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1.
泥河湾盆地东部出露一套厚近百米的以湖相为主的地层.我们测量了洞沟剖面的粒度和磁化率.通过磁化率记录的对比,我们可以将前人确定的古地磁界线转移到我们的深度坐标上来,并建立了初步的时间标尺.样品中粒径在20~50μm之间的颗粒含量时间序列可以与ETP曲线对比,即低含量对应高ETP值.这样的对比意味着在北半球夏季太阳辐射量相对增加的时期,进入泥河湾盆地沉积物中的风尘物质减少了.这与已知的北方风尘的演化历史是吻合的,所以我们认为粒度(20~50μm)含量是泥河湾盆地沉积物中比较可靠的古气候变化的替代性指标.对于沉积速率相对高的时段,即>780ka的地层,我们尝试用轨道调谐的方法建立了高分辨率的时间标尺.新的粒度(20~50μm)含量时间序列滤波获得的20ka和41ka的周期成分与岁差及地轴倾斜度的理论值可以重合.这显示洞沟剖面的粒度(20~50μm)含量记录可以作为轨道调谐的气候曲线. 相似文献
2.
青藏高原东北部西宁-互助地区堆积的厚层黄土是认识高原第四纪环境演化和气候变化的重要信息载体。对西宁泮子山厚层黄土钻孔（181.7m）进行了间隔5cm的采样,在实验室测量了全部样品的粒度,以粒度和北半球高纬太阳辐射数据为材料,选择古地磁年龄作为独立年代控制点,采用改进的自动轨道调谐方法,建立了西宁黄土早更新世以来天文轨道调谐的时间标尺。调谐后的粒度时间序列与ETP曲线在轨道周期上高度相关,在一定程度上证明了轨道调谐方法建立西宁厚层黄土堆积年代标尺的可行性。泮子山厚层黄土的沉积速率在1.0Ma前后发生了明显变化,1.0Ma以来沉积速率的相对高值可能反映了粉尘源区的干旱化程度增强,也指示了亚洲中部和青藏高原干旱环境的急剧发展。西宁厚层黄土年代标尺的建立,对深入认识晚新生代亚洲干旱气候发展过程和青藏高原的环境演化具有积极意义。 相似文献
3.
轨道调谐法是确定第四纪地层时间标尺的主要手段,但人工进行轨道调谐确定时间标尺具有可操作性差、客观性差、工作量大及很难得到最佳结果等缺陷,本文描述了利用计算机自动进行轨道调谐以厘定古气候记录时间标尺的方法步骤.对于不同的气候替代性指标时间序列之间在主要周期频率上的相位关系,作者提出了利用演化凝聚函数法进行计算的新方法.作为实例,利用上述方法对塔吉克斯坦Chashmanigar黄土记录进行了时间标尺和相位关系演化的计算. 相似文献
4.
洛川黄土序列时间标尺的初步建立 总被引：10，自引：0，他引：10
对厚１４０ｍ的洛川坡头黄土剖面黄土层以５ｃｍ，古土壤层以３ｃｍ系统采样，全部样品进行了室内磁化率测量。以黄土序列磁化率变化作为古季风气候变化的代用指标，根据第四纪冰期的Ｍｉｌａｎｋｏｖｉｔｃｈ理论，利用轨道调缠绵的方法初步建立了洛川黄支的时间标尺。通过古地磁场倒转时间的检验以及与宝鸡黄土序列时间标尺对比，表明本文所论述的时间标尺适用于该地区古环境演化的研究。 相似文献
5.
ODP1148站深海沉积岩心的磁化率记录显示出较强的周期性变化规律．研究发现,中新世和渐新世的深海地层物性参数具有很强的斜率周期．Shackletoneta1．利用这一规律,以北半球高纬太阳辐射曲线作为天文调谐的目标,以ODP154航次的深海沉积岩心的磁化率记录作为调谐对象,将磁化率的极大值与北半球天文辐射的极小值相对应,建立了14～34Ma的天文调谐的年代标尺．采用相同的方法,利用南海北部ODP1148站深海沉积岩心的磁化率记录和北半球高纬太阳辐射曲线建立了南海中中新世天文调谐的年代标尺．调谐后的磁化率记录显示了很强的斜率周期和较强的岁差周期,并与太阳辐射在这2个记录上高度相关,此外偏心率周期在磁化率记录中也较显著．调谐后1148站的浮游有孔虫事件年龄与ODP154航次采用相同的天文调谐方法获取的事件年龄异常接近,而与传统方法获取的生物地层事件年龄有较大差距,这在一定程度上证明了利用天文调谐的方法建立中新世深海地层年代标尺的可行性． 相似文献
6.
利用2.5Ma以来经过时标调谐的宝鸡黄土剖面的粒度比值曲线,等时距(1000a)地重构了具2500个样本容量的时间序列。作者在分析此时间序列所记录的古气候变化的混沌特征后发现:2.5Ma以来的古气候是具有有限个自由度的复杂的混沌系统,吸引子关联维数为3.8,饱和嵌入维数为11,它的以最大Lyapunov指数和二阶Renyi熵表征的可预报时效(误差增大一倍所需时间)分别为0.66—0.76Ma和6600—7100a。已有的研究证明该剖面古气候时间序列的大部分时间区间受地球轨道参数的驱动,表明2.5Ma以来的古气候是一种混沌的与周期性的混合式振荡的动力系统。 相似文献
7.
渭南黄土剖面十五万年以来的主要地层界线和气候事件──年代学方面的证据 总被引：5，自引：4，他引：5
本文在渭南黄土剖面所测得的年龄结果和时间标尺研究的基础上，结合粒度、磁化率等气候曲线的分析，对该剖面十五万年以来一些主要地层界线和气候事件的年龄进行了初步讨论，结果如下：１）Ｓ１／Ｌ２界线位于剖面１１８０ｃｍ处，从时间标尺上可知其年龄为１２８８００ａＢ．ｐ．，同末次间冰期起始的年龄相一致；２）Ｌ１／Ｓ１的地层界线年龄为７４２２０ａＢ．Ｐ．，同ＳＰＥＣＭＡＰ曲线中末次间冰期的结束年龄相吻合；３）渭南剖面所指示的末次盛冰期约在２００００～１８０００ａＢ．Ｐ．之间；４）在２００００～１８０００ａＢ．Ｐ．之间的末次盛冰期，有一段不足１０００ａ的快速堆积期，其堆积速率是中国黄土平均堆积速率的１０倍以上。 相似文献
8.
本文在渭南黄土剖面所测得的年龄结果和时间标尺研究的基础上，结合粒度、磁化率等气候曲线的分析，对该剖面十五万年以来一些主要地层界线和气候事件的年龄进行了初步讨论，结果如下：１)Ｓ１／Ｌ２界线位于剖面１１８０ｃｍ处，从时间标尺上可知其年龄为１２８８００ａＢ．ｐ．，同末次间冰期起始的年龄相一致；２)Ｌ１／Ｓ１的地层界线年龄为７４２２０ａＢ．Ｐ．，同ＳＰＥＣＭＡＰ曲线中末次间冰期的结束年龄相吻合；３)渭南剖面所指示的末次盛冰期约在２００００～１８０００ａＢ．Ｐ．之间；４)在２００００～１８０００ａＢ．Ｐ．之间的末次盛冰期，有一段不足１０００ａ的快速堆积期，其堆积速率是中国黄土平均堆积速率的１０倍以上。 相似文献
9.
长江中游砂山的粒度特征及古气候环境意义 总被引：2，自引：1，他引：2
通过对江西梁家渡剖面的野外考察、系统采样和粒度测试,在与中原邙山黄土研究对比的基础上,分析和讨论了长江中游晚更新世风成砂堆积序列(江西梁家渡剖面)的粒度特征;并结合热释光年龄测试数据,按照安芷生等的粒度年龄模式获得相应的年代时间标尺,根据粒度与古气候环境之间的内在联系建立了长江中游地区晚更新世以来的气候环境演化序列;发现长江中游末次冰期以来至少发生过10次暖湿-干冷的气候旋回,其中还记录了发生在约22.0,29.5 ka BP的2次Heinrich事件. 相似文献
10.
《地层学杂志》2017,(2)
水沟—会兴沟遗址是黄土高原东南部三门峡盆地的一个代表性旧石器遗址,传统上将遗址文化层上覆较厚的黄土层看作是"红色土",而认为文化层属于中更新世早期。在对遗址的会兴沟剖面进行野外考察和地层划分基础上,通过对剖面磁化率曲线的测量及与不同黄土剖面土壤地层和磁化率曲线的对比,证实遗址剖面上部的黄土地层包括了S_0~S_8的黄土-古土壤序列。遗址文化层位于S8以下约10m处的河流相地层中,因此其年代必定早于S_8顶部的轨道调谐年龄,即0.8Ma。因为遗址文化层出现在黄河第四级阶地的河流相地层中,而河流相地层是在L9形成时的冰期环境下河流沉积作用的产物,其轨道调谐年龄为0.86~0.95Ma。据此推断该年龄即是遗址文化层的形成年代。 相似文献
11.
2.5Ma以来地球轨道参数变化对黄土粒度变化的线性驱动 总被引：9，自引：7，他引：9
本文对2.5Ma以来宝鸡黄土剖面粒度曲线与ETP曲线做了互功率谱和凝聚函数分析,以期反映风力强度与地球轨道参数变化的关系。结果表明,2.5Ma以来粒度记录中始终存在着与地轴倾斜度、岁差呈线性响应的41000a、23000a和19000a周期;同时,在0.6—0.0MaB.P.时段存在与偏心率呈线性响应的0.1Ma周期,在2.5—1.6MaB.P.时段存在与偏心率0.4Ma呈线性响应的周期。上述结果佐证了地球轨道变化对内陆古气候变化的线性驱动作用,但该理论不能解释在约0.9—0.6MaB.P.和1.6MaB.P.前后出现的二次较大的主导气候周期转型事件。 相似文献
12.
R.G. Johnson 《Quaternary Research》1982,17(2):135-147
The presence of the Brunhes-Matuyama magnetic reversal in deep-sea core sediments makes possible an alternative to the usual K/Ar radioistope method of dating the reversal as found in rocks. The alternative method uses correlations of Northern Hemisphere summer insolation with oxygen-isotope ratios from tropical cores. The latitude-dependent insolation variations are calculated from planetary mechanics and thus provide a highly accurate astronomical time scale. The insolation variations strongly influence glacial-ice volume fluctuations that dominate the oxygenisotope ratio changes recorded in core sediments. The summer half-year insolation variations are identified with corresponding isotope-ratio changes in cores from the present through glacial Stage 20. Misleading effects of discontinuities or major nonuniformities of sediment deposition are avoided by an analysis of the uniformity of V28-238 and V28-239, the principal cores studied, and by comparisons with other cores. The top section (Stages 1 to 10) of V28-238 is uniformly deposited, and for this section an isotope-ratio time scale is chosen that agrees with the thorium-uranium date for the high sea stand of the last interglacial extreme. Over this interval, major glacial extremes (strong isotope-ratio minima) coincide consistently with major insolation minima at times of low orbital eccentricity. In addition interstadials are directly associated with precessional insolation peaks, and the envelope of isotope-ratio peaks resembles the envelope of precessionally dominated insolation peaks. The assumption that the glacial extremes depended similarly on insolation minima during Stages 10 to 20 permits minor age shifts of strong isotope-ratio minima in the two cores (relative to ages based on uniform overal deposition) to match the ages of low-eccentricity insolation minima. The age shifts reflect residual nonuniformities of deposition. The validity of this matching procedure is supported by a resulting consistent identification of principal isotope-ratio peaks with high- and low-latitude coincident insolation maxima. The Brunhes-Matuyama reversal is found intinterglacial Stage 19, and is dated on the astronomical time scale at 790,000 ± 5000 yr B.P. 相似文献
13.
In Argentina, loess/palaeosol sequences were studied from the two sections at Monte Ralo and Corralito, located near to the city of Córdoba in the east of the Pampean ranges. Infrared optically stimulated luminescence (IRSL) and thermoluminescence (TL) dating techniques were applied to set up a more reliable chronological framework for the Upper Pleistocene loess record. IRSL ages increase with depth and are stratigraphically consistent. The oldest loess exposed correlates at least to the penultimate glaciation. The luminescence dating study gives evidence for humid climate conditions with soil formation during the last interglacial period and the middle pleniglacial correlating to Marine Isotope Stage (MIS) 5 and 3, respectively. Three extended periods of soil formation are recorded in the loess/palaeosol sequences at the Corralito section. These buried soils most likely correlate with the last interglacial and early last glacial period. During the Middle Pleniglacial, two palaeosols are intercalated in the loess successions. In the Córdoba area, the periods of increased loess accumulation and deposition of loessic sediments correlate with more arid and glacial periods during the Early Pleniglacial, the Middle Pleniglacial and the Late Glacial. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
14.
MARKUS FUCHS DENIS-DIDIER ROUSSEAU PIERRE ANTOINE CHRISTINE HATTÉ CAROLINE GAUTHIER SLOBODAN MARKOVI&#; LUDWIG ZOELLER 《Boreas: An International Journal of Quaternary Research》2008,37(1):66-73
The Surduk loess section in Serbia provides a 20 m thick pedosedimentary record of the last interglacial–glacial climatic cycle (Upper Pleistocene). Based on optical dating, a chronostratigraphy could be established for the last climatic cycle, yielding the first numerical ages of a loess record from the middle Danube basin. Infrared-stimulated luminescence (IR-OSL) dating has been applied to the polymineral silt fraction using a multiple aliquot additive-dose protocol to determine the equivalent dose ( D E ). Within error limits, all age estimates are in stratigraphic order. Owing to the application of shine-plateau tests, the samples showed no evidence of insufficient bleaching. The Surduk loess section comprises three major periods of soil formation. Based on the IR-OSL chronostratigraphy, the lowermost pedocomplex is attributed to the Last Interglacial and to the Early Glacial (Marine Isotope Stage – MIS 5e to 5a). The middle part of the section exhibits a succession of weakly developed brown soils and a humic horizon, named 'Surduk soil', formed during MIS 3. On top of the section, recent soil formation is related to the Holocene. Thick loess deposits are preserved between these palaeosols and are attributed to the Lower and Upper Pleniglacials (MIS 4 and 2), respectively. Estimated mean sedimentation rates are 0.1–0.2 mm/yr for the last glacial cycle, with a strong increase to 0.6 mm/yr with onset of the Pleniglacial. 相似文献
15.
中国黄土研究新进展(一)黄土地层 总被引：39，自引：15，他引：39
本文扼要介绍最近几年中国黄土研究中的土壤地层学、磁性地层学、气候地层学、第四纪下界及海陆古气候对比等方面的新进展。根据新发现的黄土剖面,中国黄土中共可区分出37个土壤地层单位。中国黄土底界的古地磁年龄为2.5MaB.P.。2.5Ma以来,中国北方共经历了37次大的冷暖交替。2.5MaB.P.前后,全球气候出现了一次大的转型事件,它可作为第四纪的开始。中国黄土-古土壤系列同深海氧同位素记录在1.7Ma至今的时段上可以很好的对比;2.5Ma至1.7MaB.P.的气候变化,以黄土记录较为明确。 相似文献
16.
Thomas Stevens Slobodan B. Marković Michael Zech Ulrich Hambach Pal Sümegi 《Quaternary Science Reviews》2011,30(5-6):662-681
Loess in the Carpathian Basin is some of the thickest and most complete in Europe. Located in the Vojvodina region of the southern Carpathian Basin the Crvenka loess-palaeosol section appears to preserve a detailed climate proxy archive of the last glacial–interglacial cycle. Central to the interpretation of the site is a detailed and independent age model. Here, the results of detailed optically stimulated luminescence (OSL) dating and elevated temperature post-IR infrared stimulated luminescence (post-IR IRSL) dating are presented. Quartz OSL ages appear accurate to about 50–60 ka, where 2D0 values are reached, while elevated temperature post-IR IRSL yields more accurate ages below this. In line with recent results, the latter signal appears to show negligible fading rates. Two age models are developed that combine (a) OSL and post-IR IRSL ages and (b) OSL ages and ‘expected’ ages from tying unit boundaries to the marine record. If the luminescence model is regarded as accurate, differences between this and the OSL/marine age model raise questions over the accuracy of the latter, as well as the processes controlling the zeroing of luminescence dates. The luminescence based age model is then used to derive the first fully independent reconstruction of climate proxies and accumulation rates from Carpathian loess. Such reconstructions can be used to compare to other independent records without assumptions inherent in correlation-based approaches. The findings demonstrate how variable accumulation rate is at the site, and compared to other independently dated Carpathian loess records. Average values vary north–south but are of similar order throughout the basin. Accumulation rate was highest during the later part of the last glacial, but variation on millennial timescales does not always match shifts in grain-size, suggesting diverse and complex influences. Environmental reconstructions using grain-size and magnetic susceptibility show that no one atmospheric system or air mass can explain the changes in the Carpathian Basin and that millennial-scale variability can only intermittently be tied to North Atlantic Heinrich events. Expanded ice sheets during the peak last glacial, combined with other atmospheric teleconnections, may have served to develop a strong anticyclone in the region. It was likely windier during earlier parts of the last glacial, but Atlantic and Mediterranean moisture was probably less abundant than during more humid interglacials. 相似文献
17.
18.
作者将奇异谱分析(SSA)引入第四纪古气候变化研究中,收到了较好的效果。奇异谱分析是一种新的时间序列分析工具,它可形成一个单边(向前)滤波器,将原时间序列有效地分解成各个主成分,其滤波系数完全由数据本身决定。由奇异谱分析确定的统计维,给出动力维上界的估计,为非线性动力学研究打下基础。分析表明,在整个第四纪,宝鸡黄土粒度曲线的统计维为19,与深海钻孔V28-239氧同位素分析结果(=18)十分接近;各主成分在地球轨道几何参数各成分中大都能找到对应关系,但均不是线性响应关系;与偏心率、地轴倾斜度和岁差有关的成分分别占46、43和6％左右;其中第一主成分还揭示出与偏心率约0.4Ma周期对应的振荡仅在2.5—1.7和0.7—0.3Ma B.P.出现。 相似文献