-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