Research ArticleGEOLOGY

Pre-Quaternary decoupling between Asian aridification and high dust accumulation rates

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Science Advances  14 Feb 2018:
Vol. 4, no. 2, eaao6977
DOI: 10.1126/sciadv.aao6977
  • Fig. 1 Map of the Chinese Loess Plateau and potential dust source regions, with inset map showing the North Pacific Ocean.

    The main map corresponds to the dashed black rectangle in the inset map. Loess sites mentioned in this study are labeled using white dots, and some source region sample sites were labeled using white squares. The filled white oval and the unfilled red oval correspond to low-elevation eastern Asia (LEEA) and the Qaidam + Gobi (Qilian Shan) source region, respectively. H, Siberian high pressure system; EASM, East Asian summer monsoon; EAWM, East Asian winter monsoon. Revised from Pullen et al. (11). Pink color in main map indicates Cenozoic volcanics.

  • Fig. 2 Chaona Red Clay zircon U-Pb ages and comparison with loess zircon U-Pb ages.

    Black and blue lines are normalized probability density function and kernel density estimation plots, respectively, and open rectangles are age histograms. Pink arrows highlight increases and decreases of the 200- to 300-Ma age population. The shades highlight samples with similar zircon U-Pb age distribution. CN-xMa indicates the depositional age of the Chaona Red Clay samples.

  • Fig. 3 A comparison of North Pacific, Chinese Loess Plateau, and global paleoenvironmental records.

    (A) Dust accumulation rate on the CLP (8). (B) North Pacific dust mass accumulation rate (6). (C) North Pacific dust 206+207+208Pb/204Pb ratio (7). (D) Ratio of number of zircon ages within the 1500- to 2750-Ma range over that within the 400- to 500-Ma range [n(1500–2750Ma)/n(400–500Ma)] on the CLP (this study). (E) Ratio of number of zircon ages within the 200- to 300-Ma range over that within the 400- to 500-Ma range [n(200–300Ma)/n(400–500Ma)] on the CLP (this study). (F) Magnetic susceptibility record on the CLP (1, 8). The lower and upper part of the record is from Qinan (1) and Chaona (8), respectively (see fig. S3 for further justification of using these data). (G) Benthic oxygen isotope record (35). CLP data are all from the Chaona section. The two yellow shades correspond to those in Fig. 2. The average dust accumulation rate of the Chaona section during 8 to 6, 6 to 3.8, and 3.8 to 2.7 Ma is ~24, ~21, and ~28 m My−1, respectively (8).

  • Fig. 4 Biplot of n(200–300Ma)/n(400–500Ma) and n(1500–2750Ma)/n(400–500Ma) from Chaona Red Clay and potential source regions (black dots).

    The ratios for Quaternary loess from the northeastern Jingbian site (brown crosses) and those excluding the Jinbian site on the CLP (brown dots) are also shown for comparison. See table S1 for data references. L3, third loess layer counting from the top of sequence. The tilted black line near the middle of the graph separates high (to the upper right; plus and triangle) from low (to the lower left; dot and square) dust accumulation rate Red Clay samples. The solid and dashed double arrows indicate the schematic mixing pattern for the young loess and for the old loess and Red Clay, respectively.

  • Parameters
    Mass spectrometer
      Cool gas (liter min−1 Ar)13.0
      Auxiliary gas (liter min−1 Ar)0.80
      Sample/make-up gas (liter min−1 Ar)1.06
      Power (W)1200
    Data acquisition
      Masses202Hg, 204Pb, 206Pb, 207Pb,
    208Pb, 232Th, 235U, 238U
      Detection modeIon counting and analog
      ScanningEscan
      Sample time per peak (s)0.0052, 0.0078, 0.0202, 0.0284,
    0.0026, 0.0026, 0.0154, 0.0104
      Number of sample per peak4
      Runs/sweeps per analysis73
      Blank at beginning of each6
      Washout and blank at the end of each (s)11
      Acquisition modeSample blocks
      Acquisition initiationExternal trigger from laser scan
      LaserTeledyne Photon Machines G2
      Type and wavelengthExcimer 193 nm
      Sample cellHelex-fast
      Analyte tubingTeflon
      Laser energy (mJ)7.0 constant energy
      Laser fluence (J cm−2)10.16
      Rep rate (Hz)7
      Preablation pass3 bursts at 20 μm
      Analysis pass110 bursts at 12 μm
      Drill rate (μm/burst)~0.053 (52)
      MFC1, MFC2 (liter min−1 He)0.110, 0.290

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/2/eaao6977/DC1

    fig. S1. Zircon U-Pb age distribution of the potential source regions for the CLP.

    fig. S2. MDS plot of Red Clay/loess and potential source region sample zircon U-Pb geochronology data.

    fig. S3. Magnetic susceptibility record for the CLP (1, 8).

    table S1. Description of samples shown in Fig. 4.

    data file S1. Chaona Red Clay zircon U-Pb geochronologic data.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Zircon U-Pb age distribution of the potential source regions for the CLP.
    • fig. S2. MDS plot of Red Clay/loess and potential source region sample zircon U-Pb geochronology data.
    • fig. S3. Magnetic susceptibility record for the CLP (1, 8).
    • table S1. Description of samples shown in Fig. 4.
    • Legend for data file S1

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    Other Supplementary Material for this manuscript includes the following:

    • data file S1 (Microsoft Excel file). Chaona Red Clay zircon U-Pb geochronologic data.

    Files in this Data Supplement:

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