Geochemical Distribution of 

Some Metals in the 

Moenkopi Formation and 

Related Strata, 

Colorado Plateau Region 

By ROBERT A. CADIGAN 

GEOLOGICAL SURVEY BULLETIN 1344 

A study of the concentrations of metals, their 

covariance, and geochem.ical associations 

in members and sedimentary rock facies 

of the Moenkopi Formation and 

related lithologic units 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 197 l 
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary 

GEOLOGICAL SURVEY 

W. A. Radlinski, Acting Director 

Library of Congress catalog-card No. 74-179646 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washinjlton, D.C. 20402 - Price 35 cents (paper cover) 

Stock Number 2401-1197 
CONTENTS 

Abstract ----------------------------------------------------------------------------------------------------------------

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

Purpose and scope of investigation _________________________________________________________ _ 

Geographic and geologie setting--------------------------------------------------------------

Previous work ----------------------------------------------------------------------------------------------

Acknowledgments ----------------------------------------------------------------------------------------

Stratigraphy --------------------------------------------------------------------------------------------------------

Petrology ---------------------------------------------------------------------------------------------------------------

Observations -------------------------------------------------------------------------------------------------

Interpretations ________________________________________________ --------------------------------------------

Geochemical studies --------------------------------------------------------------------------------------------

Sampling and analytical methods ------------------------------------------------------------

Elements studied ----------------------------------------------------------------------------------------

Statistical analysis ----------------------------------- -----------------------------------------------

Stratigraphic comparisons _______________ ------------------------------------------------------. 

Facies comparisons ----------------------------------------------------------------------------------- Geochemical association of the metals ___________________________________________________ _ 

Textural and compositional comparisons _______________________________________________ _ 

Locality comparisons --------------------------------------------------------------------------------

Gold ----------------------------------------------------------------------------------------------------------------

Summary and conclusions --------------------------------------------------------------------------------

References cited ------------------------------------ -------------------------------------------------------------

ILLUSTRATIONS 

Page 

1 

~ 2 

2 

3 

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4 

4 

9 

9 

10 

12 

12 

'16 

16 

18 

28 

30 

36 

43 

48 

50 

55 

Page 

FIGURE 1. Map showing location of Colorado Plateau region_ 3 

2. East-west cross s·ection across the Colorado Plateau region, 

illustrating typical facies and- member relationships in 

the Moenkopi Formation ---------------------------------------------------------- 8 

3-5. Probability graphs of the log distributions of: 

3. Ca, Fe, Mg, Ti, Ba, and Mn____________________________________________ 19 

4. Sr, Zr, V, Cr, Cu, and Cu(A)__________________________________________ 20 

5. Y, Pb, Ni, Co, Ag(A), and Hg(A)______________________________ 21 

6. Probability graph of the highly truncated log distributions 

of Be and Au (A) _______ _ _________ ----------------------------------------- 22 

7-9. Graphs showing: 

7. Mean abundance of 20 metals in the Moenkopi Formation ---------------------------------------------------------------------------- 23 

8. Comparison of metal content of some members with 

average metal content of the entire formation______ 25 

9. Comparison of metal content of rocks from different 

facies with average metal content of the entire 

formation ------------------------------------------------------------------------ 29 

III 
IV CONTENTS 

Page 

FIGURE 10. Diagrammatic illustration of significant positive associations 

of metals in the Moenkopi Formation____________________________________ 35 

11. Graph showing comparison of metal content of groups of 

samples having different textures with average metal 

content of the entire formation______________________________________________ 38 

12. Graph showing comparison of metal content of four metalenriched mudstones with average metal content of six 

siltstones -------------------------------------------------------------------------------------- 44 

13. Map showing sample localities having the largest average 

number of high metal values per sample______________________________ 49 

TABLES 

TABLE 1. Generalized chart showing nomenclature of the Moenkopi 

Formation and lithologically related strata in different 

Page 

parts of the Colorado Plateau region____________________________________ 5 

2. The locations, names, and lithologic characteristics of the 

members of the Moenkopi Formation and of lithologically 

related formations ---------------------------------------------------------------------- 6 

3. Summary of higher-than-average amounts of rock components contributed to the Moenkopi Formation by the four 

general source areas, and the interpreted source terranes 

in order of influence on the derived sediments______________________ 12 

4. Index of sample localities, number of samples, and units 

sampled in the Moenkopi Formation and lithologically related strata ------------------------------------------------------------------------------------ 13 

5. Metals looked for, lower detection limits, and percent of 

samples for which numerical values were obtained____________ 17 

6. Selected measures of central tendency and dispersion computed for the log distributions of the 20 metals used in the 

Moenkopi study ---------------------------------------------------------------------------- 22 

7. Sen sings of comparisons of metal values in the different 

groups of samples with the formation geometric means as 

illustrated in figures 8 and 9---------------------------------------------------- 30 

8. Non parametric association coefficients measuring relative correlation between each possible pair of metals________________________ 32 

9. Metal content of randomly selected samples of very coarse, 

coarse, medium, fine, and very fine grained sandstones from 

the Moenkopi Formation ------------------------------------------------------------ 37 

10. Metal content of randomly selected samples of siltstones, 

claystones, and calcareous siltstones, limestones, and dolomites from the Moenkopi Formation ------------------------------------ 41 

11. Metal content of Moenkopi Formation mudstone samples collected from rocks underlying uranium deposits in the 

Chinle Formation ------------------------------------------------------------------------ 43 

12. Distribution by locality of the 32 highest values for each of 

the 20 metals used in the present study, and additional 

valid values available for La, Mo, Nb, Sn, and Zn________________ 45 

13. Localities that contain the 16 highest values per sample, and 

16 highest secondary metals ratios ------------------------------------------ 48 
GEOCHEMIC~AL DISTRIBUTION OF 

SOME MET ALLS IN THE MOENKOPI 

FORMATION .AND RELATED STRATA, 

COLORADO PLATEAU REGION 

By ROBERT A. CADIGAN 

ABS'l'RACT 

Major factors that affect the metal content of rocks constituting the 

Triassic(?) and Lower and Middle(?) Triassic Moenkopi Formation and 

lithologically related Permian and Triassic strata in the Colorado Plateau 

region are sediment source, texture, and nearness to channels of movement 

of mineralizing solutions. Significant positive and negative coefficients of 

association show that the primary relationship that controls the abundance 

of the different groups of metals is the proportion of marine source components and interstitial calcareous cement to detritus from terrestrial source 

areas. 

The Moenkopi is a typical red-bed formation and forms the basal unit of 

the Triassic. It is unconformable with underlying Permian formations and 

with the overlying Chinle FoJrmation. A geochemical study of the occurrences 

of Ca, Fe, Mg, Ti, Ba, Mn, S:r, Zr, V, Cr, Cu, Y, Pb, Ni, Ag, Hg, Au, and Be 

in the Moenkopi suggests that average metal content varies significantly 

among its stratigraphic members. Ti, V, Cr, Y, Ni, and Au vary in amount 

inversely with grain size; Ba varies in amount directly with grain size. 

Rocks from marine or marg]inal marine environments are very high in Ca, 

Sr, and Mg, and very low in .Ba, Zr, Ti, V, Ni, Fe, Cr, Mn, and Co. Published 

reports of metal content of siltstone and sandstone formations in general 

indicate that, in comparison, the Moenkopi is deficient in average content 

of most metals but is richer in Cr, Co, and Au. 

The metals Fe, V, Cu, Co, Ti, Cr, Y, and Ni have a highly significant 

degree of positive mutual as:;ociation; Mg, Sr, Pb, Hg, and Ca do not have 

significant positive associations with specific metals. The highly significant 

negative associations are Ca with Ba, Ti, Cr, and Ni; Ag with Ba, Zr, and 

Pb; Hg withY, Pb, and Ni; and Sr with Zr. 

In the Moenkopi Formation, metals that occur chiefly with the heavy 

mineral fraction of detritus from terrestrial sources are Fe, Ti, Mn, Zr, V, 

Cr, Cu, Y, Ni, Au, and Be. Metals that occur chiefly in marine carbonate 

rocks and siltstones and marginal marine evaporites are Ca and Hg. Metals 

that occur in different modes and in significant proportions in both marine 

and terrestrial sediments are Mg, Sr, and Pb. Ba occurs almost exclusively 

in terrestrial sedimentary rocks in an interstitial cement, barite, which 

competes with and apparently replaces the Ca-bearing cement, calcite. 

1 
2 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

Gold was detected in one-third of the samples studied. Highest average 

gold content (0.09 parts per million) is in the enriched mudstones at the 

top of the formation. Highest proportions of samples that contain detectable 

gold occur in the north-central and northeastern parts of the Colorado 

Plateau region. Lowest proportions are in the salt anticline area of southeastern Utah and southwestern Colorado. 

Mudstones at the Chinle-Moenkopi contact are, in many localities, highly 

enriched in Cu, Y, Be, Sr, Ni, Co, V, Ti, Fe, Pb, and Au. The enriched mudstones commonly occur below known uranium ore deposits in the Chinle 

Formation, suggesting that in areas of unknown uranium ore potential, 

Moenkopi mudstones at the upper contact may prove useful in geochemical 

prospecting. 

Sixteen areas of anomalously high metal values were delineated on the 

basis of the average number of high (upper 10 percent) metal values per 

sample. These areas are recommended for further study or exploration. 

INTRODUCTION 

Metal content varies within the Triassic Moenkopi Formation 

and related strata in the Colorado Plateau region in response to 

many factors. These factors are sedimentary texture, original mineral composition including both detritus and cements, sources of 

sediment, nearness to zones of introduced minerals, diagenesis, 

and tectonic and geographic environments of erosion, transportation, and deposition. The Moenkopi, a typical red-bed formation 

whose common facies is a relatively well sorted coarse siltstone 

interbedded with very fine grained sandstone, is unique in the 

sense that it is composed of strata whose environments of deposition ranged from continental alluvial to marine (including that 

of evaporites) and it contains more than average trace amounts 

of gold. 

PURPOSE AND SCOPE OF INVESTIGATION 

The investigation is part of a study of the distribution of trace 

metals in sedimentary rock formations of the Colorado Plateau. 

Background values for 20 metals (counting spectrographic and 

atomic-absorption Cu determinations as two different metals) 

were determined for the Moenkopi as a whole, for individual 

members of the formation, for lithologically related Permian and 

Triassic strata, for certain textural and compositional rock types, 

and for rocks close to known stratified sandstone uranium ore 

deposits. Metal geochemical associations were assigned on the 

basis of statistically significant covariation, and geologic interpretations of the covariation were made in terms of source and mode 

of occurrence. Areas of anomalously high metal values were delineated and recommended for further study or exploration. 
INTRODUCTION 3 

GEOGRAPHIC AND GEOLOGIC SETTING 

The Colorado Plateau region comprises western Colorado, the 

northwest quarter of New Mexico, and most of the east half of 

Utah and north half of Arizona (fig. 1). 

FIGURE 1.-Location of Colorado Plateau region (shaded). 

Rocks exposed in the Colorado Plateau region range in age from 

Precambrian to Holocene. Newman (1962, figs. 42-68) showed 

isopach and outcrop maps of many stratigraphic units ranging 

in age from the Precambrian through the Tertiary. Rocks of 
4 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

Mesozoic age, the most widely exposed rocks in the Plateau region, 

are dominantly terrestrial quartzitic-feldspathic-tuffaceous clastic 

rocks interlayered with minor marginal marine and marine rocks. 

In four-fifths of the region, the sedimentary beds are flat lying 

or gently warped. The dominant structures are salt-cored anticlines, sharp monoclinal folds, and structures formed by laccoliths, 

volcanic flows, and plugs. 

The arid climate and resulting lack of vegetation yield excellent 

rock exposures in the steep-walled canyons or wide valleys of the 

major streams and in the slopes of the valleys, washes, canyons, 

and arroyos of the minor and intermittent streams. 

PREVIOUS WORK 

The distribution of elements in Colorado Plateau rocks was 

studied by Shoemaker, Miesch, Newman, and Riley (1959) with 

special emphasis on the contained uranium deposits. That study 

resulted from the intense economic and academic interest in 

uranium occurrences during the 1950's and the ready availability 

of much geochemical data. Additional results were reported by 

Newman (1962) and Miesch (1963) and geochemical relationships 

of copper, vanadium, and uranium in uranium deposits and their 

host rocks were summarized by Fischer and Stewart (1961). 

ACKNOWLEDGMENTS 

Most of the rock samples used in the investigation were collected 

by J. H. Stewart, F. G. Poole, and me. Additional samples were 

supplied by W. L. Newman, E. M. Shoemaker, and others. 

"Wet" analyses for gold, silver, copper, and mercury were done 

under the supervision of G. H. VanSickle. Silver and copper 

analyses were done by A. J. Toevs and Lucy Dickson. Mercury 

analyses were done by W. W. Janes. Six-step spectrographic 

analyses for 32 metals were done by J. L. Finley. Mrs. Laurette 

Bates assisted with data cards, tables, and illustrations. 

STRATIGRAPHY 

In the Colorado Plateau region the Moenkopi Formation of 

Triassic ( ?) and Early and Middle ( ?) Triassic age is the basal 

Triassic formation. It overlies unconformably several Permian formations and is overlain unconformably by the Chinle Formation 

of Late Triassic age. The nomenclature and regional relationships 

of the Moenkopi are summarized in table 1. Detailed stratigraphic 

relations of the Moenkopi Formation have been reported by Stewart, Poole, and Wilson (1971). 
TABLE !.-Generalized chart showing nomenclature of the Moenkopi Formation and lithologically related strata in different 

parts of the Colorado Plateau region 

Northern Arizona, eastern Arizona, 

southern Utah, western Utah 

San Rafael Swell,l 

east-central Utah 

-I 

.8 

rJ). 

rJ). 

tiS 

-~ 

E-4 

~ 

tiS ·s 

~ 

Q) 

~ 

Chinle Formation Chinle Formation 

Moenkopi Formation Moenkopi Formation 

(2) (2) ------------------------------------------ ------------------------------------------

Kaibab Limestone Coconino Sandstone 

1 Use of Coconino in San Rafael Swell uncertam. 

2 No deposition in this area. 

Northern Utah to northwestern Colorado 

Chinle Formation 

Mahogany, 1-~ §I Po..~ 

Thaynes, 0~ 

,.!1:lt:IS State 

and ~ s Bridge Q)~ Woodside oo FormaFormations ~~ tion 

Park City Weber Formation Sandstone 

Southwestern Colorado, 

southeastern Utah 

Chinle Formation 

Moenkopi Formation 

(2) ------------------------------------· 

Cutler Formation 

I 

Western 

New Mexico 

Chinle Formation 

Moenkopi Formation 

(!!) 

-----·----------------------------------

San Andres 

Limestone 

00. 

~ 

~ 

> 

~ 

-

C) 

~ 

> 

1-d 

::r: 

1-<! 

c:Jl 
6 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

The Moenkopi Formation is a typical red-bed unit such as those 

that characterize upper Paleozoic and lower and middle Mesozoic 

strata in the Colorado Plateau region. The Moenkopi is exposed in 

many localities throughout the west two-thirds of the region. It 

ranges in thickness from at least 2,000 feet on the west border of 

the region to less than 10 feet in the eastern part, where it is barely 

recognizable as Moenkopi. The basal Triassic formations, including the Moenkopi, are shown on the isopach map by McKee and 

others (1959, pl. 9, fig. 1). 

The Moenkopi consists of numerous members, none of which 

extends throughout the entire depositional area of the formation. 

The names, locations, and lithologic characteristics of the memTABLE 2.-The locations, names, and lithologic characteristics of the meutbers 

of the Moenkopi Formation and of lithologically related formations 

Location 

Southwestern Utah, northwester Arizona, and southeastern Nevada. 

North-central and eastern Arizona. 

Name Lithologic characteristics 

Members of the Moenkopi Formation 

Upper red------------------------------- Red siltstone and sandstone. Shnabkaib -------------------------------White gypsum, gray limestone (marine), red siltstone, and sandstone. Middle red __ --------------------------- Red siltstone and sandstone. Virgin Limestone __________________ Gray limestone and siltstone (marine). 

Lower red -------------------------------Red siltstone and sandstone. Timpoweap ___________________ Red siltstone, gray limestone (marine) 

and light-gray chert pebble conglomer- ate. 

Holbrook--------------------------------- Reddish-brown sandstone and siltstone. Moqui ____ --------------------------------Reddish-brown siltstone and sandstone, minor white gypsum. Wupatki ________________________________ Reddish-brown siltstone and sandstone, 

lower "massive" sandstone bed. Western New Mexico _________ Undifferentiated ___________________ Red siltstone and sandstone. Southeastern Utah _______________ Cliff-forming __________________________ Reddish-brown and grayish-red siltstone 

Eastern Utah, western Colorado (salt anticline area). 

and sandstone. Upper slope-forming __________ Grayish-red and reddish-brown siltstone 

and sandstone. Ledge-forming _____________________ Red siltstone and sandstone. Sin bad Limestone ________________ Yellowish-gray limestone (marine). Lower slope-forming ___________ Grayish-red, yellowish-gray, and lightgreenish-gray siltstone and sandstone. 

Hoskinnini ------------------------------Reddish-brown siltstone and sandstone containing fine to coarse sand grains. Pariott ----------------------- _____________ Red-brown, purplish-brown, orange, and red sandstone, siltstone, and clayey mudstone. Sewemup _________________________________ Reddish-brown and grayish-red siltstone 

Ali Baba __ _ and sandstone. _______________ Red conglomeratic sandstone and red 

sandstone and siltstone. Tenderfoot ____________________________ Reddish-brown siltstone and sandstone, 

local red arkosic conglomerate, white gypsum. Northern Utah and Utah- Undifferentiated _____________________ Red siltstone and sandstone. 

Colorado border area. 

Lithologically related formations 

Northeastern Utah Mahogany ________________________________ Red siltstone and sandstone. 

(west Uinta Mountains). Thaynes----------------------------------- Brownish-gray limestone (marine). Woodside ---------------------------------Red siltstone and sandstone. Northwestern Colorado _______ State Bridge: 

Upper member ___________________ Red siltstone and sandstone. 

South Canyon Creek Limestone. Member,l Lower member l ______________ Red siltstone and sandstone. 

1 Considered to be of Permian age and therefore older than Moenkopi strata in the Colorado Plateau region. The upper member of the State Bridge Formation is considered to be Triassic and Permian age. 
STRATIGRAPHY 7 

bers are outlined in table 2. Rocks described as siltstone and sandstone, the dominant lithology of the formation, are generally thin .. 

bedded poorly resistant interbedded coarse siltstone and very fine 

grained sandstone. Forntations in northeastern Utah (west Uinta 

Mountains) and northwestern Colorado that are similar to and 

considered to be, at least in part, stratigraphically equivalent to 

the Moenkopi Formation are also shown in table 2. They are certainly the same lithologically. 

The sediments may be divided into three general facies: (1) a 

marginal marine and alluvial red and gray coarse siltstone and 

very fine to fine-grained sandstone facies, which includes all undifferentiated red beds, all the informal red and gray members, the 

Moqui, Wupatki, Pariott, Sewemup, and Ali Baba Members of 

the Moenkopi, the upper and lower members of the State Bridge 

Formation, and the Mahogany and Woodside Formations; (2) 

an alluvial relatively coarse sandstone facies, represented by parts 

of the Tenderfoot, Holbrook, and Hoskinnini Members of the 

Moenkopi; and (3) a lin1estone and evaporite facies, composed of 

the marine Virgin and Sinbad Limestone Members, the marginal 

marine Timpoweap (lirnestone and conglomerate) Member, the 

marine to marginal marine Shnabkaib (gypsum and limestone) 

Member, the marine South Canyon Creek Member of the State 

Bridge Formation (limestone), the scattered gypsum beds (mostly 

in the basal strata) of the Moenkopi, and the marine Thaynes 

(limestone) Formation. 

Typical facies and mem.ber relations in the Moenkopi Formation 

are illustrated in figure 2, which is based on four stratigraphic 

sections measured and described by Stewart, Poole, and Wilson 

(1971) : the Kanarraville, Capitol Wash, and North Sixshooter 

Peak sections in Utah, and the Paradox Valley section in Colorado. 

Marine and marginal marine facies in the form of limestone and 

gypsum beds are common on the west side of the area of deposition, but these thin and disappear to the east. Coarse chert 

pebbles probably deriv,ed from west-central Arizona form the 

limestone-cemented conglomerate of the Timpoweap Member in 

the west. 

The siltstone and sandstone facies is dominant and is characterized by an overall redd:[sh-brown color. The strata of this facies 

are typically flat bedded with some small-scale crossbedding, and 

they weather to slopes covered with platy fragments. Ripplemarked bedding surfaees are common. Strata associated with 

gypsum commonly exhibit contorted bedding. 
emoer 

~lesection 

Upper red 

Upper slope-forming 

Shnabkaib 

Middle red 

Virgin Limestone 

Lower red 

Timpoweap 

0 ~OMILES 

EXPLANATION 

~ . 

. Coarse-grained siltstone and very fine grained 

sandstone 

Sandstone, 

~ 

~ 

siltstone, 

and conglomerate 

Gypsum 

~ interbedded 

with limestone 

Limestone 

~ 

500 

Conglomerate 

~ in limestone 1000 

Contact 

Dashed where approximately located owing 

to loss of distinguishing characteristics 

between members 

1500 

2000 

0 20 40 60 80 MILES 

------~----~------~_____j 

VERTICAL EXAGGERATION X 169 

FIGURE 2.-East-west cross section across the Colorado Plateau region, illustrating typical facies and member relationships in the 

Moenkopi Formation. Data from Stewart, Poole, and Wilson (1971). 

00 

0 

t:z:j 

0 

0 

~ 

t:z:j 

~ 1-1 

0 

> t'-4 

t:) 

1-1 

00 

1-3 

~ 1-1 

b:1 

~ 

1-3 

1-1 

0 

~z 

~ t:z:j 

1-3 

> t'-4 

.rn 

~ 

0 

t:z:j 

z 

~ 

0 

1-d 

1-1 
GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 9 

PETROLOGY 

OBSERVATIONS 

The rocks of the Moenkopi and contiguous formations of similar 

lithology are classified on the basis of present mineral composition 

as varieties of orthoquartzite, arkose, graywacke, limestone, dolomite, and gypsum. The major detrital components are grains of 

quartz, chert, chalcedony, albite, oligoclase, orthoclase, and sanidine( ?) , and fragments of quartzite, probable silicified limestone, granite, altered silicified devitrified tuff, and felsite. The 

most abundant accessory minerals are flakes of biotite, muscovite, 

and chlorite, and grains of zircon, tourmaline, garnet, staurolite, 

rutile, apatite, magnetite, ilmenite, leucoxene, and altered amphibole. 

Illite is the dominant clay mineral; kaolinite and chlorite are 

generally minor, but each is dominant in some strata. Combinations of illite, montmorillonite, and chlorite-illite with mixedlayer montmorillonite also occur. Some of the clay minerals were 

derived from the source areas, and some were derived by alteration from other detrital :minerals. All clay minerals observed were 

recrystallized during diagenesis. 

The major nondetrital mineral components present as cements 

are calcite, dolomite, gypsum, barite, authigenic quartz as overgrowths on quartz grains, anatase, and authigenic orthoclase as 

overgrowths on detrital particles of orthoclase. Iron oxides, as 

finely crystalline alteration products either alone or mixed with 

clay, also act as cement::;. 

Diagenesis altered the composition of the original sediment. 

Most affected were feldspars, biotite and other heavy minerals, 

volcanic ash, tuff, and pumice fragments, and detrital clays. Feldspars show evidence of replacement by carbonates and clay minerals; biotite was altered to chlorite, chloritic clay, and iron oxides; 

other original detrital rnafic minerals, such as pyroxenes, amphiboles, and ilmenite, were mostly altered to metallic oxides and 

hydrous aluminum silicates (clay minerals); volcanic ash was 

altered to montmorillonite, much of which in turn was then altered 

to chloritic and illitic clays; and tuff and pumice fragments were 

devitrified and then either silicified or altered to clay minerals. Most 

siliceous orthoquartzite and chloritic graywacke in the Moenkopi 

are more the products of diagenesis than of tectonic environment. 

The petrology of the Moenkopi and lithologically related strata is 

discussed in detail in another report (Cadigan, 1971). 

Sandstones of the Moenkopi and related strata are generally 

very fine grained and rnoderately sorted with slightly positively 
10 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

skewed and moderately peaked grain-size distributions. 1 The 

siltstones are generally coarse grained and are moderately to 

poorly sorted with slightly positively skewed and moderately 

peaked grain-size distributions. The claystones are coarse grained 

and poorly sorted, with negatively skewed and flattened (negatively peaked) grain-size distributions. 

Source areas for the Moenkopi and related sediments included the 

Uncompahgre highland area of southwestern and west-central 

Colorado (Baker and others, 1933, p. 975) and a continuous positive area that is now the Basin and Range province of southern 

Arizona and southern New Mexico (McKee and others, 1959, pl. 

9, fig. 1). Streams transported sediment from these sources 

(McKee, 1954) across the northwestward-sloping area of deposition and on toward the marginal marine and marine environments 

to the west. 

Local feldspar-rich sediments suggest the presence of a major 

source of feldspar in the Uncompahgre highland, and minor 

sources of feldspar in southeastern Arizona and southwestern 

New Mexico. The major source of silicified-rock fragments appears 

to have been in southern New Mexico, with a minor source in 

southern Arizona. A major source of biotite and chlorite appears 

to have been the Uncompahgre highland in western Colorado. 

INTERPRETATIONS 

The Moenkopi Formation shows regional variations in composition, grain size, and thickness that are significant both statistically 

and geologically. Proportions of certain minerals show individual 

regional gradients with highs near related source areas; measures 

of grain-size distribution yield regional trends related to direction 

of sediment movement; and thickness variations yield trends 

related to slope of the depositional surface. 

Regional trends of grain-size distribution measures show that 

from southeast to northwest, the grain size, skewness, and peakedness decrease and the degree of sorting increases; these trends 

suggest that the direction of sediment movement was northwestward. 

The Moenkopi Formation was deposited on a partly eroded plain 

1 For the convenience of the reader, the grain-size distribution measures are briefly reviewed: the range of particle sizes in a sediment forms what is called a size distribution. Good sorting indicates a small range of particle sizes; poor sorting indicates the opposite. If the sediment is uniformly sorted, the particle-size distribution is called normal. A lack of sorting uniformity results in a size distribution that is nonsymmetrical (skewed and (or) peaked). Positive skewness indicates a disproportionately large range of finer sizes compared with the range of coarser sizes; negative skewness indicates the opposite. Positive peakedness indicates a dis- proportionately large amount of particles in the middle of the size range; negative peakedness indicates a disproportionately large amount of particles in both the fine and the coarse ends of the size range. 
PETROLOGY 11 

which subsided at a low to moderate rate. The source areas underwent tectonic uplift at a low to very low rate. Sediments that 

were eroded from the weathered sources were mostly silt, clay, 

and very fine sand. Erosion and deposition took place in a warm 

arid climate that produced oxidized sediments and evaporite 

basins. In the present study, interpretations of tectonic uplift and 

subsidence were made largely according to the system described in 

a previous report (Cadigan, 1961) and especially from the relationships apparent in figure 11 of that report. 

Decreases in the rate of source-area uplift at times reduced the 

supply of detritus, and this reduction, combined with the effects of 

a continuous rate of subsidence of the area of deposition, permitted 

invasion into eastern alluvial areas by marine environments from 

the west. Toward the end of Moenkopi deposition, the rate of 

source-area uplift slowly increased, and the resulting increased 

flow of detritus caused the retreat of the marine environment 

westward beyond the borders of the Colorado Plateau region. 

The energy level 2 in the environment of deposition of the 

Moenkopi generally was low, but locally it varied from low to high. 

Conglomerates present in the basal strata-the Tenderfoot, Ali 

Baba, and Timpoweap Members as well as the higher Holbrook 

Member-testify to the occasional presence of high energy levels in 

the marginal parts of the area of deposition adjacent to source 

areas. 

All source areas produced detritus containing quartz, feldspar, 

mica, volcanic igneous, metamorphic, and sedimentary rock fragments, but the proportions of these types of fragments varied 

greatly from one area to another. From evidence supplied by 

trend-surface analyses, certain terranes are proposed as being 

dominant in certain souJrce areas, as listed in table 3. The weathering in the source areas prior to erosion presumably altered the 

surface of the source roeks. Detritus from the weathered surfaces 

was deposited and subj~!cted to further change during diagenesis. 

The terranes listed in table 3 are suggested as the source rocks of 

the Moenkopi sediments with the realization that other rocks, for 

example sodic andesite (in the southwestern source), also may 

have been present. As a result of the combined effects of weathering and diagenesis, andesite might yield few identifying stable 

detrital minerals. 

The four interpreted source areas are the Uncompahgre highland in southwestern Colorado; a southwestern source, part of the 

2 Energy level refers to the rate at which geologic processes operate in a system of erosion, 

transportation, and deposition. Thi:; is an extension of the "energy concept" of Gilbert (1914). 
12 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

Basin and Range province of New Mexico; a southern source, part 

of the Basin and Range province of southwestern New Mexico and 

southeastern Arizona; and a southeastern source in south-central 

Arizona. The last three were probably more or less physically 

continuous areas. 

TABLE 3.-Summary of higher-than-average amounts of 'tack components 

contributed to the Moenkopi Formation by the four gene'ral sowrce areas, 

and the interpreted sowtce terranes in O'rder of influence on the derived 

sedi'rnents 

[X indicates higher-than-average amount of rock components contributed to the Moenkopi Formation] 

Source areas 

Quartz ___________________ _ 

All rock fragments Feldspar ________________ _ Mica flakes ____________ _ 

Volcanic detritus __ _ Heavy minerals ____ _ 

Siliceous rock 

fragments. 

Uncompahgre 

highland 

X 

X 

X 

X 

X 

X 

Southwestern Southern 

Rock component 

X 

X 

X 

X 

X 

X 

X 

Terrane 

Southeastern 

X 

X 

X 

Dominant____________ Granite _____________ Siliceous Quartzite _______ Metamorphic 

sedimentary rocks. 

rocks. 

Intermediate______ Metamorphic None evident ______ None Siliceous 

rocks. evident. sedimentary 

rocks. 

Minor_ ________________ Arkose; Granite; 

andesite? 

Rhyolite _________ None evident. 

rhyolite. 

GEOCHEMICAL STUDIES 

SAMPLING AND ANALYTICAL METHODS 

The rock samples used for this study were selected as representative of the outcrops from which they were taken. Weathered 

surfaces were removed and a 2- to 3-pound sample was taken from 

an area less than 1 foot square. In thick stratigraphic sections, 

samples were selected at predetermined intervals along a line 

perpendicular to the outcrop of the beds. In well-exposed sections 

consisting of different members, at least three samples were taken 

from each member. Some samples were taken in the Moenkopi near 

uranium ore deposits in the overlying Chinle Formation. A total 

of 323 samples was collected from 76 localities (table 4). The 

number of samples collected at each locality ranged from one to 18. 

To eliminate clusters of data points, some closely spaced localities 

were combined in the previously published petrology study, reduc-
GE:OCHEMICAL STUDIES 13 

ing the total sample localities to 65. (See sample locality map, pl. 1, 

in Cadigan, 1971.) 

TABLE 4.-lndex of smnple localities, nwnbe1· of samples, and units sampled 

in the Moenkopi F'ormation and lithologically related strata 

[Number refers to locality number on published map (Cadigan, 1971, pl. 1). All members sampled are of Moenkopi and related strata. Those preceded by asterisk (*) are State Bridge Forma- tion] 

No. 

1 

5 

9 

10 

12 

15 

60 

70 

81 

210 

211 

400 

401 

3 

4 

8 

15 

18 

139 

186 

188 

189 

400 

1 

3 

16 

20 

Sample locality Number of Members sampled Area Long W. Lat N. samples 

Black Creek _____________________________________ _ 

Hunters Point _ _ ____________________ _ 

St. Johns ''A''---------- -------------------------

Black Point -------------------

Sunset Mountain Big Canyon_ 

Holbrook 

Winslow _____________________________ _ 

Shinumo Altar---------------------------------

14 miles west of Navajo Bridge ___ _ 

Kato Sells 2 ---------------- Hoskinnini Mesa _ 

Nokai Dome 

Sheephorn Creek ------------------------------

South Canyon Creek _____________ _ 

Gateway (The Palisade) ____ _ 

Paradox Valley ______ --------------------------

Meeker 

Gore Pass__ ----------------------------------------- Main Elk Creek __ ----------------------------- Skull Creek ----------------------------------------- Deer Creek ___________ ------------------------------ Sinbad Valley _ ----------------- _ 

Horse Spring Valley _____________________ _ 

Cha vez-Prewitt "A" ________________________ _ Fort Wingate "A" ___________________________ _ Riley __________________ _ 

Mesa Gallina _ -------------- ____ _ 

Muddy River--------------- --------------------

Straight Wash----------------------- ________ _ 

Temple Mountain _____________________________ _ 

Arizona 

109.23° 

109.13° 

109.37° 

111.27° 

110.90° 

111.55° 

110.16° 

110.83° 

111.72° 

111.82° 

109.86° 

110.40° 

110.40° 

Colorado 

106.52° 

107.43° 

108.99° 

108.85° 

107 .so· 

106.58° 

107.59° 

108.68° 

106.54 ° 108.97° 

Nevada 

35.33° 

35.60° 

34.43° 

35.73° 

34.87° 

36.15° 

34.88° 

35.08° 

36.44 ° 

36.70° 

36.93° 

36.85° 

36.93° 

39.91° 

39.97° 

40.16° 

39.63° 

40.33° 

40.20° 

38.52° 

New Mexico 

108.06° 35.32° 108.57° 35.48° 107.21° 34.38 ° 107.24° 34.67° 

Utah 

110.52.0 38.78 ° 

110.67° 38.68° 

3 

2 

2 

3 

1 

2 

3 

2 

3 

2 

1 

1 

4 

2 

2 

2 

2 

1 

2 

2 

1 

1 

1 

1 

1 

1 

2. 

4 

1 

14 

3 

3 

1 

1 

1 

2 

1 

1 

3 

6 

7 

2 

1 

3 

2 

3 

3 

Undifferentiated. Do. 

Do. Holbrook. 

Moqui. 

Wupatki. 

Holbrook. 

Moqui. 

Wupatki. 

Holbrook. 

Moqui. 

Wupatki. 

Holbrook. 

Undifferentiated. 

Lower massive sandstone. Upper red. Shnabkaib. 

Lower red. Upper slope-forming. Hoskinnini. 

Upper slope-forming. Do. 

*Upper. 

*South Canyon Creek. *Upper. 

*Lower 

Ali Baba. Tenderfoot. 

Sewemup. 

Ali Baba. Tenderfoot. 

*Upper 

*Lower. 

*Undifferentiated. 

*Upper. 

Undifferentiated. *Do. Pari ott. Sewemup. 

Ali Baba. Tenderfoot. 

Upper red. 

Middle red. 

U ndifferen tia ted. Do. 

Do. 

Do. 

Cliff-forming. 

Upper slope-forming. 

Ledge-forming. 

Lower slope-forming. 

Upper slope-forming. Lower slope-forming. 

Upper slope-forming. 

Ledge-forming. 

Sin bad. 

9 Poison Spring Wash 

1 

1 

1 

1 

1 

1 

1 

2 

1 

3 

1 

2 

2 

Lower slope-forming. 

Upper slope-forming. 

Ledge-forming. 

Lower slope-forming. 

(Buckacre Point). 
14 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

TABLE 4.-Index of sample localities, number of samples, and units sampled 

in the Moenkopi Formation and lithologically related strata-Continued 

No. 

10 

11 

14 

18 

22 

25 

26 

27 

28 

29 

30 

32 

33 

34 

35 

36 

38 

41 

43 

45 

47 

49 

64 

160 

173 

200 

248 

286 

300 

304 

305 

307 

309 

310 

Sample locality Number 

of Members sampled 

Area Long W. Lat N. samples 

Horse Canyon ( Lampstand 

Draw, Long Canyon). 

Muley Twist ------------------ __ _ 

Silver Falls ---------------------- ____ ---------· 

Richardson Amphitheater _______________ _ 

Kanarraville "A"--------------------

Bears Ears _____________ ---------------------------· 

Bridger Jack Mesa--------------------------- Comb Wash ---------------------------------------- Cottonwood Creek. ____________________________ _ 

Hite------------------------------------------------------· 

Jacobs Chair--------------------------- __________ _ 

Lockhart Canyon ______ -----------------------

Milk Ranch Point----------------------------

Monitor Butte ------------------------------------

North Sixshooter Peak--------------------

Poncho House._. _________________________________ _ 

Steer Mesa------------------------------------------

Vernal.-----------------------------·--------------------

Chimney Rock-----------------------------------

Leeds ____________________________________________________ _ 

St. George "A"----------------------------------· 

Clay Hills Pass ---------------------------------· 

Pleasant Creek 

(Miners Mountain). 

Torrey _________________________________________________ _ 

Clay Gulch ------------------------------------------

Happy Jack area ------------------------------· Clay Hills Crossing -------------------------- Cedar City----------------------------------------

~r:gi~~~--~~~~~-~~~~~~~~~~~~~~~~~~~~--~~--~~~~~~ The Peaks __________________________________________ _ 

Farm Creek _______ --------------------------------

Deer Flat (Hide-out mine) ____________ _ Mineral Canyon ________________________________ . 

Utah-Continued 

111.03° 

111.15° 

109.32° 

113.20° 

109.87° 

109.68° 

109.65° 

109.68° 

110.43° 

110.23° 

109.68° 

109.68° 

110.43° 

109.66° 

109.75° 

11o.ooo 

109.48° 

111.30° 

113.35° 

113.67° 

110.31° 

111.20° 

111.39° 

110.40° 

110.27° 

110.40° 

113.07° 

110.53° 

113.12° 

111.17° 

110.72° 

110.02° 

109.92° 

37.83 ° 

37.74° 

38.78° 

37.50° 

37.64° 

37.97° 

37.32° 

37.77° 

37.78° 

37.73° 

38.35° 

37.61° 

37.23° 

38.15° 

37.12° 

38.42° 

40.60° 

38.33° 

37.20° 

37.05° 

37.44° 

38.17° 

38.35° 

37.34° 

37.74° 

37.30° 

37.72° 

39.05° 

37.25° 

37.87° 

40.38° 

37.66° 

38.55° 

1 

2 

1 

1 

1 

2 

2 

1 

4 

3 

1 

2 

2 

2 

1 

1 

2 

2 

4 

3 

2 

4 

6 

2 

1 

2 

3 

1 

1 

1 

3 

3 

3 

1 

1 

1 

1 

2 

1 

1 

2 

4 

2 

1 

1 

2 

1 

2. 

3 

5 

2 

2 

6 

3 

1 

1 

4 

2 

3 

4 

1 

1 

1 

2 

2 

3 

1 

2 

1 

1 

1 

1 

1 

1 

4 

4 

3 

Upper slope-forming. 

Ledge-forming. 

Sin bad. Lower slope-forming. 

Cliff-forming. 

Upper slope-forming. 

Ledge-forming. 

Cliff-forming. 

Upper slope-forming. 

Ledge-forming. 

Sewemup. 

Ali Baba. 

Tenderfoot. 

Upper red. Lower red. 

Timpoweap. 

Ledge-forming. 

Lower slope-forming. 

Hoskinnini. Do. 

Do. 

Do. Upper slope-forming. 

Ledge-forming. 

Upper slope-forming. 

Ledge-forming. 

Hoskinnini. 

Upper slope-forming. 

Ledge-forming. 

Lower slope-forming. 

Hoskinnini. Do. Ledge-forming. 

Hoskinnini. 

Upper slope-forming. 

Ledge-forming. 

Lower slope-forming. 

Hoskinnini. 

Lower slope-forming. 

Hoskinnini. 

Lower slope-forming. 

Hoskinnini. 

Undifferentiated. 

Upper slope-forming. Ledge-forming. 

Sin bad. Lower slope-forming. 

Upper red. Do. Shnabkaib. 

Middle red. 

Virgin. 

Lower red. 

Upper slope-forming. 

Ledge-forming. 

Lower slope-forming. Hoskinnini. 

Upper slope-forming. 

Ledge-forming. 

Sin bad. Lower slope-forming. 

Upper red. 

Ledge-forming. 

Hoskinnini. 

Upper slope-forming. 

Hoskinnini. 

Upper red. 

Upper slope-forming. 

Upper red. 

Cliff-forming. 

Ledge-forming. 

Sin bad. Lower slope-forming. 

Mahogany Formation. 

Thaynes Formation. 

Upper slope-forming. Do. 
GEOCHEMICAL STUDIES 15 

TABLE 4.-Index of sample localities, number of samples, and units sampled 

in the Moenkopi Formation and lithologically related strata-Continued 

Sample locality Number No.----------------------------------- of Members sampled Area Long W. Lat N. samples 

Utah-Continued 

312 3 miles south of Kanab 313 Red House Cliffs 

(Midway section). 

315 Red House Cliffs 

(North section). 

319 Bicknell ___ ____________ _ ___ ------------------------- 323 Oijato Trading Post------------------------- 325 Moab ______________________________________________________ 

326 Junction Butte ----------------------------------- 400 Frey Canyon ______________ ------------------------ 401 Shinarump No. 1 mine ______________________ 

402 Castle Valley ____________ ---------------------------

112.55° 37.00° 110.27° 37.43° 

110.2.'3° 37.45° 

111.53° 38.33° 110.26° 37.05° 109.60° 38.62° 

109.83° 38.33° 110.14 ° 37.63° 109.71° 38.68° 

109.40° 38.66° 

2 Upper red. 1 Upper slope-forming. 1 Ledge-forming. 1 Lower slope-forming. 2 Hoskinnini. 3 Do. 

1 Upper red. 1 Undifferentiated. 1 Pariott. 2 Sewemup. 3 Ali Baba. 2 Tenderfoot. 3 Hoskinnini. 4 Upper slope-forming. 1 Sewemup. 1 Mottled zone. 1 Pariott. 1 Sewemup. 2 Ali Baba. 1 Tenderfoot. 

Chemical analyses were performed using a six-step spectrographic method slightly modified from the three-step technique 

described by Myers, Havens, and Dunton (1961). Smaller quantities of gold and silver can be detected by the atomic-absorption 

methods than by the six-step spectrographic method. Detection 

of copper is about the same with both methods; duplication provided an opportunity to make a statistical comparison between the 

two methods for copper. Analysis for gold was also done using an 

atomic-absorption technique. Silver and copper analyses were 

duplicated with an atomic-absorption technique described by Huffman, Mensik, and Rader (1966) and Huffman (1968). Mercury, 

not included among the elements determined in the six-step 

spectrographic method, was determined utilizing a large-volume 

atomic-absorption technique described by Vaughn (1967). 

Uranium was not sought by chemical analysis because previous 

work with similar samples indicated that detectable amounts of 

uranium were present only in well-mineralized rock, suggesting 

that few if any of the samples in this study would be found to 

contain detectable uranium. All samples, however, were scanned 

with a scintillation counter for evidence of radioactivity above 

background. None was detected. 

Values for copper, silver, gold, and mercury determined by 

atomic absorption are identified in this report by modifying the 

element symbols to Cu (A), Ag (A), Au (A), and Hg (A). Unmodified symbols indicate values determined by spectrographic 

method; for example, Cu, Fe, and Ni. Cu and Cu (A) are treated 

as two different elements throughout the rest of the report. 

Ag(A) values, according to G. H. VanSickle (written and oral 
16 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

communs., 1968), tend to be high when Ca values are high, but 

this seems to be a result of the effect of calcite on the atomicabsorption method used for Ag (A) rather than a valid geochemical correlation. 

ELEMENTS STUDIED 

Table 5 lists the metals looked for in the samples, their lower 

limits of detection, and the percentage of samples for which 

numerical values were obtained for each element. The lower detection limit is the minimum amount of a particular element that can 

be detected with a particular method. The upper detection limit is 

the maximum amount that can be discerned before saturation of 

the discriminating element occurs. Numerical values are those that 

range between (and include) the detection limits. Frequency distributions containing some values that lie outside the detection 

limits are called censored distributions (Cohen, 1959, 1961; 

Miesch, 1967). 

This study is based on determinations of the 20 elements listed 

in the first half of table 5. Distributions of 18 of these elements are 

sufficiently uncensored for purposes of a statistical study. Au (A) 

and Be, despite severe censoring of their distributions, are included in this study because of the current interest in their modes 

of occurrence as well as their economic importance. It is, of course, 

important to emphasize the tentativeness of any conclusions suggested by the Au (A) and Be data calculations. The 16 elements 

listed in the second half of table 5 were not included in the statistical study because of the small percentage of samples from which 

numerical values for these elements were obtained. 

STATISTICAL ANALYSIS 

To utilize as many of the available analytical data as possible, 

values which fell below the lower limits of detection were arbitrarily assigned a value equal to one-half of the lower detection· 

limit value. This was also done to avoid using zero values, which 

are probably incorrect. For example, the lower detection limit of 

yttrium is 10 ppm (parts per million). Thus, values reported as 

less than 10 ppm were assigned a value of 5 ppm. Similarly for 

high determinations, calcium values reported as greater than 10 

percent were arbitrarily assigned the value of 20 percent-twice 

the upper limit of detection. 

Numerical values were transformed to logarithms essentially 

for purposes of calculating statistical measures as discussed in a 

previous report (Cadigan, 1969). The statistical analysis of the 

data is similar to that used by Miesch and Riley (1961) and Miesch 
GEOCHEMICAL STUDIES 17 

TABLE 5.-Metals looked for, lower detection limits, and percent of samples 

for which numerical values were obtained 

[Six-step spectrographic analyses were done by J. L. Finley. Atomic-absorption analyses for 

Cu(A) and AG(A) were done by A. J. Toevs and Lucy Dickson; and atomic-absorption 

analyses for Hg(A), by W. W. Janes] 

Metal 

Symbol 

used in 

report 

Lower Percent of samples 

detection for which 

limit numerical values 

(ppm) were obtained 

Elements used in statistical study because of high percentage of samples for which numerical 

values were obtained 

Calcium 1 

----------------------------------- Ca 50 98 Iron ___________________________________________ Fe 10 100 Magnesium ______________________________ Mg 50 100 Titanium __________________________________ Ti 2 100 Barium ______________________________________ Ba 2 100 

Manganese _______________________________ Mn 1 100 

~f;~6~~~:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~: Sr 5 100 

Zr 10 96 Vanadium _________________________________ v 7 97 

Chromium ________________________________ Cr 1 99 

Copper-------------------------------------- Cu(A) 10 65 

Copper-------------------------------------- Cu 1 99 Yttrium ____________________________________ y 10 74 Lead __________________________________________ Ph 10 83 NickeL _____________________________________ Ni 3 92 

Cobalt__ _____________________________________ Co 3 77 Beryllium _________________________________ Be 1 4 Silver ________________________________________ Ag(A) .2 96 

Mercury------------------------------------ Hg(A) .01 98 

Gold ___________________________________________ Au(A) .02 32 

Elements looked for but not used in statistical study because of small percentage of samples for 

which numerical values were obtained 

Gold___________________________________________ Au 

Silver---------------------------------------- Ag Lanthanum______________________________ La 

Molybdenum____________________________ Mo 

Tungsten__________________________________ W 

Zinc____________________________________________ Zn 

Arsenic_____________________________________ As 

Bismuth____________________________________ Bi 

Cadmium__________________________________ Cd 

Antimony--------------------------------- Sb 

Tin_____________________________________________ Sn 

Tellurium_________________________________ Te 

Tantalum__________________________________ Ta 

Platinum__________________________________ Pt 

Palladium___________________________ _____ Pd 

Niobium___________________________________ Nb 

20 

1 

30 

3 

100 

200 

2,000 

10 

50 

200 

10 

2,000 

200 

50 

2 

3 

0 

1 

5 

2 

0 

1 

0 

0 

0 

0 

1 

0 

0 

0 

0 

1 

1 Six calcium determinations were greater than 10 percent, the upper detection limit. 

(1967). Measures of average concentration are the geometric 

mean (the antilog of the log distribution mean) and the median. 

Analytical data were punched on cards, and computations of 

means, standard deviations, and cumulative frequencies were performed by electronic computer. 
18 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

Some miscellaneous computational tasks were done by direct 

entry into a smaller computer. Logs to the base x (Cadigan, 1969) 

used in the study are derived from the formula 

1 

( 

N ) logto2 logxN = 0.003125 

The following paragraphs discuss statistical properties of the 

element distributions. Readers with no interest in such a discussion may skip to the section entitled "Stratigraphic Comparisons" 

without much loss of continuity. 

A test for normality utilizing chi-square at the 95-percent 

significance level showed that statistical distributions approach 

log normal for 13 of the 20 metals studied and depart significantly 

from log normal for five of the metals (Ni, Sr, Mg, Ba, and Cr). 

Probability graphs of the 18 log distributions are shown in figures 

3, 4, and 5. As is conventional, the divergence from a straight line 

exhibited in the percentiles below 10 and above 90 were discounted 

in the log normality test. Probability graphs of the Au (A) and Be 

are shown in figure 6. Table 6 lists selected measures of central 

tendency and dispersion for the log distributions. 

Figure 7 graphically presents at log scale the relative abundance 

of the 20 metals, the detection limit, the range of geometric mean, 

and the rank of the metals in order of abundance. These average 

values are based on the 323 samples of Moenkopi and were used 

as the standard against which average values of certain stratigraphic units, textural rock types, and compositional rock types 

within the Moenkopi Formation were compared. 

The range-of-mean interval, a graphic indication of relative 

dispersion, is of similar width for most of the 20 metals. This 

reflects the similarity of log standard deviations and standard 

errors of the mean listed in table 6. 

STRATIGRAPHIC COl\fP ARISONS 

Figure 8 illustrates the relative amounts of metal content in 

some members of the Moenkopi Formation compared with the 

abundance of the same 20 metals in the formation as a whole. 

Figure 8, column A, shows the formation averages (geometric 

means) as a graphic standard. From a statistical geochemical 
GEOCHEMICAL STUDIES 19 

Mn 

I 

I 

99 I 

I 

98 I 

I 

95 

90 

c:; 

...J 

< C,.) 

Cl) 80 > 1-

::::i 

ii5 70 < IX) 

0 

0::: 60 

!!; 

1-

z 50 UJ 

C,.) 

0::: 40 UJ 

c.. 

30 

20 

10 

5 

2 

0.5 

20 21 22 23 24 25 26 

LOG BASE X 

FIGURE 3.-Log distributions of Ca, Fe, Mg, Ti, Ba, and Mn. Dashed line segments indicate extrapolation. 
20 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

0.4 

99.99 

Q 

....J 

<C 

99 

98 

95 

90 

~ 80 

>- I-

~~bo <C 

00 

~ 60 

e:. 

!z 50 LIJ 

<:..) e:i 40 c... 

30 

20 

10 

5 

2 

0.5 

9 10 11 12 13 14 15 16 

LOG BASE X 

17 18 19 20 

Sr 

I 

I 

I 

21 22 23 

FIGURE 4.-Log distributions of Sr, Zr, V, Cr, Cu, and Cu (A). Dashed line 

segments indicate extrapolation. 
GEOCHEMICAL STUDIES 21 

viewpoint, these averages based on all samples collected are arbitrary estimates of the true formation abundances. The graphs in 

the other columns are intended to show the metal content of 

different stratigraphic members in terms of the average metal 

content of the entire formation more readily than could be seen 

from a comparison of figures in parts per million. Thus, for 

PARTS PER MILLION 

0.0125 0.05 0.2 0.8 3.2 12.8 209.6 838.4 

99.99 

Co Pb,Ni y I 99.9 I I I 

I I I Ag(A) I I 99.8 Hg(A) I I 

I I ! I 

99 

98 

GJ 

~ 95 (..) 

(I) 

!;: 90 ...J 

iii 

< cc 

~ 80 e::. 

1-

i:5 70 (..) 

IX 

~ 60 

50 

40 

30 

20 

10 

Ni 

5 

2 2 3 4 5 6 8 9 10 11 

LOG BASE X 

FIGURE 5.-Log distributions of Y, Ph, Ni, Co, Ag(A), and Hg(A). Dashed 

line segments indicate extrapolation. 
22 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

Q 

....I 

C( 

0.00625 

99.99 

99.9 

99.8 

~ 99 

> 1-

;! 98 Cll 

C( 

Cll 

0 

~ 95 

1-

z 

UJ 

~ 90 UJ 

a.. 

80 

70 

60 

50 

0.025 

2 3 4 

PARTS PER MilLION 

0.1 0.4 1.6 6.4 25.6 102.4 419.2 

5 6 8 9 10 11 12 13 14 15 16 17 

lOG BASE X 

FIGURE 6.-Highly truncated log distributions of Be and Au (A). Dashed line 

segments indicate extrapolation. 

TABLE 6.-Selected measures of central tendency and dispersion computed for 

the log distributions of the 20 metals used in the Moenkopi study 

[Metal symbols accompanied by "A" indicate analyses by atomic-absorption method] 

Logarithmic measures 1 Arithmetic measures, in parts per million 2 

Expected range 

Standard of geometric 

Metal Standard Mean error of Geometric Median mean at 

deviation mean 95-percent mean significance level 

Ca --------------------- 1.582 22.749 0.0880 22,000 29,000 20,000-25,000 Fe _____________________ 1.163 21.437 .0647 8,900 11,000 8,100-9,700 Mg _____________________ 1.565 20.641 .0871 5,100 7,000 4,500-5,800 Ti ______________________ 1.207 17.891 .0672 760 790 690-830 Ba _____________________ 1.552 16.998 .0864 410 440 360-460 Mn ____________________ 1.114 15.997 .0620 190 180 170-210 Sr _______________________ 1.275 14.996 .0709 100 81 91-110 Zr _______________________ 1.360 14.575 .0757 76 78 69-85 v _________________________ 1.129 13.265 .0628 31 34 28-34 Cr _______________________ 1.114 12.793 .0620 22 27 20-24 Cu(A) _______________ 1.356 11.985 .0754 12 10 11-14 Cu ______________________ 1.602 11.626 .0891 10 11 9-11 y ________________________ .945 11.813 .0526 11 11 1Q-12 Pb ______________________ .676 11.730 .0376 11 10 10-11 Ni _______________________ 1.057 10.948 .0588 6.2. 7.1 5.6-6.7 Co _______________________ 1.028 10.246 .0572 3.8 2.3 3.5-4.1 Be ______________________ .539 7.414 .0300 .. 53 Unknown 0.51-0.56 Ag(A) ______________ 1.244 6.370 .0692 .26 .25 0.24-0.28 Hg(A) ______________ 1.535 5.393 .0854 .13 .13 0.12-0.15 Au(A) _____________ 1.209 2.333 .0673 .016 Unknown 0.014-0.017 

1 Logarithms to base x (Cadigan, 1969) • 2 Rounded to two significant figures. 
Ca 

Fe 

Mg 

Ti 

Ba 

Mn 

Sr 

Zr 

v 

Cr 

Cu(A 

Cu 

y 

Pb 

Ni 

Co 

Be 

) 

) 

) )I 

Ag(A 

Hg(A 

Au(A ):JI 

0 

0.1 

I 

~ 

I 

I 

5 

GEOCHEMICAL STUDIES 

PARTS PER MILLION 

3.2 102.4 3276.8 

I I I 

)I 

)I I 

)f I 

)f I 

)I I 

)I I 

>I I 

)I I 

)I I 

)I I 

)II 

)I • 

)I 

)I 

)I I 

)II EXPLANATION 

I )i 

Range of geometric • mean 

~ 

Detection limit 

I I I 

10 15 20 

LOG BASE X 

23 

104,857.6 

I 

• 22,000 

8900 

5100 

760 

410 

z 190 0 

::i 

...J 100 ~ 

a:: 76 UJ 

c.. 

en 31 1-

a:: 

<( 22 c.. 

~ 12 

z 

<( 

UJ 10 

~ 

u 11 

a: 

1-

UJ 11 ~ 

0 

UJ 6.2 (.!) 

3.8 

0.53 

0.26 

0.13 

0.016 

I 

25 

FIGURE 7.-Mean abundance of 20 metals in the Moenkopi Formation, limits 

of detection, and range of geometric means. Units of horizontal scale are 

logarithmic (base x). Metals are arranged from top to bottom in order of 

decreasing abundance. 

example, in column A, the horizontal bars representing the standard values of Ca and Pb are of the same length and each represents the abundance of its respective element; the bar for Ca 

represents its geometric mean, 22,000 ppm, whereas the bar for 

Pb represents its geometric mean, 11 ppm. The respective lengths 

of the bars for Ca and Pb in column B indicate that Ca in the 

Shnabkaib Member is about 1.4 tin1es as abundant as Ca in the 

entire formation, whereas Ph in the Shnabkaib is nearly two times 

as abundant as the formational abundance of Ph. The horizontal 

scale is graduated geometrically to indicate 0.25, 0.5, 1.0, 2.0, and, 

for some members, 4.0 times the formation geometric mean. 
A Moenkopi Formation 

METALS (323 samples) 

Ca 

Fe 

Mg 

Ti 

Ba 

Mn 

Sr 

Zr 

v 

Cr 

Cu(A 

Cu 

y 

Pb 

Ni 

Co 

Be 

Ag(A 

Hg(A 

Au(A 

I I 

I 

) 

) 

) 

I I 

0.25 0.5 1.0 

22,000 

8900 

5100 

760 

410 

190 

100 

76 

31 

22 

12 

10 

11 

11 

6.2 

3.8 

0.53 

0.26 

0.13 

0.016 

0.25 

GEOMETRIC MEAN, 

IN PARTS PER MILLION 

0.5 1.0 2.0 0.25 

c Tenderfoot Member 

(22 samples) 

I I 

I I 

0.5 1.0 

GEOMETRIC RATIOS 

I 

I 

2.0 0.25 

D Hoskinnini Member 

(49 samples) 

I I 

I I 

0.5 1.0 

I 

I 

2.0 

~ 

~ 

0 

t:rj 

0 

Q 

::r: 

t:rj 

~ 1--4 

Q 

> t"" 

tj 

1--4 

00 

t-3 

~ 1--4 

t::d 

~ 

t-3 

1--4 

0 

,:Z 

~ t:rj 

t-3 

> t"" 

.rn 

~ 

0 

t:rj 

z 

~ 

0 

., 

1--4 
E Holbrook Member 

(12 samples) 

I I 

1---

r-----

I I 

I 

I 

0.25 0.5 1.0 2.0 

I 

I 

F Wupatki Member 

(6 samples) 

G Upper slope-forming member 

(44 samples) and cliffforming member (14 samples) 

I I I 

-

I I I 

4.0 0.25 0.5 1.0 2.0 0.25 0.5 1.0 2.0 

GEOMETRIC RATIOS 

I 

I 

H 

Lower red member 

(8 samples) 

J 

4.0 0.25 0.5 1.0 2.0 

METALS 

Ca 

Fe 

Mg 

Ti 

Ba 

Mn 

Sr 

Zr 

v 

Cr 

Cu(A) 

Cu 

y 

Ph 

Ni 

Co 

Be 

Ag(A) 

Hg(A) 

Au(A) 

4.0 

FIGURE B.-Comparison of metal content of some members of the Moenkopi Formation with average metal content of the entire formation. All values compared are geometric means. Horizontal 

scale indicates proportion, or geometric ratio, in terms of the standard, column A. 

C':l 

M 

0 

Q 

::r: 

M 

~ 1-1 

Q 

> t'-4 

rn 

1-3 

c:::: 

tj 

1-1 

M 

rn 

~ 

01 
26 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

The Shnabkaib Member (fig. 8, col. B) is a marginal marine 

evaporite sedimentary unit containing gypsum, limestone, and 

limy siltstone. Compared with the formation mean, the Shnabkaib 

contains on the average much more Ca, Mg, Sr, Pb, and Ag(A), 

but it contains less than half as much Fe, Ti, Ba, V, and Ni, and 

much less of almost all the other metals. 

The Tenderfoot Mem.ber (fig. 8, col. C) is an arkosic continental 

alluvial sedimentary unit in western Colorado and eastern Utah 

and was probably derived from the Uncompahgre highland source 

area in western Colorado. Of the 20 geometric means, 15 are 

higher than the formation means. Using unadjusted chi-square, 

we found this number of differences to be statistically significant 

at the 95-percent confidence level. Thus, a comment that the 

Tenderfoot has a significantly higher metal content than the formation as a whole refers to the fact that a significant number 

( 15 or more) of geometric means for the Tenderfoot are higher 

than the comparable formation geometric means. Differences between comparable geometric means for individual metals are sometimes described in terms of magnitude. An order of magnitude 

difference would indicate that one of two geometric means being 

compared is two times, or more, larger than the other. The simple 

terms "higher" or "lower" describe general differences of less 

than an order of magnitude between compared geometric mean 

values. The individual metal geometric means in the Tenderfoot 

do not vary nearly as much from corresponding formation means 

as do those of the Shnabkaib. Au (A) content in the Tenderfoot is 

slightly higher than the formation mean. 

The Hoskinnini Member (fig. 8, col. D), although correlated 

with the Tenderfoot Member (Stewart, 1959) because both 

occupy similar positions in the stratigraphic column in adjacent 

areas, has significantly lower metal content than the Tenderfoot 

and than the formation as a whole. Individual metals in all threeHoskinnini Member, Tenderfoot Member, and the formation as a 

whole-however, are present in quantities of the same order of 

magnitude. Au (A) content in the Hoskinnini is slightly lower than 

the formation mean. 

The Holbrook Member (fig. 8, col. E), a sandstone-siltstone unit 

with conspicuous sandstone beds, and the Wupatki Member (fig. 8, 

col. F), a siltstone-sandstone unit also with conspicuous sandstone 

beds, in north-central Arizona were probably derived from sources 

in southwestern New Mexico and southeastern Arizona. Both are 

generally lower in metal content than the formation, the Holbrook 

significantly so. Particularly noticeable is the low Mg content of 
GEOCHEMICAL STUDIES 27 

both members. It is about one-fourth the formation geometric 

mean. Cu (A) for the two members is about half the formation 

mean, but Au (A) is only slightly lower. Sr in the Wupatki 

Member is lower by an order of magnitude than the formation 

mean. 

The low Mg values probably reflect the lower proportions of 

mica and chlorite in these rocks as compared with those derived 

from Uncompahgre highland sources (p. 10). 

The upper slope-forming member and the overlying but not 

everywhere distinguishable cliff-forming member (fig. 8, col. G), 

the uppermost members of the Moenkopi in southeastern and 

eastern Utah, are examples of the typical red siltstone-sandstone 

facies and represent a low-energy alluvial-plain environment of 

deposition. They were derived from generally the same sources as 

the Tenderfoot and Hoskinnini Members. Their content of metals 

is significantly higher than the formation mean, and Cu is more 

than twice as abundant. Other conspicuously high value metals are 

Cu(A), Co, Hg(A), and V. The abundance of Cu and other metals 

is probably not related to source or depositional environment 

because in the Tenderfoot Member, which is similar to the upper 

slope-forming and cliff-forming members in terms of source, 

Cu is only slightly above the formation mean. The high Cu content 

in the upper slope-forming and cliff-forming members may be 

related to the uranium deposits that occur in some localities at or 

just above the Moenkopi-Chinle contact. More evidence of this 

possible relationship is considered later in the report (p. 40). 

Au (A) content is about the same as the formation mean. 

The lower red member (fig. 8, col. H) (red calcareous coarse 

siltstone, very fine grained sandstone, and limestone) in southwestern Utah, southeastern Nevada, and northwestern Arizona is 

thought to be marginal marine in origin. Detrital sediment was 

probably derived from source areas in southern Arizona. Compared with the formation mean, the average metal content is significantly lower in the lower red member; Ca, Sr, and Ag(A) are 

much higher; Ti and Zr, which are strongly related to terrestrial 

detritus, are lower by two orders of magnitude; and Au (A) is 

slightly lower. 

In summary, figure 8 illustrates differences among the geometric 

means for the formation and the individual members that can 

be attributed to the effects of specific geologic variables related to 

provenance. The significant and order-of-magnitude differences 

between geometric means of the formation and those of the Shnabkaib and lower red members (fig. 8, cols. Band H) reflect major 
28 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

variation in source. The principal source of metals of the two 

members was the sea by way of the complex of marine environments of deposition, characterized by high Ca, Sr, Mg, Pb, and 

Ag (A). (Ag (A) values, however, may be analytically dependent 

on Ca values, as discussed on p. 15.) The low Fe, Ti, Mn, Zr, and 

V geometric means are an indication that terrestrial sources supplied only a minor proportion of the sediment and metal content of 

these members. 

Variation in metal content resulting from differences between 

terrestrial sources is illustrated by the significant, but less than 

order-of-magnitude, differences between the Hoskinnini and Tenderfoot Members, which variation suggests minor differences 

between two similar terrestrial sources. On the other hand, the 

significant and, for some metals, order-of-magnitude differences 

between the Tenderfoot and the Holbrook and Wupatki Members 

(for example, the deficiencies of Mg, Fe, Cr, Cu, and Cu (A) in 

the Holbrook and Wupatki) reflect major differences between 

terrestrial sources. 

A third type of variation results from the effect of an extrinsic 

source and is represented by the contrast between the higher 

amounts of Cu, Cu (A), and Hg (A) in the upper slope-forming 

and cliff-forming members as compared with the Tenderfoot and 

Hoskinnini Members. The increases of metal abundances in the 

upper slope-forming and cliff-forming members are the effects 

of interstratal solutions acting as a supplementary extrinsic source 

of metals. 

Other variables whose effects are not demonstrable in figure 8 

but which no doubt control to some extent the variation of metal 

content in Moenkopi rocks are the process of diagenesis (which, 

however, is thought to be a regional constant), particle size, and 

particle composition, a function of particle size, diagnenesis, and 

source. 

Although none of the members of the Moenkopi is composed of 

particles of only one size classification, members can be grouped 

into facies according to general differences in texture and composition (p. 7). 

FACIES COMPARISONS 

Rock facies are defined for purposes of this report as certain 

combinations of particle size and mineral composition. The three 

major facies are (1) siltstone-sandstone facies-the dominant 

Moenkopi rock type; (2) sandstone facies-represented by samples from the Holbrook, Hoskinnini, and Tenderfoot Members of 
GEOCHEMICAL STUDIES 29 

the Moenkopi; and (3) limestone-evaporite facies-represented 

by samples from the Timpoweap, Virgin, Sinbad, and Shnabkaib 

Members of the Moenkopi and Thaynes Formations. Differences 

in metal content among the three facies are shown graphically in 

figure 9. Unity, or the standard of comparison, is once again the 

formation geometric mean (fig. 8, col. A). 

METALS 

Ca 

Fe 

Mg 

Ti 

Ba 

Mn 

Sr 

Zr 

v 

Cr 

Cu(A) 

Cu 

y 

Ph 

Ni 

Co 

Be 

) 

) 

Ag(A 

Hg(A 

Au(A) 

A 

Siltstone-sandstone facies 

(217 samples) 

I I I 

I I I 

I 

B Sandstone facies 

(83 samples) 

I I 

1 I I 

I 

I 

I 

c Limestone-evaporite facies 

(23 samples) 

0.25 0.5 1.0 2.0 4.0 0.25 0.5 1.0 2.0 4.0 0.25 0.5 1.0 2.0 4.0 

GEOMETRIC RATIOS 

FIGURE 9.-Comparison of metal content of rocks from different facies with 

average metal content of the entire formation as shown in figure 8, column A. All values compared are geometric means. 

The siltstone-sandstone facies (fig. 9, col. A), partly because 

it is represented by 65 percent of the total samples collected from 

the Moenkopi, shows no order-of-magnitude differences from the 

formation mean; it does, however, show statistically significant 

slightly higher mean metal content that the formation. 

The sandstone facies (fig. 9, col. B) shows no significant differences, but it does show a generally lower mean metal content 

than the formation. 
30 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

The limestone-evaporite facies (fig. 9, col. C) shows the greatest 

differences compared with the formation means. Ca and Mg are 

at least twice as high, and Fe, Ti, Zr, V, Cr, Cu, and Ni are only 

about half as high as the formation geometric means, a repetition 

of the proportions observed for the marine members illustrated 

in figure 8. This facies is dominantly marine in origin. The siltstone-sandstone and sandstone facies are composed dominantly 

of terrestrial sediments. 

Au (A) geometric means for the siltstone-sandstone and limestone-evaporite facies are about the same as the formation mean. 

The Au (A) mean for the sandstone facies is slightly lower. 

GEOCHEMICAL ASSOCIATION OF THE METALS 

The 10 comparative graphs in figures 8 and 9 were used to 

investigate element covariation in the Moenkopi Formation. Each 

metal value on each graph was compared with the formation mean, 

and the result of the comparison was "sensed" as "plus," "minus," or "equal." Using this technique, the 10 X 20 matrix in table 

7 was prepared. The matrix consists of plus ( +), minus (-), 

and zero ( 0) symbols which describe a non parametric relationship 

TABLE 7.-Sensings of comparisons of metal values in the different groups of 

samples with the formation geometric means as illustrated in figures 8 and 9 

[Explanation of symbols: +. more than the formation mean;-, less than the formation mean; 0, equal to the formation mean. (A) following metal symbol indicates analysis by atomic- absorption method] 

Figure 8- Figure 9-

B c D E F G H A B c 

Ca __________________ + + + + Fe __________________ Mg + + + _________________ + + + + 0 + TL __________________ - + + + + + Ba __________________ + + + + + + 

Mn __________________ + + + + Sr ___________________ + + + + Zr 0 + ___________________ - + + + + + y ____________________ + Cr - + + ___________________ - + + + + + 

Cu (A) ___________ - + + + Cu __________________ + + + y ____________________ - + + + Pb __________________ NL + + + + + + __________________ - + + + + + 

Co ___________________ Be + + + ___________________ - + - Ag( A) ___________ Hg( A) + + + + ___________ + + + + + + + Au (A) ___________ 0 + + + + 
GEOCHEMICAL STUDIES 31 

between the geometric mean for each metal in each of the 10 

subdivisions and the formation geometric mean for that metal. 

Nonparametric relationship as used here means one which is not 

defined by numerical measurements. N onparan1etric statistics 

have been described by Siegel (1956). 

The sensings in the matrix for each metal were then compared 

with the sensings for every other metal. The number of agreements was divided by 10, and the result was labeled the coefficient 

of association. For example, the sensings of Ca and Fe agree in 

three of the 10 columns; the coefficient of association is threetenths, or 0.3. The sensings of Sr and Zr agree in none of the 

columns, but for figure 9, column A, they are 0 and + respectively. 

The 0 used to indicate equality with the formation mean is, for 

convenience, assigned a value of one-half, so the coefficient of 

association for Sr and Zr becomes five-hundredths, or 0.05. 

Table 8 shows the calculated nonparametric association coefficients. The statistical significance of such coefficients as these 

has not been previously established. The metal abundances originally compared are means rather than individual sample values, 

which has the effect of lowering the probability of significantly 

high association coefficients occurring by chance. 

To establish a basis for defining significance limits, an experiment was done using 200 random single sensings to produce a 

10 x 20 matrix similar to that shown in table 7. The sensings were 

obtained by assigning "plus" to even random numbers and "minus" to odd numbers. Theoretical coefficients were then computed. 

The resulting normal distribution of coefficients, with its mean at 

0.5 by definition, was analyzed using probability paper. The significance levels estimated from the random distribution are as follows: 

Association 

coefficient 

Significance 

level 

0.65 ________________________________________________________________ 0.90 

.71---------------------------------------------------------------- .95 

.77---------------------------------------------------------------- .98 

.82---------------------------------------------------------------- .99 

On the basis of this estimate of significance and considering 

that means were used as already mentioned, coefficients of 0.80 

or higher and 0.20 or lower in table 8 were assumed to be very 

highly significant, meaning that the probability is less than 0.01 

that a coefficient of 0.80 or greater or 0.20 or less can occur by 

chance. Coefficients greater than 0.50 indicated positive relationships, and coefficients less than 0.50 indicate negative relationships. 

Of the 67 significant coefficients of association listed in table 

8, 56 are positive and only 11 are negative. Significant coefficients 
TABLE 8.-Nonparametric association coefficients measuring relative correlation between each possible pair of metals 

t~~~~~~~ 

r~~~~~ Cu (A)··----------------------- Cu __________________________________ _ y _______________________________ _ 

Pb ____________________________ _ NL ___________________ _ 

co ________________________ _ Be_ __________ _ 

Ag (A)-------------------

Hg(A)-------· 

Au (A)-------------

Ca Fe 

0.30 

Mg Ti Ba 

0.40 0.10 0.20 

.55 .80 .70 .65 .35 

.70 

[Significant coefficients are shown in italic] 

Mn Sr Zr v Cr Cu(A) Cu 

0.40 0.55 0.30 0.30 0.10 0.30 0.30 .90 .45 .60 1.00 .80 1.00 1.00 

.45 .50 .45 .55 .65 .55 .55 .70 .25 .80 .so 1.00 .80 .80 

.70 .35 .70 .70 .70 .60 .60 

.35 .70 .90 .70 .90 .90 

.05 .40 .25 .45 .45 .60 .80 .60 .60 .80 1.00 1.00 

.80 .80 

1.00 

y Pb Ni Co Be Ag(A) Hg(A) Au(A) 

0.30 0.40 0.10 0.30 0.50 0.80 0.70 0.45 .80 .30 .80 1.00 .so .50 .40 .85 

.45 .55 .45 .55 .55 .45 .55 .70 .so .50 .80 .80 .60 .30 .40 .65 .70 .60 .90 .70 .50 .20 .30 .55 

.70 .40 .60 .90 .70 .40 .50 .75 

.25 .25 .45 .45 .55 .75 .65 .50 .80 .70 .50 .60 .40 .20 .40 .45 .80 .30 .80 1.00 .so .50 .40 .85 

.80 .50 .80 .80 .60 .30 .40 .65 

.80 .30 .80 1.00 .so .50 .40 .85 

.so .30 .80 1.00 .so .50 .40 .85 

.40 .80 .80 .60 .50 .20 .65 

.50 .30 .30 .20 .20 .25 .80 .60 .30 .20 .65 

.80 .50 .40 .85 

.50 .40 .65 .70 .55 

.45 

~ 

I:\:) 

C) 

l:_:l:_j 

0 

l.l 

p:: 

l:_:l:_j 

a= 

~ 

() 

> t-'4 

t:j 

~ 

rn 

1-3 

~ ~ 

to 

c::: 

1-3 

~ 

0 

~z 

a= 

l:_:l:_j 

1-3 

> t-'4 

sn 

a= 

0 

l:_:l:_j 

z 

~ 

0 

~ ~ 
GEOCHEMICAL STUDIES 33 

for the elements Ca, Ag(A), Hg(A), and Sr are mostly negative. 

Discussion of geologic factors responsible for significant associations, both positive and negative, suggested by the coefficients 

in table 8, is based on previously reported petrologic relationships 

(Cadigan, 1971). 

Proportions of major components of sedimentary rocks-for 

example, nondetrital minerals and detrital minerals-tend to be 

negatively related to each other; as one increases in proportion the 

other decreases. Statistically, this is referred to as the relation 

of components of a constant sum (Chayes, 1960). Of the metals 

in this study, only Ca could be classified as a major component; 

it is a constituent of calcite, gypsum, and dolomite, the most 

abundant cementing minerals in the Moenkopi. The other metals 

are, volumetrically, considerably less abundant and may be considered, for purposes of this report, as minor rock components, 

without inherent direct negative associations. 

The significant negative correlations around Ca-Ti, Cr, Ni, 

and Ba-probably reflect indirectly the negative relationship between proportion of cement and proportion of detritus. Cr and Ni 

are assigned generally to the detrital fraction and specifically to 

the heavy mineral fraction which is concentrated chiefly in the 

very fine sand-sized or very coarse silt-sized particles. 

Thus as Ca-bearing cements increase, the proportion of Ti-, 

Cr-, and Ni-bearing detritus decreases. Ba, on the other hand, 

occurs chiefly in barite, an interstitial cementing mineral. Petrographic relations suggest that barite replaces calcite in sandstones; thus the Ca-to-Ba negative correlation supports the petrographic interpretation and suggests that such replacement occurs 

only in detrital rocks and in proportion to the amount of detritus 

present. 

The significant negative associations around Ag(A)-Ba, Zr, 

and Pb-are not discussed in this report because of the unreliability of the Ag (A) analytical results from samples that contain 

high proportions of calcite. 

The significant negative associations around Hg (A)-Y, Pb, 

and Ni-are also suggestive of a negative relationship between 

non detrital and detrital components. Hg (A) has a high positive 

but nonsignificant correlation with Ca which, together with abundances shown in figures 8 and 9, indicates that Hg(A) is more 

abundant in highly calcareous rocks than in detrital rocks. Rankama and Sahama (1950) noted that in a marine environment, 

clay minerals tend to concentrate Hg (A). This tendency would 

explain the preference of Hg (A) for both the clayey and the 
34 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

calcareous marine sediments. Another association, illustrated in 

figure 8, column G, is that Hg(A) values are high in many samples collected near uranium deposits. Thus the high Hg (A) mean 

for the upper slope-forming and cliff-forming members is probably the effect of the presence of the uranium deposits and associated mineralizing solution activity at the top of the members in 

some localities. 

The negative association between Sr and Zr in light of the 

almost significant negative relationships of Sr to Ti, Cr, Pb, and 

Y seems at first glance to be another detrital-to-nondetrital relationship. Strangely, however, Sr, although noticeably high in 

marine and marginal marine sediments, shows only a random 

association with Cain table 8. According to Rankama and Sahama 

( 1950), Sr occurs most commonly as a sulfate in sedimentary 

rocks and may occur as a residual after the removal of aragonite 

or calcite by solution action. Evidence of such removal is present 

in crumpled, distorted clayey and fine siltstone strata in the 

Moenkopi. Sr, then, is not associated either positively or negatively 

with Ca cements. It has a sharp negative association with Zr and 

therefore with the heavy-mineral-bearing very fine sand and very 

coarse silt fraction. Sr thus is believed to occur in marginal marine 

evaporites and also in the clay and fine silt facies of terrestrial 

sedimentary rocks, both of which, in terms of proportions, would 

bear negative relationships to the Zr-bearing sand fractions. 

Low coefficients of association (0.35 to 0.65) between any two 

metals that have strong mineralogic associations may be explained 

in terms of multiple modes of occurrence. For example, Ca and 

Mg are associated in cement-forming carbonate minerals, but 

Mg also occurs in certain detrital minerals that do not contain 

Ca, including the micas, their alteration product chlorite, and 

some of the quantitatively significant clay minerals. Thus, although Mg and Ca show strong positive association in the marine 

and marginal marine rocks (fig. 8, cols. B and C), the association 

is negative in terrestrial sediments (fig. 8, cols. C, E, F, and G). 

Figure 10 illustrates the significant positive associations among 

20 metals based on the coefficients shown in table 7. The largest 

group of interassociated metals comprises Fe, V, Cu, Cu(A) Co, 

Ti, Cr, Y, and Ni. These metals are subdivided as shown because 

other individual metals are associated separately in occurrence 

with the two major subgroups. Ni is associated with both subgroups and with Ba, which in turn is associated with no other 

metal. Au (A), Be, and Mn each appear to be associated individually with metals of the upper subgroup, and Zr is associated 
GEOCHEMICAL STUDIES 35 

8 

I I 

0= 0 

0 

ASSOCIATED METALS 

8 

PROBABLY ARTIFICIALLY ASSOCIATED METALS 

0 () 8 

UNASSOCIATED METALS 

FIGURE 10.-Significant positive associations of metals in the Moenkopi 

Formation. 
36 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

with metals of the lower subgroup. The grouping suggests that, 

in Moenkopi Formation rocks, Zr, Ti, Cr, and Y are principally 

detrital-controlled metals, and Fe, V, Cu, Cu (A), Co, Ni, Be, 

Au (A), and Mn are detrital- and solution-controlled metals. 

Four metals, Mg, Sr, Pb, and Hg (A), show no significant positive associations. If the Ca-to-Ag relationship is manmade, then 

Ca also belongs down in the bottom row of circles in figure 10 

as a metal lacking positive associations. 

The apparently isolated significant positive association between 

Ba and Ni is not really isolated. High coefficients of association 

(0.70) suggest strong positive relationships between Ba and Fe, 

Ti, Mn, Zr, V, Cr, Y, and Co, which includes all the metals except 

Cu and Cu (A) to which Ni is significantly positively related. 

Fe occurs commonly as a red oxide-an almost universal alteration product and rock-coloring pigment in the Moenkopi-and 

suggests itself as a metal very likely to be taken into solution by 

and redeposited from interstratal solutions. The significant positive associations with other metals, such as Cr, Y, and Ti, and 

through them with detrital-carried Zr suggest, however, that Fe 

and associated soluble metal ions do not migrate far from their 

original point of deposition. In other words, the red beds of the 

Moenkopi are colored by oxidized Fe from their contained Febearing detritus. 

Pb shows no significant positive associations possibly because 

of its multiple modes of occurrence. According to Rankama and 

Sahama (1950), Pb is high in granitic source rocks, easily removed in solution, subject to precipitation in alluvial environments, and, in sea water, concentrated in clays and in sulfate 

evaporites. Potentially, then, Pb could be present in detrital rock 

fragments, in interstitial precipitated minerals in terrestrial rocks, 

and in marine mudstones and in marginal marine evaporites, 

which, barring the possibility of contamination, may account for 

its relatively consistent abundance in most Moenkopi rocks. 

TEXTURAL AND COMPOSITIONAL COMPARISONS 

Possible relations between texture and metal content of sandstones, siltstones, mudstones, claystones, and limestones were investigated using sets of samples randomly selected from those 

for which textural data were available (Cadigan, 1971). Sample 

data are listed in table 9. 

The metal content of six very coarse and coarse-grained sandstones and the geometric mean for each metal are shown in the 

first half of table 9. Grain size (median) and sorting (phi stand-
GEOCHEMICAL STUDIES 37 

TABLE 9.-Metal content (in parts per million) of randomly selected samples 

of very coarse, coarse, medium, fine, and very fine grained sandstones from 

Moenkopi Formation 

[Samples are listed in order of decreasing grain size from left to right. Geometric mean values are italicized for contrast. Values in parentheses are below detection levels; see discussion on p. 16. Analyses were by six-step spectrographic method, by J. L. Finley, except that analyses of the following were by atomic-absorption method: Cu(A) and Ag(A), by A. J. Toevs and Lucy Dickson; Hg(A), by W. W. Janes. Standard deviation and median grain diameter pertain to the phi grain-size distribution] 

Standard deviation (phi)_ Median grain diameter ( mm) __ Field No. ________________ _ 

Laboratory No. (AA-) _______________ _ 

ca ____________________________ _ Fe _____________________________ _ Mg ___________________________ _ Ti ____________________________ _ Ba ____________________________ _ 

Mn ___________________________ _ Sr _____________________________ _ Zr ____________________________ _ y ______________________________ _ Cr ____________________________ _ 

Cu(A) _____________________ _ cu ____________________________ _ y ______________________________ _ 

Pb ____________________________ _ NL __________________________ _ 

co ____________________________ _ Be ____________________________ _ Ag(A) ____________________ _ Hg(A) ____________________ _ Au(A) ___________________ _ 

Standard 

Median grain deviation (phi)_ diameter (mm) __ Field No. ________________ _ 

La bora tory No. (AA-) ____________ _ 

ca ___________________________ _ Fe ____________________________ _ Mg ___________________________ _ Ti _____________________________ _ Ba ____________________________ _ 

Mn ___________________________ _ Sr _____________________________ _ 

Zr ____________________________ _ v ______________________________ _ Cr ____________________________ _ 

Cu(A) ____________________ _ Cu ____________________________ _ y ______________________________ _ Pb ____________________________ _ Ni_ ___________________________ _ 

co ____________________________ _ Be ____________________________ _ Ag(A) _________________ _ Hg(A) ___________________ _ Au(A) ___________________ _ 

Very coarse and coarse grained sandstones 

3.02 

1.55 

L2617 

B999 

10,000 

20,000 

5,000 

700 

3,000 

150 

300 

50 

50 

30 

12 

6 

15 

20 

7 

5 

1.0 

.3 

.03 

.02 

2.80 

1.30 

L4763 

D080 

7,000 

15,000 

5,000 

700 

1,500 

200 

70 

70 

30 

20 

12 

6 

(5) 

10 

7 

7 

(.5) 

(.1) 

(.005) 

(.01) 

2.83 

1.18 

L4764 

D081 

1,000 

10,000 

5,000 

700 

3,000 

50 

70 

70 

30 

20 

12 

7 

(6) 

10 

7 

5 

(.5) 

(.1) 

.025 

(.01) 

1.80 

0.97 

L2545 

B982 

70,000 

5,000 

1,600 

200 

700 

200 

100 

30 

20 

20 

25 

2 

10 

10 

3 

(1.5) 

(.6) 

.4 

.06 

(.01) 

2.13 

0.64 

L2629 

B005 

15,000 

15,000 

10,000 700 

700 

300 

70 

70 

50 

16 

16 

6 

10 

10 

6 

7 

(.5) 

.25 

.20 

(.01) 

Medium, fine, and very fine grained sandstones 

1.96 

0.38 

L2612 

B994 

10,000 

20,000 

5,000 

1,500 

1,000 

200 

100 

150 

30 

50 

27 

10 

30 

20 

5 

7 

(.6) 

.25 

.16 

.02 

2.16 

0.31 

L3718 

D067 

15,000 

10,000 500 

700 

500 

150 

70 

150 

30 

20 

12 

7 

15 

15 

10 

10 

(.5) 

.60 

.06 

(.2) 

1.73 

0.24 

L1636 

B845 

50,000 

7,000 

15,000 

1,000 

200 

150 

100 

50 

50 

30 

60 

15 

10 

(5) 

5 

(1.5) 

(.5) 

(.1) 

.40 

(.01) 

2.08 

0.17 

L1352 

B835 

30,000 

2,000 

7,000 

500 

700 

100 

70 

30 

70 

20 

125 

70 

(5) 

(5) 

3 

(1.5) 

(.5) 

.45 

.50 

(.01) 

1.76 

0.12 

L1993 

B910 

30,000 

10,000 

2,000 

700 

1,600 

300 

2,000 

150 

30 

30 

(5) 

10 

10 

10 

7 

3 

(.5) 

.35 

.09 

.3 

1.80 

0.63 

L2627 

B003 

30,000 

15,000 

20,000 

600 

700 

300 

70 

30 

20 

30 

32 

3 

(6) 

10 

3 

6 

(.6) 

(.1) 

.05 

(.01) 

1.65 

0.084 

L3198 

D0 53 

10,000 

7,000 

2,000 

1,000 

700 

200 

30 

150 

30 

30 

42 

5 

10 

10 

5 

3 

(.6) 

.35 

.30 

.01 

Geometric 

mean 

15,780 

12,250 

5,785 

537 

1,291 

179 

95 

50 

81 

22 

17 

.u 

76 

11 

50 

4.6 

.56 

.18 

.036 

.011 

Geometric 

mean 

20178 

7,622 

9,188 

846 

647 

179 

120 

96 

88 

29 

!8 

12 

11 

10 

5.5 

8.4 

.5 

.91 

.19 

.015 

ard deviation) are given for each sample. Figure 11, column A, 

shows the comparison of the geometric means of the six samples 

with the geometric means of the Moenkopi as a whole. Major 

(order-of-magnitude) differences are those of the relatively high 
38 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

A Very coarse and coarsegrained sandstones 

METALS (6 samples) 

Ca 

Fe 

Mg 

Ti 

Ba 

Mn 

Sr 

Zr 

v 

Cr 

Cu(A) 

Cu 

y 

Ph 

Ni 

Co 

Be 

Ag(A) 

Hg(A) 

Au(A) 

I I I 

1----

-

rI I I 

I 

I 

B Medium, fine, and very fine 

grained sandstones 

(6 samples) 

I I I 

-

I I I 

I 

I 

c Siltstones 

(6 samples) 

I I 

-

I I 

I 

I 

0.25 0.5 1.0 2.0 4.0 0.25 0.5 1.0 2.0 4.0 0.25 0.5 1.0 2.0 

GEOMETRIC RATIOS 

FIGURE H.-Comparison of metal content of groups of samples having 

formation as shown in figure 8, column A. All 

Ba and the relatively low Hg (A) in the coarse-grained fraction 

of the formation. Cu is low and Cu (A) is high, suggesting that 

results of the two analytical methods are not comparable for 

very coarse and coarse-grained sandstone. 

The second half of table 9 lists the metal content of six medium, 

fine, and very fine grained sandstones. Figure 11, column B, 

shows the comparison of their geometric means to the formation 

as a whole; Cu (A) is an order of magnitude higher. Hg (A) and 

Cu are higher and Mg and Ba are notably lower in column B 

than in column A of figure 11. 

Means for 14 of the 20 metals are higher in the medium, fine, 

and very fine grained sandstones than in the coarse-grained sandstones. Ten of these metals exceed the formation mean, compared 

with only eight of the metals in the coarser sandstones. These 

general increases in metal content are compatible with the petro-
<0.25 

<0.25 

I 

~ 

I 

D 

Claystones 

(2 samples) 

I I I 

GEOCHEMICAL STUDIES 

E Calcareous siltstone, 

limestone, and dolomite 

(6 samples) METALS 

I 

~~--~---,---,--~ 

<0.25 

<0.25 

<0.25 

Ca 

Fe 

Mg 

Ti 

Ba 

Mn 

Sr 

Zr 

v 

Cr 

Cu(Af 

Cu 

y 

Pb 

Ni 

Co 

Be 

Ag(A) 

Hg(A) 

Au(A) 

0.25 0.5 1.0 2.0 4.0 8.0 0.25 0.5 1.0 2.0 4.0 8.0 

GEOMETRIC RATIOS 

different textures with average metal content of the entire 

values compared are geometric means. 

39 

graphic evidence that the fine and very fine sand sizes contain 

larger proportions of heavy minerals than do the coarser sizes. 

Table 10 lists the metal content of six siltstones, ranging from 

coarse to very fine grained. Figure 11, column C, shows the comparison of their geometric means with the formation means. As 

in the medium to very fine grained sandstones (table 9), the 

metal content compared with the formation mean metal content 

shows no order-of-magnitude differences; 12 metals are higher 

and eight are lower. Mn and Cr are conspicuously higher. Mn is 

almost twice as high in the siltstones as it is in the two groups 

of sandstones. 

Table 10 also lists the metal content of two claystones, and 

figure 11, column D, shows the comparison of their log means 

with the formation means. Several metals are higher-Cr. Cu, 

Co, Be, and Au(A) by one order of magnitude and Fe and Ni by 
40 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

two orders of magnitude. Ca, Ba, and Mn are lower by two orders 

of magnitude. 

A comparison of columns A, B, C, and D of figure 11 indicates 

that with decreasing grain size, Ti, V, Cr, Y. Ni, and Au show a 

persistent increase, Ba shows a persistent decrease, and Ca shows 

a small increase from column A through column C and an abrupt 

decrease in column D. Pb remains relatively constant. 

Table 10 also lists the metal content of six samples of calcareous 

siltstone, limestone, and dolomite ranging in soluble carbonates 

from 50 to 97 percent. The metals Ti, Ba, Sr, Zr, V, and Cr decrease 

as the amount of soluble carbonates increases. A comparison of 

chemically determined percent solubles with spectrographically 

determined Ca and Mg shows poor correlation; in sample L3145, 

for example, spectrographically determined Ca, Mg, and Fe as 

carbonates would account for only 40 percent of the acid solubles. 

Figure 11, column E, shows the comparison of the geometric 

mean metal values of the carbonate rocks with the formation 

geometric means. Not surprisingly, Ca, Mg, and Sr are much 

higher, Mg and Ca by one and two orders of magnitude, respectively. Ti, Ba, Zr, Fe, Cu, and Hg (A) are low by one or more 

orders of magnitude. The carbonate rocks, compared with the 

formation as a whole, are significantly lower in metals. 

Mudstones (poorly sorted siltstones and claystones) from the 

top of the Moenkopi in localities where uranium deposits are 

found in overlying rocks of the Chinle Formation vary widely in 

metal content. Table 11 lists the metal content in the only samples available from such rocks. These are compared in figure 12 

with ordinary siltstones (from table 10 and fig. 11, col. C). 

Metals that are one or more orders of magnitude more abundant in the mudstones than in siltstones, in order of decreasing 

differences from the siltstone means, are Cu, Cu (A), Y, Be, Sr, 

Ni, Co, Au (A), V, Ti, Fe, and Pb. Metals that are relatively low 

in amount are Ca, Mn, and Ag (A). Cu, specifically, is more than 

30 times higher than both the siltstone average (fig. 12, col. A) 

and the formation average (fig. 8, col. A). Au (A) is more than 

five times as high as the formation average. The value of Ca is 

less than one thirty-second of the formation mean; the value of 

Mn is about one-fourth the formation mean. The high metal 

values are undoubtedly related both to rocks with higher-thanaverage heavy mineral content (note: Zr, Cr, and Ti) and to the 

overlying uranium deposits. The high Cu, Cu (A), Y, Sr, Ni, Co, 

Be, and Au (A) probably represent enrichment by metal-bearing 

solutions moving along the Chinle-Moenkopi contact. 
TABLE 10.-Metal content (in parts per million) of randomly selected smnples of siltstones, claystones, and calcareous siltstones 

limestones, and dolomites from the Moenkopi Formation ' 

[Samples are listed in order of decreasing grain size from left to right. Geometric mean values are italicized for contrast. Values in parentheses are below detection levels; values in brackets are above the upper detection limits; see discussion on p. 16. Analyses were by six-step spectrographic method by J. L. Finley, except that analyses of the following were by atomic-absorption method: Cu(A) and Ag(A), by A. J. Toevs and Lucy Dickson; Hg(A)' by W. W. Janes. Standard deviation and median grain size pertain to the phi grain-size distribution]. ' 

Siltstones 

Standard deviation___________________________________________________ 2.19 1.78 1.57 2.16 2.67 1.96 Median grain diameter (mm)__________________________________________ 0.062 0.044 0.030 0.022 0.013 0.0043 Percent acid solubles _________________________________________________________________________________________________________________________ _ 

Field No____________________________________________________________ L1969 L1777 L262G L1G45 L1843 L187fi Laboratory No. (AA-)_ __ _ _ _ _ _ _ _ _ __ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ B902 B876 D002 B854 B88G B897 

Ca _______________________________ . Fe _________________________________________________________________ _ 

Mg_---------------------------------------------------------------- Ti _________________________________________________________________ _ Ba _________________________________________________________________ _ 

Mn ________________________________________________________________ _ Sr _________________________________________________________________ _ Zr _________________________________________________________________ _ 

v Cr ------------------------------------------------------------------- _________________________________________________________________ _ Cu(A) _____________________________________________________________ _ Cu ________________________________________________________________ _ 

Pb y------------------------------------------------------------------ ________________________________________________________________ _ 

NL __ ---------------------------------------------------------------

Co _________________________________________________________________ _ 

Be _________________________________________________________________ _ 

Ag(A) ______________________________________________________________ _ Hg(A) _____________________________________________________________ _ Au(A) ____ ----- ____________________________________________________ _ 

20,000 

5,000 

700 

700 

300 

150 

50 

200 

30 

30 

(5) 

2 

15 

10 

3 

(1.5) 

(.5) 

(.1) 

.10 

(.01) 

30,000 

10,000 

5,000 

700 

1,000 

300 

70 

150 

30 

30 

25 

20 

15 

10 

5 

(1.5) 

(.5) 

.35 

.08 

.02 

30,000 

10,000 

15,000 

1,500 

300 

300 

70 

15 

30 

50 

18 

7 

10 

10 

7 

3 

(.5) 

.40 

.05 

(.01) 

30,000 

15,000 

20,000 700 

500 

700 

70 

50 

30 

20 

25 

20 

15 

(5) 

5 

3 

(.5) 

(.1) 

.24 

.03 

20,000 

20,000 

10,000 

1,500 

200 

200 

100 

50 

70 

70 

30 

20 

15 

20 

15 

7 

(.5) 

(.1) 

.26 

.03 

30,000 

20,000 

15,000 700 

200 

700 

150 

30 

70 

50 

(5) 

15 

15 

15 

15 

7 

(.5) 

(.1) 

.w 

(.01) 

Geometric mean 

26,207 

12,009 

7,949 

902 

949 

991 

80 

57 

40 

98 

14 

11 

14 

10 

7.0 

9.2 

.5 

.15 

.19 

.016 

c;1 

t_:rj 

0 

0 

::r: 

t_:rj 

~ ~ 

0 

> 

t-t 

rn 

1-3 

~ 

tl 

~ 

t_:rj 

rn 

~ 

~ 
TABLE 10.-Metal content (in parts per million) of randomly selected samples of siltstones, claystones, and calcareous siltstones, 

limestones, and dolomites from the Moenkopi Formation-Continued 

Claystones Calcareous siltstones, limestones, and dolomites 

Standard deviation _____________ 2.20 2.08 Median grain diameter (mm) ____ 0.004 0.0023 Geometric _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Geometric 

Percent acid solubles ___________________________________ mean 50.7 62.7 82.2 87.5 93.1 97.1 mean Field No ______________________ L2057 L1755 L2157 L4776 L2303 L2150 L3152 L3145 Laboratory No. (AA-) __________ B918 B873 B933 D093 B954 B3932 B030 B025 

Ca ____________________________ 3,000 1,000 1,7!Jf 70,000 200,000 200,000 .50,000 50,000 70,000 88,790 Fe ____________________________ 30,000 70,000 J,5,8B5 7,000 3,000 2,000 3,000 3,000 7,000 J,,f8!J 

Mg_-------------------------- 3,000 15,000 6,708 7,000 2,000 2,000 30,000 30,000 70,000 10,992 

Ti__ -------------------------- 2,000 2,000 e,ooo 700 700 300 50 50 50 16f Ba ____________________________ 300 15 67 500 300 70 30 15 15 6.1, 

Mn ___________________________ 70 30 .1,6 500 300 200 100 70 300 199 Sr ____________________________ 70 70 70 1,500 500 300 150 50 30 192 Zr ____________________________ 70 150 102 70 20 30 (5) (5) (5) 1!J 

v ----------------------------- 70 30 .1,6 100 70 10 10 7 7 18 

50 70 59 30 50 10 50 5 3 15 

Cu(A) ________________________ 25 20 2B (5) 25 27 (5) 22 (5) 11 Cu _____ ----- _________________ 30 50 !J9 50 2 3 3 1 2 !J.5 

y---------------------------- 30 15 S1 15 (5) (5) (5) (5) (5) 6.0 Ph ____________________________ 15 10 u (5) (5) 30 (5) (5) (5) 6.7 NL __________________ ---- _____ 50 20 Sf 10 5 (1.5) 7 (1.5) 5 .t,.O 

Co ___________________________ 15 10 u 3 3 (1.5) 3 (1.5) (1.5) e.t Be ____________________________ 1.0 3.0 1. 7 (.5) (.5) (.5) (.5) (.5) (.5) .5 Ag (A) ________________________ Hg .55 (.1) .S!J .6 .45 .55 (.1) (.1) (.1) .S!J (A) ________________________ .30 .12 .19 .14 (.005) .10 .20 .12 .04 .06.1, Au (A) ________________________ .20 (.01) .OJ, (.01) (.01) (.01) .02 .02 .06 .017 

~ 

1:\:) 

C':l 

t:_%j 

0 

0 

::q 

t:_%j 

~ 1-1 

0 

> t"" 

t:1 

1-1 

00. 

1-3 

~ 1-1 

td 

C! 

1-3 

1-1 

0 

.:Z 

~ t:_%j 

1-3 

> t"" 

.rn 

~ 

0 

t:_%j 

z 

?::: 

0 

1-d 

1-1 
GEOCHEMICAL STUDIES 43 

TABLE 11.-Metal content (in parts per million) of Moenkopi Formation 

mudstone samples collected from rocks underlying uranium deposits in 

the Chinle Formation 

[Samples are listed in order of decreasing grain size from left to right. Geometric mean values are italicized for contrast. Values in parentheses are below detection levels listed on p. 16. 

Analyses were by six-step spectrographic method, by J. L. Finley, except that analyses of 

the following were by atomic-absorption method: Cu(A) and Ag(A), by A. J. Toevs and 

Lucy Dickson; Hg(A), by W. W. Janes] 

Standard deviation ----------------------------- 2.33 1.97 2.24 2.11 Geometric 

Median grain diameter (mm) __________ 0.013 0.013 0.005 0.0036 mean Sample No ___________________________________________ L1813 L1814 L1826 L1827 

Ca. _____________________________________________ 700 1,000 500 300 569 Fe ______________________________________________ 70,000 20,000 50,000 15,000 32,010 Mg _____________________________________________ 3,000 3,000 5,000 5,000 3,873 TL ______________________________________________ 2,000 3,000 2,000 3,000 2,449 Ba ______________________________________________ 500 500 300 300 387 

Mn _____________________________________________ 70 100 300 30 89 Sr _______________________________________________ 500 500 1,000 700 647 Zr _______________________________________________ 100 150 100 100 111 

y ________________________________________________ 150 100 100 150 122 

Cr _______________________________________________ 70 70 70 70 70 

Cu (A)--------------------------------------- 250 1,100 950 35 309 Cu ______________________________________________ 200 700 700 200 374 

y ________________________________________________ 30 70 70 500 93 Pb ______________________________________________ 30 50 15 15 24 N i_ ___________________________________ ----------- 30 70 100 20 45 

Co ______________________________________________ 10 100 70 3 21 Be ______________________________________________ 7 5 7 3 5.2 

Ag( A)-------------------------------------- (.1) (.1) (.1) (.1) .1 

Hg( A)-------------------------------------- .30 .55 .20 .11 .25 

Au (A)--------------------------------------· .06 .10 .46 .02 .09 

LOCALITY COMPARISONS 

In order to select the localities that yielded samples with the 

highest proportion of high metal values, data on metal content 

of the 323 samples from the Moenkopi and related strata at 76 

(reduced by "declustering" to 64) localities were sorted to obtain 

the sample localities containing the 32 highest values for each 

metal. Only analytically determined numerical values were used 

(for example, 30 values for Au (A) and 13 for Be). Adding available values for La, Mo, Nb, Sn, and W, not used previously in the 

study, the total number of values used in locality comparisons 

was 647. This number represents the approximate upper 10 percent of values; it was chosen arbitrarily to reduce the values to 

be considered to a manageable number. 

Using the number of high metal values found at each locality 

and the number of samples collected at each locality, it was possible to calculate the average number of high metal values per 

sample for each locality. These averages are shown as "values 

per sample" in table 12. Taking locality 60> in Arizona as an 

example, the four samples collected at this locality contain one 
44 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

of the 32 high values for each of the metals Ca, Fe, Cr, Cu (A), 

Cu, Y, Pb, Co and Ag(A) and two of the high values for Mn and 

Ba. Dividing the total of 13 high values by the number of samples 

(four) yields the average number of high "values per sample," 

3.25. 

To refine the "values per sample" result, the metals were divided 

into "primary" metals, including Ca through Zr (see table 12) 

and "secondary" metals, V through Zn. This division was a rough 

device to remove the effects of ( 1) carbonate and sulfate-bearing 

minerals and (2) some metals strongly related to detrital heavyA 

Mean metal content of 

siltstones (fig. 11, column C 

as a standard 

METALS (6 samples) 

Ca 

Fe 

Mg 

Ti 

Ba 

Mn 

Sr 

Zr 

v 

Cr 

Cu(A 

Cu 

) 

y 

Pb 

Ni 

Co 

Be 

Ag(A 

Hg(A 

Au(A 

) 

) 

I 

I 

I 

I 

26,000 

12,000 

7,400 

900 

350 

330 

80 

57 

40 

38 

14 

11 

14 

10 

7.0 

3.2 

0.5 

0.15 

0.13 

0.016 

I I I 

< 0.03125 

-

-

I I I 

B 

Mean metal content of 

enriched mudstone in 

terms of column A 

(4 samples) 

I I 

I I 

I I I 

I I 

0.25 0.5 1.0 0.25 0.5 1.0 2.0 4.0 8.0 16.0 32.0 64.0 

GEOMETRIC MEAN, GEOMETRIC RATIOS 

IN PARTS PER MILLION 

FIGURE 12.-Comparison of metal content of four metal-enriched mudstones 

with average metal content of the six siltstones of table 10 and figure 11, 

column C. All values compared are geometric means. A, Mean metal content of siltstones, table 10, used as a standard of comparison; B, mean 

metal content of metal-enriched mudstones, in terms of column A. 
TABLE 12.-Distribution by locality of the 32 highest values for each of the 20 metals used in the present study, and additional 

valid values available for La, M o, Nb, Sn, and Zn 

[Leaders ( ____ ) in figure columns indicate an absence of high values of the metal in samples collected at the locality] 

Staie ___________________ Arizona Colorado - Locality Nos. in table 4 ___ 1 5 9 10 12 15 60 70 81 210 211 400 3 4 8 15 401 Number of samples _______ 3 2 5 3 3 5 4 4 4 5 4 2 2 2 6 18 

Primary sedimentary rock metals 

Ca __________________________________ 1 

Fe __________________________________ 1 ------------------ 1 ------------------------------------------ 4 3 

~~ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -i----= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -i----= = = = = = = = = = = = ~ Mn ___________________ ----- _____________________ 1 ______ 2 

Ba---------------------------------- 1 1 1 ______ 2 1 Sr ---- _ --- __________________ ------ ________________________________ 2 Zr ____________________________ 1 __________________ 1 

Secondary sedimentary rock metals 

Cr v ----------------------------------------------------------------------------- 1 ______________ ------- ___ -------- __________________________ 1 _______ _ 

Cu(A>------------------------------------------------------ Cu _________________________________ 1 __________________ 1 1 ------ 2 

y __________________________________ 2 ------------------ 1 

Ph--------------------------------------------- 1 ------ 1 

NL _________________ ---- ____________ 1 

Co _____ ---- ________________ ------- __ 1 

Be__________________________________ 1 Ag (A) ___________________ - ______ -----_----

Hg (A) _____ ------ __ -----_-----_----------- Au(A) ____ ----- _____ ------ __ ------ __ 1 

2 

1 

1 

2 

-=====-i 

18 139 

189 4 2 

186 188 400 

1 2 17 

------ 1 

3 

1 

2 

1 

2 

2 

1 

3 

1 

2 

3 

1 

La _________ ------------ _____ ------------ __ -------- __________________________________________________________ 1 1 __________________ 1 _____ _ Mo _____ ---------------- ____________ ------ ___________________________________________________________________________________________________________ _ Nb ___________________________ ---- ___________________________________________________________________________________________________________________ _ 

Sn _____________________ ------------------- ______________ ----- _________ ----- _______________ -------- ___________________________________________________ _ Zn ___________________________________________________________________________________________________________________________________________________ _ 

Values per sample ________ 0.0 0.5 2.2 1.67 1.0 0.2 3.25 1.0 0.5 0.6 1.75 2.0 3.5 1.5 3.0 1.89 0.75 1.5 1.0 4.0 1.71 

Secondary ratio __________ 0 0 1.40 1.00 0.33 0 1.75 0 0.50 0.40 1.25 2.00 2.0 1.00 1.83 0.66 0.75 1.00 1.00 2.50 1.06 

l:;') 

trj 

0 

C":l 

::z:: 

t_:%.1 

a= 

1-f 

C":l 

> t"'4 

00 

1-3 

q 

t:l 

1-f 

trj 

00 

w::.. 

Ol 
TABLE 12.-Distribution by locality of the 32 highest values for each of the 20 metals used in the present study, and additional 

valid values available for La, Mo, Nb, Sn, and Zn-Continued 

State __________________ Nevada New Mexico Utah 

Locality Nos. in table 4 ___ 1 1 3 16 20 6 7 8 9 10 11 14 18 22 305 -- ---------- ---------------- Number of samples _______ 3 3 2 3 3 4 2 7 5 9 5 8 5 4 

Primary sedimentary rock metals-Continued 

Ca ___________________________ _ Fe ______________________ 1 

Mg _____________________ 1 

TL _____________ ------- _ 1 

Mn __________ - _ -- __ ---- ___________ - ______ _ Ba __________________________________ 1 2 Sr ___________________________________________________ _ 

Zr ______________________ 1 

Secondary sedimentary rock metals-Continued 

------ 2 

Cr _____ - ___ - __________________________________________ 1 __________________ 1 _______________________ _ 

Cu(A) ______________________________________________________________________________ 1 1 

Cu _____________________ 1 ------------------------ 1 ------------------------ 1 3 

y---- Pb ________________________________ ------------------------------------------------------------------------------------------ ------ _______________________________________________________ _ 

25 2!) 27 

8 3 2 

28 

4 

2 

1 

2 

2 

NL _____________________ 1 ------------------------ 1 ______ 1 1 ------------ 3 ------------------------------------ 2 

29 30 32 200 326 

8 8 9 

1 

2 

2 

2 

2 

1 

4 

3 

CO-------------------------------------------------------------~-- Be ___________________________________________________________________________________________________________________________________________________ 3 2 ------------ 3 ------------------------------------ 2 ------ _ 

Ag(A)------------------------------------------------------------- 2 ------------ 1 1 ------ 2 ------------------ 1 ------------ 1 Hg(A>------------------------------------------------------ 1 ------------ 1 ______ 1 ------------ 1 ------ 2 Au(A) __________________ 1 ------ 1 2 ------------ 1 ------------ 1 ______ 3 ______ 2 1 ------ 1 

Mo La---------------------------------- ________________________________________________________________________________ 1 ------------------------ 1 _ Nb ________________________________________________________________________________________________________________________________ _ Sn__ _ _ _ _ _ _ _ _ _ _ ___ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 Zn ___________________________________________________________________________________________________________________________________________________ _ 

Values per sample ________ 2.67 0.67 1.5 1.67 0.0 1.5 2.0 1.29 1.4 0.89 1.40 2.50 1.40 2.25 1.75 1.33 1.50 1.25 2.38 0.13 3.11 

Secondary ratio__________ 1.33 0 1.00 0.67 0 0.75 1.00 1.00 0.80 0.56 0.80 2.25 0.60 1.25 0.88 0.67 1.50 0.50 1.50 0.13 1.89 

~ 

~ 

c;i 

t?:l 

0 

0 

::t:: 

t?:l 

~ ~ 

0 

> 

t-t 

tj 

~ 

[/). 

1-:3 

~ ~ 

t:d 

c::: 

1-:3 

~ 

0 

~z 

~ 

t?:l 

1-:3 

> 

t-t 

!fl 

~ 

0 

t?:l 

z 

~ 

0 

""d 

~ 
State __ Utah-Continued -----34 49 309 325 Locality Nos. in 33 173 35 36 38 41 43 

160 45 47 313 64 286 300 304 307 400 310 312 319 323 401 402 table 4. 248 315 

Number of samples_ 3 10 5 2 6 2 6 2 18 17 10 2 

Primary sedimentary rock metals-Continued 

Ca ____________________________ 1 __________________ 1 9 ------ 3 Fe---------------------------- 1 ______ 2 ______ 1 1 2 2 Mg _______________________________________ 1 ______ 3 6 ------ 4 Ti_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 _ _ _ _ _ _ 2 1 2 2 

Mn __________________________ _ Ba __________________________ _ Sr _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 Zr ________________ 1 

Secondary sedimentary rock metals-Continued 

v --- Cr _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 _ _ _ _ _ _ 2 

Cu(A) ________________________ 2 Cu _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 

y ---------------------------- 3 Pb ______________________ 1 1 

Co NL_-------------------------- ___________________________ _ 

Be ______________________ 1 1 

Ag(A) ----- _______________________________ _ Hg(A) __________________ 5 ------ 1 

Au(A) ___ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 

La _______________ 1 ------ 1 

Mo_- Nb _ _ _ _------------------------------------------------------------ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 

5 

4 

3 

4 

1 

1 

2 

8 3 2 

1 

2 

1 

3 

2 

1 

1 

1 

3 

1 

9 5 

1 

1 

1 

1 

1 

------

2 

Sn ____________________________________________________________ -- _ ------ _ ------------------------------------------------------------------ Zn ____________________________________________________________________________________________ - __ - _ _ _ _ _ _ _ _ _ _ 1 

Values per sample __ 1.0 1.0 4.60 1.50 3.50 1.00 1.5 1.0 2.89 1.82 3.5 1.0 0.5 0.0 2.4 6.88 5.33 1.5 2.0 0.0 3.11 1.5 

Secondary ratio ____ 0.67 0.90 3.00 0.50 2.67 0.50 0.50 0.50 1.28 1.29 1.70 1.00 0.50 0 1.00 5.50 3.67 0.5 1.0 0 2.11 1.2 

C1 

tr.l 

0 

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toot 

w 

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d 

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w 

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48 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

mineral suites, and to obtain a ratio weighted in favor of the 

higher values of rarer metals. This ratio, designated the "secondary ratio" (table 12) was computed using only the secondary 

metals and the number of samples. In the example of locality 60, 

there are seven "secondary" metals, which divided by the number 

of samples (four) yields a "secondary ratio" of 1.75. 

The calculations of the "values per sample" and the "secondary 

ratio" were made to obtain numerical measures which can be 

used to rank the sample localities in terms of high metal occurrence. 

In table 13, the 16 localities (upper quartile) with the highest 

TABLE 13.-Localities that contain the 16 highest values per sample, and 16 

highest secondary metals ratios 

[Localities are listed in approximate order of highest to lowest ratios. Locality names and 

numbers (in parentheses) are those listed in table 4] 

Localities that contain 16 highest 

values per sample 

*Deer Flat, Utah (309) 

**Mineral Canyon, Utah (310) 

North Sixshooter Peak, Utah (35) 

Skull Creek, Colo. (188) 

Steer Mesa, Utah (38) 

Pleasant Creek, Utah (64) 

Sheephorn Creek, Colo. ( 3) 

Holbrook, Ariz. (60) 

*Shinarump No.1 mine, Utah ( 401) 

Lockhart Canyon, Utah (32) 

St. George "A," Utah ( 47) 

Horse Spring Valley, Nev. (1) 

**Silver Falls, Utah (14) 

Farm Creek, Utah (307) 

Hite, Utah (29) 

Kanarraville "A," Utah (22) 

*Mine nearby. 

**Mining activity in area. 

Localities that contain 16 highest 

secondary ratios 

*Deer Flat, Utah (309) 

**Mineral Canyon, Utah (310) 

North Sixshooter Peak, Utah ( 35) 

Steer Mesa, Utah ( 38) 

Skull Creek, Colo. ( 188) 

**Silver Falls, Utah (14) 

**Shinarump No.1 mine, Utah (401) 

Sheephorn Creek, Colo. ( 3) 

**Nakai Dome, Ariz. (401) 

Lockhart Canyon, Utah (32) 

Gateway (The Palisade), Colo. (8) 

Holbrook, Ariz. ( 60) 

Pleasant Creek, Utah (64) 

Hite, Utah (29) 

Comb Wash, Utah (27) 

Horse Spring Valley, Nev. (1) 

"value per sample" measures and with the highest "secondary 

ratio" measures are listed separately and in order of decreasing 

amounts. The secondary metals list contains three localities different from the total metals list. All 20 localities are shown in 

figure 13. 

GOLD 

Surprisingly, 101 samples from the Moenkopi Formation contain Au (A) detectable at the 0.02-ppm detection level. The Tenderfoot Member is slightly high in Au (A), and the Hoskinnini, 

Holbrook, and Wupatki Members and lower red member are 

slightly low. Au (A) is definitely high in the metal-enriched mudstones below the Chinle-Moenkopi contact and in some localities 
GEOCHEMICAL STUDIES 49 

3 

Glenwood Springs 

COLORADO 

36° I 

', t -;;. NEW MEXICO ~ 

"': q<G Albuquerq\le 

~ \ .. ~ 

60 

ARIZONA ~ 

0 ./i>zi-e,.. J r.x.. 

34° ::s 

< u 

0 100 200 MILES 

EXPLANATION 

0 

Sample locality having one of 16 highest 

metal values per sample 

Based on primary plus secondary sedimentary-rock-metals content (tables 12 and 

13} 

22 

Sample locality number, by State 

* Known uranium deposits in close vicinity 

• Sample locality having one of 16 highest 

metal secondary ratios 

Based on secondary sedimentary-rockmetals content (tables 12 and 13} 

With the exception of localities 8 (Colorado), 27 (Utah), and 401 (Arizona), 

these are also sample localities having 

one of 16 highest metal values per 

sample 

FIGURE 13.-Sample localities having the largest average number of high 

metal values per sample. Data from tables 12 and 13. Sample locality numbers are those listed in table 4. 

below known uranium deposits. It is high in claystones and low 

in coarse sandstones. Au (A) was found to have a significant 

positive geochemical association with Fe, Cu, Cu (A), V, and Co 

in Moenkopi rocks (fig. 10). The highest detected amount of 
50 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

Au (A), 0.70 ppm, is in a limestone (Thaynes Formation) sample 

from Farm Creek, Utah (locality 307). Because of the highly 

censored nature of the Au distribution, I could not compute statistical measures that would show the full range of variation in 

Au values among different members, facies, and textures. 

A chi-square test of the regional distribution of the samples 

containing detectable Au (A) using a previously described method 

(Cadigan, 1962) and seven arbitrarily selected areas yielded a 

probability of randomness of less than 0.01, an indication that 

the regional distribution of Au (A) in the Moenkopi is not random. 

The main source of deviations from randomness resulted from a 

deficiency of Au (A) in the salt anticline area in the southeastern 

Utah-southwestern Colorado border area and an excess of Au (A) 

in the area including the southern and southeastern flanks of the 

Uinta Mountains uplift and associated structures in northeastern 

Utah and northwestern Colorado. 

SUMMARY AND CONCLUSIONS 

The Moenkopi Formation of Triassic(?) and Early and Middle 

Triassic age and contiguous lithologically related strata constitute one of the red-bed units of the Colorado Plateau region. The 

Moenkopi is the basal unit of the Triassic stratigraphic sequence 

in the west two-thirds of the region. Unconformities are present 

at the lower contacts with several different Permian formations 

and at its upper contact with the Chinle Formation. 

The Moenkopi was deposited on a slowly subsiding plain within 

environments which ranged from alluvial on the east to marine 

on the west. Tectonic activity in the source areas, the Uncompahgre highland of Colorado, and highlands in southern Arizona 

and New Mexico ranged from quiescence to slow uplift. Minor 

volcanic activity occurred in the western Uncompahgre highland 

and in highlands in what is now the southern Arizona-New Mexico 

border area. 

Lack of sediment from the source areas during periods of 

quiescence allowed marine environments to migrate eastward 

across the subsiding plain into the central parts of the region. 

The marine invasions are marked by the presence of marine 

clastic limestones and by marginal marine gypsum evaporite 

deposits, particularly in the western part of the region. 

The Moenkopi is composed of sediments eroded from relatively 

low-lying weathered terranes of granitic, low-grade metamorphic, 

sedimentary, and minor volcanic rocks, and of marginal marine 

gypsum deposits and marine limestones. Diagenetic changes oc-
SUMMARY AND CONCLUSIONS 51 

curred which probably further altered many of the detrital minerals, particularly the feldspars and the ferromagnesian "heavy" 

minerals. Most of the clays are recrystallized and represent the 

combined products of alteration in the source area and postdepositional diagenesis. 

The Moenkopi has been divided into numerous members, none 

of which is recognized as extending throughout the region. Each 

seems to be related to a specific source area or to an interval of 

marine or marginal marine deposition. The members are generally 

conformable. 

The analytical data for this study were obtained from 323 rock 

samples from 64 localities. Data were sought on 33 metals. 

Analyses were done by the six-step spectrographic method for 

32 of the metals and by atomic-absorption methods for four of 

the metals-gold, silver, copper, and mercury. Sufficient valid 

data for statistical analysis were obtained for only 18 metals 

(counting spectrographic and atomic-absorption analyses for copper as two different metals). Gold and beryllium data are severely 

censored and most of the samples contain amounts below the 

level of detection, but, because of special interest in these metals, 

they are considered in addition to the other 18 metals in the 

statistical study. 

The 20 sets of metal values used in the study are, in order of 

geometric mean abundance in the Moenkopi Formation as a whole, 

Ca, Fe, Mg, Ti, Ba, Mn, Sr, Zr, V, Cr, Cu (A), Cu, Y, Pb, Ni, Co, 

Be, Ag (A), Hg (A), and Au (A). 

The statistical distributions of 13 metal values are essentially 

log normal and five (Ni, Sr, Mg, Ba, and Cr) are not. Pb, Be, and 

Y distributions exhibit the lowest variances, and Zr, Cu (A), Cu, 

Hg(A), Ca, Mg, and Ba, the highest. 

Metal content in the Moenkopi and related lithologic units 

varies significantly, mainly because of the difference in source 

of rock components. Largest differences observed are between 

units derived predominantly from a marine source (the sea) and 

units derived predominantly from terrestrial sources. Metal content of the marine and marginal marine members of the Moenkopi (the Shnabkaib, Virgin, Sinbad, Timpoweap, and lower red) 

and of the Thaynes Formation, compared with geometric means 

of metals in the Moenkopi Formation as a whole, is markedly 

and significantly low. The characteristic exceptions are much 

higher values for Ca, Mg, and Sr. Individual metals that are 

lower in marine rocks by approximately an order of magnitude 
52 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

are Fe, Ti, Ba, Mn, Zr, V, Cr, Ni, and Co. These metals are derived 

chiefly from terrestrial sources. 

The next lower order of differences in metal content among 

members was related to different terrestrial sources. These differences were observed specifically between the Tenderfoot Member 

and the Holbrook and Wupatki Members and between the Tenderfoot and Hoskinnini Members. 

The Tenderfoot Member, a continental alluvial arkosic lithologic unit, was derived from the western slope of the Uncompahgre highland in western Colorado. The Holbrook and Wupatki 

Members are continental alluvial units derived from the southern 

highland sources of Arizona and New Mexico. The metal content 

of the Tenderfoot is conspicuously and significantly higher than 

that of the other two members. Mg is higher in the Tenderfoot 

by more than two orders of magnitude, an indication of a major 

difference in composition between the two terrestrial source areas. 

The Hoskinnini Member, also a continental alluvial arkosic 

unit, was derived from sources in southwestern Colorado and 

northern Arizona. Compared with the Tenderfoot Member, it is 

significantly lower in metal content, but abundances of individual 

metals for both units fall into the same order of magnitude. Differences are attributed to minor differences between similar 

sources. Compared with the formation geometric means, the 

Hoskinnini is slightly but significantly lower and the Holbrook 

and Wupatki are markedly and significantly lower in metal content. The Tenderfoot is slightly but significantly higher. 

A third order of differences in metal content among the units 

was related to metal contributions by interstratal solutions. These 

differences were observed specifically in comparisons of the 

geometric mean metal values of the upper slope-forming and 

cliff-forming members with those of the Moenkopi as a whole, 

and with the Tenderfoot and Hoskinnini Members. The upper 

slope-forming and cliff-forming members were derived from the 

same sources as the Tenderfoot and Hoskinnini ; they are significantly higher in metal content than both the formation as a whole 

and the Hoskinnini. They are not significantly higher in metal 

content than the Tenderfoot, but they are conspicuously higher 

in specific metals that are related to ore deposits in the overlying 

Chinle Formation. The metals with higher-than-expected abundances are: Cu (A), Cu, Co, Hg (A), V, and Sr. Increments of 

these metals were contributed to the upper strata of the upper 

slope-forming and cliff-forming members by solutions migrating 
SUMMARY AND CONCLUSIONS 53 

along the overlying unconformity between the Moenkopi and Chinle 

Formations. 

A fourth order of difference is that which occurs within the 

units and which is attributed to variation in facies. Facies are 

defined in terms of a combination of particle size and composition. 

Comparisons were made among the siltstone-sandstone facies 

(the dominant one), the sandstone facies, the limestone-evaporite 

facies, and the Moenkopi and related lithologic units as a whole. 

The siltstone-sandstone facies is significantly higher in metal 

content than all the units as a whole, and higher but not significantly so than the other two facies. No magnitude differences 

exist for individual metal abundances among all the units as a 

whole, the sandstone-siltstone facies, and the sandstone facies. 

Magnitude differences in metal content between the limestoneevaporite facies and the other facies occur, but they are differences related to the marine source of the limestone-evaporite 

facies rather than to variation in only particle size and composition. 

Comparisons among four groups of samples, representing coarse 

sandstones, fine sandstones, siltstones, and claystones, show decreases in Ba with decrease in grain size, and gradational increases 

in Ti, V, Cr, Y, Ni, and Au. The gradational increases are the 

result of increasing proportions of heavy minerals which, in the 

Moenkopi, show greatest concentration in the very fine sand and 

very coarse silt sizes. In a suite of rocks composed of 50-97 percent carbonates, Sr, Ti, Ba, Zr, V, and Cr decrease in quantity 

as percent carbonates increase. Mg shows an increasing trend; 

Ca values should show an increasing trend, but they do not because proportions exceed the discriminating capability of the 

analytical method. Y, Pb, Be, Au, Ni, and Co were present in 

quantities too close to their detection level to show any trend. 

Coefficients of association computed for all possible pairs of 

the 20 metals studied contain 11 significant negative coefficients 

and 56 significant positive ones. The negative associations around 

the metals Ca, Ag (A), Hg (A), and Sr are related directly or 

indirectly to a major negative relationship of proportion of marine 

sediments to proportion of terrestrial sediments. 

The significant positive coefficients come from 14 metals which 

form a positively associated group: Fe, V, Cu, Cu (A), Co, Ti, 

Cr, Y, Ni, Ba, Zr, Mn, Be, and Au(A); these, with the exception of 

Ba, are related directly or indirectly to sediments derived from 

terrestrial sources. All were probably contained in the original 

detrital heavy minerals. Mg, Sr, Pb, Hg (A), and possibly Ca form 
56 GEOCHEMICAL DISTRIBUTION, METALS, MOENKOPI 

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U.S. Geol. Survey Misc. Geol. Inv. Map I-300, 33 p. 

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deposits-A preliminary report: U.S. Geol. Survey Bull. 1147-E, 57 p. 

---1967, Methods of computation for estimating geochemical abundance: 

U.S. Geol. Survey Prof. Paper 57 4-B, 15 p. 

Miesch, A. T., and Riley, L. B., 1961, Basic statistical measures used in 

geochemical investigations of Colorado Plateau uranium deposits: Am. 

Inst. Mining, Metall., and Petroleum Engineers Trans., v. 220, p. 247-251. 

Myers, A. T., Havens, R. C., and Dunton, P. J., 1961, A spectrochemical 

method for the semiquantitative analysis of rocks, minerals, and ores: 

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fru.s. GOVERNMENT PRINTING OFFICE: 1971 0-438-746