共查询到19条相似文献，搜索用时 859 毫秒
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本文以欧亚黄土中记录的布容一松山极性倒转界线为例,简要回顾近年来对黄土中 古地磁极性界线地层学解释的讨论。研究表明,由于在记录古地磁极性转换时存在不同程度 的“错位”,黄土中所测的极性界线的年代地层意义存在很大的不确定性。就中国黄土而言,第 ８层黄土（Ｌ８）中下部或第８层古土壤（Ｓ８）顶部测得的布容－松山界线系“错位”的产物,该层位 的年龄应老于 ０．７９ＭａＢ．Ｐ。对黄土中测得的Ｃｏｂｂ Ｍｏｕｎｔａｉｎ极性事件界线进行地层学解释, 推论蓝田猿人化石层位的年龄１．２ＭａＢ．Ｐ。 相似文献
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洛川黄土-红粘土序列铁氧化物组成及其古气候指示 总被引：2，自引：0，他引：2
对洛川黄土、古土壤和红粘土中磁性矿物组成、成因和相关系进行了研究。结果表明:黄土磁性矿物以风尘磁铁矿为主,少量的成土赤铁矿和成土磁赤铁矿;古土壤磁性矿物以成土磁赤铁矿为主,成土赤铁矿次之,少量的风尘磁铁矿和赤铁矿;红粘土磁性矿物以成土赤铁矿为主,风尘磁铁矿和成土磁赤铁矿次之,少量风尘赤铁矿。黄土、古土壤和红粘土磁性矿物组成差异,反映了其形成期不同的古气候特性以及不同气候条件下生物地球化学作用强度的差异。干冷的冰期,黄土弱成土作用形成了以粗颗粒的风尘磁铁矿核 赤铁矿边的磁化率载体。间冰期的温暖湿润的古气候最有利于生物活动,强烈生物活动导致古土壤中大量纳米超细磁赤铁矿/磁铁矿产生,形成以磁赤铁矿为主,风尘磁铁矿核 赤铁矿边为辅的磁化率载体。红粘土成壤期,强降雨强蒸发的长干短湿的高温炎热的古气候使得红粘土化学风化强烈,生物地球化学活动较弱,形成以磁铁矿核 赤铁矿边和磁赤铁矿核 赤铁矿边的磁化率载体。黄土、古土壤和红粘土磁性矿物组成、磁性矿物相关系是其形成期独特的古气候指示。 相似文献
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三门峡地区黄土与古季风 总被引：10，自引：2，他引：8
位于黄土高原东南缘的三门峡黄土地层,以陕县张汴乡村剖面为其典型代表。厚度１５３ｍ的曹村剖面由上部厚１４５ｍ的黄土地层和下伏红粘土沉积组成,黄土地层为Ｌ１－Ｌ３３的连续风尘沉积。磁性地层研究显示：Ｂ／Ｍ界线位于Ｌ７下部,Ｊ事件位于Ｓ１１／Ｓ１２,Ｏ事件位于Ｌ２３－Ｌ２６,Ｍ／Ｇ界线位于黄土与红粘土界线之上２０ｃｍ处。古季风代用指标的磁化率、碳酸盐及〉３０μｍ的粒度组分均显示了约２．６Ｍａ以来季风变迁 相似文献
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最直观、最直接的古气候记录莫过于陆相黄土地层,它由许多黄土和古土壤层叠覆而成,详细地记录了第四纪以来的古气候变化。黄土高原中部黄土和古土壤的风化和发育程度可以用磁学参数,如磁化率等来描述。本文作者对甘肃西峰剖面约13万年以来的黄土地层做了详细采样,测量其磁滞回线各参数,频率磁化率、低场和高场磁化率、温度磁化率、磁组构等参数。研究表明,黄土与古土壤中的磁性矿物组分相似而且稳定。磁铁矿、赤铁矿和磁赤铁矿(主要是磁铁矿)的含量及其颗粒大小决定了它们的磁学特征。黄土和古土壤的磁学性质差别主要受成土过程中形成细小磁铁矿的影响。 相似文献
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详细的古地磁及岩石磁学研究表明磁铁矿和赤铁矿是宝鸡古土壤层S7和黄土层L8的特征剩磁的主要载磁矿物,在稳定的正反极性期间,这两种磁性矿物携带的剩磁方向完全一致.然而,在地磁漂移事件或者松山-布容(M-B)极性转换的过程中,这两种载磁矿物有时携带的剩磁方向不同.高分辨率的磁性地层结果证实宝鸡古土壤层S7和黄土层L8能记录300～500年的短期地球磁场极性倒转事件.经与日本大阪湾高分辨率的海洋沉积物中记录的同期短期极性倒转事件相比,估算宝鸡剖面土壤层S7和黄土层L8的天然剩磁锁定深度小于5～8 cm. 相似文献
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利用Ｂ／Ｍ地磁极性倒转层位０．７３ＭａＢ．Ｐ．时间参考点，通过黄土剖面１０Ｂｅ变化曲线与深海ＳＰＥＣＭＡＰδ１８Ｏ变化曲线匹配拟合，求得洛川黄土剖面０．７５Ｍａ以来的相对连续时标。时标精度约５０００—１００００ａ。由于０．１５Ｍａ以来洛川剖面加密取样以及１０Ｂｅ、δ１８Ｏ两曲线之间更好的相关性，１０Ｂｅ相对时标精度与ＳＰＥＣＭＡＰδ１０Ｏ时标精度大体相同，即３０００—５０００ａ。各时期１０Ｂｅ通量与黄土堆积速率之间存在十分好的线性相关关系，展示了一条崭新的地层定年途径。黄土１０Ｂｅ记录３５０００ａＢ．Ｐ．处的Ｒａｉｓｂｅｃｋ峰可被用作地层时间参考点。黄土１０Ｂｅ／(２６)Ａｌ值、黄土石英中“就地”成因１０Ｂｅ／(２６)Ａｌ值以及“就地”成因１０Ｂｅ浓度等均可望应用于黄土地层精确定年。 相似文献
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中国北方陆相沉积5.30Ma磁性地层序列 总被引：8，自引：2，他引：6
本文通过中国北方新第三纪晚期典型剖面的磁性地层研究,建立５．３０Ｍａ以来中国北方陆相沉积积磁性地层序列。中国黄土记录了Ｂｒｕｎｈｅｓ正极性带与Ｍａｔｕｙａｍａ负极性带,年龄约２．５０Ｍａ。静乐红土（包括静乐剖面,榆林剖面,蓝田剖面）对应于Ｇａｕｓｓ正极性带与Ｇｉｌｂｅｒｔ负极性带,年龄约２．５０￣５．３０Ｍａ。三门组记录了Ｍａｔｕｙａｍａ负极性带下段,年龄约１．２０￣２．５０Ｍａ。游河组记录了Ｇａ 相似文献
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通过中国北方５．３０Ｍａ以来含丰富哺乳动物化石的典型剖面的磁性地层研究,建立５．３０Ｍａ以来中国北方陆相哺乳动物群与磁性地层序列对比。中国黄土记录了Ｂｒｕｎｈｅｓ正极性带与Ｍａｔｕｙａｍａ负极性带,黄土年龄约２．５０ＭａＢ．Ｐ．,其中发现有午城动物群、公王岭动物群、阳郭动物群、陈家窝动物群与靖远动物群。三门组记录了Ｍａｔｕｙａｍａ负极性带下段,年龄约１．２０—２．５０Ｍａ,其中发现有三门动物群。静乐剖面的静乐红土对应于Ｇａｕｓｓ正极性带上段,年龄约２．５０—３．００Ｍａ,其中发现有静乐贺丰动物群。游河组记录了Ｇａｕｓｓ正极性带,年龄约２．５０—３．４０Ｍａ,其中发现游河动物群。泥河湾沉积对应于Ｂｒｕｎｈｅｓ正极性带、Ｍａｔｕｙａｍａ负极性带、Ｇａｕｓｓ正极性带,年龄约０．１３—３．４０Ｍａ。其中小长梁剖面记录了Ｂｒｕｎｈｅｓ正极性带与Ｍａｔｕｙａｍａ负极性带上段（含Ｊａｒａｍｉｌｏ亚带）,年龄约０．１３—１．００Ｍａ（其中含化石及石器地层年龄约０．９０—１．００Ｍａ）。榆社盆地麻则沟组记录了Ｇａｕｓｓ正极性带（２．５０—３．４０Ｍａ）,高庄组记录了Ｇｉｌｂｅｒｔ负极性带（３．４０—５．３０Ｍａ）。 相似文献
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南方红土是中国分布最广的第四纪土状堆积,蕴含丰富的古气候、古地理以及古人类演化的信息。然而,南方红土地区长期高温多雨的气候造成许多定年材料的缺乏,导致其年代学研究进展比较缓慢。磁性地层学方法是一种适合于中、新生代海陆相沉积物定年的快捷、有效的方法,近年来南方红土的磁性地层年代学研究取得了很好的结果。文中比较系统地总结了近年来南方红土磁性地层年代学研究方面的进展。这些研究显示南方红土中的载磁矿物包括赤铁矿、磁赤铁矿、磁铁矿和针铁矿,其中磁铁矿和赤铁矿是特征剩磁的主要载体。磁性地层结果表明南方红土记录了Matuyama负极性时晚期至Brunhes正极性时早-中期的沉积,其沉积起始年龄不晚于Jaramillo正极性亚时,即早于11 Ma。这些磁性地层学结果为揭示南方红土记录的环境变化和中国南方亚热带地区早期人类演化提供了年代学基础。 相似文献
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LEI Xiangyi YUE LepingLoess Research Section Department of Geology Northwest University Xi'' an Shaanxi 《《地质学报》英文版》1998,72(4):420-431
The Fengzhou loess section is very typical in the Qinling Mountains. The section, which is about 82 m thick and underlain by Neogene red clays, consists of 33 layers of loess and 33 layers of palaeosol. It covers the Brunhes normal polarity zone and Matuyama reversed polarity zone, and the B/ M boundary is located in the middle part of loess layer 8 (L8). The loess of the Matuyama reversed polarity zone records the Jaramillo, Olduvai and Reunion normal polarity subchrons. The boundary between the Matuyama reversed polarity zone and Gauss normal polarity zone (M / Ga) appears on the lithological boundary between loess and Neogene red clays. Loess accumulation in the Fengzhou section started before 2.48 Ma B.P. Based on the stratigraphical structure, the material composition and magnetic susceptibility curve of the Fengzhou loess section, the palaeoclimatic changes during the last 2.48 Ma in the Qinling Mountains are subdivided into 66 cold-dry and warm-humid stages, equivalent to 33 climatic cycles. The 相似文献
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山西省榆社县王宁剖面的古地磁测试结果表明，Ｒ红土始自高斯正极性带顶部，向上跨越包括奥杜威极性亚带在内的松山负极性带下半部。这一结果揭示了老Ｒ红土的存在，对于确定Ｒ红土的层位和沉积年代提供了重要依据。Ｒ红土磁化率值的变化与土壤化程度呈正相关性，反映了形成期内气候波动的特征。在它所跨越的１Ｍａ间，Ｒ红土记录了９次明显的气候波动。这种由古土壤层和Ｒ红土层更迭及磁化率峰谷交替表现出来的气候波动韵律与天文韵律中０．１Ｍａ周期相近。且红土的磁化率各向异性度很小，线理、面理同等发育，粘滞剩磁很强，以及阻挡温度谱等主要磁学性质都与原生黄土系列相近，意味着二者成因的相似性。 相似文献
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One hundred and seventeen oriented specimens of loess (in the form of cubes with an edge of 4 cm) were collected from the Wucheng loess section in Xixian County, Shanxi Province. After magnetic cleaning in an alternating field the remanent magnetization of specimens was measured with an astatic magnetometer (sensitivity 4×10?3 emu/cm3). The normally magnetized zone of the Brunhes normal epoch is recorded in upper Pleistocene Malan loess and middle Pleistocene Lishi loess which contain typical Zhoukoudian fauna. The reversely magnetized zone of the Matuyama reversed epoch is observed in lower Pleistocene Wucheng loess, whose fossils are found corresponding to Villafranchian Nihowan fauna. 相似文献
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对黄河三门峡地区曹村黄土剖面L1至L13(年代持续约1.1Ma)的高分辨率古地磁研究发现:布容/松山界线位于第8层古土壤(S8)的顶部,贾拉米洛正极性亚时的顶、底界分别位于S10和L13的顶部,上述古地磁极性转换界线与洛川标准剖面一致。“上粉砂层”(L9)的绝大多数样品特征剩磁方向与现代地磁场方向一致,而其中的弱发育古土壤层(L9SS1)则呈预期的反极性特征。综合L9的厚度、岩性和岩石磁学特征,认为这一巨厚的正极性带可能反映了完全由岩性所控制的重磁化特征。对于L9重磁化的原因,似乎很难用后生的化学剩磁和粘滞剩磁来解释。文章尝试性地提出,可能在L9沉积后的间冰期(对应S8)和布容正极性时内气候较湿润的时期,由于雨水的向下渗透而诱导了其中强磁性矿物(磁铁矿)在沉积后随地磁场方向的变化而进行了重新排列。 相似文献
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The Brunhes/Matuyama boundary and magnetic parameters related to climatic changes in Quaternary sediments of Argentina 总被引：1，自引：0，他引：1
《Journal of South American Earth Sciences》2007,23(1):17-29
Rock magnetic properties have been measured in a loess–paleosol sequence in the Gorina Quarry, which previously have been suggested to contain records of the Brunhes and part of the Matuyama polarity chrons. Lowest susceptibility values (below 50 × 10−8 m3/kg) are generally related to intensive weathered horizons, whereas highest values are obtained in loess layers (250 × 10−8 m3/kg) as a result of the greater ferromagnetic content in the parent material. The frequency-dependent part of susceptibility ranges between 0.5% and 6.8%; the higher value was obtained in B horizons of paleosols, which can be attributed to superparamagnetic contributions. Hysteresis loops indicate that the differences in ferrimagnetic and paramagnetic content in the sequence reflect the degree of pedogenesis. The same conclusion can be drawn with isothermal remanent magnetization. This point is relevant for determining past climatic changes because the wind-blown titanomagnetites from Cordillera de Los Andes during glacial periods were altered during interglacial periods. The mode of pedogenesis appears not only to control such alterations but also to produce other magnetic minerals. 相似文献
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《Quaternary Research》2014,81(3):433-444
A high-resolution rock magnetic investigation was performed on the Chaona Quaternary loess/paleosol sequences in the Central Chinese Loess Plateau. Based on a newly developed independent unturned time scale and magnetic records, we reconstructed the history of the East Asia monsoons during the last 3 Ma and explored the middle Pleistocene climate transition (MPT). Rock magnetic results show that the loess layers are characterized by relatively high coercivity and remanent coercivity, lower magnetic susceptibility (MS), and that the paleosol layers are characterized by relatively high MS, saturation magnetization and remanent saturation magnetization. Spectrum analyses indicate that there are various periods in addition to orbital periodicities. According to the onset and stable appearance of 100 kyr period, we consider that the MPT recorded in this section began at ~ 1.26 Ma and was completed by ~ 0.53 Ma, which differs from previous investigations based on orbitally tuned time scales. The forcing mechanism for the MPT was more complicated than just the orbital forcing. We conclude that the rapid uplift of the Tibetan Plateau may have played an important role in the shift of periodicities during the middle Pleistocene. 相似文献
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M.A. Krainov A.Yu. Peskov A.V. Kosynkin M.I. Kuz’min 《Russian Geology and Geophysics》2013,54(11):1402-1408
The relative paleointensity of sedimentation is studied for sediments stripped by deep-water drilling in Lake Baikal (BDP-99 borehole). Two intervals are considered: 0–420 ka (Brunhes chron) and 1.05–1.09 Ma (before, during, and after the Matuyama–Jaramillo reversal). For these intervals, curves of the ideal magnetization of samples are plotted.The paleointensity data obtained along the borehole section reveal four excursions for the Baikal sediments whose identification on the inclination–depth curve is complicated.The lower part of the section (Matuyama–Jaramillo subzones) shows a paleointensity decrease by a factor of five or more relative to periods of invariable polarity. 相似文献