Has anyone out there done work on c-isotope analysis on organic 
carbon in ancient sediments? My question is this; in programmed 
pyrolysis (Rock-Eval), samples with a %TOC value less than 2% give 
questionable results due to matrix effects from clays, has anyone 
found similar problems with c-isotope analysis of decarbonated 
sediment with %TOC values less than 2%, if so have you tried analyses 
on pure kerogen?

Just a quick note to let you all know who I am and what I'm doing:
Bob Brown, first year Ph.D. student at NRG, Newcastle university, 
working with Paul Farrimond and Richard Tyson (NRG), with 
collaborative work with Helmut Weissert (ETH Zurich).
We are looking at the relationship between molecular organic carbon 
and the positive c-isotope curve during oceanic anoxic events in the 
erly cretaceous, during a "greenhouse" environment. Work is focused 
on the Western Tethys region of Europe. Any advice, comments or help 
of any sort is greatly appreciated.

Cheers
Bob.