GEOLOGICAL SURVEY CIRCULAR 264 

GEOBOTANICAL RECONNAISSANCE 

NEAR GRANTS, NEW MEXICO 


UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary · · 

GEOLOGICAL SURVEY 

W. E. Wrather, Director 

GEOLOGICAL SURVEY CIRCULAR 264 

GEOBOTANICAL RECONNAISSANCE NEAR 

GRANTS, NEW MEXICO 

By Helen L. Cannon 

This report concerns work done on 

behalf of the U. S. Atomic Energy 

Commission and is published with 

the permission of the Commission 

Washington, D. C., 1953 

Free on application to the Geological Survey, Washington 25, D. C. 
GEOBOTANICAL RECONNaiSSANCE NEAR GRANTS, NEW MEXICO 

By Helen L. Cannon 

CONTENTS 

Page 

Abstract ...............•.... ,,................ 1 

Introduction . . . . . . • . . . . . . . . . • . • . . . . . . . . . . . . . 1 

Geology................................... . 2 

The effect of ore deposits on native vegetation... . 3 

Page 

Application of geobotanical methods 

of prospecting for uranium................ . 3 

Literature cited .......•....... ~........... . 7 

Unpublished reports . • . . . . . • . . • . • . . . . . . • . • . . 8 

ILLUSTRATIONS 

Page 

Figure 1. Geologic map of Grants district, New Mexico, showing areas investigated . • . • . • . • . . • • . . . . • . . . .. . 2' 

2. Sketch map of area 1, NW-i- sec. 19, T. 13 N., R. 10 W., showing geobotanical traverses 

across uranium deposits in the Todilto limestone member . . • • . . . . . • • . . . • • • . . . . . . . . . . . • • • . • . . 5 

3. Diagram showing uranium content of unwashed tree needles collected along traverses A-A' 

and B-B' in s'ec. 19, T. 13 N., R. 10 W.................................................... 6 

4. Diagram showing uranium content of trunkwood collec,ted along traverses A-A' and B-B' in 

sec. 19, T. 13 N., R. 10 W............................................................. . 7 

TABLE 

Page 

Table 1. Uranium content of samples from trees rooted in ore bodies of the Todilto limestone member. . . . . . 4 

ABSTRACT 

The application of geobotanical methods of prospecting in uranium-bearing areas in McKinley County, 

near Grants, N. Mex., has been investigated briefly. 

The uranium deposits occur in the Todilto limestone 

member of the Wanakah formation and in the overlying 

Morrison formation, both of Jurassic age. Carbonaceous uranium ore in the Morrison formation contains 

a high percentage of selenium, and selenium-indicator 

plants are commonly associated with these deposits. 

Such plants have not been observed on the Todilto 

deposits. 

The average uranium content in the ash of trees 

rooted in ore deposits of the Todilto limestone member 

is more than 20 parts per million, and trees rooted in 

barren limestone average about 10 ppm. The uranium 

content of the plant ash is detectable by fluorimetric 

methods. Uranium analysis of trees growing on the 

Todilto bench and mapping of selenium-indicator plants 

on the sandstones of the Morrison formation are recommended as a method of prospecting. 

INTRODUCTION 

Geobotanical techniques show considerable promise 

as tools in the search for uranium in the Wanakah and 

Morrison formations of Jurassic age near Grants, 

1 ' 

McKinley County, N. Mex. Large amounts of uranium 

are absorbed by plants growing near uranium deposits 

in the Todilto limestone member of the Wanakah formation (area 1, fig. 1). Selenium-indicator plants are 

present on the ore-bearing sandstones of the Morrison 

formation (area 2, fig. 1). 

The outcrop of the Todilto limestone member 

chosen for study is 18 miles by road northwest of Grants, 

in the northwest corner of sec. 19, T. 13 N., R. 10 W., 

New Mexico principal meridian {fig. 1). The area lies 

near the south end of Haystack Mountain, McKinleyCounty, 

N. Mex., and about 80 miles west of Albuquerque. The 

outcrop of uranium-bearing sandstone in the Morrison 

formation is 14 miles north of Grants in sec. 18, 

T. 13 N. , R. 9 W. Both localities are reached 

by a dirt road leading north and east from U. S. 

Highway 66 just east of the town of Prewitt. The 

main line of the Atchison, Topeka, and Santa F~ 

Railway parallels U. S. Highway 66. Mineral l,j 

rights to the property are controlled by the railroad. 

The altitude of the deposits is about 6, 500 feet. 

The average annual rainfall is 10 to 15 inches. 

The vegetation consists of xerophytes, or droughtresistant plants, such as saltbush, sagebrush, and 

grasses; junipers and pinyons grow on the sandstone and limestone benches. 
EXPLANATION 

Dakota sandstone 

Morrison formation 

Summerville formation 

[ill[]] 

Todilto limestone member of Wanakah 

formation and Entrada sandstone 

undifferentiated 

~ 

Chinle ~ formation 

-- ---- Fault, approximately located 

Area of investigation 

- 2 0 

R.IO W. R. 9W. 

6Miles 

Geology after T. 0. Evans; Atchison, 

Topeka, and Sante Fe Railway 

T. 

14 

N. 

t 

13 

N. 

t 

12 

N. 

T. 

II 

N. 

Figure 1. -Geologic map of Grants district, New Mexico, showing areas investigated. 

The field work was done in May 1951. The author 

wishes to acknowledge the able assistance of Barbara Knapp 

and to express her appreciation to Irving Rapaport of 

the Atomic Energy Commission for help in field orientation and to Abraham Rosensweig of the Atomic Energy 

Commission for furnishing background information used 

in this report. Special acknowledgment is made to the 

Atchison, Topeka,and Santa Fe Railway for permission 

to study the deposits on the railroad property. The 

work was sponsored by the U. S. Atomic Energy Commission. 

2 

GEOLOGY 

The area studied is on the northeast flank of the 

Zuni Mountains and within the Colorado Plateau province. The geology has been described by Gregory (1917), 

by Darton (1928), by Baker, Dane, and Reeside (1947), 

by Reyner and Sheridan (1950), and by Evans (1950). 

Sedimentary beds of Mesozoic age dip gently to the 

northeast and the resistant sandstones and limestones 

form inclined benches. A broad valley has been formed 

by the erosion of the Chinle formation of Triassic age. 
Jurassic rocks-Entrada sandstone, Wanakah, Summerville and Morrison formations-crop out on the northeast side of the valley; The 4- to 18-foot thickTodilto 

limestone member of the Wanakah formation caps 

the Entrada sandstone and forms a broad shelf or bench 

along the edge of the valley. The Summerville formation is represented by a sandstone bed called the 

Red Mesa sandstone by Hoover (1950). This sandstone 

and the Westwater Canyon sandstone and Brushy Basin 

shale members of the Morrison formation form a southfacing slope along the north side of the Todilto bench. 

The slope is capped by the Dakota sandstone· of Cretaceous 

age. 

Uranium deposits occur along the outcrops of 

these beds in McKinley and Valencia Counties for a 

distance of 18 miles, and also on the Laguna Indian 

Reservation 30 miles east of Grants. In the section 

studied, shown as area 1 on figure 1, the Todilto limestone member has a maximum thickness of 15 feet 

and forms a bench 1, 000 feet wide; the overburden is 

less than 4 feet thick and the average depth to the top 

of the ore, which is exposed in numerous test pits, 

is only 5 feet. The ore minerals in this locality, 

according to Gruner and Gardiner (1951), are mainly 

secondary tyuyamunite, carnotite, and uranophane, 

associated with small amounts of pitchblende. Vanadium 

and uranium occur in nearly equal amounts. The content of selenium is very low. A specimen of ore, collected in conjunction with the geobotanical studies, contained 0. 31 percent equivalent U, 0. 22 percent U, 

0. 39 percent V 20 5 , and less than 0. 000001 percent Se. 

A specimen of ore of the Todilto interbedded with 

volcanic flows collected from the Laguna Reservation 

contained 0. 0038 percent selenium. 

Carnotite and carbonaceous uranium ores occur 

at several localities in the sandstone beds of the Morrison 

formation in the Grants area. The deposit studied is 

in Poison Canyon, 14 miles northeast of Grants, shown 

as area 2 on figure 1. The ore is in the conglomeratic 

Westwater Canyon sandstone member of the Morrison 

formation. A selected sample of black carbonaceous 

ore contained 2. 02 percent equivalent U, 2 .. 88 percent 

U, 0. 99 percent V 20 5 , and 0. 234 percent Se. As far 

as the writer knows, this is the largest amount of 

selenium reported from a sedimentary rock. A highly 

vanadiferous ore specimen collected from the Laguna 

Reservation contained only 0. 0001 percent selenium. 

THE ·EFFECT OF ORE DEPOSITS 

ON NATNE VEGETATION 

Plants are affected by uranium ore deposits in 

two ways. First, due to the usual association of 

selenium with uranium ores, plants that require 

selenium may grow near uranium deposits. Second, 

plants that are rooted in ore deposits absorb uranium 

and vanadium in detectable quantities. 

Selenium-indicator plants apparently do not 

grow· on the Todilto limestone member, although in 

some areas the ore contains sufficient selenium to 

support selenium-indicator plants. These plants of 

the preussii group of Astragalus (milkvetch) and 

Oryzopsis hymenoides (Indian ricegrass) grow profusely along the base of the outcrop of the carbonaceous 

ore in the Westwater Canyon sandstone member of the 

Morrison formation in Poison Canyon. The vegetation 

3 

on the alluvium of the valley .floor consists mainly of 

xerophytic plants such as A triplex confertifolia (shadscale), which is a selenium absorber. 

Juniper and pinyon trees that grow on the Todilto 

limestone member absorb unusual quantities of uranium but very little vanadium. Samples of unwashed 

and washed needles, peeled branches, and peeled roots 

of five selected trees were collected to provide data 

on distribution of uranium in plants in a lime environment, and also to check the amount of contamination. 

The analyses of these samples for uranium are given 

in table 1. 

Analyses of washed and unwashed samples of 

the foliage indicate contamination. Washing does not 

remove all surface contamination from the vegetation; 

the chemical analyses of washed samples, therefore, 

do not represent uncontaminated material. Roots and 

branches were carefully peeled to eliminate all possibilities of contamination. The analyses, compared 

in dry weight figures, indicate only slightly less uranium in r·oots and branches than in washed needles. 

Results shown on figures 3 and 4 indicate that trunkwood also contains a quantity of uranium similar to 

that of needles. The average uranium content of tree 

samples from area 1 on the Todilto limestone member 

is about 10 times greater than the content of similar 

samples collected from sandstones elsewhere on the 

Colorado Plateau (Cannon, 1952). This is probably 

the result of the deposits having been exposed to 

weathering by extensive erosion and the uranium in 

the minerals becoming water soluble and available 

for plant absorption. 

Eight samples were analyzed for vanadium. Samples of peeled branches and washed needles contained 

less than 10 ppm V 20 5 in the ash and samples of unwashed needles contained from 18 to 27 ppm. The 

absorption of vanadium is surprisingly low and is in 

direct contrast to the higher absorption of uranium 

from the same deposits. The average content of V 20s 

in vegetation of the Colorado Plateau as determined 

by previous work (Cannon, 1952) is 40 ppm in the ash. 

The plants sampled at Grants, N. Mex. , were thus 

below normal background. The reasons for this are 

not 0learly understood although presumably closely 

related to the physiologic means of absorption of these 

two elements and their availability in an oxidized limestone environment. A possible explanation is that in a 

calcium carbonate environment, the weathering process fixes the vanadium and frees the uranium. 

APPLICATION OF GEOBOTANICAL METHODS OF 

PROSPECTING FOR URANIUM 

Prospecting for uranium by analysis of vegetation 

is a feasible method of exploration in the Todilto limestone member. 

Prospecting by chemical analysis was tested in 

sec. 19, T. 13 N., R. 10 W. The location of sample 

stations is shown on figure 2 and the results are shown 

graphically in figures 3 and 4. Test pits expose ore 

at an average depth of 5 feet. To test the amount of 

contamination by dust, as well as the _usefulness of 

the sampling methods in prospecting, collections of 

both needles and trunkwood were made of juniper and 

pinyon at intervals of 100 feet along east-west and 
~ 

Table 1.--Uranium content or samples rrom trees rooted in shallow ore bodies or the Todilto limestone member, sec. 19, T. 13 N., R. 10 w. 1 

• Unwashed needles Washed needles Peeled branches Peeled roots Plant station no. (shown on rig. 2) 

Pinyon 3--------------------

Juniper 13------------------

Pinyon 13-------------------

Juniper 17------------------

Pinyon 17-------------------

Average----------------

1Claude Huffman, aaalyst. 2 Unpeeled. 

U in ash 

(ppm) 

112.0 

27.0 

53.0 

49.0 

46.0 

57.0 

U in dry wt. 

(ppm) 

2.9 

1.1 

1.2 

1.8 

1.0 

1.6 

U in ash U in dry wt. 

(ppm) (ppm) 

106.0 2.0 

24.0 0.78 

30.0 0.69 

40.0 1.4 

33-0 0.76 

47.0 1.1 ~~--- -

U in ash U in dry wt. U in ash U in dry wt. 

(ppm) (ppm} (p:Pn) (ppm) 

44.0 0.57 97.0 1.3 

11.0 2.7 49.0 .49 

26.0 .47 74.0 1.55 2 

7-0 -29 --- --- 13.0 .20 14.0 .20 

20.0 .85 60.0 .87 
U1 

?q 

• 82 • 80 

• • 58 56 

.68 

Base by T. 0. Evans, 

tchison, Topeka, and Santa Fe Railway 

~ 

~« 

• 36 

.34 .32 

\\m~ tor motions 

EXPLANATION 

Limestone 

~ containing more 

than 0.1 percent U3 Oa 

•a2 

Location of trees 

""\~6~\0 100 0 500 Feet 

~~e l1 1 1 I 1 • 1 1 I 

Figure 2. --Sketch map of area 1, NWt sec. 19, T. 13 N., R. 10 W., showing geobotanical traverses across uranium deposits in the Todilto limestone membet: 
70 

60 

50 

:::> 40 

E 

0.. 

a.. 30 

A 

20 50 

62 60 

10 

0 

~ 

46 

44 

48 

I 

Juniper tree 

40 42 38 

EXPLANATION 

!•:•:···:•'.•: I 

Limestone containing more 

than 0.1 percent U30a 

'f' ROAD 

26 

A' 

24 

. I 

~ Sampling points projected 

Pinyon pine into traverse lines 

100 0 500 Feet· 

IL~'J'~'~'----~--~--~----~~' 

46 

66 72 

64 1 L_ I No Vegetation ~ 

1 

1: : 

17 

23 

74 76 

78 

Figure 3. -Diagram showing uranium content of unwashed tree needles collected along traverses A-A' and B-B' in 

sec. 19, T. 13 N., R. 10 W. 

north-south traverses across the ore body. Wood from 

the trunk and needles from all sides of the tree trunk 

were sampled at the same time. The samples were airdried, ashed, and analyzed by the fluorimetric method, 

in the Trace Elements Section, Denver Laboratory of 

the Geological Survey (Grimaldi and othe!S, 1950) .. 

The absorption of urani 1lm by trees rooted in 

weathered ore-bearing limestone is very high. Along 

section A-A' the increment due to contamination from 

dust was much less tilan expected, and in many places 

the trunkwood of the trees contained more uranium than 

the unwashed needles. The trunkwood of several trees 

over ore contained more than 30 ppm U in the ash. 

6 

The trunkwood samples average 10 ppm U in the ash 

on limestone containing less than 0.1 percent Ua0 8 , 

and more than 20 ppm on limestone containing C. 1 percent or more U3 0 8 • The results of this cursory examination are much more uniform than were expected for 

crude sampling in a disturbed area, and suggest that 

results may be contoured from an organized sampling 

program in unexplored outcrop. 

Prospecting for uraEium by analysis of vegetation 

on the favorable areas of the Todilto limestone member 

is recommendeJ. Needles of deep-rooted pinyons or 

junipers may be sampled by collecting needles from all 

sides of a tree at certain specified intervals along 
70 

60 

50 

~40 

E 

0. 

Q.. 30 

20 

10 

46 

48 38 32 

30. A' 

40 

42 34 24 

oLD~L---~JL~L-~L-~~~~L-~--~~L-~--._~L--U--~~------~--

g:s::g 

70 

60 

50 

3 

~40 

E 

0. 

0.. 30 13 

20 B 

10 

0 

I; ; ; I 

I 

Juniper tree 

~ Pinyon pine 

100 0 

I II" 

No Vegetation 

EXPLANATION 

I•: I: I I II.; .; •I 

Limestone containing more 

than 0.1 percent U30a 

Sampling points projected 

into traverse lines 

500feet 

I 

46 

+ ROAD 

B' 

Figure 4. -Diagram showing uranium content of trunkWood collected along traverses A-A 1 and B-B' in sec. 19, 

T. 13 N., R. 10 W. 

traverses or on a grid pattern. Wood from the branches 

or trunk of the trees is a favorable sampling medium. 

One hundred milligrams of dried wood or needles are 

needed for an analysis by the fluorimetric method. 

Thirty samples per .day can be .collected and charted 

by a two-man party, and a similar number can be 

analyzed by a chemist in a centrally located laboratory. 

The occurrence of selenium-indicating Astragalus 

plants on the Westwater Canyon sandstone member of 

the Morrison formation at Poison Canyon and also in 

the Laguna Indian Reservation suggests that the mapping 

of the occurrence of these plants on the beds of the 

Morrison is a feasible method of prospecting for uranium. 

7 

Areas of plants occurring on colluvium and along 

appropriate stream drainage as well as areas of plants 

closely associated with the outcrop of the ore-bearing 

beds should be investigated. 

LITERATURE CITED 

Baker, A. A., Dane, C. H., and Reeside, J. B., Jr., 

1947, Revised correlation of Jurassic formations 

of parts of Utah, Arizona, New Mexico, and Colorado: 

Am. Assoc. Petroleum Geol. Bull., v. 31, p. 1664-

1668. 
Cannon, H. L., 1952, The effect of uranium-vanadium 

deposits on the vegetation of the Colorado Plateau: 

Am. Jour. of Scienc-e, v. 250, p. 735-770. 

Darton, N. H., 1928, "Red Beds" and associated 

formations in New Mexico: U. S. Geol. Survey 

Bull. 7~4, 356 p. 

Gregory, H. E., 1917, Geology of the Navajo country: 

U. S. Geol. Survey Prof. Paper 93, 161 p. 

Hoover, W. B., 1950, New Mexico Geol. Soc. Guidebook of the San Juan Basin, New Mexico and Colorado, p. 77. 

UNPUBLISHED REPORTS 

Evans, T. 0., Exploration of uranium deposits sec. 19, 

T. 13 N., R. 10 W., N. M. B. & P. M. near Grants, 

New Mexico: Company report, Atchison, Topeka, 

and Santa Fe Ry., 1950. 

8 

Grimaldi, Frank, Ward, F. N., and Kreher, Ruth, 

1950, A direct quantitative fluorimetric method 

for determining small amounts of uranium in 

the field and laboratory: U. S. Geol. Survey 

Trace Elements Investigations Rept. 98. 

Gruner, J .. W., and Gardiner, Lynn, 1951, The 

mineralogy of the uraniurr.~. deposits of the Grants 

area, New Mexico: Progress report, Contract 

AT-(30-1) 610, Atomic Energy Commission. 

Reyner, M. L., and Sheridan, M. J., 1950, 

Preliminary report on uranium deposits in 

McKinley and Valencia Counties, near Grants, 

New Mexico: Spokane Ext. Activity Rept. , 

Atomic Energy Commission. 

Ill'l'.-qn'. SEC., WASH., D.C.J8l71