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1.
Data on the geomagnetic field intensity in the first millennium BC and the 8th–10th centuries AD are obtained from the study of materials from the El Molon archaeological monument (Spain). A 75-yr averaged curve of the variation in the geomagnetic field intensity in the area of the zero meridian over the last three millennia is constructed from a set of new and previously obtained data on the geomagnetic intensity variations in Spain and France. The field intensity smoothly decreases in the time interval studied, and variations a few centuries long are superimposed on this trend. Unlike the present-day relationship, the average level of the geomagnetic field intensity in Spain in the first millennium BC was higher than in the Caucasus.  相似文献   

2.
The geomagnetic intensity variation from the middle of the 4th millennium BC to the beginning of the 2nd millennium BC is reconstructed from the archaeomagnetic study of ceramic material taken from 24 layers of the Los Castillejos monument (Montefrio, Spain). The general patterns of the geomagnetic intensity variation reconstructed by studying materials from the Cendres Cave and Los Castillejos monuments (Spain) are similar. The intensity level is revised in the time interval including the minimum of the “fundamental” oscillation of the geomagnetic field; the characteristics of geomagnetic intensity variations whose superposition can provide the intensity variation observed in the study time interval are determined. Constraints on the climate humidity variation over the settlement lifetime are obtained from heating-induced variations in the magnetic susceptibility of the ceramics.  相似文献   

3.
The archaeomagnetic study of the ceramics from the multilayered archeological monument Ubeda in Spain provided the data on the geomagnetic field strength in the period of accumulation of cultural deposits. According to the results obtained for the Ubeda monument of the Bronze Age and the La Motilla Del Azuer multilayer archaeological monument dated to the second millennium BC, the time interval of accumulation of the Ubeda cultural deposits likely spans from the last quarter of the 19th to 18th centuries BC. The sharp decrease in the geomagnetic field strength in the 19th century BC. established against the obtained data is consistent with the archaeomagnetic results for other Eurasian regions and can be used for correlating the ages of various archeological monuments and stages of culture.  相似文献   

4.
The conducted archeomagnetic studies resulted in data on variations in the geomagnetic field intensity in the central East European Plain (Sakhtysh I site area, ? = 56°48′ N, λ = 40°33′ E) during the time interval of 5–3 ka BC. The geomagnetic field intensity varied mainly within the range of 30–60 μT. In the first half of the 5th millennium BC, the mean level of geomagnetic field intensity was about 35 μT. In the second half of the 5th–early 4th millennium BC, it rose to about 50 μT and then decreased again to reach a mean value of about 40 μT in the period of 4–3 ka BC. Comparison of the geomagnetic field intensity variation based on the obtained data and the data on the Caucasus region for the same time interval demonstrates a certain similarity.  相似文献   

5.
The geomagnetic field variation pattern in the second and third quarters of the first millennium BC is obtained from data on ceramic material sampled in the Los Villares multilayer archaeological monument (Spain). The analysis of available data on the geomagnetic field variation in Spain over the last seven millennia shows that it is similar to the geomagnetic variation pattern observed in other Eurasian regions. The amplitude of the “fundamental” (8000-yr) oscillation (≈20 μT) estimated from the Spain data exceeds significantly its amplitudes in other regions, which supports the previously noted tendency to a westward increase in the amplitude of the fundamental oscillation.  相似文献   

6.
The magnetization of ceramic material manufactured in the eastern Mediterranean is studied. Data on the variation in geomagnetic field intensity in the time interval from the fourth-quarter of the 6th century BC through the 2nd century AD are obtained. The main tendency of the variation in the field intensity until approximately the middle of this interval is its decrease, after which the average intensity level varied insignificantly over the three next centuries. Variations with characteristic times of a few tens to a few hundreds of years are superimposed on the smooth variation in the field intensity approximated by a sinusoid with a period of 1600 yr. The data obtained in this work confirm the previously derived conclusion that short-term intensity variations have been permanently present in the geomagnetic field in the recent millennia.  相似文献   

7.
The study of magnetization of the ceramic material from 21 archeological monuments of Portugal (the Evora province), dated archeologically from the Bronze Age to the end of the Iron Age has been carried out. For the purpose of more detailed timing of the material from the monuments the method of ceramic age dating on the basis of its porosity has been used. In order to take into account the distorted factors in the determination of the parameters of the ancient geomagnetic field with the aim of the maximal approximation to the actual values the diagnostic features of magnetite weathering have been considered and the level of weathering of the magnetic fraction in the ceramics from archeological monuments has been determined. The data of geomagnetic field-strength variation in the time interval of the 12th century BC to the beginning of the Common Era have been obtained. The field-strength at this time interval varied in the range of 60–90 micro Tesla with the maximal values in the 9th, 8th, and the second half of the 5th to the beginning of the 4th century BC. In addition, the timing of the ceramic material from the urns of the megalithic complex Monte de Tera of the Evora province has been clarified.  相似文献   

8.
The Bronze ceramics of the Baeza archeological monument in Spain is studied by archaeomagnetic methods. In the 19th and 18th centuries B.C, the intensity of the geomagnetic field varied from 40 to 60 mkT. The variations are smooth; they attained their maximum in the 16th to 15th centuries B.C. The obtained data on the variations in the geomagnetic intensity perfectly agree with the results of previous investigations for the ceramics from the Bronze Age multilayered archeological monuments Azuer and Ubeda. The temperature in the region of the Baeza monument is estimated in the interval from the 18th to the 13th centuries B.C. It experiences wave-like variation, ranging from ??15 to 23°C and attains its maximum in the 16th century B.C.  相似文献   

9.
We present an updated compilation of Greek directional archaeomagnetic data for the last 4.5 millennia. The data set comprises 89 directions from archaeological artefacts and volcanic rocks. Most of the data come from the Late Bronze Age (1700-1400 BC) that is the flourishing period of the Minoan civilization in Crete, while parts of the classical (480-323 BC), Hellenistic (323-31 BC) and Roman (146 BC-330 AD) periods are also well covered. The dataset has been analysed using the Bayesian approach for curve building and a directional secular variation (SV) curve for Greece is proposed. Comparisons with regional and global model predictions show a general agreement even though some discrepancies are observed for some time intervals. The new curves together with the previously published intensity SV curve for Greece, also using the Bayesian approach, form a homogeneous set and enrich our knowledge of the full geomagnetic field vector variation in Greece during the last millennia.  相似文献   

10.
Dating of soil layers in a young floodplain using iron oxide crystallinity   总被引：1，自引：0，他引：1  
Dating of fluvial deposits is essential for a more quantitative understanding of landscape evolution and soil development in floodplain environments. We collected soil layers in defined depth intervals down to 60 cm along a substrate age gradient in a floodplain of the Danube River near Vienna, Austria. Depth profiles of fallout 137Cs were used to assess short-term sedimentation, and optically stimulated luminescence (OSL) dating was used to attribute sediment deposits to time periods between the early last millennium BC and the 18th century AD. In the studied soils, the ratio of oxalate- to dithionite-extractable iron (Feo/Fed), which indicates the degree of iron oxide crystallinity, progressively decreased from ratios greater than 0.5 to values less than 0.2 with increasing soil age and proved to be a reliable indicator of soil maturity. We linked the observed Feo/Fed ratios to the radiometric and OSL ages in a chronofunction, which allows to approximately date soil layers that lack an independent age control. The soil ages calculated with this chronofunction accurately reflected their geomorphological position, resulted in consistent age trends with depth, and highlighted the active morphodynamics of the studied floodplain. The chronofunction was further validated by dating a soil profile near the studied chronosequence that contained an archaeological find dated to the La Tène period (5th to 1st century BC).  相似文献   

11.
Archaeomagnetic study and rehydroxylation dating of fired-clay ceramics from Great Britain, Spain, and the Black Sea region is carried out in order to refine the dating of the material from the archaeological monuments used in the archaeomagnetic research for determination of the elements of the main magnetic field during the past few millennia. The archaeomagnetic analysis revealed the factors responsible for deviations of the rehydroxylation dating from the true values. They include the processes of weathering (magnetite transformation into hydroxides) and secondary magnetization (e.g., magnetization in a fire). In order to bring the dating closer to the true values, corrections for the influence of the distorting factors are suggested. The data on the geomagnetic field intensity derived from the magnetization of the studied material are used as independent criteria to validate the dating of the field. When applied to the fired clay material with reliable dating, the rehydroxylation method provides the estimates of the temperature in the region of archaeological monuments during the past.  相似文献   

12.
The archaeomagnetic studies of ceramics from the Hermonassa multilayer archaeological monument in the Taman Peninsula provided the data on the intensity of the main geomagnetic field in the past. The data for the interval from VIII to XX centuries A.D. demonstrate a well pronounced decreasing trend in the geomagnetic field intensity during this time. Three stages, each lasting for a few centuries, are distinguished in the variations of the centennial average field which slightly varies within each stage and generally decreases from 70 to ~45 μT during the entire period from VIII to XX centuries A.D. The variations of the geomagnetic field in the interval from XII to XVII centuries A.D. have a form of quasi-harmonic oscillations with a characteristic time of about 300 years.  相似文献   

13.
The magnetization of ceramics from the eastern Mediterranean dated within a short period (mostly shorter than ±20 years) has been studied, which made it possible to specify the geomagnetic field variations on the time interval 5th–3rd centuries BC. The 11-year time series of the geomagnetic field strength values has been constructed. The field strength changes have been considered, which indicated that the centennial variation with a characteristic time of ～130 years (according to the obtained data) is observed on this time interval as well as during the last two millennia. The ceramic material from the Mayskaya Gora archeological site (Taman), the preparation succession of which was established based on the shape of pottery but the problem of absolute dating was not solved, has been dated.  相似文献   

14.
The archaeomagnetic determinations obtained from the collections of archaeological materials, dated in the last 2000 years are summarized. The review describes the materials used, the methodology applied, the local database organization, the principles of data processing and smoothing procedures. Errors evaluation at different levels of analysis of the experimental results are described. Special attention is paid to the archaeointensity determinations. Some rock magnetic properties studied in connection with the difficulties in the Thellier method are summarised. The curves of geomagnetic field elements variations for the last 2000 years for Bulgaria are shown. The Bauer plots, VGP path and VDM curve are also discussed, the latter confirming the general decrease in the strength of the geomagnetic field from the beginning of this era to the present. Westward drift of the geomagnetic field non-dipole part cannot be considered proved yet for the time interval 7th to 13th Centuries AD from the Bulgarian directional data.  相似文献   

15.
We calculated and analyzed variation of the non-dipole(ND)magnetic field at the millennium scale over the Chinese mainland during 2000 BC–1900 AD using the newest global geomagnetic model,CALS3K.4(3K.4).The newest-generation IGRF(IGRF11)was used to verify the results.Taking component Z for example,we calculated and analyzed the distribution and annual change rates of the ND field during 1900–1990 AD every 5 yr,using two models.To thoroughly analyze the contributions of field sources,quadrupole and octupole fields,and others within the ND field at the surface and core-mantle boundary(CMB)were investigated.Results show that there were three main variation phases of the field during the period 2000BC–1900 AD.The mean amplitude roughly reflected the ND field because of the distribution and variation of that field,corresponding somewhat to the mean amplitude change.A magnetic anomaly of the ND field over East Asia(EA)first emerged in 1682 AD,and its extreme intensity had increased a total of 15276.95 nT by 1900 AD.Its location moved continuously southeastward after 1690 AD.The asymmetry between location and intensity of extreme points over EA,particularly during1740–1760 AD,indicates irregularity of fluid motion inside the outer core.Mean annual changes of Z are generally divided into four phases,which first oscillated between 2000 and 800 BC,then increased,decreased and increased in the periods 800BC–300 AD,300–900 AD and 900–1900 AD,respectively.The intensity of mean annual change increased a total of 22.87nT/yr.Anomaly extreme locations based on 3K.4 and IGRF11 over EA centered around 44°N and 103°E for degree(n)greater than 5,and intensities continuously increased with n.During 2000 BC–1990 AD,ND energy of Z at the surface and CMB had decreased in total by 18.29%and 23.23%,respectively.The field source of 26–210 pole fields are more or less affected by the lithospheric field.Energies of higher degree at the surface attenuate by almost 99%compared with CMB,but mean attenuation speeds of the low-degree ND field are faster than high-degree,which implies that the low-degree ND field has a deeper source.  相似文献   

16.
Results from joint work between the Geophysical Institute (Sofia, Bulgaria), and the Geomagnetic Institute (Grocka, Yugoslavia) on the geomagnetic field variation in the prehistoric past are presented. Preliminary curves of variation of the three geomagnetic elements: declination, inclination and intensity are presented. The movement of the virtual pole position for the 6500 years time period B.C. is derived. The curves and the virtual pole positions provide a dating tool for archaeological purposes and determination of the periodicities in the geomagnetic secular variations in southeastern Europe.  相似文献   

17.
Spatiotemporal variations of the nondipole (ND) magnetic field over the Chinese mainland and neighboring regions from 10000 BC to 1990 AD were analyzed using the latest global geomagnetic models CALS10K.1b, CALS3K.4, and IGRF11. Moreover, for field sources, we investigated 2 n (n = 2–10) pole ND fields and their energies. The results suggest that the study period can be divided into three. The intensity of the ND field has been mainly positive since 10000 BC and lasted almost 7500 years, then gradually decreased to negative in 2500 BC to 1500 AD, and finally sharply increased to positive. The anomaly areas of the ND field in East Asia took shape for n = 3, when the anomaly areas in East Asia were shaped into closed circles in the mainland. This suggests that the first three harmonic degrees account for most of the ND field. The energy of the ND field rapidly attenuates at the core–mantle boundary and is stable at the surface.  相似文献   

18.
Sediments from Site 769 of the Ocean Drilling Program's Leg 124 provide a record of geomagnetic intensity variation over the past 110 ky. Using continous shipboard measurements exclusively, I estimate the variation in the geomagnetic field strength by employing low-field magnetic susceptibility as a normalization parameter for the measured remanence intensity. By calibrating the resultant relative paleointensity record against previously available Holocene age estimates of absolute paleointensity, I derive an estimate of virtual dipole moment since 110 ka. The record obtained from these Sulu Sea sediments is strikingly like that previously obtained from sediments of a similar age in the Mediterranean Basin with distinct intervals of low intensity near 15, 20, 40 and 65–70 ka. The Sulu sediments also indicate a low-intensity feature near 108 ka. Important differences in paleointensity estimates obtained from these different regions for the interval between 30 and 20 ka suggest that a relatively large non-dipolar component of the geomagnetic field might have been present at that time.  相似文献   

19.
根据19360年426个地磁测点和28个IGRF计算的地磁数据,计算地磁场和地磁异常场各个分量的曲面Spline模型,并绘制相应的地磁图和地磁异常图.依据我国部分地区的1909～1915,1915～1920,1920～1930,1930～1936年间地磁偏角长期变化图,1908～1917,1917～1922,1922～1936年间水平强度长期变化图和1908～1922,1922～1936年间垂直强度长期变化图,使用曲面Spline方法,分别计算上述9个时间段的磁偏角（D）、水平强度（H）和垂直强度（Z）长期变化的曲面Spline模型,并绘制相应的长期变化图.根据这些长期变化模型,将19360年426个点的三分量绝对值数据归算至1940,1930,1920,1910年和1900年,从而为计算这5个年代的地磁场模型奠定了坚实的基础.  相似文献   

20.
We present palaeomagnetic data obtained from large clasts collected in non-welded pyroclastic deposits from Montagne Pelée volcano (Martinique Island, West Indies). These deposits, dated by the 14C method from 5000 yr BP to the present, comprise block- and ash-flows, ash- and pumice-flows and pumice fallouts. Alternating fields treatment was as a routine chosen to demagnetise large samples for which the magnetisation was measured with a specially designed inductometer. The mean directions obtained from block- and ash-flow deposits of the 1902 and 1929 eruptions are in good agreement with the expected geomagnetic directions at these times in Martinique. The so-called P1 eruption (∼1345 AD), which is characterised by a rarely observed transition from a Peléean to a Plinian eruptive style, allows a direct comparison of the palaeomagnetic directions obtained from the three types of pyroclastic deposits. All deposits provide identical mean directions, which further demonstrates the suitability of the non-welded pyroclastic deposits for geomagnetic secular variation study with a very good accuracy and precision. The possibility of using pyroclastic deposits is promising for obtaining a wider distribution of sampling sites, which may better allow us to constrain our knowledge on the geomagnetic secular variation. We find that large geomagnetic changes occurred in Martinique during the last millennium, while the variations appear more limited prior to this period.  相似文献   

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