Results of 40Ar/39Ar laser single-grain fusion experiments

No.	Atmos.(%)	36Ar/39Ar	37Ar/39Ar	38Ar/39Ar	40Ar/39Ar	40Ar/36Ar	Date (Ma)

	1	  2.05	.14629E-03	.20520E-02	.58100E-01	.21317E+01	.14572E+05	  12.9	±	  .2
	2	   .57	.40119E-04	.36107E-03	.55360E-01	.21137E+01	.52684E+05	  13.0	±	  .1
 	3	 89.28	.55335E-01	.36624E+00	.51492E-01	.18313E+02	.33095E+03	  12.3	±	 4.8
 	4	 23.54	.20145E-02	.94554E-04	.57934E-01	.25576E+01	.12696E+04	  12.1	±	  .1
 	5	 22.74	.20174E-02	.11312E-01	.45500E-01	.26466E+01	.13119E+04	  12.6	±	  .3
 	6	  1.21	.84008E-04	.24194E-03	.41655E-01	.20725E+01	.24671E+05	  12.6	±	  .2
 	7	   .31	.19622E-04	.20183E-03	.37899E-01	.18841E+01	.96021E+05	  11.6	±	  .3
 	8	 20.24	.17544E-02	.12506E-01	.50395E-01	.25855E+01	.14737E+04	  12.7	±	  .1
 	9	 24.79	.23261E-02	.19340E-03	.46673E-01	.28010E+01	.12042E+04	  13.0	±	  .2
 10	 21.53	.19614E-02	.16673E-03	.47391E-01	.27210E+01	.13873E+04	  13.2	±	  .2
 11	  6.31	.45217E-03	.27590E-03	.44643E-01	.21453E+01	.47443E+04	  12.4	±	  .3
 12	  2.01	.13768E-03	.23602E-03	.58268E-01	.20502E+01	.14891E+05	  12.4	±	  .1
 13	 34.76	.37100E-02	.18851E-03	.52264E-01	.31826E+01	.85784E+03	  12.9	±	  .1
 14	 41.19	.48098E-02	.15811E-01	.52889E-01	.34767E+01	.72285E+03	  12.7	±	  .6
 15	 36.29	.38062E-02	.10490E-01	.52036E-01	.31257E+01	.82121E+03	  12.3	±	  .2
 16	  7.28	.55391E-03	.78873E-02	.47137E-01	.22692E+01	.40967E+04	  13.0	±	  .3
 17	  1.42	.10547E-03	.84372E-03	.46334E-01	.22172E+01	.21023E+05	  13.5	±	  .4
 18	 28.75	.27918E-02	.15263E-03	.48484E-01	.28979E+01	.10380E+04	  12.8	±	  .1
 19	 15.08	.12092E-02	.14781E-03	.46319E-01	.23984E+01	.19835E+04	  12.6	±	  .1
 20	  3.18	.22977E-03	.30636E-03	.44426E-01	.21598E+01	.94000E+04	  12.9	±	  .2
 21	 15.34	.12562E-02	.22745E-01	.38733E-01	.24379E+01	.19407E+04	  12.8	±	  .3
 22	 14.85	.11707E-02	.47757E-02	.45889E-01	.23558E+01	.20124E+04	  12.4	±	  .5
 23	 28.67	.27161E-02	.21850E-03	.49493E-01	.28282E+01	.10413E+04	  12.5	±	  .3
 24	 29.34	.27337E-02	.23459E-03	.47997E-01	.27823E+01	.10178E+04	  12.2	±	  .2
 25	 16.67	.13477E-02	.55132E-03	.40361E-01	.24179E+01	.17941E+04	  12.4	±	  .7

J-value =  .00347774 ±  0.00001195
Total Gas Age =  12.6 ± 0.1 Ma
Mean Age = 12.6  STDEV = 0.4Ma

Note:
J-value: Weighted mean of three fusions of irradiation standard LP-6 biotite standards (Odin et al. 1982)
The date is obtained by using the following equations: 
	Date = , and 
		
where [ ]Ca and [ ]K = isotope ratios of argon extracted from irradiated calcium and potassium salts (values cited in the text) and [ ]m = isotope ratio of argon extracted from irradiated unknown. 
Date (Ma) = the date calculated using the following decay constants: le = 0.581x10-10yr -1; 
	lb = 4.962x10-10 yr-1; l = 5.543 x 10-10 yr-1;  40K/K = 0.01167 atom %  (Steiger and Jäger, 1977).  
The quoted error is one standard deviation and does not include the error in the standard error, or the error in the interference corrections.