As posted on the list last year, we obtained positive 13C values
(mainly 0 - +10 per mil, one or two at +20 - +30 per mil) from DIC in
oxidised, deep groundwater in the Murray Basin. This rules out
metanogeneis in this case. I'm still not sure of their origin, except
an inverse correlation with 87Sr/86Sr in one area suggests a carbonate
source. My guess is that lacustrine sediments in the aquifer sequences
in the region have high 13C (as in some of the other comments) and the
groundwater has picked up C from these. But that's still a guess...

Ian

______________________________________
Dr Ian Cartwright
Head, School of Geosciences
Groundwater and Stable Isotopes
Monash University
Clayton Vic 3800, Australia

Tel: +61 3 9905-4887 / 4879
Fax: +61 3 9905-4903

...water, our greatest resource

----- Original Message -----
From: Matt Kohn <[log in to unmask]>
Date: Thursday, March 24, 2005 11:51 pm
Subject: [ISOGEOCHEM] Positive extremes for d13C and d18O

> Hi,
>
> An idle question: What are the extreme positive values for
> terrestrial d13C and d18O? I know marine diatom d18O can reach c. +40
> permil, and lacustrine carbonate d13C can reach c. +5 permil. But I
> also know several years ago that someone on the list reported d13C
> values >+10 permil, for lacustrine carbonate (I think: I haven't
> found the published reference yet). Are there higher values, and if
> so in what environments do they occur?
>
> Thanks,
>
> Matt
>
> --
>
>
> **************************************************
> Dr. Matthew J. Kohn, Associate Professor
> Director, Undergraduate studies
> Department of Geological Sciences
> 701 Sumter St., Room EWS 617
> University of South Carolina
> Columbia, SC 29208
> phone: (803)-777-5565   fax:(803)-777-6610
> http://urania.geol.sc.edu/~golab/vita.htm
> articles: http://urania.geol.sc.edu/~golab/GOpdfs.htm
> **************************************************
>