Testing accretion mechanisms of the H chondrite parent body utilizing nucleosynthetic anomalies     

Sren Grube Pedersen  Martin Schiller  James N. Connelly  Martin Bizzarro 《Meteoritics & planetary science》2019,54(6):1215-1227

Planetary bodies a few hundred kilometers in radii are the precursors to larger planets but it is unclear whether these bodies themselves formed very rapidly or accreted slowly over several millions of years. Ordinary H chondrite meteorites provide an opportunity to investigate the accretion time scale of a small planetary body given that variable degrees of thermal metamorphism present in H chondrites provide a proxy for their stratigraphic depth and, therefore, relative accretion times. We exploit this feature to search for nucleosynthetic isotope variability of ⁵⁴Cr, which is a sensitive tracer of spatial and temporal variations in the protoplanetary disk's solids, between 17 H chondrites covering all petrologic types to obtain clues about the parent body accretionary rate. We find no systematic variability in the mass‐biased corrected abundances of ⁵³Cr or ⁵⁴Cr outside of the analytical uncertainties, suggesting very rapid accretion of the H chondrite parent body consistent with turbulent accretion. By utilizing the μ⁵⁴Cr–planetary mass relationship observed between inner solar system planetary bodies, we calculate that the H chondrite accretion occurred at 1.1 ± 0.4 or 1.8 ± 0.2 Myr after the formation of calcium‐aluminum‐rich inclusions (CAIs), assuming either the initial ²⁶Al/²⁷Al abundance of inner solar system solids determined from angrite meteorites or CAIs from CV chondrites, respectively. Notably, these ages are in agreement with age estimates based on the parent bodies’ thermal evolution when correcting these calculations to the same initial ²⁶Al/²⁷Al abundance, reinforcing the idea of a secular evolution in the isotopic composition of inner disk solids.  相似文献   

The northern boundary of the Jan Mayen microcontinent, North Atlantic determined from ocean bottom seismic, multichannel seismic, and gravity data   总被引：1，自引：0，他引：1  

Aleksandre Kandilarov  Rolf Mjelde  Rolf-Birger Pedersen  Bjarte Hellevang  Cord Papenberg  Carl-Joerg Petersen  Lars Planert  Ernst Flueh 《Marine Geophysical Researches》2012,33(1):55-76

The Jan Mayen microcontinent was as a result of two major North Atlantic evolutionary cornerstones—the separation of Greenland from Norway (~54 Ma), accompanied by voluminous volcanic activity, and the jump of spreading from the Aegir to the Kolbeinsey ridge (~33 Ma), which resulted in the separation of the microcontinent itself from Eastern Greenland (~24 Ma). The resulting eastern and western sides of the Jan Mayen microcontinent are respectively volcanic and non-volcanic rifted margins. Until now the northern boundary of the microcontinent was not precisely known. In order to locate this boundary, two combined refraction and reflection seismic profiles were acquired in 2006: one trending S–N and consisting of two separate segments south and north of the island of Jan Mayen respectively, and the second one trending SW–NE east of the island. Crustal P-wave velocity models were derived and constrained using gravity data collected during the same expedition. North of the West Jan Mayen Fracture Zone (WJMFZ) the models show oceanic crust that thickens from west to east. This thickening is explained by an increase in volcanic activity expressed as a bathymetric high and most likely related to the proximity of the Mohn ridge. East of the island and south of the WJMFZ, oceanic Layers 2 and 3 have normal seismic velocities but above normal average crustal thickness (~11 km). The similarity of the crustal thickness and seismic velocities to those observed on the conjugate M?re margin confirm the volcanic origin of the eastern side of the microcontinent. Thick continental crust is observed in the southern parts of both profiles. The northern boundary of the microcontinent is a continuation of the northern lineament of the East Jan Mayen Fracture Zone. It is thus located farther north than previously assumed. The crust in the middle parts of both models, around Jan Mayen island, is more enigmatic as the data suggest two possible interpretations—Icelandic type of oceanic crust or thinned and heavily intruded continental crust. We prefer the first interpretation but the latter cannot be completely ruled out. We infer that the volcanism on Jan Mayen is related to the Icelandic plume.  相似文献   

A scaled experiment for the verification of the SeaBed Logging method     

L.O. Lseth  H.M. Pedersen  T. Schaug-Pettersen  S. Ellingsrud  T. Eidesmo 《Journal of Applied Geophysics》2008,64(3-4):47-55

SeaBed Logging (SBL) is an application of the marine controlled source electromagnetic (CSEM) method that is used to directly detect and characterize possible hydrocarbon-bearing prospects. Although the CSEM method has been used by academia for more than three decades, the application as a direct hydrocarbon indicator was first introduced about five years ago. The central idea of SBL is the guiding of electromagnetic energy in thin resistive layers within conductive sediments. Even if it has been well known for a long time that electromagnetic signals can propagate from a conductive region to another via resistive regions such as air or resistive parts of the lithosphere, the application to hydrocarbon exploration has not been developed until recently. This might be due to the uncertainty of getting any significant response from thin resistive layers such as hydrocarbon reservoirs since electromagnetic energy is highly attenuated in conductive sediments. Thus, during the early development phase of the SBL technique, a scaled laboratory experiment was performed to validate if a thin resistive layer (e.g. hydrocarbons) buried within conductive media (e.g. sediments) could be remotely detected by using electric dipoles as sources and receivers. Data from this experiment were compared to a forward modelling code for layered media, and the comparison showed good agreement between experimental and theoretical results. This suggested that thin resistive layers buried in conductive media are detectable due to the guiding of the electromagnetic field within the resistor. The successful results were vital for realizing the application of marine CSEM as a hydrocarbon exploration technique. We here present the results of the first scaled SBL experiment.  相似文献   

Mapping fisheries in the German exclusive economic zone with special reference to offshore Natura 2000 sites     

Søren Anker Pedersen  Heino O. Fock  Anne F. Sell 《Marine Policy》2009

Large intensity and diversity of human activities result in an increase in complexity in the utilization of space. This paper describes the fisheries and a method to map fishing efforts and catches of different fleets by combining vessel monitoring system (VMS) data and logbook data. The method makes it possible to explore the spatial and temporal variability of fishing and the potential impacts of proposed management measures on the fisheries. The method is proposed to be used in the development of management plans for marine protected areas such as Natura 2000 sites, designated to protect vulnerable habitats and species.  相似文献   

Industrial minerals and rocks, aggregates and natural stones in the Nordic countries     

Kurt Johansson Rune B. Larsen Markku J. Lehtinen Lars Persson Mika Raeisaenen Stig A. Schack Pedersen Paer Weihed Nils-Gunnar Wik 《《幕》》2008,31(1):133-139

The Nordic countries, including Greenland, have a long tradition in mining. The industrial minerals sector is expanding in most Nordic countries and extensive development has taken place during the last few years. The main commodities mined are carbonate rocks, quartz, feldspar, apatite, olivine and talc.
A number of diferent types of dimension stones are quarried in all countries. Rock aggregates are increasingly important, replacing sand and gravel aggregate as construction materials in some countries due to the need to protect ground water supplies.  相似文献   

Introduction to the Proceedings of the ECONORTH Symposium on Ecosystem Dynamics in the Norwegian and Barents Sea     

Torstein Pedersen  Kurt S. Tande  John G. Pope   《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(21-22):1893

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Sulfide intrusion in the tropical seagrasses Thalassia testudinum and Syringodium filiforme     

Marianne Holmer  Ole Pedersen  Dorte Krause-Jensen  Birgit Olesen  Malene Hedegrd Petersen  Stephanie Schopmeyer  Marguerite Koch  Bente Aa. Lomstein  Henning S. Jensen 《Estuarine, Coastal and Shelf Science》2009,85(2):319-326

Sulfur and oxygen dynamics in the seagrasses Thalassia testudinum and Syringodium filiforme and their sediments were studied in the US Virgin Islands (USVI) in order to explore sulfide intrusion into tropical seagrasses. Four study sites were selected based on the iron concentration in sediments and on proximity to anthropogenic nutrient sources. Meadow characteristics (shoot density, above- and below-ground biomass, nutrient content) were sampled along with sediment biogeochemistry. Sulfide intrusion was high in T. testudinum, as up to 96% of total sulfur in the plant was derived from sediment-derived sulfides. The sulfide intrusion was negatively correlated to the turnover of sulfides in the sediments regulated by both plant parameters and sediment sulfur pools. Sediment iron content played an indirect role by affecting sulfide turnover rates. Leaf production was negatively correlated with sulfide intrusion suggesting that active growth reduced sulfide intrusion. Sulfide intrusion was lower in S. filiforme (up to 44%) compared to T. testudinum consistent with a higher internal nighttime oxygen concentrations found for S. filiforme. When S. filiforme can take advantage of its ability to maintain high internal oxygen concentrations, as was the case on the USVI, it could increase its success in colonizing unvegetated disturbed sediments with potentially high sulfide concentrations.  相似文献   

Stability of an immersed tunnel in offshore conditions under deep water wave impact     

T. Kasper  J.S. Steenfelt  L.M. Pedersen  P.G. Jackson  R.W.M.G. Heijmans 《Coastal Engineering》2008

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Deep reflection seismics in the Precambrian of Sweden     

T. Dahl-Jensen  D. Dyrelius  C. Juhlin  H. Palm  L.B. Pedersen 《Geophysical Journal International》1987,89(1):371-378

Summary. A total of 161 km of deep seismic profiles have been shot in the region. One profile crosses the Protogine zone in SW Sweden. Over most of the profile short, weak reflectors are seen The only area with a concentration of reflectors is in the upper two seconds between the two tectonic zones. A nearly transparent area east of the Protogine zone is interperted as a deep granite intrustion. In the Siljan impact structure where four profiles were shot, the NE part of the structure is dominated by upper crustal high amplitude reflectors. Possible causes are discussed.  相似文献   

X-ray, Lyα and Hα emission from simulated disk galaxies     

Jesper Sommer-Larsen  Sune Toft  Jesper Rasmussen  Kristian Pedersen  Martin Götz  Laura Portinari 《Astrophysics and Space Science》2003,284(2):693-696

The X-ray properties of the haloes of disk galaxies formed in fully cosmological, hydro/gravity simulations are discussed. The results are found to be consistent with observational X-ray detections and upper limits. Disk galaxy haloes are predicted to be about an order of magnitude brighter at z ∼ 1 than at z=0. The Lyα and Hα surface brightness of an edge-on, Milky Way like model galaxy has been determined. The emission is found to be quite extended, with a scale height of about 600 pc, neglecting dust corrections. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献