The GEOIDE Network –Integrating Research and Development for the Benefit of the Canadian Geomatics Industry     

Geoffrey Edwards  & Tom DeGroeve 《Transactions in GIS》2000,4(2):91-97

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A vertically resolved model for phytoplankton aggregation     

Iris Kriest  Geoffrey T. Evans 《Journal of Earth System Science》2000,109(4):453-469

This work presents models of the vertical distribution and flux of phytoplankton aggregates, including changes with time in the distribution of aggregate sizes and sinking speeds. The distribution of sizes is described by two parameters, the mass and number of aggregates, which greatly reduces the computational cost of the models. Simple experiments demonstrate the effects of aggregation on the timing and depth distribution of primary production and export. A more detailed ecological model is applied to sites in the Arabian Sea; it demonstrates that aggregation can be important for deep sedimentation even when its effect on surface concentrations is small, and it presents the difference in timing between settlement of aggregates and fecal pellets.  相似文献   

Ineffective Natural Attenuation of Degradable Organic Compounds in a Phenol-Contaminated Aquifer   总被引：4，自引：0，他引：4  

David N. Lerner  Steven F. Thornton  Michael J. Spence  Steven A. Banwart  Simon H. Bottrell  Jenny J. Higgo  Helen E. H. Mallinson  Roger W. Pickup  Geoffrey M. Williams 《Ground water》2000,38(6):922-928

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Late-glacial and early-Holocene Coleoptera assemblages as indicators of local environment and climate at Kråkenes Lake, western Norway     

Geoffrey Lemdahl 《Journal of Paleolimnology》2000,23(1):57-66

Thirty-six Coleoptera (beetle) taxa and other insects were identified from the late-glacial and early-Holocene sediments at Kråkenes Lake. Compared with other Scandinavian late-glacial sites, this is a rather sparse record. The water beetles found in the Allerod are characteristic of a poorly vegetated clear-water lake. The terrestrial fauna is indicative of dwarf-shrub and moss vegetation. A marked decline in the number of species at the start of the Younger Dryas was rather rapid, probably over less than 80 calendar yrs. No obligate tundra species replaced the Allerod fauna. Most of the Younger Dryas is virtually devoid of beetles. The increase in numbers and diversity of both aquatic and terrestrial species at the Younger Dryas/Holocene transition is very rapid. After an initial pioneer stage, beetles associated with dwarf-shrub heath and willow scrub appeared, but no obligate tree or forest taxa were recorded.Mutual Climatic Range (MCR) temperature reconstructions suggest that the Allerod was colder and more continental than present. The near absence of beetles in the Younger Dryas probably reflects very cold conditions. A rapid temperature rise at the start of the Holocene resulted in a warmer and more continental climate than present.  相似文献   

New interglacial deposits from Copenhagen,Denmark: marine Isotope Stage 7     

Ole Bennike  Lars Hedens  Kirsty High  Joakim S. Korshj  Geoffrey Lemdahl  Kirsty Penkman  Richard C. Preece  Knud Rosenlund  Finn A. Viehberg 《Boreas: An International Journal of Quaternary Research》2019,48(1):107-118

During a pre‐site survey and construction of a new metro route and station in Copenhagen, fossiliferous organic‐rich sediments were encountered. This paper reports on multidisciplinary investigations of these organic sediments, which occurred beneath a sediment succession with a lower till, glacifluvial sand and gravel, an upper till and glacifluvial sand. The organic sediments were underlain by glacifluvial sand and gravel. The organic‐rich sediments, which were up to 0.5 m thick, accumulated in a low‐energy environment, possibly an oxbow lake. They were rich in plant fossils, which included warmth‐demanding trees and other species, such as Najas minor, indicating slightly higher summer temperatures than at present. Freshwater shells were also frequent. Bithynia opercula allowed the sediments to be put into an aminostratigraphical framework. The amino acid racemization (AAR) ratios indicate that the organic sediments formed during Marine Isotope Stage 7 (MIS 7), which is consistent with optically stimulated luminescence dating that gave ages of 206 and 248 ka from the underlying minerogenic deposit. The assemblages from Trianglen are similar to interglacial deposits from the former Free Port (1.4 km away) in Copenhagen, except that Corbicula and Pisidium clessini were not found at Trianglen. The presence of these bivalves at the Free Port and the ostracod Scottia tumida at Trianglen indicates a pre‐Eemian age. AAR data from archived Bithynia opercula from the Free Port were almost identical to those from Trianglen, indicating that the two sites are contemporary. We suggest the Trianglen interglacial be used as a local name for the MIS 7 interglacial deposits in Copenhagen. MIS 7 deposits have rarely been documented from the region, but MIS 7 deposits may have been mistaken for other ages. The use of AAR ratios in Bithynia opercula has a great potential for correlation of interglacial non‐marine deposits in mainland northern Europe.  相似文献   

The importance of goats to a natural environment: a case study from Epirus (Greece) and Southern Albania     

Sarah Green  Geoffrey King 《地学学报》1996,8(6):655-658

In the Epirus region of North-west Greece, spring flows in villages have reduced dramatically over the last few decades, in some cases with serious economic consequences. We argue here that this has resulted from the major reduction of grazing by mountain goats over the same period together with other associated land-use changes. Normally such a contention would be impossible to demonstrate because many different causes could be invoked. However, prior to 1946 culturally homogenous Greek-speaking communities with identical pastoral practices were separated by the closure of the Greek-Albanian border. Changes of spring flow have not occurred on the Albanian side of the border where heavy grazing has continued. In a region such as Greece where pastoralism has continued for thousands of years, the environment had reached an equilibrium with goat grazing. Apart from the reduction of spring flows, other undesirable ecological consequences are occurring.
It is also interesting to note that long-term water table changes such as those occurring in Epirus have been attributed to tectonic effects and thought to potentially predict earthquakes. The effect however, may be the result of goats and other livestock 'leaving' and not the result of earthquakes 'coming'.  相似文献   

Corrigendum to “A comparison of lignin oxidation, enzymatic activity and fungal growth during white-rot decay of wheat straw” [Org. Geochem. 39 (2008) 945–951]     

Steven A. Robertson  Sharon L. Mason  Ethan Hack  Geoffrey D. Abbott   《Organic Geochemistry》2008,39(12):945

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Mobility of rare-earth elements and copper during shear-zone-related retrograde metamorphism     

de Jong  Geoffrey  Rotherham  Jackie  Phillips  G. Neil  Williams  Patrick J. 《Geologie en Mijnbouw》1997,76(4):311-319

In Mid Proterozoic crystalline rocks of the Mount Isa Inlier, around Cloncurry, Australia, 2000 km² of alteration and brecciation are the product of high-temperature (> 450 °C) concentrated saline solution activity. During retrogression, this fluid was locally responsible for mobility of V, Y, Nb and light rare-earth elements (15 × enrichment). Copper and S were leached during alteration and this may have been a significant source of components in nearby Cu-Au deposits. Similar rare-earth-element behaviour has been observed in the hematite breccias which host Cu-sulfides at the giant Olympic Dam Cu-Au deposit.  相似文献   

A new approach to simulating disorder in crystals     

I. L. Jones  Volker Heine  Maurice Leslie  Geoffrey D. Price 《Physics and Chemistry of Minerals》1990,17(3):238-245

The technique of calculating lattice dissociation energies using static, minimum lattice energy, ionic models has been extended to allow for multiple occupancy of the ionic sites. A particular lattice site can have a fraction x of an ionic species A and a fraction y of an ionic species B, where the position of each can be relaxed separately along with the unit cell dimensions until an equilibrium is reached. Various degrees of long and short range order can be modelled. This technique has been applied to the mineral sillimanite, Al₂SiO₅, to calculate the effect on the lattice energy of (Al, Si) ordering over the tetrahedral sites. It is found using this method that (Al, Si) ordering with space group Pbmn stabilizes the material by 29.25 kcal/mol (Al^iv-O-Al^iv), with respect to the completely disordered material.  相似文献   

Book reviews     

Geoffrey Abers  Robert D. Cicerone  Douglas J. Galpin  William Power  Tracy Rushmer  J. Leliwa-Kopystynski  Krzysztof Haman  Daniel Wójcik  Michal Herbich  Bogumil Jakubiak  Szymon P. Malinowski 《Pure and Applied Geophysics》1996,147(3):585-610

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