--- Robin > I think the explanation for the high concentration can in this case be found in the mundane...
No, no - I should have been clearer - it is not that 'local' concentration which is the precise anomaly in question. But yes there is the mundane explanation for the salt lake also. The 18O/16O ratio in the interstellar region (and presumably the 'normal' ratio found at the time earth cooled) has been measured as 0.18, almost three times lower than the present ratio found in earth's oceans (~.5) and much lower than the total planetary ratio (.3)which includes CO2. (Wilson & Rood 1994). The best explanation for this is that the ratio is altered in a planetary environment by some unknown mechanism vis-a-vis interstellar space.
