Hebridean tholeiitic magmas: A geochemical study of the Ardnamurchan cone sheets     

J. G. Holland  G. M. Brown 《Contributions to Mineralogy and Petrology》1972,37(2):139-160

The Tertiary complex of doleritic cone sheets in Ardnamurchan has been sampled and a geochemical study made on 98 rock specimens by X-ray fluorescence analysis. A range in composition from 48 to 66% (wt.) SiO₂ is associated with, for example, an increase in Rb from 2 to 126 ppm, and a decrease in Ni from 86 to < 1 ppm. R-mode factor analysis indicates element groupings that are most easily related to a history of crystal fractionation beneath the central intrusive complex. No chemical basis can be found that would add support to either the two-centre or the spiral-fracture hypotheses relating to the disposition of the cone sheets. Plots of oxide and normative data show the Hebridean cone-sheet complex to have a tholeiitic character, which is compared with the Hawaiian tholeiitic and Hebridean alkalic series. A transitional nature for the two Hebridean series, compared with the two Hawaiian series, is probably related to derivation from an olivine basalt parent rather than from an olivine tholeiite as in Hawaii.  相似文献   

${}^{18}\text{O}{}^{16}\text{O}$ ratios in Luna 16 fines     

Marc Javoy  Jacqueline Marette  Françoise Pineau 《Geochimica et cosmochimica acta》1973,37(9):2017-2019

Partial fluorination experiments developed on a 26 mg sample of Luna 16 fines show a big ¹⁸O enrichment in the first oxygen evolved similar to those observed by Epstein and Taylor on Apollo samples and probably related to the high solar wind content of this sample.  相似文献   

Geochemical Effects of Magmatic Solitary Waves—I. Numerical Results     

Sarah Watson  Marc Spiegelman 《Geophysical Journal International》1994,117(2):284-295

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Geochemical Effects of Magmatic Solitary Waves—Ii. Some Analysis     

Marc Spiegelman 《Geophysical Journal International》1994,117(2):296-300

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Electrical resistivity model of the crust and upper mantle from a magnetotelluric survey through the central Pyrenees   总被引：2，自引：0，他引：2  

Jaume Pous  Juanjo Ledo  Alex Marcuello  Marc Daignières 《Geophysical Journal International》1995,121(3):750-762

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Suspension-feeding bivalves and the fate of primary production: An estuarine model applied to Chesapeake Bay   总被引：1，自引：0，他引：1  

Jeroen Gerritsen  A. Frederick Holland  David E. Irvine 《Estuaries and Coasts》1994,17(2):403-416

A probabilistic mathematical model of bivalve suspension-feeding in estuaries is based on bivalve abundance, filtering capacities, and water mixing parameters. We applied the model to five regions of the upper Chesapeake Bay, ranging from shallow tidal fresh habitats to deep mesohaline habitats, for the years 1985 to 1987. Model results indicated that existing suspension-feeding bivalves could consume more than 50% of annual primary production in shallow freshwater and oligohaline reaches of the upper Chesapeake Bay and Potomac River. In deep mesohaline portions of the Chesapeake Bay and Potomac River, suspension-feeding bivalves could consume only 10% of primary production. Independent estimates of benthic carbon demand based on benthic production supported the model predictions. Hydrodynamics of large estuaries restrict the potential of benthic suspension-feeders to crop phytoplankton production because the width and depth of these estuaries limit transport of pelagic waters to the littoral flanks of the estuaries where benthic suspension-feeders can be abundant. Benthic suspension-feeders are dominant consumers in shallow segments of the Chesapeake Bay system, but are suppressed in deeper segments. The suppression is below that set by hydrodynamic limits, and may be due to periodic hypoxia or other factors. Our results suggest that the proposed use of suspension-feeding bivalves to improve water quality of large estuaries will be limited by the depth and width of the estuary, unless the bivalves are suspended in the water column by artificial means.  相似文献   

Regional shear stress of broken forest from radiosonde wind profiles in the unstable surface layer     

Marc B. Parlange  Wilfried Brutsaert 《Boundary-Layer Meteorology》1993,64(4):355-368

Mean wind speed profiles were measured by tracking radiosondes in the unstable atmospheric boundary layer (ABL) over the forested Landes region in southwestern France. New Monin-Obukhov stability correction functions, recently proposed following an, analysis by Kader and Yaglom, as well as the Businger-Dyer stability formulation were tested, with wind speeds in the surface sublayer to calculate the regional shear stress. These profile-derived shear stresses were compared with eddy correlation measurements gathered above a mature forest stand, at a location roughly, 4.5 km from the radiosonde launch site. The shear stress values obtained by means of the newly proposed stability function were in slightly better agreement with the eddy correlation values than those obtained by means of a Businger-Dyer type stability function. The general robustness of the profile method can be attributed in part to prior knowledge of the regional surface roughness (z ₀=1.2 m) and the momentum displacement height (d ₀=6.0 m), which were determined from neutral wind profile analysis. The 100 m drag coefficient for the unstable conditions above this broken forest surface was found to beu _* ² /V ₁₀₀ ² =0.0173.  相似文献   

A comparison of two methods for the assimilation of altimeter data into a shallow-water model     

K. Haines  P. Malanotte-Rizzoli  R.E. Young  W.R. Holland 《Dynamics of Atmospheres and Oceans》1993,17(2-3)

Two simple methods for assimilating ocean surface pressure data into a three-layer adiabatic primitive equation model are tested and compared using a twin-experiment approach. One of the methods is based on a recently presented direct insertion scheme using a quasi-geostrophic model. The method explicitly avoids making changes to the potential vorticity fields in the lower layers and the vertical current structure after assimilation is determined by this criterion. The modification required for a primitive equation framework are discussed and a comparison is made with the more familiar ‘nudging’ method of assimilation. We use root mean square errors to quantify the response of the model to the assimilation of a single complete surface pressure field and also to repeated or intermittent data available every 20 days for a period of 1 year. The two methods are almost equally effective in the short term, although the direct insertion scheme appears to be more effective in the longer term. It is suggested that this is because insertion maintains a geostrophic balance at all levels and thus avoids the generation of internal gravity waves which are needed when nudging is used to restore geostrophic currents in the deeper layers.  相似文献   

Reaction transport modelling of a freshening aquifer (Tertiary Ledo-Paniselian Aquifer,Flanders-Belgium)     

Kristine Walraevens  Javier Cardenal-Escarcena  Marc Van Camp 《Applied Geochemistry》2007

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A 17,900-year multi-proxy lacustrine record of Lago Puyehue (Chilean Lake District): introduction     

Marc De Batist  Nathalie Fagel  Marie-France Loutre  Emmanuel Chapron 《Journal of Paleolimnology》2008,39(2):151-161

This paper introduces the background and main results of a research project aimed at unravelling the paleolimnological and paleoclimatological history of Lago Puyehue (40° S, Lake District, Chile) since the Last Glacial Maximum (LGM), based on the study of several sediment cores from the lake and on extensive fieldwork in the lake catchment. The longest record was obtained in an 11-m-long piston core. An age-depth model was established by AMS ¹⁴C dating, ²¹⁰Pb and ²³⁷Cs measurements, identification of event-deposits, and varve-counting for the past 600 years. The core extends back to 17,915 cal. yr. BP, and the seismic data indicate that an open-lake sedimentary environment already existed several thousands of years before that. The core was submitted to a multi-proxy analysis, including sedimentology, mineralogy, grain-size, major geochemistry and organic geochemistry (C/N ratio, δ¹³C), loss-on-ignition, magnetic susceptibility, diatom analysis and palynology. Along-core variations in sediment composition reveal that the area of Lago Puyehue was characterized since the LGM by a series of rapid climate fluctuations superimposed on a long-term warming trend. Identified climate fluctuations confirm a.o. the existence of a Late-Glacial cold reversal predating the northern-hemisphere Younger Dryas cold period by 500–1,000 years, as well as the existence of an early southern-hemisphere Holocene climatic optimum. Varve-thickness analyses over the past 600 years reveal periodicities similar to those associated with the El Niño Southern Oscillation and the Pacific Decadal Oscillation, as well as intervals with increased precipitation, related to an intensification of the El Niño impact during the southern-hemisphere equivalent of the Little Ice Age.  相似文献