Uplift-driven sediment redness decrease at ~16.5 Ma in the Yumen Basin along the northeastern Tibetan Plateau.

Weitao Wang,Jingxing Yu,Hongyan Xu,Jianzhang Pang,Peizhen Zhang,Caicai Liu,Dewen Zheng,Huiping Zhang,Wenjun Zheng

doi:10.1038/srep29568

Weitao Wang, Jingxing Yu + Show 7 more

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https://doi.org/10.1038/srep29568

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Abstract

Significant climate shifts in the northeastern Tibetan Plateau have taken place during the Cenozoic, but the reasons behind them remain unclear. In order to unravel the mechanisms driving these climate changes, proxy data with accurate age constraint are needed. Here we present magnetostratigraphy, sediment color (redness a*, and lightness L*) and grain-size analysis from an early to middle Miocene (~20–15.3 Ma) sediment sequence preserved in the Yumen Basin on the northeastern Tibetan Plateau. In this basin, remarkable increase in lightness, decreases in redness and in ratio of hematite (Hm) to goethite (Gt) took place at ~16.5 Ma. We suggest that these changes result from shorter duration of weathering, climatic wetting, and cooling associated with rapid uplift of the Qilian Shan at the middle Miocene.

Highlights

The climate at the northeastern margin of the Tibetan Plateau changed significantly during the Cenozoic era[1,2,3,4]
A clear understanding of Eastern and Central Asian climate history and forcing mechanisms relies on the availability of well-dated Cenozoic climatic records in the northeastern Tibetan Plateau, where continuous basin deposits are sensitive to regional uplift
The depositional ages of the upper part of the Baiyanghe Formation and the lower part of the Shulehe Formation from the CG section are constrained by published magnetostratigraphy results[16]

Summary

Introduction

The climate at the northeastern margin of the Tibetan Plateau changed significantly during the Cenozoic era[1,2,3,4]. A clear understanding of Eastern and Central Asian climate history and forcing mechanisms relies on the availability of well-dated Cenozoic climatic records in the northeastern Tibetan Plateau, where continuous basin deposits are sensitive to regional uplift. Soil color studies of loess-paleosol sequences from the Chinese Loess Plateau have been completed[12,13,14] These data sets provide an excellent reference for paleoenvironmental reconstructions in the region. Detailed studies of sediment color records from Miocene deposits in the northeastern Tibetan Plateau are rare, and their potential as a paleoclimate proxy require further study. Sediment redness decreased sharply at ~16.5 Ma, indicating a significant decrease of hematite production We attribute this change to fast sediment transport, climatic cooling and wetting associated with rapid uplift of the Qilian Mountains. Fluvial and lacustrine deposits dominate the Yumen basin fill, which has been divided into five stratigraphic units (in upward sequence): the Huoshaogou, Baiyanghe and Shulehe Formations and the Yumen and Jiuquan conglomerates[17]

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