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Pleistocene climatic history in the Minusinsk Basin, southern Siberia, Russia.

机译:俄罗斯西伯利亚南部米诺辛斯克盆地的更新世气候历史。

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摘要

Climatic evolution in Siberia during the Pleistocene is still insufficiently known. A complete, high-resolution palaeoclimatic record for the last two glacial-interglacial cycles in southern Siberia has been studied at Kurtak in the Northern Minusinsk Basin. The unique, 34 m thick Late Quaternary sequence of loess and palaeosols (Section 29) with a differential degree of pedogenic development provides evidence of a strongly fluctuating, but patterned climatic change, with an increasing deviation amplitude during the Late Pleistocene cycle (130-10 ka). Mineralogical composition and grain morphology of the undifferentiated (aeolian and colluviated) loess indicates a local provenance and a short transport of the silt derived by glacial erosion of the granitic and metamorphic bedrock in the Kuznetskiy Alatau and the Eastern Sayan Mountains, and subsequently subaerially redeposited from the alluvial plain in the Yenisey River valley.;Recorded palaeoclimatic regularities manifested by a succession of Chernozemic, Brunisolic and Gleyed Regosolic soils are consistently traced by magnetic susceptibility characterized by markedly increased values during cold intervals, and decreasing values for warm intervals. This specific pattern (with the magnetic susceptibility minima in the most weathered interglacial soils) radically differs from the Chinese loess record, where the ferromagnetic concentration in palaeosols correlates directly with the enhanced degree of pedogenesis. A process of ferromagnetic mineral depletion during soil development under periodic oxidation and reduction conditions is proposed to account for the magnetic susceptibility decline because of leaching of less stable iron hydroxides. Increased amounts of unweathered iron minerals (magnetite, titanomagnetite and ilmenite) in the Siberian loess inherited from the glacially-eroded primary geological sources, coupled with the more intense aeolian activity during cold climatic intervals, are believed to be the main controlling factors.;The loess-palaeosol record from the Kurtak area, well-correlated with the marine Oxygen Isotope Stages 1-5 provides evidence of a pronounced climatic change in the Minusinsk basin during the Late Pleistocene, with very cold and dry glacial stages, and cool and more humid mid-last glacial interstadials. The last interglacial sensu lato (130-73 ka) includes several cold and warm substages with a strongly continental trend during its first half. The palaeoclimate evolution is manifested by shifts in the major ecotones, with southern taiga established during the early interglacial and early interstadial stages under more humid and warmer conditions, succeeded by semiarid steppe and tundra-steppe, respectively. A gradual transition into glacial stages is evidenced by expansion of boreal forest and tundra-forest, eventually replaced by cold periglacial tundra-steppe with intensive loess sedimentation during glacial maxima. A cold-adapted arboreal vegetation appeared during warmer oscillations. Fossil fauna and cultural remains suggest analogous Late Pleistocene environments throughout southern Siberia.
机译:在更新世期间西伯利亚的气候演变仍然知之甚少。西伯利亚南部最后两个冰河间冰期循环的完整的高分辨率古气候记录已经在米努辛斯克盆地北部的库尔塔克进行了研究。黄土和古土壤的独特的,厚达34 m的晚第四纪层序(第29节)具有不同的成岩作用,提供了强烈的波动但有规律的气候变化的证据,在晚更新世周期中偏差幅度增加(130-10) K a)。未分化(风成和凹生的)黄土的矿物学组成和晶粒形态表明,库兹涅茨基阿拉托和东部萨彦岭的花岗岩和变质基岩受到冰蚀侵蚀后,产生了淤泥的局部物产和短暂的运移,随后从地下沉积叶尼西河谷冲积平原;记录的古气候规律,由一系列的切诺兹米奇,布鲁尼索利斯和格利德雷索斯科利土壤表现出来,始终以磁化率追踪,磁化率的特征是在寒冷时期明显升高,而在温暖时期降低。这种特殊的模式(在最风化的冰间期土壤中具有最低的磁化率)与中国的黄土记录根本不同,在中国黄土记录中,古土壤中的铁磁浓度与成岩作用的增强直接相关。为了解决由于不稳定的氢氧化铁的浸出而引起的磁化率下降,提出了一种在土壤发育过程中周期性氧化和还原条件下铁磁矿物耗竭的方法。从冰川侵蚀的原始地质资源继承的西伯利亚黄土中未风化的铁矿物质(磁铁矿,钛磁铁矿和钛铁矿)的数量增加,加上在寒冷的气候区间内风沙活动更加强烈,被认为是主要的控制因素。库尔塔克地区的黄土古土壤记录,与海洋氧同位素第1-5期密切相关,提供了米诺辛斯克盆地晚更新世期间明显的气候变化的证据,冰川阶段非常寒冷和干燥,而凉爽和潮湿最后的冰川间质。最后一个冰期间的拉苏(130-73 ka)包括几个寒冷和温暖的子阶段,在其上半年具有强烈的大陆性趋势。主要气候交错带的变化表明了古气候的演变,南部的针叶林在早期的冰间期和早期的陆间期建立在更加潮湿和温暖的条件下,分别是半干旱草原和苔原草原。北方森林和寒带草原森林的扩张证明了向冰川阶段的逐步过渡,最终被冰期最大的冷黄土寒带草原草原所取代,并伴有大量的黄土沉积。在较暖的振荡过程中出现了适应寒冷的树栖植被。化石的动物群和文化遗迹表明整个西伯利亚南部都有类似的晚更新世环境。

著录项

  • 作者

    Chlachula, Jiri.;

  • 作者单位

    University of Alberta (Canada).;

  • 授予单位 University of Alberta (Canada).;
  • 学科 Geology.;Paleoecology.
  • 学位 Ph.D.
  • 年度 1995
  • 页码 234 p.
  • 总页数 234
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 老年病学;
  • 关键词

  • 入库时间 2022-08-17 11:49:35

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