Paleoclimatic evolution of Holocene loess and discussion of the sensitivity of magnetic susceptibility and median diameter
Paleoclimatic evolution of Holocene loess and discussion of the sensitivity of magnetic susceptibility and median diameter
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DOI：
10.1016/j.quaint.2012.06.015
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发表时间：
2013-05
影响因子：
2.2
通讯作者：
Guoyong Zhao;Xiu-ming Liu;Qu Chen;Bin Lü;H. Niu;Zhi Liu;Pingyuan Li
中科院分区：
文献类型：
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作者：
Guoyong Zhao;Xiu-ming Liu;Qu Chen;Bin Lü;H. Niu;Zhi Liu;Pingyuan Li
气候变化与人们的生计密切相关。因此，全新世气候变化对人类尤为重要。我国风成黄土沉积是古气候变化的最佳地质记录之一。全新世黄土是黄土序列的最上层，易受人类活动的扰动。由于这个原因，它没有得到彻底的研究。位于黄土高原西北缘的甘肃省会宁县百草园地区，新近发现了一个连续沉积、高分辨率、保存完好的全新世黄土剖面。剖面的磁性和粒度信号反映了全新世的古气候变化，并与三宝洞和葫芦洞石笋氧同位素记录具有可比性。它们一致地记录了东亚全新世古气候演化的总体过程。14.2- 12.8kaBP，末次盛冰期进入全新世过渡期。12.8- 11.5kaBP，气候寒冷干燥，以新仙女木期为主。11.5 ~ 10.5kaBP，气候迅速转暖湿润，10.5- 5.2kaBP为全新世最佳期，其间可观察到一些相对干冷的事件。自5.2kaBP以来，气候逐渐变干变冷。从全新世早期到晚全新世，气候总体上呈现出干燥化的趋势，这种变化受太阳辐射变化的控制。与磁化率相比，中位直径曲线波动频繁。中位直径曲线记录了一些气候事件，而磁化率曲线则没有记录到。白草园剖面全新世沉积物粒度参数对古气候变化的敏感性大于磁化率。
Climate changes are closely related to peoples' livelihoods. Holocene climate changes are therefore particularly important to humans. It is known that eolian loess deposits in China are one of the best geological records for paleoclimatic change. As it is the top layer of loess sequence, Holocene loess may be easily disturbed by human activities. For that reason, it has not been studied thoroughly. Recently, a continuously deposited, high-resolution and well-preserved Holocene loess section has been found in Baicaoyuan, Huining County, Gansu Province, located in the northwest edge of the Chinese Loess Plateau. The magnetic and grain size signals of the section reflect Holocene paleoclimate variations and are comparable to the stalagmite oxygen isotope records of Sanbao and Hulu caves. They consistently record the general evolution process of Holocene paleoclimate in Eastern Asia. During the period 14.2–12.8 ka BP, Last Glacial Maximum turned into Holocene transition phase. During 12.8–11.5 ka BP, the climate was cold and dry, dominated by the Younger Dryas. Between 11.5 and 10.5 ka BP, the climate rapidly turned warm and wet, and 10.5–5.2 ka BP was the Holocene Optimum Period, during which some relatively dry-cold events could be observed. Since 5.2 ka BP, the climate slowly became dry and cold. In summary, the climate showed a general drying trend from the early Holocene to the late Holocene, which was controlled by variation of solar radiation. Compared with magnetic susceptibility, the median diameter curve fluctuates frequently. Some climate events were recorded by the median diameter curve, but not observed in the magnetic susceptibility curve. It is suggested that the grain size parameter is more sensitive to paleoclimate changes than susceptibility at the Baicaoyuan section during the Holocene.