Mangshan Loess in Central China and the Paleomonsoon Variations since the Last Interglaciation

The Mangshan Yuan is a loess platform on the southern bank of the Yellow River, which is located in northwestern Zhengzhou of Henan Province, China. The typical Zhaoxiayu section of the Mangshan Yuan preserves stratigraphical loess units above S10 with a total thickness of 172.1 m, which includes 15.7 m of the last interglacial paleosol S1, 77.3 m of the last glacial loess L1 that consist of 41.6 m of the late stade L1LL1, 13.2 m of the interstade L1SS1 and 22.5 m of the early stade L1LL2. Based on the age marking points by correlating magnetic susceptibility of the section with the SPECMAP curve, the timescale of the section was constructed, and the average accumulation rate and the resolution of each loess strata over the S2 were subsequently calculated using the susceptibility age model. The results indicate that strata units developed in the glacial, interglacial stages, stadial and interstadial show substantial differences in grain size, average accumulation rate and time resolution ub the Zhaoxiayu section. Specifically, the average accumulation rate of the loess L1LL1 is 3.45 mm/a, whereas that of paleosol S1 is only 0.28 mm/a. Based on the high-resolution records of magnetic susceptibility and >45μm fraction percentage of the loess-paleosol, the summer and winter monsoon variations as well as their interrelations since the last interglaciation have been discussed, which were correlated with the SPECMAP and the GRIP climate records.

Two pedogenic models for paleoclimatic records of magnetic susceptibility from Chinese and Siberian loess

The magnetic susceptibility (MS) of Chinese loess showing a general proportional relationship to pedogenic grade has been widely recognized and used for reconstruction of paleoclimate by Quaternary scientists. The in-situ pedogenic enhancement of ferrimag

Spatial-temporal Characteristics of Holocene Paleosols in the Chinese Loess Plateau and Paleoclimatic Significance

The evolution of Holocene climate was investigated using grain size and magnetic susceptibility of the Holocene paleosols from Baicaoyuan(BCY),Xifeng(XF) and Linyou(LY) sections in the northwest,central and southern Chinese Loess Plateau(CLP).The results show that the Holocene in the B CY,XF and LY paleosol sections could be divided into three phases:during the early Holocene(11.8-10.5 kyr B.P.),increased magnetic susceptibility(χ) and frequency-dependent magnetic susceptibility(χ) and decreased median grain size(Md) indicate that the East Asian Summer Monsoon(EASM) has become more intense and the climate has changed from cold to warm.During the middle Holocene(10.5-5.0 kyr B.P.),the values of χ,χand 2-5 μm grain-size fraction(GT2/5) are higher and Md and 30-63 μm grain-size fraction(GT3 0/6 3) are the lowest,which reflect a warm and humid regional climate.At~8.0 kyr B.P.,there was a transient dry-cold climatic spike corresponding to a Heinrich Event,the cold event was likely due to the collapse of the Laurentide ice sheet.During the late Holocene(5.0-0 kyr B.P.),χ and χvalues are the lowest,while Md and GT30/63 are high,as proxies of a weakened EASM,when the dry-cold climate prevailed in the region.Decreased irradiance since 5.0 kyr B.P.may have caused climatic cooling and drying.Spatially,the increased main peak values and skewness from BCY,XF to LY sections show that the grain size became fine,the East Asian Winter Monsoon(EAWM) reduced,and climate was warmer and wetter from northwest to southeast.In addition,Md can be used as alternative proxy for EAWM,while χis positive with the intensity of EASM under semiarid climate conditions in CLP.

Magnetic susceptibility of the Xifeng section and its paleoclimate significance

Magnetic susceptibility (MS) is one of the most important indicators of the East- Asia summer monsoon. Presented in this study is a high resolution magnetic susceptibility record from the Xifeng section, which consists of Quaternary loess-paleosol sequence and Pliocene red clay. Variations in magnetic susceptibility are well correlated with the δ18O record in deep-sea sediments and the eolian flux of Greenland. The climatic evolution in the Xifeng section shows that since the Late Tertiary, the driving force of the East-Asia paleo-monsoon is correlated with solar radiation on a 10-ka time scale .

ROCK MAGNETISM OF LOW TEMPERATURE AND CHARACTER OF MAGNETIC PARTICLES IN LOESS

Ⅰ. INTRODUCTIONLoess strata in China consist of alternating loess and palaeosol layers; the loess represents the dust deposition in dry-cold climatic condition while the palaeosol is the product developed in warm-humid environment. The magnetic susceptibility of loess stratigraphy as a palaeoclimate indicator is a significant physical parameter, which was first put forward

Rock-magnetic characteristics and mechanisms of the Titel loess-paleosol sequence in northern Serbia since late Middle Pleistocene

The changing pattern of magnetic characteristics in eastern European loess deposits is the most similar across the world to that of the Chinese Loess Plateau,both of which are dominated by the strength of pedogenesis.Hence a systematical study to the rock magnetism of eastern European loess is not only helpful for understanding the paleoclimatic information preserved by themselves,but also beneficial for promoting the cognition of the pedogenic mechanism in loess records.In this study,a detailed rock-magnetic analysis of seventy loess/paleosol samples,taken from the Titel Loess Plateau in northern Serbia,is carried out for a better understanding of the magnetic records since late Middle Pleistocene.The results provide us some implications.First,the magnetic susceptibility values of the paleosols in the Titel loess-paleosol sequence are generally less than 100×10^(-8)m^(3)kg^(-1),significantly lower than those of the loess sections in the Chinese Loess Plateau,even though they are under similar climatic conditions.However,the behaviors of the parameters related to the distributions of magnetic particles in these two regions are similar.The difference in the contents of ferrimagnetic minerals is the leading reason that caused the difference in their magnetic characteristics,but the mechanism is still open to study.Second,based on the analysis of thermomagnetic curves,a gradually increasing trend of the relative contents of maghemite over the last four glacial-interglacial cycles is identified.The realization of thermally unstable maghemite from Chinese loess leads us to speculate that the long-term increasing trend of the relative contents of maghemite in Titel loess-paleosol sequence likely is a mineralogical response to the progressive enhancement of continental climate in the Pannonian Basin since the Middle Pleistocene.

Evolution of the summer monsoon regime over the Loess Plateau of the last 150 ka

On the magnetic susceptibility data of 30 sections covering the Loess Plateau, contour maps of susceptibility are drawn out for 5 time intervals including the last second glaciation (150 ka B.P.), the last interglaciation (130 - 73 ka B.P.), the interstadial of the last glaciation (24 - 59 ka B.P.), the last glacial maximum (18 ka B.P.) and the Holocene optimum (9ka B.P.). The susceptibility value of the last glaciation maximum loess is regarded as the base value of pedogenic loess or paleosol. The susceptibility increment to the base indicates the summer monsoon activity and its strength. On this assumption and the susceptibility contour maps, the variation sequence of the summer regime are reconstructed for the last 150ka. The extent and the northern boundaries of the summer monsoon front activity are also estimated for every stage. It is suggested that the evolution history of the summer monsoon regimes revealed by the susceptibility contour maps not only provides information of position, strength and their configuration of the climate members influencing the summer monsoon, but also provides some climatic signals from the polar region and southern hemisphere.

Environmental magnetism and paleoclimatic interpretation of the Sanmenxia loess-paleosol sequence in the southeastern extremity of the Chinese Loess Plateau

这是多参数矿物质的一份报告在在间隔 ofL1 上的中国黄土高原(CLP ) 的 SE 极限的 Sanmenxialoess-paleosol 两行诗的磁性的结果 - 跨越最后 1 个妈的 L13。这些结果显示出那团特定的磁性的危险性(x) ， Xarm 和 SIRM，他们的比率展出平行 stratigraphic 变化。Sincesuperparamagnetic (SP ) 粒子有重要贡献到到顽磁的 X 而是没有贡献，例如，手臂和 SIRM，在 x 之间的强壮的线性关联一(i 顽磁(例如， ARMand SIRM ) 建议生产成土作用的磁性的谷物是主要在里面小单个领域范围。因而，到想在以前的研究的体积 x 的 SP 粒子的重要贡献显然被过高估计。在 Sanmenxia 和中部的谷物尺寸的 2arm/X 数据从 CLP 显示的内地典型黄土节记录强壮的相似，暗示 Jarm/X 可以为监视变化 offerrimagnetic 谷物被认为是可靠指示物缩放。S 比率和 HIRM 的结果((SIRM+IRM_(.3T ))/2 ) 大小显示在与成土作用联系的 paleosols 有软磁铁矿 / 磁赤铁矿和 hardhematite/goethite 的重要改进。

中国第四纪黄土环境磁学研究进展

中国黄土分布广泛、沉积连续性好 ,是进行磁性地层研究和重建古环境、恢复古气候的理想材料。中国黄土高原黄土—古土壤序列的环境岩石磁学性质详细地记录了 2 .5Ma BP以来古气候和古环境变化的信息 ,尤其是黄土和古土壤的磁化率作为很好的气候代用指标已得到广泛应用。古土壤磁化率增强成因机制一直在争论中 ,其中 ,与气候变化关系密切的成壤作用对古土壤磁化率增强起主导作用的观点已被普遍接受 ,目前利用不同方法建立了磁化率气候转换函数 ,从而使重建古降水量和古温度成为可能。

黄土-古土壤磁化率述评

黄土－古土壤是研究亚洲大陆内部过去２．６０Ｍａ间古环境变化的最好记录，特别是研究其与季风气候形成的密切关系，以及黄土扩展到日本甚至广泛的太平洋区域（北半球）等重大气候环境现象。其研究对第四纪古环境恢复具有极大的意义。最近基于黄土－古土壤而进行的古环境研究取得了很大的进展，一是因为黄土－古土壤磁化率的变化与深海沉积物的氧同位素比的变化非常一致，指示陆相沉积物亦可作为古气候的良好代用指标。另一方面，为什么黄土－古土壤中的磁化率存在差别，特别是古土壤磁化率为什么增大等问题，已成为这１０ａ间岩石磁学研究的中心课题。磁化率不单单只与强磁性矿物的含量成比例，同时也与不同种类的强磁性矿物的粒径分布有很大关系。发现在土壤化过程中形成的０．１μｍ以下的单畴－超顺磁性颗粒是造成古土壤磁化率增强的主要原因，它是否与生物作用有关目前仍不确定，但不论哪种情况，都可以肯定暖湿气候是古土壤磁化率增加的共同原因。磁化率增强的系统理论明确建立以来，使得从磁化率的变化来推算降水量，以及建立古气候复元的定量模型等都已成为可行。

中原邙山黄土与末次间冰期以来古季风特征

中原邙山赵下峪剖面出露S10以上黄土地层,厚度大于172.1m。末次间冰期S1古土壤厚15.7m,末次冰期L1黄土厚达77.3m,其中晚冰阶L1LL1黄土、间冰阶L1SS1古土壤和早冰阶L1LL2黄土分别厚41.6m、13.2 m和22.5 m。邙山黄土是厚度最大的晚更新世黄土地层剖面之一,记录了丰富的气候环境变化信息。用SPECMAP氧同位素曲线确定的阶段界限的日历年龄为标定点和磁化率年龄模式,获得相应的时间标尺,据以计算出S2以上各层段的平均沉积速率和分辨率。邙山黄土倒数第二间冰期以来不同冰期或冰阶与间冰期或冰阶的粒度、平均沉积速率和分辨率有很大的差异,其中以末次冰期晚冰阶L1LL1黄土的平均沉积速率为最高,达3.45 mm／a,而末次问冰期S1古土壤的沉积速率亦高达0.28 mm／a。本文主要根据赵下峪剖面的磁化率和>45μm粗颗粒含量变化曲线,并与格陵兰GRIP冰心和深海SPECMAP氧同位素曲线对比,讨论末次间冰期以来古季风特征及其相互关系。

不同类型沉积物磁化率的比较研究和初步解释

沉积物的磁化率分析以被广泛应用在第四纪古气候研究中,不同类型沉积物磁化率的解释可能存在明显的差异。本文选择了黄土、冲积物、湖积物、风沙堆积和南方红土等五种不同类型的沉积物,进行了磁化率的测试,粒度和孢粉分析,试图通过对沉积物磁化率和相关古环境指标的研究,对不同类型沉积物的磁化率予以对比并进行初步解释。研究结果表明,黄土和湖泊沉积中磁化率的变化主要受气候变化的影响,是指示古气候的重要指标;河流沉积物和风沙沉积物的磁化率主要受粒度的影响;影响南方红土磁化率的因素十分复杂,其磁化率的解释比较困难有待进一步的研究。这一研究表明,鉴于不同沉积物磁化率的影响因素存在明显的不同,因此在运用磁化率进行古环境解释时须持慎重态度。

川西漳腊黄土地层与气候变化

川西高原风成黄土广泛分布,其中漳腊盆地黄土剖面厚约9.5 m。根据磁化率、粒度和地层特征,并通过与金川黄土和甘孜黄土剖面的对比,可将漳腊黄土地层划分为冰后期S0古土壤、末次冰期L1复合黄土、末次间冰期S1复合古土壤、倒数第二冰期L2黄土等4个地层单位,其中L1复合黄土可细分为L1L1、L1S1、L1L2、L1S2和L1L3等5个次级地层单位,S1复合古土壤又可细分为S1S1、S1L1、S1S2、S1L2和S1S3等5个次级地层单位。通过磁化率曲线与SPECMAP氧同位素曲线对比,结合地层剖面特征和前人认识,初步认为漳腊盆地黄土沉积开始于150 ka±。漳腊黄土磁化率、粒度曲线的波动旋回很好地对应了黄土-古土壤风尘堆积序列,记录着该区约150 ka以来的气候变化,本区自150 ka以来共经历了6次以冬季风占主导地位的时期和6次夏季风强盛时期。

山西临汾盆地黄土及其形成古环境

叙述了临汾盆地黄土地层分布特征，并根据王绪典型黄土剖面孢子花粉、颗粒成分、古土壤特点以及磁化率变化，将王绪剖面划分为１８个气候组及１９个温暖期和２０个干冷期，每个干湿期构成一个气候旋回，这些旋回均可同深海沉积物所揭示的古气候旋回对比。

东亚夏季风气候变迁强迫机制初探

基于反映东亚夏季风气候变迁的洛川黄土磁化率记录及一系列古气候模拟结果 ,通过统计分析研究了地球轨道参数、全球冰量及大气 CO2 含量等强迫因子对东亚夏季风气候变迁的影响。结果表明 ,在 10 5 a时间尺度上东亚夏季风气候变化大约有一半是由全球冰量消长引起的 ,约有 1/ 4归于大气温室气体含量的改变 ,而直接受到地球轨道的线性驱动作用很小。但在 10 3～ 10 4a时间尺度上 ,冰期时东亚季风边缘地区夏季气温和降水变化的70 %～ 80 %是由冰期边界条件 (包括冰量和大气温室气体含量 )造成的 ,而冰后期轨道强迫可以解释季风边缘地区夏季气候变化的 6 0 %以上。

Paleoclimatic record from Chumbur-Kosa section in Sea of Azov region since Marine Isotope Stage 11

Abstract： Loess-paleosol sequences preserve records of climatic change during the Quaternary, which is important for paleoclimate study. In this study, a loess-palaeosol sequence from the Chumbur- Kosa （CK） site in the Sea of Azov region was investigated to reconstruct climatic variability during the Marine Isotope Stage （MIS）11- MIS 1, using proxies of grain size （GS）, magnetic susceptibility （xlf and Xfd（%））, carbonate content （CaCO3%） and soil color The results enabled formulation of a detailed description of the climatic characteristics related to each individual layer. The sequence indicates that the paleoclimate shifted progressively towards increasingly cooler, somewhat drier conditions. The CK section may thus be ideal for reconstructing climatie eondifions during the Middle and Late Pleistocene in the Sea of Azov region. However, the ）Of value of paleosol $2 in the CK profile indicates different characteristics from the other paleosol layers, dilution of carbonate resulting from carbonate leaching in L2 may be the main reason for the decrease in magnetic susceptibility. Furthermore, through simple analysis part of the environmental evolution process in the Sea of Azov region and Serbia during Middle and Late Pleistocene cycles. The climate cycle expressed by Xfd（%） and Xlf variations show similar patterns, with rapidly alternating cold and warm intervals. Nevertheless, although the two areas had different climatic regimes, geographical settings, and loess source areas, both exhibited similar climate change trends since the MIS 11.

中国东北末次冰期松原黄土的释光测年及其古气候意义初探

本文以中国东北松原黄土为研究对象,通过光释光测年建立其末次冰期年代标尺,并探讨磁化率和平均粒径这两个黄土研究中常用的气候替代性指标的可能指示意义。采用成熟的细颗粒石英单片再生(SAR)光释光(OSL)测年技术获得了松原剖面顶部5.5 m年代6个,并获得了2 cm间距的低频磁化率和平均粒径这两个常规参数。石英OSL测年相关检验证实了该技术测量松原黄土的可靠性。测年结果表明,松原剖面顶部5.5 m主要沉积于末次冰期的中晚期,即约5.5—1.8 m((52.18±3.47)—(27.76±1.77)ka)主要堆积于深海氧同位素阶段(MIS)3中晚期,而顶部1.8—0.4 m((27.76±1.77)—(20.61±1.31)ka)堆积于MIS2早期。磁化率自52.18±3.47 ka到27.76±1.77 ka经历了先小幅降低又小幅升高,波动幅度较小,而自27.76±1.77 ka以后,磁化率值呈整体下降并呈现大幅度摆动。平均粒径则自52.18±3.47 ka到46.80±3.13 ka呈明显变小趋势,自46.80±3.13 ka到约20 ka变化不大,自约20 ka以后,平均粒径由约40μm陡然增加至约140μm,并在之后稳定在这一水平。测试结果对比显示,磁化率和粒度的变化不具有明显的相位关系,且同黄土高原渭南剖面末次冰期磁化率和平均粒径的变化也表现出明显的不一致现象。因此,在对松原黄土剖面的研究中,将磁化率和平均粒径分别作为东亚夏季风和冬季风的替代性指标使用时要慎重。

中国黄土磁学与古气候(英文)

近二十年来中国黄土环境磁学的研究基本上是沿着两条主线进行的 ,即磁性地层学和古气候研究两个方面。对早先确定的典型黄土剖面的磁性地层研究表明风成黄土的堆积开始于Matuyama的下界 ,约 2 .6Ma。而近年来对黄土古土壤序列之下的红粘土的进一步研究显示风成堆积的开始比原先认为的要早的多 ,至少可追溯到约 7Ma。尽管目前在古土壤磁化率的增强机制和磁化率如何记录古气候变化等问题上还没有达成广泛的一致 ,而黄土古土壤系列磁化率与深海氧同位素的良好对比可证实中国黄土确是记录全球气候变化非常理想的信息载体。近年来许多学者尝试性提出的其它古气候替代性指标 ,如全岩粒度、稳定同位素组成、FeD/FeT指标、Rb/Sr比值和CaCO3 含量等必将为重建古季风变化和古气候提供重要信息。

黄土高原风成沉积物磁化率各向异性研究

中国黄土高原粉尘堆积以往注重从物源区携带粉尘的古风向,对粉尘沉积→固结期的古风向缺乏研究。本文评述了近年来应用黄土高原黄土、红粘土磁化率各向异性研究古季风风向变迁所取得的一些重要进展并指出磁化率各向异性最大轴和最小轴的方位和倾伏均与沉积→固结期风向变化密切相关。黄土磁组构结果与利用各种统计方法计算出的古风向在多个剖面与现代夏季风方向相似,由此推论黄土是冬季风带来的沙尘在经历夏季风携带的降雨洗礼后才固结而成。而在黄土之下的红粘土地层中的初步研究发现磁组构显示明显的西风带沉积特征,指出这一现象将在今后研究中继续深入探讨。

伊朗黄土高原表土磁性特征与古气候指示意义

全球变化研究中的现代过程研究越来越成为定量重建工作的先决前提,而由于如黄土等气候记录载体沉积分布的全球性与沉积环境的多样性,更需要就具体的研究区进行有针对性的现代过程工作以最大程度地保证重建工作的可靠性。西起地中海、东至帕米尔的广大区域是丝路文明演化的关键地区,其过去气候变化也是了解北半球中纬度气候演化与机制的重要拼图。本研究即采集位于该区之里海东南缘的伊朗黄土沉积区域的现代表土,并联系气候要素考察其磁性特征的空间变化。结果显示主要分布于冬春季节的年均降水其变化控制了亚铁磁性矿物的空间分异,包括次生超细颗粒含量变化与磁赤铁矿化程度,典型的磁学参数如百分频率磁化率值的变化可以定量记录年均降水值的变化。结合相关关系函数,可以为该区过去降水变化的定量重建提供准备并为进一步理解区域气候系统演化与机制提供支持。