Matuyama-Brunhes reversal and Kamikatsura event on Maui: paleomagnetic directions, Ar/Ar ages and implications     

Robert S. Coe  Brad S. Singer 《Earth and Planetary Science Letters》2004,222(2):667-684

Eighty-nine basaltic lava flows from the northwest wall of Haleakala caldera preserve a concatenated paleomagnetic record of portions of the Matuyama-Brunhes (M-B) reversal and the preceding Kamikatsura event as well as secular variation of the full-polarity reversed and normal geomagnetic field. They provide the most detailed volcanic record to date of the M-B transition. The 24 flows in the transition zone show for the first time transitional virtual geomagnetic poles (VGPs) that move from reverse to normal along the Americas, concluding with an oscillation in the Pacific Ocean to a cluster of VGPs east of New Zealand and back finally to stable polarity in the north polar region. All but one of the 16 Kamikatsura VGPs cluster in central South America. The full-polarity flows, with ⁴⁰Ar/³⁹Ar ages spanning a total of 680 kyr, pass a reversal test and give an average VGP insignificantly different from the rotation axis, with standard deviation consistent with that for other 0-5 Ma lava flows of similar latitude. Precise ⁴⁰Ar/³⁹Ar dating consisting of 31 incremental heating experiments on 12 transitional flows yields weighted mean ages of 775.6±1.9 and 900.3±4.7 ka for the M-B and Kamikatsura transitional flows, respectively. This Matuyama-Brunhes age is ∼16 kyr younger than ages for M-B flows from the Canary Islands, Tahiti and Chile that were dated using exactly the same techniques and standards, suggesting that this polarity transition may have taken considerably longer to complete and been more complex than is generally believed for reversals.  相似文献   

A mixed finite-element method for solving the poroelastic Biot equations with electrokinetic coupling     

C. C. Pain  J. H. Saunders  M. H. Worthington  J. M. Singer  W. Stuart-Bruges  G. Mason  A. Goddard 《Geophysical Journal International》2005,160(2):592-608

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Comment on “Metallic Mineral Resources in the Twenty-First Century: I. Historical Extraction Trends and Expected Demand” by Alberto E. Patino Douce,in Natural Resources Research DOI: 10.1007/s11053-015-9266-z     

Donald A. Singer  W. David Menzie 《Natural Resources Research》2016,25(1):91-91

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The new approach to global deep sounding     

E. B. Fainberg  A. V. Kuvshinov  L. P. Mishina  B. Sh. Singer 《Pure and Applied Geophysics》1990,134(4):527-531

The new approach to global geomagnetic sounding is developed to overcome difficulties of spherical harmonical analysis and subsequent transfer function determination. The approach is based on minimizing the discrepancy between experimental and simulated magnetic fields. The discrepancy is considered as a function of the medium model parameters and the coefficients of external fields. The method can be used for laterally inhomogeneous as well as homogeneous earth models. An example of its application to a radially symmetric model is demonstrated.  相似文献   

Electromagnetic fields induced in the world's oceans and the spatial distribution of electrical conductivity functions     

E.B. Fainberg  B.Sh. Singer  A.V. Kuvshinov 《Physics of the Earth and Planetary Interiors》1983,32(4):293-300

The results of numerical simulation of electromagnetic fields induced in the world's oceans by solar daily variations are discussed. Some examples of apparent resistivity curves simulated for continental and ocean regions are demonstrated.  相似文献   

Correction for distortions of magnetotelluric fields: Limits of validity of the static approach     

B. Sh. Singer 《Surveys in Geophysics》1992,13(4-5):309-340

Subsurface inhomogeneities can be classified in three categories depending on the comparison of their sizes against the effective skin depth and “adjustment distance”. These categories are geological noise, local and regional inhomogeneities. Due to its random nature, geological noise leads to uncontrollable distortions of the magnetotelluric field. Such methods as curve shifting, distortion tensor techniques, decomposition and spatial filtering can effectively be used to correct for static shift caused by geological noise. It is shown that the effects of local and regional subsurface inhomogeneities reduce to static shifts of MT-curves when rather rigid conditions are satisfied. The methods used to suppress the effect of geological noise have limited applicability to local and regional inhomogeneities, which can be accurately accounted for only by modelling.  相似文献   

Time dependence of magnetic susceptibility of soil chronosequences on the California coast   总被引：1，自引：0，他引：1  

M. J. Singer  P. Fine  K. L.Verosub  O. A. Chadwick 《Quaternary Research》1992,37(3)

As the age of the soils in a chronosequence on the California coast increases, the difference between the magnetic susceptibility of eluvial and illuvial horizons increases, and the residual susceptibility after extraction with citrate-bicarbonate-dithionite (CBD) decreases. Enhanced susceptibility results from the conversion of nonferrimagnetic minerals to secondary ferrimagnetic forms (most likely maghemite) and the preferential accumulation of inherited and pedogenic magnetic minerals. Little enhancement occurs for pedons younger than 40,000 yr. By 124,000 yr, most of the magnetic susceptibility can be attributed to forms soluble in CBD. Magnetic susceptibility appears to vary systematically over time for three chronosequences from areas with mean annual precipitation ranging from 650 to 1500 mm yr⁻¹. Magnetic susceptibility enhancement may be a useful parameter for estimating soil age in certain climates.  相似文献   

Cloud height differences on Saturn     

Jerome Apt  Robert B. Singer 《Icarus》1982,52(3):503-508

Spectrophotometry from 0.6–2.5 μm at 1.5% spectral resolution of Saturn's equator and visibly dark South Equatorial Belt near a 1980 ring-plane crossing shows substantially less absorption by methane over the equator than over the SEB. Model fits using Appleby's model atmosphere and a multiple scattering model lead to the conclusion that the pressure levels of the clouds in the two regions differ by 20%. The region of high clouds is coincident with the location of the equatorial fast jet observed by Voyager.  相似文献   

Statistical analysis of geological data: George S. Koch Jr. and Richard F. Link. John Wiley and Sons,New York N.Y., 1970, 375 pp., U.S. $ 12.55     

D.A. Singer 《Tectonophysics》1971

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Initial Characterisation of SK01 Sanidine: A Candidate 40Ar/39Ar Reference Material     

Youjuan Li  Brian R. Jicha  Wanfeng Zhang  Wen Chen  Brad S. Singer  Dewen Zheng  Huaiyu He 《Geostandards and Geoanalytical Research》2023,47(3):657-668

The precision and accuracy of ⁴⁰Ar/³⁹Ar dates are ultimately linked to co-irradiated reference materials of known age. Here we provide new data from the SK01 sanidine, which was analysed in three different laboratories to evaluate it as a ⁴⁰Ar/³⁹Ar reference material. Aliquots of 5 mg, incrementally heated in two laboratories, yielded indistinguishable results with a weighted mean age of 27.58 ± 0.06 Ma (95% confidence level). Single-crystal step heating and single-crystal total fusion analyses of SK01 sanidine were undertaken in the third laboratory to further test the intracrystalline homogeneity. For the seven step-heating analyses, six crystals yielded nearly concordant age spectra with ⁴⁰Ar/³⁹Ar ages ranging from 26.853 ± 0.094 Ma to 26.963 ± 0.067 Ma, whereas one crystal gave an older age of 27.774 ± 0.071 Ma with a slightly discordant age spectrum. Twenty-three single-crystal total fusion analyses yielded ⁴⁰Ar/³⁹Ar ages ranging from 27.070 ± 0.108 Ma to 27.736 ± 0.062 Ma with a dispersion of ~ 3.8%. The older ages from single-crystal total fusion dates are interpreted to reflect an inherited or excess argon component in some crystals. This is an initial characterisation of the SK01 sanidine, and additional work needs to be conducted to further evaluate the age dispersion so that it can be utilised as a ⁴⁰Ar/³⁹Ar reference material.  相似文献