0ccurrence
of Bishop
AshnearGraffi?,
NewMexico
by curtis P. Kortemeier,Industrial
Minerals
Exploration,
Anaconda
Minerals
company,
Denver,
c0
At leastthree principal centersof rhyolitic
volcanismwereextantduring pleistocenitime
in the westernUnited States.Thesethreecal_
dera complexes,wjth associatedtephra units
and outflow sheets,are: yellowstonevolcanic
complexin Wyoming and ldaho, producing
the Pearlette family ashes; Valles caldera.
northernNewMexico,with the Tsankawiand
Guajepumicebeds;and Long Valleycaldera,
easternCalifornia, producingthe BishopAsh
(Izett and others,1972).Theseairbornepyro_
clastic deposits, forcibly ejected simultaneouslywith the eruption of outflow sheets.
arewidelyusedtodayasmarkerbeds.In ordei
to serveasmarkerbedsthesedepositsmust be
identifiableand stratigraphically
unique.
While attempting to identify ar isolated
outcropof volcanicashin the southernpart of
the Jornadadel Muerto of south-centralNe*
Mexico, I investigatedthe criteria of various
workers in volcanic ash correlation for the
purpose of establishinga standard set of
criteriafor readyidentificationof pleistocene
and MineralResources.
Stratigraphyand regionalgeology
An outcropof white, friable volcanicashis
Iocatedapproximately8 mi north of Rincon,
New Mexico,in an arroyoat the Gramasiding
of the Atchison, Topeka, and SantaFe raill
beenassigned
a Pleistocene
ageon the basisof
paleontology(Strain,1966).
Cavp Rrcs FonuarroN-In the base of
Grama Gully, fine-grainedsedimentsof the
Camp Rice Formation are exposed(tie. 2),
representinga distinct basin-floor facies of
deposition.Fossilfauna from the Camp Rice
have beendated paleontologicallyas pieistocene in age (Blancan and Irvingtonian) by
Strain (1966)and Hawley (1978,correlation
chart2).
The bulk of Camp Rice Formation is consideredto havebeendepositedthrough much
of Pleistocenetime by river distributaries
which fannedout from a narrow basinin the
PalomasBasinaboveHatch. The locusof active depositionduring Camp Ricetime seems
to havewanderedwidelyacrossthe broadcen_
tral plain of the southernJornadadel Muerto
(Seager
and Hawley,1973).
A subfaciesof the Camp Rice basin floor
preservesthe ash bed (fig. 3). This subfacies
consistsof l-3 ft (0.3-l m) of reddish-brown
clay, overlain by l-2 fr (0.3-0.6 m) of light
greenishclay which is interbeddedwith and
overlain by a bed of white, friable. biotitic
volcanicash.The ashrangesin thicknessfrom
0.5 to l.l ft (0.15-0.35m). This extremelv
fine-grainedsubfaciesis indicativeof a lowenergyenvironmentof depositionand rapid
ments of the Camp Rice Formation and has
R e c e n fl i l l d i r t
Bosin-floorfocies
Olderpiedmonlfocies
CompRiceFormotion
ond.gul ly- bollom
sedtments
meosuredseclrons
benchnork showinq
elevoton in fl
FIGURE l-Locerrox MAp sHowlNGAREAoF rso_
LATEDourcRop or Brsxop Asn in south_central FIGURE
2-LocerroN
New Mexico.
coLuvHs
oF MEASURED
srRATlcRApHrc
and surficial geology of Grama Cully.
22
May 1982
New Mexico Geology
aggradation.This is interpretedas an overbank depositlaid down in the final stagesof
aggradationof the ancestralRio Grande.Both
the upperand lower contactsof the overbank
subfacieswith the basin-floorfaciesare conformableor paraconformable.
The Camp Rice then marks the final stages
of aggradationof the Pleistocene
Jornadadel
Muerto Basin(Seagerand others, 1975).The
constructionalRincon surfacewas stabilized
soon after the depositionof the ash marker
bed and representsthe cessationof aggradation for this part of the Jornadadel Muerto
Basin(Seager
and Hawley, 1973).
YouNcen oeposrts-Younger depositsin
the area overlie the Camp Rice Formation
disconformablyand are dividedinto two distinct facies.A piedmont-slope
facies(epo of
fig.2), consistingtypicallyof gravellycoarsegrainedsediments,forms a thin veneerover
the Camp Rice Formation. Thicknessof the
piedmont-slopesedimentsis generally less
than l0 ft (3 m). A youngerbasin-floorfacies
is also present,locatedalong the present-day
axis of the basin. It is comprisedof finegrainedloamy sediments(fig. 2) of unknown
maximum thickness.Thesesurficial deposits
are correlativeto the JornadaII and the petts
Tank morphostratigraphicunits (Seagerand
Hawley,1973).
Correlationand dating
Any correlations between volcanic ashes
must be attemptedusingas many physicalparametersas possible.While this seemsintuitively obvious,realizingthat any correlationis
by nature permissiveis extremelyimportant;
that is, a correlation is permitted if the
physicalpropertiesmatch, never demanded.
The physicalparametersthat correlationsare
basedon typicallyinclude:chemicalcomposition, age,petrography,and, tentatively,shard
morphology.Of these,greatestcredenceusually is given to the absoluteageand chemical
analysis.
Whole-rockanalysisof the ashfrom Grama
Gully was made using X-ray fluorescence
methods.Table I shows the results of this
analysisand comparesthe analysisof the ash
from GramaGully with analyses
of the Bishop
Ash, the Bishop Tuff, and the pearlette
type-O ash. Visually, the compositionof the
ash from Grama Gully apparentlyis closer
chemicallyto both of the Bishop volcanics
than to the Pearlettetype-O ash. This visual
inspectionis not conclusive.
Statisticaltreatmentof the data (after Bor_
chardt and others, l97l; Borchardt and
others,1972:.and Sarna-Wojciki,1976)shows
that the ash from Grama Gully is chemically
very similar to both the Bishop Ash and the
BishopTuff of Long Valley,California.Table
2 shows the various statistical parameters
calculated.Thesestatisticalparametershave
beendevelopedempiricallyfrom ash samples
knownto correlate.The criticalvaluesofthese
parameters
are: X-Bar = 1.00 +0.20, Percent
Coefficient of Variation = 250/0,and Coefficientof Similarity = 0.8. Usingthesecriteria,
one can see that apparently the ash from
Grama Gully has closechemicalaffinities to
both the BishopTuff and the BishopAsh. It is
nNnI-vsls or Btsgop Ass aNo Prenr-Errr rvpn-O ASHwrrH AsH rnov Gnevn Gullv.
TABLE l-CIrEurcel
l, analysis by XRF Ted Bornhorst, personal communication, 1980 (whole rock); 2, Borchardt and others,
1972 (glass sep:[ates only); 3, Izett and others, 1970a (glass separatesonly); 4, Wes Hildreth, personal
communication, I 979 (whole rock); and 5, Izett and others, I 970b (glassonly).
GramaAsh'
BishopAsh'
Bishop Ash3
Bishop Tuffa
Pearlette type-O5
percent
SiOz
TiOz
AlrOs
Fe,Os
FeO
Mgo
CaO
NazO
KzO
PzOu
Na
K
77.9%
0.11"/"
13.4 o/o
1.0 "/"
Rb
Ba
La
1 8 3p p m
1 0 9p p m
3 5p p m
87ppm
3ppm
57ppm
56ppm
22ppm
0.4
0.6
3.4
5.1
72.3 o/o
0.06%
12.5 o/o
0.7%
0.5%
0.05%
Q.45"/o
"/"
%
%
"/o
3A%
4.9%
77.4 "/"
0.07o/o
12.3 y"
72.63o/o
O.12"/"
11.71%
0.57"/o
1.40%
0.17"/"
O.7 Y.
0.01y"
0.45V"
3.9 "/"
4.8 "/"
0.01%
2.O o/o
5.44%
O.02"/"
2.5"4
4.1o/o
:
parls per million
Zr
Sc
Sr
Pb
Y
1 6 0p p m
5 0 - 1 0 0p p m
1 6 - 2 7p p m
80 ppm
,:rr^
tu
_Tot
5 ppm
1 3 5p p m
40ppm
35ppm
1 9 0p p m
1 0p p m
1 9p p m
":o'
3 . 0p p m
more similar to the Bishop Tuff than to the
Bishop Ash. One possible explanation for this
is that the analysis of the Bishop Tuff was
done on the whole rock, as was the ash from
Grama Gully, but the analyses from the
Bishop Ash and the Pearlette type-O were performed on glass separates. Because of the
small volume and simple phenocrystic assemblage, the differences between the whole-rock
and glass-only analyses are expected to be
small. These differences should be primarily
in Fe, Mg, and Ti.
A zircon fission-track age date was obtained
to verify the Pleistoceneassignmentof the ash
and to justify its comparison to other Pleistocene ashes. Zircon microphenocrysts were
extracted from a lO-kg sample of the Grama
Gully ash and prepared using the methods of
Naeser (1976). Approximately l0 kg of ash
was sieved and separated with heavy liquids.
The resulting zbcon fraction was irradiated
and etched. The resulting fission tracks were
counted and yielded an age of 0.754 + 0.2
m.y. with a standard deviation of 2690 (table
3; fig. 4); although the standard deviation is
high, it agreeswell with agespreviously determined for the Bishop Ash by other workers.
25 ppm
oF AsH FRoM
TABLE 2-VaxtarroN ANALYSES
Gnnva GulLv roorHERAsHEs.
SOUTH
NORTH
No.2
No.3
B o s i n - f l o of ro c i e s
t_l1grL1Lo
r mIt v
91o1oLo
C o m pR i c e
B i s h o pA s h
B i s h o pT u f f
P e a r l et t e " O "
C r a m aA s h
Fossil
fission tracks
C
.9
E
g r e e nc l o y
E
r e d cr o y
o.9
E
- - -
o
silty loom
o.6
=
Ar royo
bottom
clov
cross-bedded
sono
silt with
corbonote
cemenl
corbonote
c o nc r e t i on s
e r o s i o ns u r f o c e
volconic osh
sond
FIGURE 3-Meesunro
Absoluae
age (m.y.)
0.015152
0.011561
0 . 0 115 6 1
0.011029
346
373
272
^l / - - \
\
F-=
't.37
15
10
8
13
1.22
1.35
1.00
Cumolaaiv€
oge (m.y.)
.855
.664
.915
.622
.855
.695
.799
.754
o
-----
==
31.5
27.9
41.82
0.00
CefficiHl
ol sinilodly
Ageof BishopAsh: SampleST-05-.754 + .2m.y
Standarddeviation:0 = 26.9V0
E
o
|
1.77
1.16
1.26
1.00
Numhr ol
species
Induced
lission tracks
166
4
6
3
v o l c o n i co s h
t - .---l
_l loom or slll
Cfttficicnl
ol
vsdcbilily (qo)
TABLE 3-CalcuLerrD AGEoF AsHFRoMGnane
Gurrv; s/i, fossil track density/induced track
density.
colcoreous
silt
Arroyo
b o it o m
X-Bor
o.3
4
srRArrcRApHICcoLUMNsFRoMGRAMAGur-ly, showing faciescorrelations.
\1
f--'-8...t-----a-(9'lorrBj)
/
Y
O i n d i v i d u o lc o u n l s
A cumulolivecounls
o.2
0.1
t23456789lOllt21314
Fissiontr@ks counled
AGEDETERMTNAFIGURE 4-ZrRcoN FrssroN-TRAcK
IF
rroN for ash from Grama Gully.
New Mexico Geology
May 1982
Morphology and petrology
To gain further evidenceas to the identity of
the ash deposit preserved near Grama. other
physical properties were examined. Class
shards from the sample were examined with
an optical petrographic microscope. The average index of refraction was 1.500 + 0.005.
The only phenocrysts identified were biotite,
magnetite, and zircon, for which the indices of
refraction were not determined.
Detailed three-dimensional-shard morphol_
ogy was examined using a scanning electron
microscope. The sample from Grama Gully is
typified by complex shard forms: 65go pumiceous shards, l09o complex bubble-junction
shards, and 20-25V0 bubble-wall shards.
Table 4 contrasts the physicat properties of
the Bishop Ash with the Pearlette type-O ash.
When the physical properriesof rhe ash from
Grama Gully are compared to the properties
sbown in table 4, one can seethat the ash from
Grama Gully has properties consistent with
thoseof the Bishop Ash.
near Mount Blanco, Texas with the Guaje pumice Bed of
the Jemez Mountains, New Mexico: Quaternary Research,v 2,p 554-578
Naeser, C. W , 1976, Fission track dating: U.S. Geological
Survey, Open-file Repr 76-190, 60 p
Sarna-Wojciki, A.,1976, Correlation of Late Cenozoic tuff
Central Coast Ranges of California by means of traceand minor-element chemistry: U S. Geological Survey,
Prof Paper972,23p.
Seager, W. R , and Hawley, J W., 1973, Geology of the
Rincon quadrangle, New Mexico: New Mexico Bureau of
Mines and Mineral Resources,Bull. l0l, 42 p.
S e a g e r ,W . R . , C l e m o n s , R . E . , a n d H a w l e y , J . W , 1 9 7 5 ,
Geology of Sierra Alta quadrangle, New Mexico: New
Mexico Bureau of Mines and Mineral Resources, Bull
1 0 2 , 5 6p .
Strain, W. S , 1966, Blancan mammalian fauna and pleistocene formations, Hudspeth County, Texas: Austin,
Texas Memorial Museum, Bull 10, 55 p
n
NewMexico's
minerals
Bishop Ash
Paarlelte typc-O
chalkywhire
minutelypumiceous
averaSe| 49+l 496
biotire
0 G0 7 perc€nt
06- 0t percenr
30-4Oppm
srlvergray
bubblewalls,juncrions
avetage | 499
ferroaugite
I 2-l 5 percenr
l0- 12 perc€nl
70-90 ppm
Conclusions
On the basis of fission-track age, chemical
similarity, petrography, and ash-shard morphology, the ash from Grama Gully correlates
with the Bishop Ash of Long Valley, California. The ash was ejected during a calderaforming event approximately 0.75 m.y. b.p.
The ash was carried westward by prevailing
winds and was deposited and preserved in an
overbank depression genetically and spatially
related to the ancestral Rio Grande. The sediments that preserve the ash reDresent an
overbank subfacies deposired during an aggradational cycle that culminated in the con_
struction of the Rincon surface sometime in
post-Bishop time, probably about 0.6-0.5
m.y. ago.
References
Borchardt, G. A., Harward, M. E., and Schmitt. R. A..
I 9 7 1 , C o r r e l a r i o n o f v o l c a n i c a s h d e p o s i t sb y a c r i v a t i o n
analysis of glass separates:euaternary Research,v. l, p.
247-260
B o r c h a r d t , G . A . , A r u s c a v a g e ,p . J . , a n d M i l l a r d , H . T . .
Jr., 1912, Correlation of the Bishop Ash, a pleistocene
marker bed, using instrumental neutron activation analv_
s i s :J o u r n a l o f S e d i m e n t a r yp e t r o l o g y , v . 4 2 , p . 3 0 1_ 3 0 6
Hawley, J. W., 1978, Correlarion chart 2-Middle to upper
Cenozoic stratigraphic units in selectedareas of the Rio
Crande rift in New Mexico, iz Guidebook to Rio Grande
rift in New Mexico and Colorado: New Mexico Bureau
of Mines and Mineral Resources,Circ 163. p.239
Izett, G. A., Wilcox, R. E.. powers, H.4..
and Desborough, C. A., 1970a, The Bishop Ash bed, a pleistocene marker bed in the western United States:euaternary
Research,v . l, p- l2l-132
-,
Wilcox, R. 8., Powers, H. A., and Desborough, G.
A., I970b, Pleistoceneash beds in California, Utah. Col_
orado, and Nebraska relared to rhe Bishop Tuff of Cali_
fornia: Geological Society of America, Abstracts with
Programs, v. 2, p. 336-337
Izett, G. A., Wilcox, R. E., and Borchardt, G. A., lg7l.
Correlation of a volcanic ash bed in pleistocene deposirs
a/
May 1982
New Mexico Geolog!
U.S. Boardon Geographic
Names
Pinatosa Canyon-canyon, 34 km (21 mi) long,
heads 5.6 km (3.5 mi) south-southeastof Callinas
Peak at 34"12'14'N., 105'45'46'w., trends
southwest to Largo Canyon 34 km (21 mi) north
of Carrizozo; Spanish word "pinatosa" means
"stand of measured pine"; in Lincoln County,
N e w M e x i c o ; s e c .2 0 , T . 4 S . , R . 1 0 E . ; 3 3 " 5 6 , 3 5 ,
N . , 1 0 5 ' 5 4 ' 4 0 " W . i n o t : P i n a t a s aC a n y o n , p i n a toso Canyon, Pintosa Canyon
Pinatosa Tank-tank,
in a tributary of Pinatosa
Canyon 8 km (5 mi) south of Gallinas peak and
20.9 km (13 mi) southwest of Corona; Spanish
word "pinatosa" means "stand of measured
pine"; in Lincoln County, New Mexico; sec. 33,
T. I S.,R. l1 E.; 34'10'40'N.. 105"47,48,,W.:
n o l . ' P i n t o s aT a n k .
Tecolote Peak-peak, elevation, 2,230 m (7,315 f0,
7.2 km (4.5 mi) north-northwest of Tecolote and
20.9 km (13 mi) southwest of Corona; Spanish
word "tecolote" means "owl"; in Lincoln Count y , N e w M e x i c o ; s e c .4 , T . 3 S . , R . 1 2 8 . : 3 4 " 0 4 ,
4 0 ' N . , 1 0 5 " 4 1' 1 8 ' W . ; n o t : C e r r o T e c o l o t e .
Cerro Tecolote Peak.
TABLE 4-Suvuanv or cHARACTERrsrrcs
oF
BlsHopAssaroPEARLErrE
rypE-Oesu(modified
from Izettandothers,1970b).
Color
Diagnoslic shard shape
Glass refracbvc index
Diagnostic phenocryst
Total iron (as qo FeO)
Tio,
Zn
names
Geographic
MACNETITE,FE,ON. BESSEMER
IRON PITS, FIERRO,
GRANTCoUNTY,NEw MExIco
Crystalsystem:isometric
Hardness:6
Specificgravity:5.18
Magnetic
Color: black
S p e c i m e np i c t u r e d : 3 / 2 " x 3 V 2 , ' a q o s sw i d e s tD o i n t
Magnetite, the most abundant member oi rhe soinel
group, is a common constituent of igneous rocks. The
specimen pictured is from a contact-metamorphic deposit
where a hot igneous intrusive body came into contact with
limestone. Copper, zinc, lead, gold, and silver mineralization also occur in the immediate area of this soecimen.
Magnetite is an important iron ore.
Golondrina Draw-watercourse, 13.7 km (8.5 mi)
l o n g , h e a d s a t 3 3 " 2 1 ' 2 5 " N . , 1 0 5 " 5 0 , 4 0 "W . ,
trends west-northwest to Three Rivers 2i km fi1
mi) west of Ruidoso; Spanish word "golondrina"
means "swallow"; in Otero County, New Merico;
s e c .1 3 ,T . l l S . , R . 9 E . ; 3 3 ' 2 1 ' 2 7 ' N . , 1 0 5 . 5 8 ,
0 4 " W . ; n o t . ' G o l o n d r i n aC r e e k .
Hasperos Canyon-canyon, 80 km (50 mi) tong,
heads in Jicarilla Mountains at 33053,36, N.,
1 0 5 ' 3 8 ' 2 3 ' W . , t r e n d s e a s t - s o u t h e a st to A r r o y o
del Macho 3l km (19 mi) north-northeast of Arabela and 69 km (43 mi) northwest of Roswell;
"hasperos" is a local Spanish word applied to a
white rock found in the canyon; in Lincoln
C o u n t y , N e w M e x i c o ; s e c .2 6 , T . 5 S . , R . l g E . ;
33'50'21' N., 105'01'42" W.; not: Big Asparos
Canyon, Hasparos Canyon.
-Oave Love.
NMBMlvlRCorrespondent
Photo b, K. S Ridel
quadrangle
Update
onNURE
reports
Neu')Mexico Geology, v. 3, no. 4 (November l98l) featured an article "Uranium resources
in New
Mexico-discussion of the NURE program," by Virginia T. Mclemore. Appendix I of that article
was a
list of available NURE quadrangle reports (DOE open-file reports) available at NMBMMR in
Socorro,
NM, and U.S. Doe in Grand Junction, CO. Following is an update of that list.
Quadrangle
Aztec
Brownfield
Carlsbad
Clifton
Clovis
Douglas
El Paso
Ft. Sumner
Hobbs
Las Cruces
Raton
Roswell
Silver City
Tucumcari
HSSR
GJBX-129(78),
321(81)
GJBX- 103(78),
50(76),3I 9(8l)
GJBX-415(81)
GJBX-69(78),359(81)
GJBX-69(78),244(81)
GJBX-21(77),345(8t)
GJBX-103(78),288(81)
GJBX-215(81),416(81)
GJBX-138(78),
358(81)
GJBX-69(78),320(81)
Tularosa
GJBX-104(78),215(Sl),326(81)
iPreliminaryreportsfor public
inspection.
ARMS
Folio
cJBx-65(80)
GJBX-33(76)
GJBX-412(81)
GJBX-23(79)
GJBX-33(76)
GJBX-23(79)
GJBX-412(81)
GJBX-412(81)
cJBX-228(80)
GJBX-412(81)
GJBX-9(80)
GJBX-412(81)
cJBX-23(79)
GJBX-33(76)
GJBX-67(79)
PCJ-012(80)r
PCJ-l l6(81)
PGJ-l l8(81)
GJQ-005(80)
PGJ-l3l(81)
PGJ-004(80)r