The measurement and data reduction methods were described by Hasan et al. (1987, Proc. 17th LPSC E703-E709; 1989, LPSC XX, 383-384). For meteorites whose TL lies between 5 and 100 krad the natural TL is related primarily to terrestrial history. Samples with NTL <5 krad have TL below that which can reasonably be ascribed to long terrestrial ages. Such meteorites have had their TL lowered by heating within the past million years or so (by close solar passage, shock heating, or atmospheric entry), exacerbated, in the case of certain achondrite classes, by "anomalous fading". We suggest that meteorites with NTL >100 krad are candidates for an unusual history involving high radiation doses and/or low temperatures.
NTL
[krad at
Sample Class 250 deg. C]
EET 92002 CK4 2.7 ± 0.4
EET 92042 CR2 22 ± 3
EET 92003 EUC 0.13 ± 0.04
EET 92004 EUC 0.21 ± 0.03
EET 92001 MESO 3 ± 1
EET 92033 H5 33.2 ± 0.1
EET 92035 H5 168 ± 1
EET 92040 H5 113 ± 3
EET 92044 H5 39.0 ± 0.1
EET 92045 H5 10.1 ± 0.1
EET 92041 L5 2.2 ± 0.4
PCA 91157 L5 7.5 ± 0.2
PCA 91169 L5 1.5 ± 0.1
RKP 92405 L5 0.08 ± 0.01
BEC 92601 L6 47.2 ± 0.3
EET 92030 L6 16.4 ± 0.2
EET 92031 L6 29.8 ± 0.5
EET 92032 L6 30.4 ± 0.3
EET 92034 L6 0.16 ± 0.03
EET 92036 L6 30.9 ± 0.1
EET 92037 L6 51.9 ± 0.4
EET 92043 L6 85 ± 1
EET 92046 L6 66.2 ± 0.8
PCA 91219 L6 74.8 ± 0.3
RKP 92404 LL6 3 0.6 ±0.6
The quoted uncertainties are the standard deviations shown by replicate measurements of a single aliquot.
COMMENTS: The following comments are based on natural TL data, TL sensitivity, the shape of the induced TL glow curve, classifications, and JSC and Arkansas group sample descriptions.