Science Bulletin

, Volume 61, Issue 11, pp 897–910

Lake geochemistry reveals marked environmental change in Southwest China during the Mid Miocene Climatic Optimum

  • Julie Lebreton-Anberrée
  • Shihu Li
  • Shu-Feng Li
  • Robert A. Spicer
  • Shi-Tao Zhang
  • Tao Su
  • Chenglong Deng
  • Zhe-Kun Zhou
Article Earth Sciences

Abstract

The Mid-Miocene Climatic Optimum (MMCO; ~15–17 Ma) was one of the short-term climatic warm events that punctuated the Cenozoic long-term cooling trend. Because there are very few terrestrial records of this event, most of our understanding comes from marine cores. In this report, we first present new palaeomagnetic data that revises the dating of our 400 m-thick lacustrine section in Wenshan (Yunnan), previously thought to be Late Miocene. These new data suggest an older age, ca. 15.2–16.5 Ma, coinciding with the MMCO. We measured δ13C on bulk organic matter (δ13Corg), total organic carbon (TOC), total nitrogen (TN) and C/N ratios at a high sample resolution to: (1) reconstruct the palaeoenvironmental changes in the lake catchment area, and (2) infer mechanisms responsible for these changes. Our results show that all four geochemical parameters demonstrate that a strong environmental change occurred around the middle of the section, shortly after the C5Cn/C5Br geomagnetic reversal and the Early/Middle Miocene boundary at 15.97 Ma. We propose that the environmental shift may be due to a combination of a change in climate, which became cooler, together with a change in organic matter cycling within the lake. This study provides a new insight into the MMCO and demonstrates that although the MMCO was generally a warm event, it was also a time of climatic instability and abrupt environmental changes.

Keywords

Yunnan Mid-Miocene Climatic Optimum Bulk organic carbon isotopes (δ13CorgC/N ratio TOC 

中中新世气候适宜期环境变化:来自中国西南部湖泊沉积地球化学的证据

摘要

中中新世气候适宜期(~15–17 Ma)是新生代气候变冷背景下的一次短期气候温暖事件。由于缺乏陆相记录,目前对于该事件的研究多来自于海洋钻孔。本文首先对位于云南东南部的文山湖相地层(厚400米 )开展了高分辨率的古地磁定年,结果显示其年龄为15.2–16.5 Ma,正好位于中中新世气候适宜期内,而不是先前认为的晚中新世。在精确年代框架的基础上,通过高分辨率的全岩块状土样中的有机碳同位素、总有机碳、总氮和碳氮比研究,重建了湖盆的古环境变化,并且探讨了造成这种变化的可能机制。本研究中所测四个的地球化学参数均显示在剖面的中部大约 15.97 Ma时 (稍晚于C5Cn/C5Br地磁倒转或早中新世与晚中新世界限)环境发生了显著变化,可能是气候变冷和湖泊内有机质循环的变化共同造成的。本研究结果表明:尽管中中新世气候适宜期总体表现为气候温暖,而这恰巧是造成环境变化的不稳定气候事件。这一结论也为认识和研究中中新世气候适宜期提供了新的证据和视野。

关键词

云南 中中新世气候适宜期 地球化学 全岩有机碳 碳氮比 总有机碳 

Supplementary material

11434_2016_1095_MOESM1_ESM.doc (760 kb)
Supplementary material 1 (DOC 759 kb)

Copyright information

© Science China Press and Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Julie Lebreton-Anberrée
    • 1
    • 2
  • Shihu Li
    • 3
  • Shu-Feng Li
    • 1
    • 4
  • Robert A. Spicer
    • 5
  • Shi-Tao Zhang
    • 6
  • Tao Su
    • 1
  • Chenglong Deng
    • 3
  • Zhe-Kun Zhou
    • 1
    • 7
  1. 1.Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical GardenChinese Academy of SciencesMenglaChina
  2. 2.University of Chinese Academy of SciencesBeijingChina
  3. 3.State Key Laboratory of Lithospheric Evolution, Institute of Geology and GeophysicsChinese Academy of SciencesBeijingChina
  4. 4.State Key Laboratory of Paleobiology and Stratigraphy, Nanjing Institute of Geology and PaleontologyChinese Academy of SciencesNanjingChina
  5. 5.Environment, Earth and EcosystemsThe Open UniversityMilton KeynesUK
  6. 6.Faculty of Land Resource EngineeringKunming University of Science and TechnologyKunmingChina
  7. 7.Key Laboratory of Biogeography and Biodiversity, Kunming Institute of BotanyChinese Academy of SciencesKunmingChina

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