Table 3. 40Ar/39Ar Dating of feldspars in Leg 165 tephra layer.

Core, section, interval (cm)
Analysis
number
40Ar/39Ar
38Ar/39Ar
37Ar/39Ar
36Ar/39Ar
39Ar
40Ar*
(%)
40Ar*/39Ar
Age
(Ma)
±
(m.y.)
wi
xi*wi
Mean (Ma)
Error (Ma)
165-999A-                            
48X-6, 43 1 1.80 0.013 1.62 0.0010 16.3 84.36 1.516 16.21 3.17 0.10 1.62    
48X-6, 43 2 1.77 0.012 1.43 0.0016 20.2 73.72 1.302 13.93 2.56 0.15 2.12    
48X-6, 43 3 1.69 0.012 0.59 0.0006 23.3 89.06 1.504 16.08 2.22 0.20 3.27    
48X-6, 43 4 2.11 0.013 0.77 0.0009 36.4 87.75 1.854 19.79 1.42 0.49 9.79    
48X-6, 43 5 1.75 0.013 0.96 0.0000 38.0 99.85 1.743 18.62 1.36 0.54 10.07    
48X-6, 43 6 1.69 0.012 0.81 0.0000 33.9 100.00 1.693 18.08 1.53 0.43 7.77    
48X-6, 43 7 1.82 0.014 1.09 0.0013 32.6 78.82 1.436 15.35 1.59 0.40 6.10    
48X-6, 43 8 1.81 0.012 1.73 0.0013 32.7 79.26 1.431 15.30 1.58 0.40 6.10    
48X-6, 43 9 1.83 0.010 1.84 0.0016 22.8 74.08 1.359 14.53 2.26 0.20 2.83    
48X-6, 43 10 1.88 0.014 0.71 0.0008 39.5 87.42 1.644 17.57 1.10 0.83 14.60    
48X-6, 43 11 2.00 0.017 0.05 0.0024 12.9 65.23 1.304 13.94 3.36 0.09 1.23    
48X-6, 43 12 2.08 0.017 0.43 0.0012 23.4 83.12 1.730 18.47 1.85 0.29 5.42    
48X-6, 43 13 2.31 0.014 0.57 0.0033 40.2 57.48 1.329 14.21 1.08 0.86 12.16    
48X-6, 43 14 1.96 0.015 0.27 0.0014 81.8 78.37 1.535 16.40 0.54 3.47 56.96    
48X-6, 43 15 1.91 0.021 0.38 0.0014 31.5 78.30 1.497 16.00 1.38 0.53 8.46    
48X-6, 43 16 2.15 0.015 0.28 0.0024 52.4 66.58 1.432 15.30 0.83 1.45 22.26    
                          16.36
0.31

Notes: %Atm = 100*[(40Ar/39Ar-295.5*36Ar/39Ar)40Ar/Ar]. 40Ar*/39Ar = the ratio of the radiogenic isotope of argon (40Ar) to the 39Ar produced in the reactor from potassium. wi = the weighting used in the weighted mean and is the inverse of variance on each measurement. xi*wi = the weighting multiplied by the measured age of each measurement.