Structure of organic matter in conodonts with different colour alteration indexes

Devonian conodont samples from the Beechwood Member of the North Vernon Lim estone, IN, USA and Garra Formation Wellington, NSW, Australia with Colour Alteration Index (CAI) values of 2 and 4, respectively, were analysed using X-ray photoelectron spectroscopy (XPS), pyrolysis gas chromatography mass spectrometry (py-GC/MS) and Fourier transform infrared emission spectroscop y (FTIRES). The results show the organic matter is different for the two co nodont samples, but contrary to that predicted if only thermal processes we re operating. The organic matter in the Beechwood Member conodonts appears to be reduced whereas conodonts from the Garra Formation appear to be oxidi sed. Pyrolysates from organic matter in the Beechwood Member conodonts are dominated by an n-alkane series of hydrocarbons from C-8 to C-19, and simpl e aromatic hydrocarbons, however pyrolysates of organic matter from conodon ts in the Garra Formation are dominated by nitrogen compounds and ketones. It is concluded that CAI values should be checked spectroscopically since C AI values indicating oil potential will be misleading if the organic matter is oxidised. (C) 1999 Elsevier Science Ltd. All rights reserved.