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1.
Shallow seismic data and vibrocore information, sequence stratigraphic and faunal evidence have been used for documentation of Late Weichselian reactivation of faulting in the south central Kattegat, southern Scandinavia. The study area is situated on the Fennoscandian Border Zone, where tectonic activity has been recurrent since Early Palaeozoic time and still occurs, as shown by present earthquake activity. New data from the area south of the island of Anholt show that after deglaciation fast isostatic rebound resulted in reactivation of a NW-SE striking normal fault system. This tectonic episode is dated to a period starting shortly before 15.0 cal. ka BP and ending around 13.5 cal. ka BP, after regression had already reached a level of about 30 m b.s.l. The vertical displacement associated with the faulting was in the order of 20 m. More generally, the results support the previously reported late Weichselian sea-level highstand, which was followed by forced regression until the eustatic sea-level rise surpassed the rate of glacio-isostatic rebound in early Preboreal. Our findings further imply that drainage of the Baltic Ice Lake through the Øresund at c. 15 cal. ka BP (Bergsten & Nordberg 1992) may have been triggered by tectonic activity in this region.  相似文献   
2.
A study of the Middle Jurassic Rannoch Formation in the Gullfaks Field shows that there is no relationship between the content and distribution of kaolinite and location relative to the late Cimmerian unconformity. From petrographic data most of the kaolinite is interpreted to be detrital, and only traces of authigenic kaolinite are observed. Mass-balance calculations are used to provide guidelines as to the likelihood of kaolinite being formed and preserved in sandstones under the unconformity. The result of the calculations shows that the propagation rate of the dissolution front in the sandstones was probably on average slower than the erosion rates during the formation of the late Cimmerian unconformity. Hence, transformation of significant amounts of feldspar and mica to kaolinite probably did not take place within the sandstones which at present underlie the unconformity in the Gullfaks Field. Periods of exposure during formation of unconformities may thus be less effective causes of kaolinitization in sandstones than has been assumed.  相似文献   
3.
Two regional climate model experiments for northern and central Europe are studied focussing on greenhouse gas‐induced changes in heavy precipitation. The average yearly maximum one‐day precipitation P max shows a general increase in the whole model domain in both experiments, although the mean precipitation P mean decreases in the southern part of the area, especially in one of the experiments. The average yearly maximum six‐hour precipitation increases even more than the one‐day P max, suggesting a decrease in the timescale of heavy precipitation. The contrast between the P mean and P max changes in the southern part of the domain and the lack of such a contrast further north are affected by changes in wet‐day frequency that stem, at least in part, from changes in atmospheric circulation. However, the yearly extremes of precipitation exhibit a larger percentage increase than the average wet‐day precipitation. The signal‐to‐noise aspects of the model results are also studied in some detail. The 44 km grid‐box‐scale changes in P max are very heavily affected by inter‐annual variability, with an estimated standard error of about 20% for the 10‐year mean changes. However, the noise in P max decreases sharply toward larger horizontal scales, and large‐area mean changes in P max can be estimated with similar accuracy to those in P mean. Although a horizontal averaging of model results smooths out the small‐scale details in the true climate change signal as well, this disadvantage is, in the case of P max changes, much smaller than the advantage of reduced noise.  相似文献   
4.
The polythcrmal valley glacier Erikbreen (79°40'N 12°30'E), northern Spitsbergen, was investigated in 1970 and 1990 using digital photogrammetry and digital elevation model (DEM) techniques. The bottom topography was derived from radio-echo soundings. Based on the DEM, mass balance and changes of surface slope, crevasse and flow pattern were evaluated, and internal ice deformation velocities were calculated. Calculations of the total mass balance show that Erikbreen has not been in equilibrium for the last 20 years. The average surface lowering was 0.38 m/a and the volume had decreased by 5% to 6% from 1970 to 1990 or on the average by 3.5 × 10−1 water. The glacier surface subsided over the whole glacier area except in minor areas with northfacing slopes in the accumulation area. The surface slope and the crevasse pattern, however, did not change significantly during the 20-year-period, except in areas below 100 ma.s.l.  相似文献   
5.
The 456 ± 4 Ma Skattøra migmatite complex in thenorth Norwegian Caledonides consists of migmatitic nepheline-normativemetagabbros and amphibolites that are net-veined by numerousnepheline-normative anorthositic and leucodioritic dykes. Plagioclase(An20–50) is the dominant mineral (85–100%) in thedykes and the leucosome, but amphibole is generally presentin amounts up to 15%. The following observations strongly suggestformation of the anorthositic magma by anatexis of the surroundinggabbro in the presence of an H2O-bearing fluid phase: (1) themigmatites have plagioclase-rich (anorthositic) leucosomes andamphibole-rich restites; (2) crystallization of amphibole inthe anorthositic and leucodioritic dykes suggests high H2O activity;(3) the presence of coarse-grained to pegmatitic dykes and miaroliticcavities indicates a fluid-rich magma; (4) hydration zones thatsurround many anorthosite dykes suggest that the magma probablyexpelled H2O-rich fluids during crystallization. Water-saturatedmelting experiments at 0·5–1·5 GPa and temperaturesfrom 800 to 1000°C have been performed on a nepheline-normativegabbro to test the proposed petrogenesis of the Skattøraanorthosites. The glasses produced close to the solidus aretonalitic in composition, but they become richer in plagioclaseat higher temperatures. At and below 1·0 GPa, the residuesare composed of amphibole. Experiments above 1·0 GPaproduced residual garnet and/or zoisite in addition to amphibole,suggesting that the anorthositic dykes in the Skattøramigmatite complex formed below 1·25 GPa. The experimentsshow that the high Na2O content of the anorthosite dykes canonly be produced if Na is added to the charges. The glass thatbest fits the composition of the Skattøra dykes was producedat 1·0 GPa and 900°C with 2 wt % Na(OH) added. KEY WORDS: anorthosite; dyke swarm; anatexis; experimental petrology  相似文献   
6.
Compiled data from published and unpublished sources on copepod grazing of the large-sized copepods in the Barents Sea give wide ranges in grazing rates. Approximate average values indicate daily rations of 7–18% for copepodite stages V and VI and considerably higher values for the earliest copepodite stages. It is demonstrated that individual variability in gut fullness of copepods from a given locality is typically very high and not closely related to variable food abundance or depth of occurrence. There is no diel feeding rhythm during the summer, and even when relating copepod grazing to a number of biotic and abiotic factors through stepwise linear regression analysis, much of the variability remains unexplained. It is suggested that feeding behaviour, food quality and feeding history of the copepods all play important roles as factors which regulate copepod grazing. Model simulations on the phytoplankton succession, using literature data on laboratory-determined growth characteristics for solitary cells and colonies of the prymnesiophyte Phaeocystis pouchetii and large diatoms, indicate that the extent of the mixed layer and selective grazing by zooplankton are important factors that may explain the occurrence of dense blooms of P. pouchetii colonies, frequently observed during the spring.  相似文献   
7.
The mandible of a polar bear (Ursus maritimus Phipps) found in about 1920 at Kjul Å, North Jutland, and described by Nordmann & Degerbol in 1930. has been l4C dated to 11.100 ± 160 B.P. It is so far the only find of polar bear in Denmark. Comparison with recent 14C datings of Swedish and Norwegian polar bears shows that the Danish specimen was a member of a southern Scandinavian Late Weichselian population. The contemporaneous Zirphaeu sea deposits can be regarded as the boreal-arctic shallow water equivalent of the arctic Upper Saxicava sand deposits from northern Jutland. The polar bear mandible, however, was deposited on land, as was the metacarpal bone of a brown bear ( Ursus arctos ) from the nearby Nr. Lyngby locality of Allerød age. The overall picture of the Late Weichselian mammal fauna in Denmark shows a mixed composition of different ecotypes. Their sympatric occurrence points at a unique environment not comparable to any now existing, and probably related to the very low latitude of the Weichselian ice sheet.  相似文献   
8.
In this study, the clay and heavy mineral analysis of ODP Site 911 sediments is used to investigate the sources and transport mechanisms (sea ice and oceanic currents) of sediments in the Arctic Ocean during the Mid to Late Pliocene (3.10–2.78 Myr) and upper Quaternary (800 kyr to the present). The time period between 3.10 and 3.00 Myr is characterized by a decreasing smectite and increasing illite content, which is interpreted as reflecting cooling conditions. At the beginning of the Mid-Pliocene Global Warmth period at ∼3.00 Myr, the smectite content shows an abrupt increase. This change can also be seen as a drop in the amount of kaolinite and TOC. After 3.00 Myr the kaolinite and TOC values start to increase, probably indicating high rates of reworked glacially eroded matter. During the Pleistocene, smectite shows a lower and illite a higher fluctuation level compared with the Pliocene. This might be due to reigning glacial conditions during the Pleistocene, when the freshwater input was much lower than during the Pliocene. During the Pliocene, the fluctuating heavy minerals might reflect changes in freshwater input from the great Siberian rivers, which would have led to changes in the supply of terrigenous material delivered to the shelf by the rivers. The heavy mineral fluctuation also reflects changes in the amount of sea-ice formation, which correlates with climate variations and the freshwater input from the continent. Based on the composition of the clay and heavy mineral groups in this study, the most likely transportation path is the Siberian branch of the Transpolar Drift.  相似文献   
9.
Concentrations (ppm = ug/g dry weight) of total mercury (Hg) were determined in hair of polar bears ( Ursus maritimus) from northwestern Greenland (N = 22; period of sampling: 1978-1989), eastern Greenland (N = 44: 1984-1989) and Svalbard (N = 31; 1980). For subadults (2-6 years of life), adults (7-10 years). and old bears (>10 years), concentrations of total Hg in hair were not found to be dependent on age or sex. A decreasing trend in Hg concentrations was found from west to east. The mean concentrations of total Hg in hair (cubs of the year and yearlings excluded) were: northwestern Greenland, x = 8.38 ppm (min.-max.: 4.71-14.19 ppm. N = 21); eastern Greenland: x = 4.58 ppm (min.-max.: 2.50-8.83 ppm. N = 41); and Svalbard, x = 1.98 ppm (min.-max.: 1.02-4.55 ppm, N = 29). Concentrations found in northwestern Greenland were similar to those reported by others from the hair of polar bears sampled within management zone F of the eastern Canadian High Arctic. Concentrations of total Hg in polar bear hair from eastern Greenland were similar to concentrations found by others in contemporary (1988) material collected during spring in western Svalbard. However, the mean concentration of total Hg in the 1980 Svalbard material, which was collected during July-September, was significantly lower than concentrations found in samples taken during late winter and spring in eastern Greenland and at Svalbard, respectively. Presumably the relatively low concentrations found in the 1980 Svalbard sample arc attributable to the period of moult and hence a larger proportion of newly grown hair in the individual samples. In a subsample consisting of internal tissues from 19 polar bears from eastern Greenland (1984-1987), concentrations of total Hg in hair correlated positively with concentrations of total Hg (wet weight) in muscle (N = 6), liver (N = 19) and kidney (N = 19) tissue. For liver and kidney tissue these relationships were statistically significant.  相似文献   
10.
Distribution and life history of krill from the Barents Sea   总被引：2，自引：0，他引：2  
Krill from the Barents Sea were studied on six cruises from 1985 to 1989. Thysanoessa inermis and T. longicaudata were the dominant species, while T. raschii and Meganyctiphanes norvegica were rarer in the studied areas. The two dominant species T. inermis and T. longicaudata are mainly found in the Atlantic. Water and they do not to a large extent penetrate into Arctic water masses in the northern Barents Sea. M. norvegica is a more strict boreal species that does not occur as extensively in the Barents Sea as do the Thysanoessa species. The mean population abundance ranged from 1 to 61 individuals m−2 for T. inermis and from 2 to 52 ind. M−2 for T. longicaudata . The mean dry weight biomass of these two species ranged from 14 to 616 and from 19 to 105 mg−2. Length frequency distributions indicate a life span of just over two years for T. inermis and T. longicaudata . Growth took place from about April to autumn with no apparent growth during winter. Maturation and spawning seem to occur after two years for T. inermis and one year for T. longicaudata . Main spawning occurred from May to June coinciding with the spring phytoplankton bloom. Captive spawners of T. inermis (total length 17-22 mm) shed 30-110 eggs per female in a single batch.  相似文献   
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