Geochemistry, Geophysics, Geosystems
Supporting Information for
Age of the Lava Creek supereruption and magma chamber assembly from combined
40
Ar/39Ar and U-Pb dating of sanidine and zircon crystals
Naomi E. Matthewsa,b, Jorge A Vazquezb,c, Andrew Calverta
aVolcano
Science Center, United States Geological Survey, 345 Middlefield Road, Mail Stop 910, Menlo Park, CA,
94025, USA
bStanford-USGS Ion
cSHRIMP-RG
Microprobe Laboratory, Stanford University, CA, 94305, USA
Laboratory, United States Geological Survey, 345 Middlefield Road, Mail Stop 910, Menlo Park, CA,
94025, USA
Contents of this file
Figures S1 to S3
Tables S1 to S2
Captions for Datasets S1 to S3
Additional Supporting Information (Files uploaded separately)
Datasets S1 – Zircon U-Pb and trace element data
Datasets S2 – Sanidine 40Ar/39Ar data
Datasets S3 – Feldspar electron microprobe data
Introduction
The supporting information files comprise two supplementary figures and two tables that
compliment those presented with the main text. Datasets S1 and S2 provide full data tables
used to calculate U-Pb and Ar/Ar dates. Dataset S3 provides electron microprobe traverses that
document the compositions of sanidine crystals.
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Figure S1. Schematic stratigraphic column illustrating the stratigraphy of Lava Creek members
A and B at Virginia Cascade, Yellowstone National Park, USA. Note that the fallout bed of ash
at the base of Lava Creek B is covered by talus at road level. Samples 12NMYC05 and
12NMYC04 were collected from Lava Creek A and Lava Creek B, respectively, at this locality.
Stratigraphic column is adapted from Christiansen [2001].
2
Figure S2. Plot showing 230Th-corrected 206Pb/238U date for the average Lava Creek zircon
crystal face as a function of assumed whole rock or glass Th/U and melt (230Th)/(238U)
disequilibrium at the time of zircon crystallization. Melt disequilibrium values are based on
eruption age-corrected (230Th)/(238U)0 ratios for young Yellowstone [Vazquez and Reid, 2002]
and Alid volcanic center, Eritrea, rhyolites [Lowenstern et al., 2006]. (230Th)/(238U) = 1 = secular
equilibrium.
3
Figure S3. CL images and barium concentrations across sanidine crystals from Lava Creek
members A (A), and member B (B).
Sample
Member
Sample type
Locality name
Latitude
Longitude
12NMYC01
Lower A
Pumice
Tuff Cliff, Y.N.P.
N44°39.123'
W110°49.828'
JVYC-19
Lower A
Pumice
Tuff Cliff, Y.N.P.
N44°39.123'
W110°49.828'
12NMYC05
Upper A
Welded ignimbrite
Virginia Cascade, Y.N.P.
N44°42.810'
W110°38.905'
12NMYC04
Upper B
Welded ignimbrite
Virginia Cascade, Y.N.P.
N44°42.908'
W110°39.353'
12NMYC06
Lower B
Basal bedded ash
Flagg Ranch, WY
N44°05.938'
W110°40.041'
LCT01
Distal B
Distal ash
Shoshone, CA
N35°58.830'
W116°14.991'
Table S1. Details of Lava Creek Tuff and tephra samples. Samples collected from Yellowstone
National Park (Y.N.P.), Wyoming (WY), and California (CA); localities are shown on Figure 1.
4
Sample #
6YC-146WR
8YC-371A
74Y-180B
8YC-408E
7YC-311A
7YC-185
65YR-27A
37
38
39
7A
7B
7C
8
Location
Type
WR
WR
WR
WR
WR
WR
WR
G
G
G
G
G
G
G
LCT mbr.
B
A
A
B
B
B
B
B
B
B
B
B
B
B
Shoshone, CA
Shoshone, CA
Shoshone, CA
Onion Creek, UT
Onion Creek, UT
Onion Creek, UT
Shoshone, CA
9
Shoshone, CA
G
B
11
65W78
67W43
217622
216925
216926
234832
263919
Ventura, CA
Freemont Co.,WY
Shell Cyn.,WY
Wyoming
Wyoming
Wyoming
Wyoming
Wyoming
G
G
G
G
G
G
G
G
B
A
A
A
A
A
A
A
Description
glassy ignimbrite
upper A, vitrophyric ignimbrite
upper A, vitrophyric ignimbrite
vitrophyric ignimbrite
glassy nonwelded ignimbrite
glassy nonwelded ignimbrite
vitrophyric ignimbrite
tephra shards
tephra shards
tephra shards
tephra shards
tephra shards
tephra shards
tephra shards
(5-15 cm above base of fallout bed)
tephra shards
(0-7 cm above base of fallout bed)
tephra shards
tephra shards
tephra shards
tephra shards
tephra shards
tephra shards
tephra shards
tephra shards
[Th]
30.0
31
25
30
31
29
25
30.0
29.2
29.0
29
28.9
29.0
29.7
[U]
6.55
7.3
5.2
8.2
7.3
6.2
4.4
6.6
5.8
6.3
6
6.2
6.4
6.5
Th/U Ref. Analysis type
4.58 1 ID-TIMS
4.2 2 INAA
4.8 2 INAA
3.7 2 INAA
4.2 2 INAA
4.7 2 INAA
5.7 2 INAA
4.5 3 INAA
5.1 3 INAA
4.6 3 INAA
4.8 4 INAA
4.7 4 INAA
4.5 4 INAA
4.6 4 INAA
Lab
USGS
USGS
USGS
USGS
USGS
USGS
USGS
USGS
USGS
USGS
Livermore NL
USGS, Reston
USGS
USGS
29.9
6.5
4.6
4
INAA
Livermore NL
29.8
31.7
30.8
33.1
30.7
31.7
32.2
34.0
6.4
8.6
8.8
8.3
9.7
9.7
10.4
9.7
4.7
3.7
3.5
4.0
3.2
3.3
3.1
3.5
4
5
5
5
5
5
5
5
INAA
INAA
INAA
INAA
INAA
INAA
INAA
INAA
USGS
USGS
USGS
USGS
USGS
USGS
USGS
USGS
Table S2. Th and U concentrations for glassy Lava Creek whole rock and tephra samples. Table lists glassy Lava Creek whole rocks (WR) or
tephra glass shards (G) used in this study to estimate average Th/Umelt for adjustment of 206Pb /238U dates. Location of samples and members
(LCT mbr.) are from references: 1: Doe et al. [1982]; 2: Christiansen [2001], 3: Sarna-Wojcicki et al. [1984], 4: Sarna-Wojcicki et al. [1987], and 5:
Glen Izett [USGS unpublished data]. YNP: Yellowstone National Park, USA. [Th] and [U] concentrations are in parts per million. INAA: induced
neutron activation analysis; ID-TIMS: isotope dilution thermal ionization mass spectrometry. Analyses performed at USGS labs [Denver unless
noted] or Lawrence Livermore National Lab (NL), CA.
5
Data Set S1. U-Pb and trace element data for Lava Creek zircons. 206Pb/238U dates are
corrected for common Pb using a 207Pb correction [Williams, 1998] with a value (207Pb/206Pb =
0.896) from Lava Creek feldspar as reported in Doe et al. [1982], and corrected for initial 238U230
Th disequilibrium using the method of Schärer [1984] assuming a parent melt with Th/U of
3.5 ± 0.3 (1 s.d) and 4.7 ± 0.2 (1 s.d) for crystal faces from members A and B, respectively, and
4.6 ± 0.6 for intermediate zones and cores, and an initial melt (230Th)/(238U)=1.20 ± 0.15 (1 s.d.).
See Table S2 for sources of assumed parent melt compositions and text for discussion.
206
Pb/238U dates for crystal faces on Bishop Tuff zircons are corrected in the same manner, with
common Pb and melt Th/U values from Crowley et al. [2007] and assumption of secular
equilbrium. Trace element concentrations are calibrated to 91500 zircon standard using
working values reported by Wiedenback et al. [2004]. Reported uncertainties are at 1-sigma
level. Italicized analyses are excluded from weighted means. Ti concentrations are calibrated
to SL13 zircon [Hiess et al., 2008], and Ti-in-zircon temperatures (T°C) are derived from
formulation of Ferry and Watson [2007] assuming SiO2 activity = 1.0 and TiO2 activity = 0.3
based on TiO2 saturation model of Hayden and Watson [2007] and the Lava Creek tephra
composition reported by Perkins and Nash [2002]. Analysis type column lists crystal domain
sampled via ion microprobe. The provenance of the individual zircons and their host rock in the
Lava Creek Tuff stratigraphy is denoted by TC-A (lower member A, Tuff Cliff, Yellowstone
National Park), VC-A (upper member B, Virginia Cascade, Yellowstone National Park), Basal-B
(lower member B fallout, Virginia Cascade, Yellowstone National Park), VC-B (upper member B,
Virginia Cascade, Yellowstone National Park), and Tecopa-B (distal member B, Lake Tecopa
beds, Shoshone, California); b.d. = below detection; n.m. = not measured. Decay constants
used: λ238U=1.55125 (± 0.0535%) X 10-10 yr-1 (Jaffey et al., 1971; Steiger and Jäger, 1977), λ230Th =
9.17052 (± 0.0133%) X 10-6 yr-1 (Cheng et al. 2013).
Data Set S2. Sanidine 40Ar/39Ar data. Notes: Italicized analyses are excluded from isochron
and mean single crystal dates. Dates are calculated using 40K total decay constant 5.543 (±
0.020) X 10-10 yr-1 (1) from Steiger and Jäeger (1977) with uncertainty from Min et al. (2000),
and relative to Bodie Hills fluence monitor, referenced to a Fish Canyon sanidine age of 28.172 ±
0.014 Ma (1, Rivera et al., 2011) with R (BH/FC) conversion value of 0.346717 ± 0.000402 (1).
Isotopes are reported in volts (4.87 X 10-14 moles/volt), and corrected for blank, background,
discrimination, and decay.
Data Set S3. Electron microprobe data. Feldspar separates from Lava Creek Tuff member A
samples: 12NMYC01, 12NMYC05 and 8YC-413. Sample 8YC-413 is a vitrophyric welded pumice
studied by Gansecki et al. (1998) and dated by Lanphere et al. (2002). Feldspar separates from
LCT member B samples: 7YC-325, 8YC-411, OYC-553, 12NMYC06, 12NMYC04 and 12NMYC07.
Sample 12NMYC07 is basal welded ignimbrite from Flagg Ranch locality, collected directly
above the basal ash. Sample 7YC-425 is basal vitrophyre, 8YC-411 is top pumice, and OYC-553
is fallout ash near source; all studied by Gansecki et al. (1998) and dated by Lanphere et al.
(2002).
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