Concerning to the question:
"pyrolysis (Rock-Eval), samples with a %TOC value less than 2% give
questionable results due to matrix effects from clays"
A good alternative method to avoid these problems is described in:
Langford, F.F. and Blanc-Valleron, M.-M., Interpreting Rock-Eval pyrolisis
Data using graphs of Pyrolizable Hydrocarbons vs. Total Organic Carbon.
AAPG Bulletin, v.74, pp. 799-804, June 1990.
I also agreed with Walter E. Dean in forgeting Oxygen Index in those cases!