排序方式： 共有12条查询结果，搜索用时 15 毫秒
1.
2.
Nicholas Teanby Carlo LajDavid Gubbins Malcolm Pringle 《Physics of the Earth and Planetary Interiors》2002,131(2):101-140
A new record of absolute palaeointensity was obtained from drill core Scientific Observation Hole 1 (SOH1) on Kilauea volcano, Hawaii. Kilauea’s high eruption rate resulted in a relatively continuous record and stratigraphic constraints preserved the chronological order. Three hundred and sixty samples were studied with the Thellier-Thellier technique, which gave 195 successful palaeointensity and 271 successful inclination determinations. Three geomagnetic excursions were observed, which exhibited intensity reductions of about 50%. Initial age control from K-Ar and Ar/Ar dating only constrained the total age between 20 and 120 ka. The final age model was obtained by stretching the SOH1 record relative to other Hawaiian palaeomagnetic data. This gave an age range of 0-45 ka for the flows and identified the excursions as the Hilina Pali, Mono Lake and Laschamp events. The SOH1 record of the Hilina Pali event is the most detailed ever, incorporating data from around 40 flows. This age model suggests that Kilauea had a burst of activity at the SOH1 site around 20 ka. All available data was combined to form a composite record of palaeointensity and inclination on Hawaii for 0-45 ka. 相似文献
3.
4.
Magnetostratigraphic analyses of five sediment cores recovered from the Kolbeinsey Ridge area revealed consistent records
of several geomagnetic events linked with low relative palaeointensities within the past 300 ka. Interpretation of various
rock magnetic parameters clearly rule out the possibility that the recorded non-normal polarity directions are linked to a
deviating magnetomineralogical fraction or a distorted magnetic fabric. Therefore, these directions are interpreted as true
recordings of geomagnetic field variations. Hysteresis parameters and thermomagnetic measurements revealed pure pseudo single-domain
(PSD) magnetite with Curie temperatures of 580 °C as the dominant remanence carrier mineral. Due to the homogeneity of the
rock magnetic parameters, the sediments are also suitable for relative palaeointensity determinations. Oxygen-isotope stratigraphies
for two of the cores provided a time frame to estimate the age ranges for the recorded geomagnetic field variations. The obtained
record of ten events of up to 12 ka duration during the past 300 ka and the related record of relative palaeointensity indicate
a fairly dynamic character of the Earth's magnetic field, which is in clear contrast to published polarity time scales.
Received: 2 July 1998 / Accepted: 5 February 1999 相似文献
5.
Nobutatsu Mochizuki Hideo Tsunakawa John Cassidy 《Physics of the Earth and Planetary Interiors》2006,154(2):168-179
We report new palaeointensity results concerning the Auckland geomagnetic excursions using the double heating technique of the Shaw method with low temperature demagnetisation (LTD-DHT Shaw method). The excursional palaeodirections recorded in six volcanoes of the Auckland volcanic field, New Zealand, have been classified into three groups: north-down (ND), west-up (WU) and south-up (SU) directions. In the present study, five to six consistent palaeointensities have been obtained from each of five volcanoes recording the Auckland geomagnetic excursions. The Wiri (27 ka), Crater Hill and Puketutu volcanoes (ND group) yielded mean palaeointensities of 10.6 ± 1.2 (1σ), 11.8 ± 2.8 and 11.1 ± 0.4 μT, respectively. The Hampton Park volcano (55 ka; WU group) gave 9.5 ± 1.2 μT while the McLennan Hills volcano (SU group) gave 2.5 ± 0.5 μT. It is notable that consistent palaeointensities have been obtained from the three different volcanoes which have almost the same palaeodirections (ND group), possibly supporting the reliability of the palaeointensity data. These five palaeointensities for the Auckland geomagnetic excursions correspond to virtual dipole moments (VDMs) of 0.6-2.1 × 1022 A m2, whereas three mean palaeointensities obtained from the Auckland volcanoes having non-excursional palaeodirections are 13.1-40.0 μT giving stronger VDMs of 2.1-6.9 × 1022 A m2. These results suggest that the dipole component of the geomagnetic field reduced to about 2 × 1022 A m2 or less during the Auckland geomagnetic excursions. 相似文献
6.
Peter Riisager Janna Riisager Niels AbrahamsenRegin Waagstein 《Physics of the Earth and Planetary Interiors》2002,131(2):91-100
Based on palaeomagnetic and rock magnetic results, 108 samples from 27 flows from Palaeogene flood basalts of Faroe Islands were chosen for whole-rock Thellier palaeointensity experiments. Altogether 90 samples were rejected due to either chemical alterations or typical multidomain (MD) behaviour evidenced by pTRM-tails. AF pre-treatment was used to reduce the effect of MD grains on Thellier experiments. Only five flows (18 samples) yielded acceptable palaeointensity estimates, with flow mean VDMs ranging from 3.5 to 7.4×1022 A m2. Modest selection criteria imposed on all published 5-160 Ma palaeointensity data left only 15 palaeomagnetic dipole moments: eight from whole-rock samples, six from submarine basaltic glass and one from single plagioclase crystals. More data are needed before the intriguing differences between results from different materials can be put into a geomagnetic context. 相似文献
7.
白垩纪地球物理场异常与地球深部动力学 总被引：9，自引：1，他引：9
通过对白垩纪超静磁带（CNS）期间发生的重要地质事件，如大洋缺氧事件，大量火山活动以及温度升高等的综合分析，并结合地球磁场古强度研究结果，探讨了白垩纪地球物理场异常与地球深部动力学的可能相关性。 相似文献
8.
运用 Thellier 逐步热退磁法,主要测定了我国四川一些地区新石器时期至明、清各朝代的地球磁场总强度值。本文结果表明,在过去5000多年里,该地区地球磁场的总强度随时间呈较大幅度的变化。将该地区与我国其它相关地区地球磁场总强度的长期变化曲线进行对比研究的结果表明:变化的总趋势大致可比,但最高值出现的时间不同.从过去四千年间,新疆、四川、广东、福建及洛阳一些地区的地球磁场强度变化曲线中最高峰和跨时千余年的"M"型变化中低峰出现的时间推得的滞后速度在0.01°-0.03°/a 之间。 相似文献
9.
Fco. Javier Pavón–Carrasco Maria Luisa Osete J. Miquel Torta Luis R. Gaya–Piqué 《Pure and Applied Geophysics》2008,165(6):1209-1225
The SCHA.DI.00 directional model for the geomagnetic field in Europe for the last 2000 years (Pavón–Carrasco
et al., 2008) has been updated by modelling the palaeointensity. This model, SCHA.DI.00, was developed from available Bayesian
European Palaeosecular Variation Curves using the regional Spherical Cap Harmonic Analysis technique. The comparison of the
palaeosecular variation curves, given by the regional model, with available archaeomagnetic data not used in its development
showed an improvement with respect to the fit obtained by global archaeomagnetic models. In this paper advantage is taken
of recently published palaeointensity databases to develop a complete (direction and intensity) regional archaeomagnetic model
for the last 2000 years valid for the European region: the SCHA.DI.00–F model. Not only does this complete model provide an
improvement for example for archaeomagnetic data studies, but it is also shown that this new regional model can be used to
study the recently proposed link between the centennial secular variation of the geomagnetic field and climate change. The
pattern of the archaeosecular variation of the field intensity obtained by SCHA.DI.00–F seems to verify the hypothesis presented
by Gallet et al. (2005) about a possible (causal) connection between changes in the geomagnetic field intensity and in climate parameters,
opening the door for more discussions on this challenging subject. 相似文献
10.