-3000.00 -2000.00 -1000.00 0.00
-4000.00
-3500.00
-3000.00
-2500.00
-2000.00
-1500.00
-1000.00
-500.00
0.00
500.00
1000.00
Northing (m)
Eas
ting
(m)
Fieldarea
Summitridge
Supplementary Data A
DR2008025
Table 1. 40Ar/39Ar analytical data.ID Power 40Ar/39Ar 37Ar/39Ar 36Ar/39Ar 39ArK K/Ca 40Ar* 39Ar Age ±1σ
(Watts) (x 10-3) (x 10-15 mol) (%) (%) (Ma) (Ma)
BIT 301, 61.65 mg anorthoclase, J=0.0001079±0.25%, D=1.00562±0.00081, NM-168, Lab#=54212-02
A 8 0.5853 0.0143 1.745 34.8 35.7 12.1 14.4 0.0138 0.0028B 16 0.2064 0.0152 0.5172 76.0 33.6 26.5 45.9 0.0106 0.0009C 20 0.0878 0.0139 0.1440 62.0 36.8 52.9 71.6 0.0090 0.0006D 30 0.1024 0.0154 0.1630 55.2 33.2 54.3 94.4 0.0108 0.0007
X E 40 0.1467 0.0201 0.2013 13.4 25.4 60.6 100.0 0.0173 0.0027Integrated age ± 2σ n=5 241.4 33.9 ±0.5 0.0110 0.0011Plateau ± 2σ steps A-D n=4 MSWD=2.20 228.0 34.7 ±3.4 94.4 0.0100 0.0012
BIT 301, 41.10 mg anorthoclase, J=0.0001079±0.25%, D=1.00562±0.00081, NM-168, Lab#=54212-04
X A 8 0.6305 0.0147 1.817 25.0 34.7 15.0 20.4 0.0184 0.0028B 16 0.2301 0.0143 0.5119 39.7 35.8 34.8 52.7 0.0155 0.0014C 20 0.0874 0.0151 0.0800 40.6 33.7 74.5 85.7 0.0126 0.0008
X D 30 0.0899 0.0157 -0.0393 11.7 32.4 114.6 95.2 0.0200 0.0027X E 40 0.1083 0.0172 -0.1280 5.85 29.6 136.4 100.0 0.0287 0.0081
Integrated age ± 2σ n=5 122.8 34.3 ±0.8 0.0162 0.0018Plateau ± 2σ steps B-C n=2 MSWD=3.28 80.2 34.7 ±3.0 65.3 0.0135 0.0026
Bit 152, 268.25 mg anorthoclase, J=0.0001088±0.25%, D=1.00562±0.00081, NM-168, Lab#=54206-01
X A 4 16.16 0.0287 54.67 8.61 17.8 0.1 1.0 0.0021 0.0242X B 8 1.331 0.0126 3.577 101.0 40.6 20.7 12.8 0.0539 0.0019X C 12 0.7568 0.0138 2.088 147.3 37.0 18.6 29.9 0.0277 0.0011
D 16 0.3913 0.0134 0.8959 175.9 38.0 32.6 50.4 0.0250 0.0006E 20 0.2216 0.0131 0.3259 237.9 39.0 57.0 78.2 0.0248 0.0004F 25 0.2803 0.0152 0.4886 111.7 33.6 48.9 91.2 0.0269 0.0008G 30 0.2779 0.0141 0.5108 41.1 36.2 46.1 96.0 0.0251 0.0012
X H 35 0.2141 0.0163 0.3666 22.1 31.3 50.1 98.6 0.0210 0.0015X I 40 0.2872 0.0134 0.6066 12.2 38.1 38.0 100.0 0.0214 0.0025
Integrated age ± 2σ n=9 857.9 37.0 ±0.6 0.0287 0.0011Plateau ± 2σsteps D-G n=4 MSWD=2.00 566.7 37.4 ±4.8 66.1 0.0252 0.0008
BIT-152 an, G5&6:168, 250.42 inclusion free, J=0.0001091±0.10%, D=1.00562±0.00081, NM-168, Lab#=54207-01
X A 4 8.714 0.0227 28.56 8.45 22.4 3.2 1.0 0.0544 0.0174X B 8 1.410 0.0117 3.314 73.9 43.5 30.6 10.1 0.0849 0.0019
C 12 0.8719 0.0127 2.599 128.4 40.1 12.0 25.8 0.0206 0.0013
DR2008025
X A 4 21.12 0.0363 66.80 4.20 14.1 6.6 0.5 0.2739 0.0361X B 8 1.377 0.0104 2.319 51.4 49.3 50.3 6.1 0.1365 0.0021X C 12 0.7857 0.0083 0.9062 106.4 61.7 66.0 17.8 0.1023 0.0009X D 16 0.7835 0.0084 1.035 155.3 61.0 61.1 34.8 0.0943 0.0008
E 20 0.5312 0.0083 0.2069 256.8 61.2 88.6 62.9 0.0928 0.0004F 25 0.5019 0.0074 0.1395 204.9 69.1 91.9 85.4 0.0910 0.0004G 30 0.5335 0.0091 0.2177 76.1 56.1 88.1 93.7 0.0927 0.0007H 35 0.5355 0.0092 0.2405 34.4 55.2 86.9 97.5 0.0918 0.0013
X I 40 0.5630 0.0086 0.2868 22.6 59.3 85.1 100.0 0.0945 0.0018Integrated age ± 2σ n=9 912.1 60.2 ±1.0 K2O=11.13% 0.0971 0.0008Plateau ± 2σ steps E-H n=4 MSWD=4.06 572.2 63.0 ±12.7 62.7 0.0919 0.0011
BIT-157, 249.93mg anorthoclase, J=0.0001095±0.25%, D=1.00562±0.00081, NM-168, Lab#=54198-01
X A 4 29.09 0.0561 95.46 2.05 9.1 3.0 0.3 0.1739 0.0608B 8 1.009 0.0105 1.813 69.0 48.5 47.0 8.9 0.0936 0.0015C 12 0.7333 0.0074 0.8834 128.8 68.6 64.5 24.9 0.0933 0.0009D 16 0.5770 0.0080 0.3914 181.6 63.7 80.1 47.6 0.0911 0.0006E 20 0.5248 0.0088 0.2184 207.1 57.7 87.9 73.4 0.0909 0.0005F 25 0.5110 0.0077 0.1356 141.2 66.4 92.3 91.0 0.0930 0.0004G 30 0.5984 0.0099 0.4129 42.2 51.4 79.8 96.3 0.0941 0.0011
X H 35 0.5365 0.0108 0.3499 19.1 47.2 80.9 98.7 0.0856 0.0015X I 40 0.5920 0.0081 0.2613 10.8 62.9 87.1 100.0 0.1017 0.0028
Integrated age ± 2σ n=9 801.9 59.5 ±1.6 0.0924 0.0008Plateau ± 2σsteps B-G n=6 MSWD=3.98 769.9 61.4 ±16.4 96.0 0.0922 0.0010
BIT-158, 279.90 mg anorthoclase, J=0.0001098±0.25%, D=1.00562±0.00081, NM-168, Lab#=54170-01
X A 5 5.521 0.0192 15.22 13.9 26.6 18.6 1.5 0.2028 0.0104X B 10 0.8817 0.0135 1.037 155.2 37.8 65.4 18.1 0.1140 0.0008X C 15 0.6162 0.0112 0.2625 258.0 45.4 87.6 45.7 0.1068 0.0004
D 20 0.5695 0.0098 0.1391 293.0 52.2 92.9 77.0 0.1047 0.0003E 25 0.5643 0.0102 0.1247 133.6 49.9 93.6 91.3 0.1045 0.0004F 30 0.5787 0.0103 0.1842 33.2 49.5 90.8 94.8 0.1039 0.0009
X G 35 0.5920 0.0115 0.1332 19.1 44.4 93.5 96.9 0.1095 0.0016X H 40 0.9151 0.0143 1.442 15.8 35.7 53.6 98.6 0.0970 0.0027X I 45 4.747 0.0116 14.31 8.60 44.0 10.9 99.5 0.1027 0.0114X J 50 3.631 0.0129 10.39 4.89 39.5 15.5 100.0 0.1112 0.0160
Integrated age ± 2σ n=10 935.3 45.7 ±0.9 0.1083 0.0008Plateau ± 2σ steps D-F n=3 MSWD=0.32 459.9 51.3 ±2.9 49.2 0.1046 0.0006
Bit 158, 284.02 mg anorthoclase, J=0.0001097±0.25%, D=1.00562±0.00081, NM-168, Lab#=54171-01
X A 4 10.38 0.0202 31.63 7.44 25.2 10.0 0.8 0.2052 0.0195X B 8 1 015 0 0121 1 004 97 5 42 3 70 9 11 5 0 1422 0 0010
DR2008025
Bit 160, 241.9 mg anorthoclase, J=0.0001097±0.25%, D=1.00562±0.00081, NM-168, Lab#=54179-01
X A 4 28.79 0.0161 95.12 3.46 31.6 2.4 0.4 0.1350 0.0477X B 8 1.446 0.0072 3.046 61.8 70.4 37.8 8.2 0.1081 0.0020X C 12 1.255 0.0068 2.285 143.6 75.3 46.3 26.2 0.1148 0.0014
D 16 0.8817 0.0072 0.9759 174.7 71.3 67.4 48.1 0.1174 0.0008E 20 0.7407 0.0064 0.5084 197.7 79.7 79.8 72.9 0.1168 0.0006F 25 0.7153 0.0075 0.3770 135.1 68.0 84.5 89.8 0.1195 0.0007G 30 0.6973 0.0073 0.3227 51.7 70.0 86.4 96.3 0.1191 0.0010H 35 0.7197 0.0084 0.3798 19.6 60.6 84.5 98.8 0.1202 0.0021
X I 40 0.7651 0.0102 0.5494 9.74 50.1 78.9 100.0 0.1193 0.0044Integrated age ± 2σ n=9 797.4 72.0 ±1.7 0.1167 0.0012Plateau ± 2σsteps D-H n=5 MSWD=2.92 578.8 72.9 ±13.7 72.6 0.1181 0.0013
BIT-162, 184.55 mg anorthoclase, J=0.0001102±0.25%, D=1.00562±0.00081, NM-168, Lab#=54188-01
X A 4 26.36 0.0449 88.53 2.98 11.4 0.8 0.5 0.0395 0.0516B 8 2.384 0.0212 5.793 45.4 24.0 28.3 8.3 0.1338 0.0033C 12 1.475 0.0189 2.713 93.1 27.0 45.8 24.3 0.1340 0.0017D 16 1.250 0.0175 1.875 85.3 29.1 55.8 39.0 0.1384 0.0013E 20 0.8572 0.0164 0.6112 134.1 31.1 79.1 62.0 0.1346 0.0008F 25 0.8071 0.0173 0.4224 149.0 29.5 84.7 87.6 0.1357 0.0006G 30 0.7813 0.0196 0.3302 49.9 26.0 87.7 96.2 0.1360 0.0010H 35 0.7788 0.0194 0.3084 13.0 26.3 88.5 98.5 0.1368 0.0023I 40 0.7901 0.0225 0.3480 8.95 22.6 87.2 100.0 0.1368 0.0035Integrated age ± 2σ n=9 581.7 28.1 ±0.4 0.1349 0.0014Plateau ± 2σ steps B-I n=8 MSWD=1.14 578.8 28.5 ±5.7 99.5 0.1356 0.0009
BIT-163, 7 mg multicrystal aliquots, anorthoclase, J=0.0001101±0.25%, D=1.00562±0.00081, NM-168, Lab#=54190
X 06B 30 1.573 0.0213 2.009 12.177 24.0 62.4 0.1947 0.1947 0.004602B 30 1.235 0.0110 0.6627 8.515 46.5 84.2 0.2062 0.2062 0.003709B 30 1.163 0.0087 0.3799 9.580 58.7 90.4 0.2086 0.2086 0.003207B 30 1.372 0.0133 0.9602 13.844 38.3 79.4 0.2161 0.2161 0.002801B 30 1.264 0.0068 0.5791 8.501 75.6 86.5 0.2169 0.2169 0.003710B 30 1.391 0.0255 0.8049 13.454 20.0 83.1 0.2292 0.2292 0.003208B 30 1.496 0.0104 1.087 18.438 48.9 78.6 0.2331 0.2331 0.002604B 30 1.425 0.0079 0.6110 13.102 64.9 87.4 0.2470 0.2470 0.0024
X 05B 30 1.566 0.0114 0.6392 11.957 44.9 88.0 0.2734 0.2734 0.0045X 03B 30 7.716 0.0071 1.262 14.068 71.4 95.2 1.4562 1.4562 0.0046
Mean age ± 2σ n=7 MSWD=26.44 50.4 ±36.5 0.2257 0.2257 0.0116
Notes:
Sample preparation and irradiation:
DR2008025
20°C. Gas also exposed to a W filament operated at ~2000°C.
Analytical parameters: Electron multiplier sensitivity averaged 3.5 x 10-16 moles /pA.Total system blank and background averaged 548, 14.1, 1.0, 3.2, 2.8 x 10-18 moles. J-factors determined to a precision of ± 0.1% by CO2 laser-fusion of 6 single crystals from each of 6 radial positions
around the irradiation tray. Correction factors for interfering nuclear reactions were determined using K-glass and CaF2 and are as follows: (39Ar/37Ar)Ca = 0.00072 ± 2e-05 (36Ar/37Ar)Ca = 0.00028 ± 5e-06 (38Ar/39Ar)K = 0.01077 (40Ar/39Ar)K = 0.0002 ± 0.0003
Age calculations: Isotopic ratios corrected for blank, radioactive decay, and mass discrimination, not corrected for interfering reactions.Errors quoted for individual analyses include analytical error only, without interfering reaction or J uncertainties.Integrated age calculated by summing isotopic measurements of all steps.Integrated age error calculated by quadratically combining errors of isotopic measurements of all steps.Plateau or mean age is inverse-variance-weighted mean of selected steps or analyses, respectively.Plateau age or mean age error is inverse-variance-weighted mean error (Taylor, 1982) times root MSWD where MSWD>1.Decay constants and isotopic abundances after Steiger and Jäger (1977).X symbol preceding sample ID denotes analyses excluded from plateau age or mean age calculations.
DR2008025
%R
adK
/Ca
App
aren
t Age
(M
a)
%R
adK
/Ca
App
aren
t Age
(M
a)%
Rad
K/C
aA
ppar
ent A
ge (
Ma)
0
40
80
100
10
0 10 20 30 40 50 60 70 80 90 100
-0.10
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08
A
B
C D E F G H I
0.0252 ± 0.0008 Ma* (MSWD = 2.00, p = 0.11)
Integrated Age (54206) = 0.0287 ± 0.0011 Ma
A
B
C D E F G H I
Integrated Age (54207) = 0.0293 ± 0.0010 Ma
Cumulative %39Ar Released
H 0.0237 ± 0.0012 Ma (MSWD = 3.41)
C
b) BIT-152
0
40
80
100
10
0 10 20 30 40 50 60 70 80 90 100
0
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
B
CD E F G H I
0.0919 ± 0.0011 Ma (MSWD = 4.06)
Integrated Age (54197) = 0.0971 ± 0.0008 Ma
A
B C D E F GH
I
0.0922 ± 0.0010 Ma* (MSWD = 3.98)
Integrated Age (54198) = 0.0924 ± 0.0008 Ma
Cumulative %39Ar Released
c) BIT-157
e) BIT-160
g) BIT-163
a) BIT-301
d) BIT-158
f) BIT-162
0
40
80
100
10
0 10 20 30 40 50 60 70 80 90 100
-0.10
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08
A B C D E
0.0100 ± 0.0012 Ma (MSWD = 2.20)
Integrated Age (54212) = 0.0110 ± 0.0011 Ma
A B C D E
0.014 ± 0.002 Ma (MSWD = 3.17)
Integrated Age (54212) = 0.0162 ± 0.0018 Ma
AB
C DE
Integrated Age (54212) = 0.0452 ± 0.0016 Ma
Cumulative %39Ar Released
Supplementary Data C
0
40
80%Rad
10
100
K/Ca
0 10 20 30 40 50 60 70 80 90 1000
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
App. Age Ma
A4
B8
C12
D16
E20
F25
G30
H35I
40
0.1182 ± 0.0014 Ma* (MSWD = 2.92, p = 0.)
Integrated Age = 0.1168 ± 0.0013 Ma
Cumulative 39Ar Released
0
40
80%Rad
100
K/Ca
0 10 20 30 40 50 60 70 80 90 1000
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
App. Age Ma
A4
B8
C12
D16
E20
F25
G30
H35
I40
0.1358 ± 0.0011 Ma* (MSWD = 1.14, p = 0.3)
Integrated Age = 0.1351 ± 0.0016 Ma
Cumulative 39Ar Released
0
40
80
100
10
0 10 20 30 40 50 60 70 80 90 100
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0.22
0.24
A
BC D E F G
HIJ
Integrated Age (54170) = 0.1082 ± 0.0008 Ma
A
B
C D E F G H
0.1052 ± 0.0005 Ma (MSWD = 1.38, p = 0.25)
Integrated Age (54171) = 0.1109 ± 0.0007 Ma
Cumulative %39Ar Released
0.5
1
1.5
2
Mol 39Ar
60
80
100
%Rad
10
100
K/Ca
0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3 0.32 0.340
50
100
150
200
250
300
Prob
0.226 ± 0.012, MSWD = 26.44
Age (Ma)
DR2008025
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