CONIFEROUS WOODS IN THE EARLY PLEISTOCENE BROWN COALS OF THE LEFFE BASIN (LOMBARDY, ITALY). Ecological and biostratigraphic inferences

49 autochthonous wood samples collected in brown coal from the Leffe palustrine deposits (Early Pleistocene, Lombardy, N-Italy) have been identified and their stratigraphical position has been discussed in comparison with pollen spectra. A peat level in the lower part of the succession contains Piceoxylon wood. Pollen spectra point to a conifer forest of dry and cool climate. Glyptostroboxylon  tenerum,  Chamaecyparis, Pinus aff. tabulaeformis, Carya, Pterocarya, Alnus, Fraxinus and Celtis woods have been identified from the "Main" brown coal layer in the middle (biogenic) unit of the Leffe Formation. The coniferous woods are described and some inferences about their ecological requirements are presented. These trees formed part of the swamp vegetation during interglacial phases. Pinus occurred, only during meso/oligotrophic phases. The biostratigraphic interest of these finds and climate dynamics are discussed, in order to interpret the discontinuous record of the "Tertiary plants" in Northern Italy during lowermost Pleistocene

Chemotaxonomy of fossil woods from the Lower Rhine Embayment, Germany

In the Lower Rhine Embayment (western Germany), the Neogene lignite bearing sequence is rich in large fossil wood trunks. Woods collected from sand-filled channels of a meandering river system (Pliocene: Reuver series) and from coal seams (Miocene: seams Garzweiler, Frimmersdorf and Morken) were investigated by Curie-point pyrolysis coupled with gas chromatography–mass spectrometry in order to determine their palaeobotanical classification. In comparison with reference data of individual pyrograms of modern woods, it became possible to classify 15 fossil wood trunks chemotaxonomically as follows: eleven samples were identified as Taxodioxylon sp. by reference Sequoia sempervirens, three samples were identified as Populoxylon sp. by reference Populus nigra and one sample was identified as Sciadopityoxylon sp. by two references of Sciadopitys verticillata. Microanatomical crosschecks describe the equivalent samples taxonomically as Taxodioxylon gypsaceum (GÖPPERT) KRÄUSEL, Taxodioxylon germanicum (GREGUSS) VAN DER BURGH, Populus nigra L. and Sciadopityoxylon wettsteinii JURASKY, and confirm the chemical classifications. For both fossil and reference woods, our relative quantifications of guaicyl and syringyl moieties are in precise accordance with discriminations of gymnosperms versus angiosperms. This means that not only unknown recent woods can chemotaxonomically accurately be determined by Curie-point pyrolysis gas chromatography–mass spectrometry and their equivalent modern wood reference from our data base, but also the taxonomy of botanically related wood types reaching back to the geological past up to a Miocene age at least

Chemotaxonomy of fossil woods from the Lower Rhine Embayment, Germany

In the Lower Rhine Embayment (western Germany), the Neogene lignite bearing sequence is rich in large fossil wood trunks. Woods collected from sand-filled channels of a meandering river system (Pliocene: Reuver series) and from coal seams (Miocene: seams Garzweiler, Frimmersdorf and Morken) were investigated by Curie-point pyrolysis coupled with gas chromatography–mass spectrometry in order to determine their palaeobotanical classification. In comparison with reference data of individual pyrograms of modern woods, it became possible to classify 15 fossil wood trunks chemotaxonomically as follows: eleven samples were identified as Taxodioxylon sp. by reference Sequoia sempervirens, three samples were identified as Populoxylon sp. by reference Populus nigra and one sample was identified as Sciadopityoxylon sp. by two references of Sciadopitys verticillata. Microanatomical crosschecks describe the equivalent samples taxonomically as Taxodioxylon gypsaceum (GÖPPERT) KRÄUSEL, Taxodioxylon germanicum (GREGUSS) VAN DER BURGH, Populus nigra L. and Sciadopityoxylon wettsteinii JURASKY, and confirm the chemical classifications. For both fossil and reference woods, our relative quantifications of guaicyl and syringyl moieties are in precise accordance with discriminations of gymnosperms versus angiosperms. This means that not only unknown recent woods can chemotaxonomically accurately be determined by Curie-point pyrolysis gas chromatography–mass spectrometry and their equivalent modern wood reference from our data base, but also the taxonomy of botanically related wood types reaching back to the geological past up to a Miocene age at least

Freshwater fern Azolla in and around Arctic and Nordic seas

For a short time interval (c. 1.2 Myr) during the early middle Eocene (~49 Myr), the central Arctic Ocean was episodically densely covered by the freshwater fern Azolla, implying sustained freshening of surface waters. Coeval Azolla fossils in neighboring Nordic seas were thought to have been sourced from the Arctic. The recognition of a different Azolla species in the North Sea raised doubts about this hypothesis. Here we show that no less than five Azolla species had coeval blooms and spread in the Arctic and NW European regions. A likely trigger for these unexpected Azolla blooms is high precipitation prevailing by the end of the warmest climates of the Early Eocene Climatic Optimum (EECO)

Letter. Episodic fresh surface waters in the Eocene Arctic Ocean

It has been suggested, on the basis of modern hydrology and fully coupled palaeoclimate simulations, that the warm greenhouse conditions that characterized the early Palaeogene period (55–45 Myr ago) probably induced an intensified hydrological cycle with precipitation exceeding evaporation at high latitudes. Little field evidence, however, has been available to constrain oceanic conditions in the Arctic during this period. Here we analyse Palaeogene sediments obtained during the Arctic Coring Expedition, showing that large quantities of the free-floating fern Azolla grew and reproduced in the Arctic Ocean by the onset of the middle Eocene epoch (50 Myr ago). The Azolla and accompanying abundant freshwater organic and siliceous microfossils indicate an episodic freshening of Arctic surface waters during an 800,000-year interval. The abundant remains of Azolla that characterize basal middle Eocene marine deposits of all Nordic seas probably represent transported assemblages resulting from freshwater spills from the Arctic Ocean that reached as far south as the North Sea. The termination of the Azolla phase in the Arctic coincides with a local sea surface temperature rise from 10°C to 13°C, pointing to simultaneous increases in salt and heat supply owing to the influx of waters from adjacent oceans. We suggest that onset and termination of the Azolla phase depended on the degree of oceanic exchange between Arctic Ocean and adjacent seas

Toward a Cenozoic history of atmospheric CO2

The geological record encodes the relationship between climate and atmospheric carbon dioxide (CO2) over long and short timescales, as well as potential drivers of evolutionary transitions. However, reconstructing CO2 beyond direct measurements requires the use of paleoproxies and herein lies the challenge, as proxies differ in their assumptions, degree of understanding, and even reconstructed values. In this study, we critically evaluated, categorized, and integrated available proxies to create a high-fidelity and transparently constructed atmospheric CO2 record spanning the past 66 million years. This newly constructed record provides clearer evidence for higher Earth system sensitivity in the past and for the role of CO2 thresholds in biological and cryosphere evolution