Anatomical preservation of silicified Corylites J.S.Gardner leaves from the Paleocene maar lake of Menat (Puy-de-Dôme, France)

The late Paleocene fossil lagerstätte Menat in France is well known for its wealth of excellently preserved fossil plants and insects. Although the flora from this locality is regarded as characteristic for the late Thanetian in Western and Central Europe, there is a noteworthy lack of modern paleobotanical studies on this locality. The few existing studies on plant megafossils utilized only the gross morphology of leaves and carpological material for taxonomic questions, whereas anatomical data (i.e. from cuticles and permineralizations) have been completely neglected. The present study provides the first data on anatomically preserved internal tissues of leaves assigned to Corylites macquarrii (Forbes) Heer from this locality. Cell walls are preserved as silicates, whereas cell lumina are mostly empty. On occasion, cell lumina are filled with foam-like, porous silica. Anatomical preservation of these tissues is probably related to early diagenetic silicification of plant cell walls. Although at the moment nothing can be said about the source of the SiO2 it is likely that it is related to the volcanic origin of the Menat maar and/or volcanic activities in the vicinity of the lake during deposition of the sediments.