A new 40Ar/39Ar eruption age for the Mount Widderin volcano, Newer Volcanic Province, Australia, with implications for eruption frequency in the region

TL;DR: In this article, a new, high-precision 40Ar/39Ar age of 389 ± 8 ka (2σ) was reported for a Mount Widderin basalt sample.

Abstract: The Mount Widderin shield volcano is located near Skipton, western Victoria, in the Western Plains subprovince of the monogenetic Pliocene–Holocene Newer Volcanic Province (NVP). Radiometric ages for lavas in the Hamilton–Skipton–Derrinallum area are few, owing to limited suitable outcrop for K–Ar or 40Ar/39Ar geochronology studies. Existing age constraints for flows in this area have been inferred from Regolith Landform Units (RLUs), complemented by a small number of K–Ar studies on ≥1 Ma flows. Although the RLU approach provides a valuable overview of relative eruption ages across the NVP, it is of limited use in eruption frequency studies. Additional radio-isotopic ages are required to refine age ranges for individual RLUs, and to validate previous assignment of individual flows to specific RLUs. We report a new, high-precision 40Ar/39Ar age of 389 ± 8 ka (2σ) for a Mount Widderin basalt sample. Based on this age and geomorphic observations, we propose that both the Widderin and Elephant lava f...

Summary

Summary

• Ar laser step-heating analytical results for NVP26 groundmass.
• Table A2. 40Ar/39Ar ARGUSVI data and blank values for laser step-heating analysis of sample NVP26 excluding interference corrections.
• Ar age spectra and inverse isochron diagrams for individual NVP26 groundmass aliquants.
• Grey symbols are excluded from age calculation results.
• In inverse isochron diagrams, solid lines represent preferred isochron results and dashed lines indicate position of inverse isochrons constructed from all data points.

Full text

A new
40
Ar/
39
Ar eruption age for the Mount Widderin volcano,
Newer Volcanic Province, Australia, with implications for eruption
frequency in the region.
E. L. MATCHAN, E. B. JOYCE, AND D. PHILLIPS
School of Earth Sciences, The University of Melbourne, VIC 3010, Australia.
*Corresponding author: ematchan@unimelb.edu.au
SUPPLEMENTARY PAPERS
Australian Journal of Earth Sciences (2016) 63,
http://dx.doi.org/10.1080/08120099.2016.1156576
----------------------------------------------------------------------------------------------------------------
Copies of Supplementary Papers may be obtained from the Geological Society of
Australia's website (www.gsa.org.au), the Australian Journal of Earth Sciences
website (www.ajes.com.au) or from the National Library of Australia's Pandora
archive (http://nla.gov.au/nla.arc-25194).
----------------------------------------------------------------------------------------------------------------
SUPPLEMENTARY PAPERS
Table A1. ARGUSVI
40
Ar/
39
Ar laser step-heating analytical results for NVP26
groundmass.
Table A2.
40
Ar/
39
Ar ARGUSVI data and blank values for laser step-heating analysis
of sample NVP26 excluding interference corrections.
Figure A1.
40
Ar/
39
Ar age spectra and inverse isochron diagrams for individual NVP26
groundmass aliquants. Errors symbols are 1σ. Grey symbols are excluded from
age calculation results. In inverse isochron diagrams, solid lines represent
preferred isochron results and dashed lines indicate position of inverse
isochrons constructed from all data points. Step numbers are indicated.
Appendix B Supplementary information related to the contact between lava flows
from Mount Widderin and Mount Elephant.
Matchan et al. 2016 Australian Journal of Earth Sciences 63/2 Supplementary Papers http://dx.doi.org/10.1080/08120099.2016.1156576
1

Table A1. ARGUSVI
40
Ar/
39
Ar laser step-heating analytical results for NVP26 groundmass.
a,b,c,d
Sample
Step Laser
40
Ar ±1σ
39
Ar ±1σ
38
Ar ±1σ
37
Ar ±1σ
36
Ar ±1σ
39
Ar Cum.% Apparent
ID
No Power (x10
-14 39
Ar Age (ka)
mol)
d
NVP26-1 101.3 mg
NVP26-1a 1 4% 345.50 0.08 63.788 0.045 0.1344 0.0006 99.1 2.9 0.7128 0.0031 0.2264 2.719 0.081 38.41 2.080 0.015 17.98 401.604 2.8 0.7
NVP26-1b 2 6% 501.14 0.22 105.177 0.043 0.1812 0.0008 132.7 3.0 0.9615 0.0043 0.3734 2.208 0.050 42.72 2.035 0.012 47.63 392.884 2.4 0.6
NVP26-1c 3 9% 530.49 0.13 104.603 0.076 0.2008 0.0006 138.7 4.1 1.0655 0.0029 0.3713 2.320 0.068 40.03 2.030 0.009 77.12 391.926 1.7 0.4
NVP26-1d 4 12% 316.81 0.07 52.986 0.037 0.1329 0.0004 88.9 3.1 0.7050 0.0022 0.1881 2.937 0.104 33.56 2.007 0.013 92.06 387.339 2.4 0.6
NVP26-1e 5 18% 279.59 0.07 28.168 0.046 0.1422 0.0003 110.9 1.8 0.7542 0.0016 0.1000 6.888 0.110 19.46 1.932 0.017 100.00 372.937 3.4 0.9
Total gas age: 391.8 ± 4.7 (2σ)
NVP26-2 71.5 mg
NVP26-2a 1 4% 645.08 0.34 106.061 0.078 0.2676 0.0006 173.3 2.5 1.4197 0.0031 0.3765 2.859 0.041 34.29 2.086 0.009 18.78 402.608 1.8 0.5
NVP26-2b 2 6% 702.98 0.29 144.297 0.108 0.2572 0.0004 191.8 2.0 1.3645 0.0023 0.5123 2.327 0.025 42.05 2.049 0.005 44.33 395.444 1.0 0.3
NVP26-2c 3 8% 563.02 0.16 117.904 0.060 0.2037 0.0006 142.5 2.3 1.0804 0.0031 0.4186 2.115 0.034 42.71 2.039 0.008 65.20 393.696 1.6 0.4
NVP26-2d 4 10% 450.09 0.10 86.882 0.030 0.1731 0.0006 113.1 4.0 0.9182 0.0032 0.3084 2.278 0.081 39.09 2.025 0.011 80.59 390.944 2.2 0.6
NVP26-2e 5 14% 447.18 0.12 65.464 0.035 0.1992 0.0004 133.7 2.3 1.0570 0.0021 0.2324 3.575 0.061 29.43 2.010 0.010 92.18 388.052 1.9 0.5
NVP26-2f 6 20% 341.33 0.09 30.637 0.042 0.1757 0.0005 139.1 2.6 0.9319 0.0027 0.1088 7.948 0.146 18.49 2.060 0.026 97.60 397.680 5.1 1.3
NVP26-2g 7 30% 199.01 0.06 13.555 0.032 0.1060 0.0004 99.1 2.3 0.5625 0.0019 0.0481 12.794 0.302 15.61 2.292 0.043 100.00 442.346 8.3 1.9
Total gas age: 396.1 ± 4.0 (2σ)
NVP26-3 76.0 mg
NVP26-3a 1 4% 399.93 0.13 68.267 0.040 0.1644 0.0004 101.9 2.4 0.8724 0.0021 0.2423 2.613 0.063 34.87 2.043 0.009 16.45 394.387 1.8 0.5
NVP26-3b 2 6% 516.57 0.33 103.661 0.042 0.1942 0.0005 136.2 2.1 1.0303 0.0025 0.3680 2.299 0.036 40.45 2.016 0.008 41.42 389.151 1.5 0.4
NVP26-3c 3 8% 430.47 0.18 89.732 0.060 0.1588 0.0005 109.2 2.2 0.8426 0.0027 0.3185 2.130 0.044 41.56 1.994 0.009 63.04 384.867 1.8 0.5
NVP26-3d 4 10% 325.98 0.08 64.475 0.052 0.1243 0.0004 85.5 2.0 0.6592 0.0019 0.2289 2.322 0.054 39.62 2.003 0.009 78.57 386.710 1.7 0.4
NVP26-3e 5 14% 340.29 0.08 52.219 0.043 0.1488 0.0005 100.8 3.2 0.7895 0.0028 0.1854 3.377 0.108 30.73 2.002 0.016 91.15 386.548 3.1 0.8
NVP26-3f 6 30% 445.42 0.07 36.739 0.068 0.2361 0.0005 185.6 2.7 1.2523 0.0028 0.1304 8.842 0.128 16.06 1.947 0.023 100.00 375.808 4.5 1.2
Total gas age: 387.2 ± 4.3 (2σ)
NVP26-4
101.1 mg
NVP26-4a 1 4% 632.41 0.24 108.707 0.046 0.2586 0.0008 172.1 2.5 1.3720 0.0043 0.3859 2.771 0.040 35.23 2.050 0.012 19.72 395.637 2.3 0.6
NVP26-4b 2 6% 723.03 0.30 152.589 0.092 0.2607 0.0005 197.1 1.6 1.3828 0.0028 0.5417 2.260 0.019 42.90 2.033 0.006 47.40 392.419 1.1 0.3
NVP26-4c 3 8% 571.53 0.17 122.726 0.065 0.2054 0.0006 143.8 2.1 1.0895 0.0031 0.4357 2.051 0.030 43.09 2.007 0.008 69.67 387.349 1.5 0.4
NVP26-4d 4 10% 398.11 0.12 76.565 0.041 0.1559 0.0005 92.6 3.0 0.8271 0.0025 0.2718 2.116 0.070 37.97 1.974 0.010 83.56 381.126 1.9 0.5
NVP26-4e 5 14% 427.80 0.09 58.687 0.036 0.1977 0.0004 129.7 2.8 1.0487 0.0021 0.2083 3.868 0.084 26.82 1.955 0.011 94.21 377.346 2.1 0.6
NVP26-4f 6 30% 486.47 0.19 31.927 0.036 0.2690 0.0008 215.2 2.3 1.4270 0.0041 0.1133 11.798 0.128 12.42 1.892 0.039 100.00 365.248 7.5 2.0
Total gas age: 387.2 ± 4.1 (2σ)
NVP26-5
101.0 mg
NVP26-5a 1 4% 740.37 0.26 128.485 0.073 0.3001 0.0007 208.2 3.1 1.5920 0.0037 0.4561 2.836 0.042 35.80 2.063 0.009 22.89 398.219 1.7 0.4
NVP26-5b 2 6% 783.34 0.27 168.031 0.077 0.2798 0.0007 206.6 1.3 1.4843 0.0035 0.5965 2.152 0.013 43.43 2.025 0.007 52.83 390.826 1.3 0.3
NVP26-5c 3 8% 575.39 0.10 121.589 0.051 0.2090 0.0005 141.9 2.6 1.1088 0.0025 0.4316 2.043 0.037 42.47 2.010 0.006 74.50 387.942 1.2 0.3
NVP26-5d 4 10% 391.34 0.08 71.175 0.049 0.1575 0.0006 102.9 4.8 0.8358 0.0029 0.2527 2.529 0.118 36.24 1.992 0.012 87.18 384.597 2.4 0.6
NVP26-5e 5 14% 408.08 0.10 47.829 0.035 0.1968 0.0006 135.1 2.7 1.0439 0.0031 0.1698 4.944 0.098 23.63 2.016 0.019 95.70 389.134 3.7 1.0
NVP26-5f 6 30% 414.33 0.13 24.106 0.043 0.2322 0.0004 187.5 3.7 1.2321 0.0024 0.0856 13.612 0.270 11.22 1.928 0.030 100.00 372.221 5.8 1.6
Total gas age: 390.2 ± 3.8 (2σ)
b
Interference corrections: (
36
Ar/
37
Ar)
Ca
= (2.5713 ± 0.0023) x 10
-4
; (
39
Ar/
37
Ar)
Ca
= (6.6200 ± 0.0801) x 10
-4
; (
40
Ar/
39
Ar)
K
= (1.00 ± 0.05) x 10
-10
; (
38
Ar/
39
Ar)
K
= (1.2136 ± 0.0016) x 10
-2
c
J-value is 0.0001070135 ± 0.0000000648 ( 0.061%;1σ), based on an age of 1.1811 ± 0.0006 Ma (1σ) for AC sanidine (Phillips et al., submitted)
d
Sensitivity = 3.55 x 10
-17
mol/fA
Ca/K
±1σ
%
40
Ar*
±1σ
(%)
(fA)
(fA)
b
(fA)
(fA)
b
a
Data are corrected for mass spectrometer backgrounds, discrimination, radioactive decay and interference corrections (see Table A.2 for values excluding the interference correction). Errors are
one sigma uncertainties and exclude uncertainty in the J-value.
±1σ
40
Ar*/
39
Ar
±1σ
(fA)
Matchan et al. 2016 Australian Journal of Earth Sciences 63/2 Supplementary Papers http://dx.doi.org/10.1080/08120099.2016.1156576
2

Table A1. ARGUSVI
40
Ar/
39
Ar laser step-heating analytical results for NVP26 groundmass.
a,b,c,d
Sample
Step
ID
No
NVP26-1
101.3 mg
NVP26-1a 1
NVP26-1b 2
NVP26-1c 3
NVP26-1d 4
NVP26-1e 5
NVP26-2
NVP26-2a 1
NVP26-2b 2
NVP26-2c 3
NVP26-2d 4
NVP26-2e 5
NVP26-2f 6
NVP26-2g 7
NVP26-3
NVP26-3a 1
NVP26-3b 2
NVP26-3c 3
NVP26-3d 4
NVP26-3e 5
NVP26-3f 6
NVP26-4
NVP26-4a 1
NVP26-4b 2
NVP26-4c 3
NVP26-4d 4
NVP26-4e 5
NVP26-4f 6
NVP26-5
NVP26-5a 1
NVP26-5b 2
NVP26-5c 3
NVP26-5d 4
NVP26-5e 5
NVP26-5f 6
Background correction
Blank no.
40
Ar ±1σ
39
Ar ±1σ
38
Ar ±1σ
37
Ar ±1σ
36
Ar ±1σ
EXB#74 7.276 0.011 0.085 0.019 -0.121 0.043 0.020 0.027 0.03095 0.00053
EXB#75 7.787 0.024 0.056 0.017 -0.055 0.030 -0.002 0.032 0.03330 0.00021
EXB#75 7.787 0.024 0.056 0.017 -0.055 0.030 -0.002 0.032 0.03330 0.00021
EXB#76 7.792 0.013 0.086 0.022 -0.062 0.020 0.025 0.011 0.03381 0.00035
EXB#76 7.792 0.013 0.086 0.022 -0.062 0.020 0.025 0.011 0.03381 0.00035
EXB#82 3.336 0.016 0.060 0.018 -0.008 0.021 -0.014 0.015 0.01726 0.00011
EXB#82 3.336 0.016 0.060 0.018 -0.008 0.021 -0.014 0.015 0.01726 0.00011
EXB#83 3.393 0.019 0.092 0.017 -0.003 0.020 -0.009 0.015 0.01881 0.00014
EXB#83 3.393 0.019 0.092 0.017 -0.003 0.020 -0.009 0.015 0.01881 0.00014
EXB#83 3.393 0.019 0.092 0.017 -0.003 0.020 -0.009 0.015 0.01881 0.00014
EXB#84 3.429 0.010 0.102 0.022 -0.044 0.022 0.020 0.014 0.01812 0.00036
EXB#84 3.429 0.010 0.102 0.022 -0.044 0.022 0.020 0.014 0.01812 0.00036
EXB#89 2.515 0.025 0.081 0.008 -0.083 0.017 0.035 0.014 0.01532 0.00035
EXB#89 2.515 0.025 0.081 0.008 -0.083 0.017 0.035 0.014 0.01532 0.00035
EXB#89 2.515 0.025 0.081 0.008 -0.083 0.017 0.035 0.014 0.01532 0.00035
EXB#90 2.707 0.029 0.092 0.023 -0.093 0.012 0.012 0.012 0.01736 0.00047
EXB#90 2.707 0.029 0.092 0.023 -0.093 0.012 0.012 0.012 0.01736 0.00047
EXB#90 2.707 0.029 0.092 0.023 -0.093 0.012 0.012 0.012 0.01736 0.00047
EXB#91 3.219 0.017 0.088 0.022 -0.079 0.036 -0.012 0.013 0.01936 0.00012
EXB#91 3.219 0.017 0.088 0.022 -0.079 0.036 -0.012 0.013 0.01936 0.00012
EXB#91 3.219 0.017 0.088 0.022 -0.079 0.036 -0.012 0.013 0.01936 0.00012
EXB#92 3.523 0.014 0.081 0.004 -0.067 0.026 0.051 0.019 0.02015 0.00044
EXB#92 3.523 0.014 0.081 0.004 -0.067 0.026 0.051 0.019 0.02015 0.00044
EXB#92 3.523 0.014 0.081 0.004 -0.067 0.026 0.051 0.019 0.02015 0.00044
EXB#94 2.449 0.015 0.036 0.017 -0.051 0.013 -0.023 0.007 0.01431 0.00031
EXB#94 2.449 0.015 0.036 0.017 -0.051 0.013 -0.023 0.007 0.01431 0.00031
EXB#94 2.449 0.015 0.036 0.017 -0.051 0.013 -0.023 0.007 0.01431 0.00031
EXB#95 2.554 0.027 0.081 0.010 -0.040 0.011 0.018 0.020 0.01585 0.00021
EXB#95 2.554 0.027 0.081 0.010 -0.040 0.011 0.018 0.020 0.01585 0.00021
EXB#95 2.554 0.027 0.081 0.010 -0.040 0.011 0.018 0.020 0.01585 0.00021
(fA)
(fA)
(fA)
(fA)
(fA)
Matchan et al. 2016 Australian Journal of Earth Sciences 63/2 Supplementary Papers http://dx.doi.org/10.1080/08120099.2016.1156576
3

Table A2.
40
Ar/
39
Ar ARGUSVI data and blank values for laser step-heating analysis of sample NVP26 excluding interference corrections
a
Background correction
Sample Step Laser
40
Ar ±1σ
39
Ar ±1σ
38
Ar ±1σ
37
Ar ±1σ
36
Ar ±1σ
Blank no.
40
Ar ±1σ
39
Ar ±1σ
38
Ar ±1σ
37
Ar ±1σ
36
Ar ±1σ H1/Ax H1/L1 H1/L2 AX L1 L2 H1/CDD ±1σ
ID No
Power
[40] [40] [40] (1amu) (1amu) (1amu) (%)
NVP26-1 101.3 mg
NVP26-1a 1 4% 345.50 0.08 63.853 0.045 0.970 0.052 99.1 2.9 0.7383 0.0030
EXB#74
7.276 0.011 0.085 0.019 -0.121 0.043 0.020 0.027 0.03095 0.00053 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.402846 0.095942
NVP26-1b 2 6% 501.14 0.22 105.265 0.043 1.435 0.036 132.7 3.0 0.9957 0.0042
EXB#75
7.787 0.024 0.056 0.017 -0.055 0.030 -0.002 0.032 0.03330 0.00021 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.402846 0.095942
NVP26-1c 3 9% 530.49 0.13 104.695 0.076 1.491 0.035 138.7 4.1 1.1012 0.0027
EXB#75
7.787 0.024 0.056 0.017 -0.055 0.030 -0.002 0.032 0.03330 0.00021 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.402846 0.095942
NVP26-1d 4 12% 316.81 0.07 53.045 0.037 0.776 0.025 88.9 3.1 0.7279 0.0021
EXB#76
7.792 0.013 0.086 0.022 -0.062 0.020 0.025 0.011 0.03381 0.00035 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.402846 0.095942
NVP26-1e 5 18% 279.59 0.07 28.241 0.046 0.511 0.027 110. 9 1.8 0.7827 0.0015
EXB#76
7.792 0.013 0.086 0.022 -0.062 0.020 0.025 0.011 0.03381 0.00035 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.402846 0.095942
NVP26-2 71.5 mg
NVP26-2a 1 4% 645.08 0.34 106.176 0.078 1.561 0.029 173.3 2.5 1.4643 0.0030
EXB#82
3.336 0.016 0.060 0.018 -0.008 0.021 -0.014 0.015 0.01726 0.00011 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-2b 2 6% 702.98 0.29 144.424 0.108 2.006 0.032 191.8 2.0 1.4138 0.0022
EXB#82
3.336 0.016 0.060 0.018 -0.008 0.021 -0.014 0.015 0.01726 0.00011 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-2c 3 8% 563.02 0.16 117.998 0.060 1.653 0.030 142.5 2.3 1.1170 0.0031
EXB#83
3.393 0.019 0.092 0.017 -0.003 0.020 -0.009 0.015 0.01881 0.00014 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-2d 4 10% 450.09 0.10 86.957 0.030 1.186 0.023 113. 1 4.0 0.9472 0.0031
EXB#83
3.393 0.019 0.092 0.017 -0.003 0.020 -0.009 0.015 0.01881 0.00014 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-2e 5 14% 447.18 0.12 65.553 0.035 0.989 0.028 133.7 2.3 1.0914 0.0020
EXB#83
3.393 0.019 0.092 0.017 -0.003 0.020 -0.009 0.015 0.01881 0.00014 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-2f 6 20% 341.33 0.09 30.729 0.042 0.597 0.024 139.1 2.6 0.9677 0.0026
EXB#84
3.429 0.010 0.102 0.022 -0.044 0.022 0.020 0.014 0.01812 0.00036 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-2g 7 30% 199.01 0.06 13.620 0.032 0.299 0.027 99.1 2.3 0.5880 0.0018
EXB#84
3.429 0.010 0.102 0.022 -0.044 0.022 0.020 0.014 0.01812 0.00036 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-3 76.0 mg
NVP26-3a 1 4% 399.93 0.13 68.334 0.040 1.009 0.037 101.9 2.4 0.8986 0.0020
EXB#89
2.515 0.025 0.081 0.008 -0.083 0.017 0.035 0.014 0.01532 0.00035 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-3b 2 6% 516.57 0.33 103.752 0.042 1.533 0.024 136.2 2.1 1.0653 0.0024
EXB#89
2.515 0.025 0.081 0.008 -0.083 0.017 0.035 0.014 0.01532 0.00035 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-3c 3 8% 430.47 0.18 89.804 0.060 1.288 0.032 109.2 2.2 0.8707 0.0027
EXB#89
2.515 0.025 0.081 0.008 -0.083 0.017 0.035 0.014 0.01532 0.00035 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-3d 4 10% 325.98 0.08 64.531 0.052 1.037 0.016 85.5 2.0 0.6813 0.0018
EXB#90
2.707 0.029 0.092 0.023 -0.093 0.012 0.012 0.012 0.01736 0.00047 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-3e 5 14% 340.29 0.08 52.286 0.043 0.840 0.032 100.8 3.2 0.8155 0.0027
EXB#90
2.707 0.029 0.092 0.023 -0.093 0.012 0.012 0.012 0.01736 0.00047 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-3f 6 30% 445.42 0.07 36.862 0.068 0.778 0.028 185.6 2.7 1.3001 0.0027
EXB#90
2.707 0.029 0.092 0.023 -0.093 0.012 0.012 0.012 0.01736 0.00047 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-4 101.1 mg
NVP26-4a 1 4% 632.41 0.24 108.820 0.046 1.572 0.039 172.1 2.5 1.4162 0.0043
EXB#91
3.219 0.017 0.088 0.022 -0.079 0.036 -0.012 0.013 0.01936 0.00012 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-4b 2 6% 723.03 0.30 152.719 0.092 2.127 0.040 197.1 1.6 1.4335 0.0027
EXB#91
3.219 0.017 0.088 0.022 -0.079 0.036 -0.012 0.013 0.01936 0.00012 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-4c 3 8% 571.53 0.17 122.821 0.065 1.721 0.043 143.8 2.1 1.1265 0.0031
EXB#91
3.219 0.017 0.088 0.022 -0.079 0.036 -0.012 0.013 0.01936 0.00012 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-4d 4 10% 398.11 0.12 76.626 0.041 1.129 0.037 92.6 3.0 0.8510 0.0023
EXB#92
3.523 0.014 0.081 0.004 -0.067 0.026 0.051 0.019 0.02015 0.00044 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-4e 5 14% 427.80 0.09 58.773 0.036 0.971 0.026 129.7 2.8 1.0820 0.0020
EXB#92
3.523 0.014 0.081 0.004 -0.067 0.026 0.051 0.019 0.02015 0.00044 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-4f 6 30% 486.47 0.19 32.069 0.036 0.672 0.042 215.2 2.3 1.4824 0.0040
EXB#92
3.523 0.014 0.081 0.004 -0.067 0.026 0.051 0.019 0.02015 0.00044 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-5 101.0 mg
NVP26-5a 1 4% 740.37 0.26 128.622 0.073 1.943 0.075 208.2 3.1 1.6456 0.0036
EXB#94
2.449 0.015 0.036 0.017 -0.051 0.013 -0.023 0.007 0.01431 0.00031 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-5b 2 6% 783.34 0.27 168.168 0.077 2.360 0.016 206.6 1.3 1.5374 0.0035
EXB#94
2.449 0.015 0.036 0.017 -0.051 0.013 -0.023 0.007 0.01431 0.00031 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-5c 3 8% 575.39 0.10 121.683 0.051 1.692 0.021 141.9 2.6 1.1453 0.0024
EXB#94
2.449 0.015 0.036 0.017 -0.051 0.013 -0.023 0.007 0.01431 0.00031 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-5d 4 10% 391.34 0.08 71.243 0.049 0.999 0.043 102.9 4.8 0.8622 0.0027
EXB#95
2.554 0.027 0.081 0.010 -0.040 0.011 0.018 0.020 0.01585 0.00021 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-5e 5 14% 408.08 0.10 47.918 0.035 0.849 0.032 135.1 2.7 1.0787 0.0030
EXB#95
2.554 0.027 0.081 0.010 -0.040 0.011 0.018 0.020 0.01585 0.00021 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
NVP26-5f 6 30% 414.33 0.13 24.230 0.043 0.566 0.024 187.5 3.7 1.2803 0.0022
EXB#95
2.554 0.027 0.081 0.010 -0.040 0.011 0.018 0.020 0.01585 0.00021 1.001217 0.998905 0.993785 0.992794 0.990793 0.993521 320.505939 0.150435
(fA)
(fA)
(fA)
(fA)
(fA)
a
Data are corrected for mass spectrometer backgrounds, discrimination and radioactive decay.
Argus Sensitivity and Discrimination Corrections
(fA)
(fA)
(fA)
(fA)
(fA)
Matchan et al. 2016 Australian Journal of Earth Sciences 63/2 Supplementary Papers http://dx.doi.org/10.1080/08120099.2016.1156576
4

Figure'A1.'
40
Ar/
39
Ar(age(spectra(and(inverse(isochron(diagrams(for(individual(NVP26(groundmass(aliquants.(Errors(symbols(
are(1σ.(Grey(symbols(are(excluded(from(age(calculaHon(results.(In(inverse(isochron(diagrams,(solid(lines(represent(preferred(
isochron(results(and(dashed(lines(indicate(posiHon(of(inverse(isochrons(constructed(from(all(data(points.(Step(numbers(are(
indicated.(
300
320
340
360
380
400
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440
460
480
500
Age (ka)
300
320
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Age (ka)
Plateau steps are dark grey error symbols are 1σ
300
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Age (ka)
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0 20 40 60 80 100
Age (ka)
NVP26-1
Plateau age =391.1 ± 2.4 ka (2σ)
MSWD=1.6, p=0.2
Includes 74.1% of the
39
Ar
a
b
c
d
e
NVP26-2
Plateau age =394.4 ± 1.7 ka (2σ)
MSWD=1.9, p=0.2
Includes 61.8% of the
39
Ar
NVP26-3
Plateau age =387.1 ± 1.9 ka (2σ)
MSWD=1.1, p=0.3
Includes 74.7% of the
39
Ar
NVP26-4
f
g
h
1
2
3
4
5
0.0018
0.0020
0.0022
0.0024
0.0026
0.0028
0.0030
36
Ar/
40
Ar
39
Ar/
40
Ar
1
2
3
4
5
6
7
0.0018
0.0020
0.0022
0.0024
0.0026
0.0028
0.0030
1
2
3
4
5
6
0.0018
0.0020
0.0022
0.0024
0.0026
0.0028
0.0030
1
2
3
4
5
6
0.0018
0.0020
0.0022
0.0024
0.0026
0.0028
0.0030
0.04 0.08 0.12 0.16 0.20
error symbols are 1σ
36
Ar/
40
Ar
36
Ar/
40
Ar
36
Ar/
40
Ar
Cumulative %
39
Ar
NVP26-1
age = 403.3 ± 5.6 ka (2σ)
40
Ar/
36
Ar
i
= 292.7 ± 2.1 (2σ)
MSWD = 0.1
n = 4 of 5
NVP26-2
age = 393 ± 17 ka (95% CI)
40
Ar/
36
Ar
i
= 298.6 ± 5.2 (95% CI)
MSWD = 4
n = 5 of 7
NVP26-3
age = 391.6 ± 4.4 ka (2σ)
40
Ar/
36
Ar
i
= 296.3 ± 1.8 (2σ)
MSWD = 1.4
n = 5 of 6
NVP26-4
age = 395 ± 15 ka (95% CI)
40
Ar/
36
Ar
i
= 294.6 ± 5.9 (95% CI)
MSWD = 8.7
n =5 of 6
Matchan et al. 2016 Australian Journal of Earth Sciences 63/2 Supplementary Papers http://dx.doi.org/10.1080/08120099.2016.1156576
5