|
Core, section, interval (cm)
|
Designation
|
|
Material
|
Total gas age
(Ma) |
±2 sd
|
39Ar (%)
|
Plateau
age (Ma) |
±2 sd
|
Steps
used
|
MSWD
|
Isochron age
(Ma) |
±2 sd
|
MSWD
|
40Ar/36Ar (initial)
|
±2 sd
|
||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Depth (mbsf) | |||||||||||||||||
|
Top
|
Bottom
|
Average
|
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| 183-1138A- |
|
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|
|
|
|
|
|
|
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|
|
|
|
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|
|
| 12R-3, 5-7 | A1 | 105.35 | 105.37 | 105.36 | Glass | 7.98 | 0.39 | 60.80 | 7.07 | 0.37 | 3 of 5 | 1.10 | 5.99 | 0.71 | 1.34 | 311 | 6 |
| 13R-1, 22-24 | A2 | 112.22 | 112.24 | 112.23 | Biotite | 6.53 | 0.14 | 98.70 | 6.43 | 0.14 | 6 of 7 | 1.15 | 6.39 | 0.14 | 1.15 | 305 | 11 |
| 15R-1, 73-75 | A3 | 131.93 | 131.95 | 131.94 | Glass | 16.47 | 1.68 | 83.30 | 12.22 | 1.47 | 3 of 6 | 1.02 | 6.93 | 2.96 | 0.02 | 306 | 4 |
| 19R-1, 110-112 | A4 | 170.80 | 170.82 | 170.81 | Biotite | 11.32 | 0.25 | 99.70 | 11.31 | 0.25 | 8 of 8 | 1.24 | 11.28 | 0.26 | 1.24 | 297 | 17 |
| 19R-1, 110-112 | A5 | 170.80 | 170.82 | 170.81 | Glass | 11.44 | 0.39 | 99.50 | 11.57 | 0.36 | 6 of 7 | 1.53 | 11.83 | 0.39 | 1.53 | 286 | 9 |
Notes: MSWD = mean square weighted deviation. All ages calculated relative to neutron fluence monitor FCT-2 biotite (28.04 ± 0.12 Ma), decay and abundance constants le = 0.581 x 10-10/yr; lb = 4.961 x 10-10/yr; 40K/K = 1.17 x 10-4, and corrected for 37Ar decay (half-life = 35.1 days) and interfering isotopes 36Ar/37Ar[Ca] = 2.64 x 10-4, 39Ar/37Ar[Ca] = 6.73 x 10-4, 40Ar/39Ar[K] = 1.0 x 10-3. Bold entries are considered the best estimates of crystallization ages (see text).