Time-series analysis of six whale-fall communities in Monterey Canyon,California, USA     

Lonny Lundsten  Kyra L. Schlining  Kaitlin Frasier  Shannon B. Johnson  Linda A. Kuhnz  Julio B.J. Harvey  Gillian Clague  Robert C. Vrijenhoek 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(12):1573-1584

Dead whale carcasses that sink to the deep seafloor introduce a massive pulse of energy capable of hosting dynamic communities of organisms in an otherwise food-limited environment. Through long-term observations of one natural and five implanted whale carcasses in Monterey Canyon, CA, this study suggests that: (1) depth and related physical conditions play a crucial role in species composition; (2) the majority of species in these communities are background deep-sea taxa; and (3) carcass degradation occurs sub-decadally. Remotely operated vehicles (ROVs) equipped with studio quality video cameras were used to survey whales during 0.8 to seven year periods, depending on the carcass. All organisms were identified to the lowest possible taxon. Community differences among whale-falls seemed to be most strongly related to depth and water temperature. The communities changed significantly from initial establishment shortly after a carcass’ arrival at the seafloor through multiple years of steady degradation. The majority of species found at the whale-falls were background taxa commonly seen in Monterey Bay. While populations of species characterized as bone specialists, seep restricted, and of unknown habitat affinities were also observed, sometimes in great abundance, they contributed minimally to overall species richness. All whale carcasses, shallow and deep, exhibited sub-decadal degradation and a time-series of mosaic images at the deepest whale site illustrates the rapidity at which the carcasses degrade.  相似文献   

Neutron Activation Analysis Applied to the Determination of Heavy Metals and Other Trace Elements in Sediments from Sepetiba Bay (RJ), Brazil     

Fàbio Pellegatti  Ana M.G. Figueiredo  Julio C. Wasserman 《Geostandards and Geoanalytical Research》2001,25(2-3):307-315

In this work, instrumental neutron activation analysis (INAA) was applied to the determination of the elements As, Ba, Br, Ce, Co, Cr, Cs, Eu, Fe, Hf, La, Lu, Nd, Rb, Sc, Sm, Ta, Tb, Th, U, Yb, Zn in twenty eight bottom sediment samples from Sepetiba Bay, Rio de Janeiro, Brazil. With the concentration data obtained, contour maps were prepared, by using Kriging method, to show the spatial distribution of the studied elements in the Bay. The elements Co, Cr, Cs, Fe, Sc, Ta and Zn showed similar behaviour in the sediments, with higher concentrations along the northern coast of the bay, where the fluvial water inputs are concentrated. The distribution of U, rare earth elements and Ba in the Bay indicates that these elements are not deposited as contaminants.  相似文献   

Nomospace and genospace: A spatial matrix     

Paulo Cesar da Costa Gomes 《GeoJournal》2004,60(4):339-344

We are concerned here with the notion of space as a primary condition for building social relations. From this stand, we have created two analytical matrixes that can help us characterize two modes: that of ‘being-there-in-space’ and that of ‘being-of-the-space’; the nomospace and the genospace. While the nomospace is characterized by ‘cold’ connotations, which are ideally defined as a result of a logical option, the genospace is mainly characterized by emotional or ‘warm’ connotations, which originate from a feeling of shared nature and common destiny. We believe that these matrixes could help us to identify the meanings of some behaviours and, therefore, make us more capable of interpreting many dynamics that occur in modern societies. The importance of geography is justified by the existing relationship between these behaviours and their proper spatial form. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Geology, Geochemistry and U-Pb SHRIMP Age of the Tacloban Ophiolite Complex, Leyte Island (Central Philippines): Implications for the Existence and Extent of the Proto-Philippine Sea Plate     

Leilanie O. Suerte    Graciano P. Yumul  Jr  Rodolfo A. Tamayo  Jr  Carla B. Dimalanta    Mei-Fu Zhou  René C. Maury    Mireille Polvé  Cesar L. Balce 《Resource Geology》2005,55(3):207-216

Abstract. The oceanic basement of the Central Philippines is exposed in ophiolitic massifs the age and origin of which remain debated. The Tacloban Ophiolite Complex (TOC) outcrops as a NW-SE trending massif in the northeastern portion of Leyte Island, Central Philippines. It is unconformably overlain by sedimentary sequences dated to Late Miocene-Pliocene and Pleistocene volcaniclastic deposits on its eastern and western flanks, respectively. Field, petrographic and trace element data suggest a subduction-related origin for this ophiolite. Sensitive High Resolution Ion Microprobe (SHRIMP) U-Pb dating of zircons from a gabbro yielded Early Cretaceous magmatic age for the TOC, which is very much older than a previously reported whole rock K-Ar derived Eocene age. The Early Cretaceous age of the TOC limits its possible progenitor to the proto-Philippine Sea Plate. Correlation with other Cretaceous ophiolites in Central Philippines reveals the possible extent of the proto-Philippine Sea Plate remnants now exposed onland.  相似文献   

U–Pb SHRIMP zircon dating of Grenvillian metamorphism in Western Sierras Pampeanas (Argentina): Correlation with the Arequipa-Antofalla craton and constraints on the extent of the Precordillera Terrane     

Cesar Casquet  Robert J. Pankhurst  C. Mark Fanning  Edgardo Baldo  Carmen Galindo  Carlos W. Rapela  Jose M. Gonzlez-Casado  Juan A. Dahlquist 《Gondwana Research》2006,9(4):524-529

Metamorphism of Grenvillian age (ca. 1.2 Ga; U–Pb zircon dating) is recognized for the first time in the Western Sierras Pampeanas (Sierra de Maz). Conditions reached granulite facies (ca. 780 °C and ca. 780 MPa). Comparing geochronological and petrological characteristics with other outcrops of Mesoproterozoic basement, particularly in the northern and central Arequipa-Antofalla craton, we suggest that these regions were part of a single continental crustal block from Mesoproterozoic times, and thus autochthonous or parautochthonous to Gondwana.  相似文献   

Hypsometric Curves as a Tool for Paleosurface Mapping     

Paulo Cesar Soares  Silvana Bressan Riffel 《Mathematical Geology》2006,38(6):679-695

A procedural paleosurface mapping tool, using hypsometric curves and digital elevation models, was developed and applied to three hydrographic basins that erode common areas in the coastal ranges of Brazil, in southeastern South America. The method consists of identifying areas favorable for the occurrence of paleosurfaces and their corresponding surficial formations as correlated to specific erosion events. Attributes from hypsometric curves, and logarithmic functions fitted to proper curve segments, are combined with common morphometric properties of paleosurfaces given a set of criteria. Zones satisfying the criteria are mapped as pertaining to specific paleosurfaces. Field survey confirms the agreement between predicted and observed occurrence and absence of paleosurfaces.  相似文献   

Rock-avalanche dynamics: insights from granular physics experiments   总被引：1，自引：0，他引：1  

S. Julio Friedmann  N. Taberlet  W. Losert 《International Journal of Earth Sciences》2006,95(5):911-919

Rock avalanches are known to behave in extraordinary ways unlike other landslides, and their deposits in part reflect their unusual physical behavior. Recent experiments in granular physics suggest that many phenomena and features simply reflect the non-linear nature of granular flows, although some behavior cannot simply be reproduced in lab scale experiments. In a static configuration, grain–grain contact networks dominate the distribution of forces and stresses within a granular mass. During flow, granular collisions damp the system through energy dissipation, while gravitational potential drives the system. The energy distribution between static and collisional stresses within the system can change very rapidly. Threshold events dominate system response, and the challenge is to find which characterization of the static phase helps to predict failure (and thus flow) resistance. Once flowing, many “unusual” rock-avalanche phenomena are entirely consistent with the physics of flow of large granular masses, but the low energy dissipation rate required for long run-out events requires the presence of physical processes that are not involved in experimental flows in the current parameter range or in the assumptions of current models.  相似文献   

Large-eddy Simulation of the Dispersion of Solid Particles in a Turbulent Boundary Layer   总被引：2，自引：2，他引：2  

Ivana Vinkovic  Cesar Aguirre  Michel Ayrault  Serge Simoëns 《Boundary-Layer Meteorology》2006,121(2):283-311

A large-eddy simulation (LES) with the dynamic Smagorinsky-Germano subgrid-scale (SGS) model is used to study the dispersion of solid particles in a turbulent boundary layer. Solid particles are tracked in a Lagrangian way. The instantaneous velocity of the surrounding fluid is considered to have a large-scale part (directly computed by the LES) and a small-scale part. The SGS velocity of the surrounding fluid is given by a three-dimensional Langevin model written in terms of SGS statistics at a mesh level. An appropriate Lagrangian correlation time scale is considered in order to include the influences of gravity and inertia of the solid particle. Inter-particle collisions and the influence of particles on the mean flow are also taken into account. The results of the LES are compared with the wind-tunnel experiments of Nalpanis et al. (1993 J Fluid Mech 251: 661–685) and of Tanière et al. (1997 Exp in Fluids 23:463–471) on sand particles in saltation and in modified saltation, respectively.  相似文献   

Analysis of a kinematic self‐centring seismic isolator     

Julio Pinochet  Juan C. de la Llera  C. Lüders 《地震工程与结构动力学》2006,35(12):1533-1561

This investigation deals with the analytical formulation and experimental validation of a prestressed reinforced concrete seismic isolator with kinematic constraints at both ends. The kinematic isolator was proposed initially as a low‐cost solution for seismic protection of low‐income people housing usually placed at the periphery of big cities where regular to bad soil conditions are common. So, the isolator is also a pile foundation with a central prestressed cable and two rolling steel surfaces at the top and bottom ends. By varying the shapes of the end rolling surfaces, different force–deformation constitutive relationships for the isolator may be obtained. Energy dissipation is introduced by yielding of passive reinforcement at the rolling interphase. Apart from stating the large‐deformation formulation of the element, several relevant aspects of the behaviour of these devices are studied herein, such as the increase in the tension of the central prestressed cable, responsible for the self‐centring action of the isolator, the floor uplift that results from the geometry of the isolator, and the vertical stability of the system. Experimental and theoretical results obtained for a group of 9 testing specimens show an excellent agreement in the force–deformation constitutive relationship. Although not the intent of this article, the device proposed may be extended directly as a coupling beam element for shear wall systems. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Global and local controls influencing the deposition of the La Luna Formation (Cenomanian-Campanian), western Venezuela     

Julio Perez-Infante  Paul Farrimond  Max Furrer 《Chemical Geology》1996,130(3-4):271-288

Bulk and molecular geochemical, micropalaeontological, and carbon-isotopic data are used to address the different local and global factors influencing the environment of sedimentation of the La Luna Formation (Cenomanian-Campanian, approximate palaeolatitude 15°N) in a single section in western Venezuela. Based on the constructed chronostratigraphic framework, oxygen-depleted bottom-water conditions and black-shale deposition started in western Venezuela well before the widespread occurrence of organic-rich sediments in higher palaeolatitude regions such as the Tethys and the North Atlantic near or at the Cenomanian-Turonian boundary. In the La Luna Formation, palaeoenvironmental conditions that allowed the preservation of organic matter (mainly of marine origin), prevailed until Santonian times in a distal platform facies with very low siliciclastic input. Changes in lithology appear to reflect the local response to eustatic sea-level variations and the presence of a migrating upwelling belt affecting the bioproductivity of silica and carbonate. A marked δ¹³C_org isotopic excursion is recognised in the middle part of the section, and is apparently unrelated to local palaeoenvironmental changes in bioproductivity and oxygen depletion. Biological marker data show no variations in association with the isotopic excursion, being mainly controlled by local fluctuations in organic-matter input and preservation.  相似文献