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1.
本文概述了国内外布莱克负向极性幕的研究历史与现状，报导了许家窑旧石器遗址上更新统湖相剖面布容正向极性时（带）中负向极性段的位置、时间及剩磁特征。根据剖面上铀子系法测定的年代值和该负向的转换性质，笔者确认该负向极性段时间上对应于布莱克负向极性幕。 相似文献
2.
泥河湾层磁性地层学研究回顾 总被引：7，自引：4，他引：3
泥河湾盆地以富含哺乳动物化石和古人类遗址而引起了古人类学家和地贡学家的广泛关注,泥河湾层是该盆地中发育的一套晚新生代河湖相沉积物．磁性地层学研究结果表明泥河湾层的形成始于高斯正极性世,经历了松山反向极性世,结束于布容正极性世．本文回顾了针时泥河湾层的磁性地层学研究工作,选取了小长梁、东谷坨、郝家台、洞沟、红崖、虎头粱及许家窑等七个剖面作详细介绍,并进行了横向时比． 相似文献
3.
本文报道由蓝田、陕县、洛川、西峰、平凉、兰州及靖远等剖面获得的古地磁研究结果．主要结论为：１．中国黄土剖面记录了Ｂｒｕｎｈｅｓ正极性带与Ｍａｔｕｙａｍａ负极性带，Ｂｒｕｎｈｅｓ／Ｍａｔｕｙａｍａ极性转换过程位于第８层黄土（Ｌ８）．在段家坡黄土剖面该转换过程对应的地层厚度为０．３７５ｍ，持续时间约６０００ａ．转换过程由３次极性变化构成，每次经历的时间约为４００ａ．２．Ｊａｒａｍｉｌｌｏ正极性亚带（Ｊ）位于标志层Ｌ９至Ｌ１５之间，大约Ｓ１０－Ｓ１３位置．３．Ｏｌｄｕｖａｉ正极性亚带（Ｏ）对应的地层为Ｓ２７－Ｓ３３４．Ｒｅｕｎｉｏｎ正极性亚带（Ｒ）由两部分组成，在蓝田段家坡黄土剖面分别位于Ｌ３６和Ｓ３８５．Ｍａｔｕｙａｍａ负极性带与Ｇａｕｓｓ正极性带界限（Ｍ／Ｇａ）位于黄土和红色粘土交界处，中国黄土的底界年龄为２．４８Ｍａ左右．黄土与红色粘土为整合接触关系．６．黄土下伏的红色粘土记录了Ｇａｕｓｓ正极性带，Ｇｉｌｂｅｒｔ负极性带和古地磁年表编号５（Ｅｐｏｃｈ５）． 相似文献
4.
《华北地震科学》2018,(4)
依据盆地第四系沉积特点,结合高密度、CSAMT(可控源音频大地电磁)、浅层地震及钻孔磁化率探测结果,剖析隐伏断裂在盆地的几何形态特征及活动性。结果表明:延矾盆地北缘断裂南段(隐伏端)沿窑湾村-桑园南堡村展布,由2条SE倾的阶梯状正断层组成,切割第四系上更新统泥河湾组地层,上断点埋深40m,断距约35m;断裂在早-中更新世有过活动,晚更新世断裂活动性较强,全新世以后断裂活动性具逐渐减弱趋势;施庄断裂北隐伏段经施庄向SE145°方向展布,切割第四系泥河湾组地层,上断点埋深70m,断裂早-中更新世有过活动,晚更新世断裂活动性较强。综合分析认为,延怀盆地隐伏断裂在晚更新世时期活动性强,而全新世以来,各断裂活动性减弱。 相似文献
5.
选择伊朗中部、南部及西北部地区的近２０条晚元古代－早古生代完整地层剖面，系统采集Ｓｏｌｔａｎｉｅｈ组、Ｂａｒｕｔ组、Ｚａｉｇｕｎ组、Ｌａｌｕｎ组及Ｍｉｌａ组古地磁样品９６０件．经测试和对比获得结论：Ｓｏｌｔａｎｉｅｈ组记录的地磁极性带为反向，Ｂａｒｕｔ组－Ｌａｌｕｎ组为正向，Ｍｉｌａ组又为反向．此成果完全可与国际地质科学联合会（ＩＵＯＳ）１９８９年建立的全球地层极性柱中相应时代的极性带对比．计算得出５个地层组的古地磁南极位置．古地磁研究表明，晚元古代－早古生代伊朗全境均属稳定地块，处于赤道南侧约１６°的低纬度区．此期间似无大幅度转动和纬度变化． 相似文献
6.
本文对陇中盆地会宁含小哺乳动物化石的关公滩剖面河湖相沉积序列进行了详细的岩石磁学和磁性地层学研究，磁化率各向异性结果表明关公滩剖面沉积物记录了典型的原生沉积组构，沉积物沉积以后几乎没有受到后期的扰动.最大磁化率主轴方向与现今的古水流流向基本一致，表明区域西高东低的地貌至少在中更新世早期已经形成.磁滞回线、等温剩磁获得曲线的矫顽力谱分析、三轴等温剩磁退磁曲线等岩石磁学结果显示：关公滩剖面河湖相沉积物的磁性矿物有磁铁矿、磁赤铁矿和赤铁矿，其中磁铁矿和赤铁矿是主要的剩磁载体，但其特征剩磁载体以赤铁矿为主.系统退磁结果显示，在大部分样品中，磁铁矿和赤铁矿均记录了几乎相同的特征剩磁的方向，整个剖面呈现单一的正极性.另外，关公滩剖面底部河湖相沉积物中产出丰富的小哺乳动物牙齿化石，经初步研究包括复齿鼠兔（Ochotonoides complicidens）、丁氏鼢鼠（Myospalax tingi）、方氏鼢鼠（Myospalax fontanieri）、变异仓鼠（Cricetinus varians）、大林姬鼠（Cricetinus varians）、复齿旱獭（Marmota complicidens）等六个种类，其中丁氏鼢鼠和复齿鼠兔是相对原始的种类，其时代跨越早更新世至中更新世早期，其他都是我国北方中、晚更新世常见的种类，该小哺乳动物化石组合性质表明其时代很可能为中更新世早期.因此，综合磁性地层学和小哺乳动物生物年代学结果，关公滩剖面记录了布容正极性时的沉积，剖面底部堆积及其哺乳动物群的时代应为中更新世早期. 相似文献
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8.
雷琼地区火山岩的钾-氩同位素年龄测定和古地磁极性研究表明,新生代在该地区的岩浆活动一直很强烈。火山岩的生成年代不晚于中新世晚期,至更新世岩浆活动尤为强烈。 研究也表明中新世晚期以来这里的地球磁场极性变化规律与近期发表的地磁极性年表大体相符,并肯定了数个尚有争议的短期极性事件的存在。年代为0.58±0.13Ma的反极性火山岩的资料肯定了安比拉（Emperor）事件的存在。研究还证实了布容/松山极性时界线之下和哈拉米洛极性亚时之上有一短期的极性事件,其年代约为0.78±0.03Ma.在奥尔都维和哈拉米洛极性亚时之间存在有另一正极性事件,这可能相当于吉尔萨（Gilsa）事件。 相似文献
9.
《中国科学:地球科学》2015,(10)
记述了最近采自泥河湾早更新世地层中的真马化石,新发现完全证实了中国学者对黄河马Equus huanghoensis的合理推断.主要材料包括:一件包括完整的上下齿列的比较完整的雄性个体头骨及其下颌骨标本,一件雌性个体头骨残部连带下颌残部;另有一件属于Equus未定种的第三掌骨材料.化石采自泥河湾扬水站剖面,时代为1.6 Ma的更新世早期.黄河马新材料除验证早先定种的牙齿较大、原尖较短、原脊、后脊倾斜等部分特征以外,还展示出头骨长大、枕孔上隆发育、五边形枕面、马刺很弱、褶皱简单等一系列与其他马类有显著区别的新特点.第三掌骨材料经对比与产自甘肃庆阳的庆阳马的特征较为接近. 相似文献
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The International Geomagnetic Reference Field models (IGRF) for 1900–2000 are used to calculate the geomagnetic field distribution
in the Earth’ interior from the ground surface to the core-mantle boundary (CMB) under the assumption of insulated mantle.
Four reversed polarity patches, as one of the most important features of the CMB field, are revealed. Two patches with +Z
polarity (downward) at the southern African and the southern American regions stand out against the background of ™Z polarity
(upward) in the southern hemisphere, and two patches of ™Z polarity at the North Polar and the northern Pacific regions stand
out against the +Z background in the northern hemisphere. During the 1900–2000 period the southern African (SAF) patch has
quickly drifted westward at a speed of 0.20–.3° /a; meanwhile its area has expanded 5 times, and the magnetic flux crossing
the area has intensified 30 times. On the other hand, other three patches show little if any change during this 100-year period.
Extending upward, each of the reversed polarity patches at the CMB forms a chimney-shaped “reversed polarity column” in the
mantle with the bottom at the CMB. The height of the SAF column has grown rapidly from 200km in 1900 to 900km in 2000. If
the column grows steadily at the same rate in the future, its top will reach to the ground surface in 600–700 years. And then
a reversed polarity patch will be observed at the Earth’s surface, which will be an indicator of the beginning of a magnetic
field reversal. On the basis of this study, one can describe the process of a geomagnetic polarity reversal, the polarity
reversal may be observed firstly in one or several local regions; then the areas of these regions expand, and at the same
time, other new reversed polarity regions may appear. Thus several poles may exist during a polarity reversal. 相似文献
12.
TianShui Yang Masayuki Hyodo ZhenYu Yang ShiHong Zhang Toshiaki Mishima HuaiChun Wu HaiYan Li Yi Li XingAn Shi Kan Wang YiMing Ma 《中国科学:地球科学(英文版)》2014,57(8):1929-1943
Paleomagnetic records of the Gauss-Matuyama reversal were obtained from two loess sections at Baoji on the Chinese Loess Plateau. Stepwise thermal demagnetization shows two obvious magnetization components. A low-temperature component isolated between 100 and 200–250°C is close to the present geomagnetic field direction, and a high-temperature component isolated above 200–250°C reveals clearly normal, reversed, and transitional polarities. Magnetostratigraphic results of both sections indicated that the Gauss-Matuyama reversal consists of a high-frequency polarity fluctuation zone, but the characteristic remanent magnetization directions during the reversal are clearly inconsistent. Rock magnetic experiments demonstrated that for all the specimens with normal, reversed, and transitional polarities magnetite and hematite are the main magnetic carriers. Anisotropy of magnetic susceptibility indicates that the studied loess sediments have a primary sedimentary fabric. Based on virtual geomagnetic pole latitudes, the Gauss-Matuyama reversal records in the two sections are accompanied by 14 short-lived geomagnetic episodes (15 rapid polarity swings) and 12 short-lived geomagnetic episodes (13 rapid polarity swings), respectively. Our new records, together with previous ones from lacustrine, marine, and aeolian deposits, suggest that high-frequency polarity swings coexist with the Gauss-Matuyama reversal, and that the Gauss-Matuyama reversal may have taken more than 11 kyr to complete. However, we need more detailed analyses of sections across polarity swings during reversals as well as more high-resolution reversal records to understand geomagnetic behavior and inconsistent characteristic remanent magnetization directions during polarity reversals. 相似文献
13.
We present the results of a complex (paleomagnetic, geological-stratigraphic, and paleontological) study of reference sections of Oligocene-Miocene deposits in the Kompasskii Bor tract on the Tym River in the eastern part of the western Siberian plate. Three sections of the Kompasskii Bor tract are studied: Belyi Yar (200-m mark), Belyi Yar (300-m mark), and Dunaevskii Yar (200-m mark). A composite magnetostratigraphic section of deposits, including the Oligocene-Miocene boundary dated at 23.8 Ma, is compiled with allowance for the complex data. Two magnetozones (of normal and reversed polarities) are identified in this section. The scale of magnetic polarity of the Cenozoic of the western Siberian plate at the Oligocene-Miocene boundary is determined in greater detail. The time interval of the upper part of the Zhuravka series (Chattian) and the Lyamin layers of the Abrosimov series (Aquitanian) is 24.6-22.9 Ma. 相似文献
14.
Günther Kletetschka 《Studia Geophysica et Geodaetica》1992,36(3):230-239
Summary The paper deals with the statistical approach to processing the polarity durations of the Earth's magnetic dipole over the past 170 million years. Partial elimination of the random component enables the mutual relation between normal and reversed polarities to be determined. The polarity time sequence has further been divided into several intervals. The frequency distributions for normal and reversed polarities have been established for each of these intervals. It has been found that the random component of the reversal triggering mechanism hides a pattern of behaviour which displays a certain amount of logic. 相似文献
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O.K.Chedia 《内陆地震》1994,(2)
ＲＥＣＥＮＴＵＮＤＥＲＴＨＲＵＳＴＳＯＦＴＩＡＮＳＨＡＮＡＮＤＰＯＳＳＩＢＬＥＭＥＣＨＡＮＩＳＭＯＦＴＨＥＩＲＯＲＩＧＩＮ￥Ｏ．Ｋ．Ｃｈｅｄｉａ（ＩｎｓｔｉｔｕｔｅｏｆＳｅｉｓｍｏｌｏｇｙＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅｓＲｅｐｕｂｌｉｃｏｆＫｉｒｇ... 相似文献
17.
A thin-walled steel tube/bamboo plywood composite hollow column with binding bars (SBCCB) was developed using transverse binding bars to reinforce a thin-walled steel tube and bamboo plywood composite hollow column. Low reversed cyclic loading tests were performed on 9 SBCCB specimens to observe the damage process and morphology in the SBCCBs. The effects of the slenderness ratio, the net cross-sectional area of the bamboo plywood, the assembly patterns of the cross sections, and the binding bars on the stress and seismic performance were investigated. The results show that the main failure modes of the SBCCBs were cracking of different adhesion interfaces at the base of the column and fracturing of the bamboo plywood. The cross-sectional assembly pattern has a significant effect on the failure modes; increasing the cross-sectional area and the slenderness ratio of the composite column will dramatically improve the seismic performance of the SBCCBs. SBCCBs have excellent elastic deformation and seismic energy consumption characteristics. The binding bars ensure the integrity of the specimen and inhibit the failure of the adhesion interface at the base of the column. Finally, based on the measurement of the axial pressure and the stress-strain curve within elastic range of the composite columns, a simplified mechanical model and a calculation method for bearing capacity was formulated. The calculation values of bearing capacity agree well with the experimental ones, and calculation method can be used to provide guidance for engineering applications of a SBCCB. 相似文献
18.
Magnetizations in 24 flows of Tertiary age in Israel indicate two stable directions, each of which has both normal and reversed polarities. AF demagnetization decreases the scatter of the NRM results. Typical Tertiary poles are near 70°N 110°W and another set of anomalous poles are near 34°N 50°W. These are similar to other reported Tertiary and Cretaceous poles. 相似文献
19.
Manuel Calvo-Rathert Bertha Aguilar Reyes Avto Goguitchaichvili José Rosas Elguera Héctor Franco Juan Morales Ruth Soto Ángel Carrancho Hugo Delgado 《Studia Geophysica et Geodaetica》2013,57(2):309-331
A rock-magnetic and paleomagnetic investigation was carried out on eleven Pleistocene and Pliocene 40Ar/39Ar dated lava flows from the Tepic-Zacoalco rift region in the western sector of the Trans-Mexican Volcanic Belt (TMVB) with the aim of obtaining new paleomagnetic data from the study region and information about the Earth’s magnetic field recorded in these rocks. Rock-magnetic experiments including measurement of thermomagnetic curves, hysteresis parameters and isothermal remanence acquisition curves were carried out to find out the carriers of remanent magnetisation and to determine their domain structure. Although some samples were characterised by the presence of a single ferromagnetic phase (magnetite), in most cases more phases were observed. Analysis of hysteresis parameters showed a mixture of single domain and multidomain particles, the fraction of the latter varying between 40% and 80%. Paleomagnetic results were obtained in all sites, although in 7 sites characteristic remanence directions and remagnetisation circles had to be combined in order to calculate site means. The six Pliocene sites not showing intermediate polarity yielded a paleomagnetic pole (latitude ? = 81.1°, longitude λ = 94.3°) which roughly agrees with the expected one. Paleomagnetic directions do not indicate significant vertical-axis block rotations in the western TMVB area. Reversed polarities observed can be correlated to the Gilbert chron, normal polarities to the Gauss chron or the Brunhes chron and intermediate polarities to the Cochiti-Gilbert or the Gilbert-Gauss transition. The reversed or intermediate polarity magnetisation recorded in one of the sites (542 ± 24 ka) corresponds either to the West Eifel 4 or the West Eifel 5 excursion, while the reversed polarity observed in the other site (220 ± 36 ka) very likely provides new evidence for the Pringle Falls excursion or the event recorded in the Mamaku ignimbrite. 相似文献
20.
1997年11月8日西藏玛尼79级地震发生在羌塘盆地北缘.本文利用LANDSAT影像，研究地震的地质构造背景，研究表明玛尼79级地震发生在NEE向玛尔盖茶卡—若拉错断裂带上，这是一条全新世明显活动的地壳深断裂.利用CBERS_1影像，研究地震地表破裂带的几何特征，100000分之一CBERS_1影像上由地震裂缝、地震陡坎和断塞塘组合显示的线性影像清楚地反映出地震地表主破裂带的形迹，可有效地进行破裂带的分段和长度量测.结果表明玛尼79级地震形成的地震地表主破裂带西起羌塘盆地北缘，绥加山南麓的白雪湖湖积平原上，向东延伸到双端湖西岸，长110km，走向N70 80°E.可分为白雪湖—玛尔盖茶卡、玛尔盖茶卡—朝阳湖、朝阳湖—双端湖３段.多时相MSS、TM影像分析表明，1997年玛尼79级地震是先存地震地表破裂带再次破裂的结果. 相似文献