Variational assimilation of time sequences of surface observations with serially correlated errors   总被引：1，自引：0，他引：1  

HEIKKI JÄRVINEN  ERIK ANDERSSON  FRANÇOIS BOUTTIER 《地球，A辑:动力气象学与海洋学》1999,51(4):469-488

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Sequence stratigraphy of the Upper Oligocene–Lower Miocene of eastern Jylland, Denmark: role of structural relief and variable sediment supply in controlling sequence development     

ERIK S. RASMUSSEN  KAREN DYBKJÆR 《Sedimentology》2005,52(1):25-63

The Upper Oligocene–Lower Miocene succession in eastern Jylland can be subdivided into three sequences (A–C from older to younger) deposited on and around the Ringkøbing-Fyn High. The development of the sequences reflects a complex interaction between eustatic sea-level changes, physiography and variable sediment supply. Superimposed on this, frequent storms promoted longshore sediment transport and the development of spit systems adjacent to structural highs. As a consequence, sequence boundaries and flooding surfaces are not always expressed as portrayed in conventional sequence models; sequence boundaries or flooding surfaces may only be marked by subtle changes in depositional environment that can only be revealed by careful integration of sedimentological observations with palynological data. The influence of the topography resulted in the development of brackish water basins that were sufficiently large to permit the deposition of hummocky cross-stratified sands with muds. These deposits are overlain by clean hummocky and swaley cross-stratified sands that were deposited in a fully marine, high-energy environment. This evolution from mud-rich, storm-influenced sediments to sand-dominated shoreface sediments resulted from a rise in sea level and was not the result of shoreface progradation and downstepping during a sea level fall. In addition to the topographic control on sequence development, sediment supply to the study area changed significantly during the deposition of the three sequences. Initially the basin was sediment-starved, favouring the formation of glaucony-rich sediments. The sediment input gradually increased and the influence of structural highs and lows became less significant with time. Consequently, both sequence boundaries and flooding surfaces are characterized by more conventional features in the younger part of the succession, where a basinward displacement of the shoreline resulted in thick lowstand delta deposits.  相似文献   

Timing and pattern of the last deglaciation in the Kattegat region, southwest Scandinavia     

ERIK LAGERLUND  MICHAEL HOUMARK-NIELSEN 《Boreas: An International Journal of Quaternary Research》1993,22(4):337-347

This paper presents evidence on the timing and pattern of the Late Weichselian deglaciation in SW Scandinavia, particularly in the Öresund–Kattegat region before the Allerød interstadial. New radiocarbon ages and evaluated older dates demonstrate that active glacier ice had left eastern Denmark, southern Halland and western Skåne before 14,000 BP. The deglaciation in the Öresund region took place mainly under glacioestuarine conditions in a narrow fjord or inlet with some marine influence, as indicated by radiocarbon-dated finds of Polar Cod ( Boreogadus saida ) and the vertebra of a Ringed Seal ( Phoca hispida ). The Swedish west coast experienced glaciomarine and deltaic ice proximal conditions, where Vendsyssel was at the same time under full marine conditions with little evidence of ice rafting. A paleogeographic interpretation illustrates land, sea and ice configurations around 14,000 BP. We suggest that a subsequent lateglacial transgression reached the entire region almost simultaneously and peaked around 13,300 BP. This led to deposition of an ice-rafted diamicton ( the Öresund diamicton ) in Skåne and Sjælland, and of glaciolacustrine mud in Halland. We propose that the complex transgression and regression events recorded in the region were governed by interaction of the eustatic sea level rise, isostatic reponse to glacier unloading and possibly also by damming by an ice stream in the Skagerrak and northern Kattegat.  相似文献   

The effects of oil and oil dispersants on the amphipod Gammarus oceanicus from Arctic waters     

TORE AUNAAS  ERS OLSEN  KARL ERIK ZACHARIASSEN 《Polar research》1991,10(2):619-630

Amphipods of the species Gammarus oceanicus were exposed to water soluble fractions and water emulsions crude oil, the dispersants Finasol OSR-5 and Finasol OSR-12, and combinations of the oil and dispersants. Adding Finasol OSR-12 to the crude oil caused a reduction in the mortality of the amphipods compared with amphipods exposed to the water soluble fraction and the water emulsion of crude oil alone, probably due to a reduced mole fraction of toxic oil components in the mixture of oil and dispersant. Exposure to sublethal concentrations of water soluble fractions increased the respiratory rates of the amphipods in the majority of the exposed groups. The water soluble fractions slightly increased the concentrations of sodium in the haemolymph and in the whole organism. Some exposures gave a significant increase in the relative water content of the amphipods. The water soluble fractions probably increase the membrane permeability to water and ions, leading to an increased influx of water and sodium from the medium. The increased respiratory rates are likely to be due to a compensatory extrusion of sodium. Exposure to sublethal concentrations of water emulsions reduced the respiratory rates of the amphipods, probably due to oil droplets adhering to the gill membranes and thus causing a reduced rate of oxygen diffusion into the organisms. The majority of the exposures to water emulsions increased concentrations of sodium in the haemolymph as well as in whole organisms. Thus, sodium probably accumulates in the intracellular compartments because the sodium pumps are restricted by the reduced energy available. This is likely to lead to an osmotic swelling of cells. Reduced total free amino acid concentrations in these amphipods is ascribed to volume regulation of the swollen cells, and a reduced co-transport of sodium and free amino acids from the haemolymph to the intracellular compartments.  相似文献   

Pleistocene Underplating and Metasomatism of the Lower Continental Crust: a Xenolith Study   总被引：9，自引：5，他引：4  

SACHS  PETER M.; HANSTEEN  THOR H. 《Journal of Petrology》2000,41(3):331-356

Xenoliths from Engeln–Kempenich in the East Eifel volcanicfield (Germany) comprise gabbroic to ultramafic cumulates, andmeta-igneous and meta-sedimentary granulite- to amphibolite-facieslithologies. They provide evidence for Pleistocene heating andmetasomatism of the lower continental crust by mafic magmas.The metamorphic xenoliths were divided into three types: (1)primitive type P, which are little affected by metasomatic replacementstructures; (2) enriched type E1 defined by metasomatic replacementof primary pyroxene and garnet by pargasitic amphibole and biotite;(3) enriched type E2 defined by breakdown of hydrous phases.Type E rocks are geochemically related to type P and cumulatexenoliths by compositional trends. During modal metasomatism,type E rocks were oxidized. Type E1 rocks were typically enrichedin Rb, Th, U, Nb, K, light rare earth elements (LREE) and Zr,and E2 enriched in Rb, Th, U, Nb, K, REE, Zr, Ti and Y, relativeto type P rocks. Formation of the hydrous, chlorine-bearingphases amphibole and scapolite containing glass and fluid inclusionsin the E1 rocks provides evidence for a water and Cl-bearingfluid phase coexisting with silicate melt. Accordingly, we calculated10 mol % H₂O back into the CO₂-dominated fluid inclusions, inagreement with experimental data on the composition of a fluidphase coexisting with mafic alkaline melts at elevated pressure.Primary CO₂-dominated fluid inclusions coexisting with glassinclusions in metamorphic corona phases and neoblasts, and incumulate xenoliths, have overlapping densities. Fluid inclusionbarometry using the corrected densities indicates that bothcumulates and metamorphic xenoliths originated from the samedepth at 22–25 km (650 ± 50 MPa). This is interpretedas being a main magma reservoir level within the upper partof the lower crust close to the Conrad discontinuity, wherethe xenoliths represent wall-rocks. The Conrad discontinuityseparates an upper-crustal layer, consisting of preferentiallyductile granodioritic and tonalitic gneisses, and more brittlelower-crustal mafic granulites. The brittle–ductile transitionappears to be a preferred level of magma stagnation. KEY WORDS: continental lower crust; fluids; magma chamber; metasomatism; xenoliths  相似文献   

Trichinella sp. in polar bears from Svalbard, in relation to hide length and age     

THOR LARSEN  BJØRN KJOS-HANSSEN 《Polar research》1983,1(1):89-96

DiaPhragma and masseter muscles from 376 polar bears ( Ursus maritimus ), 252 ringed seals ( Phoca hispida ), 84 bearded seals ( Erignathus barbatus ), and 77 arctic foxes ( Alopex lagopus ) from Svalbard were examined for Trichinella . Infection rates in polar bears varied between 23 and 58%, and between 3 and 67% in arctic fox- None of tne seals were infected. Trichinella in polar bears is probably transferred through cannibalism and scavenging upon polar bear carcasses. Infection rate in arctic fox was high when they preyed upon polar bear carcasses before polar bear hunting was prohibited in 1973. A low infection rate seems more natural when such prey is not available. No difference could be found in infection rate between male and female polar bears. There is only a slight increase in infection rate with age, as calculated from hide lengths, and many adult animals remain uninfected. Geographical isolation of polar bear populations may explain differences in Trichinella infection rates between bears from arctic America and arctic Europe. Possible explanations are that discrete polar bear populations have different food habits, or that they are exposed to different Trichinella strains.  相似文献   

Impact origin of the Vesta family     

ERIK ASPHAUG 《Meteoritics & planetary science》1997,32(6):965-980

Abstract— The compelling petrographic link (Consolmagno and Drake, 1977; Gaffey, 1983) between basaltic achondrite meteorites and the ～530 km diameter asteroid 4 Vesta has been tempered by a perceived difficulty in launching rocks from this asteroid's surface at speeds sufficient to bring them to Earth (Wasson and Wetherill, 1979) without obliterating Vesta's signature crust. I address this impasse in response to recent imaging (Zellner et al, 1996; Dumas and Hainaut, 1996) of a ～450 km impact basin across Vesta's southern hemisphere (Thomas et al., 1997) and model the basin-forming collision using a detailed two-dimensional hydrocode with brittle fracture including self-gravitational compression (cf., Asphaug and Melosh, 1993). A ～42 km diameter asteroid striking Vesta's basaltic crust (atop a denser mantle and iron core) at 5.4 km/s launches multikilometer fragments up to ～600 m/s without inverting distal stratigraphy, according to the code. This modeling, together with collisional, dynamical, rheological and exposure-age timescales (Marzari et al., 1996; Welten et al., 1996), and observations of V-type asteroids (Binzel and Xu, 1993) suggests a recent (<～1 Ga) impact origin for the Vesta family and a possible Vesta origin for Earth-approaching V-type asteroids (Cruik-shank et al., 1991).  相似文献   

Thinning of the ice sheet by melting: a preliminary model for calculating deglaciation rates over central Sweden about 10,000 B.P.     

ERIK BERGQVIST 《Boreas: An International Journal of Quaternary Research》1979,8(2):119-124

Thinning of the ice sheet took place by two different processes - by the melting of ice over the whole or part of the surface and by the outflow of ice from the central parts of the ice body. A simulation model should therefore include both types of processes. A first draft of a model for the melting is presented, together with some notes about other parts of a complete, complex model for the thinning of the ice.  相似文献   

JORDSAND—EROSION UND AKKUMULATION EINER HALLIG     

MARGOT JESPERSEN M.Sc.  ERIK RASMUSSEN M.Sc. 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):13-23

Jespersen, Margot und Rasmussen, Erik: Jordsand—Erosion und Akkumulation einer Hallig. Geografisk Tidsskrift 75: 13–23. København, juni 1, 1976.

Since 1972 the authors have carried out investigations of erosion and accumulation on the island of Jordsand in the Danish Wadden Sea. The investigations supported by the Danish State Research Council for Natural Sciences are not yet finished, and this paper is a midway report including preliminary results and working hypotheses.  相似文献   

GEOGRAPHIES OF THE HOLOCAUST     

WAITMAN BEORN  TIM COLE  SIMONE GIGLIOTTI  ALBERTO GIORDANO  ANNA HOLIAN  PAUL B. JASKOT  ANNE KELLY KNOWLES  MARC MASUROVSKY  ERIK B. STEINER 《Geographical review》2009,99(4):563-574

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