Danielle Duzer

Vegetational and climatic significance of modern pollen rain in northwestern Tibet

Abstract In northwestern Tibet, an atmospheric pollen sampling was performed weekly during one year (August 1989 to August 1990). Moreover, 18 dust flux samples were obtained in the same region which covers three geographical units: the western margin of the Taklimakan desert, the northern Karakorum and the northwestern Kunlun mountains. The atmospheric pollen results show that the annual pollen frequency is dominated by regional components of montane and alpine desert and steppe, such as Artemisia, Chenopodiaceae, Cupressaceae and Poaceae. They also show that pollen taxa derived from much more distant sources such as warm temperate and subtropical humid forest zones are sometimes well represented. It is inferred that the majority of airborne pollen has been carried by wind during the flowering seasons of the plants, and this provides an evaluation of the influence of southerly and southwesterly summer monsoon air movements. The similarity of pollen spectra between dust flux samples and the atmospheric pollen trap from the Kunlun Mountains suggests that the pollen deposition evaluated by the dust flux method is representative of the pollen rain in the studied area. The dust samples from lower altitudes are characterized by high values of Chenopodiaceae and low ratios of Artemisia/Chenopodiaceae which vary clearly with altitude and possibly with moisture level. The Artemisia/Ephedra ratio shows similar variations to A/C. The percentage AP value is generally higher in mountains like Kunlun where the plant cover is extremely low in comparison with semiarid massifs such as Karakorum. Therefore, interpretation of AP pollen in the fossil record must take into account long distance wind transport.

A Middle Miocene hominoid from Thailand and orangutan origins

The origin of orangutans has long been debated. Sivapithecus is considered to be the closest ancestor of orangutans because of its facial–palatal similarities, but its dental characteristics and postcranial skeleton do not confirm this phylogenetic position. Here we report a new Middle Miocene hominoid, cf. Lufengpithecus chiangmuanensis n. sp. from northern Thailand. Its dental morphology relates it to the Pongo clade, which includes Lufengpithecus, Sivapithecus, Gigantopithecus, Ankarapithecus and possibly Griphopithecus. Our new species displays striking dental resemblances with living orangutans and appears as a more likely candidate to represent an ancestor of this ape. In addition, it originates from the geographic area of Pleistocene orangutans. But surprisingly, the associated flora shows strong African affinities, demonstrating the existence of a temporary floral and faunal dispersal corridor between southeast Asia and Africa during the Middle Miocene, which may have played a critical role in hominoid dispersion.

15. Estimates of temperature and precipitation variations during the Eemian interglacial: New data from the grande pile record (GP XXI)

New data were obtained from previously unanalysed Grande Pile core samples (GP XXI) corresponding to the penultimate glacial up to the St. Germain 1 interstadial. Parallel sampling for pollen and carbon isotopes was performed. The biostratigraphy is based on pollen grains as proposed by Woillard (1978) for Grande Pile X. The age scale is from Kukla et al. (1997) except for the start of Eemian, which follows the timing defined by Shackleton et al. (2002). The pollen data were first processed to determine their biome scores. The BIOME4 vegetation model was then run in the inverse mode using the determined biome scores and measured δ13C values as constraints to reconstruct the climate parameters. These results are compared with those previously published and show that the Eemian sensu stricto and more generally the penultimate interglacial period was not stable or uniform contrary to previous terrestrial reconstructions but is in agreement with variations observed in the North Atlantic Ocean.