The cosmic-ray exposure history of the Twannberg iron meteorite (IIG)


The cosmic-ray exposure history of the Twannberg iron meteorite (IIG)

Smith, T.; Hofmann, B. A.; Leya, I.; Merchel, S.; Pavetich, S.; Rugel, G.; Scharf, A.

The Twannberg iron meteorite is one out of only six members of the group IIG. The numerous finds of Twannberg meteorites in recent years have challenged our knowledge about its cosmic-ray exposure history and especially on the time of fall with respect to glacial events. The combined noble gas and radionuclide data obtained in this new systematic study indicate that Twannberg was a large object with a pre-atmospheric radius in the range of 2-4 meters, which corresponds to ~1000 tons. The cosmic-ray exposure age for Twannberg is 66.0±7.8 Ma. The most surprising result is the long terrestrial age of Tterr = 202 +19 -20 ka, which is unexpected considering the humid conditions in Switzerland. However, this age is in accord with glaciation events, indicating that the less shielded samples from Mt. Sujet still represent the original strewnfield but that the samples from Gruebmatt and Twannbach, which are from more shielded positions, have been glacially transported during the second last ice age from an original position west of Mt. Sujet towards east-north-east.

Keywords: AMS; cosmic rays; accelerator mass spectrometry; exposure age; terrestrial age; meteorite

Related publications

Permalink: https://www.hzdr.de/publications/Publ-24306
Publ.-Id: 24306