Periodic orbits of the generalized Friedmann–Robertson–Walker Hamiltonian systems     

Jaume Llibre  Ammar Makhlouf 《Astrophysics and Space Science》2013,344(1):45-50

The averaging theory of first order is applied to study a generalization of the Friedmann–Robertson–Walker Hamiltonian systems with three parameters. We provide sufficient conditions on the three parameters of the generalized system to guarantee the existence of continuous families of periodic orbits parameterized by the energy, and these families are given up to first order in a small parameter.  相似文献   

Provenance-related characteristics of beach sediments around the island of Menorca, Balearic Islands (western Mediterranean)     

Lluís Gómez-Pujol  Francesc X. Roig-Munar  Joan J. Fornós  Pau Balaguer  Jaume Mateu 《Geo-Marine Letters》2013,33(2-3):195-208

The island of Menorca, one of the Balearic Islands (Spain) located in the western Mediterranean, is characterised by a contrasting geology and landscape with two major geographic domains: (1) a southern region called Migjorn, comprised of Late Miocene calcarenites and limestones, and (2) a northern region known as Tramuntana, which is composed of folded and faulted Palaeozoic, Mesozoic and Tertiary (Oligocene) siliceous and calcareous rocks. Both domains are lined by numerous pocket beaches exhibiting a high variety of surficial sediment assemblages. Grain-size and compositional analyses revealed that cliff erosion and nearshore Posidonia oceanica meadows are the main sources of sediments consisting mostly of medium- to coarse-grained carbonate sands of marine biogenic origin, with variable amounts of terrigenous rock fragments and quartz. Based on distinctly different contributions of bioclastic material, biogenic carbonates and quartz, 320 sediment samples from 64 beaches were grouped into different facies associations dominated by either (1) biogenic sands, (2) biogenic sands with terrigenous contributions or (3) terrigenous sands with quartz. Nevertheless, there is a marked regional variability in sediment texture and composition. Thus, variable mixtures of carbonate and siliciclastic sediments characterise the beaches of the northern region, whereas the beaches of the southern region are composed mostly of carbonate sands of marine biogenic origin. An exception is the central sector of the south coast, which is enriched in quartz sand (~10 %); this can be related to outcrops of quartz-rich basement rock and also to rocks exposed in some northern drainage basins captured by southern streams since the Plio-Quaternary.  相似文献   

Magnetostratigraphic and cyclostratigraphic calibration of a prospective Palaeocene/Eocene stratotype at Zumaia (Basque Basin, northern Spain)     

Jaume Dinarès-Turell  Juan Ignacio Baceta  Victoriano Pujalte  Xabier Orue-Etxebarria  Gilen Bernaola 《地学学报》2002,14(5):371-378

ABSTRACT Detailed magnetostratigraphic work at the Palaeocene/Eocene boundary interval in the Zumaia section has led to a precise delineation of the position of polarity Chron C25n from −35.0 m (or −35.7 m) to −25.2 m below the base of the Carbon Isotopic Excursion that marks the Palaeocene/Eocene boundary. This chronostratigraphic constraint suggests that the lithological carbonate–marl couplets making up most of the studied section are the expression of orbital precession cycles, and confirms the expanded and continuous nature of the section, with mean sediment accumulation rates of ∼ 2.5 cm kyr⁻¹. The new data render Zumaia a unique land-based marine section with available magnetostratigraphic data coupled to cyclostratigraphy. The revised chronostratigraphic framework presented supports previous cyclostratigraphic calibration of the latest Palaeocene geomagnetic timescale; it should facilitate better assessment of the different chemobiostratigraphic events that span this critical interval as a consequence of past climate and oceanographic change. Consequently, the Zumaia section is proposed as a candidate Global Stratotype Section and Point (GSSP) for the Palaeocene/Eocene boundary.  相似文献   

Effects of anisotropy on the two-dimensional inversion procedure     

Wiebke Heise  Jaume Pous 《Geophysical Journal International》2001,147(3):610-621

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A deformed Pliocene-Quaternary alluvial and red paleosol succession in the Eastern Betics: Paleomagnetic,rock-magnetic and sedimentological pilot study     

Jaume Dinarès-Turell  Pedro Alfaro  Jesús Soria 《Studia Geophysica et Geodaetica》1995,39(4):405-419

Summary An integrated pilot paleomagnetic and sedimentological study has been conducted in the Neogene-Quaternary infilling materials of the Bajo Segura Basin (Eastern Betics, SE Spain). The studied sediments belong to the youngest (late Pliocene-Quaternary) lithostratigraphic unit of the basin (P-Q unit). The statistical analysis of tectonic striations and stylolitic dissolutions on the conglomerate limestone clasts indicates a NNW-SSE maximum compression direction. This is in accordance with the principal susceptibility axes, determined from the anisotropy of magnetic susceptibility measurements (AMS) of the interbedded siltstones where the Kmax axis group in a subhorizontal N 080° E direction.A total of 45 core samples have been collected from 16 stratigraphic siltstone levels encompassing the described section at Crevillente with the aim to establish a magnetochronology. Upwards in the section the NRM intensity and bulk susceptibility vary from 10^–2 to 10^–3 A/m and from 1550 to 100 × 10^–6 SI, respectively. The mean characteristic remanent magnetization (ChRM) after bedding correction (Dec/Inc = 10°/60°, ₉₅ = 8.7°, k = 15.9) is deviated slightly towards the E from the reference N direction, and could reflect a deflection related to the observed magnetic fabric although no clear correlation exists with AMS parameters. The derived magnetostratigraphy reveals only one reversal boundary within the upper third of the section, delimiting an upper reversal magnetozone which has been tentatively correlated with the Olduwai subchron close to the Plio-Pleistocene boundary.Pilot and preliminary rock-magnetic experiments and standard X-ray difraction (XRD) analysis have been performed on typical samples in order to establish the carriers of magnetization and characterize the sedimentological and magnetic-acquisition processes in these sediments. Magnetic carriers seem to be dominated by magnetite with a relative grain size within the PSD state (pseudo single-domain) threshold, but closer to the MD (multi domain) threshold, which favours the detrital origin for the magnetite.  相似文献   

Anomalous phases exceeding 90° in magnetotellurics: anisotropic model studies and a field example     

Wiebke Heise  Jaume Pous 《Geophysical Journal International》2003,155(1):308-318

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Generation of earth stratified models compatible with both ellipticity and phase velocity observations of Rayleigh waves     

Jaume Pous  Xavier Lana  Antoni M. Correig 《Pure and Applied Geophysics》1985,123(6):870-881

In the eigenvalue eigenvector decomposition used in inversion techniques, we can sometimes obtain eigenvalues close to zero. Related to these eigenvalues close to zero, a set of stratified earth models is generated. These are compatible with the theoretical observations according to a given model. The method is applied to ellipticities and phase velocities of Rayleigh waves, and supply proof of the advantage of working with both sets of data together.  相似文献   

Volume contents     

Manuel Falconi  Ernesto A. Lacomba  Jaume Llibre 《Celestial Mechanics and Dynamical Astronomy》2000,77(4):325-326

Volume Contents

Volume contents  相似文献