甘肃西峰赵家川黄土-红粘土剖面坡缕石分布及其古气候意义

Distribution of Palygorskite in the Zhaojiachuan Section of Chinese Loess Plateau and Its Paleoclimate Significance

自生坡缕石的形成可以指示着干旱、高蒸发量的环境。利用场发射扫描电镜(FE-SEM)和X射线衍射分析(XRD)对甘肃西峰赵家川红粘土剖面样品进行了系统研究。结果表明,坡缕石从2.04Ma开始广泛分布于整个红粘土剖面。坡缕石晶体在红粘土矿物碎屑中呈束状交织形态,其与周围矿物的接触关系说明是从古土壤溶液中直接结晶沉淀出来,因此是自生成因。赵家川剖面中坡缕石记录的信息与青藏高原隆升有着时代的耦合性,也与亚洲内陆干旱化有着密切的联系,佐证了青藏高原隆升对东亚季风的控制和风成堆积的重要控制,验证晚上新世黄土高原干旱化气候的开始,更新世干旱化进一步加剧。因此,坡缕石可以作为黄土高原干旱化气候的矿物学新指标。

Palygorskite is an important environmental and climate change indicator mineral. The formation of autogenic palygorskite may indicate a dry, high-evaporation environment. Using field emission scanning electron microscopy （FE-SEM） and X-ray diffraction （XRD）, we investigated the palygorskite content and palygorskite distribution in the Zhaojiachuan section, Xifeng, Gansu province. The results showed that palygorskite began to appear at 2.04 Ma. It has a wide distribution in the entire red clay section. The fibrous palygorskite crystallizes at the edges of clay mineral particles and the platy clay mineral particles are gradually replaced by fibrous palygorskite crystals, which indicates an autogenic origin of palygorskite. We propose that the palygorskite changes are correlated with the uplift of the Qinghai-Tibet Plateau during the Late Miocene and coupled with the development of the Asian inland drought. It evidenced the important control of the Qinghai-Tibet Plateau uplift over the East Asian monsoon and the eolian deposits. It also verified that the climate began to be arid at the Late Pliocene, and the drought was intensified at the Pleistocene.