Astronomical forcing on loess deposition in the Junggar Basin since the late Pliocene

Deciphering dust outbreak frequency in inland Asia during the late Cenozoic is important for predicting the future hydroclimate in the arid parts of China. Here, we present an eolian sedimentary sequence in the southern Junggar Basin over the past 3.5 Ma, Northwestern China. Our data provide a minimum age of 3.5 Ma for the Gurbantunggut Desert of the Junggar Basin. Rb/Sr ratios exhibit prominent 405 kyr eccentricity cycles throughout our record with a weak expression 41 kyr cycles. We interpret this cyclicity as resulting from a strong impact of the global carbon cycle on western China hydroclimate. By contrast, GR data displays significant 100- and 41-kyr cycles after 2.8 Ma, suggesting important dust input variations controlled by westerlies strength. Our results demonstrate that humidity and Westerlies’ strength variations in inland Asia follow different cyclicity during the Quaternary, indicating that moisture supply by westerlies is not directly impacted by wind strength.

解析晚新生代亚洲内陆粉尘爆发频率，对预测中国干旱区未来水文气候具有重要意义。本研究针对中国西北准噶尔盆地南部，构建了过去3.5 Ma以来的风成沉积序列。本研究数据将准噶尔盆地古尔班通古特沙漠的形成下限限定为3.5 Ma。全序列中，铷锶（Rb/Sr）比值呈现显著的405千年偏心率周期，同时伴随较弱的41千年周期信号。我们认为该周期特征源于全球碳循环对中国西部水文气候的强烈影响。与之相反，伽马射线（GR）数据在2.8 Ma之后呈现显著的100千年与41千年周期，指示粉尘输入量的显著变化受西风强度调控。本研究结果表明，第四纪时期亚洲内陆的湿度变化与西风强度变化呈现不同的周期特征，说明西风携带的水汽补给并不直接受风速强度的影响。