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DAVID SWANLUND RAMONA MARAJ NADINE SCHUURMAN ROXANNE HOPE KATE DONKERS MATT AQUIN GWEN RICKERBY 《Geografiska Annaler: Series A, Physical Geography》2016,98(4):361-368
This study analyses GPS performance in Yukon's Arctic coast to inform future research that uses this technology in the region. To test this, Telonics GPS collars were placed on stakes during the summers of 2009 and 2010 throughout the region for varying lengths of time. The fix records produced by these collars were then collected and cleaned, leaving 30 samples. Using these records combined with a digital elevation model, eight variables were extracted and analysed in an attempt to find relationships, such that a fix rate could be predicted throughout the landscape. The results indicated that very few strong relationships existed. Densiometer values proved to be the only relationship between an environmental variable and fix rate. Available sky and aspect data produced results that were contrary to those expected. Overall, Telonics Generation 3 collars had extremely high fix rates, high accuracy, and low positional dilution of precision. Moreover, there was little variation in these results. This means that future GPS studies in the region would likely require minimal correction for fix rate bias. However, if corrections were to be made, more data would have to be gathered to ensure the results were statistically sound. The analysis suffered from the limitations of small sample size and low sample variance, among several others. Therefore, future studies should increase the number and diversity of sites tested. 相似文献
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Sediment deposition from flocculated suspensions 总被引：3，自引：0，他引：3
KATE KRANCK 《Sedimentology》1975,22(1):111-123
Suspended sediment in coastal environments with high inorganic content have characteristic broad size distributions and are composed of both single grains and flocculated aggregates. These flocculated suspensions have stable size distributions the modal size of which is dependent on the modal size of the deflocculated single grain distributions. Comparison between theoretical settling speeds of quartz grains and the settling speed of particles in natural suspensions indicates that most grains smaller than the deflocculated single grain mode settle as part of flocs, whereas the particles larger than the mode settle as single grains. As a result the size distribution curves of sediment populations which settle out during consecutive intervals are composed of a modal peak of larger grains and a low flat portion of smaller grains and resemble the asymmetrical non-normal curves common for muddy sediments. 相似文献
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Inge Loes TEN KATE James R. C. GARRY Zan PEETERS Richard QUINN Bernard FOING Pascale EHRENFREUND 《Meteoritics & planetary science》2005,40(8):1185-1193
Abstract— In the framework of international planetary exploration programs, several space missions are planned to search for organics and bio‐signatures on Mars. Previous attempts have not detected any organic compounds in the Martian regolith. It is therefore critical to investigate the processes that may affect organic molecules on and below the planet's surface. Laboratory simulations can provide useful data about the reaction pathways of organic material at Mars' surface. We have studied the stability of amino acid thin films against ultraviolet (UV) irradiation and use those data to predict the survival time of these compounds on and in the Martian regolith. We show that thin films of glycine and D‐alanine are expected to have half‐lives of 22 ± 5 hr and of 3 ± 1 hr, respectively, when irradiated with Mars‐like UV flux levels. Modelling shows that the half‐lives of the amino acids are extended to the order of 107 years when embedded in regolith. These data suggest that subsurface sampling must be a key component of future missions to Mars dedicated to organic detection. 相似文献
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Calciturbidite composition related to exposure and flooding of a carbonate platform (Triassic, Eastern Alps) 总被引：1，自引：0，他引：1
The compositional variation of calciturbidites (Pedata/Pötschen Formation), deposited adjacent to the Dachstein Formation carbonate platform in the Triassic Hallstatt Basin, was analysed using detailed field measurements and point-counting of thin sections. The 35 m long section is located in the Northern Calcareous Alps of Austria. Six point-count groups were distinguished separating basinal from platform-derived input. Summary statistics, cluster and correspondence analysis of the point-count data reveals a close relationship between the biota present on the Dachstein carbonate platform and the calciturbidite composition. The variations in turbidite composition are attributed to fluctuations in sea level and resulting flooding and exposure of the platform, which alternately created and destroyed shallow-water habitats on the platform top. 相似文献
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Particulate matter grain-size characteristics and flocculation in a partially mixed estuary 总被引：1，自引：0，他引：1
KATE KRANCK 《Sedimentology》1981,28(1):107-114
The concentration and grain size of the natural and deflocculated inorganic suspended particulate matter were measured along the length of the Miramichi Estuary and interpreted with respect to flocculation and transport properties. Changes in particulate matter concentration are associated with regular changes in grain-size characteristics. In the turbidity maximum region of the estuary the suspended matter occurs mostly as large flocculated particles whereas, in the waters with lower particle concentrations, a larger proportion of the material occurs as fine material. At higher concentrations natural floc modes and inorganic grain modes vary simultaneously but at low concentrations the two modes vary inversely. This modal relationship and the variation in organic matter within the estuary is proposed to result from variation in inorganic—organic composition of flocs. Increase in settling rates due to flocculation is believed to increase the trapping effect of the estuarine circulation that produces the turbidity maximum. 相似文献
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Grain-size characteristics of fine-grained unflocculated sediments I:'one-round' distributions 总被引：1，自引：0，他引：1
A simple physical model of gravitational settling from an unsorted, unflocculated source suspension is presented and an equation derived to describe the grain-size spectra of the resulting bottom sediment. Results of grain-size analyses of sediments from a variety of environments and geographical locations are shown to conform with the postulated model. The characteristic size spectrum, termed ‘one-round’ sediment, identifies a deposit which has settled from suspension with no subsequent reworking resulting in modification of the grain-size distribution. The distribution of settling rates of grains in the suspension may be inferred from an analytical form fit to the bottom sediment grain-size spectrum, along with knowledge of certain physical characteristics of the fluid (e.g. mean velocity profile). 相似文献
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Grain-size characteristics of fine-grained unflocculated sediments II:'multi-round' distributions 总被引：2，自引：0，他引：2
The grain-size spectrum of sediment deposited by settling of a suspension with a ‘one-round’ grain size distribution is described by a power law in which the integer exponent characterizing the fine-grained limb is increased by one over that of the suspension. If this better-sorted sediment, in turn, is resuspended and settles, further sorting and steepening of the limb occurs. Each resuspension event or‘round’changes the distribution by a predictable amount. Equations describing this sorting process, based on the derivation of the one-round equation, are fitted to grain-size analyses of well-sorted sediment from a variety of locations to verify the model. A suite of sandy bottom sediment samples from the Bay of Fundy shows that the steepness of the fine-grained limbs of the sand fraction indeed increases in integral steps. 相似文献
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The paper is based on a study of minerl assemblages in metamorphiciron formations in northere Quebec. Thirty-four mineral analyseshave been performed, using photometric methods of silicate analysis. Three facies of iron formation are represented, namely, quartz-speculariteiron formation, quartz-magnetite iron formation, and quartz-silicateiron formation. The silicate iron formation is made up mainlyof quartz, ferrohypersthene, ferroaugite, cummingtonite, andcalcite. Arfvedsonite and aegirine-hedenbergite occur in magnetite-richrocks. The analysed coexisting minerals are from the silicate ironformation and from overlying mafic rocks of igneous origin.The analysed assemblages include ferrohypersthene-ferro-augite-cummingtonite,ferrohypersthen-ferroaugite, cummingtonite-ferroaugite, diopside-hornblende,anthophyllite-hornblende, hypersthene-diopside-hornblende-garnet,and olivine-hypersthene-chlorite. The analyses show that (1) the minerals are nearly in equilibriumas shown by parallel tie lines, (2) cummingtonite generallyhas a higher MgO/FeO ratio than coexisting ferrohypersthene,(3) the phase higher in calcium has the higher MgO/FeO ratio,(4) the solubility gap between ferrohypersthene and ferroaugiteis 43 mole percent. The stability relationships of pyroxenes and amphiboles arediscussed in view of the new data. It is shown that FeO-CaO-SiO2systems often behave differently from MgO-CaO-SiO2 systems.Hedenbergite is probably not stable in the presence of excessCO2 in the area. The low variance ferrohypersthene-ferroaugite-cummingtonite-calcite-quartzassemblage indicates that the rocks were closed to H2O and CO2.The behaviour of the volatile components is discussed in viewof this fact. The source of the silicate minerals is assumed to be hydrousiron silicates and carbonates. A model of the sequence of chemicalreactions taking place in carbonate-silicate iron formationsduring metamorphism is suggested.
1Present address: Bolidens Gruvaktiebolag, Boliden, Sweden. 相似文献
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