Apparent magnetic polarity reversals due to remagnetization resulting from late diagenetic growth of greigite from siderite     

Leonardo Sagnotti  rew P. Roberts  Richard Weaver  Kenneth L. Verosub  Fabio Florindo  Christopher R. Pike  Trevor Clayton  Gary S. Wilson 《Geophysical Journal International》2005,160(1):89-100

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Paleomagnetic constraints on the Plio–Pleistocene geodynamic evolution of the external central–northern Apennines (Italy)     

Leonardo Sagnotti  Aldo Winkler  Laura Alfonsi  Fabio Florindo  Fabrizio Marra 《Earth and Planetary Science Letters》2000,180(3-4):243-257

We report on new paleomagnetic results obtained from 27 sites sampled in the Plio–Pleistocene sequences at the external front of the central–northern Apennines. Previous analyses of Miocene (Messinian) sediments indicated that the present shape of the northern Apenninic arc is due to the oroclinal bending of an originally straight belt oriented around N320° and that vertical axis rotations accompanied the migration of the thrust fronts toward the Adriatic foreland [F. Speranza et al., J. Geophys. Res. 102 (1997) 3153–3166]. We tried to provide new paleomagnetic constraints for the timing and rates of the oroclinal bending process during the Pliocene and the Pleistocene. The results suggest that CCW rotations observed in the northern part of the studied area are possibly younger than 3 Ma. No regional rotation is recorded in the Pliocene and Pleistocene sediments from the southern part of the study area, analogously to the Messinian sediments of the ‘Acquasanta’ domain of Speranza et al. [F. Speranza et al., J. Geophys. Res. 102 (1997) 3153–3166]. A local significant CCW rotation (23°±10°) is identified in the Early Pleistocene sediments that crop out along the Adriatic coast between Ascoli and Pescara, indicating differential motion of the thrust sheets. This rotation must be younger than 1.43 Ma.  相似文献   

Geological constraints for earthquake faulting studies in the Colfiorito area (central Italy)     

Giuseppe Cello  Giovanni Deiana  Luca Ferelli  Leonardo Marchegiani  Laura Maschio  Stefano Mazzoli  Alessandro Michetti  Leonello Serva  Emanuele Tondi  Tiziano Vittori 《Journal of Seismology》2000,4(4):357-364

On September 26, 1997, at 00.33 h(GMT), a Mw 5.7 earthquake occurred in the axial zone of theUmbria-Marche Apennines of central Italy, in the Colfiorito basin area. At09.40 h (GMT), a M_w 6.0 earthquake again struck the area withinthe Colfiorito basin, a major intramontane basin filled with Quaternarycontinental deposits. The two main shocks, and the associated aftershockswere within a roughly NNW-SSE trending zone of largest damage (Imax10), in which ground deformation has been observed. Along this trend,Cello et al. (1997a) had mapped a few capable faults, showingtranstensional to pure extensional kinematics. Field inspection of themapped faults, carried out after the main shocks, revealed that some ofthem were locally reactivated (for lengths of several hundreds metres andsurface slip in the range of 2–8 cm) during the September 26, 1997earthquakes.  相似文献   

Spatio-temporal distribution of seismic activity during the Umbria-Marche crisis, 1997     

A. Deschamps  F. Courboulex  S. Gaffet  A. Lomax  J. Virieux  A. Amato  A. Azzara  B. Castello  C. Chiarabba  G.B. Cimini  M. Cocco  M. Di Bona  L. Margheriti  F. Mele  G. Selvaggi  L. Chiaraluce  D. Piccinini  M. Ripepe 《Journal of Seismology》2000,4(4):377-386

We present the spatio-temporal distribution of more than 2000 earthquakesthat occurred during the Umbria-Marche seismic crisis, between September 26and November 3, 1997. This distribution was obtained from recordings of atemporary network that was installed after the occurrence of the first two largest shocks (Mw =, 5.7, Mw = 6.0) of September 26. This network wascomposed of 27 digital 3-components stations densely distributed in theepicentral area. The aftershock distribution covers a region of about 40 km long and about2 km wide along the NW-SE central Apennines chain. The activity is shallow,mostly located at less than 9 km depth. We distinguished three main zonesof different seismic activity from NW to SE. The central zone, that containsthe hypocenter of four earthquakes of magnitude larger than 5, was the moreactive and the more complex one. Sections at depth identify 40–50^°dipping structures that agree well with the moment tensor focalmechanisms results. The clustering and the migration of seismicity from NW to SE and the generalfeatures are imaged by aftershock distribution both horizontally and at depth.  相似文献   

Bronze Age ceramics in southwest Spain: An exploratory archaeometric study of technology and function     

Angel Polvorinos del Río  Leonardo García Sanjun  Víctor Hurtado Prez  M. Jesús Hernndez Arnedo 《Geoarchaeology》2005,20(3):263-284

Pottery from the Bronze Age of southwest Spain has traditionally been approached from a “typological” stand seeking the establishment of chronological sequences. This article examines ceramics from two different Bronze Age sites, a settlement (El Trastejón) and a necropolis (La Traviesa), from an archaeometric viewpoint. The methodology involved includes mineralogical characterization by XRD and optical microscopy, chemical analysis by XRF, and morphometric analysis through digital processing of thin sections. The analytical results are contextualized within the general framework of our current archaeological knowledge of both sites and their general background, and then a preliminary interpretation is proposed in terms of the prehistoric technology of pottery manufacture and functionality. © 2005 Wiley Periodicals, Inc.  相似文献   

Luminescence dating of Late Pleistocene faults as evidence of uplift and active tectonics in Sardinia,W Mediterranean     

Leonardo Casini  Stefano Andreucci  Daniele Sechi  Chun‐Yuan Huang  Chuan‐Chou Shen  Vincenzo Pascucci 《地学学报》2020,32(4):261-271

Precise dating of the activity of Late Pleistocene to Holocene neo‐tectonic structures is crucial to quantify the rate of deformation in low‐seismicity regions. Sardinia is a relatively stable continental fragment set in the middle of the tectonically active Western Mediterranean belt. This paper provides evidences of significant uplift of northwest Sardinia that support an ongoing tectonic activity since the Marine Isotopic Stage 7 (MIS 7; ca. 220 ka). In particular, it documents for the first time Late Pleistocene to Holocene tectonics based on luminescence dating of travertine sealing a major NNE‐SSW fault.  相似文献   

Turbulent Flow Properties Around a Staggered Wind Farm     

Leonardo P. Chamorro  R. E. A. Arndt  Fotis Sotiropoulos 《Boundary-Layer Meteorology》2011,141(3):349-367

The fundamental properties of turbulent flow around a perfectly staggered wind farm are investigated in a wind tunnel. The wind farm consisted of a series of 10 rows by 2–3 columns of miniature wind turbines spaced 5 and 4 rotor diameters in the streamwise and spanwise directions respectively. It was placed in a boundary-layer flow developed over a smooth surface under thermally neutral conditions. Cross-wire anemometry was used to obtain high resolution measurements of streamwise and vertical velocity components at various locations within and above the wind farm. The results show that the staggered configuration is more efficient in terms of momentum transfer from the background flow to the turbines compared to the case of an aligned wind turbine array under similar turbine separations in the streamwise and spanwise directions. This leads to improved power output of the overall wind farm. A simplified analysis suggests that the difference in power output between the two configurations is on the order of 10%. The maximum levels of turbulence intensity in the staggered wind farm were found to be very similar to that observed in the wake of a single wind turbine, differing substantially with that observed in an aligned configuration with similar spacing. The dramatic changes in momentum and turbulence characteristics in the two configurations show the importance of turbine layout in engineering design. Lateral homogenization of the turbulence statistics above the wind farm allows for the development of simple parametrizations for the adjustment of flow properties, similar to the case of a surface roughness transition. The development of an internal boundary layer was observed at the upper edge of the wind farm within which the flow statistics are affected by the superposition of the ambient flow and the flow disturbance induced by the wind turbines. The adjustment of the flow in this layer is much slower in the staggered situation (with respect to its aligned counterpart), implying a change in the momentum/power available at turbine locations. Additionally, power spectra of the streamwise and vertical velocity components indicate that the signature of each turbine-tip vortex structure persists to locations deep within the wind farm.  相似文献   

Magnetic classification of stony meteorites: 1. Ordinary chondrites     

Pierre ROCHETTE  Leonardo SAGNOTTI  Michle BOUROT‐DENISE  Guy CONSOLMAGNO  Luigi FOLCO  Jrme GATTACCECA  Maria Luisa OSETE  Lauri PESONEN 《Meteoritics & planetary science》2003,38(2):251-268

Abstract— We present a database of magnetic susceptibility measurements on 971 ordinary chondrites. It demonstrates that this parameter can be successfully used to characterize and classify ordinary chondrite meteorites. In ordinary chondrites, this rapid and non‐destructive measurement essentially determines the amount of metal in the sample, which occurs in a very narrow range for each chondrite class (though terrestrial weathering can result in a variable decrease in susceptibility, especially in finds). This technique is particularly useful not only for a rapid classification of new meteorites, but also as a check against curation errors in large collections (i.e., unweathered meteorites, the measured susceptibility of which lies outside the expected range, may well be misclassified or misidentified samples). Magnetic remanence, related to magnetic field measurements around asteroids, is also discussed.  相似文献   

Strike-slip faults parallel to crustal spreading axes: data from Iceland and the Afar Depression     

Pietro Passerini  Marta Marcucci  Giovanni Sguazzoni  Leonardo Zan  Abdourahman Omar Haga 《地学学报》1991,3(6):607-618

Slickenside studies in regions of crustal spreading such as Iceland and the Afar Depression, East Africa, reveal that a significant number of faults parallel and close to rift axes are strike-slip rather than normal. Therefore, the pattern of brittle deformation in these regions does not conform to the classic two-dimensional schemes of oceanic tectonics and pre-oceanic rifting. Dip-slip and strike-slip faulting presumably alternated along or in the vicinity of spreading axes, indicate a varying stress field and a combination of transverse and longitudinal movements. In Iceland, strike-slip faults parallel to rifts are observed both west and east of the rift system as well as in a median area between overlapping rifts; the mechanisms proposed for their origin include accommodation of oblique convergence or divergence of crustal sections due to variations of spreading directions along axis and the interaction of overlapping rifts. In the Afar Depression this kind of fault is recorded west of the rift of Asal and can be imputed to reflect an interaction among rifts in the vicinity of the Afar triple junction. Rift-parallel strike-slip faults cannot however be assumed to be a feature of all crustal spreading axes due to the peculiarity of the examined regions: both of them are hot-spot areas and the Afar Depression lies at a triple junction.  相似文献   

Pennsylvanian glacimarine sedimentation in the Cushamen Formation,western North Patagonian Massif     

Paulo Marcos  Daniel A.Gregori  Leonardo Benedini  Mercedes Barros  Leonardo Strazzere  Cecilia Pavon Pivetta 《地学前缘(英文版)》2018,9(2):485-504

The metasedimentary sequence of the Cushamen Formation in the western North Patagonian Massif is540 m thick and comprises six sedimentary lithofacies associations related to a glacimarine environment.Four of these lithofacies represent distal glacimarine environments, whereas another one was deposited in proximal glacimarine environments, and the last includes subglacial environments. The organization and configuration of these lithofacies associations represent the advance and retreat of the glacier masses. The maximum glacial advance is correlatable with the G2 glacial interval of the Pennsylvanian Pampa de Tepuel, Las Salinas and Valley Chico, formations of the Extraandean Chubut, and the southern part of Neuquen Cordillera. Contemporaneously, in southern Chile there are marine and glacimarine sediments. The chronostratigraphic relationships between the Silurian to Permian units allow five paleogeographic stages to be distinguished. The middle Silurian-late Devonian igneous rocks represent the first magmatic stage. The second stage, which is transitional to the first, is represented by a marine basin that includes the late Devonian-early Carboniferous Esquel and Rio Pescado formations and the Llanquihue Complex. The third stage(early-late Carboniferous) includes granitoids of the second magmatic event that partially overlapped the first magmatic igneous belt. The fourth stage belongs to the late Carboniferous sedimentation of the Cushamen and equivalent formations. The extended early Permian magmatism was the last Paleozoic event in the studied area.  相似文献