TY - JOUR A1 - Vogeli, Natalie A1 - Najman, Yani A1 - van der Beek, Peter A1 - Huyghe, Pascale A1 - Wynn, Peter M. A1 - Govin, Gwladys A1 - van der Veen, Iris A1 - Sachse, Dirk T1 - Lateral variations in vegetation in the Himalaya since the Miocene and implications for climate evolution JF - Earth & planetary science letters N2 - The Himalaya has a major influence on global and regional climate, in particular on the Asian monsoon system. The foreland basin of the Himalaya contains a record of tectonics and paleoclimate since the Miocene. Previous work on the evolution of vegetation and climate has focused on the central and western Himalaya, where a shift from C3 to C4 vegetation has been observed at similar to 7 Ma and linked to increased seasonality, but the climatic evolution of the eastern part of the orogen is less well understood. In order to track vegetation as a marker of monsoon intensity and seasonality, we analyzed delta C-13 and 8180 values of soil carbonate and associated delta C-13 values of bulk organic carbon from previously dated sedimentary sections exposing the syn-orogenic detrital Dharamsala and Siwalik Groups in the west, and, for the first time, the Siwalik Group in the east of the Himalayan foreland basin. Sedimentary records span from 20 to 1 Myr in the west (Joginder Nagar, Jawalamukhi, and Haripur Kolar sections) and from 13 to 1 Myr in the east (Kameng section), respectively. The presence of soil carbonate in the west and its absence in the east is a first indication of long-term lateral climatic variation, as soil carbonate requires seasonally arid conditions to develop. delta C-13 values in soil carbonate show a shift from around -10 parts per thousand to -2 parts per thousand at similar to 7 Ma in the west, which is confirmed by delta C-13 analyses on bulk organic carbon that show a shift from around -23 parts per thousand to -19 parts per thousand at the same time. Such a shift in isotopic values is likely to be associated with a change from C3 to C4 vegetation. In contrast, delta C-13 values of bulk organic carbon remain at 23 parts per thousand o in the east. Thus, our data show that the current east -west variation in climate was established at similar to 7 Ma. We propose that the regional change towards a more seasonal climate in the west is linked to a decrease of the influence of the Westerlies, delivering less winter precipitation to the western Himalaya, while the east remained annually humid due to its proximity to the monsoonal moisture source. (C) 2017 Elsevier B.V. All rights reserved. KW - Himalaya KW - stable carbon isotopes KW - paleovegetation KW - Siwalik KW - pre-Siwalik KW - monsoon Y1 - 2017 U6 - https://doi.org/10.1016/j.epsl.2017.04.037 SN - 0012-821X SN - 1385-013X VL - 471 SP - 1 EP - 9 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Xu, QingHai A1 - Cao, Xianyong A1 - Tian, Fang A1 - Zhang, ShengRui A1 - Li, YueCong A1 - Li, ManYue A1 - Li, Jie A1 - Liu, YaoLiang A1 - Liang, Jian T1 - Relative pollen productivities of typical steppe species in northern China and their potential in past vegetation reconstruction JF - Science China N2 - The Relative Pollen Productivities (RPPs) of common steppe species are estimated using Extended R-value (ERV) model based on pollen analysis and vegetation survey of 30 surface soil samples from typical steppe area of northern China. Artemisia, Chenopodiaceae, Poaceae, Cyperaceae, and Asteraceae are the dominant pollen types in pollen assemblages, reflecting the typical steppe communities well. The five dominant pollen types and six common types (Thalictrum, Iridaceae, Potentilla, Ephedra, Brassicaceae, and Ulmus) have strong wind transport abilities; the estimated Relevant Source Area of Pollen (RSAP) is ca. 1000 m when the sediment basin radius is set at 0.5 m. Ulmus, Artemisia, Brassicaceae, Chenopodiaceae, and Thalictrum have relative high RPPs; Poaceae, Cyperaceae, Potentilla, and Ephedra pollen have moderate RPPs; Asteraceae and Iridaceae have low RPPs. The reliability test of RPPs revealed that most of the RPPs are reliable in past vegetation reconstruction. However, the RPPs of Asteraceae and Iridaceae are obviously underestimated, and those of Poaceae, Chenopodiaceae, and Ephedra are either slightly underestimated or slightly overestimated, suggesting that those RPPs should be considered with caution. These RPPs were applied to estimating plant abundances for two fossil pollen spectra (from the Lake Bayanchagan and Lake Haoluku) covering the Holocene in typical steppe area, using the "Regional Estimates of Vegetation Abundance from Large Sites" (REVEALS) model. The RPPs-based vegetation reconstruction revealed that meadow-steppe dominated by Poaceae, Cyperaceae, and Artemisia plants flourished in this area before 6500-5600 cal yr BP, and then was replaced by present typical steppe. KW - typical steppe KW - modern surface pollen KW - relative pollen productivity KW - relevant pollen source area KW - paleovegetation Y1 - 2014 U6 - https://doi.org/10.1007/s11430-013-4738-7 SN - 1674-7313 SN - 1869-1897 VL - 57 IS - 6 SP - 1254 EP - 1266 PB - Science China Press CY - Beijing ER -