Diagenetic evolution of lower Jurassic platform carbonates flanking the Tazoult salt wall (Central High Atlas,Morocco)     

Mar Moragas  Vinyet Baqués  Anna Travé  Juan Diego Martín-Martín  Eduard Saura  Gregoire Messager  David Hunt  Jaume Vergés 《Basin Research》2020,32(3):546-566

Platform carbonates diagenesis in salt basins could be complex due to potential alterations of fluids related and non-related to diapirism. This paper presents the diagenetic history of the Hettangian to Pliensbachian platform carbonates from the Tazoult salt wall area (central High Atlas, Morocco). Low structural relief and outcrop conditions allowed to define the entire diagenetic evolution occurred in the High Atlas diapiric basins since early stages of the diapiric activity up to their tectonic inversion. Precipitation of dolomite and calcite from both warmed marine-derived and meteoric fluids characterised diagenetic stages during Pliensbachian, when the carbonate platforms were exposed and karstified. Burial diagenesis occurred from Toarcian to Middle Jurassic, due to changes of salt-induced dynamic related to increase in siliciclastic input, fast diapir rise and rapid burial of Pliensbachian platforms. During this stage, the diapir acted as a physical barrier for fluid circulation between the core and the flanking sediments. In the carbonates and breccias flanking the structures, dolomite and calcite precipitated from basinal brines, whereas carbonate slivers located in the core of the structure, were affected by the circulation of Mn-rich fluids. The final diagenetic event is characterised by the income of meteoric fluids into the system during uplift caused by Alpine orogeny. These results highlight the relevant influence of diapirism on the diagenetic modifications in salt-related basins in terms of diagenetic events and involved fluids.  相似文献   

Stratigraphic framework of the thrust geometry and structural inversion in the southeastern Pyrenees : La Garrotxa area     

Albert Martinez  Jaume Vergés  Eduard Clavell  John Kennedy 《Geodinamica Acta》2013,26(3):185-194

Abstract

The structure of la Garrotxa area within the Cadi unit (south-eastern Pyrenees) consists of a set of duplexes at different scales which repeat the different carbonatic litho-units of the Lower and Middle Eocene. These duplexes are folded by antiformal stacks structures with basement rocks in their cores. The north boundary of these antiformal stacks represents an inversion of pre-existent extensional faults which formed half-graben geometries. The basement rocks involved in the structure represent short-cuts formed in the footwall of the extensional faults. All thrusts of La Garrotxa area branch with the upper Garrotxa thrust. The more complex structure of La Garrotxa area than the adjacent areas within the Cadí unit, is due to the initial complex synsedimentary geometry of the sedimentary pile.

The Cadi unit overlies the Serrat unit with a hangingwall ramp geometry. This unit was deduced from the Serrat-1 well, drilled in 1987. The Serrat unit is made up of a Middle Eocene evaporitic sequence, with alternating shales and anhydrites and a 100 meters thick salt layer close to the top. The total thickness of this evaporitic Beuda sequence is 1 000 meters. The Beuda sequence clearly controlled the thrust geometry of the younger thrusts.  相似文献   

The Last Pterosaurs: First Record from the Uppermost Maastrichtian of the Tremp Syncline (Northern Spain)     

DALLA VECCHIA Fabio M.  RIERA Violet  OMS Josep Oriol  DINARèS-TURELL Jaume  GAETE Rodrigo  GALOBART Angel 《《地质学报》英文版》2013,87(5):1198-1127

Pterosaur bones are for the first time reported from the Tremp Syncline(Spain) and the southern Pyrenees.They come from the Torrebilles-2 site(Isona,Lleida Province) in the upper Maastrichtian part of the Tremp Formation,which falls within the C29r magnetochron.Fragmentary long bones are referred to the Pterosauria based on their cortical thinness,micro-architecture,and histological features.They belong to very large to possibly giant individuals.The most complete specimen is possibly a partial right femur.The review of the Maastrichtian pterosaur record shows that only a few specimens can be referred to the C29r(which contains the K/Pg boundary).The identification of fragmentary remains could improve our knowledge about the abundance and distribution of these flying sauropsids just before the end-Cretaceous mass extinction.  相似文献   

Periodic orbits and non-integrability of Armbruster-Guckenheimer-Kim potential     

Jaume Llibre  Luci Roberto 《Astrophysics and Space Science》2013,343(1):69-74

In this paper we study the periodic orbits of the Hamiltonian system with the Armburster-Guckenheimer-Kim potential and its $\mathcal{C}^{1}$ non-integrability in the sense of Liouville-Arnold.  相似文献   

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   

Compressed sensing imaging techniques for radio interferometry     

Y. Wiaux  L. Jacques  G. Puy  A. M. M. Scaife  P. Vandergheynst 《Monthly notices of the Royal Astronomical Society》2009,395(3):1733-1742

Radio interferometry probes astrophysical signals through incomplete and noisy Fourier measurements. The theory of compressed sensing demonstrates that such measurements may actually suffice for accurate reconstruction of sparse or compressible signals. We propose new generic imaging techniques based on convex optimization for global minimization problems defined in this context. The versatility of the framework notably allows introduction of specific prior information on the signals, which offers the possibility of significant improvements of reconstruction relative to the standard local matching pursuit algorithm CLEAN used in radio astronomy. We illustrate the potential of the approach by studying reconstruction performances on simulations of two different kinds of signals observed with very generic interferometric configurations. The first kind is an intensity field of compact astrophysical objects. The second kind is the imprint of cosmic strings in the temperature field of the cosmic microwave background radiation, of particular interest for cosmology.  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