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1.
Fuson (1969), see also Carlson (1975), claims that Olmécs and Maya knew and used a (lodestone) compass for the orientation
of pyramids, ceremonial and other important buildings, thousand years before Chinese. This hypothesis is tested here with
the aid of the new data, namely by comparison of paleomagnetic declinations for that time and area (Korte and Bőhnel, 2005),
with orientation data of buildings based also on our measurements at many archaeological localities of México, Guatemala,
and in Copán in Honduras by GPS and with a precise compass. After eliminating known astronomical and calendar orientation
of some structures, we have found that there is majority of structures with an orientation that clearly deviates from geographic
north (pole of rotation of the Earth). When trying to explain this, we can rule out pure chance, local topography, aesthetic,
meteorological or defense reasons. Thus, the Fuson hypothesis can still explain the observed site layout and building orientations.
But more accurate and extensive information mainly from paleomagnetism and archaeology is needed to reject or accept the hypothesis.
A proof of knowledge of a compass in Mesoamerica prior to Chinese would be important for our understanding history of the
ancient world.
jklokocn@asu.cas.cz
kost@fsv.cvut.cz
ttc.praha@iol.cz 相似文献
2.
Lower Cretaceous red sedimentary rocks from the depositional basin of East Qilian fold belt have been collected for a paleomagnetic study. Stepwise thermal demagnetization reveals two or three components of magnetization from dark red sandstones. Low-temperature magnetic component is consistent with the present Earth Field direction in geographic coordinates. High-temperature magnetic components are mainly carried by hematite. The mean pole of 19 sites for high-temperature magnetic components after tilt-correction is λ=62.2°N, φ=193.4°E, A95=3.2°, and it passes fold tests at 99% confidence level and reversal tests at 95% confidence level. The paleopole is insignificantly different from that of Halim et al. (1998) from the same sampling area at the 95% confidence level. Compared with paleomagnetic results for North China, South China, and Eurasia, our results suggest that no significant relative latitudinal displacement has taken place between Lanzhou region and these blocks since Cretaceous time. Remarkably, the pole of Lanzhou shows a 20° clockwise rotation with respect to those of North China, South China, and Eurasia. Geological information indicates that the crustal shortening in the western part of Qilian is greater than that in eastern part. In this case, the clockwise rotation of sampling area was related to India/Eurasia collision, and this collision resulted in a left-lateral strike-slip motion of the Altun fault in north Tibetan Plateau after the Cretaceous. 相似文献
3.
Mabel Mena Avto Goguitchaichvili Miguel Cervantes Solano Juan Francisco Vilas 《Studia Geophysica et Geodaetica》2011,55(2):279-309
The Early Cretaceous may be considered a key period for understanding the evolution of the Earth’s magnetic field. Some still
unsolved problems are related to the mode of paleosecular variation (PSV) of the Earth’s magnetic field before and during
the Cretaceous Normal Superchron. We report here a detailed rock-magnetic, paleomagnetic and paleointensity investigation
from 28 lava flows (331 standard paleomagnetic cores) collected in the Argentinean part of the Parana Flood Basalts (Formation
Posadas) in order to contribute to the study of PSV during the early Cretaceous and to obtain precise Cretaceous paleomagnetic
pole positions for stable South America. The average paleofield direction is precisely determined from 26 sites, which show
small within-site dispersion and high directional stability. Five sites show evidences for the self-reversal of thermoremanent
magnetization. 23 sites yielded normal polarity magnetization and only 3 are reversely magnetized. Moving windows averages
were used to analyze the sequential variation of virtual geomagnetic pole’s (VGP) axial positions. Interestingly, the axial
average VGP path traces an almost complete cycle around the geographical pole and passes near the location of all previously
published Paraná Magmatic Province poles. Both paleomagnetic poles and average VGP paths are significantly different from
the pole position suggested by fixed hotspot reconstructions, which may be due to true polar wander or the hotspot motion
itself. Only 15 samples from 5 individual basaltic lava flows, yielded acceptable paleointensity estimates. The site mean
paleointensities range from 25.2 ± 2.2 to 44.0 ± 2.2 μT. The virtual dipole moments (VDMs) range from 4.8 to 9.9 × 1022 Am2. This correspond to a mean value of 7.7 ± 2.1 × 1022 Am2 which is 96% of the present day geomagnetic field strength. These intensities agree with the relatively high values already
reported for Early Cretaceous, which are consistent with some inferences from computer simulations previously published. 相似文献
4.
Miguel Cervantes Solano Avto Goguitchaichvili Leda Sánchez Bettucci Ruben Cejudo Ruiz Manuel Calvo-Rathert Vicente Carlos Ruiz-Martinez Ruth Soto Luis M. Alva-Valdivia 《Studia Geophysica et Geodaetica》2010,54(4):533-546
We report detailed rock-magnetic and paleomagnetic directional data from 35 lava flows (302 standard paleomagnetic cores)
sampled in the Central-Northern region of Uruguay in order to contribute to the study of the paleosecular variation of the
Earth’s magnetic field during early Cretaceous and to obtain precise Cretaceous paleomagnetic pole positions for stable South
America. The average unit direction is rather precisely determined from 29 out of 35 sites. All A95 confidence angles are less than 8°, which points to small within-site dispersion and high directional stability. Normal polarity
magnetizations are revealed for 19 sites and 10 are reversely magnetized. Two other sites yield well defined intermediate
polarities. The mean direction, supported by a positive reversal test is in reasonably good agreement with the expected paleodirection
for Early Cretaceous stable South America and in disagreement with a 10° clockwise rotation found in the previous studies.
On the other hand, paleomagnetic poles are significantly different from the pole position suggested by hotspot reconstructions,
which may be due to true polar wander or the hotspot motion. Our data suggest a different style of secular variation during
(and just before) the Cretaceous Normal Superchron and the last 5 Ma, supporting a link between paleosecular variation and
reversal frequency. 相似文献
5.
William W. Sager 《Earth and Planetary Science Letters》1983,63(3):408-422
Seamount magnetic anomaly inversions as well as DSDP paleomagnetic and equatorial sediment facies data constrain a paleomagnetic pole for the Pacific plate of Late Eocene age. The location of the pole at 77.5°N, 21.2°E implies 12.5 ± 1.6° of apparent polar wander for the Pacific plate during the last 41 ± 5 m.y. The Late Eocene pole is significantly different from the Pacific Maastrichtian pole at the 95% confidence level and indicates 7.2° of apparent polar motion of the Pacific between 69 and 41 m.y. B.P. The data source locations for the Late Eocene pole are scattered over a large area of the North Pacific and thus the consistency of the data supports the hypothesis that the north central Pacific plate has been rigid since the Eocene. The agreement of the Late Eocene pole with the motion predicted for the Pacific from hotspot models suggests that relative motion between the spin axis and hotspots has been small since that time. Additionally, this finding dictates that the significant amounts of hotspot versus spin axis motion inferred by other authors to have occurred since the Cretaceous must have instead occurred at a faster rate and concluded before the Eocene. 相似文献
6.
The paleomagnetism of the Late Cretaceous Poços de Caldas alkaline complex (46.6°W, 21.9°S) was investigated through 42 oriented cores from seven sites. Six sites, reversed relative to the present magnetic field of the Earth, yield a pole at 127°W, 82°S (dp = 8°,dm = 13°). This pole is located close to other Late Cretaceous poles for South America obtained by Creer [1] from untreated paleomagnetic samples. The results are significantly different from those for the nearby Early Cretaceous Serra Geral basalt but close to the Triassic pole for South America. The polar wandering path for South America for the Mesozoic seems to be more complicated than anticipated. The available paleomagnetic information may not yet be precise enough to determine the time of opening of the Atlantic. 相似文献
7.
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
8.
A. M. Fetisova R. V. Veselovskiy F. Scholze Yu. P. Balabanov 《Izvestiya Physics of the Solid Earth》2018,54(1):150-162
The results of detailed paleomagnetic studies in seven Upper Permian and Lower Triassic reference sections of East Europe (Middle Volga and Orenburg region) and Central Germany are presented. For each section, the coefficient of inclination shallowing f (King, 1955) is estimated by the Elongation–Inclination (E–I) method (Tauxe and Kent, 2004) and is found to vary from 0.4 to 0.9. The paleomagnetic directions, corrected for the inclination shallowing, are used to calculate the new Late Permian–Early Triassic paleomagnetic pole for the East European Platform (N = 7, PLat = 52.1°, PLong = 155.8°, A95 = 6.6°). Based on this pole, the geocentric axial dipole hypothesis close to the Paleozoic/Mesozoic boundary is tested by the single plate method. The absence of the statistically significant distinction between the obtained pole and the average Permian–Triassic (P–Tr) paleomagnetic pole of the Siberian Platform and the coeval pole of the North American Platform corrected for the opening of the Atlantic (Shatsillo et al., 2006) is interpreted by us as evidence that ~250 Ma the configuration of the magnetic field of the Earth was predominantly dipolar; i.e., the contribution of nondipole components was at most 10% of the main magnetic field. In our opinion, the hypothesis of the nondipolity of the geomagnetic field at the P–Tr boundary, which has been repeatedly discussed in recent decades (Van der Voo and Torsvik, 2001; Bazhenov and Shatsillo, 2010; Veselovskiy and Pavlov, 2006), resulted from disregarding the effect of inclination shallowing in the paleomagnetic determinations from sedimentary rocks of “stable” Europe (the East European platform and West European plate). 相似文献
9.
碳酸盐岩是记录古地磁场信息的重要载体,然而,广泛存在的重磁化现象制约了碳酸盐岩在古地磁研究中的应用,其重磁化机制亟待解决.本文对采自贵州羊蹬地区的319块奥陶系碳酸盐岩定向样品作了详细的古地磁学和岩石磁学研究,其结果表明,94%样品(A类)记录了单一剩磁分量A,其解阻温度低于450℃;在地理坐标系下的平均方向为Dg/Ig=3.1°/48.1°(α95=2.9°),对应的古地磁极(87.0°N,2.8°E,A95=3.0°)与扬子地块古近纪-第四纪的古地磁极重合.6%样品(B类)记录了两个磁化分量,其高温分量(450℃~585℃)与A分量显著不同,但明显远离扬子块体早古生代古地磁极;低温分量(< 450℃)与A分量类似.说明羊蹬剖面奥陶系碳酸盐岩记录了两期重磁化.A分量和B低温分量的主要载磁矿物为磁黄铁矿(胶黄铁矿),B高温分量的主要载磁矿物为磁铁矿.这些磁性矿物都是成岩后的次生矿物.其中,解阻温度高于450℃的磁铁矿可能受晚燕山期造山运动影响生成;磁黄铁矿(胶黄铁矿)等矿物可能与印度板块与欧亚大陆碰撞引起的喜马拉雅造山运动所产生的流体作用有关,以后一期重磁化为主.新生代早期青藏高原隆升产生的流体在流经东南缘的碳酸盐岩等沉积岩层时,与原岩发生相互作用,使磁黄铁矿、胶黄铁矿、磁铁矿等磁性矿物生长并获得化学剩磁,造成了广泛重磁化. 相似文献
10.
Pacific plate equatorial sediment facies provide estimates of the northward motion of the Pacific plate that are independent of paleomagnetic data and hotspot tracks. Analyses of equatorial sediment facies consistently indicate less northward motion than analyses of the dated volcanic edifices of the Hawaiian-Emperor chain. The discrepancy is largest 60–70 Ma B.P.; the 60- to 70-Ma equatorial sediment facies data agree with recent paleomagnetic results from deep-sea drilling on Suiko seamount [1] and from a northern Pacific piston core [2]. Equatorial sediment facies data and paleomagnetic data, combined with K-Ar age dates along the Emperor chain [3], indicate a position of the spin axis at 65 Ma B.P. of 82°N, 205°E in the reference frame in which the Pacific Ocean hotspots are fixed. This pole agrees well with the position of the spin axis in the reference frame in which the Atlantic Ocean hotspots and the Indian Ocean hotspots are fixed [4,5], supporting the joint hypotheses that (1) the Pacific Ocean hotspots are fixed with respect to the hotspots in other oceans, (2) the hotspots have shifted coherently with respect to the spin axis, and (3) the time average of the earth's magnetic field 65 Ma B.P. was an axial geocentric dipole. Global Neogene paleomagnetic data suggest that a shift of the mantle relative to the spin axis has been occurring during the Neogene in the same direction as the shift between 65 Ma B.P. and the present. All data are consistent with a model in which the hotspots (and by inference the mantle) have shifted with respect to the spin axis about a fixed Euler pole at a constant rate of rotation for the last 65 Ma. 相似文献
11.
12.
Paleomagnetic and rock magnetic study has been conducted on the Early Triassic red beds of Liujiagou Formation from Jiaocheng,
Shanxi Province. Hematite was shown as the main magnetic mineral. After eradicating an initial viscous component at room temperature
to ~100°C–200°C, thermal demagnetization shows that most samples contain two remanence components, intermediate-temperature
remanence component at 250°C–500°C and high-temperature component at 500°C–680°C. The intermediate-temperature component has
a negative fold test at the 95% confidence level. And the pole position of the intermediate-temperature component in geographic
coordinates is correlated with the Middle Jurassic reference pole of the North China Block (NCB) within the 95% confidence,
suggesting that it might be a remagnetization component acquired during the Yanshanian period. The high-temperature component
contains both reversal and normal polarities with positive fold test and C-level positive reversal test at the 95% confidence
level, which suggests that this high-temperature component can be regarded as primary magnetization. Comparison of this newly
obtained Early Triassic paleopole with the coeval mean pole of the Ordos Basin suggests that a locally relative rotation may
have happened between the Ordos and the Jiaocheng area of Shanxi Province. This rotation may be related with two faults: one
is Lishi big fault separating Ordos from Shanxi and the other is Jiaocheng big fault, which is situated in the southeast of
sampling locality and was still in motion during the Cenozoic. 相似文献
13.
Some problems of the conventional “minimum polar distance” approach to Precambrian pole path construction are discussed. An alternative technique, based on a less restricted approach, is proposed and assessed by using all presently-available Precambrian and Paleozoic data from the world. In the construction of any pole path, assumptions are always made on the shape of the path through regions of apparently missing data. Many different assumptions are possible. Assuming that the Precambrian tectono-stratigraphic record conforms to repeated sequences of geological events suggests we should observe cycles in the paleomagnetic data. Empirically, it is found that the pole paths for the periods Cambrian-Devonian, and 750–1000 Ma, define cycles of pole motion from equator, up to and over the pole, and back down to the equator. Similar cycles of 250-Ma periodicity can be identified in paleomagnetic data back to 2500-Ma. Global wide changes in the phase of the cycles appears to be coincident with the major subdivisions of geological time i.e., Phanerozoic + Hadrynian, Helikian, Aphebian, and Archean. Finally, the geological implications of these cyclic changes in Precambrian pole paths are briefly discussed. 相似文献
14.
V. V. Shcherbakova V. P. Shcherbakov Yu. S. Bretshtein G. V. Zhidkov 《Izvestiya Physics of the Solid Earth》2010,46(12):1035-1051
We present the results of analyzing a representative collection of the middle Miocene 12.4–10.0 Ma basalts that compose the
volcanic cover of the Shufan and Sovgavan plateaus, namely the Nikolo-L’vovsk (NL) and Sovetskaya Gavan (SG) volcanic fields.
Preliminary data are obtained about the relicts of some volcanic edifices within the West and East Sikhote-Alin volcanic belts,
namely the Shishlovskii, Malyshevo, and Truzhenik objects. It is established that the volcanic rocks from these localities
are characterized by similar petrologic and magnetic properties. Thermal cleaning of the samples is carried out, and the coordinates
of the paleomagnetic pole are determined as Λ = 190.2°E, Φ = 71.3°N for basalts of the Nokolo-L’vovsk area and Λ = 180.4°E,
Φ = 71.9°N for rocks from the Sovgavan locality. These values are consistent with the data for coeval volcanics from other
regions of Eurasia. Reliable determinations of the paleointensity H
pal for a representative collection of samples were obtained using the Thellier method. The corresponding values of the virtual
dipole moment (VDM) are almost half its present-day value. The analysis of the Miocene VDM values available from the world
database revealed a low average field 5.06 × 1022 Am2 characterized by high variance σ = 2.13 × 1022 Am2 at that time. The similarity of VDM values for the Miocene characterized by frequent inversions and for the Cretaceous Superchron
supports the hypothesis of the lack of a correlation between the VDM values and the frequency of geomagnetic inversions. 相似文献
15.
过去发表的石炭纪古地理重建图存在着不少问题,特别是对亚洲各板块位置的认识上。例如,过去的重建图中华北和华南在石炭纪末都处于北半球40°—50°纬度带,但是,地层古生物资料清楚地表明,它们当时处于热带和亚热带环境。这是因为在编制上述古地理图时(70年代末和80年代初),华南和华北等东亚和东南亚地块还没有可靠的古地磁数据,因而这一地区的地块的位置是由距它们最近的西伯利亚地台的地极位置推算出来的。但是,由于这些地块和西伯利亚地台自石炭纪以来曾发生过相对运动,因此,上述作法是不合理的 相似文献
16.
Jean-Jacques Schott Raymond Montigny Robert Thuizat 《Earth and Planetary Science Letters》1981,53(3):457-470
A paleomagnetic and potassium-argon dating investigation has been carried out on a 530-km-long dike system which transects the western Iberian Peninsula in a northeasterly direction. The K-Ar age determinations were made on mineral separates exclusively. They range between 160 and 200 Ma and the authors suppose that this reflects the actual time interval of the intrusion, in accord with previous results. The paleomagnetic pole derived from 12 sites regularly distributed along the dike (71°N, 236°E) coincides well with other Mesozoic paleomagnetic poles from the western Africa. A contemporaneous pole from stable Europe is tentatively deduced from African and North American Late Triassic/Early Jurassic poles using different reconstruction models around the North Atlantic Ocean. The divergence between this pole and the Iberian pole corresponds to the result obtained for Permian poles. 相似文献
17.
18.
The paper presents the results of analyzing the set of dual-polarity paleomagnetic results the Global Paleomagnetic Database
(GPMDB). The dataset was expanded by the results from the Paleomagnetic Data Catalogue for the USSR and with new data published
after 2005. Some results were rejected to avoid the influence of overprints of ancient and recent magnetization. Overall,
59 dual-polarity results for the lithospheric plates of Baltica, Laurentia, and Siberia with their immediate framing were
selected for the analysis in the interval of ages 207–359 Ma. The new data confirmed the model of the paleomagnetic field,
according to which the field contains a long-lived component corresponding to the equatorial dipole which is responsible for
the non-antipodal paleomagnetic directions in the zones of normal and reverse polarity in sedimentary and volcanic rock sequences.
Retaining its value of 5–8% of the central axial dipole, the equatorial dipole changed its polarity a few times during the
interval 359–207 Ma. The northern poles of the dipole formed two antipodal groups on the Earth’s surface, which lie within
or near the subduction zones on the periphery of the Pangaea Supercontinent. Such localization of the equatorial dipole is
suggested to be related to the ascending branches of the mantle convection and to the topography of both boundaries of the
outer Earth’s core. 相似文献
19.
Hans Wensink 《Earth and Planetary Science Letters》1983,63(2):325-334
Paleomagnetic results are reported from 13 sites of red beds of Early Devonian age from Central Iran. Detailed paleomagnetic analyses were carried out. Two types of partial progressive demagnetization were applied, one using alternating magnetic fields, the other heating. These procedures resulted in the detection of the characteristic remanences with a mean direction with D = 24.2°, I = 1.3° (α95 = 10.1°). The paleomagnetic pole is located at 51.3°N, 163.7°W. If one shifts the Iranian landmass to its most likely position in the Gondwana configuration, then the position of the paleomagnetic pole coincides with the alternative polar wander path [14,15] which crossed South America in early Middle Paleozoic times. 相似文献
20.
Basal Paleozoic Tapeats Sandstone (Early and Middle Cambrian) in northern and central Arizona exhibits mixed polarity and a low-latitude paleomagnetic pole. Carbonates of Middle and early Late Cambrian age, and directly superposed carbonate and carbonate-cemented strata of latest Middle(?) and early Late Devonian age, are characterized by reversed polarity and high-latitude poles. The high-latitude Middle Cambrian pole, which appears to record a large but brief excursion of the polar wandering path, is considered provisional pending additional work. The Devonian data from Arizona indicate that a shift of the pole to a “late Paleozoic” position had occurred by Middle Devonian time. 相似文献