Vegetation, climate and atmospheric change prior to the Eocene-Oligocene transition : the terrestrial perspective from northern central Europe
Abstrakt
Cenozoic basins in northern central Europe, Germany: Weißelster, Czech Republic: Cheb, Sokolov and North Bohemian, have an extensive megafossil record of Paleogene and Neogene vegetation including across the Eocene-Oligocene transition (EOT) and the late Oligocene warming. Herein we focus gradual changes between the late Bartonian and the EOT.
Based on these distinct plant fossil associations paleoclimatic parameters are reconstructed (CLAMP, Coexistence Approach), and paleoatmospheric pCO2 is estimated using either the Stomata Density approach or the Mechanistic Gas Exchange approach (MGEA). Results show a gradual change in the composition of megafossil associations prior to the EOT.
A massive immigration of broad-leaved deciduous elements prior to the EOT occurs in the North Bohemian Roudníky flora but has not been recognized in the Weißelster Basin. For most of the middle to late Eocene sites a moderate seasonal 'subtropical' to warm temperate climate is reconstructed.
Temperature changes corresponding to the gradual cooling trend in the marine realm could not be quantified due to several reasons. The inverse relationship between stomatal density and pCO2 from a unique stratigraphic sequence of fossil leaves of Eotrigonobalanus furcinervis was used to derive pCO2 records.
Atmospheric pCO2 decreased continuously from the late middle to late Eocene, reaching a relatively stable low value before the end of the Eocene. Similar trends were documented in an overlapping stratigraphic sequence of Platanus neptuni leaves to which the MGEA was applied.
These investigations of floristic changes and changes in paleoatmospheric composition derived from the megafossil plant record reveal similar trends in the middle to late Eocene and may coincide with the global cooling trend postulated from the marine isotope record.