Palaeobotanical Approach Research Articles

Systematic relationships of the Mesozoic wood genus Xenoxylon: an integrative biomolecular and palaeobotanical approach

Xenoxylon GOTHAN is one of the very few components of Mesozoic terrestrial biota which give clear palaeoecological signal. Unfortunately its systematic relationships are still unknown. This work analyzes the organic geochemistry of particularly well preserved samples of Xenoxylon from the Callovian of ⁄ Lukow (eastern Poland) for comparison with the Bathonian of Gnaszyn (southcentral Poland). The wood fragments from both ⁄ Lukow and Gnaszyn contain phenolic abietanes like ferruginol, 6,7-dehydroferruginol, sugiol, hinokiol or 2-ketototarol. The presence of such biomolecules, with simultaneous absence or very small amount of tetracyclic diterpanes such as phyllocladanes, beyerane and/or kauranes, is characteristic for extant conifer families Cupressaceae s. l. and Podocarpaceae. Thus, the molecular composition of the wood genus Xenoxylon suggests systematic relationships with these extant families. This study presents the evidence that preserved biomarkers and biomolecules are not exceptional in fossil wood, and that their composition generally supports the anatomical data.

Holocene palaeoenvironmental changes in southern France: a palaeobotanical study of travertine at St-Antonin, Bouches-du-Rhône

Travertines are carbonate deposits formed generally during temperate climatic periods. They usually present a succession of travertinous units and detrital sedimentary levels containing leaf impressions and charcoal, respectively. The travertine of St-Antonin was formed during the Holocence in accordance with this model; snail shells and archaeological material have also been preserved, essentially in detrital levels. An interdisciplinary investigation combining two palaeobotanical approaches (identification of leaf imprints and charred wood) has been carried out to identify vegetation changes, at a local or microregional scale during the travertine formation. Our results were compared with those of previous malacological, geomorphological and archaeological studies. The Preboreal and Boreal sequence of the travertine shows evidence of a reduction of the riverside vegetation correlated with the establishment of a mesophilous vegetation dominated by the pubescent oak (Quercus pubescens). During the Boreal–Atlantic transition, the vegetation structure changed slightly under anthropogenic influence. From the Atlantic to the first part of the Subboreal, vegetation seems to have been profoundly affected by intensive human exploitation. This process has broken up the forested area into different plant communities and favoured the dominance of heliophilous and thermophilous species.