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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   
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The effect of cadmium on the growth of an intertidal marine gastropod, Nassarius festivus, was investigated using a number of biomarkers namely conventional measurements in terms of increase in shell length or body weight, scope for growth (SfG) and RNA/DNA ratio. After eight days of cadmium exposure, the no observable effect concentration (NOEC) and lowest observable effect concentration (LOEC) for the rate of increase in wet weight were 1.00 and 1.38 mg/l, respectively, while those for shell length did not show any significant difference from the control until day 16. After 16 days of cadmium exposure, the LOEC for both shell length and wet weight measurements was 0.22 mg/l. The 8-day SfG test was sensitive to cadmium stress, showing a significant decrease at 0.16 mg/l cadmium when compared to the control. The NOEC and LOEC of RNA/DNA ratio determination were 0.52 and 0.93 mg/l, respectively. An assessment based on sensitivity and technical complexity suggests that Scope for Growth is the most sensitive growth biomarker, followed by the RNA/DNA ratio, and then the conventional growth measurement based on shell size and body weight.  相似文献   
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In this article we treat the 'Extended Sitnikov Problem' where three bodies of equal masses stay always in the Sitnikov configuration. One of the bodies is confined to a motion perpendicular to the instantaneous plane of motion of the two other bodies (called the primaries), which are always equally far away from the barycenter of the system (and from the third body). In contrary to the Sitnikov Problem with one mass less body the primaries are not moving on Keplerian orbits. After a qualitative analysis of possible motions in the 'Extended Sitnikov Problem' we explore the structure of phase space with the aid of properly chosen surfaces of section. It turns out that for very small energies H the motion is possible only in small region of phase space and only thin layers of chaos appear in this region of mostly regular motion. We have chosen the plane ( ) as surface of section, where r is the distance between the primaries; we plot the respective points when the three bodies are 'aligned'. The fixed point which corresponds to the 1 : 2 resonant orbit between the primaries' period and the period of motion of the third mass is in the middle of the region of motion. For low energies this fixed point is stable, then for an increased value of the energy splits into an unstable and two stable fixed points. The unstable fixed point splits again for larger energies into a stable and two unstable ones. For energies close toH = 0 the stable center splits one more time into an unstable and two stable ones. With increasing energy more and more of the phase space is filled with chaotic orbits with very long intermediate time intervals in between two crossings of the surface of section. We also checked the rotation numbers for some specific orbits. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
5.
Three-fold subdivision of the Allerød chronozone   总被引：1，自引：0，他引：1  
A pollen diagram of a calcareous travertine bed near Kirf (West Germany) shows a tripartition of the Allerød chronozone. In northwestern and central-European diagrams this is not an uncommon phenom-enon. Arguments supporting a deduced climatic oscillation may also be derived from the average ice recession in southern Sweden, the Coleoptera assemblages in northwestern England, the isotope 180/16O curve from the Gerzensee in Switzerland, and the Camp Century Ice Core in Greenland. The included sandy Laachcr See ash may suggest explosive volcanism again to be somehow related to inferred climatic changes.  相似文献   
6.
Seismoacoustic profiles from the Arkona Basin show a late Pleistocene and Holocene succession of several distinct reflectors. The physical, sedimentological, mineralogical and geochemical properties of more than 30 sediment cores were analysed in order to assign these reflectors to specific sedimentary discontinuity layers. Additionally, AMS 14C data and biostratigraphic information were gathered. Based on this multi‐proxy approach, seven lithostratigraphic units (AI, AII, B to F) were distinguished. These consist of fine‐grained clay, silt and mud, and are separated from each other by thin basin‐wide traceable sandy layers (Sab‐Sef). The most sensitive parameter to mark the lithostratigraphic boundaries is the weight percentage of the grain‐size fraction >63μm. In addition, some of the quartz‐grain‐dominated sandy layers cause the strong reflection lines recorded in seismoacoustic profiles. The sandy layers are interpreted to reflect enhanced hydrodynamic energy induced by episodes of basin‐wide water‐level low‐stand conditions. These low stands resulted from water‐level drops that occurred frequently during the Baltic Sea's history and presumably affected the entire Baltic basin. The thick fine‐grained units AI, AII to F, in which coarser material is absent, represent water‐level high‐stands. We conclude that the units AI and AII are Baltic Ice Lake sediments deposited before and after the Billingen‐1 regression, respectively. We assign the most prominent sandy layer Sab to the final drainage of the Baltic Ice Lake (Billingen‐2), whereas the sandy layers between units B, C., D and E are related to the Yoldia Sea and Ancylus Lake regressions of the Baltic Sea's history. The uppermost fine‐grained unit F with its high organic carbon content contains marine sediments deposited after the Littorina Transgression. The macroscopically well‐visible sediment colour change from reddish/brown‐to‐grey, previously interpreted as a regional stratigraphic boundary, varies from core to core. It has been shown by our new data that this colour change has a diagenetic origin, and thus does not represent a stratigraphic boundary. Previous subdivisions therefore have to be revised.  相似文献   
7.
The present study examines sedimentation rates in the eastern Gotland Basin using a variety of methods that reveal considerable heterogeneity in the rates, both spatially and temporally. High-resolution seismic recordings and correlation with long sediment cores indicate increased thickness of strata and higher sedimentation rates (0.75 mm a -1 ) in the eastern part of the basin than in the western part (0.23 mm a -1 ) since the Littorina transgression some 8000 14 C years BP. This difference is apparently a consequence of a counterclockwise near-bottom circulation in the basin with periodically high current speeds that cause winnowing on the steep SE slope of the basin and differential settling of sediments in areas of low current speeds. On shorter time scales, recent sediment accumulation rates based on radiometric dating ( 210 Pb) are in general twice as high as those observed 25 years ago using the same method. The higher modern rates, compared to those of the 1970s, may partly be due to increased eutrophication, as more carbon is buried in the sediment, and partly due to increased erosion in shallow water areas. However, strong lateral variations are evident. The average sediment accumulation rates vary between 119 and 340 g m -2 a -1 (corresponding to sedimentation rates of 2.1-2.5 mm a -1 ) in the deepest part of the basin. Very high rates (6100 g m -2 a -1 , corresponding to sedimentation rates of 30 mm a -1 ) are observed on an intraslope basin site (offshore Latvia) at a water depth of only 70 m. The radiometrically determined sediment accumulation rates are up to three times higher than those estimated from average water column concentrations of suspended matter and from sediment trap flux rates. The discrepancy suggests that sedimentation in the deep basin may have a substantial contribution from near-bottom lateral transport.  相似文献   
8.
Daily maximum and minimum temperatures from 29 low-lying and mountain stations of 7 countries in Central Europe were analyzed. The analysis of the annual variation of diurnal temperature range helps to distinguish unique climatic characteristics of high and low altitude stations. A comparison of the time series of extreme daily temperatures as well as mean temperature shows a good agreement between the low-lying stations and the mountain stations. Many of the pronounced warm and cold periods are present in all time series and are therefore representative for the whole region. A linear trend analysis of the station data for the period 1901–1990 (19 stations) and 1951–1990 (all 29 stations) shows spatial patterns of similar changes in maximum and minimum daily temperatures and diurnal temperature range. Mountain stations show only small changes of the diurnal temperature range over the 1901–1990 period, whereas the low-lying stations in the western part of the Alps show a significant decrease of diurnal temperature range, caused by strong increase of the minimum temperature. For the shorter period 1951–1990, the diurnal temperature range decreases at the western low-lying stations, mainly in spring, whereas it remains roughly constant at the mountain stations. The decrease of diurnal temperature range is stronger in the western part than in the eastern part of the Alps.  相似文献   
9.
Pollen analysis and radiocarbon dating of a core section from the valley head of the Husterbaach near Hosingen (Oesling) provides a very detailed record of the successive vegetations from 1200 A. D. until today. This palynological record agrees largely with the consecutive events known from the agricultural history of that area. Particularly significant are the curves obtained of several cultivated and ruderal plants. In this section it could be demonstrated that the interruption of peat growth by deposition of minerogenic material corresponds with a comparatively high arable land/pasture ratio. As well as being intrinsically interesting for assessing which features of the present landscape are due to former human activities, a detailed knowledge of the Subatlantic evolution of the vegetation and land use in the Oesling is indispensable, as its geomorphological development in the immediate past has largely been influenced by man.  相似文献   
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