Abstract:
Organic geochemical methods for conodont analysis have been developed. Coniform elements of the conodont genus
Drepanodus from the Ordovician Emanuel Formation and pectiniform elements of the conodont genus Polygnathus
from the Devonian Napier Formation both from the Canning Basin, Australia have been shown to contain different
organic matter. Both conodont samples have been artificially matured and the structure of organic matter present
related to the conodont alteration index (CAl) and maturation temperature (TM). The carbon Is X-ray photoelectron
spectra (XPS) acquired from both sample sets contain six peaks. These peaks are assigned to highly ordered graphitic
like carbon (282.9 eV), sp3 hybridised carbon bonded to only carbon or hydrogen (284.7 eV), ether (286.1 eV), alcohol
(287.0 eV), carbonyl (287.6 eV) and carboxyl (289.0 eV) functional groups. Alkene and aromatic carbon is also probably
present but is difficult to delineate. During artificial maturation, XPS analysis monitors the main chemical modifications
expressed by the carbon-oxygen functional groups. The first stage of maturation begins with the removal of carboxyl and
alcohol groups before a CAl of 2 (TM 450 QC).Between a CAl of 3-6 (TM 450-800 QC)an increase of Sp3 hybridised
carbon bonded to only carbon or hydrogen is found, which is accompanied by a decrease in ether and carbonyl functional
groups. From a CAl of 6-7 (TM 800-950 QC),Sp3 hybridised carbon bonded to hydrogen or carbon and carbonyl
decreases while the development of highly ordered graphitic like carbon is observed. The first order laser Raman
spectra recorded for both sample sets show a low degree of structural order from a CAl of 2-3, and from CAl 4-6
show a progressive increase in structural disorder of conodont organic matter. The DIG band (band at approximately
1345-1365/band at 1610 cm-¹) line width ratio correlates with CAL Conodont colour during artificial maturation
occurs by migration of compounds to the surface. As the nitrogen compounds are volatilised from the surface, colour
disappears.
