Northward expansion of the southern-temperate podocarp forest during the early Eocene

Palynological evidence from the NE Tibetan Plateau (China)

verfasst von

Faez Robin-Champigneul, Julia Gravendyck, Huasheng Huang, Amber Woutersen, David Pocknall, Niels Meijer, G. Dupont-Nivet, Roy H.J. Erkens, C. Hoorn

Abstract

The debated vegetation response to climate change can be investigated through palynological fossil records from past extreme climate conditions. In this context, the early Eocene (53.3 to 41.2 million years ago (Ma)) is often referred to as a model for a greenhouse Earth. In the Xining Basin, situated on the North-eastern Tibetan Plateau (NETP), this time interval is represented by an extensive and well-dated sedimentary sequence of evaporites and red mudstones. Here we focus on the palynological record of the Early Eocene Climatic Optimum (EECO; 53.3 to 49.1 Ma) and study the fossil gymnosperm pollen composition in these sediments. In addition, we also investigate the nearest living relatives (NLR) or botanical affinity of these genera and the paleobiogeographic implications of their occurrence in the Eocene of the NETP. To reach our objective, we complemented transmitted light microscopy with laser scanning- and electron microscopy techniques, to produce high-resolution images, and illustrate the morphological variation within fossil and extant gymnosperm pollen. Furthermore, a morphometric analysis was carried out to investigate the infra- and intrageneric variation of these and related taxa. To place the data in context we produced paleobiogeographic maps for Phyllocladidites and for other Podocarpaceae, based on data from a global fossil pollen data base, and compare these with modern records from GBIF. We also assessed the climatic envelope of the NLR. Our analyses confirm the presence of Phyllocladidites (NLR Phyllocladus, Podocarpaceae) and Podocarpidites (NLR Podocarpus, Podocarpaceae) in the EECO deposits in the Xining Basin. In addition, a comparative study based on literature suggests that Parcisporites is likely a younger synonym of Phyllocladidites. Our findings further suggest that the Phyllocladidites specimens are derived from a lineage that was much more diverse than previously thought, and which had a much larger biogeographical distribution during the EECO than at present. Based on the climatic envelope of the NLR, we suggest that the paleoclimatic conditions in the Xining Basin were warmer and more humid during the EECO. We conclude that phylloclade-type conifers typical of the southern-temperate podocarp forests, had a northward geographical expansion during the EECO, followed by extirpation.

Organisationseinheit(en)

Institut für Geologie

Externe Organisation(en)

Maastricht University
Rheinische Friedrich-Wilhelms-Universität Bonn
Università degli Studi di Firenze (UniFi)
LOEWE Biodiversity and Climate Research Centre
Centre national de la recherche scientifique (CNRS)
Universiteit van Amsterdam (UvA)
Naturalis Biodiversity Center

Typ

Artikel

Journal

Review of Palaeobotany and Palynology

Band

316

ISSN

0034-6667

Publikationsdatum

09.2023

Publikationsstatus

Veröffentlicht

Peer-reviewed

Ja

ASJC Scopus Sachgebiete

Ökologie, Evolution, Verhaltenswissenschaften und Systematik, Paläontologie

Ziele für nachhaltige Entwicklung

SDG 13 – Klimaschutzmaßnahmen

Elektronische Version(en)

https://doi.org/10.1016/j.revpalbo.2023.104914 (Zugang: Offen)