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1.
The coastal zone of Norrbotten, northern Sweden, was gradually inundated by the Ancylus Lake following the retreating ice margin and forming a highest coastline approximately 210 m above the present sea level. The succeeding shore displacement is reconstructed based on lithological investigations and radiocarbon datings of identified isolation sequences from 12 cored lake basins. The highest lake basins, along with two basins above the highest shoreline, suggest ice-free conditions already at 10 500 cal. yr BP. This is at least 500 years earlier than previously thought and implies rapid ice-sheet break-up in the Gulf of Bothnia. The shore displacement (RSL) curve represents a forced regression of successively decreasing rate through the Holocene, from 9 m/100 yr to 0.8 m/100 yr. During the first 1000-1200 years, the isostatic uplift is exponentially declining, followed by a constant uplift rate from c. 9500 cal. yr BP to 5500-5000 cal. yr BP. The last 5000 years seem to be characterized by a low but constant rebound rate. The development of the Ancylus Lake stage of the Baltic may also be discerned in the Norrbotten RSL curve, suggesting that the chronology of the Ancylus Lake stages may have to be revised. The Littorina transgression is also reflected by the RSL curve shape. In addition, a series of early to mid-Holocene beach terraces were OSL-dated to allow for comparison with the 14C-dated shore displacement curve. Interpretations of these ages and their relation to former sea levels were clearly more problematic than the dating of the lake basin isolations.  相似文献   

2.
Jensen, J. B., Bennike, O., Witkowski, A., Lemke, W. & Kuijpers, A. 1997 (September): The Baltic Ice Lake in the southwestern Baltic: sequence-, chrono- and biostratigraphy. Boreas , Vol. 26, pp. 217–236. Oslo. ISSN 0300–9483.
This multidisciplinary study focuses on late-glacial deposits in the Mecklenburg Bay -Arkona Basin area. The sequence stratigraphical method has been used on shallow seismic and lithological data, in combination with biostratigraphical work and radiocarbon dating. Glacial-till deposits underlie sediments from two Baltic Ice Lake phases. Varved clay deposits from the initial phase cover the deepest parts of the basins. A prograding delta is observed at the western margin of the Arkona Basin, prograding from the Darss Sill area. The delta system is possibly related to a highstand dated at 12.8 ka. A maximum transgression level around 20 m below present sea level (b.s.l.) is inferred, followed by a drop in water level and formation of lowstand features. The final ice lake phase is characterized by a new transgression. The transgression maximum as observed in the Mecklenburg Bay is represented by transgressive and highstand deltaic deposits. These also indicate a maximum shore level of 20 m b.s.l. The deltaic sediments that contain macroscopic plant remains and diatoms have yielded Younger Dryas ages. Mapping of the late-glacial morphology of the Darss Sill area reveals a threshold at 23 to 24 m b.s.l. This means that the Baltic Ice Lake highstand phases inundated the Darss Sill, which implies that the westernmost extension of the Baltic Ice Lake reached as far as Kiel Bay. Forced regressive coastal deposits at the western margin of the Arkona Basin mark a lowstand level of around 40 m b.s.l. caused by the final drainage of the Baltic Ice Lake. The lowstand deposits predate lacustrine deposits from the Ancylus Lake, which date to approximately 9.6 ka BP.  相似文献   

3.
A mean varve thickness curve has been constructed for a part of the Swedish varve chronology from the northwestern Baltic proper. The mean varve thickness curve has been correlated with the δ18O record from the GRIP ice-core using the Younger Dryas–Preboreal climate shift. This climate shift was defined by pollen analyses. The Scandinavian ice-sheet responded to a warming at the end of the Younger Dryas, ca. 10995 to 10700 clay-varve yr BP. Warming is recorded as a sequence of increasing mean varve thickness and ice-rafted debris suggesting intense calving of the ice front. The Younger Dryas–Preboreal climatic shift is dated to ca. 10650 clay-varve yr BP, about 40 yr after the final drainage of the Baltic Ice Lake. Both the pollen spectra and a drastic increase in varve thickness reflect this climatic shift. A climate deterioration, correlated with the Preboreal oscillation, is dated to ca. 10440 to 10320 clay-varve yr BP and coincides with the brackish water phase of the Yoldia Sea stage. The ages of the climatic oscillations at the Younger Dryas–Preboreal transition show an 875 yr discrepancy compared with the GRIP record, suggesting a large error in the Swedish varve chronology in the part younger than ca. 10300 clay-varve yr BP. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

4.
The outer coast of Finnmark in northern Norway is where the former Fennoscandian and Barents Sea ice sheets coalesced. This key area for isostatic modelling and deglaciation history of the ice sheets has abundant raised shorelines, but only a few existing radiocarbon dates constrain their chronology. Here we present three Holocene sea level curves based on radiocarbon dated deposits from isolation basins at the outermost coast of Finnmark; located at the islands Sørøya and Rolvsøya and at the Nordkinn peninsula. We analysed animal and plant remains in the basin deposits to identify the transitions between marine and lacustrine sediments. Terrestrial plant fragments from these transitions were then radiocarbon dated. Radiocarbon dated mollusk shells and marine macroalgae from the lowermost deposits in several basins suggest that the first land at the outer coast became ice free around 14,600 cal yr BP. We find that the gradients of the shorelines are much lower than elsewhere along the Norwegian coast because of substantial uplift of the Barents Sea. Also, the anomalously high elevation of the marine limit in the region can be attributed to uplift of the adjacent seafloor. After the Younger Dryas the coast emerged 1.6–1.0 cm per year until about 9500–9000 cal yr BP. Between 9000 and 7000 cal yr BP relative sea level rose 2–4 m and several of the studied lakes became submerged. At the outermost locality Rolvsøya, relative sea level was stable at the transgression highstand for more than 3000 years, between ca 8000 and 5000 cal yr BP. Deposits in five of the studied lakes were disturbed by the Storegga tsunami ca 8200–8100 cal yr BP.  相似文献   

5.
Based on geological and archaeological proxies from NW Russia and NE Estonia and on GIS‐based modelling, shore displacement during the Stone Age in the Narva‐Luga Klint Bay area in the eastern Gulf of Finland was reconstructed. The reconstructed shore displacement curve displays three regressive phases in the Baltic Sea history, interrupted by the rapid Ancylus Lake and Litorina Sea transgressions c. 10.9–10.2 cal. ka BP and c. 8.5–7.3 cal. ka BP, respectively. During the Ancylus transgression the lake level rose 9 m at an average rate of about 13 mm per year, while during the Litorina transgression the sea level rose 8 m at an average rate of about 7 mm per year. The results show that the highest shoreline of Ancylus Lake at an altitude of 8–17 m a.s.l. was formed c. 10.2 cal. ka BP and that of the Litorina Sea at an altitude of 6–14 m a.s.l., c. 7.3 cal. ka BP. The oldest traces of human activity dated to 8.5–7.9 cal. ka BP are associated with the palaeo‐Narva River in the period of low water level in the Baltic basin at the beginning of the Litorina Sea transgression. The coastal settlement associated with the Litorina Sea lagoon, presently represented by 33 Stone Age sites, developed in the area c. 7.1 cal. ka BP and existed there for more than 2000 years. Transformation from the coastal settlement back to the river settlement indicates a change from a fishing‐and‐hunting economy to farming and animal husbandry c. 4.4 cal. ka BP, coinciding with the time of the overgrowing of the lagoon in the Narva‐Luga Klint Bay area.  相似文献   

6.
A zone of synchronous end moraines has been recognized in the Lake Superior region across northern Ontario and Michigan. The moraines were formed between 11,000 and 10,100 y.a. as cold climate resulted in successive halts in the general ice retreat. The cold climate is also indicated by the presence of tundra near Lake Superior until about 10,000 y.a. This episode is here referred to as the Algonquin Stadial. It was preceded and followed by rapid deglaciation. The Algonquin Stadial is comparable in age with the Younger Dryas Stadial of Europe, and indicates a reversal in the continuous trend toward a warmer climate during Late-Wisconsin (an) time. The apparent conflict between the present result (based on geologic evidence) and earlier pollen stratigraphical studies with no reversal is discussed.Glacial Lake Duluth formed in the western Lake Superior basin before 11,000 BP, followed by a series of Post-Duluth lakes between approximately 11,000 and over 10,100 BP. The Main Lake Algonquin stage in the Huron and Michigan basins terminated approximately 11,000 BP. The subsequent high-level post-Main Algonquin lakes, which were contemporaneous with the Post-Duluth lakes, existed in the southeastern Lake Superior basin. When the ice margin was along the north shore 9500 BP Lake Minong occupied the whole Lake Superior basin. By 9000 BP the ice had retreated north of Lake Superior-Hudson Bay divide.  相似文献   

7.
Lake Vättern represents a critical region geographically and dynamically in the deglaciation of the Fennoscandian Ice Sheet. The outlet glacier that occupied the basin and its behaviour during ice‐sheet retreat were key to the development and drainage of the Baltic Ice Lake, dammed just west of the basin, yet its geometry, extent, thickness, margin dynamics, timing and sensitivity to regional retreat forcing are rather poorly known. The submerged sediment archives of Lake Vättern represent a missing component of the regional Swedish deglaciation history. Newly collected geophysical data, including high‐resolution multibeam bathymetry of the lake floor and seismic reflection profiles of southern Lake Vättern, are used here together with a unique 74‐m sediment record recently acquired by drill coring, and with onshore LiDAR‐based geomorphological analysis, to investigate the deglacial environments and dynamics in the basin and its terrestrial environs. Five stratigraphical units comprise a thick subglacial package attributed to the last glacial period (and probably earlier), and an overlying >120‐m deglacial sequence. Three distinct retreat–re‐advance episodes occurred in southern Lake Vättern between the initial deglaciation and the Younger Dryas. In the most recent of these, ice overrode proglacial lake sediments and re‐advanced from north of Visingsö to the southern reaches of the lake, where ice up to 400 m thick encroached on land in a lobate fashion, moulding crag‐and‐tail lineations and depositing till above earlier glacifluvial sediments. This event precedes the Younger Dryas, which our data reveal was probably restricted to north‐central sectors of the basin. These dynamics, and their position within the regional retreat chronology, indicate a highly active ice margin during deglaciation, with retreat rates on average 175 m a?1. The pronounced topography of the Vättern basin and its deep proglacial‐dammed lake are likely to have encouraged the dynamic behaviour of this major Fennoscandian outlet glacier.  相似文献   

8.
One of the most discussed stages in the history of the Baltic Sea is the Ancylus Lake phase. This paper presents detailed information from the Darss Sill threshold area as well as the adjacent basins, i.e. the Mecklenburg Bay and Arkona Basin located in the southwesternmost Baltic. The threshold area was transgressed at the Baltic Ice Lake maximum phase and during the following regression about 10.3 ka BP a river valley was incised in the Darss Sill to a level of 23-24 m below present sea level (b.s.l.). Preboreal sediments in the study area show lowstand basin deposition in the Arkona Basin and the existence of a local lake in Mecklenburg Bay. The lowstand system is followed by the Ancylus Lake transgression that reached a maximum level of 19 m b.s.l. Thus, at the maximum level the water depth was about 5 m over the threshold, and the shore level fall during the Ancylus Lake regression must be in the same range. The Darss Sill area is the key area for drainage of the Ancylus Lake, and if the previously suggested regression of 8-10 m in southeastern Sweden is to be achieved, isostatic rebound must also play a role. The existence of the so-called Dana River in the Darss Sill area cannot be supported by our investigations. We observed no signs of progressive erosion of the Darss Sill area in the Early Holocene, and there are no prograding systems in Mecklenburg Bay that can be related to the Ancylus Lake regression. On the contrary, local lakes developed in Mecklenburg Bay and in the Darss Sill threshold area. In the Darss Sill area, marl was deposited in a lake in the valley that developed after the final drainage of the Baltic Ice Lake. Studies of diatoms and macrofossils, combined with seismic interpretation and radiocarbon dating, provide detailed information about the chronology and the relative shore level of these lake phases as well as about environmental conditions in the lakes.  相似文献   

9.
A high-resolution, well-dated dinoflagellate cyst record from a lagoon of the southeastern Swedish Baltic Sea reveals climate and hydrological changes during the Holocene. Marine dinoflagellate cysts occurred initially at about 8600 cal yr BP, indicating the onset of the Littorina transgression in the southeastern Swedish lowland associated with global sea level rise, and thus the opening of the Danish straits. Both the species diversity and the total accumulation rates of dinoflagellate cysts continued to increase by 7000 cal yr BP and then decreased progressively. This pattern reveals the first-order change in local sea level as a function of ice-volume-equivalent sea level rise versus isostatic land uplift. Superimposed upon this local sea level trend, well-defined fluctuations of the total accumulation rates of dinoflagellate cysts occurred on quasi-1000- and 500-yr frequency bands particularly between 7500 and 4000 cal yr BP, when the connection between the Baltic basin and the North Atlantic was broader. A close correlation of the total accumulation rates of dinoflagellate cysts with GISP2 ice core sea-salt ions suggests that fluctuations of Baltic surface conditions during the middle Holocene might have been regulated by quasi-periodic variations of the prevailing southwesterly winds, most likely through a system similar to the dipole oscillation of the modern North Atlantic atmosphere.  相似文献   

10.
The deglaciation pattern at Mt. Billingen, within the Middle Swedish end moraine zone, and its relationship with dramatic water level changes in the Baltic Ice Lake is a classic topic of Swedish Quaternary Geology. Based on data west of Mt. Billingen, the authors (in two earlier papers) presented a stratigraphic model associated with this subject. This study is an attempt to test the model east of Mt. Billingen, i.e. inside the Baltic Ice Lake itself. Lake Mullsjon is situated 30 km southeast of the drainage area of the Baltic Ice Lake and within the final drainage zone. About 8 m of Late Weichselian sediments (mostly varved clay) were recovered from the lake and analysed from different stratigraphic viewpoints, including lithology, grainsize, varve chronology, and pollen. These analyses show that the site was deglaciated in the later part of the Allerød Chronozone. Shortly thereafter the first drainage of the Baltice Ice Lake took place but without isolating Lake Mullsjon. After a short period of disturbed sedimentation varved clay continued to form as the glacier receded for another 120 varve years until the onset of the Younger Dryas cooling, as registered both in the pollen and in the varve stratigraphies. After c. another 120 varve years our analyses suggest that the Baltic Ice Lake was dammed once again. About 230 varve years of further ice readvance followed west of Mt. Billingen, while the ice margin in the east was more or less stationary. Rapid melting set in, at first producing coarse varves, but soon the clay was thin-varved and fine. This continued for 140 varve years until suddenly the lake became isolated. At this isolation thick beds of silty-sandy deposits were deposited on the lake floor. The isolation is dated to 10,400–10,500 14C years B.P., which corresponds to the assumed age of the final drainage of the Baltic Ice Lake. It was also isolated at the same time as lakes (on the same isobase) situated 20 m lower, but west of Mt. Billingen, were raised above sea level. This strongly suggests that Lake Mullsjön was isolated as an effect of the drainage of the Baltic Ice Lake. Significant differences between the clay-varve and the 14C chronologies are also presented.  相似文献   

11.
An analysis of Late Weichselian sediments from basins in southern and central Halland, southwestern Sweden was carried out. Together with evaluation of previously reported data from the area (isolated basins, highest shore levels, glaciofluvial delta levels, periglacial features, and early Holocene shore levels), this has provided the basis for constructing shore displacement curves for the area, covering the approximate time interval 14 000–9000 BP. There is a general fall in relative sea level (RSL) during this period. The average regression rate until the late Younger Dryas ( c . 10 300 BP) is 15–20 mm/yr. During the Younger Dryas the regression is possibly interrupted by minor transgressive phases. The RSL fall is rapid between c . 10 300 and 9500 BP. A halted glacio-isostatic rebound during the Younger Dryas, as the result of glacier growth, is suggested as a cause of the observed pattern of RSL change. Previously reported transgressive events during the early late-glacial phase are discussed with regard to global eustatic rise, glacio-isostatic loading and glaciolacustrine damming events.  相似文献   

12.
A detailed shoreline displacement curve documents the Younger Dryas transgression in western Norway. The relative sea‐level rise was more than 9 m in an area which subsequently experienced an emergence of almost 60 m. The sea‐level curve is based on the stratigraphy of six isolation basins with bedrock thresholds. Effort has been made to establish an accurate chronology using a calendar year time‐scale by 14C wiggle matching and the use of time synchronic markers (the Vedde Ash Bed and the post‐glacial rise in Betula (birch) pollen). The sea‐level curve demonstrates that the Younger Dryas transgression started close to the Allerød–Younger Dryas transition and that the high stand was reached only 200 yr before the Younger Dryas–Holocene boundary. The sea level remained at the high stand for about 300 yr and 100 yr into Holocene it started to fall rapidly. The peak of the Younger Dryas transgression occurred simultaneously with the maximum extent of the ice‐sheet readvance in the area. Our results support earlier geophysical modelling concluding a causal relationship between the Younger Dryas glacier advance and Younger Dryas transgression in western Norway. We argue that the sea‐level curve indicates that the Younger Dryas glacial advance started in the late Allerød or close to the Allerød–Younger Dryas transition. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

13.
The shore displacement during the Holocene in southeastern Ångermanland, Sweden, has been investigated by means of radiocarbon-dating of isolation intervals in sediment cores from a total of nine new basins. Results from earlier investigations have been used in complement. There is a forced regression in the area from c. 9300 BP ( c . 10500 cal. yr BP) until c . 8000 BP ( c . 9000 cal. yr BP), on average c . 8 m/100 years, after which there is a gradually slowing regression of c . 2.5–1.0 m/100 years up to the present time. The most rapid regression occurs during the later phase of the Ancylus Lake stage, 9500–9000 cal. yr BP. There is no evidence of halts in the regression. Crustal uplift in the area since deglaciation is c . 310 m. The deglaciation of southeastern Ångermanland took place c . 9300 BP ( c . 10500 cal. yr BP); this is c . 900 years earlier than the age given by clay varve dating. The shore displacement curve provides a means of estimating the difference between the clay varve time scale and calibrated radiocarbon dates, by comparison with varve-dated altitudes of alluvial deltas of the River Ångermanalven. From c. 2500 to c. 8000 cal. BP there is a deficit in clay varves of some 300 years; further back in time this discrepancy increases significantly. The main explanation for the discrepancy is most likely lacking varves in the time-span 8500–10200 cal. yr BP, located along the upper reaches of River Ångermanalven below the highest shore level.  相似文献   

14.
In recent years, major advances have been made in our understanding of Late Quaternary sea-level changes in western Scotland. In particular, new hypotheses have been advanced to explain the ages and origins of high-level rock platform fragments and high-level marine shell beds. Certain raised shorelines in Islay and Jura, SW Argyll and Wester Ross have been related to former margins of the last ice sheet and are associated with drops in the Lateglacial marine limit. In some areas the decline in Lateglacial sea-level took place in association with a stationary ice margin while in others the fall in sea-level occurred in conjunction with considerable ice retreat.During the Lateglacial Interstadial, relative sea-level fell rapidly between ca. 13 and ca. 12 ka BP and thereafter more slowly until ca. 11 ka BP. Renewed marine erosion during the cold climate of the Loch Lomond (Younger Dryas) Stadial (ca. 11-10 ka BP) resulted in the production of the Main Lateglacial Shoreline, which declines in altitude to the W, SW and S away from the centre of glacio-isostatic uplift in the W Highlands. The shoreline has a maximum altitude of 10–11 m O.D. in the Oban area and passes below sea-level in NE Islay, Ardnamurchan, Colonsay, W Mull, Kintyre and Arran.During the early Holocene a pronounced marine transgression took place, probably culminating between 6.6 and 7.0 ka BP. The culmination of the transgression is represented by the Main Postglacial Shoreline that reaches a maximum altitude of ca. 14 m in the Oban area and declines gently in altitude away from the centre of glacio-isostatic uplift. Reconstruction of the uplift isobases for this shoreline appears to indicate a slight eastward migration of the uplift centre since the Younger Dryas. In peripheral areas of western Scotland the Main Postglacial Shoreline is not present owing to the effect of Holocene submergence.  相似文献   

15.
Late- and postglacial history of the Great Belt, Denmark   总被引：3，自引：0，他引：3  
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   

16.
Near-shore Baltic Ice Lake deposits in Fakse Bugt, southeast Denmark   总被引：1，自引：0，他引：1  
Shallow seismic, sedimentological and macrofossil data and AMS radiocarbon dates on terrestrial plant remains from submarine deposits in Fakse Bugt in the southwestern part of the Baltic Sea are presented. The sediments were deposited near the shore of the Baltic Ice Lake, mostly in barrier-lagoon environments, during two highstand episodes dated to around 12.5–12.2 14C ka BP and 10.6–10.3 ka BP. Coastal sediments from the highstands indicate maximum water levels of 13–15 m and 13 m below present sea level, respectively. During the first episode Salix polaris was widespread in the land area, and during the second episode Dryas octopetala and Betula nana were the most common woody plants. During the lowstand episode Betula pubescens woods dominated. The flora and fauna of the Baltic Ice Lake were rather diverse, reflecting the long and increasing distance to the margin of the Fennoscandian Ice Sheet. Calcium-carbonate-rich, mesotrophic water characterized the Baltic Ice Lake in Fakse Bugt.  相似文献   

17.
Deglaciation took place in eastern Jämtland and Ångermanland in central Sweden c . 10 500–10 200 cal. yr BP. In the present study, vegetation development and shore displacement during the earliest ice-free period are investigated by 14C dating of sediment from six isolated lake basins and by pollen analysis. A brief but distinct peak in Hippophaë occurs in all pollen diagrams coincident with basin isolation, followed by up to 500 years (varying locally) by an Alnus rise. The Alnus curve does not display a synchronous rise in the area. Its expansion below the highest shore level is time-transgressive and controlled mainly by the timing of basin isolation. The relationship between regional Alnus expansion and changes in hydrology and climate is discussed. The pollen diagrams show Pinus predominance with Corylus to the east (more coastal areas) and Betula predominance (though less pronounced) to the west during the period 10 200–9000 cal. yr BP. However, comparisons between sites suggest marked variability in the forest development. Shore displacement in easternmost Jämtland c . 10 300–9000 cal. yr BP is equal to or slightly more rapid than that of SE Ångermanland, contrary to the present pattern of isostatic recovery. A rapid shore level regression c . 10 300–10 000 cal. yr BP may be related to drainage of the Ancylus Lake.  相似文献   

18.
The extent of glaciation in northwestern Alaska, the source of sediment supply to the Chukchi shelf and slope, and the movement of sea ice and icebergs across the shelf during the last glacial maximum (LGM) remain poorly constrained. Here we present geophysical and geological data from the outer Chukchi margin that reveal a regionally extensive, heavily ice-scoured surface ∼ 5-8 m below the modern seafloor. Radiocarbon dating of this discrete event yields age estimates between 10,600 and 11,900 14C yr BP, indicating the discharge event occurred during the Younger Dryas. Based on mineralogy of the ice-rafted debris, the icebergs appear to be sourced from the northwestern Alaskan margin, which places important constraints on the ice extent in northern Alaska during the LGM as well as existing circulation models for the region.  相似文献   

19.
Blomvåg, on the western coast of Norway north of Bergen, is a classical site in Norwegian Quaternary science. Foreshore marine sediments, named the Blomvåg Beds and now dated to the Bølling‐Allerød from 14.8 to 13.3 cal. ka BP, contain the richest Lateglacial bone fauna in Norway, numerous mollusc shells, driftwood, and flint that some archaeologists consider as the oldest traces of humans in Norway. The main theme of this paper is that the Blomvåg Beds are overlain by a compact diamicton, named the Ulvøy Diamicton, which was interpreted previously as a basal till deposited during a glacial re‐advance into the ocean during the Older Dryas (c. 14 cal. ka BP). Sediment sections of the Blomvåg Beds and the Ulvøy Diamicton were exposed in ditches in a cemetery that was constructed in 1941–42 and have subsequently not been accessible. A number of radiocarbon and cosmogenic 10Be exposure ages demonstrate that the diamicton is not likely to be a till because minimum deglaciation ages (14.8–14.5 cal. ka BP) from the vicinity pre‐date the Ulvøy Diamicton. We now consider that sea ice and icebergs formed the Ulvøy Diamicton during the Younger Dryas. The Scandinavian Ice Sheet margin was located on the outermost coastal islands between at least c. 18.5 and 14.8 cal. ka BP; however, no ice‐marginal deposits have been found offshore from this long period. The Older Dryas ice margin in this area was located slightly inside the Younger Dryas margin, whereas farther south it was located slightly beyond the Younger Dryas margin.  相似文献   

20.
Postglacial land uplift patterns of south Sweden and the Baltic Sea region   总被引：1，自引：0，他引：1  
Comparison of the land uplift pattern for the last 10,300 years, shown by studies of raised shorelines of the Baltic Ice Lake, with the pattern of present-day land uplift of Fennoscandia, shows that significant regional changes of uplift pattern have taken place. Some of these changes seem to be related to a halt in ice retreat during the Younger Dryas cold stage. It is also probable that some observed anomalies in the present uplift are not of glacio-isostatic origin, but are possibly related to structures in the lower lithosphere and upper mantle or large scale tectonics.  相似文献   

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