Step-wise and continuous thermal demagnetization and theories of thermoremanence     

P. W. Schmidt  D. A. Clark 《Geophysical Journal International》1985,83(3):731-751

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Long-chain alkenones and U₃₇′ variability along a south–north transect in the Western Pacific Ocean     

Ilhem Bentaleb  Michel Fontugne  Luc Beaufort 《Global and Planetary Change》2002,34(3-4)

In this paper, we present 50 surface water samples collected during the IMAGES III cruise (June–July 1997) along a transect from New Zealand to the China Sea (42°S–178°E, 21°N–120°E) covering a temperature range from 13.3 to 30.4 °C. A very worthwhile aspect of this study is a coupling of both biomarker (alkenone) and coccolithophorid counting. We show that the U₃₇^k′–temperature relationship is very similar to the Prahl et al. [Geochim. Cosmochim. Acta 52 (1988) 2203] culture calibration and to the global core top calibration of Müller et al. [Geochim. Cosmochim. Acta 62 (1998) 1757]. However, in the warmest surface waters of the Western Pacific ocean (>26.4 °C) where Gephyrocapsa oceanica is likely the most widespread species, the associated U₃₇^k′ has a constant value of 1.0. The consequence is that above this temperature threshold, U₃₇^k′ cannot be used as an accurate paleothermometer.  相似文献   

Deconvolution of long-core palaeomagnetic measurements—spline therapy for the linear problem     

Catherine Constable  Robert Parker 《Geophysical Journal International》1991,104(3):453-468

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Analytical solutions of one‐dimensional infiltration before and after ponding     

Jiann‐Mou Chen  Yih‐Chi Tan  Chu‐Hui Chen 《水文研究》2003,17(4):815-822

This paper is a continuation of previous research, which obtained a convenient solution for arbitrary surface fluxes before ponding. By means of Fourier Transformation this has been extended to derive analytical solutions of a linearized Richards' equation for arbitrary input fluxes after surface saturation. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Spatial and temporal variability of crustal magnetization of a slowly spreading ridge: Mid-Atlantic Ridge (20°–24° N)     

R. A. Pockalny  A. Smith  P. Gente 《Marine Geophysical Researches》1995,17(3):301-320

The results of the two- and three-dimensional magnetic inversions performed on data located between 20°–24° N on the Mid-Atlantic Ridge indicate the crustal magnetization has decayed exponentially for the last 10 Ma, and that this decay has been fairly symmetric about the ridge axis. After removal of the mean temporal decay, the residual field is characterized by more positive magnetizations at the second-order discontinuities, regardless of initial magnetization direction. A model that involves the preferential emplacement of serpentinized lithologies near the discontinuities is proposed to explain this correlation. The temporal detrending method also indicates that several ridge-parallel depressions located on the flanks of the ridge axis are regions of more positive magnetizations. These bathymetric depressions may mark the locations of detachment faulting that occurred during amagmatic periods of extension. The general symmetry of the crustal magnetization about the ridge axis does not support the occurrence of continuous detachment faulting proposed to correspond to the inner and outer corners of ridge axis discontinuities.  相似文献   

确定任意磁性体磁化方向的样条函数法     

姜效典 《中国海洋大学学报(自然科学版)》1992,(2)

由磁异常Z_α和重力异常g,利用样条函数的微、积分性质,从泊松方程出发,直接解得磁性体的磁化方向。该方法适用于任意形状磁性体的磁异常。  相似文献   

Three-dimensional inversion of marine magnetic anomalies: Implications for crustal accretion along the Mid-Atlantic Ridge (28°–31°30′ N)     

J. E. Pariso  C. Rommevaux  J. -C. Sempere 《Marine Geophysical Researches》1996,18(1):85-101

We present magnetic field data collected over the Mid-Atlantic Ridge in the vicinity of the Atlantis Fracture Zone and extending out to 10 Ma-old lithosphere. We calculated a magnetization distribution which accounts for the observed magnetic field by performing a three-dimensional inversion in the presence of bathymetry. Our results show the well-developed pattern of magnetic reversals over our study area. We observe a sharp decay in magnetization from the axis out to older lithosphere and we attribute this decay to progressive low temperature oxidation of basalt. In crust which is 10 Ma, we observe an abrupt increase in magnetic field intensity which could be due to an increase in the intensity of magnetization or thickness of the magnetic source layer. We demonstrate that because the reversal epoch was of unusually long duration, a two-layer model comprised of a shallow extrusive layer and a deeper intrusive layer with sloping polarity boundaries can account for the increase in the amplitude of anomaly 5. South of the Atlantis Fracture Zone, high magnetization is correlated with bathymethic troughts at segment end points and lower magnetization is associated with bathymetric highs at segment midpoints. This pattern can be explained by a relative thinning of the magnetic source layer toward the midpoint of the segment. Thickening of the source layer at segment endpoints due to alteration of lower oceanic crust could also cause this pattern. Because we do not observe this pattern north of the fracture zone, we suggest it is a result of the nature of crustal formation process where mantle upwelling is focused. South of the fracture zone, reversals along discontinuity traces only continue to crust 2 Ma old. In crust >2 Ma, we observe bands of high, positive magnetization along discontinuity traces. We suggest that within the discontinuity traces, a high, induced component of magnetization is produced by serpentinized lower crust/upper mantle and this masks the contribution of basalts to the magnetic anomaly signal.  相似文献   

台湾海峡上升流区夏季溶解氧的特征     

陈水土  阮五崎 《热带海洋学报》1992,(3)

本文根据1983—1984年,1987—1988年台湾海峡中北部海域调查资料,着重讨论了该海域夏季溶解氧分布特征及其与上升流、生物活动的关系。该上升流区温度、盐度、溶解氧含量及其饱和度的特征值分别为24.4℃,34.3,4.49mlO_2/L和93％。溶解氧含量及其饱和度与温度呈正相关关系,与盐度呈负相关关系。  相似文献   

磁通门罗盘的原理     

王文彬  程彦秋 《海洋技术学报》1992,11(2):21-27

磁通门罗盘是一种新型罗盘。此罗盘的关键部件是探头,探头主要是由高导磁的软磁材料做成的磁环和线圈组成。当在初级线圈加上交变的激励信号时,即可得到与次级线圈在地磁场中相对应的磁方位角。本文介绍其原理,并对其进行了理论分析。  相似文献   

松散沉积物中天然气水合物生成、分解过程与声学特性的实验研究   总被引：5，自引：1，他引：4  

胡高伟  业渝光  张剑  刁少波  刘昌岭  王红霞  王家生 《现代地质》2008,22(3):465-474

为了解松散沉积物中天然气水合物的生成和分解规律以及水合物对沉积物声学特性的影响,在粒径为0.18~0.28mm天然沙中进行了甲烷水合物的生成和分解实验,并利用超声波探测技术和时域反射技术实时测量了反应体系的声学参数与含水量。结果表明:根据水合物的生成和分解速率,可将水合物的生成过程分为初始生长期、快速生长期和稳定期3个阶段,分解过程可分为初始分解期和样品表层水合物快速分解期以及样品内、外层水合物均快速分解期3个阶段;由温度和压力数据的分析,得出水合物先在沉积物表层生长,然后在沉积物内、外层迅速生成;由水合物分解过程3个阶段的平均分解率,得出水合物的分解是一个由慢到快的过程。对声学参数的研究表明:水合物在松散沉积物中先胶结骨架颗粒而生成,使纵波速度和声波衰减在饱和度0~1%之间陡然增大;随后水合物开始在沉积物孔隙中形成悬浮粒子,造成超声波信号在饱和度1%~90%间淬熄,声波速度无法获取。研究结果在揭示沉积物中水合物与颗粒间接触机制的同时,为海上地球物理勘探中地震信号的解释提供了新的思路。  相似文献