Uplift, climate and biotic changes at the Eocene–Oligocene transition in south-eastern Tibet

Abstract

The uplift history of south-eastern Tibet is crucial to understanding processes driving the tectonic evolution of the Tibetan Plateau and surrounding areas. Underpinning existing palaeoaltimetric studies has been regional mapping based in large part on biostratigraphy that assumes a Neogene modernization of the highly diverse, but threatened, Asian biota. Here, with new radiometric dating and newly collected plant-fossil archives, we quantify the surface height of part of the south-eastern margin of Tibet in the latest Eocene (∼34 Ma) to be ∼3 km and rising, possibly attaining its present elevation (3.9 km) in the early Oligocene. We also find that the Eocene–Oligocene transition in south-eastern Tibet witnessed leaf-size diminution and a floral composition change from sub-tropical/warm temperate to cool temperate, likely reflective of both uplift and secular climate change, and that, by the latest Eocene, floral modernization on Tibet had already taken place, implying modernization was deeply rooted in the Palaeogene.

East Asian origins of European holly oaks (Quercus section Ilex Loudon) via the Tibet‐Himalaya

“…Two additional leaf specimens (Figure S4 in Appendix S1) belonging to the same taxon were found in MK3 (specimen no. MK3‐2588, and MK3‐1670 kept in XTBG) but not cited in Su et al (); both have the same diagnostic morphology of Quercus section Ilex. As our phylogenetic reconstructions demonstrate the Tibet‐Himalayan populations to be ancestral to the European populations, and as fossils of Quercus section Ilex already occurred in Europe at the Oligocene, we used this fossil as a stem calibration for the European clade (Clade VI), using a lognormal distribution with median 34.6 Ma (95% HPD: 36.54–33.94 Ma).…”

“…One such example is Quercus sp., recently found in the Mangkang basin, East Tibet, ca. 34 Ma (Su, Spicer, et al, ), with a clear affinity to section Ilex . These fossil occurrences demonstrate that section Ilex had established a wide distribution in Eurasia by the Oligocene if not earlier.…”

“…Therefore, we constrained the stem age of section Cyclobalanopsis with median of 48.32 Ma (95% HPD: 48.98 to 47.70 Ma), corresponding to the boundary between the Ypresian and Lutetian. (3) A well preserved oak leaf fossil from MK3 in Markam county, Tibet, dated to 34.6 ± 0.8 Ma (see Figure in Su et al, ), corresponding to the Eocene‐Oligocene boundary was utilized to constrain section Ilex . This fossil exhibits the small, leathery morphology, spine‐toothed margins, and irregularly spaced secondary veins diagnostic of Quercus section Ilex .…”

Extinct genus Lagokarpos reveals a biogeographic connection between Tibet and other regions in the Northern Hemisphere during the Paleogene

“…Fortunately, in recent years numerous fossils have been recovered from the QTP. Paleobotanical studies show that many plant species that once existed on the QTP have disappeared from this region (Xu et al, ; Wu et al, ; Su et al, ; Jiang et al, ; Xu et al, ). This could never be determined by molecular work, but these plant fossils provide us with hard evidence regarding the historical phytogeography of this region (Jia et al, ).…”

High‐Resolution Eocene Magnetostratigraphy of the Xijigou Section: Implications for the Infilling Process of Xining Basin, Northeastern Tibetan Plateau

“…However, there is an increasing availability of terrestrial sedimentary archives of the Eocene. These sites are located on the northeastern margin of the Tibetan Plateau (Bosboom et al, ; Chi et al, ; Dai et al, ; Horton et al, ; Long et al, ; Miao et al, ; Sun et al, ; Yue et al, ), in central China (Bowen et al, ; Ting et al, ; Zhu et al, ), northeastern China (Chen et al, ), southwestern China (Li et al, ; Su et al, ), North and South America (Hyland et al, ; Hyland et al, ; Hyland & Sheldon, ; Koch et al, ; Krause et al, ), and Europe (Egger et al, ). Research on these Eocene sections has focused mainly on chronology and specific climatic events, whereas few studies have drawn stratigraphic comparisons between different sections (Fang et al, ; Smith et al, ).…”