Preface to Special Issue ‘Insights on the vertebrate paleontology of the Neuquén Group,Argentina’     

《Cretaceous Research》2018

  相似文献   

Axial convergence in a well-mixed estuary     

R.A. Nunes  J.H. Simpson 《Estuarine, Coastal and Shelf Science》1985,20(5):637-649

Transverse secondary circulations involving surface convergence, observed in a well-mixed estuary in North Wales, are made visible by the collection of surface material along an axial line which extends continuously for many kilometres through the estuary. The circulation and axial convergence, however, are seen only during the flood phase of the tide and no similar behaviour has been observed during the ebb phase.Convergent circulations in the estuary are associated with small but steady transverse density gradients in the cross-section, produced by non-uniform advection of the longitudinal gradient through the channel. A diagnostic model, using measured mean distributions of cross-sectional density, indicates surface transverse velocities (～0.1 ms^?1) similar to those observed in the estuary. The model further predicts appreciable transverse divergent currents at a fractional depth of 0.75: a prediction which has been tested in the estuary using a vertical array of accurately resolving current direction indicators.  相似文献   

The D-CIXS X-ray mapping spectrometer on SMART-1     

M Grande  R BrowningN Waltham  D ParkerS.K Dunkin  B KentB Kellett  C.H PerryB Swinyard  A PerryJ Feraday  C HoweG McBride  K PhillipsJ Huovelin  P MuhliP.J Hakala  O VilhuJ Laukkanen  N ThomasD Hughes  H AlleyneM Grady  R LundinS Barabash  D BakerP.E Clark  C.D MurrayJ Guest  I CasanovaL.C d'Uston  S MauriceB Foing  D.J Heather  V FernandesK Muinonen  S.S RussellA Christou  C OwenP Charles  H KoskinenM Kato  K SipilaS Nenonen  M HolmstromN Bhandari  R ElphicD Lawrence 《Planetary and Space Science》2003,51(6):427-433

The D-CIXS Compact X-ray Spectrometer will provide high quality spectroscopic mapping of the Moon, the primary science target of the ESA SMART-1 mission. D-CIXS consists of a high throughput spectrometer, which will perform spatially localised X-ray fluorescence spectroscopy. It will also carry a solar monitor, to provide the direct calibration needed to produce a global map of absolute lunar elemental abundances, the first time this has been done. Thus it will achieve ground breaking science within a resource envelope far smaller than previously thought possible for this type of instrument, by exploiting two new technologies, swept charge devices and micro-structure collimators. The new technology does not require cold running, with its associated overheads to the spacecraft. At the same time it will demonstrate a radically novel approach to building a type of instrument essential for the BepiColombo mission and potential future planetary science targets.  相似文献   

First large urban gasfield in China was established in Chengdu     

Daxing Wang  Jinghuai Gao  Youming Li  Zhengyuan Xia  Baojiang Wang 《应用地球物理》2004,1(1):25

  相似文献   

Southern Hemisphere Early Cretaceous (Valanginian-Early Barremian) carbon and oxygen isotope curves from the Neuquén Basin,Argentina     

《Cretaceous Research》2008,29(1):87-99

The first carbon and oxygen isotope curves for the Valanginian to Early Barremian (Early Cretaceous) interval obtained from outcrops in the Southern Hemisphere are presented. They were obtained from well-dated (by ammonites) sediments from the Neuquén Basin, Argentina. Measurements were acquired by the innovative method of analysing fossil oyster laminae. The occurrence of the well-established mid-Valanginian positive carbon isotope excursion is documented, while less well-marked positive events may also correlate with peaks identified in the well-known successions of SE France. The mid-Valanginian positive carbon isotope event in the Neuquén Basin is possibly associated with organic-rich sediments. A similar relationship is seen in the European Alps and in oceanic cores in some areas of the world.  相似文献   

Li-Sr-Nd isotope signatures of the plume and cratonic lithospheric mantle beneath the margin of the rifted Tanzanian craton (Labait)   总被引：3，自引：2，他引：1  

Sonja Aulbach  Roberta L. Rudnick  William F. McDonough 《Contributions to Mineralogy and Petrology》2008,155(1):79-92

Lithium concentrations and isotopic compositions of olivine and ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd of coexisting clinopyroxene from peridotite xenoliths from the Quaternary Labait volcano, Tanzania, document the influence of rift-related metasomatism on the ancient cratonic mantle. Olivines show negative correlations between Fo content and both δ⁷Li and Li concentrations. Olivines in iron-rich peridotites (Fo_85–87) have high Li concentrations (3.2–4.8 ppm) and heavy δ⁷Li (+5.2 to +6.6). In contrast, olivines in ancient, refractory peridotites have lower Li concentrations (∼2 ppm) and relatively light δ⁷Li (+2.6 to +3.5). This reflects mixing between ancient, refractory cratonic lithosphere and asthenosphere-derived rift magmas. A uniquely fertile, deformed, high-temperature garnet lherzolite, interpreted to be from the base of the lithosphere, has a ⁸⁷Sr/⁸⁶Sr of 0.7029 and ¹⁴³Nd/¹⁴⁴Nd of 0.51286, similar to HIMU oceanic basalts. It provides the best estimate of the Sr–Nd isotope composition of the upwelling mantle (i.e., plume, sensu lato) underlying this portion of the East African Rift, and is slightly less radiogenic compared to previous estimates of the plume that were based on rift basalts. Although elevated δ⁷Li are not exclusive to HIMU source regions, the data collectively indicate that the plume beneath Labait has HIMU characteristics in Sr, Nd and Li isotope composition. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Shale basins,sulfur-deficient ore brines and the formation of exhalative base metal deposits     

Fernando Tornos  Christoph A. Heinrich 《Chemical Geology》2008,247(1-2):195-207

The massive sulfide deposits of the Iberian Pyrite Belt are interbedded with felsic volcanic rocks and shale, and underlain by several thousand meters of siliciclastic sedimentary rocks known as the PQ Group. Isotope geochemistry and regional geology are both consistent with equilibration of the ore-forming fluids with the PQ Group, prior to ore deposition near the former seafloor. The average Cu:Zn:Pb ratio of the PQ Group rocks (ca. 26:55:19) is similar to the weighted average of all the massive sulfide orebodies combined (ca. 25:52:23).The genetic relationship between massive sulfide deposits and a siliciclastic sedimentary metal source is explained here by a thermodynamic model, proposing that mildly reducing redox conditions imposed by equilibration with the sedimentary rocks are most critical for the formation of an effective ore-forming fluid. Relatively metal-rich but organic-poor pyrite-bearing shale undergoing dewatering of saline pore fluids is an effective source for the generation of sulfur-deficient but relatively iron and base metal-rich brines. Thus, we propose that the giant deposits of the Iberian Pyrite Belt owe their existence not to exceptionally metal-enriched (e.g., magmatic) fluids, but to the existence of a fairly ordinary but large metal source in reactive siliciclastic sediments, combined with an underlying igneous heat source and a particularly efficient mechanism of sulfide precipitation by mixing with H₂S-rich fluids at or near the seafloor.Essentially similar mineral equilibria are imposed when saline fluids are buffered by typical continental basement rocks. Leaching of retrograde minerals and possibly residual salts from their magmatic or metamorphic prehistory is expected to generate similar, variably metal-rich but relatively sulfide-deficient fluids. Thus, the existence of mildly reducing rocks can be the dominant chemical control in the source of fluids generating many volcanogenic, Irish-type or sedex deposits, many of which are known to precipitate their metal load in response to biogenic sulfide addition at the ore deposition site.  相似文献   

A submarine canyon conduit under typhoon conditions off Southern Taiwan     

《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(2):223-240

The function of a submarine conduit under typhoon conditions is examined. The study site is the Kao-ping river, shelf, and submarine canyon (KPRSC) system located off southern Taiwan on a wave-dominated microtidal coast. The head of the canyon is located approximately 1 km off the river mouth. Two comprehensive 1-month field experiments were carried out in 2000 and 2002 during the flood season of the river. Both experiments encountered typhoons that generated significant river discharge and wave resuspension events. Particle samples collected in 2000 by sediment-traps were analyzed for coarse fraction by the wet sieving method. Among the coarse fraction, foraminiferal species and their abundance were recorded as a tracer for biogenic particles of marine origin. Stable isotopes of carbon (δ¹³C) of organic particles of sediment-trap samples were analyzed as a tracer for particles of terrestrial origin. All the measured flow and particle concentration records were analyzed by conventional time-series analytical methods. Simultaneously observed records of suspended sediment concentration at the river mouth and the volume concentration of suspended particles near the canyon floor were compared. Instantaneous flux and cumulative transport of suspended particles near the canyon floor were estimated during the deployment period. Results show that Kao-ping Submarine Canyon is a multi-level and process-dependant two-way conduit for particles of terrestrial and marine origins. In general, terrestrial signals are stronger than the marine signals in sediment-trap samples near the head of the canyon. During typhoon events, in the early distal phase of their influence nonlithogenic and biogenic marine sources are enhanced; in the later proximal phase signals of locally generated terrestrial lithogenic sources are enhanced. An episode of momentary downcanyon flushing of suspended particles near the canyon floor is observed during one typhoon occurrence. This flushing suggests nondeposition during the typhoon at the locale of deployment despite increased input of particles to the canyon floor. It also suggests a mechanism by which turbidity currents could be triggered. Yet, this flushing phenomenon is not observed in another typhoon occurrence, suggesting it is not universal in the canyon's response to the typhoon.  相似文献   

Implementing integrated oceans management: Australia's south east regional marine plan (SERMP) and Canada's eastern Scotian shelf integrated management (ESSIM) initiative     

《Marine Policy》2005,29(5):391-405

Integrated oceans management (IOM) is emerging in the international arena as a tool in meeting requirements for sustainable use of ocean space and marine resources. Australia and Canada are at the forefront of these developments and, being without set precedents, each state has adopted quite different strategies to implement IOM—Australia adopting a policy-driven approach delivered through Regional Marine Plans and Canada developing legislation that provided a framework for policy implementation delivered through an Integrated Management Framework. Despite these significant differences, examination of initiatives in both states indicates that there are also significant commonalities and shared experiences, providing important lessons for implementing IOM.  相似文献   

A study of particle exchange at the sediment–water interface in the Benguela upwelling area based on 234Th/238U disequilibrium     

《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(11):1742-1761

The natural isotope ²³⁴Th is used in a small-scale survey of particle transport and exchange processes at the sediment–water interface in the Benguela upwelling area. Results from water and suspended particulate matter (SPM) samples from the uppermost and lowermost water column as well as the underlying sediment of three stations are compared. The stations are situated in different sedimentological environments at 1200–1350 m water depth at the continental slope off Namibia. Highly differing extent and particle content of the bottom nepheloid layer (BNL) are determined from transmissometer data. Three models are presented, all explaining the ²³⁴Th depletion of the BNL and ²³⁴Th excess of the surface sediment that were observed. While the first model is based solely on local resuspension of surface sediment particles, the second evaluates the influence of vertical particle settling from the surface waters on the ²³⁴Th budget in the BNL. The third model explains ²³⁴Th depletion in the BNL by sedimentation of particles that were suspended in the BNL during long-range transport. Particle inventory of the BNL is highest at a depocenter of organic matter at 25.5°S, where strong deposition is presently taking place and lateral particle transport is suggested to predominate sediment accumulation. This is supported by the high settling flux of particles out of the BNL into the sediments of the depocenter, exceeding the vertical particle flux into sediment traps at intermediate depth in the same area by up to an order of magnitude. High particle residence/removal times in the BNL above the depocenter in the range of 5–9 weeks support this interpretation. Comparison with carbon mineralization rates that are known from the area reveals that, notwithstanding the large fraction of advected particles, organic carbon flux into the surface sediment is remineralized to a large extent. The deployment of a bottom water sampler served as an in situ resuspension experiment and provided the first data of ²³⁴Th activity on in situ resuspended particles. We found a mean specific activity of 86 disintegrations per minute (dpm) g⁻¹ (39–339 dpm g⁻¹), intermediate between the high values for suspended particles (in situ pump: 580–760 dpm g⁻¹; CTD rosette: 870–1560 dpm g⁻¹) and the low values measured at the sediment surface (26–37 dpm g⁻¹). This represents essential information for the modeling of ²³⁴Th exchange processes at the sediment–water interface.  相似文献