistan

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010–5090–AA
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Global Mineral Resource Assessment

Michael L. Zientek, Jane M. Hammarstrom, and Kathleen M. Johnson, editors

Geology and Undiscovered Resource 

Assessment of the Potash-Bearing Central 

Asia Salt Basin, Turkmenistan, Uzbekistan, 

Tajikistan, and Afghanistan

By Jeff Wynn, Greta J. Orris, Pamela Dunlap, Mark D. Cocker, and James D. Bliss

Scientific Investigations Report 2010–5090–AA

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Director 

U.S. Geological Survey, Reston, Virginia: 2016

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Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Wynn, Jeff, Orris, G.J., Dunlap, Pamela, Cocker, M.D., and Bliss, J.D., 2016, Geology and undiscovered resource 

assessment of the potash-bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan: U.S. 

Geological Survey Scientific Investigations Report SIR 2010–5090–AA, 106 p., and spatial data, 

http://dx.doi.org/10.3133/sir20105090AA.

ISSN 2328-0328 (online)
iii

Acknowledgments

This publication represents the work of the authors and many reviewers, GIS specialists and 

figure preparers, as well as people familiar with stratabound and halokinetic potash-bearing salt 

deposits. Steve Jasinski (USGS), Lori Apodaca (USGS), Helen Folger (USGS), and Mark Gettings 

(USGS) provided formal technical reviews. Series edit was provided by Kate Johnson (USGS). 

The authors acknowledge Michael Zientek and Jane Hammarstrom of the USGS, who provided 

logistical guidance through the late stages of the USGS global potash assessment.

Bruce Lipin, Greg Spanski, and Steve Ludington participated in the three-part form of 

assessment of the Gissar tact. Chao Yang (Saskatchewan Geological Survey), Mirosław 

Słowakiewicz (Polish Geological Institute–National Research Institute), and Robert J. Ryan 

(Nova Scotia Department of Natural Resources) provided insights into potash deposits in their 

respective countries, and assisted in the three-part assessment of the Gissar tract.

Assistance with the GIS part of this report was provided by a large number of people, especially 

Karen Bolm (deceased), Deborah Briggs, Leila Gass, Robert Miller, and Connie Dicken. Drew 

Luders, Joe Miles, Heather Parks, and Kassandra Lindsey assisted in preparation of figures. All 

these individuals are USGS employees, students, or contractors.
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v

Contents

Abstract...........................................................................................................................................................1

Chapter 1. Overview of the Geology and Assessment of Undiscovered Potash Resources in 

the Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan...........3

Introduction............................................................................................................................................3

Geologic Overview................................................................................................................................8

Basin History, Tectonics, and Structure ..................................................................................8

Basin Stratigraphy.......................................................................................................................8

Salt and Potash ..........................................................................................................................10

Assessment..........................................................................................................................................11

Assessment Depth.....................................................................................................................11

Assessment Methods ...............................................................................................................12

Assessment and Results Summary ........................................................................................12

Summary...............................................................................................................................................12

Chapter 2. Potash-Bearing Salt Assessment for the Gissar Tract (142mxK0005a)—

Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan...........................................................13

Introduction .........................................................................................................................................13

Location................................................................................................................................................13

Basin History........................................................................................................................................13

Salt.........................................................................................................................................................15

Assessment..........................................................................................................................................15

Delineation of the Permissive Tract........................................................................................15

Definition of Resources ............................................................................................................15

Discovered Resources..............................................................................................................19

Akbash................................................................................................................................19

Gaurdak ..............................................................................................................................19

Karabil ................................................................................................................................19

Karlyuk................................................................................................................................19

Kugitang .............................................................................................................................21

Kyzylmazar.........................................................................................................................21

North Gaurdak...................................................................................................................21

Okuzbulak...........................................................................................................................21

South Lyalimkan................................................................................................................22

Tyubegatan.........................................................................................................................22

Mineral Occurrences................................................................................................................22

Adamtash ...........................................................................................................................22

Donguzsyrt .........................................................................................................................22

Khamkan.............................................................................................................................24

Khodzhaikan ......................................................................................................................24

Uzunkuduk..........................................................................................................................26

Exploration and Development History....................................................................................26

Data Availability .........................................................................................................................26
vi

Contents—Continued

Quantitative Estimation.............................................................................................................26

Need for Two Estimation Approaches...........................................................................26

Assessment of Undiscovered Potash Resources as Halokinetic PotashBearing Salt Deposits.........................................................................................26

Three-Part Form of Assessment Process and Rationale..................................27

Results .......................................................................................................................28

Assessment of Undiscovered Resources as Stratabound Potash-Bearing Salt 

Deposits ................................................................................................................30

Overview of the Adaptive Geometric Estimation (AGE) Method ....................30

Parameter Specification.........................................................................................30

(a) Volume.............................................................................................................30

(b) Grade ...............................................................................................................31

(c) Anomalies and Embayments ......................................................................31

Simulation .................................................................................................................32

Results .......................................................................................................................32

Discussion...................................................................................................................................32

Chapter 3. Stratabound Potash-Bearing Salt Assessment for the Amu Darya Tract 

(142sbK0005b)—Turkmenistan and Uzbekistan ........................................................................35

Introduction..........................................................................................................................................35

Location................................................................................................................................................35

Basin History........................................................................................................................................40

Salt.........................................................................................................................................................40

Assessment..........................................................................................................................................42

Delineation of the Permissive Tract........................................................................................42

Definition of Resources ............................................................................................................42

Mineral Occurrences................................................................................................................44

Exploration History.....................................................................................................................44

Data Availability ........................................................................................................................45

Quantitative Estimation.............................................................................................................46

Overview of the Adaptive Geometric Estimation (AGE) Method ..............................46

Parameter Specification..................................................................................................46

Volume .......................................................................................................................46

Grade .........................................................................................................................47

Anomalies and Embayments..................................................................................47

Simulation ..........................................................................................................................47

Results ................................................................................................................................48

Discussion...................................................................................................................................48
vii

Contents—Continued

Chapter 4. Potash-Bearing Salt Assessment for the Afghan-Tajik Tract (142haK0005c)— 

Uzbekistan, Tajikistan, and Afghanistan.....................................................................................49

Introduction..........................................................................................................................................49

Location ...............................................................................................................................................49

Basin History .......................................................................................................................................49

Salt ........................................................................................................................................................49

Assessment .........................................................................................................................................53

Delineation of the Permissive Tract........................................................................................54

Mineral Occurrences................................................................................................................54

Exploration History.....................................................................................................................54

Data Availability .........................................................................................................................55

Discussion...................................................................................................................................55

Chapter 5. Spatial Databases for Resource Assessments..................................................................57

Introduction..........................................................................................................................................57

Overview of Spatial Databases ........................................................................................................57

CentralAsia_deposits Spatial Database ................................................................................57

CentralAsia_thickness Spatial Database ..............................................................................57

CentralAsia_tracts Spatial Database.....................................................................................57

References Cited..........................................................................................................................................61

Additional References.................................................................................................................................65

Appendix A. Summary Descriptive Model of Stratabound Potash-Bearing Salt Deposits............70

Appendix B. Summary Descriptive Model of Halokinetic Potash-Bearing Salt Deposits..............77

Appendix C. Adaptive Geometric Estimation for Stratabound Potash-Bearing Salt 

Deposits—Summary......................................................................................................................84

Appendix D. Grade Data for Gissar and Amu Darya Tracts.................................................................91

Appendix E. Thickness Data for Gissar and Amu Darya Tracts..........................................................94

Appendix F. Generalized SYSTAT Script for Estimation of Undiscovered Contained K2O in 

Central Asia Salt Basin Tracts......................................................................................................97

Appendix G. Glossary of Terms Used in Description of Evaporites..................................................101

Appendix H. The Assessment Team......................................................................................................106
viii

Figures

1-1. Map showing original Central Asia Salt Basin compared with modern sedimentary

basins..............................................................................................................................................4

1-2. Map showing the three assessed tracts within the Central Asia Salt Basin

compared with salt-bearing Upper Jurassic Gaurdak Formation........................................5

1-3. Map showing the three assessed tracts of the Central Asia Salt Basin compared

with modern geographic features on a Landsat image .........................................................9

1-4. Stratigraphic columns showing generalized stratigraphy of the central and 

western Central Asia Salt Basin ..............................................................................................10

2-1. Map showing location of the Gissar tract, Turkmenistan, Uzbekistan, Tajikistan, 

and Afghanistan..........................................................................................................................14

2-2. Map and stratigraphic columns showing structural features influencing the 

Gissar tract and a section of the Upper Jurassic Gaurdak Formation..............................16

2-3. Map showing structural provinces in and near the Gissar tract, Turkmenistan,

Uzbekistan, Tajikistan, and Afghanistan .................................................................................18

2-4. Map showing geology and concession areas in the central part of the Gissar tract,

Turkmenistan and Uzbekistan...................................................................................................20

2-5. Map and cross sections showing parts of the Tyubegatan brachyanticline, the

Lyalimkan area of the Tyubegatan brachyanticline, and the Akbash salt dome,

Turkmenistan and Uzbekistan...................................................................................................23

2-6. Cross sections of the Donguzsyrt salt structure, Turkmenistan.........................................25

2-7. Cumulative frequency plot showing results of Monte Carlo simulation of

undiscovered resources in halokinetic potash-bearing salt deposits in the Gissar

tract, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan.............................................29

2-8. Histogram showing grade distribution for potash in stratabound deposits, Amu

Darya and Gissar tracts, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan...........31

2-9. Histogram showing distribution of estimated in-place K2O content in undiscovered

stratabound potash deposits, Gissar tract , Turkmenistan, Uzbekistan, Tajikistan, 

and Afghanistan .........................................................................................................................32

3-1. Map showing location of the Amu Darya tract, Turkmenistan and Uzbekistan, and

potash occurrences ...................................................................................................................36

3-2. Map of the Amu Darya tract showing drill holes and other point-source information

indicating that at least one meter thickness of potash is present .....................................37

3-3. Map showing named structural provinces in and near the Amu Darya tract,

Turkmenistan and Uzbekistan...................................................................................................38

3-4. Map showing structural features and locations of cross sections in and near the

Amu Darya tract, Turkmenistan and Uzbekistan ...................................................................39

3-5. Cross section A–A’ through the Dengizkul Arch, Turkmenistan and Uzbekistan.............40

3-6. Stratigraphic sections B–B’ and C–C’ through the Amu Darya Basin, Turkmenistan

and Uzbekistan............................................................................................................................41

3-7. Map showing potash thickness contours in the Amu Darya tract, Turkmenistan 

and Uzbekistan............................................................................................................................43

3-8. Histogram showing distribution of estimated in-place K2O content of undiscovered

potash deposits Amu Darya tract, Uzbekistan and Turkmenistan......................................48

4-1. Map showing location of the Afghan-Tajik tract, Uzbekistan, Tajikistan, and 

Afghanistan..................................................................................................................................50
ix

Figures—Continued

4-2. Map showing structural features in and near the Afghan-Tajik tract, Uzbekistan,

Tajikistan, and Afghanistan.......................................................................................................51

4-3. Map showing Mesozoic-Cenozoic structures and locations of cross sections in

part of the the Afghan-Tajik tract, Uzbekistan, Tajikistan, and Afghanistan. Crosssections showing salt domes, Afghan-Tajik tract, Uzbekistan, Tajikistan, and 

Afghanistan .................................................................................................................................52

A-1. Map showing basins containing stratabound potash-bearing salt and those

containing a mix of stratabound and halokinetic potash-bearing salt ............................71

B-1. Map showing basins containing halokinetic potash-bearing salt and those

containing a mix of stratabound and halokinetic potash-bearing salt..............................78

C-1. Flow chart showing generalized approach for assessing stratabound industrial

mineral deposits..........................................................................................................................86

C-2. Graph showing example of a triangular distribution of an unspecified variable with

a mode value of 300, a maximum of 500, and a minimum of 200 .........................................87

C-3. Map showing anomalies and embayments of the Krasnyi IIIB horizon relative to 

the maximum extent of potash as determined by all potash horizons, Solikamsk, 

Russia ...........................................................................................................................................89

E-1. Histogram showing potash thickness in the Gissar and Amu Darya tracts .....................94

F-1. Graphs showing relationship between grade and density for carnallitite and 

sylvinite.........................................................................................................................................97

F-2. Select plot showing potash grade and in-place tonnage estimations from the

adaptive geometric estimation (AGE) method, SYSTAT Monte Carlo simulation ............98

Tables

1-1. Potash ore minerals and their physical properties from Orris and others (2014)..............6

1-2. Select areas of potash exploration and development in eastern Europe and Asia

since 2000.......................................................................................................................................7

1-3. Estimates of potash in undiscovered deposits in the Central Asia Salt Basin,

Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan.......................................................11

1-4. Statistics for grade and tonnage model for halokinetic potash-bearing salt 

deposits ........................................................................................................................................11

2-1. Summary of potash resource assessment results for the Gissar tract,

Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan.......................................................15

2-2. Known deposits of potash within the Gissar tract, Turkmenistan, Uzbekistan,

Tajikistan, and Afghanistan.......................................................................................................17

2-3. Known occurrences of potash within the Gissar tract, Turkmenistan, Uzbekistan,

Tajikistan, and Afghanistan.......................................................................................................24

2-4. Principal sources of information for the Gissar tract, Turkmenistan, Uzbekistan,

Tajikistan, and Afghanistan.......................................................................................................27

2-5. Deposit estimates by individual team members for the Gissar tract, Turkmenistan,

Uzbekistan, Tajikistan, and Afghanistan .................................................................................28

2-6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density

for halokinetic potash-bearing deposits in the Gissar tract, Turkmenistan,

Uzbekistan, Tajikistan, and Afghanistan .................................................................................28
x

Tables—Continued

2-7. Results of Monte Carlo simulations of undiscovered potash resources in

halokinetic potash-bearing salt potash deposits in the Gissar tract, Turkmenistan,

Uzbekistan, Tajikistan, and Afghanistan .................................................................................29

2-8. Parameters used to estimate undiscovered K2O resources in stratabound

potash-bearing salt deposits in the Gissar tract, Turkmenistan, Uzbekistan,

Tajikistan, and Afghanistan.......................................................................................................31

3-1. Summary resource assessment results for the Amu Darya tract, Turkmenistan and

Uzbekistan....................................................................................................................................35

3-2. Evaporite salt structures reported to contain detectable potash in the Amu Darya

tract, Turkmenistan and Uzbekistan ........................................................................................44

3-3. Principal sources of information for the Amu Darya tract, Turkmenistan and

Uzbekistan....................................................................................................................................45

3-4. Parameters used to estimate the undiscovered K2O resources of the Amu Darya

tract, Turkmenistan and Uzbekistan ........................................................................................47

4-1. Known potash occurrences within the Afghan-Tajik tract, Uzbekistan, Tajikistan,

and Afghanistan..........................................................................................................................54

4-2. Principal sources of information for the Afghan-Tajik tract, Uzbekistan, Tajikistan,

and Afghanistan..........................................................................................................................55

5-1. List and description of spatial databases (digital data files) in this report.......................58

5-2. User-defined fields in the feature attribute table for CentralAsia_deposits ....................59

5-3. User-defined fields in the feature attribute table for Central Asia_thickness .................60

5-4. User-defined fields in the feature attribute table for CentralAsia_tracts .........................60

A-1. Ore minerals and common accessory and gangue minerals in stratabound

potash-bearing salt deposits from Orris and others (2014) .................................................73

B-1. Ore minerals and common accessory and gangue minerals in halokinetic

potash-bearing salt deposits from Orris and others (2014) .................................................80

C-1. Densities used in calculating tonnage....................................................................................84

D-1. Grade data for the Central Asia Salt Basin ............................................................................91

E-1. Thickness data for Gissar and Amu Darya tracts, Central Asia .........................................94

F-1. Variables used in the SYSTAT script to estimate undiscovered K2O..................................99

F-2. Generalized SYSTAT script......................................................................................................100
xi

Conversion Factors

Inch/Pound to International System of Units

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

yard (yd) 0.9144 meter (m)

Area

acre 0.4047 hectare (ha)

acre 0.004047 square kilometer (km2)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Mass

ounce, troy (troy oz) 31.015 gram (g)

ounce, troy (troy oz) 0.0000311 megagram (Mg)

ton, short (2,000 lb) 0.9072 megagram (Mg) 

International System of Units to Inch/Pound

Multiply By To obtain

Length

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

meter (m) 1.094 yard (yd) 

Area

hectare (ha) 2.471 acre

square kilometer (km2) 247.1 acre

hectare (ha) 0.003861 square mile (mi2) 

square kilometer (km2) 0.3861 square mile (mi2)

Mass

gram (g) 0.03215 ounce, troy (troy oz)

megagram (Mg) 1.102 ton, short (2,000 lb)

megagram (Mg) 0.9842 ton, long (2,240 lb)

Datum

Vertical coordinate information is referenced to the World Geodetic System 1984 (WGS 84), 

reported in decimal degrees.

Horizontal coordinate information is referenced to the World Geodetic System 1984 (WGS 84), 

reported in decimal degrees.
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Geology and Undiscovered Resource Assessment of the 

Potash-Bearing Central Asia Salt Basin, Turkmenistan, 

Uzbekistan, Tajikistan, and Afghanistan

By Jeff Wynn,1 Greta J. Orris,2 Pamela Dunlap,2 Mark D. Cocker,2 and James D. Bliss2

Abstract

Undiscovered potash resources in the Central Asia Salt 

Basin (CASB) of Turkmenistan, Uzbekistan, Tajikistan, and 

Afghanistan were assessed as part of a global mineral resource 

assessment led by the U.S. Geological Survey (USGS). The 

term “potash” refers to potassium-bearing, water-soluble 

salts derived from evaporite basins, where seawater dried 

up and precipitated various salt compounds; the word for 

the element “potassium” is derived from potash. Potash is 

produced worldwide at amounts exceeding 30 million metric 

tons per year, mostly for use in fertilizers. The term “potash” 

is used by industry to refer to potassium chloride, as well as 

potassium in sulfate, nitrate, and oxide forms (Neuendorf and 

others, 2005). For the purposes of this assessment, the term 

“potash” refers to potassium ores and minerals and potash ore 

grades. Resource and production values are usually expressed 

by industry in terms of K2O (potassium oxide) or muriate of 

potash (KCl, potassium chloride).

The CASB hosts significant discovered potash resources 

and originated in an inland sea during Late Jurassic time. 

Seawater flowed into the CASB, mostly from its extreme 

northwestern margin near the modern Caspian Sea, during 

several evaporation episodes that deposited at least five 

different packages of evaporites, with virtually all potash in 

the second and fourth packages. In this study, the CASB was 

subdivided into three tracts (permissive areas) for evaluation: 

the Amu Darya tract in the west, the Gissar tract in the 

center, and the Afghan-Tajik tract in the east. The Gissar and 

Amu Darya tracts were quantitatively assessed, whereas the 

Afghan-Tajik tract was only qualitatively assessed because 

of the commonly extreme depth (as deep as 7 km) of the 

Jurassic salt, extensive deformation, and a lack of known 

potash deposits.

Two approaches were used to estimate amounts of 

undiscovered potash in the CASB. Stratabound evaporite 

deposits in the Amu Darya tract were evaluated using an 

Adaptive Geometric Estimation (AGE) approach, which 

estimates in-place potash volumes and tonnages. The 

Gissar tract was evaluated by using the AGE approach for 

stratabound deposits and the three-part form of assessment of 

Singer and Menzie (2005) for discrete halokinetic deposits. In 

the three-part form of assessment, numbers of undiscovered 

deposits were estimated and combined with grade and 

tonnage models to probabilistically forecast the amount of 

undiscovered potash. The Amu Darya tract is estimated to 

contain 38 billion metric tons (Bt) of undiscovered potash as 

K2O by using the AGE approach for stratabound deposits. The 

hybrid stratabound-halokinetic Gissar tract is estimated to 

contain between 1 and 16 Bt of undiscovered potash as K2O. 

Chapter 1 of this report provides an overview of the 

history of the CASB and summarizes evaporite potash 

deposition, halokinesis, and dissolution processes that have 

affected the current distribution of potash-bearing salt in 

the CASB. Chapter 2 describes the Gissar tract, an uplifted 

region that contains a mix of stratabound and halokinetic 

potash deposits and all of the discovered and exploited 

potash deposits of the CASB. Chapter 3 describes the Amu 

Darya tract, where evaporite deposits remain flat-lying 

and undeformed since their original deposition. Chapter 4 

describes the highly deformed and compressed Afghan-Tajik 

tract and what is known of the deeply-buried Jurassic salt. 

Chapter 5 describes the spatial databases included with 

this report, which contain a collection of CASB potash 

information. Appendixes A and B summarize descriptive 

models for stratabound and halokinetic potash-bearing salt 

deposits, respectively. Appendix C summarizes the AGE 

method used to evaluate the Gissar and Amu Darya tracts. 

Appendixes D and E contain grade and thickness data for 

the Gissar and Amu Darya tracts. Appendix F provides the 

SYSTAT script used to estimate undiscovered K2O in a CASB 

tract. Appendix G provides a potash glossary, and appendix H 

provides biographies of assessment participants.

1

U.S. Geological Survey, Vancouver, Washington, United States.

2

U.S. Geological Survey, Tucson, Arizona, United States.
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Chapter 1. Overview of the Geology and Assessment of 

Undiscovered Potash Resources in the Central Asia Salt Basin, 

Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

By Jeff Wynn1 and Greta J. Orris2

1

U.S. Geological Survey, Vancouver, Washington, United States.

2

U.S. Geological Survey, Tucson, Arizona, United States.

3

Ages in this report are consistent with the International Chronostratigraphic 

Chart (Cohen and others, 2013).

Introduction

The Central Asia Salt Basin (CASB) is a major 

Jurassic to Early Cretaceous (?)3 evaporite basin that spans 

four countries (Uzbekistan, Turkmenistan, Tajikistan, and 

Afghanistan) and contains a significant amount of the world’s 

potash resources. The basin covers more than 770,000 square 

kilometers (km2) and the area underlain by salt is estimated to 

be approximately 192,800 km2 (fig. 1-1). The hachured area 

on figure 1-1 represents the approximate extent of Jurassic 

evaporites that contain a significant amount of salt; the 

area would have been larger, but less useful for accurately 

assessing potash, if we had included anhydrite and limestone. 

Figure 1-1 also shows that the extent of the basin containing 

Jurassic salt does not correspond to more modern basin extents 

(basins defined by Tellus, USGS, and AAPG); in fact, there 

is no single modern system of recognized basins. The three 

potash tracts shown in figure 1-2 represent the part of the 

CASB that is likely partially to wholly underlain by potash. 

The CASB evaporite deposits unconformably overlie 

a pre-Jurassic basement depression and are thought to 

have evolved through repeated inflow of seawater from the 

northwest (and possibly also the southwest), followed by 

repeated evaporation during the Jurassic and possibly into the 

Early Cretaceous. Known potash deposits in the Gissar tract 

(fig. 1-2) are distal to seawater inflow point(s) of the original 

CASB and this position is consistent with stratabound and 

halokinetic potash-bearing salt models (appendixes A and 

B). Additional, though less extensive, evaporites were also 

deposited in the CASB during Paleogene time. Salt deposition 

associated with known potash deposits is largely confined to 

the Upper Jurassic Gaurdak Formation. Sedimentary rocks 

enclosing the evaporites are generally sandstones and shales 

from terrigenous sources, or marine carbonates. During the 

Miocene, uplift of the Gissar Range divided the basin into the 

Amu Darya Basin to the west (fig. 1-1, blue shading) and the 

Afghan-Tajik Basin to the east (fig. 1-1, lilac shading). All 

known potash deposits and mines occur on the flanks of the 

Gissar uplift, most likely because they are shallow and thus 

more easily discovered and exploited than deep deposits. 

Undiscovered potash resources in the CASB were 

assessed as part of a U.S. Geological Survey (USGS) global 

mineral resource assessment whereby we (1) delineated 

permissive areas (tracts) for undiscovered potash deposits at a 

scale of 1:1,000,000; (2) created a database of known potash 

deposits and occurrences; and (3) where possible, calculated 

probabilistic estimates of the amounts of undiscovered potash 

for each permissive tract (Harris, 1984).

Potassium is an essential nutrient for plants, animals, 

and humans and has no known substitutes (Jasinski, 2015). 

The most common potash minerals, from which potassium is 

derived, are listed with their physical properties in table 1-1. 

Potash demand is primarily driven by demand for fertilizer 

for use in production of food and biofuels (Jasinski, 2015); 

increasing global population, changing diets, and decreasing 

amounts of arable land have increased the need for fertilizer 

minerals, including potash (Magen, 2010). This increasing 

demand has led to upward pressure on prices since the 

beginning of 2008 and subsequent exploration for new potash 

sources, particularly in Europe and Asia (table 1-2). This 

exploration has produced more new data on the geology and 

occurrence of potash than has been available since potash 

exploration efforts of the 1960s and early 1970s. In addition, 

more properties are reported as “currently under development” 

than have been in the previous 30 years combined.
4 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Figure 1-1. Map showing original Central Asia Salt Basin (CASB) compared with modern sedimentary basins. The two 

Tellus sedimentary basins, the Amu Darya and Afghan-Tajik to the west and east of the Gissar Range, respectively, are those 

defined by the World Petroleum Assessment (U.S. Geological Survey World Energy Assessment Team, 2000).

42° N

38° N

34° N

56° E 60° E 64° E 68° E 72° E

KYRGYZSTAN

KAZAKHSTAN

UZBEKISTAN

PAKISTAN

TURKMENISTAN

IRAN

TAJIKISTAN

AFGHANISTAN

Dashkhovuz

Ashgabat

Mary

Mashhad

Bukhara

Chardzhou

Samarkand

Islamabad

Karshi

Termez

Herat

Osh Fergana

Dushanbe

Kulyab

Konduz

Kabul

Tashkent

KOPET-DAG FOREDEEP

KAZAKHSTAN

IRAN

INDIA

CHINA TURKMENISTAN

AFGHANISTAN

UZBEKISTAN

60° E 70° E

40° N

35° N

0 100 200 400 KILOMETERS

0 100 200 MILES

300

Political boundaries from U.S. Department of State (2009).

Albers Equal Area Projection.

Central meridian, 64° E., latitude of origin, 39° N.

EXPLANATION

Tellus Basins AAPG Basins

USGS World Petroleum 

 Assessment Basins

Afghan-Tajik Basin

Afghan-Tajik Basin

Amu Darya Basin

Amu Darya Basin

Approximate area of salt, 

 Central Asia Salt Basin

 (CASB)

Kara Kum Basin

Kopet-Dag Basin

Tadzhik Basin

Turkmen Basin

MODERN SEDIMENTARY BASINS

CAsia_Fig1-1 gjo2

Area of map
Chapter 1 5

UZBEKISTAN

TURKMENISTAN

IRAN

TAJIKISTAN

KYRGYZSTAN

AFGHANISTAN

Bukhara

Navoi

Samarkand

Dzhizak

Dushanbe

Konduz

Termez

Mazar-E-Sharif

Chardzhou

Mary

Karshi

100

300

500

700

900

100

300

100

Chal I & II

Taqcha Khana

Khodzhamumyn

Nurek

Khodzhasartis

Alimtay

Tutbulak

60° E 64° E 68° E

38° N Kulyab

UZBEKISTAN

TAJIKISTAN

TURKMENISTAN

IRAN

AFGHANISTAN

60° E 70° E

40° N

35° N

EXPLANATION

100

Approximate extent of salt, Central 

 Asia Salt Basin (CASB)

Tract 142mxK0005a, Gissar tract

Tract 142sbK0005b, Amu Darya tract

Tract 142haK0005c, Afghan-Tajik tract

Discovered potash deposits

Salt structures—Domes, diapirs, and

 brachyanticlines

Thickness of Gaurdak Formation—

 Contour interval 100 m

0 50 100 150 200 KILOMETERS

0 50 100 MILES

Political boundaries from U.S. Department of State (2009).

Albers Equal Area Projection.

Central meridian, 64° E., latitude of origin, 39° N.

CAsia_Fig1-2 gjo4

Area of map

Figure 1-2. Map showing the three assessed tracts within the Central Asia Salt Basin (CASB) compared with salt-bearing 

Upper Jurassic Gaurdak Formation (adapted from Steinshouer and others, 2006). Note salt structures to east outside approximate 

boundaries of assessment tracts, and thickness of evaporite salt from Steinshouer and others (2006).
6 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Table 1-1. Potash ore minerals and their physical properties from Orris and others (2014).

[Composition formulas from Back and Mandarino (2008); potassium content and specific gravity from Harben and 

Kuzvart (1996) and Anthony and others (1997, 2003); > greater than]

Mineral or material Composition Potassium oxide 

(K2O), percent

Density

(tons/cubic meter)

Primary potash minerals

Carnallite KMgCl3• 6H2O 16.9 1.60

Kainite MgSO4• KCl• 3H2O 19.3 2.10

Langbeinite K2Mg2(SO4)3 22.7 2.83

Polyhalite K2Ca2Mg(SO4)4• 2H2O 15.6 2.77

Sylvite KCl 63.2 2.00

Primary potash ore materials

Carnallitite Mix of halite and carnallite Up to 15 Variable

Hartsalz Mix of sylvite, halite, 

anhydrite, and kieserite

Typically <15 Variable

Sylvinite Mix of sylvite and halite Typically <25 Variable

Accessory potassium minerals

Aphthitalite (glaserite) (K,Na)3Na(SO4)2 42.5 2.69

Arcanite K2SO4 54.1 2.66

Douglasite K2Fe2+Cl4• 2H2O 30.2 2.16

Leonite K2Mg(SO4)2• 4H2O 25.7 2.20

Niter (saltpeter) KNO3 44.0 2.1 

Picromerite (schönite) K2Mg(SO4)2• 6H2O 23.4 2.03

Rinneite K3NaFe2+C6 34.5 2.35

Syngenite K2Ca(SO4)2• H2O 28.7 2.58

Accessory non-potassium minerals

Anhydrite CaSO4 0 2.98

Bischofite MgCl• 6H2O 0 1.59

Blödite Na2Mg(SO4)2• 4H2O 0 2.23

Dolomite CaMg(CO3)2 0 2.86

Epsomite MgSO4• 7H2O 0 1.68

Gypsum CaSO4• 2H2O 0 2.30

Halite NaCl 0 2.17

Hexahydrite MgSO4• 6H2O 0 1.76

Kieserite MgSO4• H2O 0 2.57

Löweite Na12Mg7(SO4)13• 15H2O 0 2.36-2.42

Tachyhydrite CaMgCl6• 12H2O 0 1.67

Vanthoffite Na6Mg(SO4)4 0 2.69
Chapter 1 7

Table 1-2. Select areas of potash exploration and development in eastern Europe and Asia since 2000.

[—, no data]

Project Country Basin Company Reference

Western Qaidam Basin China Qaidam — Ourchemical (2011), 

Xi’an Center of Geological

Survey (2008)

Hanumangarh-Mahajan-Punrasar India Nagaur-Ganganagar Pebble Creek Mining Ltd.

(2008)

Pebble Creek Mining Ltd.

(2008)

Thongman Lao PDR Sakhon Nakhon-Vientiane China-Laos Minerals

Development and

Investment Corp. (2010)

Chinese Academy of

Sciences (2010)

Satimola Kazakhstan Pricaspian Satimola, Ltd. (2011) Agapito Associates Inc.

(2011)

Uvs Nuur Mongolia, Russia Uvs Nuur (Tuva) General Mining

Corporation Ltd. (2011)

General Mining

Corporation Ltd. (2009)

Gremyachinsk Russia Pricaspian EuroChem (2009) Environmental Resources

Management (2009)

Tajikistan project Tajikistan Central Asia Salt Basin Mineral Mining PLC

(2011)

Newswire Today (2011)

Udon and Somboon Thailand Sakhon Nakhon Asia Pacific Potash Corp.

(2011)

Lomas (2002)

Karlyuk (Garlyk) Turkmenistan Central Asia Salt Basin Belgeologia (2010) Belarusian Telegraph

Agency (2010)

Tyubegatan Uzbekistan Central Asia Salt Basin Western Ural Machine

Building Concern

ITE Gulf FZ LLC (2010)

The USGS global potash assessment distinguishes two 

end-member subtypes of potash-bearing evaporite salt—

stratabound deposits and halokinetic deposits. Stratabound 

deposits (appendix A) are extensive and tectonically 

undisturbed. These deposits vary in size and can underlie 

areas ranging from tens to hundreds of thousands of square 

kilometers. The maximum deposit size in each basin is limited 

by the size of the basin at the time of deposition, but in some 

places, only very small deposits may be present in extremely 

large basins, so basin size is not a reliable predictor of potash 

deposit size.

Deep burial, active tectonics, and regional faulting can 

result in halokinesis—salt flowage that can form salt structures 

such as brachyanticlines, salt walls, folds, and diapirs, 

localized thickening and thinning of potash and salt, repetition 

of beds, and other disruptions, including loss of original 

potash deposition. Halokinetic deposits (appendix B) contain, 

on average, smaller tonnages than stratabound deposits, 

although halokinetic deposits exceeding a billion metric tons 

are possible.

For the USGS global potash assessment, quantitative 

estimates of undiscovered potash resources in stratabound 

deposits were made using an adaptive geometric estimation 

(AGE) method (summarized in appendix C). Quantitative 

estimates of undiscovered potash resources in halokinetic 

deposits were made using the three-part form of assessment of 

Singer and Menzie (Singer, 1993; Singer and Menzie, 2005). 

The CASB hosts both stratabound and halokinetic potash 

occurrences; halokinesis is more prevalent in the eastern 

CASB and the original stratabound nature of the deposit is 

largely, if not completely, preserved in the western part of the 

basin. This range of deposit types allowed us to investigate 

and compare the newly developed AGE method with the 

three-part form of assessment (Singer and Menzie, 2005).

For purposes of potash resource evaluation, we divided 

the CASB into three tracts (figure 1-1): (1) the Gissar tract 

(chapter 2) composed of uplifted and, in places, deformed 

sedimentary rocks that form the Gissar Range and its buried 

extension south-southwest to the Repetek Fault; (2) the 

Amu Darya tract (chapter 3) that consists of a largely flat-lying 

and minimally-deformed sedimentary sequence to the west of 

the Gissar Range; and (3) the Afghan-Tajik tract (chapter 4) 

composed of downdropped, deeply buried, deformed, and 

compressed sedimentary rocks to the east of the Gissar 

Range. Detailed descriptions of the assessment processes and 

assessment results for these three tracts are described in the 

following chapters of this publication.
8 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Geologic Overview

The Jurassic CASB comprises part of the Amu Darya 

Basin in the west and the Afghan-Tajik Basin in the east, 

which are separated by the Miocene Gissar Range (fig. 1-1). 

The salt basin is physically delimited by the North Afghan and 

Mary-Serakh Highs to the southwest, the Kyzyl Kum Plateau 

and Alai Mountains to the north, and the Pamir Mountains and 

Hindu Kush to the east (fig. 1-3).

Basin History, Tectonics, and Structure

The Miocene Gissar Range is a large, broad anticlinorium 

trending roughly N20E that uplifted basinal sedimentary rocks 

at least 1,000 meters (m) above their pre-deformation positions 

(Ulmishek, 2004; Steinshouer and others, 2006) and forms 

the divide between the modern Amu Darya and Afghan-Tajik 

Basins. The westernmost Amu Darya Basin pinches out 

gradually to the northwest; this boundary is ill-defined in the 

scientific literature, despite extensive oil and gas exploration 

during the past half century. The Afghan-Tajik Basin was 

deformed by block tectonics during evaporite deposition and 

most of the basin has been folded and compressed by as much 

as 50 percent in an east-west direction in southern Uzbekistan 

and southwestern Tajikistan. The deepest parts of the basin 

are in Tajikistan and contain more than 10 kilometers (km) 

of sedimentary rock. Marginal structural steps, including the 

North Afghan High, surround the depression and are uplifted 

as much as 3–8 km relative to the deepest parts of the basin 

(Klett and others, 2006).

Much of the development of the CASB and its 

subsequent modern basins has been related to the movement 

of the Eurasia, Africa, and Indian continental plates and 

accretion of various terranes (Ulmishek, 2004). Major 

events include (1) compression caused by the closing of the 

Paleotethys Ocean in the late Carboniferous to early Permian 

(Cassard, 2006); (2) extensional rifting and continental 

breakup in the late Permian to Triassic; (3) collision and 

associated deformation of the Cimmerian Block with Eurasia; 

(4) extension from Early to Middle Jurassic; (5) Middle 

Jurassic to Early Cretaceous formation of island arcs, passive 

margins, and postrift sags that caused marine transgression and 

deposition of continental and marine sediments; (6) movement 

of microcontinents in the Neotethys Ocean through the 

early Paleogene; and finally, (7) renewed compression and 

closing of the Neotethys Ocean (Cassard, 2006; Klett and 

others, 2006).

Deformation affecting the CASB during the basinal stage 

of development (Jurassic through Paleogene) is characteristic 

of block tectonics (Klett and others, 2006). Structural 

highs, such as the North Afghan High, experienced slower 

subsidence and occasional upward movements that resulted in 

local disconformities and absence of parts of the sedimentary 

rock sequence (Ulmishek, 2004). This deformation is most 

evident in the Gissar and Afghan-Tajik tracts. In contrast, 

evaporites in the Amu Darya tract have remained relatively 

undeformed since original deposition.

Basin Stratigraphy

The basement of the CASB is an accreted terrane formed 

during the Variscan Orogeny (Carboniferous to Permian) 

composed of deformed and metamorphosed Paleozoic rocks 

(Ulmishek, 2004). These units are overlain by upper Permian 

to Triassic rift graben fill, which in turn is overlain by Lower 

to Middle Jurassic rocks that are largely continental and 

are commonly coal bearing. Deep-water marine carbonate 

deposition dominated during the Callovian (Middle Jurassic) 

until evaporites were deposited in Kimmeridgian-Tithonian 

(Late Jurassic) time. Deposition of clastic marine rocks, with 

some continental sedimentary rock intervals, dominated from 

the Early Cretaceous through Paleogene (Ulmishek, 2004), and 

evaporites are distributed throughout the stratigraphic section.

Although a few references consider part of the thick 

evaporite deposits to be Lower Cretaceous Almurad Formation 

(Baikov and Sedletskiy, 2001), the majority of literature 

available to us considers the extensive potash-bearing salt 

deposition to be contained exclusively in the Upper Jurassic 

(Kimmeridgian-Tithonian) Gaurdak Formation. All known 

reserves, with the possible exception of parts (or all) of the 

Okuzbulak and Khodzhaikan occurrences (described in 

chapter 2; see Rayevskiy and Fiveg, 1973), are considered 

Jurassic in age. Within the CASB, all potash-bearing salts are 

assigned to the Jurassic Gaurdak Formation for the purposes 

of this assessment; we do not have enough information to 

definitively distinguish potash that might be in the Lower 

Cretaceous Almurad Formation. In most places, the Gaurdak 

section consists of five distinct evaporite layers (from top to 

bottom): (1) upper anhydrite, (2) upper halite, (3) intermediate 

anhydrite, (4) lower halite, and (5) carbonate-anhydrite 

(Gavril’cheva, 1981; Gavril’cheva and Pashaev, 1993; Baikov 

and Sedletskiy, 2001).

The maximum thickness of the Gaurdak Formation 

is about 1,200 m (Vysotskiy and others, 1988; Baikov 

and Sedletskiy, 2001). The total volume of the Gaurdak is 

estimated to be 121,000 cubic kilometers (km3), with halite and 

potassium salt composing as much as 33 percent of the total 

volume (Baikov and Sedletskiy, 2001). Basin-wide stratigraphy 

(fig 1-4) (Ulmishek, 2004) shows that Gaurdak Formation 

evaporites occur throughout the basin and are thickest in the 

vicinity of the Gissar Range in the central part of the CASB. 

Numerous gas and occasional oil deposits are reported 

throughout the Amu Darya Basin, both above and below the 

salt horizons of the Gaurdak Formation. Non-potash-bearing 

parts of the Gaurdak Formation extend at least 350 km west 

and 450 km northwest of the contoured “33 percent salt” limit 

of Steinshouer and others (2006) that is shown in fig. 1-2.
Chapter 1 

9

H I N D U K U S H

M O U NT A I N S

U N T A I N S

P

MA

R

I

I N

MALAY-BAGADZHA UPLIFT

A L A I M O

R G A B B A S

U S T E P

M U

B U K H A R A S T E P C H A R D Z H O

Kulyab

Konduz

Mazar-E-Sharif

Termez

Gaurdak

Mary

Bukhara

Navoi

Samarkand

Dushanbe

Chardzhou

Karshi

UZBEKISTAN

TURKMENISTAN

AFGHANISTAN AKIS P

AN T

TAJIKISTAN

KYRGYZSTAN

GISSAR RANGE

MARY-SERAKH HIGH

KYZYL KUM PLATEAU

NORTH AFGHAN HIGH

Amu

Darya

River

72° E 68° E 64° E

40° N38° N36° N

Political boundaries from U.S. Department of State (2009).Albers Equal Area Projection.Central meridian, 64° E., latitude of origin, 39° N.

EXPLANATION

Assessment tract boundary

0 100 200 KILOMETERS 500 50 100 MILES

150

CAsia_Fig1-3 gjo

Figure 1-3. Map showing the three assessed tracts of the Central Asia Salt Basin (CASB) compared with modern geographic features on a Landsat image.
10 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Salt and Potash

The evaporite section in the CASB is best described 

in the Amu Darya Basin and Gissar Range areas; it is rarely 

exposed in the Afghan-Tajik Basin. Petroleum exploration 

has been largely confined to the periphery of the AfghanTajik Basin. According to Baikov and Sedletskiy (2001), the 

uppermost evaporite “package” (upper anhydrite, #1) may 

be Early Cretaceous in age, but this tentative Cretaceous age 

is copied from a single Baikov paper dating from 1974. It is 

unclear if any of the mineralized rock is Early Cretaceous, 

as the majority of available information indicates that potash 

mineralization occurred in the Late Jurassic, but two deposits 

may contain potash of earliest Cretaceous age. For the 

purposes of this assessment, all potash is assumed to be related 

and Late Jurassic in age, but the assessment of undiscovered 

resources should also be valid for any Late Jurassic-Early 

Cretaceous salts in the basin. Russian literature acknowledges 

that reporting on potash is inconsistent and incomplete (Popov 

and Osichkina, 1973), as it was incidental to oil and gas 

exploration in many parts of the CASB.

400–700

Sandstone 2 Salt and package number

Shale Upper Permian-Triassic

 clastic rocks 

Carbonate rocks

Pre-Permian basement

Anhydrite Thickness, in meters

EXPLANATION

Foredeep

Kopet-Dag 3,000−8,000 1,400 1,300 1,200 1,450 1,050 900

300

MalayBagadzha 

Uplift 160−590 900−1,200 1,100 800−1,600 <2,000

 2

 4

1,000−8,000

Gaurdak Fm.

2,500−8,000 1,800 2,000 1,000−1,270 1,300−1,430 <600 <1,500

Murgab

Basin 

 2

 4

600 100−650 650−1,200 400−700 1,500 <900

Chardzhou

Step

280−660 0−600 450−950 0−550

Bukhara

 Step

0−320

Neogene

Paleogene

Upper 

Cretaceous

Lower 

Cretaceous

Upper Jurassic

Middle Jurassic

Lower Jurassic

Upper 

PermianTriassic

Pre-Permian

CAsia_Fig1-4 gjo2

Figure 1-4. Stratigraphic columns showing generalized stratigraphy of the central and western Central Asia 

Salt Basin (CASB) (adapted from Ulmishek, 2004). Upper Jurassic Gaurdak Formation evaporite deposits are 

labeled, and potash-hosting, predominantly salt-bearing units within it are numbered. Potash locations adapted 

from Gavril’cheva and Pashaev (1993). Column locations are not available from original sources, but approximate 

locations labeled above columns are mapped in fig. 1-3.
Chapter 1 11

Table 1-3. Estimates of potash in undiscovered deposits in the Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and 

Afghanistan.

[km, kilometer; km2, square kilometer; Bt, billion metric tons; NA, not applicable]

Tract name Coded_ID Type of 

assessment

Assessment 

depth

(km)

Tract

area

(km2)

Known potash 

resource 

(Bt K2O)

Mean estimate 

of undiscovered 

potash resources

(Bt K2O)

Median estimate 

of undiscovered 

potash resources 

(Bt K2O)

Consensus 

(Bt K2O)

Gissar 142mxK0005a AGE 3 26,669 1.63 27.9 25.3 NA

Gissar 142mxK0005a Three Part 3 26,669 1.63 0.47 0.39 1 to 16

Amu Darya 142sbK0005b AGE 3 40,224 0 41.1 37.8 38

Afghan-Tajik 142haK0005c Qualitative 3 68,382 0 NA NA NA

Total 39 to 54

Table 1-4. Statistics for grade and tonnage model for halokinetic potash-bearing salt deposits.

[See appendix D; Mt, million metric tons]

Distribution Number of 

deposits Mean

Quantiles

90 50

(median) 10

Tonnage (Mt) lognormal 25 343.4 39.4 152.9 1,153

Grade (percent K2O) normal 25 16.5 9.2 15.8 24.7

Most known halite deposits lie within the southeastern 

part of the Gaurdak Formation, which was outlined by 

Steinshouer and others (2006) as “33 percent salt” (fig. 1-2); 

the eastern boundaries of this salt area are not well defined and 

should extend east to include known salt domes that have been 

characterized as Jurassic in age (Vysotskiy and others, 1988; 

Bekker, 1996). The Gaurdak Formation west and northwest of 

the Amu Darya tract is not included in this assessment because 

only anhydrite, carbonates, and terrigenous sedimentary rocks 

(not potash-bearing) are shown in stratigraphic sections. 

Most potash is in the upper halite (package 2; Zharkov and 

others, 1982a, 1982b; Gavril’cheva and Pashaev, 1993) of the 

Gaurdak Formation (fig. 1-4), which has not been discovered 

outside the three delineated tracts of this study.

Potash in the CASB occurs as the minerals sylvite and 

carnallite (Petrov and Chistyakov, 1964; Rayevskiy and Fiveg, 

1973; Sedletskiy and Derevyagin, 1980). Soluble sulfates of 

potassium, as well as sulfates of sodium and magnesium, are 

absent from the basin (Osichkina, 1978).

Assessment

The two westernmost tracts within the CASB, Amu 

Darya and Gissar, were evaluated using one or both of 

the global potash assessment methods (table 1-3). Tracts 

were delineated based on parameters of stratabound and 

halokinetic potash-bearing salt deposit models (appendixes A 

and B). Tracts permissive for halokinetic potash-bearing 

salt deposits were evaluated using the standard USGS 

three-part form of assessment (Singer, 1993; Singer and 

Menzie, 2005, 2010), and a grade and tonnage model was 

developed for this assessment (appendix D and table 1-4). 

Tracts permissive for stratabound potash-bearing salt deposits 

were evaluated using the AGE method developed for use 

with these deposits (appendix C). We prepared quantitative 

estimates for undiscovered potash resources in the Gissar 

and Amu Darya tracts, however, the assessment team had 

insufficient information to quantify undiscovered resources 

within the Afghan-Tajik tract. Moreover, geologic profiles of 

Bekker (1996) indicate that, unless uplifted by structural and 

halokinetic processes, most Jurassic sediments that might host 

potash are too deep for economic extraction. 

Assessment Depth

An assessment depth limit of 3 km was used for potash 

tracts in the CASB; this is the standard depth limit used by the 

USGS to define potash worldwide.
12 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Assessment Methods

The three-part form of assessment described by Singer 

(1993) and Singer and Menzie (2005, 2010) was used to 

estimate undiscovered potash resources in halokinetic 

deposits. In this method, an expert panel compared known 

deposits and permissive geology with a halokinetic 

potash-bearing salt deposit model, estimated the number of 

undiscovered deposits remaining in the tract, and then used 

a Monte Carlo simulation to combine a grade and tonnage 

model with the estimated number of deposits to arrive at a 

tonnage distribution for undiscovered potash resources. For 

potash, this is the remaining in-place K2O value.

The AGE method (appendix C) was developed to 

estimate undiscovered potash resources in stratabound 

potash deposits. This method does not estimate undiscovered 

deposits, rather, it calculates a geometric estimate of in-place 

volumes and (or) tonnages of potash. The initial in-place 

values are then modified using simulations to estimate 

unknown or incompletely known parameters, such as grade 

and unmineralized areas (anomalies) caused by original nondeposition, replacement, dissolution, and erosion. Tonnages of 

known deposits are subtracted from this estimate.

Assessment and Results Summary

The Gissar tract, where mineralization is transitional, 

shows features of both halokinetic and stratabound potashbearing salt deposits and was assessed for undiscovered 

potash resources using both assessment methods (table 1-3). 

Most of the available literature (for instance Vysotskiy and 

others, 1988) describes sedimentary rocks disrupted by 

tectonics and halokinesis; available information suggests 

these effects are highly variable throughout the uplifted Gissar 

tract. Numbers of undiscovered halokinetic deposits were 

estimated using a halokinetic potash-bearing salt descriptive 

model (appendix B), and were combined with the grade and 

tonnage model (table 1-4) to estimate tonnage distribution 

for undiscovered potash in halokinetic deposits for the 

Gissar tract. A number of factors (see chapter 2) suggest 

that the median of this estimate significantly underestimates 

undiscovered resources in the Gissar tract.

Undiscovered potash resources of the Gissar tract were 

also estimated using the AGE method. The tract boundary 

was interpolated from widely-dispersed no-potash-present 

drill-hole data, reports, and enclosed potash thicknesses of 

1 m or greater as estimated from limited drill hole and point 

location data; this allowed in-place volume calculations to be 

made. A distribution of reported grades in the CASB, from 

potash intervals 1 m and greater in thickness, was randomly 

sampled and used to compute density and tonnage. This 

in-place tonnage was modified to account for unmineralized 

areas and postdepositional potash losses caused by erosion 

and other processes. The estimate for stratabound deposits was 

significantly larger than the estimate for halokinetic deposits, 

but it may be an overestimate (see chapter 2). The best 

estimate of undiscovered resources is probably between 1 and 

16 Bt of potash as K2O (table 1-3).

An estimate of undiscovered potash was also made 

for the Amu Darya tract. The stratabound potash-bearing 

salt model was determined to be the best fit for the tract 

and therefore the AGE method was used to produce the 

estimate (table 1-3). Within the Afghan-Tajik tract, where 

Jurassic evaporites are commonly deeply buried, there is 

potential for undiscovered potash in halokinetic deposits 

upraised by diapirs and block tectonics. Data for this tract 

were not adequate for a quantitative assessment; therefore, 

the assessment included delineation of the area within 

which potash could occur and a qualitative evaluation of 

potash potential. 

Summary

 In 2013 (the most recent year for which complete 

information is available), world potash production was 

34.5 million metric tons (Mt) of K2O-equivalent. Canada 

was the leading producer of potash (10.1 Mt K2O-equivalent 

in 2013), followed by Russia, China, Belarus, Germany, 

Israel, Jordan, and Chile (Jasinski, 2015). Of the 12 known 

potash-producing countries in 2013, 8 produced 1 Mt or more; 

production in the United States was slightly less than 1 Mt, 

and production in Brazil, Spain, and the United Kingdom was 

less than 500,000 metric tons each (Jasinski, 2015).

Known potash resources in the CASB consist of 

8.020 billion metric tons (Bt) of mineralized potash rock 

containing 1.63 Bt of K2O, all in the Gissar tract. Our 

assessment indicates that between 39 and 54 Bt of K2O exists 

in undiscovered deposits within the Gissar and Amu Darya 

tracts together (table 1-3). There is only one previous estimate 

of total resources for the CASB (or a portion thereof)—Zhang 

and others (2005) estimated a total resource of 20 Bt for the 

Gaurdak potash basin, but it is not clear how they defined area 

boundaries or exactly what they meant by “potash resources.” 

Based on incomplete table data, it is likely that Zhang and 

others (2005) estimated 20 Bt of ore in the explored potash 

area of the central Gissar Range. Our estimate of undiscovered 

potash for that area is larger and is for a defined area that 

includes the Gissar Range and the area between the uplifted 

range and the Repetek Fault to the south-southwest.
Chapter 2. Potash-Bearing Salt Assessment for the Gissar Tract 

(142mxK0005a)—Turkmenistan, Uzbekistan, Tajikistan, and 

Afghanistan

By Jeff Wynn,1 Greta J. Orris,2 Pamela Dunlap,2 and Mark D. Cocker,2 with contributions from Bruce R. Lipin,3

Robert J. Ryan,4 Mirosław Słowakiewicz,5 Gregory T. Spanski,6 and Chao Yang7

1

U.S. Geological Survey, Vancouver, Washington, United States.

2

U.S. Geological Survey, Tucson, Arizona, United States.

3

U.S. Geological Survey, Reston, Virginia, United States.

4

Nova Scotia Department of Natural Resources, Nova Scotia, Canada.

5

Polish Geological Institute–National Research Institute, Warsaw, Poland.

6

U.S. Geological Survey, Denver, Colorado, United States.

7

Saskatchewan Energy and Resources, Regina, Saskatchewan, Canada.

Introduction 

A quantitative assessment of undiscovered potash 

resources was conducted for the Gissar tract of the Central 

Asia Salt Basin (CASB). This tract encompasses the 

Gissar Range, and extends northeast to southwest across 

the Uzbekistan-Turkmenistan border, with small areas in 

Tajikistan and Afghanistan (fig. 2-1). This tract contains the 

only known potash reserves and resources of the CASB, 

including the only operating potash mine at Tyubegatan. The 

Upper Jurassic (Tithonian) potash and host salt have been 

identified throughout the tract in a variety of salt structures 

and, in the areas of the Karabil and Karlyuk deposits, in 

undeformed pockets of stratabound potash-bearing salt. 

Documented potash reserves and resources in this tract 

are shared among 10 deposits and there are 18 additional 

known occurrences.

Potash deposits and occurrences within the Gissar tract 

are a mix of halokinetic and stratabound mineralization, 

that is, the area is probably transitional between the two 

end members. Because of this mix of mineralization styles, 

this study estimated undiscovered resources using two 

methods—one suited for halokinetic potash deposits and the 

other to stratabound potash deposits. Deposits in this tract 

are typically in the uplifted upper limbs of brachyanticlines 

and domes, where potash may be concentrated and thickened 

or disrupted by tectonic folding; this implies that halokinetic 

potash-bearing salt is the appropriate deposit type. However, 

the halokinetic deposit model and the three-part form of 

assessment of Singer and Menzie (2005, 2010) produce a 

mean estimate that appears to significantly underpredict 

undiscovered potash resources. This underprediction likely 

results from mineralized deposits that are transitional between 

stratabound and halokinetic potash-bearing salt. At least two 

deposits within the tract are relatively undisturbed and, in 

that sense, are stratabound, though they are not contiguous 

with any other deposits. The stratabound deposit model and 

the adaptive geometric estimation (AGE) method were used 

to estimate the in-place potash resource assuming the potash 

is continuous and not significantly impacted by halokinesis. 

Because the deposits in the tract are transitional between the 

deposit types, the undiscovered resource size probably lies 

between the halokinetic and stratabound estimates. Results of 

both estimates are presented in table 2-1.

Location

The Gissar tract encompasses the Gissar Range and its 

downdip extensions, and lies between the Amu Darya tract 

to the west (chapter 3) and the Afghan-Tajik tract to the east 

(chapter 4). It extends north to the flanks of the Kyzyl Kum 

Plateau, and to the south beyond the Amu Darya River into 

southeastern Turkmenistan and northern Afghanistan.

Basin History

Although the Gissar tract straddles the boundary between 

the modern Amu Darya and Afghan-Tajik Basins, the original 

Jurassic salt basin was continuous for more than 200 km east 

and west of this tract. Structural events that postdate the salt 

deposition, including Miocene uplift of the Gissar Range, 

differentiated the two basins. The Amu Darya tract, to the west 

of the Gissar Range, is relatively undeformed compared to 

the Afghan-Tajik tract to the east, which is highly deformed 

and deeply buried by east-west compression that has been 

ongoing since at least the Miocene. The Gissar tract is distinct 

from neighboring tracts because Miocene uplift has raised 

potash-bearing horizons to shallow levels where they are more 

easily discovered.
14 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan Figure 2-1. Map showing location of the Gissar tract (142mxK0005a), Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan, and known potash deposits and occurrences. TURKMENISTAN UZBEKISTAN TAJIKISTAN AFGHANISTAN Termez Karshi Mazar-E-Sharif Akbash Tyubegatan South Lyalimkan Kugitang Karabil Karlyuk Okuzbulak North Gaurdak Gaurdak Kyzylmazar Mobik Adamtash Kyzylbayrak East Karail Karabay Gumbulak Karail Kantau Belesyainak Akrabat Khamkan Kokmiyar Tigarin Chasranta Etymdag Khodzhaikan Uzunkuduk Donguzsyrt 66° E 68° E 38° N 37° N AFGHANISTAN UZBEKISTAN

TURKMENISTAN

40° N

35° N

60° E 70° E

0 20 40 60 80 KILOMETERS

0 20 40 MILES

Tract 142mxK0005a, Gissar tractOther potash tract

EXPLANATION

Potash deposit

Potash occurrence; occurrences associated with other tracts are  shown in gray

Political boundaries from U.S. Department of State (2009).Albers Equal Area Projection.Central meridian, 65° E., latitude of origin, 30° N.

CAsia_Fig 2-1 gjo2

Area of map
Chapter 2 15

Salt

The Late Jurassic basin of the CASB includes the five 

major stratigraphic units of the Gaurdak Formation (figs. 2-2A, 

2-2B), of which the second and fourth units host potash 

(Gavril’cheva, 1981). In the Gissar tract, Jurassic salt is 

present in brachyanticlines and other salt structures resulting 

from Miocene uplift of the Gissar Range. Some salt and 

potash in the southeastern part of this tract has been attributed 

to the Lower Cretaceous Almurad Formation (Rayevskiy and 

Fiveg, 1973). Because of extremely limited and conflicting 

information on salt ages, the assessment team could not 

distinguish Cretaceous salt from Jurassic salt. Therefore, 

for the purposes of this assessment, Upper Jurassic and any 

possible Lower Cretaceous salt are assumed to result from the 

same evaporite event.

Assessment

The goal of the U.S. Geological Survey (USGS) potash 

assessment in the CASB was to estimate undiscovered potash 

as potassium oxide (K2O) resources. This section describes the 

steps used to estimate undiscovered potash within the Gissar 

tract, including data collection and analysis, followed by 

identification of appropriate deposit model(s). The geology of 

the area is complex and poorly understood. Postmineralization 

tectonics and subsequent salt movement have shaped deposit 

features so that some fit the halokinetic potash-bearing salt 

deposit model and others are a better fit with the stratabound 

potash-bearing salt deposit model (appendixes A and B). 

Many deposits and occurrences within this tract are no longer 

flat-lying and continuous over large distances. A few deposits, 

such as Karabil, appear to be flat-lying and continuous within 

small areas that have been protected from postmineralization 

processes that disturbed other deposits and occurrences. The 

assessment team considered splitting this tract, but decided 

to keep the tract intact because (1) the entire tract shares a 

common depositional and postmineralization geologic history; 

(2) the southwestern part of the tract, largely covered and not 

well explored, is likely to contain the same mix of deposit 

characteristics at the same scales; and (3) subdividing would 

result in small (single mine and deposit-specific) areas relative 

to the assessment scale of 1:1,000,000.

Delineation of the Permissive Tract

A starting point for defining the Gissar tract was the 

Gissar Range, where all known deposits are found, along 

with potash-prospective zones 1 and II of Fedin (1981) 

and Vysotskiy and others (1988, their figure 73). The tract 

boundary was refined by excluding all geologic units older 

than Middle-Upper Jurassic (Gaurdak Formation) in the 

vicinity of the Gissar Range on the Central Asia Geologic 

Map (Seltmann and others, 2005). Next, the tract boundary 

was extended southwestward beyond the Upper Jurassic 

evaporites to follow the edge of the Beshkent Depression 

until it intersected the Repetek Fault Zone (fig. 2-3) and the 

Donguzsyrt occurrence (see fig. 2-1). The tract was further 

extended 3 km past the easternmost mapped Jurassic rock 

outcrops to include covered parts of Gissar Range, though 

some of the potash in the area may lie below the 3-km 

assessment depth limit. The tract was extended to the north 

until pre-Jurassic rocks were encountered, and then extended 

westward 3 km downdip below post-Jurassic rocks mapped 

at the surface, in order to enclose all potential potash-hosting 

geologic units in the tract. Finally, tract boundaries were 

modified where necessary to include all appropriate deposits 

and occurrences.

Definition of Resources

Known deposits (table 2-2) were considered to be those 

with documented reserves or resources in categories A, B, C1, 

or C2 of the Russian classification system (see Henley, 2004). 

Table 2-1. Summary of potash resource assessment results for the Gissar tract, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan.

[km, kilometer; km2, square kilometer; Bt, billion metric tons; —, no data]

Date of 

assessment

Assessment 

method

Deposit

type

Assessment 

depth

(km)

Tract

area

(km2)

Known potash 

resource 

(Bt K2O)

Mean estimate 

of undiscovered 

potash resources

(Bt K2O)

Median estimate 

of undiscovered 

potash resources 

(Bt K2O)

Consensus 

(Bt K2O)

May 2009 Three-part

estimation

Halokinetic 3 26,669 1.63 0.47 0.39 1 to 16

June 2010 Adaptive

geometric

estimation

(AGE)

Stratabound 3 26,669 1.63 27.9 25.3 —
16 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan



AFGHANISTAN

TURKMENISTAN

UZBEKISTAN

TAJIKISTAN

NORTH MUBAREK FAULT

1

2

3

4

Gaurdak

Murgab Basin

Mubarek 

Arch

Dengizkul Arch

BUKHARA FAULT

KARSHI FAULT

Karabekaul Downwarp

ALBURZ-MORMUL FAULT

Beshkent

 Depression

SOUTHWEST GISSARS

FOLD-THRUST BELT

 MangyshlakSouth Gissar Fault Zone

FAULT

REPETEK FAULT ZONE

DARYA

AMU

64° E 66° E 68° E

39° N

38° N

37° N

64° E 68° E

38° N

36° N

TAJIKISTAN

UZBEKISTAN

AFGHANISTAN

Political boundary source: U.S. Department of State (2009).

Projection: Asia North Albers Equal Area Conic.

Central meridian 65° E; latitude of origin 30° N.

20 40 60 80 KILOMETERS

0 20 40 MILES

0

Fault—Deep regional

Fault—Undifferentiated

Minor structure

Structure

Stratigraphic column correlation

 line with drill-hole location and 

 number

Tract 142mxK0005a, Gissar tract

1

EXPLANATION

CAsia_Fig 2-2A gjo2

A

Area of map

Figure 2-2. Map showing location of the Gissar tract (142mxK0005a), four drill holes,and corresponding stratigraphic columns. A, 

structural features influencing the Gissar tract (adapted from Zharkov and others, 1982a, and Blackbourn, 2008) and location of four drill 

holes. B, section of the Upper Jurassic Gaurdak Formation (Zharkov and others, 1982a). Drill holes 1 and 2 approximately mark eastern 

edge of Beshkent Depression. No potash was reported in these two drill holes by Zharkov and others (1982a), but it was reported to be 

present by Gavril’cheva (1981).
Chapter 2 17

2,900

3,000

3,100

3,200

3,400

3,300

2,500

2,400

2,300

2,600

2,700

2,500

2,600

2,400

2,300

2,200

2,100

2,700

2,800

2,900

3,000

1

2

3

4

2

2

2

2

2

2

2

2

2

2

2

2

4

4

4

4

5

5

5

5

1

3

3

3

3

1

1

1

Potash

Depth, in meters

4

5

EXPLANATION

1

2

3

Upper carbonate

Upper salt

Middle carbonate

Lower salt

Basal carbonate

2,100

1 Drill-hole number

B

CAsia_Fig 2-2B gjo

Figure 2-2.—Continued

Table 2-2. Known deposits of potash within the Gissar tract, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan.

[Mt, million metric tons; reserve and resource categories A, B, and C are described in the text]

Name Latitude Longitude Reserves, resources

(Mt ore rock, in place)

Grade 

(percent 

K2O)

Contained

K2O

(Mt)

References

Akbash 38.417 66.55 C2=266.5 12 31.98 Fedin (1981)

Gaurdak 37.588 66.346 A+B+C1=106.3 18.9 20.09 Fedin (1981)

Karabil 37.820 66.071 C2=3,500 21.65 757.75 Rayevskiy and Fiveg (1973); Fedin (1981)

Karlyuk 37.659 66.234 A+B+C1=2,015; C2=1,175 19.5 622.05 Levine and Wallace (2001); Fedin (1981)

Kugitang 37.844 66.393 C2=144 9.8–15.9 18.5 Rayevskiy and Fiveg (1973); Fedin (1981)

Kyzylmazar 38.54 66.883 A+B+C1=1.7; C2=2.2 9.9 0.39 Rayevskiy and Fiveg (1973); Fedin (1981)

North Gaurdak 37.920 66.209 C2=3.8 19.5 0.74 Rayevskiy and Fiveg (1973); Fedin (1981)

Okuzbulak 37.930 66.379 A+B+C1=96 18.3 17.57 Rayevskiy and Fiveg (1973); Fedin (1981)

South Lyalimkan 38.157 66.515 C2=24 19.9 4.78 Rayevskiy and Fiveg (1973); Fedin (1981)

Tyubegatan 37.435 66.340 A+B+C1=400.2; C2=285.6 22.4 153.62 Ashurmatov (2006); Uzbekistan Daily (2006); 

Fedin (1981)

Total 8,020.30 1,627.47
18 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

TURKMENISTAN

TAJIKISTAN

AFGHANISTAN

UZBEKISTAN

Termez

Mazar-E-Sharif

Karshi

66° E 68° E

38° N

37° N

KARABEKAUL 

TROUGH

Baisun Graben

Kafirnigan Mega Anticline

CHARDZHOU STEP

CHARDZHOU STEP

BESHKENT TROUGH

Andkhoy Uplift

North Afghan High

Repetek 

Fault Zone

Gissar

Obruchev Depression

North Karabil Trough

MURGAB BASIN

GISSAR RANGE

64° E 68° E

37° N

38° N TURKMENISTAN

UZBEKISTAN

AFGHANISTAN

TAJIKISTAN

Area of map

0 20 40 MILES

0 20 40 60 80 KILOMETERS

Potash deposit

Pre-Jurassic sedimentary 

 and crystalline basement

Fault zone

Tract 142mxK0005a, Gissar tract

Relative highs—Anticlines, 

 uplifts, and monoclines

Relative lows—Synclines, 

 depressions, and troughs

EXPLANATION

Political boundaries from U.S. Department of State (2009).

Albers Equal Area Projection.

Central meridian, 65° E., latitude of origin, 30° N.

CAsia_Fig 2-3 gjo2

Figure 2-3. Map showing structural provinces in and near the Gissar tract (142mxK0005a), Turkmenistan, Uzbekistan, 

Tajikistan, and Afghanistan, based on Steinshouer and others (2006). Note that structural uplifts and downwarps 

(depressions, troughs) are not necessarily reflected in modern topography.
Chapter 2 19

The Russian mineral resource categorization system divides 

mineral concentrations into seven categories in three major 

groups: fully explored reserves or resources (A, B, C1), 

evaluated reserves or resources (C2), and prognostic resources 

(P1, P2, P3). Category A is only distinguished from B by the 

amount of detail known about reserves (category B is based 

on less information), but both are roughly equivalent to the 

McKelvey classification of measured resources or proven and 

probable reserves. Reserves C1 and C2 are estimated with 

lower density gridding and trenching; C1 lies between B and 

C2, where C2 is estimated on the coarsest exploration grid. In 

the McKelvey classification, the Russian C1 and C2 may be 

equivalent to measured, indicated, and (or) inferred resources, 

or may be reserves. In the absence of specific definitions in the 

source literature, reserve and resource figures were assumed 

by the assessment team to represent in-place numbers for the 

purposes of the stratabound resource calculations.

Discovered Resources

All known potash deposits in the CASB (fig. 2-1, table 2-2) 

are within the Gissar tract. Ten potash deposits are recognized in 

this tract, and all deposits with reserves and resources lie within 

the Upper Jurassic (Oxfordian) Gaurdak Formation (fig. 2-4).

Summaries of known deposits are presented in the 

following report sections. Readers should note that many 

deposits and occurrences overlie locally recognized structures 

with the same names as the deposits. These structures are 

mentioned in deposit reports, but the extent of their areal 

coverages are not shown on maps. Mined potash-salt horizons 

are often not identified in the literature and are likely obscured 

by deformation. In the following report sections, any potash 

layers discussed are local to each particular deposit and do not 

correlate to the broader-scale numbering of Gavril’cheva (1981).

Akbash

The Akbash deposit (fig. 2-1, table 2-2) in Uzbekistan is 

approximately 20 km north of the Tyubegatan deposit in the 

central part of the Gissar tract. Two sylvinite (sylvite+halite) 

layers that are traceable from the Tyubegatan deposit were 

identified at this site during exploration drilling at depths 

ranging from 150 to 500 m (Sedletskiy, 1969; Rayevskiy and 

Fiveg, 1973). The upper potash layer is 3–3.5 m thick and 

contains 11.5–16.5 percent K2O; the lower layer is 2–11.4 m 

thick and contains 11.3–12.1 percent K2O (Rayevskiy and Fiveg, 

1973; Fedin, 1981).

Gaurdak

The Gaurdak deposit (fig. 2-1, table 2-2) in Turkmenistan 

is approximately 8 km north of the town of Gaurdak, in the 

central part of the Gissar tract. Potash mineralization is found on 

the northwestern flank of the northeastern part of the Gaurdak 

brachyanticline, which dips variably at angles ranging from 6° 

to 30°. Paleozoic granite and metamorphic rocks comprise the 

core of this brachyanticline at a depth of 926 m. The otherwise 

continuous Upper Jurassic and Lower Cretaceous sedimentary 

rocks on the northwest limb of the Gaurdak brachyanticline 

are abruptly displaced by varying distances that may be 

related to deformation of underlying Paleozoic rocks during 

brachyanticline formation.

In the Gaurdak area, the Gaurdak evaporite salt deposits 

can be divided into a lower rock salt, which does not contain 

potash, and a potash-bearing sequence. A transitional horizon 

between the units contains lenses and uneven impregnations 

of potash minerals. Two sylvinite lenses lie in the transitional 

horizon; one is 0.5 m thick, the other 1.5 m thick, with K2O 

contents of 18.4 percent and 17.6–18.0 percent, respectively.

The potash-bearing sequence of the Gaurdak Formation 

contains three persistent potash horizons with as many as 

seven potash beds separated by rock salt. Locally, these are 

called the “Lower II,” “Lower III,” and “Blue” horizons. The 

Lower II horizon consists of two sylvite (sylvite-carnallite 

in the south) layers, 2 and 3 m thick (total average thickness 

of 4 m), that range from 9.6 to 26.8 percent K2O (Sedletskiy, 

1969; Rayevskiy and Fiveg, 1973). The Lower III horizon lies 

higher in the stratigraphy, has a lower average K2O content 

(13.4–17 percent K2O), and contains less than 3 percent 

magnesium chloride (as carnallite). The Blue horizon is 

separated from the Lower III by 30–40 m of rock salt. This 

white and pink sylvite-bearing bed contains 13.7–24.5 percent 

K2O and is 1.5–5 m thick (Sedletskiy, 1969). Garrett (1996) 

reported considerable leaching of salts and gradational 

mineralization from north to south in the Gaurdak deposit—

from carnallitite (carnallite+halite), to carnallitite-sylvinite, to 

sylvinite, to halite.

Karabil

The Karabil deposit (fig. 2-1, table 2-2) in Turkmenistan 

is southeast of the town of Gaurdak in the central part of the 

Gissar tract. The deposit is on a brachyanticline, the northern 

and southern boundaries of which are cut by faults. The primary 

structural features of the deposit are the same as those at the 

Karlyuk deposit, though the potash-bearing stratum is somewhat 

thinner and deeper (Sedletskiy, 1969). Of ten potash layers, 

eight are relatively continuous sylvinite potash beds that contain 

a range of 16.1–27.2 percent K2O and an average 1 percent 

magnesium chloride (Rayevskiy and Fiveg, 1973). Potash layer 

4 is the most widespread with the most consistent thickness, but 

has a higher level of insoluble material than the other layers of 

interest. The central and western parts of this deposit are least 

disturbed by faulting and unfavorable hydrogeologic conditions 

(Rayevskiy and Fiveg, 1973).

Karlyuk

The Karlyuk deposit (fig. 2-1, table 2-2), discovered in the 

mid-1960s, is one of the largest in Turkmenistan. More than 

100 drill holes were reported to have penetrated the potash 

at this deposit (Rayevskiy and Fiveg, 1973). In 1983, a large 

solution mining pilot plant was operated at this site (Garrett, 

1996), but was soon discontinued.
20 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Political boundaries from U.S. Department of State (2009).

Albers Equal Area Projection.

Central meridian, 65° E., latitude of origin, 30° N.

66° E 66°30’ E

38° N

37°30’ N

0 5

0 5 10 15 20 KILOMETERS

10 MILES

Figure 2-5

TURKMENISTAN

UZBEKISTAN

AFGHANISTAN

Gaurdak

Karlyuk

Karabil

Kyzylmazar

Kugitang

South Lyalimkan

Khamkan

Akbash

Tyubegatan

North 

Gaurdak

Uzunkuduk

Okuzbulak

Khodzhaikan

UZBEKISTAN

64° E 66° E 68° E

38° N

36° N

UZBEKISTAN

TURKMENISTAN

AFGHANISTAN

TAJIKISTAN

Area of map

EXPLANATION

Quaternary-Paleogene sedimentary rock

Upper Cretaceous sedimentary rock

Lower Cretaceous sedimentary rock

Middle to Lower Jurassic sedimentary rock 

Upper to Middle Jurassic sedimentary rock

Potash concession

Tract 142mxK0005a, Gissar tract

Fault—Dashed where inferred

Location of figure 2-5

Central Asia fig 2-4 gjo2

Figure 2-4. Map showing geology and concession areas in the central part of the Gissar tract (142mxK0005a), Turkmenistan and Uzbekistan. 

Middle to Lower Jurassic rocks are older than potash-bearing salt of the Gaurdak Formation and have been removed from the tract

because they are not permissive for this deposit type. These areas are represented by the “anomalies” parameter in the adaptive geometric 

estimation process. This map is an interpolation of more detailed maps by Vysotskiy and others (1988, fig. 4) and Mirzakhanov (1989) with 

1:1,500,000-scale geology of Seltmann and others (2005) mineral deposits map of central Asia. Blue, dashed line outlines map area shown in 

figure 2-5.
Chapter 2 21

The deposit contains three main potash horizons with 

as many as 16 beds, lenses, and intercalations of potash 

salts with rock salt at depths of 200–1,200 m over an area of 

75 km2 (Sedletskiy, 1969). Three of the potash beds (locally 

labeled ninth, eighth, and seventh, counting up) are in the 

lower potash horizon of Gavril’cheva and Pashaev (1993) and 

contain most of the reserves. The mean grade of this horizon is 

more than 18 percent K2O, but carnallite is locally abundant. 

Carnallite-free sylvite makes up the seventh potash bed and is 

considered secondary in origin (Sedletskiy, 1969).

The overlying sixth potash layer is composed of 

carnallite-bearing sylvite and averages more than 5 m thick. 

The fourth and fifth beds contain sylvite, and have grades of 

14–15.5 percent K2O, and a combined thickness of 1.5–43 m 

(Sedletskiy, 1969).

The upper potash-bearing horizon is largely composed 

of individual thin lenses and intercalations of potash salts 

and is only persistent in the central part of the deposit. The 

first, second, and third potash beds are dominantly low-grade 

sylvinite (Sedletskiy, 1969).

Carnallite beds lie at the top of both the lower and 

upper potash horizons; they are locally referred to as the 

“middle carnallite” and “upper carnallite”. These beds contain 

6–28 percent magnesium chloride. The middle carnallite is 

missing in some parts of the Karlyuk deposit (Sedletskiy, 

1969; Rayevskiy and Fiveg, 1973).

Kugitang

The Kugitang deposit in Turkmenistan (fig. 2-1, 

table 2-2), is approximately 20 km south-southeast of the 

Tyubegatan deposit, in the central part of the Gissar tract. Six 

potash beds occur on the west limb of the Kugitang structure 

at depths of 500–550 m, but only three of these beds are 

persistent (Sedletskiy, 1969). The lowest bed is 0.7–2.2 m 

thick and consists of red sylvite with minor carnallite; the 

grade varies from 10.7 to 27.1 percent K2O (Sedletskiy, 1969; 

Rayevskiy and Fiveg, 1973).

The middle potash horizon consists of two potash seams 

separated by a thin intercalation of gray to pink rock salt 

(Rayevskiy and Fiveg, 1973). Like the lower horizon, the 

middle horizon consists of red sylvite with scattered orange 

carnallite. The thickness and grade of this horizon are highly 

variable and potash thickness rarely exceeds 3 m. The average 

grade ranges from 9.8 to 15.9 percent K2O (Rayevskiy and 

Fiveg, 1973). In places, the carnallite content is significant 

with some samples containing as much as 9.6 percent 

magnesium chloride. In these areas, the clay content may 

exceed 5 percent (Sedletskiy, 1969).

The upper potash horizon comprises one or two white to 

pink sylvinite layers intercalated with rock salt. Each potash 

layer is commonly 1 m thick or less, though in one drill hole, 

at least one layer exceeded a thickness of 3 m. The average 

potash grade is reported to range from 7.9 to 12.2 percent K2O, 

but rarely exceeds 9 percent (Sedletskiy, 1969; Rayevskiy and 

Fiveg, 1973). 

Kyzylmazar

The Kyzylmazar deposit (fig. 2-1, table 2-2) in 

Turkmenistan is 20 km north of the town of Gaurdak and 

less than 2 km south of the North Gaurdak deposit, in the 

central part of the Gissar tract. An unspecified number of 

sylvinite layers in the Gaurdak Formation lie at depths of 

85–250 m (Rayevskiy and Fiveg, 1973) at the north end of 

the Gaurdak brachyanticline (Sedletskiy, 1969). The potashbearing sequence is 5–50 m thick and contains an average of 

9.9 percent K2O (Rayevskiy and Fiveg, 1973; Fedin, 1981).

North Gaurdak

The North Gaurdak deposit (fig. 2-1, table 2-2) is in 

Turkmenistan, approximately 5 km north of the northernmost 

boundary of the Gaurdak deposit, in the central part of the 

Gissar tract. The area is a fault-bounded block of gently 

dipping rocks on the northwestern flank of a brachyanticline 

(Sedletskiy, 1969), the northern extension of the Gaurdak 

structure. One sylvinite layer (locally called “Lower II”) has 

been identified at this deposit. The potash layer has an average 

thickness of 3.3 m and contains an average of 19.5 percent 

K2O (Rayevskiy and Sedletskiy, 1969; Fiveg, 1973; 

Fedin, 1981).

Okuzbulak

The Okuzbulak deposit (fig. 2-1, table 2-2) in 

Turkmenistan is in the southern part of the Gissar tract 

about 20 km northwest of the point where Afghanistan, 

Turkmenistan, and Uzbekistan meet. The first discovery 

of potassium salts in the region was made here in the early 

1930s (Rayevskiy and Fiveg, 1973). The deposit is on a 

brachyanticline which is overturned to the north, and is part 

of the southeastern limb of the larger Kugitang structure. 

The northern limb of the brachyanticline dips at 50–70°, the 

southern limb at 25°.

Initial reports on potash age, and most of the available 

reports published since the early 1970s, classify the potash 

reserves and resources in this region as Jurassic in age and 

belonging to the Gaurdak Formation (Fedin, 1981; British 

Sulphur Corporation, 1984; Schultz and others, 2000). 

Potash is also reported to occur in the Lower Cretaceous 

Almurad Formation in some parts of this site (Rayevskiy and 

Fiveg, 1973).

The British Sulphur Corporation (1979, 1984) reports 

that two sylvinite beds, 12 m apart, locally occur at the top 

of a gypsiferous section at Okuzbulak and are latest Jurassic 

(Gaurdak) in age. The lower bed is 3.5 m thick and contains 

12.5–15.8 percent K2O; the upper bed is 2.5 m thick and 

contains 8–11 percent K2O. Rayevskiy and Fiveg (1973) 

also report two sylvinite beds. In this case, the lower horizon 

is reported to average 4 m thick and contain an average of 

9.9 percent K2O; the upper bed is reported to average 2.5 m 

thick with an average grade of 13.4 percent K2O.
22 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

South Lyalimkan

The South Lyalimkan deposit (fig. 2-1, table 2-2) in 

Turkmenistan is southwest of the Tyubegatan deposit in 

the central part of the Gissar tract. The two deposits are 

separated by a salt plug that is exposed in a diapiric structure 

(Sedletskiy, 1969). Elevated potassium contents were noted at 

this site as early as the mid-1930s and later exploratory holes 

identified a bed of sylvinite 3.9–6.9 m thick (average 5.6 m in 

the drill core) containing 11.5–29.6 percent K2O (Sedletskiy, 

1969; Rayevskiy and Fiveg, 1973).

Tyubegatan

The Tyubegatan deposit (fig. 2-1, table 2-2) is in 

the central part of the Gissar tract and straddles the 

Turkmenistan-Uzbekistan border. The deposit is on the 

gently dipping (15–20°) northwestern limb of the Tyubegatan 

brachyanticline (fig. 2-5), which is approximately 30 km 

long and as much as 12–15 km wide. The southeastern limb 

of the brachyanticline is steeply dipping (as much as 50°). 

Ancillary structures such as the Lyalimkan dome (fig. 2-5) and 

the Akbash salt dome (fig. 2-5) are on or adjacent to the main 

structure (Rayevskiy and Fiveg, 1973). Most of the following 

discussion on the deposit has been extracted from Rayevskiy 

and Fiveg (1973).

Salt and potash at this site are considered part of the 

Kimmeridgian-Tithonian (Upper Jurassic) Gaurdak Formation. 

The potash-bearing material is underlain by pink rock salt 

with varicolored lenses of white and gray salt, veins of 

anhydrite, and rare inclusions of red argillaceous-carbonate 

material. The base of the potash-rich horizon(s) is composed 

of carnallite and impure halite that grades up-section from 

less than 0.6 percent K2O to as much as 29.3 percent K2O. 

Above the carnallite base, three sylvinite layers are separated 

by rock salt. The deposit’s lower sylvinite layer is 2–20 m 

thick and contains less than 5.5 percent K2O on average. The 

overlying “Tyubegatan” sylvinite layer is 0.8–10.6 m thick 

and comprises pink, red, and white sylvite and halite with thin 

veins of carnallite and anhydrite; this is the most continuous 

of the three layers reported by Sedletskiy (1969). The potash 

content of this layer ranges from 11.2 to 30.9 percent K2O 

and was considered by Rayevskiy and Fiveg (1973) and 

Sedletskiy (1969) to be the main unit of economic interest. 

The upper sylvinite layer at Tyubegatan is rock salt with less 

than 2.5 percent K2O as sylvite. The upper sylvinite is in turn 

overlain by the confusingly-named “intermediate salt unit.” 

This intermediate salt contains less than 9.2 percent K2O in 

the southwestern parts of the deposit, and decreases in potash 

grade and overall thickness to the northeast.

The rock salt and potash horizons are missing in 

parts of the structure (fig. 2-5), though the extent of this 

unmineralized area is not clear from the Rayevskiy and Fiveg 

(1973) discussion.

The middle sylvinite layer of Sedletskiy (1969) was 

evaluated by using data from 59 drill holes across 12 profiles. 

Reserves were calculated by using 45 of the drill holes in 

an area of approximately 80 km2. Ore averaged 5.6 m thick 

at depths of about 100–800 m (table 2-2). In 2006, it was 

announced that the Uzbekistan part of this deposit would 

be developed for production (Ashurmatov, 2006; Shanghai 

Cooperation Organization for Economic Cooperation, 2006). 

In December, 2009, an unspecified amount of ore was mined 

from this deposit (Henley and Allington, 2010).

Mineral Occurrences

Potash prospects and occurrences in the tract were 

outlined by Russian geologists (Fedin, 1981; Vysotskiy 

and others, 1988) incidental to oil and gas exploration. The 

stratigraphy and structure of the potash-bearing zone were 

described by Russians from two-dimensional seismic data as 

well as from drill core and well logs. Brief descriptions in the 

Russian literature (Vakhabov, 1986; Popov, 1988) mention 

thinning and thickening of potash horizons from as little as 

1 m on the edge of a typical mining concession to as much as 

150 m in the core of the concession. 

Eighteen potash occurrences are reported within the 

Gissar tract (fig. 2-1, table 2-3), all within the Upper Jurassic 

Gaurdak Formation (Petrov and Chistyakov, 1964; Popov, 

1968; Rayevskiy and Fiveg, 1973; Sedletskiy and Fedin, 

1981). Only 5 of the 18 known potash occurrences are 

discussed in the following section because of the extremely 

limited information available.

Adamtash

The Adamtash occurrence (fig. 2-1, table 2-3) is a 

potash-bearing structure in Uzbekistan, ~100 km northeast of 

the border with Turkmenistan. Potassium salt was detected 

using gamma-ray-log data at a depth of approximately 

1,100 m (Popov, 1968). The potash occurs near the top 

of a rock salt horizon that exceeds 200 m in thickness 

(Popov, 1968).

Donguzsyrt

The Donguzsyrt occurrence (fig. 2-1, table 2-3; see also, 

location in fig. 3-1) in Turkmenistan is a potash-bearing salt 

structure expressed at the surface as a low-lying hill and is a 

brachyanticline in the extreme southwestern part of the Gissar 

tract. Although referred to as a salt dome in the literature, 

the salt structure and deformation of this occurrence result 

from folding and faulting related to the tectonism of the 

Gissar Range rather than depth of burial (Kutuzov and Popov, 

1976). The surface expression of this salt structure occupies 

an area of about 2.5 km2 and largely comprises anhydrite 

and (or) gypsiferous rock. The structure and lithology of this 

brachyanticline (fig. 2-6) is similar to those of the deposit at 

Tyubegatan (fig. 2-5). An explanation of the anhydrite that lies 

between the potash and the top of the rock salt at Donguzsyrt 

was not given in the available literature.
Chapter 2 23

C'

SOUTHEAST

 500

SEA LEVEL 

500

1,000

METERS

C

NORTHWEST

B B'

Tyubegatan brachyanticline

NORTHWEST SOUTHEAST

 500

500

1,000

METERS

Tyubegatan-Lyalimkan brachyanticline

A A'

NORTHWEST SOUTHEAST

Akbash salt dome

 1,500

 1,000

 500

500

1,000

METERS

SEA LEVEL 

VERTICAL EXAGGERATION ×0.5

0 0.5

0 0.25

0.25 0.75 1 KILOMETER

0.5 MILE

VERTICAL EXAGGERATION ×0.5

0 0.5

0 0.25

0.25 0.75 1 KILOMETER

0.5 MILE

SEA LEVEL 

VERTICAL EXAGGERATION ×0.5

0

0

0.25 0.5 KILOMETER

0.25 MILE

A

B

C'

A'

B'

C

0 1 2 KILOMETERS

CAsia_Fig 2-5 gjo2

Upper Jurassic Oxfordian

Fault

Cross-section line

EXPLANATION

Limestone

Anhydrite, gypsum-anhydrite 

 mix at surface

Rock salt

Potash

Terrigenous sulfate rock

 of the Gaurdak Formation

Lower Cretaceous rock

Quaternary sediments

A A'

Kimmeridgian-Tithonian

N

Figure 2-5. Map and cross sections showing parts of the Tyubegatan brachyanticline, the Lyalimkan area of the Tyubegatan 

brachyanticline, and the Akbash salt dome, Turkmenistan and Uzbekistan (modified from Rayevskiy and Fiveg, 1973). Location shown on 

fig. 2-4.
24 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Mineralized rock at Donguzsyrt consists of two potash 

layers that have poorly constrained thicknesses and grades 

resulting from poor preservation of the drill core (Kutuzov 

and Popov, 1976). Potash was identified at depths of 356 m 

to almost 600 m in the few documented drill holes. Fedin 

(1981) estimated that 100 million metric tons of so-called 

“potash salts” could be present in the brachyanticline. A more 

definitive estimation would require additional drilling and 

geologic information.

Khamkan

The Khamkan occurrence (fig. 2-1, table 2-3) in 

Uzbekistan is approximately 17 km north-northeast of the 

Turkmenistan-Uzbekistan border in the central part of the 

Gissar tract. Two potash layers have been identified on an 

anticline on the western limb of the Kugitang structure. 

Sylvite occurs in the upper part of a rock salt unit more than 

200 m thick (Popov, 1968). One layer consists of sylvinite 

that is reported to be 3.5 thick and contains 15.9 percent K2O. 

The second potash layer consists of approximately 1.5 m of 

carnallitite for which no K2O grade is reported; however, 

the bed contains more than 10 percent magnesium chloride 

(Sedletskiy, 1969; Rayevskiy and Fiveg, 1973; Fedin, 1981).

Khodzhaikan

The Khodzhaikan occurrence (fig. 2-1, table 2-3) is in 

extreme southeastern Uzbekistan, approximately 1 km from 

the Turkmenistan border in the south-central part of the Gissar 

tract. Three potash layers occur at depths of less than 403 m 

on the southeastern limb of the Kugitang brachyanticline in 

a rock salt unit that is locally as much as 200 m thick. The 

thicknesses of the three potash-bearing layers were 3.5, 20, 

and 19.2 m in a single drill hole; grades were 7.5–18.6 percent 

K2O (Rayevskiy and Fiveg, 1973). Rayevskiy and Fiveg 

assigned these potash-bearing layers to the Lower Cretaceous 

Almurad Formation on the basis of red-colored sedimentary 

rocks of assumed Neocomian age below the salt.

Table 2-3. Known occurrences of potash within the Gissar tract, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan.

[m, meter; Mt, million metric tons; —, no data]

Name Latitude Longitude Comments Reference

Adamtash 38.658 67.132 Potash detected using geophysics Popov (1968); Sedletskiy and Fedin (1981); Vysotskiy and

others (1988)

Akrabat 38.271 66.791 Potash detected using geophysics Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Beleyainak 38.389 66.483 Potash is at depth of 2,200–2,500 m Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Chashranta 37.586 66.197 Sylvite Rodnov and others (2001)

Donguzsyrt 37.495 65.080 In Repetek Fault Zone, perhaps

100 Mt at depth of 300–350 m

Fedin (1981); Khudaykuliev (1986); Kutusov and Popov (1973)

East Karail 38.727 67.082 — Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Etymdag 37.418 66.292 Could have significant potash

resource

Fedin (1981)

Gumbulak 38.580 66.853 Potash detected using geophysics Vysotskiy and others (1988)

Kantau 38.467 66.733 Potash detected using geophysics Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Karabil 38.514 66.657 Potash detected using geophysics Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Karabay 38.600 66.565 Potash bed is low grade Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Khamkan 38.078 66.790 Sylvinite, carnallite lenses on

Kugitangskoe brachyanticline

Rayevskiy and Fiveg (1973); Fedin (1981); Sedletskiy (1969)

Khodzhaikan 37.577 66.556 Sylvinite, carnallite lenses on

Kugitangskoe brachyanticline

Garrett (1996); Osichkina (2006); Rayevskiy and Fiveg (1973)

Kokmiyar 38.010 66.136 — Fedin (1981)

Kyzylbayrak 38.570 67.005 Potash detected using geophysics Vysotskiy and others (1988)

Mobik 38.665 66.862 Potash detected using geophysics Vysotskiy and others (1988)

Tigarin 37.723 65.970 Promising salt structure with 

potash at about 1,200 m depth

Fedin (1981)

Uzunkuduk 40.572 67.147 Associated with salt diapir of

Malikokoy syncline

Rayevskiy and Fiveg (1973); Popov (1968)
Chapter 2 25

 300

 900

METERS

300

SEA LEVEL

 600

 1,200

SOUTHWEST NORTHEAST

300

SEA LEVEL

 300

 600

 900

METERS

NORTHWEST SOUTHEAST

NOT TO SCALE

NOT TO SCALE

Cretaceous sedimentary rocks of Limestone

 the Okuzbulak, Kyzyltash, and 

 Almurad Formations

Clay, siltstone, and sandstone 

 of the Karabil Formation

Fault—Approximately 

 located

Quaternary sediments

Potash

Anhydrite ± gypsum

Rock salt

EXPLANATION

Jurassic

CAsia_Fig2-6_g

Figure 2-6. Cross sections of the Donguzsyrt potash-bearing salt structure, Turkmenistan (after Kutusov 

and Popov, 1976). Location coincides with the Donguzsyrt occurrence, shown in fig. 2-1. Horizontal scale is 

estimated.
26 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Uzunkuduk

The Uzunkuduk occurrence (fig. 2-1, table 2-3) in 

Turkmenistan is approximately 20 km southeast of the town 

of Gaurdak in the central part of the Gissar tract. Potash 

mineralization is in a salt diapir in the Uzunkuduk Fault 

Zone. The diapir is 200–300 m wide and more than 2 km long 

(Popov, 1968). Potash was identified at depths of 215.8–250 m 

and consists of approximately 2 m of sylvinite and (or) 

carnallitite-sylvinite (Rayevskiy and Fiveg, 1973). No grades 

are reported for this site.

Exploration and Development History

Much of the known potash in the CASB was discovered 

incidentally during hydrocarbon exploration drilling, but 

potash exploration has occurred only in the central part of 

the Gissar tract. Written descriptions for individual deposits, 

occurrences, concessions, and structures in the Russian 

literature suggest that the central part of the tract is moderately 

to well explored.

The Tyubegatan deposit, Uzbekistan-Turkmenistan, 

containing a reported 400 Mt of potash reserves, was defined 

by drilling (Zhang and others, 2005; Ashurmatov, 2006) 

and the first ore was mined in December 2009 (Henley and 

Allington, 2010; Ansher Holding Limited, 2010). Limited 

production from a pilot solution mine at the Karlyuk deposit 

in eastern Turkmenistan occurred in 1983 (Garrett, 1996). 

Scattered reports suggest that the Karlyuk and Gaurdak 

deposits will be brought into production in the next few 

years. No production is reported or planned for the other 

known deposits.

Data Availability

Numerous reports describing the geology, geophysics, 

drill-hole logs, and mineral occurrences of the Gissar tract 

(table 2-4) are available. Many are more than 20 years old; 

most are published in Russian. The most useful publications 

in terms of data content include Baikov and Sedletskiy (2001), 

Fedin (1981), Rayevskiy and Fiveg (1973), Ulmishek (2004), 

and Vysotskiy and others (1988).

Quantitative Estimation

The Gissar tract is treated as a hybrid or transitional 

deposit of the end member stratabound and halokinetic 

potash-bearing salt deposits because the literature indicates 

that potash contiguity in this part of the Amu Darya Basin has 

been disrupted in places by salt structures and tectonics and, in 

some locations, is relatively undisturbed. As such, we decided 

it best to evaluate the tract as both stratabound and halokinetic 

in character.

The USGS global potash assessment recognizes two 

end-member subtypes of potash-bearing bedded salt—

stratabound and halokinetic deposits (appendixes A and B). 

Stratabound deposits are extensive, flat-lying, and largely 

undisturbed since deposition. Halokinetic deposits have been 

disrupted by salt tectonics, fault movement, dissolution, 

or other processes that significantly changed thickness or 

continuity since original deposition; these deposits contain, on 

average, smaller tonnages than stratabound deposits.

Need for Two Estimation Approaches

Some known deposits, such as Karabil and Karlyuk, 

appear to be flat-lying (or at least stratabound) and have large 

reported reserves and resources; however, they are not as 

areally contiguous as most stratabound deposits. Observations 

that support a halokinetic deposit classification include 

erratic depths of mineralized rock, lack of continuity of 

mineralized rock over large areas of the tract, local significant 

thinning or thickening of potash-bearing unit(s), and highly 

developed halokinetic processes with increasing depth of 

evaporite burial in the southern part of the Gissar tract and 

eastward into the western boundary of the Afghan-Tajik tract. 

References in the Russian literature to “купола” (domes), 

“брахиантиклиналь” (brachyanticlines), and “линзы” 

(lenses) also suggest halokinesis. 

Because alternate delineations of the tract did not resolve 

this complex, quasi-stratabound situation, except at a scale 

that defined targets instead of resources, and because we had 

no methodology for assessing a hybrid or transitional tract, 

we chose to estimate the undiscovered resources of the Gissar 

tract using two assessment methodologies. Undiscovered 

resources assumed to be halokinetic were assessed using the 

three-part form of assessment of Signer and Menzie (Singer, 

1993; Singer and Menzie, 2005, 2010) and stratabound potash 

resources were quantitatively assessed using the Adaptive 

Geometric Estimation (AGE) methodology (appendix A).

Assessment of Undiscovered Potash Resources as 

Halokinetic Potash-Bearing Salt Deposits

Undiscovered potash resources in the Gissar tract were 

estimated by assuming they were halokinetic potash deposits 

(appendix C) and by using the three-part form of assessment 

described by Singer and Menzie (2005). The assessment team 

(appendix G) consisted of three international experts and five 

USGS experts, plus a USGS facilitator who was experienced 

in mineral resource assessments, and who also had a broad 

understanding of potash in evaporites. An estimate of the 

number of deposits (table 2-4) was made by members of 

the assessment team for the delineated tract using the global 

halokinetic grade and tonnage model (table 2-6) developed for 

the potash assessment.
Chapter 2 27

Table 2-4. Principal sources of information for the Gissar tract, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan.

[CIS, Commonwealth of Independent States; GIS, geographic information system; M, million; USSR, Union of Soviet Socialist Republics]

Theme Name or title Scale Citation

Geology

Potassium-bearing basins of the world Unknown Vysotskiy and others (1988)

Some aspects of the genesis of halogenic sequences— 

Evidence from the Central Asian halogenic basin

Unknown Baikov and Sedletskiy (2001)

Tectonics of the Afghan-Tajik Depression Unknown Bekker (1996)

Afghan-Tajik Depression Unknown Nikolaev (2002)

Geologic map of Turkmenistan 1:500,000 Mirzakhanov (1989)

Mineral deposits database and thematic maps of Central Asia 1:500,000 Seltmann and others (2005)

Mineral

occurrences

An evaluation of prospects for potash-bearing capabilities in 

Upper Jurassic salt deposits, southern Central Asia

Unknown Fedin (1981)

World survey of potash resources Unknown British Sulphur Corporation (1979)

Uzbekistan to extend its chemical industry Unknown Ashurmatov (2006)

Upper Jurassic halogen deposits of southeast Central Asia Unknown Luchnikov (1982)

Investigation of potassium resource, exploitation and 

utilization in Turkmenistan

Unknown Zhang and others (2005)

Deposits of potassium salts in the USSR Unknown Rayevskiy and Fiveg (1973)

New data on the geology of Donguzsyrt, Southeast Turkmenia Unknown Kutuzov and Popov (1976)

Industrial minerals of the CIS Unknown Troitskiy and others (1998)

Subsurface

geology

Deposits of potassium salts in the USSR Unknown Rayevskiy and Fiveg (1973)

Petroleum resource potential GIS of northern Afghanistan Various Steinshouer and others (2006)

Petroleum geology and resources of the Amu-Darya Basin Various Ulmishek (2004)

Facies zoning and conditions of sediment accumulation of 

Upper Jurassic salt-bearing formations in the territories of 

eastern Turkmenia

Unknown Gavril’cheva (1981)

Hydrogeologic conditions of gas reservoirs in Murgab Basin Unknown Semashev (1983)

Amu Darya Basin and surrounding areas–generalized location

map showing major structural elements, hydrocarbon provinces,

hydrocarbon fields and well locations

1:1.35M Blackbourn (2008)

Geophysics Petroleum geology and resources of the Amu-Darya Basin Various Steinshouer and others (2006)

Exploration

Lithofacies and potassium potential of Upper Jurassic halogen

deposits in Central Asia

Unknown Sedletskiy and Fedin (1981)

Jurassic Basins Unknown Vysotskiy and others (1988)

World survey of potash resources Unknown British Sulphur Corporation (1979)

Structure of the Upper Jurassic halogen complex and its role in

predicting buried reefs in the Amu-Darya regional low

Unknown Khudaikuliev (1989)

Three-Part Form of Assessment Process and Rationale

The team reviewed the deposit and grade and tonnage 

models and the process for delineating the tract, discussed the 

oil and gas exploration history of the Amu Darya Basin, and 

evaluated the following factors that suggest the presence of 

undiscovered halokinetic deposits in the Gissar tract:

• The marine evaporite section of the Gaurdak Formation 

is as much as 1,200 m thick and extends over a vast 

region. A limited number of stratigraphic sections in 

Russian reports suggest that combined salt and potash 

layers may be as thick as 800 m in places;

• Known deposits occur at Karabil, Gaurdak, Karlyuk, 

Tyubegatan, and other locations;

• Salt and potash are not present everywhere in the larger 

salt field or in specific structures (see, for example, 

fig. 2-5). Brief descriptions in other references 

(Belelovskiy and others, 1971; Vysotskiy and others, 

1988; Baikov and Sedletskiy, 2001) all imply that 

deposits in the Gissar tract are not as continuous as 

would be expected of a purely stratabound deposit;

• Known deposits in the area of the Gissar tract are distal 

to the seawater inflow point of the original CASB to 

the northwest, which is consistent with the halokinetic 

potash-bearing salt model (appendix B);
28 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

The following factors argue against the presence of 

undiscovered halokinetic deposits:

• Tremendous east-west compression (as much as 

50 percent) of the Afghan-Tajik Basin, adjacent to the 

eastern margins of the Gissar tract suggests at least the 

possibility of increased dissolution and alteration of 

potash on the east side of the tract;

• Geophysical evidence suggests that Upper Jurassic 

strata of the Afghan-Tajik (eastern) side was buried to 

depths of 7 km, which limits the eastward extension 

of potash lying above the 3-km assessment depth limit 

and within the Gissar tract;

• Known deposits appear to have been uplifted by the 

flanks of the Gissar Range, implying that they are deep 

and less accessible elsewhere;

• The relative flatness of the Karlyuk and Karabil 

deposits and their continuity is more consistent 

with stratabound potash-bearing salt deposits than 

halokinetic potash-bearing salt deposits.

The assessment team’s estimate of numbers of 

undiscovered deposits incorporated the above factors and 

was made in part by analogy with estimated deposit densities 

in other tracts and similar environments (for example, 

Dnieper-Donets, Zechstein in Orris and others, 2014). The 

team also considered what little is known of the exploration 

history (that is, the relatively few potash deposits known for 

such a large evaporite basin), and the large number (nearly 50) 

of potash prospects (Fedin 1981; Vysotskiy and others, 1988) 

that were discovered incidental to hydrocarbon exploration 

to the west and northwest in the Amu Darya tract. It is 

reasonable to expect that deposits exploited on one limb of a 

brachyanticline could be mirrored in the other limb, as well as 

elsewhere along strike.

Results

Estimates of numbers of deposits by individual team 

members (table 2-5) vary, however, the consensus estimate 

is that there are 7.2 undiscovered halokinetic potash-bearing 

salt deposits in the Gissar tract (table 2-6). Contained potash 

(K2O) in the tract was estimated by combining the consensus 

estimate with the grade and tonnage model developed for this 

study (table 1-2, appendix D), using the Economic Mineral 

Resource Simulator (EMINERS) program (Root and others, 

1992; Bawiec and Spanski, 2012; Duval, 2012). The result 

is a mean of 470 Mt of K2O (table 2-7). The complete results 

of the Monte Carlo simulation are presented as a cumulative 

frequency plot (fig. 2-7) showing estimated resource amounts 

associated with cumulative probabilities of occurrence, as well 

as the mean, for potash and for total mineralized rock.

Table 2-5. Deposit estimates by individual team members for the 

Gissar tract, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan.

[Nxx, estimated number of deposits associated with the xxth percentile]

Estimator Estimated number of undiscovered deposits

N90 N50 N10 N05 N01

1 1 5 10 10 10

2 1 4 6 6 6

3 1 5 20 20 20

4 1 2 5 5 5

5 3 7 15 15 15

6 1 5 5 5 5

7 6 12 25 25 25

8 2 6 16 16 16

Table 2-6. Undiscovered deposit estimates, deposit numbers, tract area, and deposit density for halokinetic potash-bearing 

deposits in the Gissar tract, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan.

[Nxx, estimated number of deposits associated with the xxth percentile; Nund, expected number of undiscovered deposits; s,standard deviation; Cv %, 

coefficient of variance; Nknown, number of known deposits in the tract that are included in the grade and tonnage model; Ntotal, total of expected number of 

deposits plus known deposits; density, total number of deposits (N) per square kilometer (km2). Nund, s, and Cv % are calculated using a regression equation 

(Singer and Menzie, 2005)]

Consensus undiscovered deposit estimate Summary statistics Tract area 

(km2)

Deposit 

density

(N/km2 N90 N50 N10 N05 N01 Nund ) s Cv

 % Nknown Ntotal

1 7 14 14 14 7.2 4.5 63 10 17.2 26,669 0.001
Chapter 2 29

Table 2-7. Results of Monte Carlo simulations of undiscovered potash resources in halokinetic potash-bearing salt potash 

deposits in the Gissar tract, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan.

[Mt, million metric tons]

Material

Probability of at least the indicated amount Probability of

mean or greater

Probability of

zero 0.95 0.9 0.5 0.1 0.05 Mean

K2O (Mt) 0 18 390 1,200 1,400 470 0.45 0.08

Rock (Mt) 0 110 2,500 6,100 7,100 2,900 0.45 0.08

10k 100k 1M 10M 100M 1B 10B 100B 1Tr

Mean potash Mean rock

1.00

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

Probability

Material, in metric tons

Mean rock

Mean potash

Rock

Potash

EXPLANATION

Figure 2-7. Cumulative frequency plot showing results of Monte Carlo simulation of 

undiscovered resources in halokinetic potash-bearing salt deposits in the Gissar tract

(142mxK0005a), Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan. k, thousands; M, 

millions; B, billions; Tr, trillions.
30 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Assessment of Undiscovered Resources as Stratabound 

Potash-Bearing Salt Deposits

Assessment of stratabound deposits requires a method 

that considers the areal extent of the deposit, its thickness, and 

the range of ore grades throughout the deposit. The three-part 

form of assessment described in previous sections assumes 

that there is some number of discrete undiscovered deposits in 

the area being considered. Stratabound, relatively undeformed 

mineralized rocks that are contiguous within small to large 

parts of a depositional basin, may form a geologic deposit but 

are not always divisible into the physically discrete economic 

deposits needed to estimate the number of deposits needed for 

the three-part form of assessment. Therefore, for the global 

assessment of potash (K2O), the AGE method was developed 

to estimate undiscovered resources in stratabound deposits.

The following observations support the presence of 

undiscovered potash in stratabound deposits:

• The marine evaporite section of the Gaurdak Formation 

is as much as 1,200 m thick and extends over a vast 

region according to the Russian literature. A limited 

number of stratigraphic sections in Russian reports 

suggest potash-hosting salt may be as thick as 800 m 

in places, suggesting a substantial potash resource;

• The large size of known deposits, such as Karabil and 

Karlyuk, suggests that disruption or loss of potash 

is more similar to stratabound potash-bearing salt 

deposits in some, but not all, parts of the tract;

• Blackbourn (2008) shows structure in the tract 

consisting of gently undulating folds;

The following observations do not support the presence of 

large stratabound potash deposits:

• At least two throughgoing faults in the same 

Blackbourn structural map suggest the possibility of 

local tectonic disruptions and dissolution;

• Older Russian literature refers to “lenses” of potash in 

the tract area, a word which has uncertain meaning, but 

generally refers to local thickening or a body of limited 

extent;

• The known presence of salt structures, some of which 

have pierced overlying sedimentary rocks or led to 

erosion and loss of salt and potash in the crests of the 

structures imply the presence of halokinetic-potash 

bearing salt deposits.

Overview of the Adaptive Geometric Estimation (AGE) Method 

The AGE method (appendix A) follows a similar 

approach, albeit without the strict drill-hole density controls, 

to that used by most Canadian NI 43-101 standardized reports 

to estimate in-place volume of reserves and resources when 

applied to potash (Canadian Institute of Mining, Metallurgy 

and Petroleum, 2005, 2012), in that an in-place tonnage is 

calculated and then reduced by adjustments for anomalies 

and other factors. An AGE simulation can be modified to 

allow missing, incomplete, and unknown data to be estimated 

subjectively and (or) statistically through use of distributions 

based on partial data or analogous areas. Other approaches, 

such as a kriging method, were not used because of the large 

gaps between drill holes and other data points in the Gissar 

and Amu Darya tracts and the need to estimate the percent 

of unmineralized area, as well as missing variables such as 

thickness and grade.

In the AGE method, the volume of the tract being 

evaluated is first estimated using the tract area and thickness 

data. A grade is randomly selected from the grade distribution 

and the volume is converted to tonnage using a density based 

on the selected grade. The tonnage estimate is then adjusted 

to correct for areas of dissolution and lack of initial potash 

deposition, internal to the mineralized area (anomalies) and 

along the boundaries of the mineralized area (embayments). 

Lastly, known resources are subtracted from the calculated 

tonnage to determine the amount of undiscovered K2O 

contained in the mineralized rock. All calculations are 

completed using a customized SYSTAT script (appendix F).

In the AGE method, unknown or incompletely known 

parameters may be (1) estimated from incomplete data 

available within the tract being studied, (2) estimated based 

on global averages for the deposit type, or (3) estimated 

subjectively. These estimates may be single numbers, but in 

this assessment they commonly are distributions that represent 

the variation of a particular parameter observed elsewhere, 

as well as the uncertainty in predicting its value(s). When 

assessing undiscovered resources, incomplete and missing 

data are the norm. Therefore, tract delineation and parameter 

estimation for missing data are critical for calculating a 

quantitative estimate of undiscovered resources. Parameter 

estimates for the Gissar tract (table 2-8) are discussed below.

Parameter Specification

(a) Volume

The volume of potash resources for the Gissar tract was 

calculated using a contoured set of potash thicknesses bounded 

by the tract, using an average, minimum, and maximum 

thickness. In the Amu Darya tract (chapter 3) we used data 

from drill holes to contour thickness because they covered a 

significant part of the tract (fig. 2-1). We averaged thicknesses 

in the Gissar tract to account for high data variability over 

short distances, a consequence of the Gissar Range uplift 

and deformation of potash-bearing salt. These thickness 

estimations are consistent with thickness estimations of the 

neighboring Amu Darya tract to the west. Average thickness 

for the Gissar tract was calculated as the weighted average of 

total potash thickness from all available data (appendix E). 
Chapter 2 31

Table 2-8. Parameters used to estimate undiscovered K2O resources in stratabound potash-bearing 

salt deposits in the Gissar tract, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan.

[km3, cubic kilometer; m, meter; min, minimum; max, maximum; %, percent]

Parameter Source Description

Thickness Drill holes, other sources Weighted average 4.5 m (min 3 m; max 10 m)

Volume Triangular distribution Triangular distribution (min 82 km3; mode 123; max 273) 

Grade (K2O) Drill holes, other sources Normal distribution (mean 15.84%; standard deviation 4.42)

Anomalies Global distribution Triangular distribution (min 5%; mode 25%; max 40%)

Embayments Global distribution Triangular distribution (min 5%; mode 15%; max 30%)

Maximum and minimum thicknesses were taken directly 

from available drill-hole intercept data for this tract. These 

thickness values were used to calculate a minimum, average, 

and maximum distribution of possible potash volumes for the 

area of the tract using ArcMap.

(b) Grade

Available grade data for potash intervals of 1 m or 

greater in the Gissar and Amu Darya tracts were compiled 

and analyzed. The grade data (appendix D) form a normal 

distribution with a mean of 15.8 percent K2O and a standard 

deviation of 4.42. Figure 2-8 provides a histogram showing 

grade distribution for potash in stratabound deposits in the 

Gissar tract. Conceptually, the mean or median are close to 

the actual average grade across the tract, and the tails of the 

grade distribution are much less likely to represent the tract as 

a whole. However, because data were not available for large 

parts of the Amu Darya tract, the higher and lower values 

of K2O represented by the tails of the distribution cannot be 

completely eliminated as possibilities, however slight.

Two simplifications were necessary to use the grade data. 

There was limited point grade data across the tract extent, and 

no information on how typical any grade in the grade data 

we identified might be. Therefore, the grades in the grade 

distribution were treated as the range of possible average 

grades in the resource estimation simulation; in other words, a 

selected grade was applied to the entire tract during each pass 

of the Monte Carlo simulation. Because we do not know the 

potash mineral composition at most given points in the tract, 

it was assumed that average grades below 16.9 percent K2O 

resulted solely from carnallite mineralization whereas grades 

of 16.9 percent or higher resulted from sylvite mineralization. 

This is based on experience with other potash-producing 

areas such as the Congo, Dnieper-Donets (Ukraine), and 

Zechstein (northern Europe); see Appendix C for a more 

detailed explanation. The density of carnallite is 1.6 (grams 

per cubic centimeter) g/cm3, sylvite is 1.99 g/cm3, and halite is 

2.165 g/cm3 (table I-1). With this information, an appropriate 

density can be determined for a select grade when estimating 

the undiscovered resource.

(c) Anomalies and Embayments

Unmineralized areas within stratabound potash deposit 

tract boundaries that are not connected to the edges of 

mineralization (and thus would be “embayments”) are termed 

“anomalies” for the purposes of this assessment. Anomalies 

disturb the continuity of potash-bearing beds, and may range 

in size from less than one square meter to tens of square 

kilometers or more. Anomalies are usually composed of 

barren salt (halite) and commonly result from dissolution, 

diagenetic processes, or localized non-deposition of potash 

for unknown reasons. We used a range of 5–35 percent with 

a mode of 20 percent, based on better-known potash deposits 

elsewhere in the Monte Carlo simulation. The maximum is a 

conservative value and the minimum is based on the lowest 

reports of anomalies in the literature.

Potash and other salt deposits tend to have highly 

irregular tract boundaries that result from initial deposition 

and subsequent erosion. Where boundaries of stratabound 

potash have been mapped in detail, in places such as 

Carlsbad, New Mexico, they show pronounced embayments 

between unmineralized and mineralized areas. A more 

complete discussion of anomalies and embayments, including 

references, is in the method summary in appendix C.

15 20

0.10

10 25

0.20

K20 (%)

Probability

N = 106

Mean = 15.84

Median = 16.05

StdDev = 4.42 

Figure 2-8. Histogram showing grade distribution for 

potash (K20) in stratabound deposits, Amu Darya and 

Gissar tracts, Turkmenistan, Uzbekistan, Tajikistan, and 

Afghanistan. N, number of grade distribution samples; 

StdDev, standard deviation. Data table is available in 

appendix D.
32 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Tectonism has uplifted and deformed the salt layers in 

this tract, increasing the possibility of erosion or dissolution. 

For example, a section of the central Gissar area is not 

permissive for potash because it has been eroded to below 

the level of the Upper Jurassic potash-bearing Gaurdak 

Formation (fig. 2-4). The anomalies parameter estimate has 

a higher mode and maximum for the Gissar tract than for the 

Amu Darya tract. This accommodates the greater evidence for 

tectonism in the Gissar tract than is found in the Amu Darya 

tract to the west. A more complete discussion of anomalies 

and embayments with references is in the Adaptive Geometric 

Estimation method summary in appendix C.

Simulation

The AGE approach for estimating undiscovered K2O 

content of the Gissar tract (see Appendix C) assumes that 

potash deposits are dominantly stratabound and roughly 

flat-lying, consistent with the stratabound potash-bearing salt 

model (appendix A). The simulation begins with a calculation 

of the volume of potash-mineralized rock as the area 

multiplied by a variable thickness derived from very limited 

drill-intercept data.

After calculating the tract volume and other parameters, 

the next step is to run a Monte Carlo simulation, a random 

selection of a grade distribution done 5,000 times to obtain 

a distribution of the undiscovered potash. This grade is then 

used to determine whether carnallite or sylvite is the potash 

mineral (see previous discussion of grade), and thus determine 

the appropriate density value for converting tract volume to 

tonnage. The simulation actually calculates the volume and 

tonnage of sylvite (or carnallite) and of halite. The resulting 

tonnages are then adjusted for the expected proportions of 

anomalies and embayments, and finally the total tonnage is 

calculated and known resources are subtracted from this. 

The simulations were run in SYSTAT 12, statistical 

analysis software. A generalized version of the SYSTAT script 

and a table defining the variables in the script is in appendix F.

Results

Our volume calculation assumes that stratabound potash 

mineralization varies from 82 to 273 km3 (mode 234 km3) 

depending on the average potash thickness assumed for the 

tract. This calculation results in a mean estimated resource of 

27.9 Bt of K2O (median 25.3) remaining undiscovered in the 

Gissar tract (fig. 2-9). The N=5,000 in the figure represents 

5,000 Monte Carlo simulation runs using randomly selected 

grades and volumes to arrive at a most likely tonnage and 

to estimate uncertainty. At 90 percent confidence, there is at 

least 13.1 Bt of K2O present; at 10 percent confidence, there is 

47.0 Bt of K2O present (table 2-1). These values compare well 

with the 20 Bt of K2O estimated by Zhang and others (2005) 

for an apparently similar but ill-defined area.

Discussion

The Zhang and others (2005) estimate is consistent 

with ours if (a) they are discussing ore, not K2O, and (b) we 

compare these numbers with the USGS AGE calculation. In 

Zhang and others (2005), the tract boundaries and estimation 

method are not clearly explained. If all potash in the Gissar 

tract occurs as halokinetic potash-bearing salt deposits, then 

the three-part form of assessment of Singer and Menzie 

(2005) predicts a mean undiscovered resource of 470 Mt of 

K2O. Alternatively, if all potash in the Gissar tract occurs as 

stratabound potash-bearing salt deposits, then the AGE method 

predicts a mean undiscovered resource of 27.9 Bt of K2O. 

If we assume that Zhang and others (2005) estimated 

“nearly 20 billion tons” of potash ore in the central Gissar 

tract (fig. 2-4), then less than 20 percent of that ore (less than 

4 Bt) is K2O; this amount is more than one order of magnitude 

higher than the USGS halokinetic potash estimate and more 

than one order of magnitude lower than the USGS stratabound 

potash estimate. In other words, our end-member halokinetic 

and stratabound estimates for potash for the hybrid Gissar 

tract likely bracket the actual value. Note that our stratabound 

potash estimate is similar to the Zhang and others (2005) 

estimate of 20 Bt of K2O. If the Zhang and others (2005) 

estimate is for the entire CASB, then the USGS estimate for 

halokinetic deposits is more consistent with theirs.

The USGS estimate of undiscovered potash resources 

in halokinetic deposits of the Gissar tract is likely an 

underestimate resulting from (1) conflicting information on 

the style and age of mineralization within known deposits 

and occurrences of the Gissar tract; (2) uncertainty about the 

mineralization and depth in the southwestern part of the tract; 

(3) an incorrect, or at least incomplete, understanding of the 

Donguzsyrt occurrence in the southwestern part of the tract 

Figure 2-9. Histogram showing distribution of 

estimated in-place K2O (potassium oxide) content in 

undiscovered stratabound potash deposits, Gissar tract 

(142mxK0005a), Turkmenistan, Uzbekistan, Tajikistan, 

and Afghanistan. N, number of in-place K2O samples; 

StdDev, standard deviation.

0.02

0.04

0.06

0.08

Probability

N = 5,000

Mean = 27.9

Median = 25.3

StdDev = 12.5

CAsia

10 20 30 40 50 60 70

K2

0 content, in billion metric tons 
Chapter 2 33

(the Kutuzov and Popov [1976] paper was not available to 

us at the time of the assessment); (4) deliberate conservatism 

on the part of the assessment team in assessing additional 

potential for potash mineralization; and (5) sparse data in the 

global tonnage model to accurately represent the size range of 

the deposits in this tract (Karlyuk and Karabil are very large 

and were not part of the halokinetic grade and tonnage model).

Alternatively, the USGS estimate of undiscovered 

potash in stratabound deposits of the Gissar tract is six to 

eight times larger than Zhang and others (2005), although the 

Gissar tract almost certainly covers a much larger area than 

they considered. This USGS result may be an overestimate. 

The relatively shallow northern part of the Gissar tract was 

extensively explored by Soviet geologists, and most of the 

significant potash mineralization there has probably already 

been identified. This implies that the tract may contain much 

larger barren areas than would be expected from the less 

deformed stratabound potash-bearing salt deposits used 

as the analogues to determine the anomaly correction in 

the simulation.

An apparent lack of agreement between the two 

calculations does not invalidate either USGS estimate. The 

authors believe that the true amount of undiscovered and 

potentially economic potash resource in the Gissar tract lies 

between 470 Mt and 27.9 Bt of K2O (table 2-1), placing it 

in the large tail of the distribution for worldwide halokinetic 

deposits and towards the smaller tail of distribution for 

worldwide stratabound deposits.

Additional data would lead to more optimistic estimates 

of numbers of halokinetic deposits in the three-part form 

of assessment or, in the AGE method, and would allow us 

to more closely define the parameters to reflect the actual 

geologic constraints of the area.
This page intentionally left blank
Chapter 3. Stratabound Potash-Bearing Salt Assessment for the 

Amu Darya Tract (142sbK0005b)—Turkmenistan and Uzbekistan

By Jeff Wynn,1 Greta J. Orris,2 Pamela Dunlap,2 Mark D. Cocker,2 and James D. Bliss2

1

U.S. Geological Survey, Vancouver, Washington, United States.

2

U.S. Geological Survey, Tucson, Arizona, United States.

Introduction

A quantitative assessment of undiscovered stratabound 

potash deposits was conducted for the Amu Darya tract of the 

Central Asia Salt Basin (CASB) that extends northwest from 

the Gissar Range along the Turkmenistan-Uzbekistan border 

(fig. 3-1). Upper Jurassic to Lower Cretaceous(?) potash 

and host salt of the Gaurdak Formation have been identified 

throughout the tract at or near the crests of abundant gentle 

anticlinal structures (fig 1-2). From the Russian literature, 

potash mineralization appears to be laterally continuous and 

stratabound, and to form a gently undulating surface. The 

assessment team interpolated limited available data (fig 3-2) to 

estimate a range of potash thicknesses for the Amu Darya tract 

that, in turn, allowed for estimation of volume and tonnage. 

Other parameters, such as grade and anomalies (unmineralized 

areas) were estimated from available data or analogous areas 

and were used to refine tonnage estimates of undiscovered 

potash resources. Our assessment team estimates a mean 

contained K2O (potassium oxide) resource of 41.1 Bt for the 

Amu Darya tract (table 3-1).

Location

The Amu Darya tract is west of the Gissar Range and 

spans the border of Turkmenistan and Uzbekistan, including 

the city of Chardzhou. It is within the Jurassic CASB, and 

includes relatively undeformed parts of the northern Beshkent 

Trough, Karabekaul Trough, and Dengizkul Arch (figs. 3-3, 

3-4, 3-5) that host potash occurrences. Maps shown in figures 

3-3, 3-4, and 3-5 are derived from different sources and, in 

many places, do not agree; however, unique locations and 

features on each map (not found on the other) were used 

to define the Amu Darya tract and are thus included for 

completeness. We have made an effort to bring the figures 

into closer agreement in terms of feature names and locations 

(such as cities and fault names) but have not forced our own 

interpretations of what we believed to be the intent of the 

individual authors of the source maps.

Table 3-1. Summary resource assessment results for the Amu Darya tract, Turkmenistan and Uzbekistan.

[km, kilometer; km2, square kilometer; Bt, billion metric tons]

Date of 

assessment

Assessment 

depth

(km)

Tract area 

(km2)

Known potash resources

(Bt K2O)

Mean estimate of 

undiscovered potash 

resources

(Bt K2O)

Median estimate of 

undiscovered potash 

resources

(Bt K2O)

2010 3 40,224 0 41.1 37.8
36 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan 66° E 64° E 62° E 40° N 38° N

A

F

G

H

A

NISTA

N

T

U

R

K

M

E

NISTA

N

U

Z

B

E

KISTA

N

Mary

Navoi

Bukhara

Samarkand

Chardzhou

Karshi

Gaurdak

Uzonshor

Sundukli

Aizovat Saman-tepe

Alyaudyn-Tau

Beshkent

Darbaza

Dengizkul

Dzhambulak

Girsan

Kamashi Karshi

Chashtepe

Kuruksay

Nishan

North Kamashi

Shady

Shurtan

South Pamuk Urtabulak

West Zevardy

Farab

Yangikent

Khauzak Kishtuvan

Kultai

Metedzhan Narazym

Zevardy

West Kishtuvan

Sakar

Kultak

Amu Darya River

70° E 65° E 60° E

40° N35° N

A

F

G

H

A

NISTA

N

KA

Z

A

KHSTA

N

TURKMENISTAN

U

Z

B

E

KISTA

N

Area of map

EXPLANATION

Assessed potash tract 142sbK0005b, Amu Darya tract

Other potash tracts

Potash occurrence; occurrences associated with other tracts are  shown in gray 

Potash deposit associated with other potash tract

0 20 40 60 80 KILOMETERS0 20 40 MILES

Political boundaries from U.S. Department of State (2009).Albers Equal Area Projection.Central meridian, 64° E., latitude of origin, 39° N.

CAsia_Fig 3-1 gjo2

Figure 3-1. Map showing location of the Amu Darya tract (142sbK0005b), Turkmenistan and Uzbekistan, and potash occurrences.
Chapter 3 37

UZBEKISTAN

TURKMENISTAN

Karshi

Bukhara

Samarkand

Chardzhou

Mary

Navoi

A m

u Da r y a R i ve

r

62° E 64° E 66° E

40° N39° N38° N

70° E 65° E 60° E

40° N35° N

AFGHANISTAN

KAZAKHSTAN

TURKMENISTAN

UZBEKISTAN

Area of map

0 20 40 60 80 KILOMETERS

0 20 40 MILES

Assessed potash tract 142sbK0005b, Amu Darya tract

Other potash tractsSections with known potash  thickness Drill hole 

EXPLANATION

Political boundaries from U.S. Department of State (2009).Albers Equal Area Projection.Central meridian, 64° E., latitude of origin, 39° N.

CAsia_Fig 3-2 gjo2

Figure 3-2. Map of the Amu Darya tract (142sbK0005b) showing drill holes and other point-source information indicating that at least one meter thickness of potash is present.
38 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

UZBEKISTAN

TURKMENISTAN

AFGHANISTAN

Mary

Bukhara Samarkand

Karshi

Chardzhou

CHARDZHOU STEP

Repetek 

Fault Zone

Gissar

Uchadzi-Kurama Arch

Bayram-Ali

Uplift

MURGAB BASIN

Obruchev Depression

KARABEKAUL TROUGH

Baisun

Graben

MURGAB 

BASIN

Zaunguz Basin

Gissar

Malay-Bagadzha

Uplift

BESHKENT TROUGH

GISSAR RANGE

Repetek 

Fault Zone

62° E 64° E 66° E

38° N

39° N

TURKMENISTAN

UZBEKISTAN

AFGHANISTAN

63° E 66° E

38° N

40° N

Area of map

Pre-Jurassic sedimentary and

 crystalline basement

Fault zone

Tract 142sbK0005b, Amu Darya tract

Relative highs—Anticlines, uplifts,

 and monoclines

Relative lows—Synclines, depressions,

 and troughs

EXPLANATION

0 20 40 MILES

0 20 40 60 80 KILOMETERS

Political boundaries from U.S. Department of State (2009).

Albers Equal Area Projection.

Central meridian, 65° E., latitude of origin, 30° N.

Figure 3-3. Map showing named structural provinces in and near the Amu Darya tract (142sbK0005b), Turkmenistan and 

Uzbekistan (adapted from Steinshouer and others, 2006).
Chapter 3 39

Mubarek

Arch

Gazli Arch

Kagan Arch Kandym-Alat

Arch

Dengizkul Arch

Uchadzi-Kurama Arch

Malay-Bagadzha Uplift

KARABEKAUL TROUGH

N. MUBAREK FAULT

BAGADZHA FAULT

REPETEK

FAULT ZONE

NORTH KARABIL TROUGH

BESHKENT TROUGH

KARSHI FAULT

ALBURZ-MORMUL FAULT

CHARDZHOU STEP

BUKHARA STEP

MURGAB BASIN

SOUTHWEST GISSARS

FOLD-THRUST BELT

REPETEK FAULT ZONE

Mary-Serakh High

SANDYKACHI DOWNWARP ZONE

ZAUNGUZ BASIN

AMU DARYA FAULT

KYZYL KUM FAULT

MANGYSHLAK-SOUTH GISSAR FAULT ZONE

BUKHARA

FAULT

REPETEK FAULT ZONE

KYZYL KUM PLATEAU

B'

B

C

C'

A'

A

Gaurdak

Bairam-Ali

Chardzhou

Bukhara

Gazli

Aktash

Samarkand

UZBEKISTAN

TURKMENISTAN

AFGHANISTAN

62° E 64° E

40° N

38° N

66° E

60° E 65° E 70° E

40° N

35° N

AFGHANISTAN

UZBEKISTAN

TURKMENISTAN

Area of map

EXPLANATION

Fault—Undifferentiated

Fault—Deep regional. Paired arrows

 show direction of relative movement.

Major structural boundary or flexure 

 zone

Areas of uplift

Cross sections 

Tract 142sbK0005b, Amu 

 Darya tract

A-A' (fig. 3-5)

B-B' (fig. 3-6)

C-C' (fig. 3-6)

0 50 100 KILOMETERS

0 25 50 MILES

Political boundaries from U.S. Department of State (2009). 25 75

Albers Equal Area Projection.

Central meridian, 64° E., latitude of origin, 39° N.

CAsia_Fig 3-4 gjo2

Figure 3-4. Map showing structural features and locations of cross sections in and near the Amu Darya tract (142sbK0005b), 

Turkmenistan and Uzbekistan (adapted from Blackbourn, 2008).
40 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

METERS

 1,500

 1,700

 1,900

 2,100

SOUTHWEST NORTHEAST

A A'

Carbonate rocks with

 local reef complexes

Potash horizon

Evaporite succession 

 with halite

Carbonaceous 

 shale

Clastic sulfate-bearing 

 red beds and other

 sediments

EXPLANATION

0 4 KILOMETERS

0 1 2 MILES

1 2 3

VERTICAL EXAGGERATION ×9

DATUM IS SEA LEVEL

CAsia_Fig3-5 gjo2

Figure 3-5. Cross section A–A' through the Dengizkul Arch, Turkmenistan and Uzbekistan (see fig. 3-4 for 

location). The potash horizon, referred to in Vakhabov (1986) and Popov and others (1984), is immersed in 

a much thicker evaporite succession with halite. Depth of Jurassic salt and potash increases to the south 

(adapted from Belenitskaya, 2000).

Basin History

The Amu Darya tract lies within the Amu Darya Basin, 

the relatively undisturbed part of the original CASB west of 

the area of Miocene uplift (the Gissar Range) that separated 

the CASB into two subbasins. Salt water inflow during 

Kimmeridgian-Tithonian (Late Jurassic) time appears to have 

come from the southwestern part of the modern Amu Darya 

Basin (Vysotskiy and others, 1988; Baikov and Sedletskiy, 

2001). Subsequent basin infill, including that weathered from 

surrounding uplifted areas, such as the Kyzyl Kum Plateau 

to the north and the Uchadzhi-Kurama Arch to the south and 

southwest, has covered the Jurassic evaporite deposits with as 

much as 3 km of Cretaceous to Pleistocene sedimentary rocks. 

Whereas post-Miocene deformation continued in the eastern 

(Afghan-Tajik) subbasin, geophysical evidence (Ulmishek, 

2004) suggests that little structural deformation or halokinesis 

has affected the salt in the Amu Darya tract, except near 

its contact with the neighboring Gissar tract and, possibly, 

adjacent to the Repetek Fault Zone.

Salt

The Amu Darya tract is within the boundaries of the 

CASB (fig. 1-2) and is underlain by salt and other evaporates 

of the Upper Jurassic Gaurdak Formation. In places, the 

salt is at least 100–300 m thick (Zharkov and others, 1982a, 

1982b; Khudaikuliev, 1989). Stratabound potash-bearing salt 

is believed by Khudaikuliev (1986, 1989) and Zharkov and 

others (1982c) to be present within this unit. Whereas the 

morphology of potash-bearing salt is initially stratabound, 

dissolution, erosion, and halokinesis commonly result in less 

homogeneous and continuous mineralization, even when salt 

structures are not strongly developed. The entire area included 

within the tract is considered permissive for potash because we 

cannot precisely identify areas lacking potash within the tract 

boundaries. The depth of the Gaurdak evaporites increases in 

a southerly direction and, although much of the mineralization 

now lies at depths of 1 km or more, the potash remains mostly 

above the 3- km assessment depth limit (fig 3-6).
Chapter 3 41

Figure 3-6. Stratigraphic sections B–B' and C–C' through the Amu Darya Basin, Turkmenistan and Uzbekistan (see fig. 3-4 

for locations), derived from Zharkov and others (1982a) and Sedletskiy and Fedin (1981). Upper salt in this figure is the same 

as package 2, and lower salt is the same as package 4, of Gavril’cheva (1981), shown in figures 1-4 and 2-2.

B B'

C C'

Dengizkul 

Arch

BESHKENT 

TROUGH

 1,900

 2,000

 2,100

 2,200

 2,300

 2,400

 2,500

 2,600

 2,700

 2,800

 2,900

METERS

 2,000

 2,100

 2,200

 2,300

 2,400

 2,500

 2,600

 2,700

 2,800

 2,900

 3,000

 3,100

 3,200

 3,300

 3,400

METERS

EXPLANATION

Upper carbonate

Upper salt

Middle carbonate

Lower salt

Basal carbonate

PotashTURKMENISTAN UZBEKISTAN

TURKMENISTANUZBEKISTAN

DATUM IS ASSUMMED TO BE SEA LEVEL

CAsia_Fig3-6 _gjo2
42 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

The Repetek Fault Zone shown in figures 3-2 and 3-3 

is coincident in places with a narrow arch (Repetek Arch). A 

lineament of small salt domes occurs within this fault zone 

along the southern boundary of the Amu Darya tract and part 

of the southern boundary of the Gissar tract. The only salt 

dome known to host potash is the Donguzsyrt occurrence 

in the adjacent Gissar tract. We included cumulative 

potash thicknesses (>1 m) reported from individual layers 

in our gridding and contouring of total potash thickness 

data (fig. 3-7; contours intersecting the tract boundary are 

explained in the following volume section).

Assessment

This section describes the steps used to estimate 

undiscovered K2O resources in the Amu Darya tract, including 

data collection and analysis, and identification of the 

appropriate deposit model. Data available for the Amu Darya 

tract indicated that the stratabound potash-bearing salt model 

(appendix B) was most appropriate for this assessment. The 

Jurassic potash layers appear to be continuous and, where 

anticlines and (or) domes are present, these structures do not 

appear to be pronounced and mineralization is likely less 

disturbed than in the tracts to the east.

Although Zharkov and others (1982a, their fig. 4) report 

combined aggregate thicknesses of potash-hosting salt, we 

used their drill holes, in which no salt or potash is reported, 

to constrain the boundaries of the Amu Darya tract and thus 

constrain our calculation. The resulting potash thickness 

contours are within tract boundaries and approximate the 

“K-Prospective Zone III” of Vysotskiy and others (1988, their 

fig. 73) and Fedin (1981), increasing our confidence in our 

tract boundary.

Delineation of the Permissive Tract

The Amu Darya tract comprises the largely undisturbed 

part of the Beshkent Trough and regions farther northwest 

in the CASB (fig. 3-4) that contain potash occurrences. This 

tract is bounded to the east by the Gissar tract. Blackbourn 

(2008) and Belenitskaya (2000) show that the potash included 

in this tract is stratabound with gently undulating folds; the 

magnitude of structural modification apparently was not 

high enough to significantly disrupt the continuity of the 

potash‐bearing salt layers (fig. 3-5). The Amu Darya tract lies

south of the Kyzyl Kum Plateau, and includes all areas where 

potash one meter or greater in thickness has been reported 

or inferred. The K-Prospective Zone III of Fedin (1981) and 

Vysotskiy and others (1988) was the starting point to begin 

delineating the tract. The tract boundary was further refined 

by extending the boundaries to include known occurrences in 

the northeast and by using the high-resolution structural map 

of Blackbourn (2008), in addition to the structures shown by 

Steinshouer and others (2006). We used these structural maps 

to include the southern boundary of the Karabekaul Trough 

adjacent to the Repetek Fault, and to exclude areas where 

known total potash thickness is less than 1 m (Khudaikuliev, 

1986; see fig. 3-2). The boundaries were slightly expanded 

south and west to include all known occurrences of potash 

(Zharkov and others, 1982a, 1982b), and potash occurrences 

shown in figure 3-1, even though earlier Russian reports said 

that there was no potash, for instance, west of the city of 

Chardzhou. The tract is consistent with reports that potash is 

only found north of the Repetek Fault Zone (Vysotskiy and 

others, 1988). Overall, the tract is believed to represent the 

extent of stratabound potash beds 1 m or greater in thickness.

The Murgab Basin (fig. 3-3, 3-4) is relevant to the 

resource discussion of the Amu Darya tract because it is 

part of the CASB; however, it is not included in the potash 

assessment. The Murgab Basin lies south and west of the 

Amu Darya tract, and is separated from it by the Repetek 

Fault Zone. The K-Prospective Zone IV of Vysotskiy and 

others (1988) includes the northern edge of the Murgab Basin, 

but was coarsely sketched in the original figure. Much of 

the Repetek Fault Zone is occupied by, or coincident with, 

a narrow arch that separates Fedin’s (1981) and Vysotskiy 

and others’ (1988) K-Prospective Zone III (approximately 

coincident with the Amu Darya tract) from another zone to the 

south that Russian geologists referred to as “K-Prospective 

Zone IV.” This latter zone was their lowest-potential potash 

resource zone, and includes the Murgab Basin. 

The Repetek Arch is 450 km long and 12–15 km wide 

and is approximately coincident with the Repetek Fault 

Zone. Jurassic evaporite salt occurs in the Repetek Arch as a 

lineament of small salt domes that locally breach the surface 

and have 2,000–3,000 m in vertical relief (Semashev, 1983). 

This salt continues southwest and downdip into the Murgab 

Basin (Belelovskiy and others, 1971). Depth to basement, 

apparently ascertained by seismic-reflection data, ranges 

from 6 to 14 km. South of the Repetek Arch (coincident 

with the Repetek Fault Zone) is the Uchadzhi-Kurama Arch, 

which dips southward and forms the northern flank of the 

Murgab Basin. In the Mary-Serakh High, near the town 

of Mary, the base of the Jurassic lies at depths of 5–6 km, 

and is underlain by another 4–5 km of upper Paleozoic and 

Triassic sedimentary rock (Clarke, 1986; 1988). According 

to Vysotskiy and others (1988), no potash is reported in the 

Murgab Basin south and west of the Repetek Fault Zone. If 

potash is present, it lies well below the potash assessment 

depth limit of 3 km.

Definition of Resources

For the Amu Darya tract, known deposits were defined 

as those with documented reserves or resources with a 

category of A, B, C1, or C2 (the Russian classification system, 

see Henley, 2004, and also chapter 2 of this report). Using 

these criteria, no known deposits have been reported within 

the tract.
Chapter 3 43

62° E 64° E 66° E

39° N

38° N

UZBEKISTAN

TURKMENISTAN

Samarkand

Chardzhou

Karshi

Mary

Gaurdak

4

3

3

15

4

4

3

8

9

7 3

9

3 1

9

16

8

7

8

9

4

3

2

4

8 6

1 15 4

5

5

12

13 11

2

10 3

9

7

7

3

4 5

8

4

7

5

6

UZBEKISTAN

TURKMENISTAN

AFGHANISTAN

60° E 64° E 66° E

40° N

38° N

36° N

Area of map

0 20 40 60 80 KILOMETERS

0 20 40 MILES

Political boundaries from U.S. Department of State (2009).

Albers Equal Area Projection.

Central meridian, 64° E., latitude of origin, 39° N.

Potash thickness, in meters

EXPLANATION

7

Tract 142sbK0005b, Amu Darya tract

> 12 m

> 8 to 12 m

Potash thickness

> 3 to 8 m

 0 to 3 m

CAsia_Fig 3-7 gjo2

Figure 3-7. Map showing potash thickness contours in the Amu Darya tract (142sbK0005b), Turkmenistan and 

Uzbekistan. Contours were created by using drill-intercept data (appendix E) in ArcMap.
44 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Mineral Occurrences

Many potash occurrences have been reported in this tract 

(table 3-2, fig. 3-1). Most reported potash appears to have 

been identified by using gamma-ray logs acquired during oil 

and gas exploration. Most, if not all, potash occurrences in the 

area are described as non-piercing salt structures (Fedin, 1981; 

Vysotskiy and others, 1988), which are undulations or flexures 

in the evaporite salt over local basement highs (fig. 3-5). 

Many of these structures were identified indirectly from 

“geophysical surveys” (probably seismic-reflection surveys) 

or gamma-ray logs, the latter being a standard technique used 

for characterizing stratigraphy in oil and gas exploration, 

but also useful for identifying potash. Potash descriptions 

by Sedletskiy and Fedin (1981), Belenitskaya (2000), and 

Khudaikuliev (1986) suggest that virtually all potash in the 

tract is shallower than 3 km (figs. 3-5, 3-6).

Exploration History

Although active potash resource exploration and 

development are occurring in the Gissar tract to the east, 

the assessment team was not able to identify any potash 

exploration in the Amu Darya tract during the past decade 

and, possibly, the past 30 years. Publications since the 1990s 

that reference potash mineralization in this tract appear 

to be based on earlier work or on data collected during 

oil and gas exploration (gamma-ray logs). Exploration 

for and development of potash within the Amu Darya 

tract is less likely than within the Gissar tract because 

deposits at shallower depths in the Gissar tract make them 

more attractive.

Table 3-2. Evaporite salt structures reported to contain detectable potash in the Amu Darya tract, Turkmenistan 

and Uzbekistan.

Name Country Latitude Longitude Reference

Chashtepe Turkmenistan 39.199 63.584 Vysotskiy and others (1988)

Farab Turkmenistan 39.174 63.608 Vysotskiy and others (1988)

Khauzak Turkmenistan 39.142 63.669 Vysotskiy and others (1988)

Kishtuvan Turkmenistan 39.128 63.345 Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Kultai Turkmenistan 38.718 64.702 Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Metedzhan Turkmenistan 38.857 64.256 Vysotskiy and others (1988)

Narazym Turkmenistan 63.723 63.595 Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Sakar Turkmenistan 38.869 63.173 Vysotskiy and others (1988)

Saman-tepe Turkmenistan 38.953 63.705 Vysotskiy and others (1988)

Sundukli Turkmenistan 38.345 64.471 Vysotskiy and others (1988)

Uzonshor Turkmenistan 39.197 63.306 Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

West Kishtuvan Turkmenistan 39.283 63.197 Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Aizovat Uzbekistan 38.967 65.300 Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Beshkent Uzbekistan 38.821 65.653 Vysotskiy and others (1988)

Darbaza Uzbekistan 39.218 64.838 Vysotskiy and others (1988)

Dengizkul Uzbekistan 39.095 64.118 Vysotskiy and others (1988)

Dzhambulak Uzbekistan 38.867 66.401 Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Girsan Uzbekistan 38.617 65.167 Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Gumbulak Uzbekistan 38.580 66.853 Vysotskiy and others (1988)

Kamashi Uzbekistan 38.850 65.383 Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Karshi Uzbekistan 38.867 65.800 Roskill (1989); Schultz and others (2000); Lefond (1969)

Kultak Uzbekistan 38.750 64.883 Vysotskiy and others (1988)

Kuruksay Uzbekistan 38.483 65.900 Vysotskiy and others (1988)

Mobik Uzbekistan 38.570 67.005 Vysotskiy and others (1988)

Nishan Uzbekistan 38.665 66.862 Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Shady Uzbekistan 38.622 65.687 Vysotskiy and others (1988)

Shurtan Uzbekistan 38.978 65.725 Vysotskiy and others (1988)

South Pamuk Uzbekistan 39.298 63.652 Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

West Zevardy Uzbekistan 38.877 64.538 Vysotskiy and others (1988)

Yangikent Uzbekistan 38.700 66.061 Vysotskiy and others (1988)

Zevardy Uzbekistan 38.975 64.713 Vysotskiy and others (1988)
Chapter 3 45

Data Availability 

Most available data for the Amu Darya tract (table 3-3) 

were acquired in the 1970s and 1980s as a result of oil and 

gas exploration, and the assessment team believes that reports 

on the specific thickness of potash are largely derived from 

gamma-ray logs, though some potash was identified directly 

from drill core logs (for example, the Sakar occurrence, in 

Zharkov and others, 1982a, 1982b). Two 1:500,000-scale 

geologic maps (Seltmann and others, 2005) were available to 

the authors to use as a base, but only very coarse-resolution 

magnetic and gravity data were accessible. No original well 

logs were available. Figures from Russian reports lacked 

the detail and definitive geographic information needed to 

Table 3-3. Principal sources of information for the Amu Darya tract, Turkmenistan and Uzbekistan.

[CIS, Commonwealth of Independent States; GIS, geographic information system; NA, not applicable; USSR, Union of Soviet Socialist Republics]

Theme Name or title Scale Citation

Geology

Potassium-bearing basins of the world Unknown Vysotskiy and others (1988)

Central Asia Halogenic Basin Unknown Baikov and Sedletskiy (2001)

Tectonics of the Afghan-Tajik Depression Unknown Bekker (1996)

Afghan-Tajik Depression Unknown Nikolaev (2002)

Geologic map of Turkmenistan 1:500,000 Mirzakhanov (1989)

Mineral Deposits Database and Thematic Maps of Central Asia 1:500,000 Seltmann and others (2005)

Mineral

occurrences

An evaluation of the prospects for potash-bearing capabilities 

in the Upper Jurassic salt deposits in southern Central Asia

NA Fedin (1981)

World survey of potash resources NA British Sulphur Corporation (1979)

Uzbekistan to extend its chemical industry NA Ashurmatov (2006)

Salt dome region of southwestern Tadzhikistan NA Luchnikov (1981)

Potassium resource exploitation and utilization in Turkmenistan NA Zhang and others (2005)

Industrial minerals of the CIS NA Troitskiy and others (1998)

Deposits of potassium salts in the USSR NA Rayevskiy and Fiveg (1973)

Subsurface

geology

Deposits of potassium salts in the USSR Unknown Rayevskiy and Fiveg (1973)

Petroleum resource potential GIS of northern Afghanistan Various Steinshouer and others (2006)

Petroleum geology and resources of the Amu-Darya Basin,

Turkmenistan, Uzbekistan, Afghanistan, and Iran

Various Ulmishek (2004)

Hydrological conditions of gas accumulation in the Murgab

depression

Unknown Semashev (1983)

Facies zoning and conditions of sediment accumulation of 

Upper Jurassic salt-bearing formations in the territories of 

eastern Turkmenia

Unknown Gavril’cheva (1981)

Amu Dar’ya Basin and surrounding areas 1:1,600,000 Blackbourn (2008)

Geophysics Petroleum resource potential GIS of northern Afghanistan Various Steinshouer and others (2006)

Exploration

Prospects for potash-bearing capabilities in the Upper Jurassic 

salt deposits in southern Central Asia

Unknown Fedin (1981)

Jurassic Basins Unknown Vysotskiy and others (1988)

World survey of potash resources NA British Sulphur Corporation (1979)

Main structural features of the Upper Jurassic halogenous

formation and its role in forecasting buried reefs in the 

Amu Darya syneclise

Unknown Khudaikuliev (1986)

correlate map data and text was often abstracted from earlier, 

inaccessible or unpublished reports. Figure 3-2 shows the 

density of available information from which we built our 

resource estimate. Drill holes with measured and reported 

potash thicknesses of 1 m or greater are shown as yellow 

triangles. Open circles indicate drill holes where only the 

presence or absence of potash was noted, or other point 

sources of potash information including measured thicknesses. 

Drill holes and other point sources reporting at least one meter 

of potash (Khudaikuliev, 1986, 1989) are included within the 

tract boundary. The northwesternmost of these drill holes and 

occurrence data allowed us to extend the Amu Darya tract to 

the west beyond Chardzhou.
46 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Quantitative Estimation

Undiscovered potash resources (K2O) in tracts with 

thickness data for stratabound potash were estimated using 

an adaptive geometric estimation (AGE) method that follows 

the basic approach used by most Canadian NI 43-101 reports 

(Canadian Institute of Mining, Metallurgy and Petroleum, 

2005, 2012) to estimate in-place volume of reserves and 

resources. The AGE method (appendix A) can be modified to 

allow missing, incomplete, and unknown data to be estimated 

subjectively and (or) through the use of distributions based on 

partial data or analogous areas.

Our AGE assessment of undiscovered potash in the Amu 

Darya tract was based on these encouraging observations:

• The marine evaporite section of the Gaurdak Formation 

is as much as 1,200 m thick and extends over a vast 

region. The potash-hosting salt may be as much as 

800 m thick in places;

• Potash deposits, including Gaurdak, Karabil, Karlyuk, 

and Tyubegatan, are known in the adjacent Gissar tract 

directly east of the Amu Darya tract;

• Russian literature describes, within the area of the 

tract, potash occurrences with large areal extents 

and potash thicknesses in drill holes that suggest a 

substantial resource;

• Reported total thicknesses of potash-bearing layers in 

drill holes in the Amu Darya tract range from 1 to 17 m 

(fig. 3-6);

• Blackbourn (2008) shows structure in the tract consists 

of gently undulating folds.

Factors that do not support significant mineralization in the 

Amu Darya tract include the following: 

• At least two throughgoing faults, the Amu Darya and 

the Bagadsha Faults (Blackbourn, 2008) suggest local 

tectonic disruptions and dissolution;

• Older Russian literature refers to “lenses” or local 

thickening of potash in the tract area, which implies 

some level of dissolution and disruption of the 

potash mineralization; 

• Much of the potash intercept information was obtained 

incidental to oil and gas exploration, implying that 

there has been substantial drilling in the tract, which 

may have introduced pathways for local dissolution 

of potash;

• The tract is closer to the inflow source than the Gissar 

tract and thus the extent, grade, and thickness of the 

potash deposition may be more limited;

• Large gaps between some drill holes contribute 

to uncertainties about the character of 

potash mineralization.

Although the effect of the pessimistic factors cannot 

be quantified, the assessment team considered these factors 

during all phases of the assessment process. For the first, third, 

and fourth pessimistic factors listed above, this consideration 

included allowing for wider ranges of dissolution and 

non-deposition in the quantitative resource estimation process. 

A simplifying assumption, based on observations from other 

stratabound potash-bearing salt deposits with low levels of 

deformation in a similar climate, was that local lensing or 

changes in thickness are within the norm for stratabound 

potash-bearing salt deposits and are unlikely to affect the 

overall potash content of the tract.

Overview of the Adaptive Geometric Estimation (AGE) 

Method

In the AGE method, the area of the tract being evaluated 

is first multiplied by tract thickness to estimate volume. A 

grade is randomly selected from a grade distribution and the 

volume is then converted to tonnage using a density based 

on the selected grade. The in-place tonnage estimate is then 

adjusted downward to correct for areas of dissolution and 

nonmineralization, internal to the mineralized area (anomalies) 

and along the mineralization boundaries (embayments). Lastly, 

known resources are subtracted to determine the total amount 

of in-place, undiscovered K2O contained in the mineralized 

rock. All calculations and simulations were completed using a 

customized SYSTAT script (appendix F).

In the AGE method, unknown or incompletely known 

parameters may be (1) estimated from incomplete data 

available within the tract being studied, (2) based on global 

averages for the deposit type, or (3) estimated subjectively. 

These estimates may be single numbers, but when estimating 

undiscovered resources, they are more commonly (as in 

this assessment) distributions that represent observed or 

expected variation of a particular parameter, as well as 

the uncertainty of predicting its value(s).When assessing 

undiscovered resources, incomplete and missing data are the 

norm; therefore, tract delineation and parameter estimation for 

missing data are critical for obtaining robust final quantitative 

estimates of undiscovered resources. For most areas assessed, 

much of the uncertainty in the final estimate results from 

uncertainty in parameter estimations, and this uncertainty 

reflects the quantity and quality of the initial inputs. 

Parameter estimates for the Amu Darya tract (table 3-4) are 

discussed below.

Parameter Specification

Volume

The volume of potash resources in the Amu Darya tract 

was calculated using a contoured set of potash thicknesses 

bounded by the tract (fig. 3-7), which represents our best 

estimate of the extent of potash 1 m or greater in thickness. 

A raster surface, built from contours in ArcMap, was used 

to approximate an undiscovered potash volume of 201 km3. 
Chapter 3 47

Before we did this, however, we generated a theoretical 

kilometer-diameter topographic hemisphere with a 1-m 

grid, and used raster and TIN surface methods to calculate a 

volume that we could compare with the analytic volume of 

a hemisphere. The TIN volume calculation gave the closest 

value to the analytical volume (within less than 2 percent), and 

this was used for the Amu Darya volume calculation.

Although the tract boundary was drawn using several 

different sources of information, thickness contours were 

constructed only using known, often sparse thicknesses of 

potash, which leads to the apparent contouring disparities in 

figure 3-7, such as the 4-m and 5-m contours intersecting the 

tract boundary on the south. Abrupt changes in thicknesses 

may result from faulting on some of these boundaries. Abrupt 

thickness changes in the northern part of the tract likely results 

from down-dropping along faults.

Grade

Available grade data for potash intervals 1 m or greater in 

thickness in the Gissar and Amu Darya tracts were compiled 

and analyzed. The grade data (appendix D) form a normal 

distribution with a mean of 15.8 percent K2O and a standard 

deviation of 4.4 (fig. 2-8). This distribution provides a range 

of grades to sample in order to estimate the amount of K2O in 

the basin.

Two simplifications were necessary in order to use the 

grade data. First, because point grade data across the Amu 

Darya tract were very uneven and there was no information 

on the frequency of any grade in the grade data, grades in 

the grade distribution were assumed to represent a range of 

possible average grades in the resource estimation simulation. 

Using Monte Carlo simulation, different grades within this 

range were applied to the entire tract. Secondly, because we 

did not know the potash mineral composition at any given 

point in the tract, it was assumed that average grades below 

16.9 percent K2O resulted from carnallite mineralization 

and grades of 16.9 percent or higher resulted from sylvite 

mineralization. The density of carnallite is 1.6 g/cm3; sylvite 

is 1.99 g/cm3, and halite is 2.165 g/cm3 (table 1-1). With this 

information, an appropriate density was determined for a 

selected grade to estimate undiscovered resource tonnage.

Anomalies and Embayments

Unmineralized areas within stratabound potash 

deposit tract boundaries that are not along the edges of the 

mineralization are termed “anomalies” for the purposes of 

this USGS potash assessment. The term “embayment” refers 

to localized areas on tract margins where potash was never 

deposited because of local paleotopography, physical erosion, 

and other reasons including dissolution. See the chapter 2 

(Gissar tract) where this issue was visited earlier. A more 

complete discussion of anomalies and embayments with 

references is in the method summary (appendix C).

Simulation

The AGE approach (appendix C) was used to estimate 

undiscovered stratabound K2O in the Amu Darya tract. The 

process starts with a volume of potash-mineralized rock 

as a function of area and thickness. Values, or estimated 

distributions of values, have previously been determined or 

modeled for grade, anomalies, and embayments, and this 

information is entered into the simulation variables.

After determining tract volume and other parameters, the 

next step is to run a Monte Carlo simulation that starts with 

a random selection of a grade from the grade distribution. 

This grade is used to determine if carnallite or sylvite is the 

dominant ore mineral, which determines the density value 

to be used to convert the volume of potash-mineralized 

rock to tonnage. The simulation program actually calculates 

the volume and tonnage of sylvite (or carnallite) and of 

halite. Resulting tonnages are then adjusted for the expected 

proportions of anomalies and embayments (selected from 

distributions using Monte Carlo simulation), and finally, 

total ore and contained K2O tonnages are calculated. Known 

resources are then subtracted to determine an estimate 

of in-place potash as K2O. This process is repeated for 

5,000 iterations to form a distribution of possible K2O values.

Monte Carlo simulations were run in SYSTAT, a 

statistical analysis software package. A generalized version 

of the SYSTAT script and a table defining the variables in the 

script is in appendix F.

Table 3-4. Parameters used to estimate the undiscovered K2O resources of the Amu Darya tract, 

Turkmenistan and Uzbekistan.

[GIS, geographic information system; min, minimum; max, maximum; %, percent]

Parameter Source Description

Thickness Drill holes, other sources Data

Volume GIS calculation Point thickness data, including drill hole (see chapter 5)

Grade (K2O) Drill holes, other sources Normal distribution (mean 15.84%; standard deviation 4.42)

Anomalies Global distribution Triangular distribution (min 5%; mode 20%; max 35%)

Embayments Global distribution Triangular distribution (min 5%; mode 15%; max 30%)
48 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Results

Our calculation of potash-salt volume for the Amu Darya 

tract is 201 km3. Converting volume to tonnage and using 

a Monte Carlo simulation to estimate the probable range of 

contained K2O (fig. 3-8) yields a mean estimated resource of 

41.1 Bt of K2O (median of 37.8) undiscovered potash in the 

Amu Darya tract (table 3-1). At 90-percent confidence, there 

is 22.7 Bt of K2O present; at 10-percent confidence, there is 

64.9 Bt of K2O present. 

K20 content, in billion metric tons

N = 5,000

Mean = 41.1

Median = 37.8

StdDev = 12.0 

0.02

0.04

0.06

0.08

Probability

10 20 30 40 50 60 70 80

Histogram showing distribution of estimated in-place K2O 

content of undiscovered stratabound potash deposits, Amu 

Darya tract, Turkmenistan and Uzbekistan.

CAsia_Fig 3-8 gjo

Figure 3-8. Histogram showing distribution of 

estimated in-place K2O (potassium oxide) content 

of undiscovered potash deposits for the Amu Darya 

tract, Uzbekistan and Turkmenistan. N, number of 

in-place K2O samples; StdDev, standard deviation.

Discussion

The Amu Darya tract contains a significant amount of 

potash. Our mean estimate of 41.1 Bt of K2O is similar to 

our estimate of as much as 27.9 Bt of K2O for the Gissar 

tract, given that the Amu Darya tract is almost 50 percent 

larger than the Gissar tract. However, this mean for the Amu 

Darya tract may overestimate or underestimate the resource 

actually contained in this tract. We expect that the true 

estimate lies within the distribution of estimated contained 

K2O that was generated from the simulation. All grades in 

the grade distribution were obtained from the neighboring 

Gissar tract, where known deposits of the CASB occur. It is 

also possible that the grade distribution for the Amu Darya 

tract is significantly different than that for the Gissar tract. 

Given the lack of specific data, using the grade distribution 

from the contiguous and largely analogous Gissar tract was 

deemed appropriate. A similar uncertainty exists for most of 

the other estimated parameters, and readers should keep this in 

mind when using the results of this assessment. That said, the 

assessment team is confident that the predicted distribution of 

undiscovered potash resources encompasses the uncertainty of 

the estimate and that the mean of this distribution represents 

the best possible estimate.
Chapter 4. Potash-Bearing Salt Assessment for the Afghan-Tajik 

Tract (142haK0005c)— Uzbekistan, Tajikistan, and Afghanistan

By Jeff Wynn,1 Greta J. Orris,2 Pamela Dunlap,2 and Mark D. Cocker2

1

U.S. Geological Survey, Vancouver, Washington, United States.

2

U.S. Geological Survey, Tucson, Arizona, United States.

Introduction

A qualitative assessment of undiscovered potash deposits 

was conducted for deeply buried salt in the eastern part of the 

Central Asia Salt Basin (CASB), which underlies much of the 

modern Afghan-Tajik Basin of Tajikistan and Afghanistan. 

The Afghan-Tajik tract shares its western boundary with 

the richly-mineralized Gissar tract (see chapter 2), and 

the assessment team believes that potash-hosting Jurassic 

evaporite units are likely present, but commonly at depths in 

excess of the 3-km assessment depth limit, especially in the 

western half of the tract near known reserves and resources of 

potash in the Gissar Range of Turkmenistan and Uzbekistan. 

In the Afghan-Tajik tract, the potential for potash is greatest 

where halokinesis and (or) faulting have resulted in potash 

occurring at depths of less than 3 km. Six, small, named 

potash occurrences have been reported (Sedletskiy, 1969; 

Rundkvist, 2001). Lack of exploration in the area and potential 

complexities and uncertainties inherent in potash deposits 

within halokinetic salt structures suggest that potential 

resources in this tract are unlikely to be developed.

Location 

The Afghan-Tajik tract is east of the Gissar Range with 

parts of the tract in Uzbekistan, Tajikistan, and Afghanistan 

(fig 4-1). It comprises the eastern part of the original CASB, 

which is now separated by the Gissar Range into two 

modern basins: (1) the Amu Darya Basin in southern and 

eastern Turkmenistan and southwestern Uzbekistan, and 

(2) the Afghan-Tajik Basin in northern Afghanistan, western 

Tajikistan, and part of Uzbekistan (fig. 1-1).

Basin History 

The Afghan-Tajik tract covers more than 68,000 km2

and includes most of the modern Afghan-Tajik Basin. The 

Jurassic sedimentary rocks and evaporites of the basin are 

typically overlain by several kilometers of sedimentary 

rocks. Subsequent to the Gissar uplift of Miocene time, 

the Afghan-Tajik Basin has been continually compressed 

by the complex collision of the Indian subcontinent with 

Asia. Sedimentary rocks of the basin have been folded 

and compressed by as much as 50 percent in the east-west 

direction forming the Obigarm and Kafirnigan Mega 

Anticlines (open to the east) (Bekker, 1996; fig. 4-2). Geologic 

mapping and two‐dimensional seismic profiles show that

Upper Jurassic to Lower Cretaceous(?) evaporite units in 

the Afghan-Tajik tract have undergone extreme halokinesis 

during this tectonic compression (fig. 4-3A). Most of the 

potentially potash-bearing salt in this evaporite sequence lies 

far below the 3-km assessment depth limit, but a few diapirs 

or fault blocks may have raised potash to the surface or near 

surface in the extreme eastern and southeastern parts of the 

tract. It is also possible that, locally, some potash-bearing 

Jurassic evaporites lie in shallow areas near the crests of large 

regional anticlines (Bekker, 1996) or in areas uplifted by block 

tectonics (Klett and others, 2006).

Salt 

Nikolaev (2002) reported that Jurassic salt beds extend 

under most of the Afghan-Tajik Basin. Most Jurassic 

sedimentary rocks that include the salt and potash units in 

the Afghan-Tajik tract lie at depths of 4–7 km (fig. 4-3B; 

Bekker, 1996; Nikolaev, 2002). However, the depth of salt 

burial and tectonic movement along basement and other 

faults has caused halokinesis within the tract, and has 

brought some Jurassic evaporites to the surface, or at least 

above the 3-km assessment depth limit. There are several 

exposures of probable Upper Jurassic (to Lower Cretaceous?) 

salt in the Afghan-Tajik Basin, most notably in salt domes 

west of Kulyab, Tajikistan, and in three domes 50–75 km 

east‐southeast of Konduz in northern Afghanistan (fig. 1-2).
50 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan Tanapchi Nurek Alimtay Khodzhamumyn Khodzhamartis

!

!

!

!

!

!

!

!

!

Karshi

Termez

Mazar-E Sharif

Dushanbe

Kulyab

Qurghonteppa

Konduz

Gaurdak

A

F

G

H

A

NISTA

N

U

Z

B

E

KISTA

N

TAJIKISTA

N

70° E 68° E 66° E

38° N36° N

70° E 65° E

40° N35° N

AFG

H

A

NISTA

N

KA

Z

A

K

HSTA

N

U

Z

B

E

KISTA

N

PA

KISTA

N

TAJIKISTA

N

Area of map

0 20 40 60 80 KILOMETERS0 20 40 MILES

EXPLANATION

Assessed potash tract 142haK0005c,  Afghan-Tajik tractOther potash tracts

Potash occurrence; occurrences associated with other tracts are  shown in gray

Potash deposit associated  with other tract

Political boundaries from U.S. Department of State (2009).Albers Equal Area Projection.Central meridian, 68° E., latitude of origin, 39° N.

CAsia_Fig4-1 gjo3

Figure 4-1. Map showing location of the Afghan-Tajik tract (142haK0005c), Uzbekistan, Tajikistan, and Afghanistan and and potash occurrences.
Chapter 4 51

TURKMENISTAN

UZBEKISTAN

TAJIKISTAN

AFGHANISTAN

Karshi

Termez

Mazar-E-Sharif Konduz

Kulyab

Dushanbe

Qurghonteppa

66° E 68° E 70° E

39° N

38° N

37° N

Gissar

Hindu Kush / Badakhshan

North Afghan High

Kafirnigan 

Mega-anticline

GISSAR RANGE

CHARDZHOU STEP

Obigarm Mega-anticline

North Afghan High

Kokchin

Graben

North Karabil Trough

North Afghan High

Repetek Fault Zone

Obruchev Depression

Baisun 

Graben

BESHKENT TROUGH

66° E 69° E

37° N

36° N

AFGHANISTAN

TAJIKISTAN UZBEKISTAN

Area of map

0 40 80 KILOMETERS

0 20 40 MILES

20 60

EXPLANATION

Relative highs—Anticlines, 

 uplifts, and monoclines

Relative lows—Synclines, 

 depressions, and troughs

Pre-Jurassic sedimentary and 

 crystalline basement

Fault zone

Tract 142haK0005c, Afghan-Tajik tract

Political boundaries from U.S. Department of State (2009).

Albers Equal Area Projection.

Central meridian, 65° E., latitude of origin, 30° N.

CAsia_Fig 4-2 gjo2

Figure 4-2. Map showing structural features in and near the Afghan-Tajik tract, Uzbekistan, Tajikistan, and Afghanistan, adapted 

from Steinshouer and others (2006).
52 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

B

A'

B'

A

!

Feyzabad

UZBEKISTAN

AFGHANISTAN

TAJIKISTAN

68° E 70° E

38° N

Khodzhasartis

Tanapchi, 

Nurek Alimtay Khodzhamumyn

Severopushionskaya

AFGHANISTAN

TAJIKISTAN

UZBEKISTAN

66° E 68° E 70° E

38° N

36° N

Area of map

0 40 80 KILOMETERS

0 40 MILES

20 60

20

EXPLANATION

Syncline (Mesozoic-Cenozoic)— 

 Filled with Quaternary, 

 Pliocene, and Miocene

 sediments

Anticline (Mesozoic-Cenozoic)

Thrust fault

Nappe

Regional fault—Bounding 

 Afghan-Tajik Basin; 

 includes wrench faults,

 upthrows, and thrusts

Cross-section line

Tract 142haK0005c, Afghan-

 Tajik tract

A A' Salt diapir with reported 

 potash

Salt diapir exposed at 

 surface, no reported 

 potash

Political boundaries from U.S. Department of State (2009).

Albers Equal Area Projection.

Central meridian, 64° E., latitude of origin, 39° N.

CAsia_Fig4-3a gjo3

A

Figure 4-3. A, Map showing Mesozoic-Cenozoic structures and locations of cross sections shown on fig. 4-3B, and the AfghanTajik tract, Uzbekistan, Tajikistan, and Afghanistan, adapted from Bekker, 1996. B, Cross-sections showing depths to salt for the 

central and northeastern parts of the Afghan-Tajik tract (see fig. 4-3A for locations), adapted from Bekker (1996).
Chapter 4 53

NORTHWEST SOUTHEAST

KILOMETERS

4

SEA LEVEL

4

8

12

8

SEA LEVEL

VERTICAL EXAGGERATION ×1.3

0 20 40 KILOMETERS

0 20 MILES

A A'

WEST-NORTHWEST EAST-SOUTHEAST

B B'

VERTICAL EXAGGERATION ×1.3

0 20 40 KILOMETERS

0 20 MILES

4

4

8

12

KILOMETERS Alimtay 

diapir

Severopushionskaya

diapir

EXPLANATION

Quaternary, Pliocene, and Miocene

 sedimentary strata

Paleogene sedimentary strata

Cretaceous sedimentary strata

Upper Jurassic salt

Jurassic sedimentary strata

Subsalt complex of sedimentary

 rocks and basement

Fault—Dashed where uncertain

CAsia_Fig 4-3b gjo2

(old 4-4)

B

Figure 4-3.—Continued

Cross sections in Bekker (1996) suggest that any Jurassic 

salt above the 3-km assessment depth is rare (fig. 4-3B). Salt 

diapirs near Kulyab are found along anticlines associated 

with major faults (Leith and Simpson, 1986; see cross section 

A–A′ on fig. 4-3). These salt structures are narrow, several 

kilometers high, and pierce the entire postsalt sequence. The 

Khodzamumyn dome (fig. 4-3A) forms a mountain that rises 

880 m above the river valley, and the Khodzasartis dome rises 

400 m above the adjacent plain (Baikov and Sedletskiy, 1992); 

both have reported occurrences of potash. Potash has been 

reported in the cupola of the Alimtay diapir (fig. 4-3A).

Several salt diapirs of probable Upper Jurassic or 

possibly Lower Cretaceous age are exposed approximately 

60 km west-southwest of Konduz in northern Afghanistan 

(fig. 1-2). The Taqcha Khana salt dome (also known locally 

as Namakab, after the local river that cuts it and makes the 

downstream water too salty to drink; fig. 1-2) is several 

kilometers in diameter (Kulke, 1972). This salt deposit is 

currently being mined for rock salt by using primitive (hand) 

mining methods. The rock salt is finely crystalline and lightgray to red-brown (Mennessier, 1963). Rock salt of the Chal-I 

and Chal-II occurrences (fig 1-2) has been mined in the past 

and workings extend to depths of about 20 m (Mikhalov and 

others, 1967; Abdullah and others, 1977).

Assessment 

The modest amount of specific information available 

for the Afghan-Tajik tract is not sufficient to conduct a 

quantitative estimate of undiscovered potash resources 

in halokinetic potash-bearing salt deposits (appendix B). 
54 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Russian seismic data (fig 4-3B; Bekker, 1996) suggest that 

virtually all Jurassic salt lies well below the 3-km assessment 

depth limit, notably excepting diapirs and fault blocks raised 

closer to the surface by halokinesis and tectonics. While the 

assessment team was able to identify areas where tectonics 

and halokinesis could have resulted in potash-bearing salt 

above the assessment depth limit, no further refinement of the 

tract was possible.

Delineation of the Permissive Tract

The boundary of the Afghan-Tajik tract represents our 

best estimate of the extent of Upper Jurassic salt within 

the Afghan-Tajik Basin. We know that the Upper Jurassic 

salt hosts significant potash deposits in the Gissar tract 

immediately to the west, and that potash occurs in salt diapirs 

in at least six locations within this basin (table 4-1). Potash is 

most likely to occur within salt structures in this tract, but the 

total number of salt structures is unknown; therefore, we used 

the probable extent of Upper Jurassic salt as the main limit of 

potash-bearing salt structures of that age. The Afghan-Tajik 

tract boundaries (fig. 4-1) were thus determined by contacts or 

faults dividing Upper Jurassic and younger rocks from Middle 

Jurassic and older rocks. This approach implicitly accepts 

Nikolaev’s (2002) assertion that Jurassic salt underlies most of 

the basin.

The western boundary of the Afghan-Tajik tract shares 

the eastern boundary of the Gissar tract and is roughly 

coincident with the eastern boundary of the Baisun Graben 

(fig. 4-2). Northern, northeastern, and eastern tract boundaries 

are defined by the extent of Upper Jurassic sedimentary 

rock map units as shown on the Central Asia geologic map 

of Seltmann and others (2005). The southern boundary 

in Afghanistan was inferred from the geologic map of 

Afghanistan by Doebrich and Wahl (2006) to be the edge of 

the North Afghan High (fig. 4-2).

Mineral Occurrences

There is no historic production of potash in the AfghanTajik tract, and there are no known potash deposits. Six 

occurrences have been reported (table 4-1); only one is 

specifically located (fig. 4-1). Vysotskiy and others (1988) 

report that three horizons of rock salt in the cupola of the 

Alimtay salt dome contain sylvite. Concentrations of as 

much as 10.4 percent are reported, but it is not clear if this 

percentage represents the sylvite-carnallite content or the 

concentration of potash as K2O or KCl. In addition, Mineral 

Mining plc has reported potash at an undisclosed location in 

the western part of the Afghan-Tajik tract (Newswire Today, 

2011) and stringers of potash have been reported in some 

salt domes in the eastern part of the tract (Sedletskiy, 1969). 

Potash deposits with known reserves and (or) resources have 

been reported in several locations in the adjacent Gissar tract 

to the west where there is one mine in production and at least 

one additional mine being developed.

Exploration History

There was no reported exploration for potash within the 

Afghan-Tajik tract through 2010; available information on 

halokinetic salt structures is largely a product of Soviet-era 

oil exploration and the few surface salt exposures in this arid 

environment. Several structures have been mined for salt by 

using primitive (hand) mining methods.

In 2011, Mineral Mining plc was reported to be exploring 

a potash prospect in Tajikistan “90 km southeast of the 

Uzbekistan border” (Newswire Today, 2011). Exploration 

has included “geophysical work” and a single 1,065-m-deep 

drill hole that encountered several 3–6-m-thick intervals 

containing 40–60 percent potash salts, apparently disrupted by 

postdepositional faulting. Although no age or specific location 

was given in the report, the described location of this prospect 

Table 4-1. Known potash occurrences within the Afghan-Tajik tract, Uzbekistan, Tajikistan, and Afghanistan.

Name Latitude Longitude Comments Reference

Alimtay 37.749 69.432 Sylvite reported in three horizons of this salt

structure

Vysotsky and others (1988); Bekker (1996)

Khodzhasartis 37.946 69.662 Dispersed impregnations and very fine

intercalations of sylvite in rock salt

Sedletsky (1969); Rundkvist (2001)

Khodzhamumyn 37.729 69.637 Dispersed impregnations and very fine

intercalations of sylvite in rock salt

Sedletsky (1969); Rundkvist (2001)

Nurek 37.937 69.530 Small amounts of potash minerals reported;

potash averages less than 1 percent

Sedletsky (1969); Rundkvist (2001)

Tanapchi 37.916 69.503 Dispersed impregnations and very fine

intercalations of sylvite in rock salt

Sedletsky (1969); Rundkvist (2001)

Unnamed occurrence1 “Several” intervals containing 40–60 percent

potash salts

Newswire Today (2011)

1

Location is described as “90 km southeast of the Uzbekistan border.”
Chapter 4 55

is within the area included in this tract. Plans to continue 

exploration with an additional drill hole were mentioned in 

the short report, but no other information on the occurrence 

was provided.

Data Availability

Most data for the Afghan-Tajik tract (table 4-2) were 

acquired in the 1970s and 1980s incidental to oil and gas 

exploration. The authors believe that cross sections (fig. 4-3B) 

showing depth to Jurassic salt along with subsurface structure, 

are largely derived from seismic and gravity profiling and 

well logs (generally these are referred to as “geophysical 

data” or “геофизическиm данныm”). Two 1:500,000-scale 

geologic maps (Seltmann and others, 2005) were available to 

the authors to use as a base, but only very coarse-resolution 

magnetic and gravity data were accessible. Original seismic 

data and well logs were not available. In these older Russian 

reports, figures were crudely sketched with little to register 

them against, and text was often abstracted from earlier, 

apparently unpublished, reports.

Discussion

Based on seismic-reflection data, most of the Jurassic 

salt in the Afghan-Tajik tract lies below the 3-km assessment 

depth limit (Bekker, 1996; figs. 4-3A,B). Although only six 

occurrences of potash are known within the tract, there is still 

the possibility that significant deposits of potash might exist. 

The Gissar tract to the west includes all known potash deposits 

in the CASB. They are Jurassic in age and were uplifted in 

the Miocene during the formation of the Gissar Flank Mega 

Anticline (Fedin, 1981; Vysotskiy and others, 1988; Seltmann 

and others, 2005; see fig. 4-2). Continuation of this Jurassic 

mineralized salt, albeit at greater depth, into the Afghan-Tajik 

tract is geologically reasonable. There is no information to 

judge how far east any potash extends, though the reported 

occurrence of sylvite at Alimtay (fig. 4-1) indicates potential 

to at least that longitude. No significant potash mineralization 

has been reported in the Jurassic salt diapirs being worked for 

salt in Tajikistan and Afghanistan, although the occurrence of 

potash has been reported at a handful of sites. Areas of potash 

deposition can be very large, such as the potash mineralization 

in the Elk Point Basin of Canada, where potash in the Patience 

Lake Member of the Prairie Formation occurs over an area 

larger than 125,000 km2. Alternatively, areas of mineralization 

can be small; potash in the Mulhouse Basin of France and 

Germany only occupies an area of about 438 km2. 

The assessment team felt that one or more deposits 

exist within 3 km of the surface, especially in shallow areas 

resulting from the Gissar uplift on the west. However, based 

on the lack of data and exploration, the complexities of 

potash deposits hosted by halokinetic salt, and the relative 

inaccessibility of the area, it is unlikely that potash deposits 

within this tract will be discovered and developed in the short 

to medium term.

Table 4-2. Principal sources of information for the Afghan-Tajik tract, Uzbekistan, Tajikistan, and Afghanistan.

[GIS, geographic information system; NA, not applicable]

Theme Name or title Scale Citation

Geology

Jurassic Basins Unknown Vysotskiy and others (1988)

Some aspects of the genesis of halogenic sequences Unknown Baikov and Sedletskiy (2001)

Tectonics of the Afghan-Tajik depression Varies Bekker (1996)

Afghan-Tajik Depression Unknown Nikolaev (2002)

Tellus sedimentary basins of the world Varies Fugro-Robertson, Ltd. (2010)

Mineral deposits map of Central Asia 1:500,000 Seltmann and others (2005)

Geologic and mineral resource map of Afghanistan 1:850,000 Doebrich and Wahl (2006)

Geologic map of Turkmenistan 1:500,000 Mirzakhanov (1989)

Subsurface

geology

Petroleum resource potential GIS of northern Afghanistan Varies Steinshouer and others (2006)

Petroleum geology and resources of the Amu-Darya Basin Varies Ulmishek (2004)

Geophysics Petroleum resource potential GIS of northern Afghanistan Various Steinshouer and others (2006)

Exploration

Lithofacies and potassium potential of Upper Jurassic halogen

deposits in Central Asia

Unknown Sedletskiy and Fedin (1981)

Potassium-bearing basins of the world Unknown Vysotskiy and others (1988)

World survey of potash resources Unknown British Sulphur Corporation (1979)

Mineral Mining PLC—Research continues at Tajikistan 

potash deposit

NA Newswire Today (2011)

Mineral 

occurrences

Jurassic Basins NA Vysotskiy and others (1988)

Potash salts of Central Asia NA Sedletskiy (1969)

Mineragenetic map of Russian Federation and adjacent states 1:2,500,000 Rundkvist (2001)
This page intentionally left blank
Chapter 5. Spatial Databases for Resource Assessments

By Pamela Dunlap1

1

U.S. Geological Survey, Tucson, Arizona, United States.

Introduction

Spatially referenced data for the distribution of mineral 

deposits and areas permissive for undiscovered deposits are 

important elements of mineral resource assessments. When 

used in conjunction with a common set of descriptive data and 

a variety of other types of spatial data, this information can be 

used to conduct detailed resource assessments to understand 

the likely distribution and availability of potash resources to 

meet future needs and to help inform resource policy.

The datasets and documentation presented in this 

report were developed primarily for use with Esri software, 

in particular ArcGIS version 10 or higher. Geographic 

information system (GIS) terminology specific to Esri 

software is used throughout this report; definitions of GISrelated terms and concepts are available online at http://

support.esri.com/en/knowledgebase/Gisdictionary/browse [last 

accessed December 3, 2015].

Overview of Spatial Databases

The spatial databases (digital data files) released in 

this report are listed and briefly described in table 5-1. Each 

spatial database is provided in vector format as a feature class 

in the Esri file geodatabase (FGDB) CentralAsia_potash.

gdb. The geodatabase is packaged with metadata files and a 

brief descriptive ASCII text file in the compressed archive file 

sir20105090aa_gis.zip, available at http://dx.doi.org/10.3133/

sir20105090AA.

FGDC-compliant (Federal Geographic Data Committee; 

www.fgdc.gov) metadata provides information about the 

spatial databases. Embedded metadata in extensible markup 

language (XML) format can be viewed in ArcGIS 10. 

Metadata are also provided in standalone XML and Adobe 

PDF (portable document file) format files (table 5-1).

CentralAsia_deposits Spatial Database

The deposits spatial database, the FGDB feature class 

CentralAsia_deposits, contains vector (point features) and 

descriptive data for 66 potash sites representing areas, leases/

concessions/permits, mines, mineral occurrences, and salt 

structures in the Central Asia Salt Basin. Brief descriptions 

of fields and values in this spatial database are provided in 

table 5-2; a “<NULL>” entry in any field indicates that the 

value is not known.

CentralAsia_thickness Spatial Database

The regional thickness spatial database, the FGDB 

feature class CentralAsia_thickness, contains vector 

information (point features) for thickness of the potash-bearing 

intercepts in drill holes and at mineral occurrence sites as 

compiled from Rayevskiy and Fiveg (1973), Sedletskiy 

and Derevyagin (1980), Fedin (1981), Sedletskiy and Fedin 

(1981), Zharkov and others (1982a, 1982b), Khudaikuliev 

(1986), and Vysotskiy and others (1988). Brief descriptions 

of fields and values in this spatial database are provided in 

table 5-3.

CentralAsia_tracts Spatial Database

The permissive tracts spatial database, the FGDB feature 

class CentralAsia_tracts, contains vector information (polygon 

features) for each tract, in addition to descriptive data used 

in the mineral resource assessment and the quantitative 

calculations (table 2-1). Brief descriptions of fields and values 

in the spatial database are provided in table 5-4.
58 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Table 5-1. List and description of spatial databases (digital data files) in this report.

File name File description

Compressed archive file containing spatial databases, associated metadata files, and readme.txt

sir20105090aa_gis.zip Geographic information system (GIS) and associated files: Esri

file geodatabase (FGDB), metadata (*.pdf and *.xml), and

readme.txt (ASCII text).

File geodatabase (FGDB) (located in folder \CentralAsia)

CentralAsia_potash.gdb FGDB (ArcGIS 10) contains spatial databases prepared for and

used in the mineral resource assessment for undiscovered

potash in the Central Asia Jurassic Salt Basin, Turkmenistan,

Uzbekistan, Tajikistan, and Afghanistan.

FGDB feature classes in CentralAsia_potash.gdb

CentralAsia_deposits FGDB feature class (points) for sixty-two potash deposits

(includes areas, leases/concessions/permits, mines, mineral

occurrences, and salt structures).

CentralAsia_thickness FGDB feature class (points) of thickness data for potash-bearing

intercepts in drill holes and at mineral occurrence sites.

CentralAsia_tracts FGDB feature class (polygons) of assessment data and results for

three tracts permissive for undiscovered potash.

Metadata—Adobe Acrobat PDF (*.pdf) and extensible markup language (XML) format (*.xml) files 

(located in subfolder \CentralAsia\Metadata)

CentralAsia_deposits_metadata.pdf/.xml Metadata for spatial database for deposits.

CentralAsia_thickness_metadata.pdf/.xml Metadata for spatial database for thickness of potash

mineralization.

CentralAsia_tracts_metadata.pdf/.xml Metadata for spatial database of tract assessment data and

results.

ASCII text file (located in subfolder \CentralAsia)

readme.txt Brief description of report and associated digital data.
Chapter 5 59

Table 5-2. User-defined fields in the feature attribute table for CentralAsia_deposits.

Field Description

ID_NO Unique numeric identifier.

SITE_NAME Mineralized feature.

ALT_NAMES Known synonym.

TYPE_REC Site type.

COUNTRY Country.

LATITUDE Positive number represents latitude north of the equator.

LONGITUDE Positive number represents longitude east of the Greenwich meridian.

BASIN Evaporite basin.

BASIN_TYPE Type of basin.

TRACT_NAME Informal name of permissive area for undiscovered potash.

DEP_TYPE Type of mineralization style.

COMMODS Significant commodities; multiple commodities are listed in approximate order of significance.

K_MINERALS Potash mineral(s) known to be present.

OTHER_MINS Other mineral(s) of significance or interest.

AGE Age of evaporite sequence, as taken from source(s).

UNIT Formal and (or) informal name of stratigraphic rock unit(s) that contain mineralization (as derived from sources).

LITH Lithology and (or) composition of the host rock and (or) unconsolidated sediment.

SALT_STR Name of salt structure, if any, associated with mineralized site (where DEP_TYPE is ‘evaporite-halokinetic’).

K_THK_M Reported thickness of potash horizon(s).

K_DEPTH_M Reported depth to top of potash.

GEOL_NOTES Additional geologic information.

AV_K2O_PCT Reported average potash (K2O) not associated with reported production or reserve information, in percent.

FIGURES Image(s) portraying representative geology, in PDF format; includes name of folder where file is stored

(no figures were available/included for technical review).

P_STATUS Production and (or) development status, queried where uncertain, year included when known.

P_FIRST_YR Year(s) of first known production.

P_LAST_YR Year(s) of last known production.

COMPANY Last known owner and (or) operator; may include year for which owner or operator was confirmed.

P_ORE_MT Reported production of ore, in million metric tons; numbered entries correspond to those in P_REFS.

P_K2O_MT Reported production of potash, in million metric tons; numbered entries correspond to those in P_REFS.

P_K2O_PCT Grade of reported production of potash (K2O), in percent; numbered entries correspond to those in P_REFS.

P_REFS Abbreviated citation(s) for source reference(s) for production data; full citations are provided in report; numbered

entries correspond to numbered entries in P_ORE_MT, P_K2O_MT, P_K2O_PCT, and P_YEARS.

P_YEARS Year(s) for which production data were reported; numbered entries correspond to those in P_REFS.

MEAS_INV Categorical field denoting if reserves or resources were reported.

RR_ORE_MT Reported reserves and (or) resources of ore, in million metric tons; modifying abbreviations are listed in table 4 in

report; numbered entries correspond to numbered entries in RR_REFS.

RR_K2O_MT Reported reserves and (or) resources of potash (K2O), in million metric tons; modifying abbreviations are listed in

table 4 in report; numbered entries correspond to numbered entries in RR_REFS.

RR_K2O_PCT Reported reserves and (or) resources of potash (K2O), in percent; numbered entries correspond to numbered entries

in RR_REFS.

RR_REFS Abbreviated citation(s) for source reference(s) for resource and (or) reserve data; full citations are provided in

report; numbered entries correspond to numbered entries in RR_ORE_MT, RR_K2O_MT, RR_K2O_PCT, and

RR_YEARS.

RR_YEARS Year(s) for which resource and (or) reserve data were reported, if known; numbered entries correspond to those in

RR_REFS.

MISC_NOTES Additional information.

SHORT_REFS Abbreviated citation(s) for source reference(s).
60 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Table 5-4. User-defined fields in the feature attribute table for CentralAsia_tracts.

Field Description

Coded_ID Coded, unique identifier assigned to permissive tract.

Tract_name Informal name of permissive tract.

Unregcode Three digit United Nations code for the region that underlies most of the permissive tract.

Country Country(ies) in which permissive tract is located, hyphen-delimited.

Commodity Primary commodity being assessed.

Dep_type Name of the deposit type assessed.

Age Age of geologic feature assessed.

Unit Rock unit in which potash mineralization occurs.

Geology Geologic feature assessed.

Asmt_date Year assessment was conducted.

Asmt_methd Assessment method used.

Asmt_depth Maximum depth beneath the Earth’s surface used for the assessment, in kilometers.

Thickness How thickness variation was determined for the assessment.

Volume_km3 Volume of tract (in cubic kilometers) for areas of carnallite and areas of non carnallite in the format

TRRN(min,max,mode) where TRRN is SYSTAT code for triangular distribution, min = minimum value,

max = maximum value, mode = mode or average value.

Density Specific gravity used in assessment calculations.

Tonnage Tonnage of mineralized rock, in billions of tons (gigatons), in the format TRRN(min,max,mode) where

TRRN is SYSTAT code for triangular distribution; min = minimum value, max = maximum value,

mode = mode or average value.

K2O grade K2O grade (as percent K2O) for areas of carnallite and areas of non-carnallite; distribution specified in the

format ZRN(mean,s.d.) where ZRN is SYSTAT code for normal distribution and s.d. = standard deviation.

Embayments Embayments (as percent of area); distribution specified in the format TRRN(min,max,mode) where

TRRN is SYSTAT code for triangular distribution, min = minimum value, max = maximum value,

mode = mode or average value.

Anomalies Anomalies (as percent of area); distribution specified in the format TRRN(min,max,mode) where TRRN

is SYSTAT code for triangular distribution, min = minimum value, max = maximum value, mode = mode

or average value.

Other_adj Other needed adjustments.

K2O_known Known resources of potash, in billion metric tons (gigatons).

K2O_median Median of undiscovered resources of contained potash, in billion metric tons (gigatons).

K2O_mean Mean of undiscovered resources of contained potash, in billion metric tons (gigatons).

K2O_densit Mean of undiscovered resources of contained potash divided by area of permissive tract, in million metric

tons K2O per square kilometer.

Estimators Names of people on the estimation team (listed alphabetically).

Area_km2 Area of permissive tract, to three significant figures, in square kilometers.

Table 5-3. User-defined fields in the feature attribute table for Central Asia_thickness.

Field Description

LATITUDE Positive number represents latitude north of the equator.

LONGITUDE Positive number represents longitude east of the Greenwich meridian.

THICK_M Total thickness of potash-bearing intercept, in meters.

REFERENCES Short citation (author, year) for reference.

SITE_NAME Identifier for site.

SITE_TYPE Type of site (drill hole or occurrence).
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Appendixes A–H
70 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Appendix A. Summary Descriptive Model of Stratabound 

Potash-Bearing Salt Deposits

By Mark D. Cocker1 and Greta J. Orris1

1

U.S. Geological Survey, Tucson, Arizona, United States.

Introduction

Stratabound potash-bearing salt is associated with 

thick sections of evaporitic salt (halite) that form laterally 

continuous strata in marine evaporite basins. Deposits are 

extremely soluble and thus are easily altered or destroyed over 

geologic time. Stratabound potash deposits range in size from 

several tens of millions to more than 30 billion metric tons 

(Bt) of potassium oxide (K2O). Most of the world’s potash 

resources are associated with this deposit type.

Representative Deposits

Examples of stratabound potash-bearing salt deposits 

include those in the Givetian (Middle Devonian) Elk Point 

Basin in Canada, the Frasnian and Famennian (Upper 

Devonian) Pripyat Basin in Belarus, and the Lopingian (upper 

Permian) Solikamsk Basin in Russia (fig. A-1). Some larger 

basins, such as the Lopingian Zechstein Basin in Europe and 

the Central Asia Salt Basin (fig. A-1), contain potash-bearing 

salt in both stratabound and halokinetic (appendix B) forms.

Brief Description

Synonyms

Synonyms for this type of deposit include potash 

deposits, potash-bearing salt deposits, bedded potash, and 

marine potash.

Principal Commodities and Byproducts

The principal products of potash mining are potassium 

chloride (KCl), which is referred to as muriate of potash 

(MOP), and potassium sulfate (K2SO4), which is referred to 

as sulfate of potash (SOP). Where carnallite (KMgCl3•6H2O) 

constitutes a major part of a deposit, magnesium may be 

recovered. The main byproduct commodity is halite or 

rock salt. 

Relative Importance of the Deposit Type

Stratabound potash-bearing salt deposits may contain 

billions to trillions of tons of mineralized rock and are 

amenable to low-cost, bulk underground mining methods. 

Approximately 75 percent of the world’s potash production is 

from stratabound potash-bearing salt deposits, and more than 

25 percent of that production is from the Middle Devonian 

Prairie Evaporite Formation of the Elk Point Basin in 

Saskatchewan, Canada.

Global Distribution

The largest and economically most important deposits 

of potash are found in North America, Europe, and Asia. 

Newly explored deposits in Africa and South America are 

increasingly important.

Associated and Related Deposit Types

Stratabound potash-bearing salt deposits are associated 

with stratabound and bedded gypsum, anhydrite, halite, and 

sulfur deposits (Long, 1992). Halokinetic potash-bearing salt 

deposits (see appendix B, this report) originally formed in 

the same manner as stratabound deposits but deformation of 

salt resulted in grade and tonnage differences between these 

two end-member deposit types. Stratabound and halokinetic 

potash-bearing salt may occur concurrently in some 

larger basins.

Descriptive and Genetic Synopsis

Potash-bearing salt is a chemically deposited sedimentary 

rock made up of fine- to coarse-grained, potassium- and 

magnesium-chloride and sulfate minerals intergrown 

with halite. Beds of laterally continuous stratabound 

potash-bearing salt occur within thick sections 

of halite-dominant evaporite deposits. Potash-bearing 

strata range from centimeters to meters in thickness, and 

potash-bearing intervals may consist of one bed or numerous 

thin layers. These deposits are commonly attributed to 

evaporation of large volumes of seawater in hydrographically 

restricted or isolated basins under hyperarid climatic 

conditions (Warren, 2006, 2010; Kendall, 2010). Progressive 

evaporation of saline water, usually seawater, and salt 
Appendix A 71

120° E 60° E 0° 60° W 120° W

45° N

0°

45° S

1,000 2,000 0 MILES

0 1,000 2,000 3,000 4,000 KILOMETERS

EXPLANATION

Basin containing stratabound potash-bearing salt

Basin containng a mix of stratabound and  halokinetic potash-bearing salt

Political boundaries from U.S. Department of State (2009).World Eckert III Projection.Central meridian, 0°.

0 150 MILES0 300 KILOMETERS 150 75 225

75

Central Asia fig A1 gjo2

Elk Point

Permian

Neuquén

Zechstein

Pripyat

Congo

Danikil

Solikamsk

Central Asia

Figure A-1. Map showing basins containing stratabound potash-bearing salt and those containing a mix of stratabound and halokinetic potash-bearing salt from Orris and others (2014).
72 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

precipitation contribute to increasingly hypersaline conditions, 

formation of bitterns, and eventual deposition of potassiumand magnesium-bearing minerals. Multiple episodes of saline 

water inflow can result in cyclic deposition of potash minerals 

and yield deposits that are many tens of meters thick.

Permissive Tract Delineation

The fundamental geologic feature used to delineate of 

tracts permissive for stratabound potash-bearing salt is an 

evaporite- bearing sedimentary basin that contains halitedominated areas and evidence that evaporation reached the 

bittern stage. Evidence of potash mineralization includes 

reports of the presence of sylvite, carnallite, polyhalite, or 

other potassium saline minerals, or indirect evidence from 

downhole geophysical surveys.

Permissive tracts are outlined by selecting basins with 

known evaporites, restricting tract boundaries to areas likely 

underlain by salt at depths of 3 kilometers (km) or less, and if 

possible, using drill hole or other information to limit tracts 

to areas underlain by potash-bearing salt. Halite-rich layers 

are preferably many tens to hundreds of meters thick and (or) 

areally extensive.

Regional Geologic Attributes

Tectonic Setting of Basin

Stratabound potash-bearing salt is found in sedimentary 

basins that formed in regions of arid climate. Tectonic plate 

interactions formed basins between 15° and 45° north and 

south of the equator that were likely places for stratabound 

potash-bearing salt deposition. Deposits have been described 

in continental and oceanic rift basins, foreland basins, 

intracontinental sag basins, and in transform basins that are 

products of the breakup (or failed breakup) of continents, 

convergence or collision of continental plates, or intraplate 

thinning and weakening (Warren, 2010). Basin type is less 

critical than climatic conditions at the time of deposition. Hot, 

hyperarid climatic conditions are necessary to form brines 

from saline waters and deposit evaporites. These conditions 

may result from global scale atmospheric wind circulation 

patterns (Warren, 2010). Many of the world’s deserts are 

near latitudes of 30° N and 30° S, which correspond to the 

boundary between atmospheric circulation cells.

Depositional Systems

In an evaporite basin, nearshore, shallow clastic facies 

rocks grade to carbonate-, then sulfate-, then halide-rich rocks 

towards the central part of a basin or parts more distal from 

the point of seawater influx. Central parts of an evaporite 

basin may have facies representing shallow to deep water 

(Schmalz, 1969; Warren, 2006; Kendall, 2010). The resulting 

stratigraphic sequence begins with minor clastic red beds, 

followed by carbonate rocks, anhydrite or gypsum, salt, and 

ends with potash-bearing salt. Multiple episodes of evaporite 

mineral precipitation may be recorded in cyclic sequences of 

rock layers, with individual cyclic units ranging from a few 

centimeters to hundreds of meters thick.

Age Range and Age-Related Features

Potash-bearing salt deposits are found in basins that 

are Neoproterozoic in age or younger (Goncharenko, 2006; 

Kovalevych and others, 2006; Warren, 2006, 2008; Zharkov, 

1984, 2005). Half of the world’s known potash‐containing

basins are Middle and Late Devonian, Permian, or 

Paleogene-Neogene in age (Goncharenko, 2006).

Differences in deposit mineralogy likely reflect temporal 

changes in global seawater chemistry. During the Phanerozoic, 

marine brine chemistry appears to have oscillated between 

Na-K-Mg-Ca-Cl and Na-K-Mg-Cl-SO4 types (Hardie, 1990, 

1996; Holland and others, 1996; Kovalevych and others, 

1998; Horita and others, 2002; Warren, 2006; Ries, 2010). 

Magnesium sulfate- poor deposits dominated by sylvite 

and carnallite are derived from the Na-K-Mg-Ca-Cl brines. 

Magnesium-rich sulfate type deposits, with variable amounts 

of K- and Mg-sulfate minerals, may form from Na-K-MgCl-SO4

 brines. Local environmental conditions may be 

significant factors in basin brine geochemistry.

Local Geologic Attributes and Deposit 

Characteristics

Host Rocks

Host rocks are evaporitic sedimentary rocks, such as 

rock salt, sylvinite, carnallitite, kainitite, hartsalz, anhydrite, 

and gypsum. The mineralized rock strata consist of potash 

salt minerals, including chlorides, sulfates, and halite, in 

evaporite sequences.

Deposit Characteristics

Deposit Form and Dimensions

Stratabound potash-bearing salt deposits are composed of 

one or more layers or beds of potash-bearing salt. The beds or 

layers or groups of layers are commonly laterally continuous 

across large areas of a basin. Individual potash beds or layers 

range in thickness from less than a meter to several tens 

of meters, to almost a hundred meters (rare). A sequence 

of potash-bearing salt beds may range from tens of meters 

to a few hundred meters thick. The areal extent of potash 

mineralization is ultimately limited by the basin size at time of 

deposition. Typical volumes of stratabound potash-bearing salt 

can be hundreds to thousands of cubic kilometers. 
Appendix A 73

Mineralogy

Potash Ore Mineralogy

Primary potash ore minerals include sylvite, carnallite, 

kainite, polyhalite, and langbeinite (table A-1). These minerals 

occur most commonly as intergrowths with halite.

Potash Ore Assemblages

The dominant potash ore assemblages contain sylvite 

and halite with minor (<6 weight percent) carnallite or 

carnallite plus halite with negligible amounts of sylvite. Some 

deposits may contain ore assemblages of kainite, langbeinite, 

polyhalite, kieserite, and (or) bischofite mixed with halite and 

gypsum or anhydrite.

Gangue Mineralogy

Gangue minerals include halite, clay minerals, 

dolomite, anhydrite, gypsum, bischofite, epsomite, 

tachyhydrite, leonite, blödite, hexahydrite, vanthoffite, 

löweite, aphthitalite, picromerite, and borate minerals 

(table A-1). Sonnenfeld (1991) noted the presence of 

halloysites, kaolinite, iron-chlorite, magnesium-chlorites, 

montmorillonite, palygorskite, illite, sepiolite, and muscovite 

in evaporite basins.

Primary mineral zoning may consist of an outer or 

stratigraphically lower zone dominated by sulfates such as 

anhydrite or gypsum, changing to a halite-dominated zone, 

and culminating with an inner or upper zone containing 

halite plus potassium chloride or potassium sulfate minerals. 

Table A-1. Ore minerals and common accessory and gangue minerals in stratabound potash-bearing salt 

deposits from Orris and others (2014).

 [Composition formulas from Back and Mandarino (2008)]

Ore minerals Composition Other minerals Composition

Carnallite KMgCl3•6H2O Aphthitalite (K,Na)3Na(SO4)2

Kainite MgSO4•KCl•3H2O Anhydrite CaSO4

Langbeinite K2Mg2(SO4)3 Bischofite MgCl•6H2O

Polyhalite K2Ca2Mg(SO4)4•2H2O Blödite Na2Mg(SO4)2•4H2O

Sylvite KCl Boracite Mg7B7O13Cl

Dolomite CaMg(CO3)2

Epsomite MgSO4•7H2O

Gypsum CaSO4•2H2O

Halloysite Al2Si2O5(OH)4

Halite NaCl

Hexahydrite MgSO4•6H2O

Kaolinite MgSO4•H2O

Kieserite MgSO4•H2O

Kurnakovite K2Mg(SO4)2•4H2O

Leonite Na12Mg7(SO4)13•15H2O

Löweite (Na,Ca)0.3(Al,Mg)2Si4O10(OH)2•nH2O

Lüneburgite Mg3B2(PO4)2(OH)6•6H2O

Montmorillonite (Mg,Al)2Si4O10(OH) •4H2O

Palygorskite K2Mg(SO4)2•6H2O

Picromerite Mg4Si6O15(OH)2•6H2O

Sepiolite CaMgCl6•12H2O

Tachyhydrite Na6Mg(SO4)4

Vanthoffite Na6Mg(SO4)4

Volkovskite KCa4B22O32(OH)10Cl•4H2O
74 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Under certain conditions at the end of an evaporation 

sequence, some other bittern minerals such as tachyhydrite or 

bischofite may also be present and preserved. These minerals 

are highly soluble and are commonly no longer present in 

most of these deposits.

Effects of Alteration

Potash-bearing salt is highly soluble and susceptible 

to alteration, recrystallization, and dissolution by surface 

water, less saline brine, and groundwater (Warren, 2010). 

Groundwater dissolution can modify the mineralogy, 

layering, grain size, or porosity, or it can totally destroy 

a deposit. Increased pressure and temperature related to 

burial metamorphism can also lead to recrystallization and 

destruction of primary textures and changes in grain size.

Exploration Guides

Geochemical Signature(s)

In many primary deposits, brines in boreholes may 

be anomalous in potassium, sodium, magnesium, bromine, 

chlorine, and sulfur (Rogers, 2011). Exceptionally saline 

wells and saline spring water are indicative of an evaporite 

sequence, and have historically led to discoveries of concealed 

salt and potash deposits.

Bromine content of halite increases as the salinity of the 

brine increases; bromine profiles show increasing upwards 

trends in unaltered evaporite cycles. Residual brines at 

this stage may contain hundreds of parts per million (ppm) 

bromine, and on the order of a thousand parts per million 

or more bromine during precipitation of potash minerals, 

although reported values are typically much lower due to 

dilution and dissolution, diagenesis, and brine fluctuations 

(Webb and Stewart, 2011).

Geophysical Signature(s)

Radiometric Signatures

High gamma radiation signatures from the natural isotope 

potassium-40 (40K) are used to map potassium content of salt 

in downhole geophysical surveys (Garrett, 1996).

Seismic Signatures

Reflection seismic methods are used to delineate salt 

structures and layers (Fox, 1987; Simeonova and Iasky, 2005).

Other Exploration Guides

Except for drilling confirmation of potash, there are few 

sure indications of the presence of potash-bearing salt. Thick 

sections of halite, usually greater than 100 meters (m), are 

believed to be necessary prior to potash deposition (Harben 

and Kužvart, 1996), and this could be used in conjunction with 

other data to identify or rank the potash potential of basins 

with little exploration history.

Typical Grade and Tonnage

Average reported potash grades in explored deposits of 

this type may range from 5.3 to 38 percent K2O (de Ruiter, 

1979; Kumar and Bakliwal, 2005). Most reported grades in 

operating mines range from 11 to 25 percent K2O. In general, 

the lowest average grade that is currently being mined is in the 

range of 8–10 percent K2O, with the lowest associated cutoff 

grade less than 4 percent K2O.

The minimum thickness of a potash layer that is currently 

being mined is about 1 m. In Saskatchewan, minimal mining 

thicknesses range from 2.44 to 3.35 m because of the mining 

equipment used and the thickness of the highest grade ore in 

different mines (Moore and others, 2010a,b,c,d, 2011).

Reported tonnages for potash deposits range from a few 

tens of millions to 30 Bt (British Sulphur Corporation Limited, 

1984; Hardy and others, 2009). Tonnages since 2000 for 

greenfield potash projects that reported NI 43-101-compatible 

reserves and resources largely exceed 500 million metric tons, 

and commonly, 1 Bt of potash ore (Rauche and van der Klauw, 

2009, 2012; BHP Billiton, 2010; Western Potash, 2010; South 

Boulder Mines, 2012).

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Appendix B 77

Appendix B. Summary Descriptive Model of Halokinetic 

Potash-Bearing Salt Deposits

By Mark D. Cocker1 and Greta J. Orris1

1

U.S. Geological Survey, Tucson, Arizona, United States.

Introduction

Halokinetic potash-bearing salt occurs in salt structures 

developed from stratabound potash-bearing salt deposits 

where differential loading by thick overlying sediments 

initiated and drove upward movement of low-density 

potash-bearing salt. The original stratabound salt beds are 

disrupted during halokinesis, resulting in complexly deformed 

lenses and beds of potash-bearing salt. Potash deposits within 

salt structures range in size from 1 million to more than 

1,000 million metric tons. Most mined halokinetic potash 

deposits are from 50 million to several hundred million metric 

tons in size.

Representative Deposits

Some of the best known halokinetic potash-bearing 

salt deposits occur in the evaporites of the Lopingian 

(upper Permian) Zechstein Basin of Germany, Poland, The 

Netherlands, and Denmark; the Cisuralian (lower Permian) 

Pricaspian Basin of Kazakhstan and Russia; the Middle 

Pennsylvanian of the Paradox Basin in the United States; 

and the Miocene Carpathian Basin of Romania and Ukraine 

(fig. B-1). Some larger basins, such as the Zechstein Basin 

(fig. B-1) and the Central Asia Salt Basin (fig. B-1), contain 

potash-bearing salt in both halokinetic and stratabound 

(appendix A) forms.

Brief Description

Synonyms

Synonyms for this type of deposit include potash 

deposits, potash-bearing salt deposits, diapiric potash, marine 

potash, and halokinetic potash-bearing salt deposits.

Principal Commodities and Byproducts

The principal products of potash mining are potassium 

chloride (KCl), which is referred to as muriate of potash 

(MOP), and potassium sulfate (K2SO4), which is referred to 

as sulfate of potash (SOP). Where carnallite (KMgCl3•6H2O) 

constitutes a major part of a deposit, magnesium may be 

recovered. The main byproduct commodity is halite or salt.

Relative Importance of the Deposit Type

An estimated 10–15 percent of the world’s potash 

production is from halokinetic potash-bearing salt deposits.

Global Distribution

The largest known deposits are found in Europe and 

Central Asia.

Associated and Related Deposit Types

Some salt structures may contain associated gypsum, 

sulfur, iodine, bromine, or borate deposits (Raup, 1991; Long, 

1992). Salt structures and associated fault-related features 

commonly form hydrocarbon traps (Kyle and Posey, 1991; 

Long, 1992). Because stratabound potash-bearing salt deposits 

have not suffered the deformation characteristic of halokinetic 

potash-bearing salt deposits, there are important differences in 

grades and tonnages between these two end member deposit 

types. Stratabound and halokinetic potash-bearing salt may 

both be found in some larger basins.

Descriptive and Genetic Synopsis

Halokinetic potash-bearing salt deposits are the layers 

or beds of stratabound potash-bearing salt deposits that have 

moved by plastic flow into a salt structure along with the 

enclosing sedimentary rock, most of which is salt. The internal 

structure of the salt layers, and hence the potash-bearing salt 

layers, can be simple to complex, and the original continuity 

and thickness of the potash-rich layers may be altered 

considerably by the internal deformation.
78 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan 120° E 60° E 0° 60° W 120° W 45° N0° 45° S 1,000 2,000 0 MILES

0 1,000 2,000 3,000 4,000 KILOMETERS

World Eckert III Projection.Political boundaries from U.S. Department of State (2009).Central meridian, 0°.

Basin containing halokinetic potash-bearing salt

Basin containing a mix of stratabound and  halokinetic potash-bearing salt

EXPLAN

ATION

Central Asia fig B1 gjo

Paradox

Carpathian

Zechstein

Dnieper-Donets

Pricaspian

Oman

Central Asia

Sakon Nakhon and Khorat 

Figure B-1. Map showing basins containing halokinetic potash-bearing salt and those containing a mix of stratabound and halokinetic potash-bearing salt from Orris and others (2014).
Appendix B 79

Structural deformation of low-density salt may be 

related to differential loading or unloading of the sedimentary 

sequence and local or regional tectonic activity. Halokinetic 

salt structures are generally developed in tectonically active 

salt basins such as rift or foreland basins.

Permissive Tract Delineation

The fundamental unit for delineation of tracts permissive 

for potash-bearing bedded salt is an evaporite-bearing 

sedimentary basin that contains halite-dominated areas and 

evidence that evaporation reached the bittern stage. Evidence 

of potash mineralization includes reports of the presence of 

sylvite, carnallite, polyhalite, other potassium saline minerals 

or indirect evidence from downhole geophysical surveys.

Permissive tracts for halokinetic potash-bearing salt 

deposits are outlined by (1) selecting basins with known 

halokinetic salt; (2) restricting tract boundaries to areas likely 

underlain by halokinetic salt at depths of 3 kilometers (km) 

or less; (3) if possible, using drill hole or other information 

to limit tracts to areas underlain by potash-bearing salt; 

and (4) delineating specific salt structures likely to contain 

potash-bearing salt.

Regional Geologic Attributes

Halokinesis is most common in continental and oceanic 

rift basins, foreland basins, convergent basins, and transform 

basins where lateral compression or extension is active. 

Halokinesis may be initiated by such factors as (1) differential 

loading through rapid deposition of thick, overlying clastic 

sediments; (2) differential unloading resulting from listric 

block faulting during extensional rifting; (3) differential 

erosion of overlying sedimentary rocks; (4) rift basement 

block faulting; and (5) compressional or extensional regional 

tectonic activity (Kityk, 1970; Amor, 1999; Al-Zoubi and ten 

Brink, 2001; Jarhani and others, 2007).

Depositional Systems

In an evaporite basin, near-shore, shallow clastic facies 

rocks grade to carbonate-, then sulfate-, then halide-rich rocks 

towards the deep, central parts of a basin. Central parts of 

an evaporite basin may have facies representing shallow to 

deep water (Schmalz, 1969; Warren, 2006; Kendall, 2010). 

The resulting stratigraphic sequence begins with minor clastic 

red beds, followed by carbonate rocks, anhydrite or gypsum, 

salt, and ends with potash-bearing salt. Multiple episodes 

of evaporite mineral precipitation may be recorded in cyclic 

sequences of rock layers, with individual cyclic units ranging 

in thickness from a few centimeters to hundreds of meters. 

During halokinesis, the original depositional layering is partly 

to wholly disrupted by plastic flow, which may result in 

complex folding, discontinuous mineralization, or even loss 

of mineralization.

Age Range and Age-Related Features

Potash-bearing salt deposits are found in basins that 

are Neoproterozoic in age or younger (Zharkov, 1984, 

2005; Goncharenko, 2006; Kovalevych and others, 2006; 

Warren, 2006, 2008). Half the world’s known potashcontaining basins are Middle and Late Devonian, Permian, or 

Paleogene-Neogene in age (Goncharenko, 2006).

Differences in deposit mineralogy likely reflect temporal 

changes in global seawater chemistry. During the Phanerozoic, 

marine brine chemistry oscillated between Na-K-Mg-Ca-Cl 

and Na-K-Mg-Cl-SO4 types (Hardie, 1990, 1996; Holland 

and others, 1996; Kovalevych and others, 1998; Horita 

and others, 2002; Warren, 2006; Ries, 2010). Magnesium 

sulfate- poor deposits dominated by sylvite and carnallite are 

derived from Na-K-Mg-Ca-Cl brines. Magnesium-rich sulfate 

type deposits, with variable amounts of K- and Mg-sulfate 

minerals, may form from Na-K-Mg-Cl-SO4 brines. Local 

environmental conditions may be a significant factor in basin 

brine geochemistry.

Local Geologic Attributes and Deposit 

Characteristics

Host Rocks

Host rocks are evaporitic sedimentary rocks, such as rock 

salt, sylvinite, carnallitite, kainitite, hartsalz, anhydrite, and 

gypsum. Diapiric structures pierce overlying sediments, so any 

younger, originally overlying sedimentary rocks may appear to 

host salt and potash mineralization.

Impacts of Local Structures

Halokinetic salt structures are commonly aligned over 

basement faults.

Deposit Characteristics

Deposit Form and Dimensions

The areal extent of salt diapirs ranges from a few 

to several hundred square kilometers. With a vertical 

extent ranging from a few hundred meters to more than 

10 kilometers, salt volumes of diapirs are on the order of tens 

to hundreds of cubic kilometers. Potash forms only a small 

part of an individual salt diapir.

Mineralogy

Potash Ore Mineralogy

Primary ore minerals include sylvite, carnallite, kainite, 

polyhalite, and langbeinite (table B-1). These minerals occur 

most commonly as intergrowths with halite.
80 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Potash Ore Assemblages

The dominant ore assemblages contain sylvite and halite 

with minor (<6 weight percent) carnallite or carnallite plus 

halite and negligible amounts of sylvite. Some deposits may 

contain ore assemblages of kainite, langbeinite, polyhalite, 

kieserite and (or) bischofite mixed with halite and gypsum or 

anhydrite.

Gangue Mineralogy

Gangue minerals include halite, clay minerals, dolomite, 

anhydrite, gypsum, bischofite, epsomite, tachyhydrite, 

leonite, blödite, hexahydrite, vanthoffite, löweite, aphthitalite, 

picromerite, and borate minerals (table B-1). Sonnenfeld 

(1991) noted the presence of halloysites, kaolinite, ironchlorite, magnesium-chlorites, montmorillonite, palygorskite, 

illite, sepiolite, and muscovite in evaporite basins.

Primary mineral zoning may consist of (1) an outer or 

stratigraphically lower zone dominated by sulfates such as 

anhydrite or gypsum, changing to (2) a halite-dominated zone, 

and culminating with (3) an inner or upper zone containing 

halite plus potassium chloride or potassium sulfate minerals. 

Under certain conditions at the end of an evaporation 

sequence, some other bittern minerals, such as tachyhydrite or 

bischofite, may also be present and preserved. These minerals 

are highly soluble and are commonly no longer present in 

most of these deposits.

Mineral Zoning

Secondary zoning caused by alteration may be 

pronounced along the flanks and apexes of salt structures.

Table B-1. Ore minerals and common accessory and gangue minerals in halokinetic potash-bearing salt deposits 

from Orris and others (2014).

[Composition formulas from Back and Mandarino (2008)]

Ore minerals Composition Other minerals Composition

Carnallite KMgCl3•6H2O Aphthitalite (K,Na)3Na(SO4)2

Kainite MgSO4•KCl•3H2O Anhydrite CaSO4

Langbeinite K2Mg2(SO4)

3 Bischofite MgCl•6H2

O

Polyhalite K2Ca2Mg(SO4)4•2H2O Blödite Na2Mg(SO4)2•4H2O

Sylvite KCl Boracite Mg7B7O13Cl

Dolomite CaMg(CO3)

2

Epsomite MgSO4•7H2O

Gypsum CaSO4•2H2O

Halloysite Al2Si2O5(OH)4

Halite NaCl

Hexahydrite MgSO4•6H2O

Hydroboracite CaMgB6O8(OH)6•3H2O

Inderite Al2Si2O5(OH)4

Kaolinite MgSO4•H2O

Kieserite MgSO4•H2O

Kurnakovite K2Mg(SO4)2•4H2O

Leonite Na12Mg7(SO4)13•15H2O

Löweite (Na,Ca)0.3(Al,Mg)2Si4O10(OH)2•nH2O

Lüneburgite Mg3B2(PO4)2(OH)6•6H2O

Montmorillonite (Mg,Al)2Si4O10(OH)•4H2O

Palygorskite K2Mg(SO4)2•6H2O

Picromerite Mg4Si6O15(OH)2•6H2O

Sepiolite CaMgCl6•12H2O

Tachyhydrite Na6Mg(SO4)4

Vanthoffite Na6Mg(SO4)4

Volkovskite KCa4B22O32(OH)10Cl•4H2O
Appendix B 81

Ore Controls

Ore controls peculiar to potash-bearing halokinetic salt 

structures include (1) zones of primary and secondary potash 

mineralization, (2) internal structure of the salt structures that 

affects thickness and location of the potash beds, and (3) depth 

to the potash ore. Halokinesis may move potash-bearing salt 

to shallower depths, where the potash is more amenable to 

discovery and mining.

Effects of Alteration

As they rise to the surface, halokinetic potash-bearing 

salt structures interact with less saline brine and groundwater. 

Surface and groundwater may partially dissolve carnallite, 

removing magnesium chloride and leaving potassium chloride 

to form sylvite. In the upper part of a salt structure, dissolution 

of salt minerals leaves insoluble materials such as gypsum, 

anhydrite, and clay that form a caprock that may be may be on 

the order of tens to a thousand meters thick (Warren, 2006).

Halokinesis can bring potash-bearing salt to the Earth’s 

surface or close to it, exposing the salt to surface weathering. 

In areas of extreme aridity, such as the Middle East, surface 

weathering is minimal and salt and potash-bearing salt can 

exist on the surface.

Exploration Guides

Geochemical Signature(s)

Primary indicator elements of potash mineralization 

in rocks and groundwater include potassium, sodium, 

magnesium, bromine, chlorine, and sulfur as sulfate (Rogers, 

2011). Exceptionally saline wells and saline spring water 

may be indicative of an evaporite sequence at depth, and 

have historically led to discoveries of concealed salt and 

potash deposits.

Geophysical Signature(s)

Seismic, gravity, and downhole gamma radiation surveys 

may be useful in the delineation of potash-bearing salt. The 

velocity contrast between salt and most other sedimentary 

rocks is sufficient that reflection seismic methods are used 

extensively to delineate salt structures and beds (Ratcliff and 

others, 1992; Ezersky, 2005). Salt is less dense than most 

enclosing sediments, so gravity surveys work well to identify 

and define salt structures (Nettleton, 1968; Benassi and others, 

2006). High gamma radiation from the natural isotope 40K 

provides a measure of the potassium content of salt in drillhole logs (Garrett, 1996). In underground mines, ground 

penetrating radar may be used to define the structure of the salt 

diapir (Behlau and Mingerzahn, 2001; Kovin, 2011).

Geomorphic and Physiographic Features

Near-surface diapirs may be expressed as domal or 

collapse structures that are roughly circular topographic highs 

or lows. Lakes may form at the crest of near-surface salt 

structures owing to dissolution of the underlying evaporites.

Other Exploration Guides

The most readily detectable features of concealed salt 

structures that may contain potash include saline wells and 

springs. Except for drilling confirmation of potash, there 

are few sure indications of the presence of potash-bearing 

salt. Thick sections of halite, usually greater than 100 m, 

are believed to be necessary prior to potash deposition 

(Harben and Kužvart, 1996), and this feature could be used 

in conjunction with other data to identify or rank the potash 

potential of basins with little exploration history.

Typical Grade and Tonnage

Tonnages of these deposits are smaller on average 

than stratabound potash-bearing salt deposits. However, 

some of the deposits have reported resources of as much as 

6–10 billion metric tons in some unusually large and complex 

salt structures. Grades are highly variable, but commonly 

average less than 20 percent K2O.

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O.Y., and Zhukova, S.A., 2006, Chemical composition of 

seawater in Neoproterozoic—Results of fluid inclusion 

study of halite from Salt Range (Pakistan) and Amadeus 

Basin (Australia): Precambrian Research, v. 144, p. 39–51.

Kovalevych, V.M., Peryt, T.M., and Petrychenko, O.Y., 

1998, Secular variation in seawater chemistry during the 

Phanerozoic as indicated by brine inclusions in halite: 

Journal of Geology, v. 106, p. 695–712.

Kovin, O., 2011, Mapping of evaporite deformation in a 

potash mine using ground penetration radar—Upper Kama 

deposit, Russia: Journal of Applied Geophysics, v. 74, 

p. 131–141.

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development, and salt dome mineral resources, in Melvin, 

J.L., ed., Evaporites, petroleum and mineral resources: New 

York, Elsevier, p. 413–474.

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and contained-sulfur model for salt-dome sulfur: U.S. 

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available at http://pubs.er.usgs.gov/publication/ofr92705.]

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northern Spain, in Mattox, R.B., Holser, W.T., Odé, H., 

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D.C., eds., Saline deposits: Geological Society of America 

Special Paper 88, p. 75–82.

Orris, G.J., Cocker, M.D., Dunlap, P., Wynn, J.C., Spanski, 

G.T., Briggs, D.A., and Gass, L., with contributions from 

Bliss, J.D., Bolm, K.S., Yang, C., Lipin, B.R., Ludington, 

S., Miller, R.J., and Slowakiewicz, M., 2014, Potash—A 

global overview of evaporite-related potash resources, 

including spatial databases of deposits, occurrences, 

and permissive tracts: U.S. Geological Survey Scientific 

Investigations Report 2010–5090–S, 76 p., and spatial data, 

http://dx.doi.org/10.3133/sir20105090S.

Ratcliff, D.W., Gray, S.H., and Whitmore, N.D., Jr., 1992, 

Seismic imaging of salt structures in the Gulf of Mexico: 

The Leading Edge, v. 11, p. 15–31.

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subtype—Diapiric salt structures, in Orris, G.J., and Bliss, 

J.D., Some industrial mineral deposit models—Descriptive 

deposit models: U.S. Geological Survey Open-File Report 

91–11A, 73 p.

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evidence for secular variation in seawater Mg/Ca (calcitearagonite seas) and its effect on marine biological 

calcification: Biogeosciences, v. 7, p. 2795–2849.

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models: Saskatchewan Ministry of Energy and Resources 

Open File Report 2011–57, 112 p.
Appendix B 83

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of the Geographer and Global Issues.

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hydrocarbons: Berlin, Springer-Verlag, 1,035 p.

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Littke, Ralf, Bayer, Ulf, and Gajewski, Dirk, eds., Dynamics 

of Complex Intracontinental Basins: Berlin, SpringerVerlag, p. 249–276.

Zharkov, M.A., 1984, Paleozoic salt bearing formations of the 

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Zharkov, M.A., 2005, Evolyutsiya evaporitov v dokembrii 

v svyazi s preobrazovaniyami biosfery i khimicheskogo 

sostava mirovogo okeana; Stat’ya 1, Evapority arkheya i 

rannego proterozoya [Evolution of Precambrian evaporites, 

transformation of biosphere and the world oceans’ chemical 

composition—Paper 1, Archean and Paleoproterozoic 

evaporites]: Stratigrafiya, Geologicheskaya Korrelyatsiya, 

v. 13, no. 2, p. 19–29.
84 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Appendix C. Adaptive Geometric Estimation for Stratabound 

Potash-Bearing Salt Deposits—Summary

By Greta J. Orris,1 James D. Bliss,1 Pamela Dunlap,1 and Mark D. Cocker1

1

U.S. Geological Survey, Tucson, Arizona, United States.

This summary describes a geometric estimation approach 

for assessment of areally extensive bedded or stratiform 

mineral deposits and the use of this approach to estimate 

undiscovered potash in stratabound potash-bearing salt 

deposits. This methodology is adaptable to varied types of data 

inputs and the resulting estimate is in a format compatible with 

results from the U.S. Geological Survey (USGS) three-part 

form of assessment (Singer and Menzie, 2010).

Requirements for Methodology 

An assessment methodology for stratabound deposits 

must meet several criteria:

• The process must produce a probabilistic estimate of 

undiscovered resources as a distribution of expected 

grades and tonnages of the contained mineral 

or commodity (for example, K2O for potash). A 

probabilistic distribution is compatible with outputs 

from areas assessed using the traditional USGS 

three-part form of assessment (Singer and Menzie, 

2010) and indicates not only the best estimate, but 

also the uncertainty of the estimate. A single number 

conveys a level of certainty unlikely to be achievable 

in this type of exercise.

• The methodology must be appropriate for a stratabound 

deposit type; it should be based on volume (area 

multiplied by thickness) with appropriate adjustments 

for unmineralized areas, uncertainties and variability in 

input, and other factors that affect the estimate of the 

amount of mineralization.

• The methodology must be adaptable to large variations 

in basin size and to highly variable input data volumes, 

formats, and densities across a tract.

• The output must be adjustable for known reserves and 

resources.

• The methodology needs to be easily implemented with 

readily available hardware and software, as well as be 

adaptable to new and (or) different software, hardware, 

and estimation techniques.

These requirements led to development of a methodology 

that can be adapted to highly variable inputs on a basinby-basin basis, yet still provides a common underlying 

approach and results in a format that allows for comparison 

between areas.

General Approach

A simplified description of ore reserve estimates that 

meet the Canadian Securities Administrators National 

Instrument 43-101 report standards for potash (Canadian 

Institute of Mining, Metallurgy and Petroleum, 2003), 

starts with a volume estimate of mineralized material that 

is converted to ore tonnage using an appropriate density 

(table C-1). The estimated ore tonnage is then adjusted for 

unmineralized areas contained within the area estimated. 

An overview of mineral reserve and resource estimation 

standards for these reports, as well as some potash specific 

guidelines, are available from the Canadian Institute of 

Mining, Metallurgy and Petroleum (2003, 2004). The adaptive 

geometric estimation (AGE) methodology takes a similar 

approach to estimating undiscovered resources with the 

less robust data inputs to be expected from poorly-explored 

areas and with an additional correction for known reserves 

and resources. 

Table C-1. Densities used in calculating tonnage.

[g/cm3, grams per cubic centimeter]

Formula Density

(g/cm3)

Carnallite KMgCl3•6H2O 1.6

Halite NaCl 2.17

Sylvite KCl 1.99

Elk Point sylvinite 2
Appendix C 85

Overall, the approach can be most simply stated as:

T = (VOL × DENS) – NOMIN – RR,

where

T = “undiscovered” in-place tonnage,

VOL = volume,

DENS = density of ore, 

NOMIN = correction for unmineralized areas, and

RR = known reserves and resources.

It follows that the tonnage of the commodity of interest, 

potash (K2O), is 

KT = T × GRD,

where

KT = tonnage of contained potash as K2O, and 

GRD = potash grade as percent K2O.

Adaption of Reserves Estimation to 

Undiscovered Resources Estimation

The AGE methodology for assessing stratabound potash 

deposits consists of several steps. First, the tract area for 

potash is identified and delineated using geologic maps, 

deposit models, and other data. Second, the volume of this 

area is calculated using known and (or) estimated thickness 

data. Third, a potash grade is selected from an appropriate 

grade distribution model. If the dominant ore mineral is 

not known, then an assumption is made about the probable 

ore mineral based on the selected grade. The grade and ore 

mineral are used to determine an appropriate density to 

convert the volume estimate to an in-place tonnage for the 

delineated area. Fourth, the tonnage estimate is adjusted for 

unmineralized areas within the tract (anomalies) and along 

its edges (embayments) and for known mineralization, as 

appropriate. Finally, the contained potash in the ore (as metric 

tons of K2O) is determined from the tonnage and grade. 

The process is repeated for 5,000 iterations to produce a 

probabilistic estimate of contained potash. A flow chart of this 

process is shown in figure C-1.

Although this approach is conceptually simple, 

implementation in areas with undiscovered resources is 

complicated by incomplete data. The extent of mineralization, 

in terms of area and thickness, is usually not well-defined and 

reported grade, density, and similar data may not represent 

the entire assessment area. It is inevitable in areas with 

undiscovered resources that one or more data inputs will be 

unknown and must be estimated. These estimates can be based 

on analogy with similar, better explored areas, or models 

can be constructed based on incomplete data from the area 

being studied.

This is a largely stochastic approach that requires 

simplifying assumptions along with estimates of missing data. 

Most estimates of missing data are not single numbers, but 

are distributions of possible values. These distributions are 

randomly sampled using Monte Carlo simulation(s) in the 

AGE methodology. For potash, 5,000 iterations were typically 

used. This process produces stable or repeatable distributions 

of estimated undiscovered ore and the contained commodity, 

with the medians of those distributions representing the most 

likely values.

 Implementation of this methodology for the potash 

assessment requires a geographic information system (GIS) 

or other system to calculate areas and volumes, as well as 

statistical and modeling software. For this study, ArcGIS was 

used to map data and estimate volumes. Data distributions 

were constructed and (or) tested using JMP 8 data analysis 

software. More complex statistical procedures, simulations 

and estimations were programmed and executed using 

SYSTAT 12 software (appendix F). Individual steps and some 

of the alternate estimation procedures are discussed more 

completely in the following sections.

Tract Delineation and Volume

The first step in an assessment process is to delineate 

a tract, the area containing the mineralization of interest. 

Tract delineation is commonly done using a mix of 

geologic and other maps, geophysical data, and point data, 

such as drill holes and mineral occurrences. In addition, 

tract delineation may be constrained by criteria such as 

minimum thickness, grade, or maximum levels of deleterious 

materials or contaminants. At an assessment scale of 

1:1,000,000, uncertainties in potash tract boundaries, caused 

by lack of detail in source materials used to delineate the 

mineralized areas, can be significant and assessors should 

account for this in their estimates. An Albers Equal Area or 

other equal area projection of the tract boundaries should be 

used for accurate area and volume calculations.

In well-explored areas, thickness values can be extracted 

from drill-hole data and the information contoured. In 

less-explored areas, thickness data might be a mix of drill-hole 

and other point data on thickness. For these latter cases, a 

single volume can be calculated using a continuous raster 

surface of the total potash thickness and the lateral tract 

boundaries. Most tracts have multiple sources for thickness 

estimates, including drill-hole and isopach data, and these data 

are commonly unevenly distributed. In these tracts, thickness 

isopachs can be constructed for the entire tract using the 

available data and informed judgment. Volumes can then be 

calculated using the isopachs.

In some areas, thickness data are not available as either 

point data or isopachs to allow calculation of volume. In these 

areas, an “average” thickness can be estimated and used. 
86 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan For 5,000 iterations

Delineate tract

GIS Statistical software

Distributions:

(1) tons contained mineral

(2) tons total ore

End iterations

Does iteration = 5,000?

YES

NO

Predicted contained mineral tonnage to file

Predicted total ore tonnage to file

Select grade from grade distribution

Volume(s) from GIS

Select anomaly and embayment adjustments

Determine probable dominant mineral 

and density based on grade 1 2 3

4 5 6

7 8 9

C 0 E

Calculate tonnage adjustment

(anomalies and embayments) 1 2 3

4 5 6

7 8 9

C 0 E

Calculate ore tonnage and 

adjusted ore tonnage 1 2 3

4 5 6

7 8 9

C 0 E

Calculate adjusted contained K2O tonnage

1 2 3

4 5 6

7 8 9

C 0 E

Subtract known reserves and resources

from adjusted ore and adjusted contained 

K2 1 2 3 O tonnages

4 5 6

7 8 9

C 0 E

CAsia Fig C-1 gjo

Figure C-1. Flow chart showing generalized approach for assessing stratabound industrial 

mineral deposits.
Appendix C 87

If possible, a maximum, minimum, and mode estimate of 

thickness should be made. These values allow construction 

of a triangular distribution (Kotz and van Dorp, 2004). Use 

of triangular distributions is not an optimal choice because 

the tails of the distribution tend to be overestimated and the 

relationship between the maximum and minimum values and 

the mode are assumed to be linear (fig. C-2). However, the 

triangular distribution is widely used in risk assessment and 

other areas where the underlying distribution is not known, 

and this distribution is commonly available in statistical 

software packages. The advantage of this distribution is that 

most scientists understand what the input values mean and 

can estimate these values consistently when provided with a 

given level of geologic information. However, the use of the 

triangular distribution is not considered to be as statistically 

rigorous by some statisticians as other distributions. In the 

case of potash thickness, we do not know the underlying 

distribution (normal, lognormal, exponential, or other) 

and published studies for thickness distributions for other 

lithologies are not in agreement. Therefore, use of the 

triangular distribution is often the best available option.

In assessment of undiscovered potash resources, the 

exact method of calculating the volumes is not considered to 

be a significant issue compared to other uncertainties, and the 

assessor should use the tools available. Testing of calculated 

differences in volumes, such as comparing the outcomes of 

krigging and nearest neighbor in this study, showed maximum 

differences of 3–11 percent where the data points were 

unevenly distributed and data point density was low. In most 

calculations, the potential error from incomplete, missing, and 

widely and unevenly spaced data is significantly larger than 

differences arising from the volume calculation technique.

200 250 300 350 400 450 500

0.10

0.08

0.05

0.03

Probability

Unspecified variable in unspecified units

Figure C-2. Graph showing example of a triangular 

distribution of an unspecified variable with a mode value of 

300, a maximum of 500, and a minimum of 200.

Grade and Density

For most potash tracts, grade was modeled using 

available grade data for thickness intervals of 1 m or greater. 

Grades of rock-forming commodities such as potash are 

normally distributed (as opposed to the lognormal distribution 

of commodities such as Cu, Au, Pb, and so on; see Harris, 

1984). Grade models were constructed by USGS staff from 

published potash horizon thicknesses and grades taken 

from well log data. Grades and thicknesses determined 

by the USGS from well logs met the following criteria: 

(1) contiguous extent of potash and halite mineralization 

with minimum thickness of 1 meter and no maximum 

thickness; (2) average grade within selected thickness greater 

than 4 percent K2O equivalent; and (3) potash horizons 

divided by “unmineralized” halite. Note that “unmineralized” 

halite consists of (1) halite horizons that were not sampled 

and analyzed by drillers because of assumed low grade, 

(2) 1 meter or more of halite that would drop potash grade 

below the minimum grade if included in the potash horizon, 

and (3) halite outside of geophysically-determined potash 

horizons. Most of the grade models constructed for potash 

tracts are distributed normally if n>30, where n is the number 

of data points. For very small datasets, the mean of the 

documented data and other information was used to create a 

normal distribution of K2O grade. For tracts with little data 

where correlation between potash horizons in different parts 

of the tract could not be determined and for tracts where 

reported data consisted of the aggregate thickness of all potash 

horizons and the average grade across all the horizons, potash 

resources were estimated as total potash without consideration 

of intervening halite.
88 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

To convert estimated volume(s) of potash mineralization 

to tonnage(s) requires a known or estimated density. In 

some areas, such as Saskatchewan, many companies use a 

standard average density for conversion for sylvite ore based 

on knowledge or assumptions about the ore composition. 

For most potash tracts evaluated by the USGS, we estimate 

density based on grade distributions constructed for each 

tract and modeled sylvinite or carnallitite grade and density 

relationships (see appendix F). Data released by Rauche and 

others (2013) allowed relationships between carnallite and 

sylvinite grades and measured density to be modeled using 

linear regression. A Monte Carlo simulation was used to 

sample the grade distribution and that grade was substituted 

in one of the following formulas based on regression of the 

Rauche and others Congo data to determine the density:

• Sylvinite—density = 2.177–0.003×grade, or

• Carnallite—density = 2.044 – 0.027×grade.

These formulas are considered appropriate because the 

mean of the density response for sylvinite in that regression 

is 2.08, a common average density used for sylvinite ore 

tonnage calculations in Saskatchewan. Also, the carnallitite 

grade and density relationship provides densities similar to 

a scattered handful of carnallitite grade and density reports. 

Although region-specific relationships would be preferred if 

the data were available, grade and measured density are rarely 

reported together.

A major simplifying assumption is made in the absence 

of specific data on the type of potash mineralization. The 

resource is considered to be a mix of the potash mineral 

carnallite and halite (carnallitite) if the selected grade in 

an iteration is less than 16.9 percent K2O (the maximum 

K2O content of carnallite). For grades of 16.9 percent K2O 

or greater, the ore is considered to be a mix of sylvite and 

halite (sylvinite).

Tonnage and Adjustments to Tonnage

Once density is determined, in-place ore tonnage can be 

calculated by multiplying ore volume by density. Estimators 

need to ensure that the volume units and density units 

are compatible.

There may be large unmineralized areas within the tract 

boundaries. For potash, these areas may result from nondeposition, dissolution, erosion, remineralization, or other 

factors that significantly decrease the size of the potential 

resource. Therefore, once a gross tonnage is determined for the 

potash mineralized area, the tonnage needs to be adjusted for 

what the potash assessment team has classified as anomalies 

and embayments (fig. C-3), as well as known reserves 

and resources.

Anomalies are defined as any barren areas inside the tract 

other than rocks that are too old to host mineralization and that 

should be excluded from the tract during the initial delineation 

process. Anomalies include depletion zones, replacement 

zones, and halite zones, washout and leach or “salt horst” 

anomalies, or salt dissolution and collapse anomalies (Baar, 

1974; Korenevskiy, 1989; Boys, 1990; Filippov, 1990; 

Kopnin, 1995; Abbott and Kuchling, 2009). Anomalies are 

interruptions in the normal continuity of potash-bearing beds 

and may range in size from less than a meter to tens of square 

kilometers or larger. The lack of potash mineralization may 

result from dissolution, non-deposition, erosion, or another 

cause; halite is typically encountered in these areas rather 

than potash. Anomalies may occupy as much as 40 percent or 

more of the mineralized area (Linn and Adams, 1966; Boys, 

1990) or as little as 5 percent (Kopnin, 1995). The reported 

average seems to be in the range of 20 to 25 percent (Halabura 

and Hardy, 2007; Hardy and others, 2009). For most tracts, 

this variable needs to be estimated, and there is commonly at 

least some information specific to each tract on which to base 

the estimate.

Embayments are a correction for actual edge irregularities 

in the mineralization not represented in the tract boundaries. 

These irregularities may be in part caused by dissolution, but 

largely result from non-deposition because of topography, 

facies change, water or sediment incursion from the basin 

edges, or mechanical weathering. This correction is added 

because the effect on volume and tonnage may be large; it is 

determined and estimated where appropriate on a tract-by-tract 

basis and considers how the tract boundary was delineated 

and the scale of the most detailed information. Potash-bearing 

tracts may show effects of just anomalies or just embayments, 

but at common assessment scales such as 1:1,000,000, effects 

of both need to be considered. In places, the cumulative area 

of potash loss due to embayments and anomalies may be a 

significant percentage of the overall potash mineralized area 

and leads to a “Swiss cheese” pattern of potash distribution, 

such as in the Krasnyi IIIB horizon of the Permian Solikamsk 

deposit, Russia (fig. C-3; Zharkov, 1984).

The last adjustment to tonnage is to subtract known 

reserves and resources. For the potash assessment, this 

includes all proven, measured, recoverable, indicated, and 

inferred reserves and resources, as well as those classified as 

A, B, C1, and C2 under the Russian resource/reserve reporting 

system (Henley, 2004). All known reserve and resource figures 

are converted to in-place ore and contained potash (as K2O) 

before being subtracted from the estimate.

Constructing a Probabilistic Distribution

The process outlined above is repeated for 

5,000 iterations to create a probabilistic distribution of 

estimates of contained potash. This was done using the Monte 

Carlo simulation function of the SYSTAT 12 software and 

tract-specific tracts.
Appendix C 89

Kama River

Solikamsk

Berezniki

Kama River

56°30' E 57° E

59° N

60° N

59°30' N

embayment

embayment

embayment

embayment

anomalies

anomalies

anomalies

embayment

embayment

embayment

embayment

embayment

Area of map

50° E 60° E 70° E

65° N

60° N

55° N

RUSSIA

KAZAKHSTAN

Perm

Tyumen

Chelyabinsk

Ufa

Kazan

Vyatka

Syktyvkar

Tobol River

Ob River

Kama River

Pecho ra R.

Vo lga River

Ural River

0

0

5

5

10

10 MILES

15 20 KILOMETERS Political boundaries from U.S. Department of State (2009).

Albers Equal Area Projection.

Central meridian, 114° E., latitude of origin, 30° N.

EXPLANATION

Krasnyi IIIB horizon

Total extent of all potash layers

Cisuralian

CAsia Fig. C-3 gjo2

Figure C-3. Map showing anomalies and 

embayments of the Krasnyi IIIB horizon 

relative to the maximum extent of potash 

as determined by all potash horizons, 

Solikamsk, Russia (adapted from Zharkov, 

1984). Many, but not all, anomalies and 

embayments are labeled.
90 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Summary

The AGE methodology produces a distribution of 

in-place ore tonnage and contained K2O tonnage for the 

assessed potash tracts. This approach also provides an 

estimation of the uncertainty in the assessment. Input 

variables for estimates that form distributions are sampled 

using successive Monte Carlo simulations; for most 

tracts, 5,000 iterations were performed to produce stable 

distributions of estimated ore and contained K2O tonnages. 

The most probable ore tonnage and contained K2O estimates 

are centered near the mean; the values in the tails of these 

distributions are considered unlikely but help quantify 

the uncertainty.

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Publishing Company, 308 p.

Linn, K.O., and Adams, S.S., 1966, Barren halite zones in 

potash deposits, Carlsbad, New Mexico, in Rau, J.L., ed., 

Second symposium on salt: Cleveland, Ohio, The Northern 

Ohio Geological Society, Inc., p. 59–69.

Rauche, Henry, van der Klauw, Sebastiaan, and Linsenbarth, 

Ralf, 2013, Summary of the Feasibility Study for a Solution 

Mine on the ALLANA Potash Project, Danakhil Depression, 

Afar State, Ethiopia: Technical Report NI 43-101, 

February 4, 2013 news release, Allana Potash Corp., 

accessed August 21, 2015, at http://www.allanapotash.com/

news/2013/index.php?&content_id=33.

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

resource assessment—An integrated approach: New York, 

Oxford University Press, 219 p.

Zharkov, M.A., 1984, Paleozoic salt bearing formations of the 

world: New York, Springer-Verlag, 427 p.
Appendix D 91

Appendix D. Grade Data for Gissar and Amu Darya Tracts

By Greta J. Orris,1 Mark D. Cocker,1 and Jeff Wynn2

1

U.S. Geological Survey, Tucson, Arizona, United States.

2

U.S. Geological Survey, Vancouver, Washington, United States.

Table D-1. Grade data for the Central Asia Salt Basin.

[U., upper; Mid., middle; %, percent; m, meter; —, no data]

Well or site Orebody

or layer

K2O

(%)

Thickness

(m) Reference

2 Lower II 17.79 2 Petrov and Chistakov (1964)

5 Lower II 13.6 3.5 Petrov and Chistakov (1964)

6 Lower II 20.44 1.5 Petrov and Chistakov (1964)

7 Lower II 16.49 1.5 Petrov and Chistakov (1964)

8 Lower II 19.53 5.03 Petrov and Chistakov (1964)

11 Lower II 11.62 1.5 Petrov and Chistakov (1964)

14 Lower II 26.61 1.5 Petrov and Chistakov (1964)

15 Lower II 26.09 2 Petrov and Chistakov (1964)

17 Lower II 16.13 1.5 Petrov and Chistakov (1964)

18 Lower II 16.09 2 Petrov and Chistakov (1964)

26 Lower II 15.17 2.5 Petrov and Chistakov (1964)

35 Lower II 17.24 1.5 Petrov and Chistakov (1964)

36 Lower II 17.77 4.5 Petrov and Chistakov (1964)

44 Lower II 16.84 2 Petrov and Chistakov (1964)

45 Lower II 18.45 8 Petrov and Chistakov (1964)

46 Lower II 10.39 2.5 Petrov and Chistakov (1964)

47 Lower II 9.64 1 Petrov and Chistakov (1964)

49 Lower II 20.72 3 Petrov and Chistakov (1964)

51 Lower II 14.38 3.5 Petrov and Chistakov (1964)

54 Lower II 15.41 1.5 Petrov and Chistakov (1964)

55 Lower II 13.01 1.2 Petrov and Chistakov (1964)

1 Lower II 12.3 1.55 Petrov and Chistakov (1964)

2 Lower II 19.28 6 Petrov and Chistakov (1964)

3 Lower II 23.96 4.4 Petrov and Chistakov (1964)

46 Lower II 18.05 1.5 Petrov and Chistakov (1964)

47 Lower II 10.84 1 Petrov and Chistakov (1964)

48 Lower II 18.06 1.5 Petrov and Chistakov (1964)

50 Lower II 17.43 1.5 Petrov and Chistakov (1964)

51 Lower II 19.33 2 Petrov and Chistakov (1964)

1 Blue 17.17 3.15 Petrov and Chistakov (1964)

5 Blue 18.79 2 Petrov and Chistakov (1964)

6 Blue 14.6 1.5 Petrov and Chistakov (1964)

7 Blue 16.23 3 Petrov and Chistakov (1964)

11 Blue 19.81 2.2 Petrov and Chistakov (1964)

14 Blue 23.41 4 Petrov and Chistakov (1964)
92 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Well or site Orebody

or layer

K2O

(%)

Thickness

(m) Reference

15 Blue 19.61 3.72 Petrov and Chistakov (1964)

16 Blue 7.95 1.5 Petrov and Chistakov (1964)

19 Blue 13.85 2.5 Petrov and Chistakov (1964)

20 Blue 13.01 1.5 Petrov and Chistakov (1964)

21 Blue 21.89 1.6 Petrov and Chistakov (1964)

22 Blue 12.63 2.5 Petrov and Chistakov (1964)

23 Blue 14.98 2.5 Petrov and Chistakov (1964)

24 Blue 16.48 3.5 Petrov and Chistakov (1964)

25 Blue 15.35 3.59 Petrov and Chistakov (1964)

26 Blue 14.24 5.5 Petrov and Chistakov (1964)

28 Blue 23.71 2.5 Petrov and Chistakov (1964)

29 Blue 14.24 1.5 Petrov and Chistakov (1964)

30 Blue 22.35 2 Petrov and Chistakov (1964)

32 Blue 17.56 1.5 Petrov and Chistakov (1964)

35 Blue 15.75 2.5 Petrov and Chistakov (1964)

36 Blue 10.18 1.5 Petrov and Chistakov (1964)

38 Blue 13.35 3 Petrov and Chistakov (1964)

40 Blue 16.69 5 Petrov and Chistakov (1964)

44 Blue 14.16 4 Petrov and Chistakov (1964)

45 Blue 24.5 3 Petrov and Chistakov (1964)

46 Blue 15.7 2 Petrov and Chistakov (1964)

47 Blue 13.19 2 Petrov and Chistakov (1964)

48 Blue 26.19 2 Petrov and Chistakov (1964)

49 Blue 19.07 2.6 Petrov and Chistakov (1964)

51 Blue 10.74 1.5 Petrov and Chistakov (1964)

53 Blue 16.01 1.5 Petrov and Chistakov (1964)

55 Blue 15.09 1.5 Petrov and Chistakov (1964)

56 Blue 17.12 3.5 Petrov and Chistakov (1964)

Tyubegatan — 22.51 Not specified Fedin (1981)

Gaurdak — 18.91 Not specified Fedin (1981)

Karlyuk — 20.13 Not specified Fedin (1981)

Okuzbulak — 18.3 Not specified Fedin (1981)

Akbash — 12.02 Not specified Fedin (1981)

Yuzhno-Lyalimkan — 19.92 Not specified Fedin (1981)

Kyzylmazar — 9.93 Not specified Fedin (1981)

North Gaurdak — 19.52 Not specified Fedin (1981)

Karlyuk horizon U. Carnallite 7.79 5.63 ave (0.29–25.36) Rayevskiy and Fiveg (1973)

Karlyuk horizon Ia 12.48 5.83 (0.33–31.2 Rayevskiy and Fiveg (1973)

Karlyuk horizon II 13.22 3.53 (0.51–13.0) Rayevskiy and Fiveg (1973)

Karlyuk horizon III 13.04 4.2 (0.58–15.95) Rayevskiy and Fiveg (1973)

Karlyuk horizon Mid. Carnallite 13.93 4.02 (0.3–17.5) Rayevskiy and Fiveg (1973)

Karlyuk horizon IV 13.88 5.63 (1.37–46.75) Rayevskiy and Fiveg (1973)

Karlyuk horizon V 15.21 5.05 (1.0–22.1) Rayevskiy and Fiveg (1973)

Karlyuk horizon VI 16.71 5.67 (0.55–31.5) Rayevskiy and Fiveg (1973)

Karlyuk horizon VII 17.01 5.55 (1.06–18.6) Rayevskiy and Fiveg (1973)

Karlyuk horizon VIII 17.41 9.5 (1.45–28.2) Rayevskiy and Fiveg (1973)

Karlyuk horizon IX 12.44 4.9 (1.12–17.36) Rayevskiy and Fiveg (1973)

Karlyuk Upper lens 7.14 1.38 Rayevskiy and Fiveg (1973)

Karlyuk Lower lens 16.63 2.94 Rayevskiy and Fiveg (1973)

Karlyuk Lower lens 3.05 4.13 Rayevskiy and Fiveg (1973)

Karlyuk U. Carnallite 11.41 5.15 Sedletskiy and Derevyagin (1980)

Karlyuk I 12.76 3.71 Sedletskiy and Derevyagin (1980)

Karlyuk II 11.36 3.4 Sedletskiy and Derevyagin (1980)

Table D-1. Grade data for the Central Asia Salt Basin.—Continued
Appendix D 93

Well or site Orebody

or layer

K2O

(%)

Thickness

(m) Reference

Karlyuk III 13.36 3.75 Sedletskiy and Derevyagin (1980)

Karlyuk Mid. Carnallite 8.92 1.47 Sedletskiy and Derevyagin (1980)

Karlyuk IV 15.29 3.12 Sedletskiy and Derevyagin (1980)

Karlyuk V 17.07 3.3 Sedletskiy and Derevyagin (1980)

Karlyuk VI 15.7 3.34 Sedletskiy and Derevyagin (1980)

Karlyuk VII 19 6.05 Sedletskiy and Derevyagin (1980)

Karlyuk VIII 18.75 9.48 Sedletskiy and Derevyagin (1980)

Karlyuk IX 17.1 3.52 Sedletskiy and Derevyagin (1980)

Dongusyrt 2D — 14.51 3.35 Kutuzov and Popov (1976)

Karlyuk VIII 17.41 >8 Vysotskiy and others (1988)

Karlyuk VII 17.01 >3 Vysotskiy and others (1988)

Karlyuk VI 16.71 >3 Vysotskiy and others (1988)

Karlyuk — 5 >3 Vysotskiy and others (1988)

Karlyuk — 7.02 >3 Vysotskiy and others (1988)

Karlyuk I 12.48 >3 Vysotskiy and others (1988)

Karlyuk II 13.22 >3 Vysotskiy and others (1988)

Karlyuk III 13.04 >3 Vysotskiy and others (1988)

Tyubegatan Lower II 22.5 5.1 Vysotskiy and others (1988)

Table D-1. Grade data for the Central Asia Salt Basin.—Continued

References Cited

Fedin, O.V., 1981, Otsenka perspektiv kaliyenosnosti 

verkhneyurskikh solyanykh otlozheniy yuga Sredney 

Azii [An evaluation of the prospects for potash-bearing 

capabilities in the Upper Jurassic salt deposits in southern 

Central Asia], in Yanshin, A.L., and Zharkov, M.A., eds., 

Stroyeniye i usloviya formirovaniya mestorozhdeniy 

kaliynykh soley [The structure and formation conditions 

of potash salt deposits]: Novosibirsk, USSR, Izd. Nauka, 

Sibirsk. Otdel., p. 171–176.

Kutuzov, A.P., and Popov, V.S., 1976, Novyye dannyye po 

geologii Donguzsyrta (Yugo-Vostochnaya Turkmeniya) 

[New data on the geology of Donguzsyrt, Southeast 

Turkmenia]: Sovetskaya Geologiya, v. 1976, no. 9, p. 137–

142.

Petrov, N.P., and Chistyakov, P.A., 1964, Lithologia solvevykh 

I krasnocvetnykh otljzenij yugo-eapadnykh otrogov gissara 

[Lithology salt and red deposits southwestern Gissar spurs]: 

Tashkent, Uzbekistan, Izdatelstvo Nauka Uzbekskoy SSR, 

221 p.

Rayevskiy, V.I., and Fiveg, M.P., 1973, Mestorozhdeniya 

kaliynykh soley SSSR; metody ikh poiskov i razvedki 

[Deposits of potassium salts in the USSR; methods of 

exploration and surveying]: Leniingrad, Izd. Nedra, 

Leningr. Otd., 344 p.

Sedletskiy, V.I., and Derevyagin, V.S., 1980, Stroyeniye 

i sostav kaliyenosnih otlozhyeniy Karlyukskogo 

myestorozhdyeniya [The structure and composition of the 

potassium-bearing Karlyukskogo deposits], in Zharkov, 

M.A., ed., Osobennosti stroeniia zalezhei bishofita i 

kaliinykh solei [Structural features of bischofite and 

potassium salt deposits]: Novosibirsk, Academiia Nauk 

SSSR, Institut geologgi i geofiziki, p. 70–90.

Vysotskiy, E.A., Garetskiy, R.G., and Kislik, V.Z., 1988, 

Kalienosnye basseiny mira [Potassium-bearing basins of the 

world]: Minsk, Izd. Nauka i Tekhnika, Byelorussian SSR, 

387 p.
94 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Appendix E. Thickness Data for Gissar and Amu Darya Tracts

By Greta J. Orris,1 Mark D. Cocker,1 and Jeff Wynn2

1

U.S. Geological Survey, Tucson, Arizona, United States.

2

U.S. Geological Survey, Vancouver, Washington, United States.

Drill holes and occurrences with potash thickness 

information in the Amu Darya (142sbK0005b) and Gissar 

(142mxK0005a) tracts were obtained primarily from Russian 

publications (below). Evaporitic salt is not exposed at the 

surface in the Amu Darya tract, so this list includes aggregate 

potash thicknesses for discrete sylvite and carnallite layers 

encountered in drill holes in the tract. Potash entries with 

zero value were included from areas lying outside the tracts 

to constrain the minimum-curvature gridding effort, thus 

allowing us to obtain a reasonable thickness for potash over 

the entire area of the tracts. Sedletskiy and Fedin (1981, 

fig. 2) and Khudaikuliev (1986) show that potash in the tracts, 

with the exception of the bottom of a single drill hole in the 

Beshkent Trough, is shallower than 3 kilometers (km).

Table E-1. Thickness data for Gissar and Amu Darya tracts, Central Asia.

[m, meter]

Name Latitude Longitude

Potash

thickness

(m)

Site type Reference

Urtabulak 39.017 64.013 6 Occurrence Fedin (1981)

Bagadzhin 10 39.217 62.667 2 Drill hole Khudaikuliev (1986)

Donguzsyrt 37.495 65.080 10 Occurrence Khudaikuliev (1986)

Gaurdak 560 37.877 66.026 >0 Drill hole Khudaikuliev (1986)

Karabil 96 37.683 66.202 >0 Drill hole Khudaikuliev (1986)

Khodzhambass 3 38.115 65.078 8 Drill hole Khudaikuliev (1986)

Metedzhan 4 38.893 64.089 >0 Drill hole Khudaikuliev (1986)

Okuzbulak 103 37.497 66.412 >0 Drill hole Khudaikuliev (1986)

Sunduklu 3 38.365 64.451 8 Drill hole Khudaikuliev (1986)

Akbash 38.172 66.584 9.5 Occurrence Rayevskiy and Fiveg (1973)

Gaurdak 37.844 66.054 9 Occurrence Rayevskiy and Fiveg (1973)

Khamkan 38.096 66.759 5 Occurrence Rayevskiy and Fiveg (1973)

Kugitang 37.879 66.416 5 Occurrence Rayevskiy and Fiveg (1973)

Skv. 72 37.564 66.320 5.5 Drill hole Rayevskiy and Fiveg (1973)

Skv. 50 37.554 66.334 3.9 Drill hole Rayevskiy and Fiveg (1973)

Karlyuk 87 37.533 66.373 0 Drill hole Sedletskiy and Derevyagin (1980)

Skv. 70 37.575 66.294 38 Drill hole Sedletskiy and Derevyagin (1980)

Skv. 110 37.615 66.344 0 Drill hole Sedletskiy and Derevyagin (1980)

Skv. 123 37.623 66.353 0 Drill hole Sedletskiy and Derevyagin (1980)

Figure E-1. Histogram showing potash thickness 

(in meters) in the Gissar and Amu Darya tracts.

0 5 10 15 20 25 30 35 40

Thickness, in meters

40

Frequency

20
Appendix E 95

Name Latitude Longitude

Potash

thickness

(m)

Site type Reference

Alyauduntau 2 38.411 65.608 10 Drill hole Sedletskiy and Fedin (1981)

Beshkent 4 38.781 65.633 10 Drill hole Sedletskiy and Fedin (1981)

Darbaz 1 39.183 64.834 5 Drill hole Sedletskiy and Fedin (1981)

Dengizkul 7 39.098 63.840 3 Drill hole Sedletskiy and Fedin (1981)

Karabai 1 38.600 66.565 7 Drill hole Sedletskiy and Fedin (1981)

Kuruksai 2 38.402 65.913 17 Drill hole Sedletskiy and Fedin (1981)

Metedzhan 2 38.893 64.089 10 Drill hole Sedletskiy and Fedin (1981)

Metedzhan 5 38.894 64.090 5 Drill hole Sedletskiy and Fedin (1981)

Pamuk 1 38.953 64.930 8 Drill hole Sedletskiy and Fedin (1981)

Sakar 2 38.883 63.251 10 Drill hole Sedletskiy and Fedin (1981)

Saman-Tepe 10 38.948 63.730 10 Drill hole Sedletskiy and Fedin (1981)

Shurtan 7 38.529 66.169 15 Drill hole Sedletskiy and Fedin (1981)

Urtabulak 2 39.017 64.013 10 Drill hole Sedletskiy and Fedin (1981)

West Zevardy 1 38.874 64.500 2 Drill hole Sedletskiy and Fedin (1981)

Zevardy 16 38.979 64.690 5 Drill hole Sedletskiy and Fedin (1981)

Adamtash 5 38.658 67.132 8 Drill hole Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Belesyainak 38.389 66.483 4.2 Occurrence Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Girsan 38.617 65.167 3 Occurrence Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Kamashi 38.733 65.427 3 Occurrence Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Karabay 38.600 66.565 7 Occurrence Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Karail 38.514 66.657 4.2 Occurrence Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Kishtuvan 39.128 63.345 6.5 Occurrence Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

North Kamashi 38.978 65.725 3.5 Occurrence Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Uzonshor 39.197 63.306 6.5 Occurrence Sedletskiy and Fedin (1981); Vysotskiy and others (1988)

Aizovat 38.864 65.325 3.5 Occurrence Vysotskiy and others (1988)

Chashtepe 39.199 63.584 6.5 Occurrence Vysotskiy and others (1988)

Darbaza 39.218 64.838 6.5 Occurrence Vysotskiy and others (1988)

Gumbulak 38.580 66.853 3.5 Occurrence Vysotskiy and others (1988)

Khauzak 39.142 63.669 6.5 Occurrence Vysotskiy and others (1988)

Kultak 38.75 64.883 3.5 Occurrence Vysotskiy and others (1988)

Kyzylbayrak 38.570 67.005 3.5 Occurrence Vysotskiy and others (1988)

Metedzhan 38.857 64.256 6.5 Occurrence Vysotskiy and others (1988)

Mobik 38.665 66.862 3.5 Occurrence Vysotskiy and others (1988)

Sakar 38.869 63.173 6.5 Occurrence Vysotskiy and others (1988)

Saman-Tepe 38.953 63.705 6.5 Occurrence Vysotskiy and others (1988)

Zevardy 38.975 64.713 3.5 Occurrence Vysotskiy and others (1988)

Karaul-Kuiu 1 38.554 63.547 4 Drill hole Zharkov and others (1982)

Severnyts Urtabulak 2 39.034 64.527 10 Drill hole Zharkov and others (1982)

Zevarda 8 38.950 63.845 2 Drill hole Zharkov and others (1982)

3 39.674 60.386 0 Drill hole Zharkov and others (1982)

4 39.874 60.704 0 Drill hole Zharkov and others (1982)

5 39.757 61.163 0 Drill hole Zharkov and others (1982)

6 39.980 61.679 0 Drill hole Zharkov and others (1982)

8 39.233 61.120 0 Drill hole Zharkov and others (1982)

9 38.899 61.056 0 Drill hole Zharkov and others (1982)

11 39.958 62.497 0 Drill hole Zharkov and others (1982)

12 39.374 67.179 2 Drill hole Zharkov and others (1982)

13 39.072 62.460 2 Drill hole Zharkov and others (1982)

14 38.805 62.712 2 Drill hole Zharkov and others (1982)

15 38.557 62.553 0 Drill hole Zharkov and others (1982)

16 38.669 63.074 3 Drill hole Zharkov and others (1982)

17 39.306 63.297 0 Drill hole Zharkov and others (1982)

18 39.253 63.463 5 Drill hole Zharkov and others (1982)

Table E-1. Thickness data for Gissar and Amu Darya tracts, Central Asia.—Continued
96 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Name Latitude Longitude

Potash

thickness

(m)

Site type Reference

19 39.077 63.632 8 Drill hole Zharkov and others (1982)

22 38.862 64.009 5 Drill hole Zharkov and others (1982)

23 38.971 64.067 6 Drill hole Zharkov and others (1982)

25 38.945 64.340 7 Drill hole Zharkov and others (1982)

26 39.064 64.466 8 Drill hole Zharkov and others (1982)

29 38.946 64.982 7 Drill hole Zharkov and others (1982)

30 38.752 64.802 5 Drill hole Zharkov and others (1982)

31 38.741 64.617 6 Drill hole Zharkov and others (1982)

32 38.430 64.649 8 Drill hole Zharkov and others (1982)

33 38.717 65.323 3 Drill hole Zharkov and others (1982)

34 38.778 65.493 4 Drill hole Zharkov and others (1982)

36 38.413 65.864 16 Drill hole Zharkov and others (1982)

38 38.349 61.737 0 Drill hole Zharkov and others (1982)

39 37.940 61.574 0 Drill hole Zharkov and others (1982)

40 37.276 60.817 0 Drill hole Zharkov and others (1982)

41 37.328 61.631 0 Drill hole Zharkov and others (1982)

42 38.132 62.423 0 Drill hole Zharkov and others (1982)

43 37.060 61.896 0 Drill hole Zharkov and others (1982)

45 36.499 62.822 0 Drill hole Zharkov and others (1982)

46 37.814 63.343 0 Drill hole Zharkov and others (1982)

47 38.933 64.818 7 Drill hole Zharkov and others (1982)

48 39.156 64.974 4 Drill hole Zharkov and others (1982)

49 39.080 65.359 2 Drill hole Zharkov and others (1982)

50 38.867 65.582 0 Drill hole Zharkov and others (1982)

Table E-1. Thickness data for Gissar and Amu Darya tracts, Central Asia.—Continued

References Cited

Fedin, O.V., 1981, Otsenka perspektiv kaliyenosnosti 

verkhneyurskikh solyanykh otlozheniy yuga Sredney 

Azii [An evaluation of the prospects for potash-bearing 

capabilities in the Upper Jurassic salt deposits in southern 

Central Asia], in Yanshin, A.L., and Zharkov, M.A., eds., 

Stroyeniye i usloviya formirovaniya mestorozhdeniy 

kaliynykh soley [The structure and formation conditions 

of potash salt deposits]: Novosibirsk, USSR, Izd. Nauka, 

Sibirsk. Otdel., p. 171–176.

Khudaikuliev, K., 1986, Osnovniye chyerti stroyeniya 

vyerhnyeyoorskoy galogyennoy formatsii i yeye rol’ v 

prognozirovanii po gryebyennih rifov v amudar’inskoy 

[Main structural features of the Upper Jurassic halogenous 

formation and its role in forecasting buried reefs in the Amu 

Darya syneclise], in Yanshin, A.L., and Merzlyakov, G.A., 

eds., Novye dannye po geologii solenosnykh basseinov 

Sovetskogo Soyuza [New data on the geology of saliferous 

basins of the Soviet Union]: Moscow, Nauka, p. 101–115.

Rayevskiy, V.I., and Fiveg, M.P., 1973, Mestorozhdeniya 

kaliynykh soley SSSR; metody ikh poiskov i razvedki 

[Deposits of potassium salts in the USSR; methods of 

exploration and surveying]: Leningrad, Izd. Nedra, Leningr. 

Otd., 344 p.

Sedletskiy, V.I., and Derevyagin, V.S., 1980, Stroyeniye 

i sostav kaliyenosnih otlozhyeniy Karlyukskogo 

myestorozhdyeniya [The structure and composition of the 

potassium-bearing Karlyukskogo deposits], in Zharkov, 

M.A., ed., Osobennosti stroeniia zalezhei bishofita i 

kaliinykh solei [Structural features of bischofite and 

potassium salt deposits]: Novosibirsk, Academiia Nauk 

SSSR, Institut geologgi i geofiziki, p. 70–90.

Sedletskiy, V.I., and Fedin, O.V., 1981, Lithofacies and 

potassium potential of Upper Jurassic halogen deposits in 

central Asia: Lithology and Mineral Resources, v. 16, no. 1, 

p. 83–92.

Vysotskiy, E.A., Garetskiy, R.G., and Kislik, V.Z., 1988, 

Kalienosnye basseiny mira [Potassium-bearing basins of the 

world]: Minsk, Izd. Nauka i Tekhnika, Byelorussian SSR, 

387 p.

Zharkov, M.A., Blagovidov, V.V., Zharkova, T.M., 

and Merzlyakov, G.A., 1982a, Kvoprosu o stroyenii 

pozdnyeyoorskih solyenosnih otlozhyeniy Sryednyey 

Azii [The problem of the structure of Late Jurassic 

saliferrous sediments of Central Asia], in Yanshin, A.L., ed., 

Osobennosti stroenya osadocgnikh formatsiy [Structural 

characteristics of sedimentary formations]: Novosibirsk, 

Trudy Instituta Geologii i Geofiziki, p. 3–18.
Appendix F 97

Appendix F. Generalized SYSTAT Script for Estimation of 

Undiscovered Contained K2O in Central Asia Salt Basin Tracts

By Greta J. Orris1

1

U.S. Geological Survey, Tucson, Arizona, United States.

This appendix contains a list of variables (table F-1) 

and a generalized SYSTAT script for in-place ore and K2O 

estimates for stratabound tracts in the Central Asia Salt 

Basin (table F-2). Initial estimates were made using average 

densities for sylvinite and carnallitite. The estimates were 

rerun in November, 2014, using a defined relationship between 

potash grade and density. The revised simulations use data 

from the Congo Basin (Rauche and others, 2013) that became 

available after the initial estimations were made; these new 

data allow a linear relationship between potash grade and 

density to be estimated using regressions for carnallitite and 

sylvinite (fig. F-1).

Potential users should note that literature for the area 

reported no data on the ratios of sylvite to carnallite in the 

Central Asia Salt Basin. Information was limited to reports 

of carnallitite as the dominant potash mineralization, with 

variably-sized local areas and horizons dominated by sylvite 

mineralization. Therefore, for the purposes of determining 

density, mineralization is assumed to be only carnallite when 

the grade is less than 16.9 percent K2O and only sylvite when 

the grade is higher. This assumption leads to a discernable 

linear feature that corresponds to this grade break when 

plotting the K2O grades versus in-place ore tonnages estimated 

by the SYSTAT script Monte Carlo simulation (fig. F-2).

Distributions

Normal distribution: ZRN (mean, standard deviation)

 Triangular distribution: TRRN (minimum, maximum, 

mode)

density = 2.177–0.003×grade

2.06

2.08

2.10

2.12

2.14

10 15 20 25 30 35 40 45

Sylvinite grade, in percent K2O

Density

density = 2.044–0.027×grade

Carnallitite grade, in percent K2

O

Density

1.9

1.8

1.85

1.75

1.7

1.65

1.6

6 7 8 9 10 11 12 13 14 15 16 17

B

A

Figure F-1. Graphs showing relationship 

between grade (in percent K2O [potassium oxide]) 

and density for carnallitite (A) and sylvinite (B). 

Resulting regression line and equation are also 

shown.
98 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

300 

320 

340 

360 

220 

240 

260 

280 

140 

160 

180 

200 

380 

400 

420 

440 

60 

80 

100 

120 

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

Potash grade, in percent K2O

Total in-place tonnage, in million metric tons

CAsia Fig F-2 gjo2

Figure F-2. Select plot showing potash grade and in-place tonnage estimations from the adaptive geometric 

estimation (AGE) method, SYSTAT Monte Carlo simulation. Grade break between carnallitite and sylvinite ore is 

discernable as a linear cluster of data points at about 17 percent K2O (potassium oxide).
Appendix F 99

Table F-1. Variables used in the SYSTAT script to estimate undiscovered K2O.

Variable Definition

CDENSITY Calculate, carnallitite density

COT Calculate, carnallitite, ore tonnage

COTADJ Calculate, carnallitite ore tonnage, adjusted for anomalies and embayments

CTK2OADJ Calculate, contained K2O in adjusted carnallitite ore tonnage

EMB Input, adjustment for edge embayment, as distribution (in percent)

HOLES Input, adjustment for anomalies, as distribution (in percent)

KGRADE Input, K2O grade, as distribution, in percent

KGRADE2 Conversion, KGRADE from percent to decimal number

KVOL Input, volume of potash area, as distribution or single number, in cubic kilometers (km3)

SDENSITY Calculate, sylvinite density

SOT Calculate, sylvinite, ore tonnage

SOTADJ Calculate, sylvinite ore tonnage, adjusted for anomalies and embayments

STK2OADJ Calculate, contained K2O in adjusted sylvinite ore tonnage

TOTADJ Calculate, HOLES + EMB

TOTADJ2 Conversion, TOTADJ from percent to decimal number

TOTALK2O Calculate, total tons contained K2O in place, in billions of metric tons (Bt) with known K2O subtracted

TOTALORE Calculate, total tons of ore/mineralized rock in-place, in billions of metric tons (Bt) with known resources

subtracted

Variables

See table F-1.

Script

See table F-2.

References Cited

Rauche, Henry, van der Klauw, Sebastiaan, and Linsenbarth, 

Ralf, 2013, Update of the NI 43-101 Technical Report 

for MagMineral’s Mengo Permit area, Kouilou region, 

Republic of Congo: Erfurt, Germany, ERCOSPLAN 

Ingenieurgesellschaft Geotechnik und Bergbau mbH.
100 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Table F-2. Generalized SYSTAT script.

[black text is script; red text indicates values that need to be input for each tract; blue italicized text is an explanation of script step]

Script Explanation

CLASSIC ON

OUTPUT “location for output filename”/NOSCREEN Specify location and name for output file

KGRADE=0 Set initial value to zero

TOTADJ=0 Set initial value to zero

TOTADJ2=0 Set initial value to zero

CDENSITY=0 Set initial value to zero

SDENSITY=0 Set initial value to zero

COT=0 Set initial value to zero

COTADJ=0 Set initial value to zero

CTK20ADJ=0 Set initial value to zero

SOT=0 Set initial value to zero

SOTADJ=0 Set initial value to zero

STK2OADJ=0 Set initial value to zero

FOR I =1 TO 5000 5,000 iterations

KVOL=TRRN(min,max,mode) Specify tract volume as distribution in km3

KGRADE=ZRN(mean,s.d.) Specify potash grade distribution in percent

KGRADE2=CGRADE/100 Convert grade from percent to decimal 

IF KGRADE2<0.04 THEN KGRADE2=0.04 Set lower limit of 4 percent K2

O for KGRADE2 (K team specified for

Central Asia)

IF KGRADE2>0.22 THEN KGRADE2=0.22 Set upper limit of 22 percent K2

O for KGRADE2 (K team specified for

Central Asia)

HOLES=TRRN(min,max,mode) Specify distribution of anomalies (K team specified for each tract)

EMB=TRRN(min,max,mode) Specify distribution of embayments (K team specified for each tract)

TOTADJ=(HOLES+EMB) Calculate total adjustments (in percent)

TOTADJ2=TOTADJ/100 Convert total adjustments from percent to decimal

IF KGRADE2<0.169 THEN BEGINBLOCK If grade is less than 16.9% K2

O, assume mineralization is carnallite and

calculate following values

 CDENSITY=2.044-(KGRADE*0.027) Calculate carnallitite density

 IF CDENSITY<1.602 THEN CDENSITY=1.602 Set lower density limit at that of 100% carnallite

 SDENSITY=0 Set sylvinite density to 0

 COT=KVOL*CDENSITY Calculate in-place ore tonnage for carnallitite

 COTADJ=COT-(COT*TOTADJ2) Adjust in-place ore tonnage for areas of no mineralization

 CTK2OADJ=COTADJ*KGRADE2 Calculate contained K2

O from adjusted ore tonnage

ENDBLOCK End calculation resulting from grade <0.169

ELSE BEGINBLOCK If KGRADE2 is NOT <0.169, assume mineralization is sylvinite and

calculate the following values

 CDENSITY=0 Set carnallite density to 0

 SDENSITY=2.177-(KGRADE*0.003) Calculate sylvinite density

 SOT=KVOL*SDENSITY Calculate in-place ore tonnage for sylvinite

 SOTADJ=SOT-(SOT*TOTADJ2) Adjust in-place ore tonnage for areas of no mineralization

 STK2OADJ=SOTADJ*KGRADE2 Calculate contained K2

O from adjusted ore tonnage

ENDBLOCK End calculations resulting from KGRADE2 NOT <0.169

ENDIF End conditional calculations

TOTALORE=COTADJ+SOTADJ-[total ore, known resources] Calculate total ore tons (minus known resources), Bt

TOTALK2O=CTK2OADJ+STK2OADJ-[total K2O, known 

resources]

Calculate contained K2O tons (minus known resources), Bt

PRINT KVOL, KGRADE, HOLES, EMB, TOTADJ,

CDENSITY, COT, COTADJ, CTK2OADJ, SDENSITY, SOT,

SOTADJ, STK2OADJ , TOTALORE, TOTALK2O

Print variables

NEXT Go to next iteration

OUTPUT *

CLASSIC OFF

END
Appendix G 101

Appendix G. Glossary of Terms Used in 

Description of Evaporites

By Mark D. Cocker1 and Greta J. Orris1

1

U.S. Geological Survey, Tucson, Arizona, United States.

Allochthonous salt Sheetlike salt bodies 

emplaced at stratigraphic levels above the 

autochthonous source layer. Allochthonous 

salt lies on stratigraphically younger strata; 

theoretically, allochthonous salt could overlie 

older strata, but such examples have not yet 

been reported (Jackson and Talbot, 1991).

Autochthonous salt Salt body resting on 

the original strata or surface on which it 

accumulated by evaporation (Jackson and 

Talbot, 1991).

Bittern The bitter liquid remaining 

after seawater has been concentrated by 

evaporation until most of the sodium chloride 

has crystallized out (Neuendorf and others, 

2005).

Bittern salts Any of the salts that may be 

extracted from the bittern of a saltworks or 

from a comparable natural solution; such as 

magnesium chloride, magnesium sulfate, 

bromides, iodides, and calcium chloride 

(Neuendorf and others, 2005).

Brachyanticline A short, broad anticline 

(Neuendorf and others, 2005). A short 

anticlinal fold of layers of rock having an oval 

cross section. The layers of rock that form the 

brachyanticline slope away from the central 

part of its crest on all sides. A brachyanticline 

is represented on a geological map in the form 

of concentric oval rings, with the older rocks 

in the center; the rocks become progressively 

younger toward the periphery (Prokhorov, 

1970–1979).

Cap rock [tectonics] In a salt dome, an 

impervious body of anhydrite and gypsum, 

with minor calcite and sometimes with sulfur 

that overlies the salt body, or plug. It probably 

results from accumulation of the less soluble 

minerals of the salt body during leaching in 

the course of its ascent (Neuendorf and others, 

2005).

Carnallite A primary potash ore mineral, 

KMgCl3•6H2O, and that also is a source of 

magnesium in some deposits. Usually occurs 

as crystalline or granular masses. Mode of 

occurrence—occurs chiefly as a component of 

extensive thick sedimentary saline deposits, 

often associated with kieserite, halite, sylvite, 

and polyhalite (Roberts and others, 1974; 

Neuendorf and others, 2005).

Carnallitite A rock largely composed of a 

mixture of carnallite and halite (salt).

Cycle Many sedimentary sections exhibit 

rhythmicity in the form of regularly 

alternating beds traceable over long distance, 

or a repetition of larger units which are 

referred to as sedimentary sequences or 

cycles. Rhythmic and cyclic sequences occur 

worldwide on various scales in presumably 

every environmental and stratigraphic system 

(Einsele, 2000).

Dewatering The expulsion of water 

from sediments during diagenesis or 

metamorphism. The water may have been 

present in the form of interstitial pore waters 

or water bound to hydrous minerals, such 

as certain clays or gypsum (see page 11, 

Friedman and others, 1992; Neuendorf and 

others, 2005).

Diapir [structural geology] A dome or 

anticlinal fold in which the overlying rocks 

have been ruptured by the squeezing-out of 

plastic core material. Diapirs in sedimentary 

strata usually contain cores of salt or shale 

(Neuendorf and others, 2005).

Evaporite A sedimentary rock primarily 

composed of minerals produced from a saline 

solution as a result of extensive or total 

evaporation of the solvent. Examples include 

gypsum, anhydrite, other diverse sulfates, 

halite (rock salt), primary dolomite, and 

various nitrates and borates (Neuendorf and 

others, 2005).
102 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, and Afghanistan

Gypsum A widely distributed mineral 

consisting of hydrated calcium sulfate: 

CaSO4·2H2O. Usually occurs as crystalline 

masses, fine to coarse granular; fibrous; 

pulverent; concretionary. Mode of 

occurrence—occurs abundantly and 

widespread chiefly in sedimentary deposits; 

in saline lakes and playas; as efflorescence 

on certain soils, in the oxidized parts of ore 

deposits; and in deposits associated with 

volcanic activity (Roberts and others, 1974). 

It is the most common sulfate mineral, 

and is frequently associated with halite 

and anhydrite in evaporites, forming thick, 

extensive beds interstratified with limestone, 

shale, and clay (especially in rocks of Permian 

and Triassic age) (Neuendorf and others, 

2005). It may alter to anhydrite under burial 

metamorphic conditions and release its water 

of hydration (Adams, 1970).

Halite NaCl, an abundant evaporite mineral. 

Usually occurs as crystalline masses, granular 

and rarely columnar or stalactitic. Mode of 

occurrence—occurs widespread chiefly as 

extensive sedimentary deposits ranging from a 

few centimeters to more than several thousand 

meters in thickness; as efflorescence in playa 

deposits, and as a sublimation product in 

areas of volcanism (Roberts and others, 1974; 

Neuendorf and others, 2005).

Halokinesis (1) A class of salt tectonics 

in which salt flow is powered entirely by 

gravity in the absence of significant lateral 

tectonic forces Jackson and Talbot (1991). 

(2) The deformation of halite by flowage. 

Mechanisms cited for this process include 

gravity flow, tectonic thrusting, and diapirism 

(Kyle and Posey, 1991; Neuendorf and others, 

2005).

Hartsalz Hard salt, typically a mixture of 

sylvinite and kieserite, with some anhydrite, 

found in the Stassfurt salt deposits (U.S. 

Bureau of Mines, 1996).

Horizon (1) In geology, any given definite 

position or interval in the stratigraphic column 

or the scheme of stratigraphic classification. 

(2) An identifiable rock stratum regionally 

known to contain or be associated with rock 

containing valuable minerals (U.S. Bureau of 

Mines, 1996).

Horse A mining term for a barren mass 

of country rock occurring within a vein 

(Neuendorf and others, 2005).

Intracratonic basin A basin formed within 

the interior region of a continent, away 

from plate boundaries. It develops where 

there is subsidence of a part of a craton, 

probably owing to thermal subsidence 

or an unsuccessful rift (Neuendorf and 

others, 2005).

Potash (1) A generic industry term for 

potassium-bearing salts that includes the 

commodities potassium chloride, potassium 

sulfate, potassium nitrate, and potassium 

oxide; (2) A generic geologic term that 

mainly includes the minerals sylvite, 

carnallite, kainite, and langbeinite; (3) A 

generic geologic term for a sedimentary rock 

containing significant amounts (commonly 

more than 20 percent by weight) of soluble, 

precipitated potassium- and magnesiumchloride and sulfate minerals intermixed 

or interlayered with halite and other bittern 

minerals. Variable amounts of insoluble 

minerals such as gypsum, anhydrite, clay, 

quartz, and hematite are generally present.

Rim syncline A fold having an arcuate or 

subcircular axial tract on the outer margin of 

a salt upwelling. Rim syncline is a nongenetic 

term, but in the context of salt tectonics a rim 

syncline typically results from salt withdrawal 

in the source layer. Peripheral sinks of 

sediments accumulate within rim synclines 

(Nettleton, 1934; Jackson and Talbot, 1991; 

Neuendorf and others, 2005).

Safety pillar A significant thickness, 

usually about 150 meters, of salt that is left 

in place below the brine saturated caprock 

and surrounding water-bearing strata to act 

as a seal in a diapiric salt structure (Heim and 

Potthoff, 1983). See “salt back.”

Saline giant A term used to describe thick, 

basin‐filling evaporite units; synonymous with

mega-evaporites. Mineralogies are dominated 

by halite and (or) anhydrite, along with 

varying amounts of carbonates and potash 

salts (Warren, 2006, 2010).

Salt (1) A general term for naturally 

occurring sodium chloride, NaCl; (2) 

A geologic term for a sedimentary rock 

dominantly composed of halite formed by 

evaporation of saline water, usually seawater. 

Salt as a rock may contain lesser amounts of 

other evaporite-related minerals, including 

potassium- and magnesium-bearing minerals 

and variable amounts of insoluble minerals 
Appendix G 103

such as gypsum, anhydrite, clay, quartz, 

and hematite. Crystalline salt is found in 

playa lakes, bedded salt deposits, and salt 

structures (operational definition); (3) Usage 

as a commodity such as a food supplement, 

in industrial applications, or as a source of the 

chemicals sodium and chlorine.

Salts (1) A generic term for chemicals 

classified as chlorides, sulfates, bromides, 

and iodides; (2) A generic term for minerals 

classified as chlorides, sulfates, bromides, and 

iodides. This can include sylvite, carnallite, 

halite, and other minerals (operational 

definition; see appendix A for some of these 

minerals).

Salt anticline (1) A diapiric or piercement 

structure, like a salt dome except that the salt 

core is linear rather than equidimensional, 

such as the salt anticlines in the Paradox basin 

of the central Colorado Plateau (Neuendorf 

and others, 2005); (2) Elongated upwelling of 

salt having concordant overburden (DeGolyer, 

1925; Harrison and Bally, 1988; Jackson and 

Talbot, 1991).

Salt back A significant thickness of salt 

above the mining horizon maintained to 

ensure a water seal between mine openings 

and overlying strata that contain groundwater. 

Salt back thickness depends on mining 

method and nature of water saturation 

and rock competency in overlying beds 

(Holter, 1969).

Salt diapir A mass of salt that has flowed 

ductilely and appears to have discordantly 

pierced or intruded the overburden. In its 

broadest sense, “diapir” includes (1) lateral or 

vertical intrusion of any shape, (2) upwelling 

of buoyant or non-buoyant rock or magma, or 

(3) emplacement by passive piercement or by 

faulting of prekinematic overburden (Mrazec, 

1907; Jackson and Talbot, 1991).

Salt dome (1) A diapir or piercement 

structure with a central, nearly 

equidimensional salt plug, generally 1 to 

2 kilometers (km) or more in diameter, which 

has risen through the enclosing sediments 

from a mother salt bed (source layer) 5 km 

to more than 10 km beneath the top of the 

plug. Many salt plugs have a cap rock of 

less soluble evaporite minerals, especially 

anhydrite. The enclosing sediments are 

commonly turned up and complexly faulted 

next to a salt plug, and the more permeable 

beds serve as reservoirs for oil and gas 

(U.S. Bureau of Mines, 1996); (2) An 

imprecise, general term for a domal upwelling 

comprising a salt core and its envelope of 

deformed overburden. The salt may or may 

not be discordant (Harris and Veatch, 1899; 

Jackson and Talbot, 1991).

Salt glacier Sheetlike extrusion of salt 

flowing from an exposed diapir and spreading 

subaqueously or subaerially (Jackson and 

Taylor, 1991).

Salt horse A dome-shaped barren zone 

generally consisting of halite that crosscuts 

potash-bearing salt beds. Bedding is 

continuous through the halite, but is thinner 

than the potash-bearing salt beds. Halite is 

believed to have replaced the potash-bearing 

salt beds in the salt horse through upward 

movement of saline brines (Linn and Adams, 

1963).

Salt pillow A subcircular upwelling of salt 

having concordant overburden (Jackson and 

Talbot, 1991).

Salt plug The salt core of a salt dome. It is 

nearly equidimensional, about 1 or 2 km in 

diameter, and has risen through the enclosing 

sediments from a mother salt bed (source 

layer) 5 to 10 km below (Neuendorf and 

others, 2005).

Salt solutioning A partial to complete 

dissolution of salts, commonly resulting in 

collapse of overlying strata, attributed to 

ascending or descending less saline water or 

brine (Holter, 1969).

Salt stock (syn: salt plug; Trusheim, 1957; 

Jackson and Talbot, 1991; Neuendorf and 

others, 2005) A pluglike salt diapir having 

subcircular planform.

Salt structure A generic term used in 

petroleum, salt, and other geologic literature 

to refer to geologic structures formed partly 

or wholly from the movement and (or) 

deformation of salt (see halokinesis or salt 

tectonics); may include salt anticlines, salt 

diapirs, salt domes, salt pillows, salt stocks, 

salt plugs, salt walls, and other structures 

(operational definition).

Salt tectonics (syn: halotectonics): Any 

tectonic deformation involving salt, or other 

evaporites, as a substratum or source layer; 

it includes halokinesis (Trusheim, 1957; 
104 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, and Afghanistan

Jackson and Talbot, 1986; Jackson and 

Talbot, 1991).

Salt wall An elongated upwelling of 

diapiric (discordant) salt, commonly forming 

sinuous, parallel rows (Trusheim, 1960; 

Jackson and Talbot, 1991).

Salt weld Surface or zone joining strata 

originally separated by autochthonous or 

allochthonous salt. The weld is a negative 

salt structure resulting from the complete or 

nearly complete removal of intervening salt. 

The weld can consist of brecciated, insoluble 

residue containing halite pseudomorphs or 

of salt too thin to be resolved in reflectionseismic data. The weld is usually but not 

always marked by a structural discordance. 

Another distinctive feature of welds is a 

structural inversion above them (Jackson and 

Talbot, 1991).

Salt withdrawal (syn: salt expulsion; Jackson 

and Talbot, 1991; Neuendorf and others, 

2005) Mass transfer of salt over time without 

obvious change in salt area in cross section. 

Examples are the migration of salt from 

the flanks of a salt pillow into its core as it 

evolves into a diapir or the flow of salt along 

a salt wall into local culminations that evolve 

into salt stocks.

Source layer (syn: mother salt) Layer 

supplying salt for the growth of salt 

structures; the source layer is a particular type 

of substratum (Jackson and Talbot, 1991).

Stratabound Said of a mineral deposit 

confined to a single stratigraphic unit 

(Neuendorf and others, 2005).

Substratum An underlying layer; in salt 

tectonics, substratum refers to the ductile 

layer below a brittle overburden and above 

the subsalt strata or basement. “Substratum” 

is a term more general than source layer; 

the substratum mayor may not give rise to 

upwelling structures (Jackson and Taylor, 

1991).

Subrosion (syn: postburial 

dissolution) Subrosion is the process by 

which soluble rocks in the underground are 

dissolved by groundwater or water penetrating 

from the surface. Subrosion takes place where 

soluble rocks are not protected by a layer 

of impermeable rocks (Rauche and van der 

Klauw, 2011).

Subsalt strata Sedimentary unit 

immediately underlying salt (Jackson and 

Talbot, 1991).

Sylvite The mineral sylvite, KCl, is the 

principal ore mineral of potassium. Usually 

in crystalline masses, compact to granular, as 

crusts, and columnar. Mode of occurrence: 

Occurs chiefly as extensive thick sedimentary 

deposits, typically associated with halite, 

gypsum, anhydrite, carnallite, polyhalite, 

kieserite, and kainite (Roberts and others, 

1974; Neuendorf and others, 2005).

Sylvinite A mixture of halite and sylvite, 

mined as a potash ore; a rock that contains 

chiefly impure potassium chloride (Neuendorf 

and others, 2005).

Turtle-structure anticline (1) Mounded 

strata between salt diapirs having a flat 

base and rounded crest over a local primary 

increase in sedimentary thickness; the 

anticline may or may not be cored by a low 

salt pillow. The turtle structure forms between 

diapirs whose flanks subside because of 

regional extension or between salt structures 

evolving from pillows to diapirs (Trusheim, 

1957; Neuendorf and others, 2005); (2) Strata 

mounded between salt diapirs and having a 

flat base and rounded crest over a sedimentary 

thick; the anticline mayor may not be cored 

by a low salt pillow. The turtle structure forms 

by structural inversion of a primary peripheral 

sink when salt is withdrawn from the margins 

of the peripheral sink by growing diapirs. 

The planform of turtle structures is typically 

highly irregular.

References Cited

Adams, S.S., 1970, Ore controls, Carlsbad 

Potash District, Southeast New Mexico, 

in Rau, J.L., and Dellwig, L.F., Third 

Symposium on salt, volume 1: Cleveland, 

Ohio, Northern Ohio Geological Society, p. 

246–257.

DeGolyer, E.L., 1925, Discovery of potash 

salts and fossil algae in Texas salt dome: 

American Association of Petroleum 

Geologists Bulletin, v. 9, no. 2, p. 348–349.

Einsele, G., 2000, Sedimentary basins—

evolution, facies, and sediment budget: 

New York, Springer, 792 p.
Appendix G 105

Friedman, G.M., Sanders, J.E., and Kopaskamerkee, D.C., 1992, Principles of 

sedimentary deposits—stratigraphy and 

sedimentology: New York, MacMillan 

Publishing Company, 43 p. 

Harris, G.D., and Veatch, A.C., 1899, A 

preliminary report on the geology of 

Louisiana: Baton Rouge, Geological 

Survey of Louisiana Report, 324 p.

Harrison, J.C., and Bally, A.W., 1988, Cross 

sections of the Devonian to Mississippian 

fold belt on Melville Island, Canadian 

Arctic Islands: Canadian Society of 

Petroleum Geologists, v. 36, p. 311–332.

Heim, W.A., and Pothoff, A.H., 1983, Potash 

mining in steep deposits (salt domes), in

McKercher, R., ed., Potash ’83: New York, 

Pergamon Press, p. 79–84.

Holter, M.E., 1969, The Middle Devonian 

Prairie Evaporite of Saskatchewan: 

Saskatchewan Department of Mineral 

Resources Report 123, 134 p.

Jackson, M.P.A., and Talbot, 1986, External 

shapes, strain rates, and dynamics of salt 

structures: Geological Society of America 

Bulletin, v. 97, p. 305–323.

Jackson, M.P.A., and Talbot, C.J., 1991, A 

glossary of salt tectonics: Texas Bureau of 

Economic Geology Geological Circular 

91-4, 44 p. 

Kyle, J.R., and Posey, H.H., 1991, 

Halokinesis, cap rock development, and 

salt dome mineral resources, in Melvin, 

J.L., ed., Evaporites, petroleum and mineral 

resources: New York, Elsevier, p. 413–474.

Linn, K.O., and Adams, S.S., 1963, Barren 

halite zones in potash deposits, Carlsbad, 

New Mexico, in Rau, J.L., ed., Second 

Symposium on Salt: Cleveland, OH, 

Northern Ohio Geological Society, p. 

59–69.

Mrazec, L., 1907, Despre cute cu sîmbure de 

strapungere [On folds with piercing cores]: 

Romania, Buletinul Societatiide de ştiinţe, 

v. 16, p. 6–8.

Nettleton, L.L., 1934, Fluid Mechanics of 

Salt Domes: Bulletin of the American 

Association of Petroleum Geologists, v. 18, 

no. 9, p. 1175–1204. 

Neuendorf, K.K.E., Mehl, Jr., J.P., and 

Jackson, J.A., 2005, Glossary of Geology 

(5th ed.): Alexandria, Virginia, American 

Geological Institute, 799 p.

Prokhorov, A.M., ed., 1970–1979, The 

Great Soviet Encyclopedia: New York, 

Macmillan Inc., 31 volumes and 3 volumes 

of indexes.

Rauche, H., and van der Klauw, S., 2011, 

Technical report and resource report for the 

Danakhil potash deposit, Afar State, State/

Ethiopia: Erfurt, Germany, ERCOPSPLAN 

Ingenieurgesellschaft, 128 p. [plus 

appendixes.] 

Roberts, W.L., Rapp, Jr., G.R., and Weber, 

Julie, 1974, Encyclopedia of minerals: New 

York, Van Nostran Reinhold Company, 693 

p.

Trusheim, Ferdinand, 1957, Über halokinese 

und ihre bedeutung für die strukturelle 

entwicklung Norddeutschlands [On 

halokinesis and its significance for the 

structural development of North Germany]: 

Zeitschrift für Deutsche Geologische 

Gesellschaft, v. 109, p. 111–151.

Trusheim, Ferdinand, 1960, Mechanism 

of salt migration in northern Germany: 

Bulletin of the American Association 

of Petroleum Geologists, v. 44, no. 9, p. 

1519–1540.

U.S. Bureau of Mines, 1996, Dictionary 

of mining, mineral, and related terms: 

U.S. Bureau of Mines Report SP-96-1, 

CD-ROM.

Warren, J.K., 2006, Evaporites—Sediments, 

resources and hydrocarbons: Berlin, 

Springer-Verlag, 1,035 p.

Warren, J.K., 2010, Evaporites through 

time—Tectonic, climatic, and eustatic 

controls in marine and nonmarine deposits: 

Earth-Science Reviews, v. 98, no. 3–4, 

p. 217–268.
106 Geology and Undiscovered Resource Assessment, Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan

Appendix H. The Assessment Team

Jeff Wynn, Ph.D., is a research geophysicist with the U.S. Geological Survey (USGS) 

at the Cascades Volcano Observatory in Vancouver, Washington. He has authored over 

220 books, papers, and maps in geophysics, mineral resource assessments, astrophysics, 

and ocean engineering. He authored the first 3D geologic map, and the first age-correlated 

mineral resource assessment of southern Venezuela. He has served as a U.S. diplomat and 

USGS mission chief in Venezuela and Saudi Arabia. He served a 5-year assignment as chief 

scientist for volcano hazards of the U.S. Geological Survey, and holds three patents in mineral 

exploration technology and deep ocean geophysical mapping.

Greta J. Orris, Ph.D., is a research geologist with the USGS in Tucson, Arizona. She 

specializes in industrial minerals, tools and methodologies for quantitative assessment of 

these and other minerals, and is a senior USGS research scientist for mineral economics. 

She has served as a leader of mineral resource assessment teams evaluating a wide range of 

commodities in North and South America, Europe, Asia, and Africa.

Mark D. Cocker, Ph.D., PG, is an emeritus research geologist with the USGS. His background 

is in global potash assessment, lateritic, supergene rare earth elements, precious and base metals 

in the western US, industrial minerals in Georgia, and hydrocarbon exploration in Alaska. His 

work has involved field mapping, drilling, geochemical sampling, petrography, geophysical 

surveys, GIS mapping and analysis. He has authored over 170 papers, abstracts, maps, and 

digital publications. He has been a member of several mineral resource assessment teams.

Pamela Dunlap, M.S., is a geologist with the USGS in Tucson, Arizona. She worked as 

an exploration geologist for several mining companies in Nevada, Montana, Idaho, and 

Washington and also as a research geologist for various state geological surveys (Idaho, 

Montana, and Washington) prior to joining the USGS in 1992. She has done mineral-resource 

assessment work in Idaho (phosphate) and Montana (oil shale) under contract to the USGS. She 

has prepared many geologic map and mineral-resource assessment products in a geographic 

information system (GIS) while with the USGS.

James D. Bliss, M.S., is an industrial mineral and spatial modeling specialist with the USGS in 

Tucson, Arizona. He has developed grade and tonnage models suitable for use in quantitative 

assessment for a number of mineral-deposit types including low-sulfide gold quartz veins, and 

gold placers, among others. He has participated in a number of mineral resources assessment 

teams. He has developed models and grade and tonnage databases for numerous industrial 

minerals including graphite, diamonds, and pegmatites.

Bruce Lipin, Ph.D., is an emeritus geologist with the USGS in Reston, Virginia. He is a 

specialist in ultramafic rocks and their mineral resources, and mineral resource assessments.

Gregory T. Spanski, Ph.D., is an emeritus geologist with the USGS in Denver, Colorado. He is 

a mineral resource specialist for Africa, and a former university professor.

Chao Yang, Ph.D., is a senior oil and gas and evaporite geologist with Saskatchewan Energy 

and Resources, Regina, Saskatchewan, Canada.

Mirosław Słowakiewicz, Ph.D., is a sedimentary geologist with the Polish Geological 

Institute–National Research Institute, Warsaw, Poland.

Robert J. Ryan, Ph.D., is a geologist and section leader with the Nova Scotia Department of 

Natural Resources, Nova Scotia, Canada.
Menlo Park Publishing Service Center, California

Manuscript approved for publication, December 21, 2015

Edited by Sarah E. Nagorsen

Layout and design by Sharon L. Wahlstrom 
Printed on recycled paper

Wynn and others— Geology and Undiscovered Resource Assessment of the Potash-Bearing Central Asia Salt Basin, Turkmenistan, Uzbekistan, Tajikistan, and Afghanistan—Scientific Investigations Report 2010–5090–AA

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20105090AA