what does it mean for something to have a " δ13C signature of −60 ‰ "?
Is that 60 parts of carbon-13 per thousand? why is there a negative sign next to 60? here's the sentence it came from:
" biogenic clathrates have a δ13C signature of −60 ‰ "
thank you.
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The lower case delta (δ) means a difference,
A1(13C) - A2(13C) = δ13C
Where A1 and A2 are two measurements of the amount of 13C present.
A negative value for δ13C means that one of the amounts is greater than the other, and as written in my equation, this would be A2 (A2 > A1, so the difference is a negative number).
"60 parts of carbon-13 per thousand" is correct.
IIRC, this means that clathrates of biogenic origin are depleted in 13C by 6/1000 (0.6%) compared with clathrates of non-biogenic origin.