Geophysical Research Letters

Biomarkers challenge early Miocene loess and inferred Asian desertification

Authors

  • Tingjiang Peng,

    1. Key Laboratory of Western China's Environmental Systems (Ministry of Education) and College of Earth and Environmental Sciences, Lanzhou University, Lanzhou, China
    Search for more papers by this author
  • Jijun Li,

    1. Key Laboratory of Western China's Environmental Systems (Ministry of Education) and College of Earth and Environmental Sciences, Lanzhou University, Lanzhou, China
    2. College of Geography Science, Nanjing Normal University, Nanjing, China
    Search for more papers by this author
  • Chunhui Song,

    1. School of Earth Sciences and Key Laboratory of Western China's Environmental Systems (Ministry of Education), Lanzhou University, Lanzhou, China
    Search for more papers by this author
  • Zhijun Zhao,

    1. College of Geography Science, Nanjing Normal University, Nanjing, China
    Search for more papers by this author
  • Jun Zhang,

    1. Key Laboratory of Western China's Environmental Systems (Ministry of Education) and College of Earth and Environmental Sciences, Lanzhou University, Lanzhou, China
    Search for more papers by this author
  • Zhengchuang Hui,

    1. Key Laboratory of Western China's Environmental Systems (Ministry of Education) and College of Earth and Environmental Sciences, Lanzhou University, Lanzhou, China
    Search for more papers by this author
  • John W. King

    1. Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island, USA
    Search for more papers by this author

Abstract

[1] Fine-grained Miocene sediments from Tianshui Basin, northeastern Tibetan Plateau, have received intense attention recently because these sediments were identified as loess. The presence of early Miocene loess pushes the timing of initiation of inland Asian desertification from 8 Ma back to 22 Ma. However, mudflat/distal fan and shallow lake sediments of Miocene have also been reported in Tianshui Basin. Consequently, the origin of these fine-grained Miocene sediments in this area remains controversial. Here we investigate then-alkane biomarker characteristics of Neogene sediments from a north-south transect of exposures within Tianshui Basin and compare these molecular distributions with those published Quaternary loess to help resolve the disputed origin. We found thatn-C23 and n-C25 alkanes, sourced from either aquatic macrophytes or palustrine plants, are ubiquitous in the Miocene sediments from Tianshui Basin but are largely absent in Quaternary loess. This striking difference between n-alkane distributions in the Tianshui samples and the Quaternary loess casts doubt on an eolian origin for the Tianshui samples and challenges the hypothesis of an early Miocene onset of Asian interior desertification.

Ancillary