Remanent magnetization of andesitic and dacitic pumice from the 1985 eruption of Nevado del Ruiz (Colombia) reversed due to self-reversal     

Maja Haag  Friedrich Heller  Juan Carlos Carracedo  Vicente Soler 《Journal of Volcanology and Geothermal Research》1990,41(1-4)

The natural remanent magnetization of andesitic pumice emitted during the 1985 eruption of the Nevado del Ruiz volcano (Colombia) has a direction opposite to the present geomagnetic field. The self-reversing mechanism can be re-activated in the laboratory during cycles of heating and subsequent cooling in air and zero magnetic field. Laboratory-produced thermoremanent magnetization is dominated by the same self-reversal process in fields up to several mT. Microchemical, optical and Curie temperature analyses indicate that the ferromagnetic minerals are members of the magnetite-ulvöspinel and hematite-ilmenite series with average compositions of Fe_2.73Ti_0.27O₄ and Fe_1.38Ti_0.62O₃, respectively. In analogy with the magnetic behaviour of synthetically grown antiferromagnetic-ferromagnetic FeMn-FeNi films, the self-reversal can probably be interpreted in terms of an exchange field acting between a Ti-poor canted antiferromagnetic and a Ti-rich ferrimagnetic phase in the hemoilmenite grains.  相似文献   

A comment on¹³C/¹²C in land snail shells—reply     

M. Magaritz  J. Heller 《Earth and Planetary Science Letters》1983,63(1):144-145

  相似文献   

The physical principles of rock magnetism: F. D. Stacey and S. K. Banerjee. Elsevier,Amsterdam, 1974, 195 pp., Dfl. 60.00     

F. Heller 《Marine Geology》1976,20(2):179-180

  相似文献   

Numerical simulations of interacting gas-rich barred galaxies: vertical impact of small companions     

I. Berentzen  E. Athanassoula  C. H. Heller  K. J. Fricke 《Monthly notices of the Royal Astronomical Society》2003,341(1):343-360

We investigate the dynamical effects of an interaction between an initially barred galaxy and a small spherical companion using an N -body/smoothed-particle-hydrodynamics algorithm. In the models described here the small companion passes through the disc of the larger galaxy nearly perpendicular to its plane. The impact positions and times are varied with respect to the phase of the bar and the dynamical evolution of the disc.
The interactions produce expanding ring structures, offset bars, spokes and other asymmetries in the stars and gas. These characteristic signatures of the interaction are present in the disc for about 1 Gyr. We find that in some cases it is possible to destroy the bar while keeping the disc structure. In general, the central impacts cause larger damage to the bar and the disc than the peripheral ones. The interaction tends to accelerate the transition from a strongly-barred galaxy to a weakly- or non-barred galaxy. The final disc morphology is determined more by the impact position relative to the bar rather than the impact time.  相似文献   

An efficient method of generating random permeability fields by the source point method     

Saleem G. Ghori  John P. Heller  Ashok K. Singh 《Mathematical Geology》1993,25(5):559-572

Aquifer properties, for example permeability and porosity, vary in space and may be characterized by their distributions. The property distribution is not totally random but shows some correlation structure. Because most of the values are not known, some rational method is required to generate credible aquifer distribution properties for inclusion in fluid transport models. This paper presents a numerically efficient method of generating geostatistical random fields, by the source Point Method (SPM). The SPM is a very efficient method and requires little computer time and relatively small data storage, as compared to other methods of generating random fields. In addition, the SPM is modified to include any desired amount of anisotropy in the property distribution of a system. By using conditional covariances, a formula for a two-dimensional anisotropic field is derived to prespecify the desired correlation length in any direction. Results show that for an anisotropic medium the correlation length can be pre-specified in any specific direction.  相似文献   

Mach's principle and bundle of geometric quantities     

M. Heller 《Astrophysics and Space Science》1975,32(2):L29-L31

It is shown that the bundle of geometric quantities σ(M) over a space-timeM is a strong anti-Machian element ofM.  相似文献   

A Furnace for Magnetic Investigations of Rocks     

Friedrich Heller  Henning Scriba  Max Weber 《Geophysical Journal International》1970,21(5):531-534

  相似文献   

保德阶层型剖面磁性地层学研究   总被引：18，自引：4，他引：14  

岳乐平  邓涛  张云翔  王建其  张睿  杨利荣  Heller 《地层学杂志》2004,28(1):48-51,63

古地磁测量表明 ,中国新近系保德阶界线层型 ,山西保德冀家沟剖面记录了 12个正极性段与 11个负极性段。上部黄土显示了正极性与负极性 ,记录了松山负反极性带的一部分 ;红色黏土与砂砾岩层记录了 Cande95古地磁极性年表中的 C2 An.1n,C2 An.2 n,C2 An.3n,C3n.1n,C3n.2 n,C3n.3n,C3n.4 n,C3An.1n,C3An.2 n,C3Bn,C4 n.1n,C4 n.2 n及其间负极性带。剖面红色黏土的地质年龄为 8.0 Ma— 3.0 Ma,包括了榆社期的早期和保德期的中、晚期。冀家沟保德阶剖面含有二层哺乳动物化石层 ,上化石层以含丰富的鹿科化石为特点 ,相当于含 4 9地点动物群的层位 ,年龄约 5 .5 0 Ma;下化石层相当于含 30地点动物群层位 ,古地磁年龄应当在 6 .5 Ma— 7.0 Ma之间。  相似文献   

New paleomagnetic results from Upper Cretaceous arc-type rocks from the northern and southern branches of the Neotethys ocean in Anatolia     

Cengiz Cinku  Mualla  Heller  Friedrich  Ustaömer  Timur 《International Journal of Earth Sciences》2017,106(7):2575-2592

International Journal of Earth Sciences - A paleomagnetic study of Cretaceous arc type rocks in the Central-Eastern Pontides and in the Southeastern Taurides investigates the tectonic and...  相似文献   

Fluvial stacking due to plate collision and uplift during the Early Pleistocene in Cyprus     

Wolfgang Schirmer  Josef Weber  Valerian Bachtadse  Marcelle BouDagher-Fadel  Friedrich Heller  Frank Lehmkuhl  Ioannis Panayides  Ursula Schirmer 《Central European Journal of Geosciences》2010,2(4):514-523

Southern Cyprus is situated within a mosaic terrane that has been fragmented between the northward drifting African and Arabian plates and the Eurasian plate. Enormous uplift of the earth mantle in the Tróodos Mountains is explained by two models. The subduction model explains subduction along the Cyprean arc to be the driving force for uplift whereas after the restraining bend model westward squeezing of Cyprus along strike-slip faulting is responsible for the enormous uplift at restraining bends. Since its emergence as an island in early Miocene times, landscape formation on Cyprus has been strongly controlled by this uplift. Until the Plio-Pleistocene, a strait belt separated the southern unroofed ophiolitic core region-the Tróodos Mountains-from the folded Kyrenia range to the north. This former sea basin, nowadays the Mesaoría Basin, is linked with the Tróodos Mountains by a dissected glacis with a thick cover of river deposits. The highest and oldest river deposits (Apalós Formation) were studied in the Vlokkariá hill southwest of Lefkosía. The 45.5 m thick Apalós Formation of Early Pleistocene age exhibits 24 sedimentary units (Fluviatile Series). Their magnetostratigraphical characters align with the Matuyama chron including the Olduvai and Jaramillo subchrons thus comprising about 1.15 Ma within the Early Pleistocene. This fluvial stack indicates a very flat and deeply lying river environment flowing from a slowly uplifting Tróodos hinterland. It happened during the end of Early Pleistocene when the enhanced Tróodos uplift started the dissection of the stacked river plain.  相似文献