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1.
A. M. Fetisova R. V. Veselovskiy Yu. P. Balabanov N. V. Sal’naya 《Izvestiya Physics of the Solid Earth》2017,53(5):635-644
One of the key challenges which are traditionally encountered in studying the paleomagnetism of terrigenous sedimentary strata is the necessity to allow for the effect of shallowing of paleomagnetic inclinations which takes place under the compaction of the sediment at the early stages of diagenesis and most clearly manifests itself in the case of midlatitude sedimentation. Traditionally, estimating the coefficient of inclination flattening (f) implies routine re-deposition experiments and studying their magnetic anisotropy (Kodama, 2012), which is not possible in every standard paleomagnetic laboratory. The Elongation–Inclination (E–I) statistical method for estimating the coefficient of inclination shallowing, which was recently suggested in (Tauxe and Kent, 2004), does not require the investigation of the rock material in a specially equipped laboratory but toughens the requirements on the paleomagnetic data and, primarily, regarding the volume of the data, which significantly restricts the possibilities of the post factum estimation and correction for inclination shallowing. In this work, we present the results of the paleomagnetic reinvestigation of the Puchezh and Zhukov ravine (ravine) reference sections of the Upper Permian and Lower Triassic rocks in the Middle Volga region. The obtained paleomagnetic data allowed us to estimate the coefficient of inclination shallowing f by the E–I method: for both sections, it is f = 0.9. This method was also used by us for the paleomagnetic data that were previously obtained for the Permian–Triassic rocks of the Monastyrskii ravine (Monastirskoje) section (Gialanella et al., 1997), where the inclination shallowing coefficient was estimated at f = 0.6. 相似文献
2.
本文报道青藏高原羌北地区中-晚侏罗世雁石坪群古地磁新结果.对采自青海省格尔木市唐古拉山乡雁石坪剖面(33.6°N, 92.1°E)11个灰岩采点(118块)和10个碎屑岩采点(99块)定向样品系统古地磁学研究表明,大部分样品的退磁曲线具有双分量特征.低温分量方向在地理坐标系下较为集中,应该为地层褶皱之后的黏滞剩磁.高温特征剩磁分量方向可分为两类:(1)索瓦组(J3s)和布曲组(J2b)灰岩,以磁铁矿为主要载磁矿物,高温特征剩磁分量(Ds=355.7°,Is=42.1°,k=58.2,α95=6°)可通过99%置信度的褶皱检验.(2)雪山组(J2x)和雀莫错组(J2q)碎屑岩,以赤铁矿、磁铁矿为主要载磁矿物,高温特征剩磁分量(Ds=3.3°,Is=28.9°,k=30.7,α95=8.9°)可通过95%置信度的倒转检验和99%置信度的褶皱检验.两组分量都应该是岩石形成时的原生剩磁信息.碎屑岩组的磁倾角比灰岩组偏低13°左右,其剩磁方向很可能存在着与压实作用相关的剩磁倾角变浅的状况.本文取灰岩组平均磁化方向作为雁石坪群的原生剩磁分量,获得羌北地区雁石坪群古磁极位置:80.0°N,295.2°E(dp/dm=7.4/4.5).古地磁结果表明,羌北-昌都地区晚石炭-晚二叠世期间位于南纬中低纬度地区,早三叠世以后开始大规模北向漂移,至中-晚侏罗世已到达24.3°N.其快速北向运动主要发生在早三叠至早侏罗世期间(3500 km左右),与现今位置相比中晚侏罗世之后的北向迁移总量为900 km左右. 相似文献
3.
An updated analysis of the global paleomagnetic database shows that the frequency distributions of paleomagnetic inclinations for the Cenozoic and Mesozoic eras (younger than 250 Ma) are compatible with a random geographical sampling of a time-averaged geomagnetic field that closely resembles that of a geocentric axial dipole. In contrast, the frequency distributions of paleomagnetic inclinations for the Paleozoic and Precambrian eras (prior to 250 Ma) are over-represented by shallow inclinations. After discounting obvious secondary causes for the bias, such as from data averaging, sedimentary inclination error, inhomogeneous lithological distributions, and tropical remagnetization, we show that the anomalous inclination distributions for the Paleozoic and Precambrian can be explained by a geomagnetic field source model which includes a relatively modest (25%) contribution to the axial dipole from a zonal octupole field and an arbitrary zonal quadrupolar contribution. The apparent change by around 250 Ma to a much more axial dipolar field geometry might be due to the stabilization of the geodynamo from growth of the inner core to some critical threshold size, a gross speculation which would imply that either the threshold size was rather large or the inner core nucleated rather late in Earth history. Alternatively, if a geocentric axial dipole model is assumed or can eventually be demonstrated independently, the anomalous inclination distributions for the Paleozoic and Precambrian may reflect a tendency of continental lithosphere to be cycled into the equatorial belt, perhaps because geoid highs associated with long-term continental aggregates influence true polar wander. 相似文献
4.
D. Kondopoulou S. Sen E. Aidona D.J.J. van Hinsbergen G. Koufos 《Journal of Geodynamics》2011,51(5):327-338
Superimposed on a regional pattern of oroclinal bending in the Aegean and west Anatolian regions, the coastal region of western Anatolia, shows a complex and chaotic pattern of coexisting clockwise and counterclockwise rotations. Here, we report new palaeomagnetic data from the eastern Aegean island of Chios, to test whether this fits the regional palaeomagnetic pattern associated with the Aegean orocline, or should be included in the narrow zone of chaotic palaeomagnetic directions. Therefore, a combined palaeomagnetic study of Miocene sediments and volcanic rocks has been carried out. Thermal and AF demagnetization of a 130-m thick Middle Miocene succession from the Michalos claypit allowed a stable component of both polarities to be isolated while rock magnetic experiments showed that the main magnetic carrier is magnetite. When compared with the Eurasian reference, the mean declination of 348 ± 5.1° implies 15° of counterclockwise rotation since Middle Miocene times. The obtained shallow inclination of 38 ± 6.7° was corrected to 61.8 ± 3.9°, by applying the elongation/inclination correction method for inclination shallowing. This result is similar to the expected inclination of 58° for the latitude of Chios. The palaeomagnetic analysis (demagnetization treatment and corresponding rock magnetic measurements) of the volcanic rocks identify a stable, predominantly normal, ChRM with poorly constrained mean declination of about 290 ± 19.8° based on five successfully resolved components. The significantly different palaeomagnetic results obtained from an island as small as Chios (and a very short distance), and the relatively large rotation amounts do not fit the regional palaeomagnetic direction of Lesbos and basins in northwestern Turkey which show little or no significant rotation. We thus prefer to include Chios in the coastal zone of chaotic rotations, which may represent a previously inferred tectonic transfer zone that accommodates lateral differences in extensional strain within the Aegean back-arc. 相似文献
5.
《Earth and Planetary Science Letters》2006,241(1-2):234-247
Ten sections of Neogene molasse-type sediments were sampled in the Guide Basin of northeastern Tibet for magnetostratigraphy [X.M. Fang, M.D. Yan, R. Van der Voo, D.R., Rea, C. Song, J.M. Parés, J. Gao, J. Nie, S. Dai, Late Cenozoic deformation and uplift of the NE Tibetan plateau: evidence from high resolution magnetostratigraphy of the Guide Basin, Qinghai Province, China, Geol. Soc. America Bull. 107 (2005) 1208–1225 [1]], but they also yield seven well-dated formation-mean directions that reveal changing declinations as rotations occurred in response to crustal deformation north of the India–Asia collision zone. Three formations are of early Miocene and Oligocene age, as indicated by fossils and magnetic reversal records, whereas four younger formations yield late Miocene and Pliocene ages. The dual-polarity magnetizations are typically antipodal, but reveal inclinations that are too shallow, most likely because of post-depositional inclination flattening. The late Miocene and younger directions show formation-mean declinations between 354° and 7°, whereas three early Miocene and late Oligocene mean declinations range from 31° to 44°. This indicates that a clockwise rotation of 25.1 ± 4.6° took place during the middle part of the Miocene (best estimate 11–17 Ma). No rotations appear to have occurred, during that time, in the Xining, Lanzhou, Linxia and Jingning basins (Longzhong Basin) to the northeast and east of the Guide Basin; however, a rotation of similar magnitude has been documented by Dupont-Nivet and colleagues for pre-Miocene (> 29 Ma) time in these areas. Collectively, these results show that the basins in NE Tibet have had independently evolving structural histories. 相似文献
6.
Abstract Neotectonic crustal deformation in central Japan near a triple-junction of plates is investigated on the basis of paleomagnetic data. The progressive thermal demagnetization test isolated characteristic remanent magnetization from 18 sites of the early Quaternary Eboshidake volcanic rocks erupted around the termination of active strike-slip faults. The site-mean directions show considerably large scatter in declinations, and easterly deflection in average (Dm = −161.7°). On the basis of inclination statistics, measured inclinations (Im = −48.9°, δI = 6.6°) are concordant with an expected value from latitude of the study area. Because the sampling was planned to cover a wide stratigraphic range and eliminate the effect of geomagnetic secular variation, an easterly deflection is attributed to clockwise rotation around vertical axis. Together with previous paleomagnetic data, the present study indicates that clockwise-rotated areas in central Japan are aligned on a northeast–southwest recent shear zone delineated through geodetic survey. Deflection and scatter of paleomagnetic declinations of the Eboshidake volcanic rocks are much greater than those extrapolated from a recent strain rate, and might be explained by complicated motion anticipated at fault terminations and/or enhanced crustal rotation under elevated temperatures around a Quaternary volcanic province. 相似文献
7.
对白令海北部陆坡B5-4孔进行了古地磁和岩石磁学研究,尝试获得该岩芯的地磁场相对强度和方向变化信息.结果表明:(1)除0~0.44 m沉积物的磁性矿物粒度比其余沉积物细以外,岩芯的磁学性质总体均一,其记录的地磁场相对强度可以与北大西洋ODP983孔相应记录进行高度对比.(2)根据B5-4孔与ODP983孔地磁场相对强度记录对比结果,并结合该孔4.54~4.56 m处有孔虫AMS14C测年结果,可以确定3个深度-年龄对比点,并据此初步建立了B5-4孔的年龄模型.(3)B5-4孔磁偏角和磁倾角记录与贝加尔湖、北美、欧洲全新世以来的记录和当地地磁场球谐模型结果一致,其对比点丰富了强度对比点年龄模型,揭示了14 cal ka B.P.以来近线性的沉积模式.(4)根据与中国东部陆架两个钻孔的磁倾角对比,我们推测B5-4孔9~14 ka之间两段浅化的磁倾角可能是哥德堡极性事件的记录,但是受到早期成岩或者沉积物平滑效应的影响.以上结果足以证明,地磁场相对强度和方向变化可以从适宜的白令海沉积物中获得,它可以为确定该海区沉积物年龄提供相关辅助信息,有助于解决北极、亚北极古环境和古海洋研究中由于有孔虫等钙质生物壳体缺乏导致的年龄信息匮乏问题. 相似文献
8.
Abstract Recent paleomagnetic studies are reviewed in an effort to clarify the relationship between the intra-arc deformation of central Japan and the collision tectonics of the Izu-Bonin Arc. The cusp structure of the pre-Neogene terranes of central Japan, called the Kanto Syntaxis, suggests a collisional origin with the Izu-Bonin Arc. The paleomagnetic results and newly obtained radiometric ages of the Kanto Mountains revealed the Miocene rotational history of the east wing of the Kanto Syntaxis. More than 90° clockwise rotation of the Kanto Mountains took place after deposition of the Miocene Chichibu Basin (planktonic foraminiferal zone of N.8: 16.6–15.2 Ma). After synthesizing the paleomagnetic data of the Japanese Islands and collision tectonics of central Japan, it appears that approximately a half rotation (40–50°) probably occurred at ca 15 Ma in association with the rapid rotation of Southwest Japan. The remainder (50-40°) continued until 6 Ma, resulting in the sharp bent structure of the pre-Neogene accretionary complexes (Kanto Syntaxis). The latter rotation seems to have been caused by the collision of the Izu-Bonin Arc on the northwestward migrating Philippine Sea Plate. 相似文献
9.
10.
运用主成分分离及线性区段等方法 ,使早白垩世样品明显分离出二组磁组分 .叠加剩磁为喜山期重磁化 ,特征剩磁明显偏离现代地磁场方向 ,经倾斜校正后 ,有很好的一致性并通过了倒转检验 ,给出塔里木地块库车坳陷早白垩世巴西盖组古地磁新数据 .综合已有的古地磁结果 ,获得了塔里木地块早白垩世平均剩磁方向及平均古地磁极 ,阐明了塔里木地块早白垩世磁倾角明显偏低这一现象 .分析导致磁倾角偏低的诸多因素 ,认为压实作用可能是导致磁倾角偏低的重要因素之一 . 相似文献
11.
Seven deep-sea sediment cores recovered in the central equatorial Pacific collectively span a magneto- and biostratigraphically determined age interval ranging from about 0.1 to 21 m.y. B.P. Measured values of paleomagnetic inclination and their systematic variation with depth in these cores denote relative motion between the central Pacific lithosphere and the magnetic field of the earth. Assuming that the position of the earth's dipole field remained essentially parallel to the present spin axis during the interval, the data provide evidence of a marked decrease in the northward rate of plate motion from about 11 cm/yr to about 6 cm/yr at approximately 12 m.y. B.P. This date of change of motion as well as the northward direction and overall average rate of about 8 cm/yr throughout the last 21 m.y., agree reasonably well with results of other studies of the tectonic history of the Pacific plate and ridge system. More significantly, however, these preliminary results demonstrate the usefulness of the paleomagnetic record in deep-sea sediment cores spanning sufficiently long intervals of time as an aid in reconstructing plate motions. 相似文献
12.
Niels Abrahamsen 《Studia Geophysica et Geodaetica》1992,36(1):26-41
Summary Three possible ways to explain the Caenozoically observed farsidedness of paleomagnetic poles (apart from lithospheric plate movements) are discussed: magnetic refraction, sediment compaction and dipole off-set. The dipole off-set, being a possible geomagnetic field property, will be of opposite sign on opposite hemispheres, and hence will not tend to smoothe out by sectorial averaging. Sediment compaction shallows the inclination on both hemispheres, and hence will tend to smoothe out by sectorial averaging, provided that sediment properties, site latitude coverage and number of investigations are equal (fairly unlikely).Magnetic refraction causes systematic directional distortions of the remanent magnetization in rocks of moderate to high magnetic intensity (or apparent susceptibility kapp=k(1+Q)) such as in many volcanics, some metamorphics, as well as in baked clays and slags, etc. A detailed discussion of this effect is given: If the kapp of the material is above 0.001 emu/cm
3
(×4 SI), this effect is likely to cause a significant palaeomagnetic refraction error of the NRM (typically a TRM or a CRM) of the rock. An apparent susceptibility of this order of magnitude is quite common in volcanic rocks; e.g. for oceanic floor basalts the average of kapp is about 0.02 emu/cm
3
corresponding to systematic errors (flattening) of some 3° to 6° in the inclination of a horizontal flow, depending on the latitude.To improve paleomagnetic results in general, a simple refraction correction is therefore suggested to be applied in the case of common two-dimensional (i.e. flat, elongated) geological bodies such as dykes, sills, lava flows and baked clays. Numerical solutions are given for the horizontal case, while a graphical solution is given for the general two-dimensional case.Being of systematic types, the refraction error together with the sediment compaction effect may be responsible for a major part of the observed farsidedness of the Caenozoic palaeomagnetic pole positions, the apparent farsidedness not yet beeing masked by the scatter of pole positions produced by older individual lithospheric plate movements.Presented at 2nd conference on New Trends in Geomagnetism, Castle of Bechyn, Czechoslovakia, September 24–29, 1990. 相似文献
13.
Yoram Eckstein 《Pure and Applied Geophysics》1978,117(1-2):150-159
Heat flow data from the eastern Mediterranean region indicates an extensive area of low heat flow, spreading over the whole basin of the Mediterranean east of Crete (Levantine Sea), Cyprus, and northern Egypt. The average of the marine heat flow measurements in the Levantine Sea is 25.7±8.4 mW/m2, and the heat flow on Cyprus is 28.0±8.0 mW/m2. The estimated values of heat flow in northern Egypt range from 38.3±7.0 to 49.9±9.3 mW/m2, apparently with no consistent trend. To the east, on the coast of Israel, the heat flow values increase, ranging from 36.6±22.4 to 56.7±14.2 mW/m2 along a SSE trend. The trend apparently correlates with an increase in crustal thickness, which is about 23 km at the north-west base of the Nile-Delta-cone, and close to 40 km beneath Israel.Contribution No. 157, Department of Geology, Kent State University, Kent, Ohio, USA. 相似文献
14.
Paleomagnetic constraints on the tectonic history of the major blocks of China duing the Phanerozoic
Zhu Rixiang Yang Zhenyu Wu Hanning Ma Xinghua Huang Baochun Meng Zifang Fang Dajun 《中国科学D辑(英文版)》1998,41(2):1-19
Paleomagnetic study of China and its constraints on Asia tectonics has been a hot spot. Some new paleomagnetic data from three major blocks of China. North China Block (NCB), Yangtze Block (YZB) and Tarim Block (TRM) are first reported, and then available published Phanerozoic paleomagnetic poles from these blocks with the goal of placing constraints on the drift history and paleocontinental reconstruction are critically reviewed. It was found that all three major blocks were located at the mid-low latitude in the Southern Hemisphere during the Early Paleozoic. The NCB was probably independent in terms of dynamics. its drift history was dominant by latitudinal placement accompanying rotation in the Early Paleozoic. The YZB was close to Gondwanaland in Cambrian, and separated from Gondwanaland during the Late-Middle Ordovician. The TRM was part of Gondwanaland, and might be close to the YZB and Australia in the Early Paleozoic. Paleomagnetic data show that the TRM was separated from Gondwanaland during the Late-Middle Ordovician, and then drifted northward. The TRM was sutured to Siberia and Kazakstan blocks during the Permian, however, the composite Mongolia-NCB block did not collide with Siberia till Late Jurassic. During Late Permian to Late Triassic, the NCB and YZB were characterized by northern latitudinal placement and rotation on the pivot in the Dabie area. The NCB and YZB collided first in the eastern part where they were located at northern latitude of about 6°—8°, and a triangular oceanic basin remained in the Late Permian. The suturing zone was located at northern latitude of 25° where the two blocks collided at the western part in the Late Triassic. The collision between the two blocks propagated westward after the YZB rotated about 70° relative to the NCB during the Late Permian to Middle Jurassic. Then two blocks were northward drifting (about 5°) together with relative rotating and crust shortening. It was such scissors-like collision procedure that produced intensive compression in the eastern part of suturing zone between the NCB and YZB, in which continental crust subducted into the upper mantle in the Late Permian, and then the ultrahigh-pressure rocks extruded in the Late Triassic. Paleomagnetic data also indicate that three major blocks have been together clockwise rotating about 20° relative to present-day rotation axis since the Late Jurassic. It was proposed that Lahsa Block and India subcontinent successively northward subducted and collided with Eurasia or collision between Pacific/Philippines plates and Eurasia might be responsible for this clockwise rotating of Chinese continent. 相似文献
15.
Jose Rosas-Elguera Bertha Aguilar Reyes Avto Goguitchaichvili Macario Rocha Margarita López Martínez Miriam M. Tostado-Plascencia Luis M. Alva Valdivia Cecilia Caballero Miranda 《Studia Geophysica et Geodaetica》2011,55(2):265-278
For long time the western-central Mexico has been affected by oblique subduction caused by Farallon plate beneath North America.
As result, smaller plates (e.g. Cocos Plate), several fault systems outlining crustal blocks (e.g. Michoacán block) and magmatic
arcs (e.g. Paleocene-Early Oligocene magmatism and the Trans-Mexican Volcanic Belt) were developed. Still, no paleomagnetic
data are available for Oligocene and Miocene. The principal aim of this study is to evaluate whether the tectonic rotations
and relative motions of these blocks occurred before the Miocene. Here, we report a detailed rock-magnetic and paleomagnetic
results from Tecalitlan area, located in the Michoacán block. Sixteen sites (about 150 oriented samples) were collected including
one radiometrically dated diabase dike (35.0 ± 1.8 Ma). Rock-magnetic experiments permitted identification of magnetic carriers
and assessment of the paleomagnetic stability. Continuous susceptibility measurements vs temperature in most cases yield reasonably
reversible curves with Curie points close to that of magnetite. Reliable paleomagnetic directions were obtained for 12 sites.
Inclination I and declination D of the mean paleomagnetic direction obtained in this study are I = 33.1°, D = 345.0°, and
Fisherian statistical parameters are k = 25, α95 = 8.9°. The corresponding mean paleomagnetic pole position is Plat = 75.7°, Plong = 166.6°, K = 31, A95 = 8.0°. The mean inclination is in reasonably good agreement with the expected value, as derived from reference poles for
the stable North America. Magnetic declination is not significantly different from that expected which is in disagreement
with a counterclockwise tectonic rotation of about 20° previously reported for the studied area. Based on paleomagnetic results
obtained in this study compiled with those currently available from the Michoacán Block, we propose a simple model suggesting
that sometime in Eocene epoch the convergence vector of the Farallon plate relative to North America plate was normal to the
trench before reaching an actual oblique convergence. 相似文献
16.
The western boundary current in the southern South China Sea (SCS) in summer does not always flow northward along the Indo-China Peninsula, it leaves the southeast coast of peninsula around 10–14°N, forming a strong eastward jet called “Vietnam Coastal Current” or “Southeast Vietnam Offshore Current” (SVOC). It is known that the wind stress curl is the major driving factor responsible for this current. In this paper, we carry on the study of the separation position, strength and forming time of this current. A connected single-layer/two-layer model is employed here to study these problems. According to the numerical experiments and analyses of the vorticity dynamics, it is found that, the local wind stress curl (including the northern cyclonic and the southern anticyclonic wind forcing curl), the nonlinear term, the topographic effect, the planetary vorticity advection and the water exchange between the SCS and Java Sea via the Sunda Shelf have an important effect on both the position where this current leaves the coast and its strength; when there is an inflow via the Sunda Shelf, the current is stronger and the separation position is more northward; whereas the water stratification, the coastline and the inflow of Kuroshio have little effect on its separation. In fact, two opposite flowing currents, the northward SVOC and the southward western branch of the cyclonic eddy to its north near the Indo-China Peninsula, collide with each other, and the strength of these two currents determine the separation position of the SVOC. Origin of the SVOC may be driven by the local negative wind stress curl in the middle SCS in mid-spring, this current flows along the coast of the Indo-China Peninsula and leaves the coast at high latitude, flowing northeastward; once the local positive wind stress curl near the northern Indo-China Peninsula or the negative one near the southern Indo-China Peninsula is large enough, this current will begin to leave the coast at low latitude. 相似文献
17.
HUANG Baochun WANG Yongcheng &ZHU Rixiang Institute of Geology Geophysics Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2004,47(6):540-550
~~New paleomagnetic and magnetic fabric results for Early Cretaceous rocks from the Turpan intramontane basin,east Tianshan,northwest China~~ 相似文献
18.
对四川盆地东北部巴中地区和西部雅安地区早白垩世红层分别采集9块手标本,进行了详细的古地磁学研究.系统退磁获得两地的特征剩磁,其中巴中地区平均方向为,倾斜校正之前:D_g/I_g=25.3°/19.0°,k=18.6,α_(95)=8.8°;倾斜校正之后:D_s/I_s=25.8°/18.9°,k=24.3,α_(95)=7.6°.雅安地区平均方向为,倾斜校正之前:D_g/I_g=24.5°/45.0°,k=15.7,α_(95)=9.0°;倾斜校正之后:D_s/I_s=356.7°/35.6°,k=28.5,α_(95)=6.6°.磁化率各向异性实验结果显示两地均未受到显著的构造应力影响.等温剩磁各向异性(AIR)实验结果,巴中地区IRMz/IRMLx平均值为0.8194,表明18%的压实率;雅安地区IRMz/IRMx平均值为0.8909,表明11%的压实率,计算得到巴中和雅安地区校正后的磁倾角分别为22.7°和38.8°.根据等温剩磁各向异性(AIR)实验和Tauxe and Kent(2004)提出的EI校正法得到的结果表明,四川盆地早白垩世陆相碎屑岩层中存在沉积压实作用造成的磁倾角偏低现象,而且川东北巴中地区的偏低程度强于川西雅安地区. 相似文献
19.
本文提出了一种全张量磁梯度数据的斜导数边界识别方法,该方法利用全张量磁梯度数据定义了北向斜导数、东向斜导数和垂向斜导数.模型试验表明,北向和东向斜导数无法有效识别磁性异常体边界,异常形态复杂虚假异常较多,而垂向斜导数在高纬度斜磁化或者垂直磁化条件下可以清晰而准确得识别地质体的边界,具有一定的深度识别能力.与现有磁张量梯度的边界识别方法相比,识别效果好,可以有效均衡不同深度地质体的响应.将上述方法应用于大兴安岭地区实测航磁三分量数据转换得到的全张量数据,获得了研究区浅部磁性体的分布,并与三分量数据进行联合解释,取得良好的地质效果. 相似文献
20.
Henry C. Halls 《Earth and Planetary Science Letters》1991,105(1-3)
Consistent age relationships between oppositely magnetized dykes of the 2.45 Ga Matachewan dyke swarm suggest that only a single magnetic field reversal occurred during the period of igneous activity. The magnetic field throughout most of this time was characterized by a SSW declination and shallow negative inclination but reversed toward the waning stages of magmatism. The new paleomagnetic data provide the oldest known magnetic reversal for which the relative reversal sense is known. 相似文献