A late Eocene palynological record of climate change and Tibetan Plateau uplift (Xining Basin, China)

Abstract

General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Climate models suggest that Asian paleoenvironments, monsoons and continental aridification were primarily governed by tectonic uplift and sea retreat since the Eocene with potential contribution of global climate changes. However, the cause and timing of these paleoenvironmental changes remain poorly constrained. The recently well-dated continental mudflat to ephemeral saline lake sedimentary succession, situated in the Xining Basin at the northeastern margin of the Tibetan Plateau (NW China), provides a unique opportunity to develop additional proxy successions in this area that are placed accurately in time. Here, a palynological record from this succession is reported. High abundances of desert and steppe-desert taxa such as Ephedripites and Nitrariadites/Nitraripollis are found, which can be differentiated by the presence of broad leaved deciduous forest taxa in the lower part of the section (particularly up to 36.4 Ma; magnetochron C16r), and a sudden increase of Pinaceae (Pinuspollenites, Piceaepollenites and Abiespollenites) which is dated at 36.1 Ma (C16n.2n). Coexistence Approach (CoA) indicates that from 39.9 to 36.4 Ma (C17n.1n) regional climate was warm and wet, while from 36.4 to 33.5 Ma (C16n.2n-C13r) climate tends to be cooler and drier. The data indicate that paleoenvironmental and palynological changes on the NE part of the Tibetan Plateau resulted from a combination of long-term tectonic uplift forcing and long-and short-term climate changes. The increase of taxa such as Piceaepollenites and Abiespollenites indicates not only a cooling and drying trend prior to the Eocene/Oligocene (E/O) boundary, but also the existence of high altitude mountain habitats in the periphery of the Xining Basin. The sudden Pinaceae event correlates closely in time with a marked aridification step as viewed from the lithology of the Xining Basin that was linked to the sea retreat out of the Tarim Basin.

Pollen morphology ofEphedra(Gnetales) and its evolutionary implications

“…Doyle & Le Thomas 1994;Doyle & Endress 2000;Sauquet & Le Thomas 2003), for calibrating molecular dating analyses (Thornhill et al 2012), as well as for studying plant reproductive biology (Ferguson & Skvarla 1982;Grayum 1986;Osborn et al 1991;Bolinder et al 2015). In addition, fossil pollen data are also frequently used for reconstructing past vegetation types and for inferring paleoclimates (Hoorn et al 2012). Ephedroid pollen (i.e.…”

“…Ephedroid pollen (i.e. pollen inferred to have been produced by Ephedra (Gnetales) or Ephedralike extinct plants) is characteristically polyplicate, well known from the fossil record, and considered a good indicator of a very dry paleoclimate (Li et al 2005;Hoorn et al 2012).…”

Observing the past to better understand thefuture: a synthesis of the Neogene climate inEurope and its perspectives on present climatechange

“…Just before the MCO, the Tibetan Plateau reached an elevation capable of generating climate changes, like the beginning of the Indian monsoon and the increase in aridification in the interior of the continent. This effect was felt as far as Eastern Europe [85,86]. However, despite the global cooling during this time, Paratethys and Mediterranean temperatures did not drop significantly [51].…”

Fables and foibles: A critical analysis of the Palaeoflora database and the Coexistence Approach for palaeoclimate reconstruction

“…The combination of MAT, CMT and WMT would be indicative of subtropical climates with hot, rainy summers as found today in central (lowlands) and southern China (lowlands and mid-altitudes). The elimination of the erroneous nearest-living relative (Engelhardia) results in broader and far less precise estimates (see also 'sheet 1' in the electronic supplement to Hoorn et al, 2012, CA analysis labelled "ohne Engel"). Examples of the new reconstruction precision without this single and problematic nearest-living relative include CMT (4-13°C for assemblages with more than ten nearestliving relatives) and MAT intervals (3-11°C in all but one case).…”