Late Pleistocene dust dynamics and pedogenesis in Southern Eurasia - Detailed insights from the loess profile Toshan (NE Iran)
Late Pleistocene dust dynamics and pedogenesis in Southern Eurasia - Detailed insights from the loess profile Toshan (NE Iran)
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DOI：
10.1016/j.quascirev.2017.11.010
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发表时间：
2018-01
影响因子：
4
通讯作者：
Stefan Vlaminck;M. Kehl;C. Rolf;S. Franz;T. Lauer;E. Lehndorff;M. Frechen;F. Khormali
中科院分区：
文献类型：
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作者：
Stefan Vlaminck;M. Kehl;C. Rolf;S. Franz;T. Lauer;E. Lehndorff;M. Frechen;F. Khormali
在欧亚大陆南部，干旱化、尘源扩展和增强的风成沉积作用的周期性阶段与潮湿的间隔交替出现，在晚更新世气候变化的背景下，促进了通缩区的减少和灰尘的积累。因此，在这个更大的区域的风化和土壤形成的强度，主要取决于粉尘供应和水分供应之间的平衡的波动，在迄今已知的部分，托山黄土-土壤序列（LPS）是一个关键的网站，由于记录的质量和大量的可用数据提供详细的洞察到该地区的粉尘积累和土壤形成的时间和幅度。为了阐明过去13万年大部分时间的这种动力学，本文提供了大量的矿物学和地球化学资料，并辅以高分辨率的磁化率记录和对托山黄土的详细微形态研究结果，末次间冰期淋溶土/类黑土（RIMIS 5e）和早冰期间冰期干草原古土壤（CIMIS 5 c和a）的特征是粒度逐渐增大，云母和镁铁质矿物的分解程度逐渐降低。明显的长石风化只在末次间冰期和现代土壤中被检测到，它们分别在倒数第二次和末次冰期黄土上减少或不存在灰尘沉积的情况下形成（沉积后）。整体pedoseptidial条件对应于大规模的趋势，增加干旱，灰尘积累和风力在欧亚大陆南部的关系，减少水分供应对早期Pleniglacial（PIMIS 4），造成土壤形成下正在进行的灰尘沉积（同沉积）。类似的同沉积土壤形成的时间间隔记录在间冰期/interstadial-stadial过渡的早期冰期和pleniglacial（AMMIS 4至2）interstadial。后者的特点是磁化率、颜色和纹理逐渐增加。相反，硅酸盐风化不能被检测到，这表明粒度波动是一个主要特征。因此，在欧亚大陆南部的多风和干旱pleniglacial条件中断同沉积土壤形成的间歇性阶段，响应短暂和相对潮湿的interstadials。虽然这些初始土壤的相互关系，整个欧亚大陆南部受到相当大的限制，托山LPS的振荡模式承担了很大的相似性与千年尺度的振荡记录在西亚的湖沼档案。
In southern Eurasia recurrent phases of aridization, dust source extension and enhanced Aeolian sedimentation alternated with moister intervals, promoting reduced deflation areas and dust accumulation in the context of late Pleistocene climate changes. Weathering and soil forming intensity in this greater region are, hence, mainly governed by fluctuations in the balance between dust supply and moisture availability.Among the hitherto known sections, the Toshan loess-soil sequence (LPS) represents a key site due to the quality of the record and the multitude of available data giving detailed insights into the timing and magnitude of dust accumulation and soil formation of the region. To elucidate these dynamics for much of the past 130.000 years bulk mineralogical and geochemical data are presented supplemented by a high resolution magnetic susceptibility record and by the results of a detailed micromorphological study of loess at Toshan.The last interglacial Luvisol/Phaeozem-like (∼MIS 5e) and the early glacial interstadial steppic palaeosols (∼MIS 5 c and a) are characterized by gradually increasing grain-size and decreasing degrees in decomposition of micaceous and mafic minerals. Pronounced feldspar weathering is detected in the last interglacial and modern soils only, which formed under reduced or absent dust deposition on penultimate and last glacial loess, respectively (postsedimentary). The overall pedosedimentary conditions correspond to large scale trends of increasing drought, dust accumulation and wind strength in southern Eurasia in relation to decreasing moisture availability towards the early Pleniglacial (∼MIS 4), causing soil formation under ongoing dust deposition (synsedimentary). Similar intervals of synsedimentary soil formation are recorded during the interglacial/interstadial-stadial transitions of the early glacial and during pleniglacial (∼MIS 4 to 2) interstadials. The latter are marked by gradual increases in magnetic susceptibility, colour and decreasing texture. Conversely, silicate weathering could not be detected, suggesting that grain-size fluctuations are a primary feature. Thus, windy and arid pleniglacial conditions in southern Eurasia were interrupted by intermittent phases of synsedimentary soil formation, in response to short-lived and relatively moist interstadials. Although the interrelation of these incipient soils, throughout southern Eurasia is afflicted with considerable restrictions, the oscillatory pattern of the Toshan LPS bears great similarity with millennial-scale oscillations recorded in limnic archives of western Asia.