Botanical Prospecting for 

Uranium on La Ventana 

Mesa, Sandoval County 

New Mexico

GEOLOGICAL SURVEY BULLETIN 1009-M

This report concerns work done on behalf 

of the U. S. Atomic Energy Commission 

and is published with the permission of 

the Commission

Botanical Prospecting for 

Uranium on La Ventana 

Mesa, Sandoval County 

New Mexico

By HELEN L. CANNON and W. H. STARRETT

A CONTRIBUTION TO THE GEOLOGY OF URANIUM

GEOLOGICAL SURVEY BULLETIN 1009-M

This report concerns work done on behalf 

of the U. S. Atomic Energy Commission 

and is published with the permission of 

the Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1956
UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

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

Washington 25, D. C. - Price 15 cents (paper cover)
CONTENTS

	Page 

Abstract________________________________________________________ 391

Introduction._ ____________________________________________________ 391

Methods and extent of work________________________________________ 394

Results____.--___._-___.-_..___.____--__-._--_-__--.____-._-___. 399

Chemistry of coal__-___-_-___-_-_--_---__-_____________________ 399

Distribution of indicator plants__--____-___--__-_-__---__._____ 399

Absorption of uranium by tree cover.____________________________ 401

Summary and conclusions.________________-_-__-___-_--__-_____-__. 405

Literature cited.______________-_-___-_______-_---_____--__-__--__. 406

Index____________________________________________________________ 407

ILLUSTRATIONS

FIGUKE 58. Index map of part of New Mexico showing location of La

Ventana Mesa______________________________________ 393

59. Geologic map of the La Ventana area___________________ 394

60. Isogram map showing uranium content of live pinyon and

juniper branches from north butte of La Ventana Mesa_. 396

61. Isogram map showing uranium content of dead pinyon and

juniper branches from north butte of La Ventana Mesa__ 397

62. Isogram map showing uranium content of dead pinyon and 

juniper branches from part of south butte of La Ventana 

Mesa____._-_--___--------_---__------_-----------_-- 398

63. Probable areas of uranium-bearing coal, as interpreted from 

analyses of livewood and deadwood samples from north butte 

of La Ventana Mesa_____.__-_____-_-___-___--.__--___ 405

TABLES

TABLE 1. Chemical composition of coals from the La Ventana area..___ 400

2. Plant distribution data, La Ventana Mesa.________________ 401

3. Plant absorption data._-______-___-____-____-__-______-- 402

in

A CONTRIBUTION TO THE GEOLOGY OF 

URANIUM

BOTANICAL PROSPECTING FOR URANIUM ON LA VENTANA MESA, SANDOVAL COUNTY, NEW MEXICO

By HELEN L. CANNON and W. H. STARBETT

ABSTRACT

A uranium-bearing coal of the Allison and Gibson members (undifferentiated) 

of the Mesaverde formation of Late Cretaceous age crops out in erosional remnants 

of La Ventana Mesa, Sandoval County, N. Mex. Analyses of the coal show the 

uranium to be concentrated locally, along with minor accumulations of sulfur, 

selenium, chromium, copper, lead, cobalt, molybdenum, and nickel. It is believed 

that the metals have entered the coal along fractures in the overlying La Ventana 

sandstone member and that the source of the metals may 'have been Pliocene (?) 

Bandelier tuff of Smith (1937).

Plant distribution studies indicate that selenium- and sulfur-indicator plants, 

including species of Astragalus, Stanleya, several Crucifers, and Eriogonum, which 

grow on the slopes below the coal outcrop, may be useful in prospecting along the 

base of other mesas in the area.

On the buttes of La Ventana Mesa the coal is capped by a well-fractured 65-foot 

sandstone bed through which roots of a pinyon and juniper forest penetrate. 

More than 200 samples of branches of trees growing on top of the mesa were collected and analyzed for uranium. The assays ranged from 0.1 to 2.3 parts per 

million of uranium in the wood ash. Dead branches, which were found to contain 

more uranium in the ash than live branches, were sampled whenever possible. 

The resulting uranium values have been contoured to indicate probable areas of 

mineralized coal. Parts of the north butte are recommended as favorable for 

physical exploration.

INTRODUCTION

Geological studies were made by the Geological Survey in advance of 

exploration in an area of uranium-bearing coal on La Ventana Mesa, 

Sandoval County, N. Mex., as described by Bachman, Vine, Read, and 

Moore (in preparation). Prospecting by botanical methods was suggested by C. B. Read of the Geological Survey and was done on behalf 

of the Division of Raw Materials of the U. S. Atomic Energy Commission.

391
392

The purpose of the present investigation was to prospect for uranium 

by botanical methods in an area in which the uranium-bearing bed is 

under cover. The bed, known to be mineralized along parts of the 

outcrop, is overlain by the La Ventana sandstone member of the 

Mesaverde formation, a massive flat-lying sandstone 65 feet thick, 

which caps the mesa. Botanical prospecting was planned to study 

the metal constituents of the uranium-bearing coal; the relation of 

these constituents to plant distribution; the absorption of uranium 

by trees rooted in the sandstone capping; and the use of this information in prospecting.

The area studied includes the north butte and part of the south 

butte of La Ventana Mesa. The mesa lies just east of New Mexico 

Highway 44, 15 miles by road south of Cuba, and 65 miles by road 

northwest of Albuquerque, in sections 28, 29, 32, 33, and 34 of T. 19 

N., R. 1 W., New Mexico principal meridian (fig. 58). The two 

buttes are completely isolated from each other and rise about 1,400 feet 

above the valley floor. The shale and talus-covered slopes can be 

traversed only on foot except at the northwest corner of the north 

butte where it is possible to drive a jeep about one-third of the way 

up the slope. The area is drained and dissected by tributaries of the 

Rio Puerco, a part of the Rio Grande drainage system. The altitude 

ranges from 6,000 feet at the base of the mesa to 7,400 feet at the top. 

The climate is semiarid. The mean annual rainfall on La Ventana 

Mesa is 18 inches (Renick, 1931, p. 6-8).

La Ventana Mesa is composed of sedimentary beds and lies off the 

western flank of the granitic Nacimiento Mountains (fig. 58). Rocks 

exposed on the mesa belong to the Mesaverde formation of Late 

Cretaceous age. Uranium-bearing material is fOUIld in the upper 

carbonaceous shales and COal of the Allison and Gibson members 

(UDdifferentiated) of the Mesaverde formation; these form the body 

of the mesa. Overlying the Allison and Gibson members is 65 feet 

of porous, jointed La Ventana sandstone capping the buttes. According to Bachman, Vine, Read, and Moore (in preparation), a small 

flexure, the La Ventana syncline, plunges northwest, and its axis 

trends through the part of the mesa sampled. The flat-lying beds 

are steeply upturned within a few miles to tb& east where the more 

resistant beds form hog-backs wiucn parallel the Sierra Nacimiento. 

TKe structure described remained almost unchanged in Tertiary time. 

The area was probably once covered by the mildly radioactive tuffs 

of the PHocene(?) Bandelier tuff of Smith, (1937). It seems probable 

that uranium was dissolved by descending meteoric waters which 

percolated through the La Ventana sandstone member and was 

adsorbed by carbonaceous material in the underlying Allison and 

Gibson members. The geologic relations have been described by
BOTANICAL PROSPECTING FOR URANIUM, SANDOVAL CO., N. MEX. 393

FIGURE 58. Index map of part of New Mexico, showing location of La Ventana Mesa, Sandoval County,

N. Mex.
394 A CONTRIBUTION TO THE GEOLOGY OF URANIUM

Darton (1929), C. B. Read (written communication), and Bachman, 

Vine, Read, and Moore (in preparation), and are shown in a generalized 

way in figure 59. According to the last, the Bandelier tuff of Smith 

(1937) contains about 0.003 percent of uranium.

R.1W.

EXPLANATION

Mancos shale

Fault, dashed where inferred 

U, upthrown side; D, downthrown side

X

From unpublished material of J. D. Vine, 

U. S. Geological Survey

0

I I'

3 Miles

FIGTJBE 59. Geologic map of the La Ventana area, Sandoval County, N. Mex.

METHODS AND EXTENT OF WORK

i>i&nt cu^trikvtiorY studies were made, and coal and preliminary plant samples were collected m *&<> summer of 195.. ^et^iea

ampling was begun m the fall of 1952 and completed in tufi

of 1953 by Starrett.

Radioactive coal samples collected during previous studies made 

by Bachman, Vine, Read, and Moore (in preparation) were reanalyzed 

to determine the minor metal content, and, for comparison, a barren
BOTANICAL PROSPECTING FOR URANIUM, SANDOVAL CO., N. MEX. 395

coal sample was collected from the same bed at a distance of several 

miles and analyzed.

Plants were collected at six stations: near the outcrop of uraniferous coal, on the talus slopes below the coal on each butte, and 

at the nonuraniferous La Ventana coal mine. E. F. Castetter of the 

University of New Mexico aided in plant identification.

The method of prospecting used was the collection of livewood and 

deadwood samples of branches of pinyon and juniper, and a few 

samples of mountain mahogany, for fluorimetric uranium analyses. 

The buttes of La Ventana Mesa are covered with a thick growth of 

pinyon and juniper, which are known to be excellent absorbers of 

uranium. These trees are phreatophytes; that is, they "habitually 

obtain their water supply from the zone of saturation either directly 

or through the capillary fringe" (Meinzer, 1923, p. 95). The uraniumbearing coal at the base of the sandstone acts as a perched zone of 

saturation and contains the water supply on which the trees depend. 

Live juniper roots have been observed in mines at depths of several 

hundred feet. Whether the tree roots on La Ventana Mesa actually 

penetrate to the coal or whether there is sufficient upward migration 

of water and soluble salts in the capillary fringe to support root 

growth is not known. At least the roots have worked down through 

joints and fractures of the La Ventana sandstone member and sufficient uranium has been absorbed by the trees to be detectable in the 

trunk, limbs, and branch tips (Cannon, 1952).

For this study, a sample consisted of 6-inch unpeeled sections of 

either livewood or deadwood branches collected from the quadrants 

of the tree. Detailed sampling on a grid pattern with a 100- to 200- 

foot spacing was originally planned on the advice of G. 0. Bachman 

to cover only the western part of the north mesa which was considered 

to be most favorable for mineralized ground. Later it was decided 

to include widespaced and admittedly incomplete coverage of the rest 

of the mesa in order to round out the picture. In all, 90 livewood 

(fig. 60) and 103 deadwood (fig. 61) samples were collected to cover a 

large part of the north butte, and 13 deadwood samples were collected 

on a thin extension of the south butte known to be mineralized (fig. 

62). The samples in sees. 29 and 32 were collected in November 1952, 

and the rest in April 1953. The assays for each tree were plotted on 

maps of the buttes, and the values contoured with an isogram interval 

of 0.5 ppm of uranium (figs. 60, 61, and 62).

The samples were analyzed by an extraction fluorimetric method 

by C. Huffman and G. Burrow of the U. S. Geological Survey. By 

this method, the samples are ground, ashed, digested in nitric acid, 

and the solution extracted hi ethyl acetate. After evaporation, the 

residue is analyzed fluorimetrically for uranium.

355398-66 2
396 A CONTRIBUTION TO THE GEOLOGY OF URANIUM

T.I9N., R.IW.

SECTION 29

EXPLANATION

X 0.l

Uranium content, in parts per 

million, of live branches

60 

I

Uranium content, in parts per 

million, of coal samples. (From 

unpublished material by J. D. Vine)

'BIO

SECTION 33

1.0 -

Isogram lines solid where drawn

points and dashed where pattern

inferred from deadwood samples

Isogram interval 0.5 ppm of uranium

500 2000 F«t

FIGURE 60. Isogram map showing uranium content of live pinyon and juniper branches from north butte

of La Ventana Mesa.
BOTANICAL PROSPECTING FOR URANIUM, SANDOVAL CO., N. MEX. 397

T.I9N..R.IW.

SECTION 29

Sompled November | Sampled April

irts per 

nches

60

1000

3000'

370'

SECTION 32 SECTION 33

Uranium content, in parts per 

million, of coal samples. (From 

unpublished material by J. D. Vine)

Isogram lines solid where drawn 

proportionally between control 

points and dashed where pattern 

inferred from livewood samples

Isogram interval 0.5 ppm of uranium

FIGURE 61. Isogram map showing uranium content of dead plnyon and juniper branches from north butte

of La Ventana Mesa.
398 A CONTRIBUTION TO THE GEOLOGY OF URANIUM

730

750

T.I9N..R.I W.

SECTION 33 SECTION 34

820 440 n'o

Probable area of mineralized ground-inferred 

' from analyses of tree branches

1.8 

x

820

Uranium content, in parts per 

'million, of coal samples. (From 

unpublished material by J. D. Vine) 

____ 15 ____

Isogram interval 0.5 ppm of uranium

FIGURE 62. Isogram map showing uranium content ot' dead pinyon and juniper branches from part of
BOTANICAL PROSPECTING FOR URANIUM, SANDOVAL CO., N. MEX. 399

RESULTS

The problem of prospecting La Ventana Mesa for uranium is one 

of prospecting a barren sandstone mesa top for favorable areas in an 

underlying coal bed which can only be sampled around the rim. 

Analysis of samples from the mesa top was therefore chosen as the 

primary method of prospecting, and only a cursory study of the coal 

and its effect on the plant ecology of the talus-covered slope was made..

CHEMISTRY OP COAL

Coal is considered by Bachman, Vine, Read, and Moore (in preparation) to be mineralized when it contains more than 100 ppm of uranium; the mineralized parts of the coal bed contain from 100 to; 

6,200 ppm (0.01 to 0.62 percent) of uranium and the barren parts of 

the coal average about 20 ppm of uranium. The elements associated 

with uranium in the mineralized coal compared to barren coal are 

shown in table 1. The ratio of selenium, to uranium is very high in. 

mineralized coal. Chromium, copper, lead, cobalt, molybdenum, 

nickel, and sulfur also occur in greater amounts in the uranium-bearing 

coal than hi barren coal. Although these elements are concentrated 

in several types of deposits, the argument that they may be of volcanic 

origin is strengthened by the fact that anomalous amounts of the same, 

suite of metals occur in three samples of glass collected in the Jemez 

volcanic field (R. S. Cannon, oral communication). :

DISTRIBUTION OF INDICATOR PLANTS

The selenium and sulfur in the coal have affected the plant ecology 

of the slopes below the coal outcrop. Plants noted in study areas 

are listed in table 2. Few plants grow along the actual outcrop 

of uranium-bearing coal and these are limited to a few genera known 

to be tolerant of uranium ore deposits. Euphorbia, Atriplex, Mentzelia, and Stanleya were seen. Aster tenacetifolius is also abundant. 

In addition, two species of Astragalus associated with several Crucifers 

and an Eriogonum appear on the slopes and along the drainage channels below the uranium-bearing outcrop. Though these Astragalus 

species have not been proved to be selenium indicators, their presence 

here is significant and their association with the sulfur indicators 

listed is suggestive of mineralized ground. It is possible that these 

plants which extend far down the slope below the coal outcrop may be 

useful in prospecting along the base of other mesas in the area.
400 A CONTRIBUTION TO THE GEOLOGY OF URANIUM

.

Ch

TAB

(Ca, yses 

a

bo

2

o

^H

0

O

d 

O

O

£

ca 

O

CO

9 

OS

P

P

1

1

 §.

00

£££

£c£

§88 o ' '

rSrS o 

OOO

O

MMM 

o ' '

MMM 

888

d

§88

o

M

MMM o ' '

>ONi-l c>5 cx>o

888

o

§

w 

OO

6

^JtOg

080

o

Uranium-bearing station coal, 41 

(flg.62). 

sandstone... 8-ia ------ 

impure coal.--- 7-in. _..--- shale carbonaceous 6-in.--------- station coal, 44Uranium-bearing 

Mo 

i^o

££

MM 

88

88

8§

MM 

88

MM 

88

MM

Mo 'M

*.% .

ss

*N

l«

(ng. e^.)

sandstone.. - carbonaceous 5-in.

3.5-in. impure coal.- 

mine Ventana colfrom La Barren stations 59) horizon (Samefie. as 

S

£

£

^"

s

|

M

£

s

 o

i

CO

0

 *
BOTANICAL PROSPECTING FOR URANIUM, SANDOVAL CO., N. MEX. 401

TABLE 2. Plant distribution data, La Ventana Mesa, Sandoval County, N. Mex. 

[s, selenium indicator plant; cs, calcium sulfate indicator; no, not observed; o, observed]

Plant name

Qramineae:

Oryzopsis Itymenoides (R & S) Rick (ricegrass) ...

Pihaceae: 

Juniperus monosperma (Engelm.) Sarg. (juniper).

Onetaceae:

Euphorbiaceae: 

Euphorbia fendleri Torrand Gray (sandmat). _ 

Cbenopodiaceae: 

Atriplex confertifolia (T & S) S. Wats, (shadscale).

Rosaceae:

Cruciferae: 

Lesquerella gordoni (A. Gray) S. Wats, (bladderpod)...........................................

Capparidaceae:

Polygonaceae:

Loasaceae: 

Ment'zeliasp. (stickleaf)... ___________

Leguminosae:

Compos! tae:

Control 

indicated

s

cs

cs 

s, cs 

. cs

cs 

cs

B(T)

s(?)

At base of 

mineralized coal

no 

o 

no 

no

no 

no

no

0 

0

no 

no

no 

no

0

no 

no 

no

0

no 

no

no 

no 

no

0

On talus below 

mineralized coal

South 

butte

no 

no

0 

0

no 

no

no

0

0 

0 

0

0

no 

no

0 

0 

0 

0

0 

0

o

0 

0

o

North 

butte

no

0

o 

o

0 

0

0 

0 

0

no

0

o

0 

0

o 

no

0 

0

o

0

no

0 

0

no

At base 

of barren 

coal

0

o

0 

0

o

0

no 

no

0

no 

no

no

no 

no 

no

o

0

no

no 

no

no 

no 

no 

no

ABSORPTION OP URANIUM BY TREE COVER

Trees rooted directly in barren coal were found by preliminary 

analyses to contain less uranium in the ash than trees growing over 

sandstone capping and rooted in underlying mineralized coal. The 

samples were collected on both buttes where uranium-bearing coals 

occur, and, for comparison, from nonuraniferous coal in the same bed 

exposed at the La Ventana coal mine several miles distant. A few 

preliminary samples were taken for information on variations in 

uranium content between livewood and deadwood of juniper (Juniperus monosperma), pinyon (Pinus edulis), and mountain mahogany
A CONTRIBUTION TO THE GEOLOGY OF URANIUM

(Cefcocarpos montanus Raf.). The results are shown in table 3. It 

must be remembered that the uranium content detected in the 

branches has been raised through 65 feet of root system and 10 feet of 

trunk and therefore is not large. Basic work (Cannon, 1952, p. 743) 

has shown that much of the uranium absorbed by the roots is precipitated within the root near the point of intake and that the uranium

TABLE 3. Plant absorption data, La Ventana Mesa 

|Analysts: E. J. Fennelly and Claude Huffman, U. S. Geological Survey]

Location and kind of tree

Samples collected on South butte 

(fig. 62) 

Juniper, above station 44

Pinyon, above station 44_ _

 Juniper/ 'above station 41_____

Mountain mahogany, above

station 41. 

Do______. ______________

Traverse on North butte (figs. 60 

ami 61) ; ' 

1. Pinyon, above station 2____

Do _ .._.__..-._.._. _

2. Mountain mahogany, 50

ft south of no. 1. 

Do.. ___________________

3. Pinyon, 170 ft south of

no. 2.

4. Pinyon, 200 ft south of

no. 3. 

Do.... _________________

5. Pinyon, 200 ft south of

' no. 4. 

Do__.__________________

6. Mountain mahogany, 10 ft

south of no. 5. 

Do________ _ ____.__

7: Pinyon, above station 3__ _

Do..... ________________

Do.. _-____:_____.______

Nonuraniferous coal at La Ventana 

mine 

Juniper. -_-_____. .. _______

Type of branch 

sampled

Live__-___-

___do . 

_-_do-__.-._

 do_ ___

Dead_^___,

Live ______

Dead _ ___

Live _______

Dead ..__._

.-_do__-___-

Dead__ ___

Live _-_-._

Dead

Live -_-_-_

Live

Dead. ___

Dead

Live _-_.--

___do_-_---_

Ash (percent)

5. 1

2. 2

 ' 4. 7

3. 1

2.7.

2. 1

4; 4

1.8

2. 5

2. 7

3. 0

3. 1

2.5

4.4

1.8

2. 3

2. 6

3. 1

2.2

3. 2

5.3

1. 8

Uranium 

(ppm) in 

ash

0.4

.4

.5

.8

3.2

. 4

. 4

. 1

. 5

. 5

. 2

. 5

. 5

1.6*

.4

. 8

. 4

.4

. 8

1. 2

.3

. 2

Uranium 

(ppm) in coal 

65 ft. below 

ground surface '

400

400

4,200

4,200

4, 200

400

400

unknown

unknown

unknown

unknown

unknown

200

200

1, 500

1,500

6

6

i Station numbers and coal analyses from geologic sampling described by J. D. Vine, U. S. Geological 

Survey.
BOTANICAL PROSPECTING FOR URANIUM, SANDOVAL CO., N. MEX. 403

content within the root therefore decreases with distance from the 

source. These variations are reduced in the parts of the tree above 

ground, and the comparative uranium contents of tree branches -and 

leaves appear to reflect very closely the uranium content of the soil or 

rock in which the tree is rooted. The livewood of trees was found to 

contain from 0.2 ppm uranium in the ash when the tree was rooted 

in barren coal containing 0.0006 percent uranium, to 0.8 ppm uraniuni 

in the ash when the tree was rooted in mineralized coal containing 

0.04 percent uranium; and the ash of deadwood ranged from 0.4 ; to 

3.2 ppm uranium under the same respective conditions. The thre,e 

species sampled show no significant difference in uranium absorption. 

Closely related species that may,differ markedly, in percent qf.ash 

nevertheless contain closely comparable proportions of. uranium ijn 

the ash. From this it follows that the uranium content of theory 

weight of different species shows much more variability than does*tjie 

uranium content of the ash. This is illustrated by the following summary, of .livewood data, taken from table. 3; : . « - : ;^

Comparison of average uranium contents in juniper and pihyon branches '

Tree sampled

Juniper ___________________________

Pinyon. _ ________._-_____^_________

Average percent; 

of ash

. .4.9 

. 2. 5

 Average uraniumicontenf * ' ' 

In ash (ppm) :

,'0.40:

'.- ' 45 .

In dry weight 

 (ppm) '

, ...- ' 0,02 '."6.1

. /

Plants of similar absorption habits may be collected, then, regardless of variations in ash content, and used interchangeably in pattern 

sampling. Furthermore, because uranium is measured in the laboratory in the plant ash, it is better to express it in .relation to. ash than 

to dry weight. Too, the deadwood sampled contains a larger amount 

of uranium in the ash than the livewood. This marked' increase, 

shown in table 3, raises the amount' to be detected chemically, in a 

given amount of ash to a more readily determined quantity. For this 

reason, it was decided to use deadwood of -pinyon' and juniper in 

sampling wherever possible on the buttes of ; La Ventana Mesa. -

The assays for each tree were plotted on maps of the buttes and the 

values contoured with an isogram interval of 0.5 ppm of uranium 

(figs. 60, 61, and 62). The resulting isograms are similar in pattern 

although several variations in results are apparent. First, both types 

of wood (live and dead) were not taken from every tree and therefore 

the same number of points is not available for contouring on each 

map. Second, the outstanding difference between maps plotted on 

deadwood and livewood assays is one of uranium content rather than
404 A CONTRIBUTION TO THE GEOLOGY OF URANIUM

pattern, as deadwood consistently contains more uranium in the ash. 

Assays of livewood samples of pinyon and juniper range from 0.1 ppm 

to 1.6 ppm of uranium, and deadwood samples from 0.1 to 2.3 ppm of 

uranium in the ash. The amount of ash in the deadwood samples 

averaged 4.6 percent, compared to 2.5 percent in the livewood samples. 

Third, a group of tree samples from the most favorable part of the 

buttes averaged lower in uranium content than a group of tree samples 

from parts of the buttes inferred to be less favorable from a study of 

coal analyses. The samples from the less favorable area were collected 

and analyzed several months later than the samples from the more 

favorable areas.

Although the causes of the variations mentioned have not yet been 

adequately investigated, it is possible to resolve the differences empirically and to compile maps to show the probable uranium-bearing parts 

of the buttes. It is significant that all common control points on the 

two maps indicate a similar isogram pattern. Therefore, in areas 

where there are not enough control points for close contouring on one 

map, isograms have been inferred from analyses of the other type of 

material and drawn as dashed lines (figs. 60 and 61). It can also be 

seen that the isogram pattern for 1 ppm of uranium in the ash of 

livewood coincides closely with that of 1.5 ppm of uranium in the ash 

of deadwood. If the outlined areas are compared, using this ratio, 

the areas on the east side of the butte appear to be favorable. The 

third variation, that in analyses, probably reflects changes in laboratory procedure. This conclusion is based on the fact that the uranium 

content of deadwood should not exhibit seasonal variations, and this 

is the only alternative explanation of the sharp change in uranium

content in the adjacent areas sampled at different times. Because of

these differences which resulted in an increase of about 0.5 ppm of 

uranium, large areas on the east end of the north butte above the

cutoff values used are probably not favorable and have not been

hachured (fig. 63). 

Areas of plants having relatively high uranium content probably

correspond with areas of relatively high uranium content in the coal. 

The results coincide roughly but not exactly with known areas of

uraniferous coal sampled along tlae outcrop. TKe assays of uranium in coal reported by Bachman, Vine, Read, and Moore (in preparation)

are shown on figures 60, 61, and 62. A final compilation of favorable

areas has been made in figure 63. The tree assays indicate that the

areas or uraniMous com m»j

small magnitude.
BOTANICAL PROSPECTING FOR URANIUM, SANDOVAL CO., N. MEX. 405

TI9N..R.IW.

SECTION 29

1500 Feet

SECTION 32

Areas favorable for 

mineralized coal

FIGURE 63. Probable areas of uranium-bearing coal, as interpreted from analyses of livewood and deadwbod 

samples of pinyon and juniper branches from the north butte of La Ventana Mesa. ' 

SUMMARY AND CONCLUSIONS

A preliminary study was made of the metal content of the uraniferous coal that crops out on La Ventana Mesa and the effect of the 

sulfur and selenium on the vegetation of the mesa slopes. . In addition, 

about two hundred tree branch samples were collected in an area of 

one-half square mile of mesa and analyzed for uranium as a guide to 

exploration in outlining uraniferous portions of the coal.

Minor amounts of sulfur, selenium, chromium, copper, lead, cobalt, 

molybdenum, and nickel were found to be concentrated in uraniumbearing parts of the coal. A selenium content of 600 ppm was reported 

in one sample. The selenium-indicator plants Stanley a and two 

species of Astragalus were noted on the slopes below the coal outcrop. 

These were associated with sulfur-absorbing Crucifers and Eriogonum.

Pinyon and juniper trees growing on the sandstone which caps the
406 A CONTRIBUTION TO THE GEOLOGY OF URANIUM

mesa absorb uranium from the underlying coal. The assays ranged 

from 0.1 ppm of uranium in ash of pinyon and juniper trees rooted in 

barren ground to 2.3 ppm of uranium in the ash of these trees rooted 

in mineralized coal. The uranium content of dead branches was 

found to exceed that of live branches in the majority of trees. Areas 

presumed to be favorable for drilling were outlined on maps of the 

mesa. Botanical anomalies coincide fairly well with the known areas 

of uraniferous coal sampled previously along the outcrop.

Several conclusions may be drawn from the studies made in connection with the botanical sampling program. The association of metals 

in the uranium-bearing coal suggests enrichment from an unusual 

source, possibly the Pliocene(?) Bandelier tuff of Smith (1937). The 

distribution of metals within the coal is limited to isolated patches and 

presumably resulted from ground-water solution and deposition. 

Weathering of the mineralized coal has affected the vegetation of the 

slopes. It is possible that sulfur and selenium plants which grow 

down slope from the deposits may be useful in prospecting.

The assays indicate that the areas of mineralized coal may be 

fracture controlled and relatively small. This botanical survey 

suggests that uraniferous areas of coal may be present in the eastern 

part of the north butte where the coal in the rim is largely under cover.

LITERATURE CITED

Bachman, G. 0., Vine. J. D., Read, C. B., Moore, G. W., 1956 Uranium bearing 

coal and carboniferous shale in the La Ventana Mesa area, Sandoval County, 

N. Mex.: U. S. Geol. Survey Bull, [in preparation].

Cannon, H. L., 1952, The effect of uranium-vanadium deposits on the vegetation 

of the Colorado Plateau: Am. Jour. Science, v. 250, p. 735-770.

Darton, N. H., 1929, "Red Beds" and associated formations in New Mexico:

V, S, Geol, Survey Bull. 794.

Meinzer, 0. E., 1923, The occurrence of ground water in the United States, with 

a discussion of principles: U. S. Geol. Survey Water-Supply Paper 489, p. 95.

Renick, B. C., 1931, Geology and ground-water resources of western SandOVal 

County, New Mexico: U. S. Geol. Survey Water-Supply Paper 620, p. 6-8.

Smith, H. T. U., 1937, Tertiary and Quaternary geology of the Abiquiu Quadrangle, N. Mex. [Abstract] Geol. Soc. Amer. Proc. 1936, p. 103.
INDEX

Page

Abstract ................................... 391

Analyses, dead wood and livewood samples.-- 395,

402-404 

Analytical results, variations in......_.-.. 403

Baadelier tuff.---.-.--......-....-...... 392

Climate..................................... 392

Coal, chemistry............................. 399,400

uranium-bearing__. ________..... 395,399

Conclusions-..-----.......----......,-.---- 405-406

Drainage.---.--.-...--.-.-----.--------- 392

Dufoure, E. F., analyst--..-......--....... 400

Ecology, plant ---.-.--------------- 390,401

Extent of work covered by report..__.... 394,395

Fennclly, E. J., analyst----..-------. 400,402

Fluorimetric analysis for uranium.....__.. 395

Furman, S. P., analyst..--.--...-.-.-- ..... 400

Geology-..-..-.-.----..--.---..-.---- 392-394 

Huffman, Claude, analyst.____..----.. 402

Indicator plants, distribution_............ 399,401

selenium and sulfur----..-.--- 399,401,405

Introduction._........................... 391-394

Page

La Ventana coal mine__.______--....- 401 

La Ventana sandstone member._....--..-. 392

La Ventana syncline.-.._________._ 392 

Literature cited--..----...-------- 406

Location of area studied.__.___......_ 392

Meadows, Jesse, analyst________ .... 400 

Mesaverde formation____._...____ 392 

Methods of study used....--...-----. 394-395 

Meyers, A. T., analyst.._____.....___ 400 

Mineralized areas Inferred.............. 404-405

Nacimiento Mountains_..........----.-... 392

Phreatophytes, definition_.______...... 395

Prospecting, method used.... . -___-. 395

problem__..._._.___............ 399

Purpose of investigation...-_................. 392

Rainfall... .....1 .................. 392

Rio Puerco. ---------.. ................ 392

Eoots, depth' of penetration.....-.-.-....- 395

Sampling methods.. -._--_-_.__--_-_---- 395

Sherwood, A. M., analyst.__..:_____.. 400 

Summary...____...____._____ 405-406

Topography...... .......... .. 392-393

Uranium absorption by tree cover ... 395,401-404

407

U. S. GOVERNMENT PRINTING OFFICEi 1988