Molecular features of fossil organic matter in remains of the Lower Cretaceous fern Weichselia reticulata from Przenosza basement (Poland)

Curie-point pyrolysis released a range of aromatic compounds and their alkylated derivatives, i.e. benzenes, phenols, naphthalenes, anthracenes/phenanthrenes, fluorenes and pyrenes (probably derived from heavily altered aromatic biomacromolecules such as lignin or tannins, or from secondary aromatisation of diagenetic structures). There was also a series of n-alkane/n-alkene/α,ω-alkadiene triplets. These range from C9 to C24 in carbon number, which is consistent with the distributions found in previous studies of thermally altered cutan. Methoxyphenols, catechols, fatty acids, steroids, diterpenes and sesquiterpenes were absent or present only in trace amounts. In contrast to the distributions of aliphatic pyrolysis products, the lack of indicators for selectively preserved lignin, carbohydrate or protein, points to an extensive rearrangement of phenolic constituents into a largely newly formed condensed backbone, where the original lignin, waxes and carbohydrate were removed or became incorporated into a condensed kerogen matrix affected by severe reduction, aromatization and additional cross-linking reactions.