Lateral variations in vegetation in the Himalaya since the Miocene and implications for climate evolution

Vogeli, Natalie and Najman, Yanina Manya Rachel and van der Beek, Peter and Huyghe, Pascale and Wynn, Peter Michael and Govin, Gwladys and van der Veen, Iris and Sachse, Dirk (2017) Lateral variations in vegetation in the Himalaya since the Miocene and implications for climate evolution. Earth and Planetary Science Letters, 471. pp. 1-9. ISSN 0012-821X

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Abstract

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 ∼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 δ13Cδ13C and δ18Oδ18O values of soil carbonate and associated δ13Cδ13C 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. δ13Cδ13C values in soil carbonate show a shift from around −10‰ to −2‰ at ∼7 Ma in the west, which is confirmed by δ13Cδ13C analyses on bulk organic carbon that show a shift from around −23‰ to −19‰ 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, δ13Cδ13C values of bulk organic carbon remain at ∼−23‰∼−23‰ in the east. Thus, our data show that the current east–west variation in climate was established at 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.

Item Type:
Journal Article
Journal or Publication Title:
Earth and Planetary Science Letters
Additional Information:
This is the author’s version of a work that was accepted for publication in Earth and Planetary Science Letters. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Earth and Planetary Science Letters, 471, 2017 DOI: 10.1016/j.epsl.2017.04.037
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/1900/1912
Subjects:
ID Code:
86250
Deposited By:
Deposited On:
13 May 2017 02:35
Refereed?:
Yes
Published?:
Published
Last Modified:
21 Oct 2020 04:45