At the foot of the Eiffel Tower: The fossil flora of Passy (early Eocene), new discoveries, and challenges.
Résumé
The fossils from Passy, in Île-de-France, correspond to a temporary excavation during the construction of a building in 1999. This construction revealed layers of lignite sediments belonging to the “sables d’Auteuil” (middle Ypresian). Only two species of Icacinaceae from this site have been published to date. The purpose of this study is to comprehensively examine the plant megafossils from this site and infer the paleoecology and the biogeographic history of this flora. Although limited to a few bags of sediment, the site reveals 144 fruits, seeds and cones specimens that are suitable for morphological study. They have been photographed and compared with existing literature in Eocene of Northern Hemisphere. All specimens were classified into ca. 50 morphotypes. The difficulty in studying Passy arises from the fact that fossil fruits, seeds and cones are generally extremely compressed, making their identification at the family or genus level sometimes challenging. The internal anatomy is generally crushed, and size measurements are affected, making direct comparisons with other fossil sites difficult. Nevertheless, some of the specimens are easily identifiable. Angiosperm remains dominate in abundance and specific diversity, accounting for approximately 90% of the total. In particular, the site has an abundance of fruits and seeds corresponding to lianescent groups such as Vitaceae, Menispermaceae, and Icacinaceae, as well as generally tropical groups such as Arecaceae, Anacardiaceae, and Apocynaceae. Conifers are represented by isolated cone parts or scales from possibly Taxodiaceae and Pinaceae. The composition of this assemblage demonstrates the existence of a tropical to subtropical climate during the early Eocene in Paris. This flora likely evolved in a swampy area and formed dense, humid forests. The potential allochthonous conifer remains could indicate a continental flora with a cooler to subtropical appearance. These results agree with previous palynological finding at the Paris Basin scale.