Table 1.

Furnace argon isotopic results for MZ-7 glass

Step	Temp, °C	40Ar/39Ar	37Ar/39Ar	36Ar/39Ar (×10−3)	39ArK (×10−15 mol)	K/Ca	40Ar*, %	39Ar, %	Age, Ma	±1 σ, Ma
A	550	10385	0.2738	35070	0.132	1.9	0.2	0.4	32	504
B	600	134.3	0.5938	435.1	1.03	0.86	4.3	3.1	8.4	1.5
C	650	69.96	0.6300	201.8	2.71	0.81	14.8	10.3	14.96	0.51
D	700	52.46	0.6468	131.1	2.43	0.79	26.2	16.7	19.81	0.53
E	730	53.10	0.7097	121.3	6.31	0.72	32.6	33.5	24.90	0.32
F	760	47.85	0.7493	96.78	4.84	0.68	40.3	46.3	27.75	0.27
G	800	53.06	0.7971	107.3	6.25	0.64	40.3	62.9	30.75	0.29
H	830	59.22	0.8182	125.6	5.39	0.62	37.4	77.2	31.83	0.34
I	870	71.23	0.8627	164.1	4.11	0.59	32.0	88.1	32.74	0.45
J	900	118.9	0.9004	329.1	2.40	0.57	18.3	94.5	31.17	0.76
K	950	318.3	0.9827	1007.8	1.39	0.52	6.5	98.2	29.6	2.6
L	1000	1302.7	0.8560	4331	0.688	0.60	1.8	100.0	33.0	14.0
Total gas age					37.7	0.67			27.3	2.5

MZ-7 glass, sample mass = 19.73 mg, J (radiation parameter for neutron flux) = 0.0008025, Laboratory sample 8955–01. ⁴⁰Ar* indicates radiogenic ⁴⁰Ar.