Cosmogenic isotopes terrestrial

Another method uses the decay of cosmogenic isotopes that are produced in the atmosphere and then incorporated into terrestrial reservoirs. Examples of this approach include standard 14C and l0Bc dating. 

Kouwenberg LLR, Kiirschner WM, McElwain JC (2007) Stomatal frequency change over altitudinal gradients prospects for paleoaltimetry. Rev Mineral Geochem 66 215-242 Lai D (1988) In situ-produced cosmogenic isotopes in terrestrial rocks. Ann Rev Earth Planet Sci 16 355-388 Lai D (1991) Cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models. Earth Planet Sci Lett 104 424-439... 

Lai, D. (1988) In situ-produced cosmogenic isotopes in terrestrial rocks. Ann. Rev. Earth Planet. Sci., 16, 355-88. 

Terrestrial Cosmogenic isotopes and their Production Rates... 

The W/ W ratios of lunar rocks have been difficult to determine because there is significant W production via neutron-capture of Ta during prolonged cosmic-ray exposure of the lunar surface 30, 32). This problem has now been overcome by analyzing metals from lunar basalts 30). These metals contain no Ta and hence no cosmogenic W. Touboul et al. 33) obtained W isotope data for metals from a comprehensive set of lunar rocks and showed that probably all lunar samples have Sw values of 0. Hence, the lunar and terrestrial mantles have identical W isotope compositions. 

How did a nearly pure sample of Martian atmosphere end up inside BETA 79001 The trapping mechanism was apparently the shock event that ejected the rock from Mars. Simulation experiments, in which (terrestrial) basaltic samples were shocked in the presence of an atmosphere, showed that shock can produce glass that contains a sample of the ambient noble gas, with little or no elemental or isotopic fractionation (Bogard et al. 1986 Wiens and Pepin 1988). Furthermore, the Martian atmospheric signature is emphasized in BETA 79001. The rock is remarkably young (crystallization age of <200 Ma), so there is little radiogenic " °Ar, and has a remarkably short exposure age (<1 Ma), so there is little cosmogenic noble gas of any kind. 

Kuroda PK (1960) Nuclear fission in the early history of the Earth. Nature 187 36-38 Kurz MD (1986) Cosmogenic helium in a terrestrial igneous rock. Nature 320 435-439 Kurz MD, Jenkins WJ, Hart SR (1982) Helium isotopic systematics of oceanic islands and mantle heterogeneity. Nature 297 43-47... 

---