Grants, New Mexico in beds ranging in
age from Triassicto Miocene (Cannon,
1960).
Astragalus preussi (fig. a) has purple
pea-likeflowersin contrastto the creamcolored flowers of A. pattersoni, but
otherwiseis similar in appearance.The
absorptionof largeamountsof vanadium
by this speciesmay be a significant factor
in the geographic distribution of the
plant. Astragaluspreussihas beenusedin
prospecting in the Thompson, Green
River, and Henry Mountain districts of
Utah's Morrison Formation. Other indicator species of Astragalus are A.
orgillous and A. confertiflorus (Cannon,
1960).
INCHES
'4
(
(
Frcune 5-,4ster venustus Jones (after Cannon,
1957).
FrcuRE4-,4s/ragalus preussi A. Gray (after Cannon, 1957).
porsoNvETcH.Perennial,
CouvoN NAME:PREUSS
many stems less than a foot high rise from a
woody base, purple flowers with darker calyx,
smoothpinnatewith ll to 15 ellipticleaflets;fat,
oblong pod slightly curved, with short
:H:,t,
Districtsnoted: Ship Rock, Slick Rock, Uravan,
GypsumValley, Thompson,San Rafael, Henry
Mountains,GreenRiver,and Moab.
Corvrvot NAME:wooDy nsrpn. Woody perennial,
naked flower stalks, long taproot, 6 to 8 inches
tall, composite daisyJike white to lavender
flowers, spatula-shaped hairy leaves and small
silky seeds.
Districts noted: Thompson, Moab, Henry Mountains and Green River.
and Grindella (gumweed). Calcium or
sulfur indicatorplantsshouldnot be consideredindicativeof mineralizedground,
Additional plantsthat requireselenium asmanyof theseplantsarecommonroadand may act as indicatorsof uranium ore side weeds.Thesespecies,on the other
areAster venustus(woody aster),Oryzop- hand, may abound in mineralized areas
sis hymenoldes (Indian ricegrass) and becausethe calcium or sulfur is more
Stanleya sp. (desert prince's plume). readilyavailablein uraniumdepositsthan
Commonly found on clay soils and allu- in the surroundingcountryrock (Cannon,
vium, Aster venustus(fig. 5) has white to r960).
pink daisy-like heads and hairy leaves
Plant chemistry
growing from a woody base. Oryzopsis
hymenoides(fig. 6), a perennialgrasswith
The seleniumcontentof a givenplant is
smallrice-likeseeds,is prevalentthrough- not a simplefunction of the soil. The maout the westernUnited Statesin soilscon- jor factor influencing selenium uptake
taining small amounts of selenium. from soils is solubility. Although selenStanleyasp. (fig. 7) is a weedyperennial ium in acid soilsis insolubleand unavailof the mustard family with long flower able to plants, alkalinesoils host soluble
spikesand thin seedcapsulesextending selenium-up to half the total amount
from the spikes.Although the plant, com- present. The degree to which soluble
mon to the Colorado Plateau, requires selenium will be absorbed is in turn
both sulfur and selenium,its useas an in- dependent(althoughin ways not underdicator is limited (Cannon, 1960).Other stood) on factors such as chemical form
marginal indicator plants areDescurainia and quantitiesof other soil constituents,
(tansymustard),Lepidium (pepperweed), especiallysulfur. Thesefactors are more
Frcvxe 6-Oryzopsis hymenoldes (Roem and
Schult.)Rick (afterCannon,1957).
Cot*.tvoNNluE: ItoteN Rtcpcness.Perennialgrass
I to 2 ft high, with deepfibrous roots, small dry
flowers. inrolled narrow flowers and small ricelike seeds.
Districts noted: Gypsum Valley, Rifle, Slick
Rock, Bull Canyon,ParadoxValley,White Canyon, Thompson,San Rafael,Henry Mountains,
GreenRiver, Moab, Monticello,Grants, Poison
Basin,and ShipRock.
significantin the root-bearingsoil horizon
than at the soil surfaceproper (Cannon,
r9s2).
Although most plants are nonaccumulators, any plant may passivelytake up
selenium dissolved in the soil-the
amount will be determinedin large part
by the form of the seleniumand the concentrationin the soil. In summary, the
concentrationof seleniumin a givenplant
is determinedby its selenium-accumulating power and the soil's selenium-supply
power. The former is determinedby the
speciesof the plant, its stageof growth,
and its vigor. The latter is determinedby
the form of selenium.its concentrationin
the root zone, soil pH, and the amounts
and kinds of otherelementspresent(Cannon, 1952).
Toxicity of selenium-richplants
Seleniumhas long been known for its
toxicity to animals.Two typesof poisoning have been recognized:"Blind staggers," usually found in cattle, manifests
itself in poisonedanimalsby the tendency
to wander aimlessly,running into fences
or other fixed objects.The effectsappear
after a week or more of ingestingnative
I=F
New Mexico Geology
November1979