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1.
Neotectonics, sea-level changes and biological evolution in the Fennoscandian Border Zone of the southern Kattegat Sea 总被引:1,自引:0,他引:1
JØRN BO JENSEN KAJ STRAND PETERSEN PETER KONRADI ANTOON KUIJPERS OLE BENNIKE WOLFRAM LEMKE RUDOLF ENDLER 《Boreas: An International Journal of Quaternary Research》2002,31(2):133-150
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.
Late- and postglacial history of the Great Belt, Denmark 总被引:3,自引:0,他引:3
OLE BENNIKE JØRN BO JENSEN WOLFRAM LEMKE ANTOON KUIJPERS STEEN LOMHOLT 《Boreas: An International Journal of Quaternary Research》2004,33(1):18-33
On the basis of shallow seismic records, vibrocoring, macrofossil analyses and AMS radiocarbon-dating, five stratigraphical units have been distinguished from the deepest parts of the central Great Belt (Storebælt) in southern Scandinavia. Widespread glacial deposits are followed by two lateglacial units confined to deeply incised channels and separated by an erosional boundary. Lateglacial Unit I dates from the time interval from the last deglaciation to the Allerød; lateglacial Unit II is of Younger Dryas age. Early Holocene deposits show a development from river deposits and lake-shore deposits to large lake deposits, corresponding to a rising shore level. Lake deposits are found up to 20 m below the sea floor, and the lake extended over some 200–300 km2. The early Holocene freshwater deposits are dated to the time interval c. 10900 to c. 8800 cal. yr BP and the oldest shells of marine molluscs from the Great Belt are dated to c. 8100 cal. yr BP. 相似文献
3.
CALVIN J. HEUSSER THOMAS V. LOWELL LINDA E. HEUSSER ARTURO HAUSER BJ
RN G. ANDERSEN GEORGE H. DENTON 《第四纪科学杂志》1996,11(3):173-184
Palaeoecological studies carried out in the Chilean Lake District and Chilotan Archipelago (41°–43°S) record full-glacial and late-glacial pollen assemblages beginning just after 21000 and beetle assemblages after 18000, both sets extending until 10000 14C yr BP. Pollen records indicate that Subantarctic Parkland, the vegetation of the early millennia of record, changed after about 14000 yr BP to become open woodland and later North Patagonian Evergreen Forest. Assemblages of plants and beetles, responding more or less in unison to a strong rise in temperature (≥ 6°C), behaved in accord at around 14000 until 13000–12500 yr BP, the beetle fauna displaying a marked increase in obligate forest types. During full-glacial conditions (17400–16100 and 15300 and 14400 yr BP) and in the late-glacial interval (after about 13000 yr BP), however, climate evidently coerced populations dissimilarly, the pollen sequence showing an increase in plant taxa indicative of colder climate, whereas the beetle fauna underwent little or no variation. Contrasting climate modes implied by plants and beetles may be attributed to differential responses to apparent low-order temperature changes (≤ 2–3°C). 相似文献
4.
Tess Olivia Bamber Angus Charles Jackson Robert Philip Mansfield 《Ocean Science Journal》2018,53(2):215-224
Increasing concentrations of atmospheric carbon dioxide are causing oceanic pH to decline worldwide, a phenomenon termed ocean acidification. Mounting experimental evidence indicates that near-future levels of CO2 will affect calcareous invertebrates such as corals, molluscs and gastropods, by reducing their scope for calcification. Despite extensive research into ocean acidification in recent years, the effects on non-calcifying anthozoans, such as sea anemones, remain little explored. In Western Europe, intertidal anemones such as Actinia equina are abundant, lower trophic-level organisms that function as important ecosystem engineers. Changes to behaviours of these simple predators could have implications for intertidal assemblages. This investigation identified the effects of reduced seawater pH on feeding and contest behaviour by A. equina. Video footage was recorded for A. equina feeding at current-day seawater (pH 8.1), and the least (pH 7.9) and most (pH 7.6) severe end-of-century predictions. Footage was also taken of contests over ownership of space between anemones exposed to reduced pH and those that were not. No statistically significant differences were identified in feeding duration or various aspects of contest behaviour including initiating, winning, inflating acrorhagi, inflicting acrorhagial peels and contest duration. Multivariate analyses showed no effect of pH on a combination of these variables. This provides contrast with other studies where anemones with symbiotic algae thrive in areas of natural increased acidity. Thus, novel experiments using intraspecific contests and resource-holding potential may prove an effective approach to understand sub-lethal consequences of ocean acidification for A. equina, other sea anemones and more broadly for marine ecosystems. 相似文献
5.
VALENTIN BURKI LOUISE HANSEN OLA FREDIN THORBJØRN A. ANDERSEN ACHIM A. BEYLICH MICHEL JABOYEDOFF EILIV LARSEN JAN‐FREDERIK TØNNESEN 《Boreas: An International Journal of Quaternary Research》2010,39(3):551-566
Burki, V., Hansen, L., Fredin, O., Andersen, T. A., Beylich, A. A., Jaboyedoff, M., Larsen, E. & Tønnesen, J.‐ F. 2009: Little Ice Age advance and retreat sediment budgets for an outlet glacier in western Norway. Boreas, Vol. 39, pp. 551–566. 10.1111/j.1502‐3885.2009.00133.x. ISSN 0300‐9483 Bødalsbreen is an outlet glacier of the Jostedalsbreen Ice Field in western Norway. Nine moraine ridges formed during and after the maximum extent of the Little Ice Age (LIA). The stratigraphy of proglacial sediments in the Bødalen basin inside the LIA moraines is examined, and corresponding sediment volumes are calculated based on georadar surveys and seismic profiling. The total erosion rates (etot) by the glacier are determined for the periods AD 1650–1930 and AD 1930–2005 as 0.8 ± 0.4 mm/yr and 0.7 ± 0.3 mm/yr, respectively. These rates are based on the total amount of sediment delivered to the glacier margin. The values are almost one order of magnitude higher than total erosion rates previously calculated for Norwegian glaciers. This is explained by the large amount of pre‐existing sediment that was recycled by Bødalsbreen. Thus, the total erosion rate must be considered as a composite of eroded bedrock and of removed pre‐existing sediments. The total erosion rate is likely to vary with time owing to a decreasing volume of easily erodible, unconsolidated sediment and till under the glacier. A slight increase in the subglacial bedrock erosion is expected owing to the gradually increasing bedrock surface area exposed to subglacial erosion. 相似文献
6.
BJÖRN HOLMER SOFIA THORSSON INGEGÄRD ELIASSON 《Geografiska Annaler: Series A, Physical Geography》2007,89(4):237-248
Intra‐urban cooling rates were monitored for a year in the centre of Göteborg on the Swedish west coast. Five sites with different building geometry ‐ from dense canyon to open space ‐ within a radius of 300 m were analysed. Results showed two modes of cooling during the night. In the first mode, the cooling was site‐dependent ‐the open space cooled the most and the dense canyon the least. In the second mode, which began about 3–4 hours after sunset, all sites cooled at the same rate. Our hypothesis is that in the early part of the evening both radiative divergence and sensible heat dominate the cooling. However, as the evening progresses, a spatially homogeneous inversion is established which controls the radiative cooling, making the cooling independent of both surface geometry and surface type. From April to November the sites cooled rapidly around sunset and the cooling slowly decreased during the rest of the night. However, between December and March, the cooling was less intense, with an almost constant rate during the entire night. It has been suggested that this might be the result of the draining of stored solar heat during the summer and a continuous flux of anthropogenic heating during the winter. 相似文献
7.
Two raised marine sequences from Prins Karls Forland, western Svalbard, interpreted to have been deposited during part of isotope substage 5e (Eemian) and substage 5a, were studied for foraminifera content. Time constraints are given by 14 C ages, infrared stimulated luminescence age estimates and amino acid ratios in subfossil marine molluscs. A diamicton (unit B) separates the two marine sequences and reflects an advancement of local glaciers sometime late in isotope stage 5. The two marine sequences contain diverse benthic foraminiferal faunas, indicating periods of a relatively warm and seasonally ice-free marine shelf environment. Compared to the lowermost sequence (unit A), the upper marine sequence (unit C) seems to reflect a more shallow environment that could have resulted from the global lowering of the sea level towards the end of isotope stage 5. Our results further emphasise the problem of biostratigraphic distinction between interglacial and interstadial deposits at high latitudes, with temperature conditions for substage 5a close to those of substage 5e and present conditions. 相似文献
8.
Eemian and Weichselian stratigraphy in South Sweden 总被引:1,自引:0,他引:1
BJÖRN E. BERGLUND ERIK LAGERLUND 《Boreas: An International Journal of Quaternary Research》1981,10(4):323-362.
The stratigraphy of Pleistocene sequences within three main areas of the province of Skane, South Sweden, is discussed. The traditional stratigraphy is revised. New lithostratigraphic units are deficned and named according to international stratigraphic terminology. Lithostratigraphical correaltions are based on sedimentological development and palaeoenvironmental changes. Organic beds are correlated with the Eemain interglacial and some of the Early and Middle Weichselian interstadials. The chronostratigraphic key site, Stenberget, is described in greater detail. Stratrigraphy and palaeoenvironment are summarized in a scheme indicating that South Sweden was glaciated only during the period 21,000–13,000 B.P. 相似文献
9.
A simple climate model has been developed to investigate the existence of the small ice cap instability in the Southern Hemisphere.
The model consists of four coupled components: an atmospheric energy balance model, a thermodynamic snow-sea ice model, an
oceanic mixed layer model and a terrestrial ice model. Results from a series of experiments involving different degrees of
coupling in the model show that the instability appears only in those cases when an explicit representation of the Antarctic
ice sheet is not included in the model. In order to determine which physical processes in the ice sheet model lead to a stabilization
of the system we have conducted several sensitivity experiments in each of which a given ice sheet process has been removed
from the control formulation of the model. Results from these experiments suggest that the feedback between the elevation
of the ice sheet and the snow accumulation-ice ablation balance is responsible for the disappearance of the small ice cap
instability in our simulation. In the model, the mass balance of the ice sheet depends on the air temperature at sea level
corrected for altitude and it is, therefore, a function of surface elevation. This altitude-mass balance feedback effectively
decouples the location of the ice edge from any specific sea level isotherm, thus decreasing the model sensitivity to the
albedo-temperature feedback, which is responsible for the appearance of the instability. It is also shown that the elevation-radiative
cooling feedback tends to stabilize the ice sheet, although its effect does not seem to be strong enough to remove the instability.
Another interesting result is that for those simulations which include the terrestrial ice model with elevation-dependent
surface mass balance, hysteresis is exhibited, where for a given level of external forcing, two stable solutions with different,
non-zero ice-sheet volume and area and different air and ocean temperature fields occur. However, no unstable transition between
the two solutions is ever observed. Our results suggest that the small ice cap instability mechanism could be unsuitable for
explaining the inception of glaciation in Antarctica.
Received: 14 April 1997 / Accepted: 22 October 1997 相似文献
10.
JAN MANGERUD BJÖRN E. BERGLUND 《Boreas: An International Journal of Quaternary Research》1978,7(3):179-181
The proposal for Quaternary stratigraphy of Norden published 1974 by Mangerud, Andersen, Berglund & Donner was discussed at a Nordie meeting 1978. On the basis of this discussion some recommendations are proposed here which deviate slightly from the 1974 proposal: (1) the term Flandrian should not be used in Norden until it is properly defined in the type area, (2) the Middle/Late Weichselian boundary should provisionally be defined as 25,000 14 C years B. P. In addition it was stated that there is an urgent need for complete subdivision of the Weichselian into a continuous chronozone sequence. 相似文献