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Loess deposits in southern Tajikistan (Central Asia): Magnetic properties and paleoclimate
Quaternary Geochronology ( IF 2.7 ) Pub Date : 2020-08-19 , DOI: 10.1016/j.quageo.2020.101114
Nazarov Parviz , Zhongshan Shen , Mamadjanov Yunus , Sajid Zulqarnain

The continental accumulation of dust during the Quaternary led to the formation of widespread loess deposits in southern Tajikistan. In this area, the accumulation of loess is commonly associated with the occurrence of dust storms and the widespread distribution of loess provides evidence of dust storms becoming more frequent in arid Central Asia at least since the Early Pleistocene. Southern Tajikistan represents one of the largest loess deposits in Central Asia. We conducted a thorough study on the magnetostratigraphy, grain size, and magnetic susceptibility of the Chashmanigar section to reconstruct the stratigraphy of loess deposits and paleoclimate of Tajikistan. Based on our new data, the lower boundary of the basal ages of the Olduvai and Reunion subchrons were established for the studied Chashmanigar section. Rock magnetic analyses showed that the predominant ferrimagnetic minerals are large pseudo-single domain grains of magnetite, including limited maghemite. Standard demagnetization techniques yielded a characteristic component of natural remanent magnetization, which was used to obtain a well-defined magnetostratigraphy. In southern Tajikistan, paleosols consistently exhibit finer grain size distribution and higher magnetic susceptibility than loess horizons, suggesting that the environment of the Chashmanigar section was colder, drier, and dustier during glacial periods than during interglacial periods. Through correlation with astronomically tuned oxygen isotope records, sophisticated dating of the loess-paleosol sequence at Chashmanigar could be achieved, and the global significance of the recorded paleoclimatic variations could be revealed. The resulting grain size, magnetic susceptibility, and correlation with astronomically tuned oxygen isotope clearly provide information about the climatic pattern during the Early Pleistocene.



中文翻译:

塔吉克斯坦南部(中亚)的黄土矿床:磁性和古气候

第四纪期间大陆的尘埃堆积导致塔吉克斯坦南部形成了广泛的黄土沉积物。在该地区,黄土的积累通常与沙尘暴的发生有关,并且黄土的广泛分布提供了至少自更新世以来沙尘暴在干旱中亚变得更加频繁的证据。塔吉克斯坦南部是中亚最大的黄土矿床之一。我们对查什曼尼加尔剖面的地层,地层大小和磁化率进行了深入研究,以重建塔吉克斯坦的黄土和古气候地层。根据我们的新数据,为研究的Chashmanigar断层建立了Olduvai和Reunion次子基础年龄的下限。岩石磁性分析表明,主要的亚铁磁性矿物是磁铁矿的准伪单畴大晶粒,包括有限的磁赤铁矿。标准的消磁技术产生了自然剩磁的特征成分,该成分用于获得清晰的地层。在塔吉克斯坦南部,古土壤始终比黄土层具有更细的粒度分布和更高的磁化率,这表明与冰川期相比,Chashmanigar段的环境在冰川期更冷,更干燥,更尘土飞扬。通过与天文调整的氧同位素记录的相关性,可以实现查什曼尼加尔黄土-古土壤序列的精密年代测定,并且可以揭示所记录古气候变化的全球意义。

更新日期:2020-08-19
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