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1.
The Late Quaternary ( c . 130,000–10,000 BP) glacial history of the central west coast of Jameson Land, East Greenland, is reconstructed through glacial stratigraphical studies. Seven major sedimentary units are described and defined. They represent two interglacial events (where one is the Holocene). one interstadial event and two glacial events. The older interglacial event comprises marine and fluvial sediments, and is correlated to the Langelandselv interglacial, corresponding to oxygen isotope sub-stage 5e. It is followed by an Early Weichselian major glaciation during the Aucellaelv stade, and subsequently by an Early Weichselian interstadial marine and deltaic event (the Hugin Sø interstade). Sediments relating to the Middle Weichselian have not been recognized in the area. The Hugin Sø interstade deposits have been overrun by a Late Weichselian ice advance, during the Flakkerhuk stade, when the glacier, which probably was a thin, low gradient fjord glacier in Scoresby Sund, draped older sediments and landforms with a thin till. Subsequent to the final deglaciation, some time before 10,000BP, the sea reached the marine limit around 70 m a.s.l., and early Holocene marine, fluvial and littoral sediments were deposited in the coastal areas.  相似文献   

2.
Coastal Jameson Land is characterized by thick Quaternary deposits from the last interglacial/glacial cycle. The successions at the mouth of Langelandselv exhibit a key stratigraphy where sediments from the Langelandselv interglaciation (Eemian) are overlain by three till units interbedded with glacimarine and deltaic interstadial successions. Immediately after the retreat of glaciers after the extensive Scoresby Sund glaciation (Saalian). advection of warm Atlantic surface water surpassed what is known from the Holocene. The two lowermost Weichselian tills, deposited during the Aucellaelv and Jyllandselv stades (Early Weichselian), reflect short-lasting readvances of fjord glaciers. Luminescence dates and correlation with adjacent areas suggest ages of 110–80 ka and 70–60 ka for the Hugin Sø and the Møselv interstades, respectively.  相似文献   

3.
The sedimentary record around outer Scorcsby Sund begins with the Scorcsby Sund glaciation (≅ isotope stage 6), but is incomplete. Both at Kap Hope, headward of the fjord mouth, and at Kikiakajik on the outer coast. there are shallow marine sediments, correlated with the Langelandselv interglaciation (≅ isotope substagc 5e) on the basis of molluse assemblages and luminescence dates. Abundant Balanus crenatus , and several bivalves. show that thc adveetion of warm Atlantic water to the East Greenland coast was higher during that interglacial than during the Holocenc. Glacial striae at Kap Brewster (facing the open ocean) and till on top of the interglacial beds at Kikiakajik show that both an outlet from the Greenland Iee Sheet, and more local glaciers reached the continental shelf during the Weichselian. This glacial event is poorly dated. but tentatively correlated with the Flakkerhuk stade (≅ 19 15 ka BP) when, from marine geological data, it is suggested that thc Scoresby Sund glacier terminated c . 30 km east of Kap Brewster. During the Milne Land stade ( c . 10 ka BP) there was a resurgence of local ice caps in the mountains both north and south of the fjord mouth, but Scoresby Sund and Hall Bredning probably remained free of glaciers. Dating of these events was achieved through Iuminescence- (TL and OSL) and the 14C-method. and biostratigraphical and amino acid correliition Interglacial shells on thc outer coast show much lower amino acid D/L ratios than shells of the same age within the Scoresby Sund area. This may indicate that the outer coast remained free of ice cover and marine inundation much longer, arid suffered colder temperatures than areas along the fjord.  相似文献   

4.
The bio- and chronostratigraphy of the Eemian interglacial (marine isotope substage 5e) and an Early Weichselian glaciation (5d-a) established from representative and detailed sequences can be correlated with the deep-sea oxygen isotope stratigraphy, ice-core data, sea-level fluctuations and coupled ice sheet-climate models. Biostratigraphic sequences from Fennoscandian key sections are correlated with reference sequences from Estonia and from sections located near or beyond the margins of the last glaciation. Organic sediments previously attributed to Early and Middle Weichselian interstadial periods in Finland are argued to be redeposited and mixed older (last interglacial) material. Pollen and diatom spectra of the undisturbed materials suggest that the Eemian climatic optimum was followed by a continuously cooling climate and a regressive marine level. If only undisturbed sequences are considered, the major climatic fluctuations of the Early Weichselian, apparent in Central and Western Europe, are not apparent in the sequences from the central part of the glaciated terrain. Instead, some sequences are truncated by sediments indicating approaching ice sheets soon after the interglacial. This may imply that the ice sheet grew over Finland during the first Early Weichselian stadial. The preservation of the interglacial beds and the lack of younger non-glacial sediments support the interpretation that the area remained ice-covered until the final deglaciation. During the Early Weichselian, the Norwegian coast was probably occasionally ice free, similar to the coastal zone of Greenland today. The authors' interpretation of the Fennoscandian organic deposits of the last glaciation may also explain similar observations from the central parts of the Laurentide ice sheet.  相似文献   

5.
Deposits of Late Pleistocene age were investigated near the Fynselv river on the southwestern coast of Jameson Land. East Greenland. The deposits are of fluvial, deltaic shallow marine and glacigenic origin. Four stratigraphic units are recorded. Unit I consists of deltaic and shallow marine deposits reflecting a relative sea level of at least 20 m above the present. Elevated fluvial deposits represent the subaerial part of the depositional system. The system existed during full interglacial and subarctic conditions as indicated by remains or flora and Fauna and unit I is correlated with the Langelandselv interglaciation (isotopic substage 5e). Unit II consists of a till deposited by a glacier in the Scoresby Sund Fjord during the beginning of the Early Weichselian referred to as the Aucellaelv stade. The glacier probably melted in a marine environment. Unit III represents a marine delta system during the Hugin Sø interstade. and reveals a relative sea level of at least 62 m above the present. Unit IV consists of till and kame deposits assumed to be deposited by a glacier in the Scoresby Sund Fjord during the Flakkerhuk stade. probably a Late Weichselian glacier advance.  相似文献   

6.
Marine, fluvial and glacigene sediments exposed in coastal cliffs and stream-cut sections in East Greenland between latitudes 69° and 78° N display a record of Quaternary climatic and environmental change going back to pre-Saalian times (> 240 ka), but with main emphasis on the last interglacial/glacial cycle. The stratigraphical scheme is based on studies on the Jameson Land peninsula, and contains five glacial stages and stades with the Greenland ice sheet or its outlets reaching the outer coasts. Individual sites are correlated and dated by a combination of biostratigraphy, luminescence dating, amino acid analyses, as well as 14C- and uranium series dating. The pre-Weichselian Lollandselv and Scoresby Sund glaciations were the most extensive. During the Weichselian the Inland Ice margin in this part of East Greenland was apparently very stable. The Aucellaelv, Jyllandselv and Flakkerhuk stades mark the advance and subsequent retreat of outlet glaciers from the Inland Ice which advanced through the wide Scoresby Sund basin and reached the inner shelf. In-between the glacier advances, three interglacial or interstadial periods have been recognized. During the Langelandselv interglacia-tion (≅ Eemian) the advection of warm Atlantic water was higher than during the Holocene, and the terrestrial flora and insect faunas show that summer temperatures were 3–4°C higher than during the Holocene optimum. There is no unambiguous evidence for cooling in the sediments from this interval. Later, in isotope stage 5, there were apparently two ice-free periods. During the Hugin Sø interstade, stable Polar water dominated Scoresby Sund, and the terrestrial flora suggests summer temperatures 2° -3° lower than the present. The marine and fluvial sediments from the second ice-free period, the Mønselv interstade, are devoid of organic remains.  相似文献   

7.
The first major Weichselian ice advance in Scoresby Sund, during the Aucellaelv stage, deposited thick till beds along the coast of Jameson Land between > 107 ka and 140 ka. and is correlated with isotope substage 5d in the marine record. This is shown by stream-cut sections at the mouth of the Aucellaelv. Jameson Land, which contain a scquence of shallow marine, fluvial and glacigene sediments extending from the Scoresby Sund glaciation (≅Saalian) to the Flakkerhuk stade (Late Weichselian). The sequence is dated by palaeoceanographic correlation with the deep-sea record, U/Th and luminescence dating, and correlated with the record in adjacent areas by mapping of marker horizons, and by mollusc fauna assemblages and amino acid analyses.  相似文献   

8.
Detailed investigations of sediments exposed along river sections in the coastal part of Jameson Land have revealed a Saalian to Holocene glacial history. Eleven sedimentary units have been distinguished. most of which are found in superposition at one single large section. Four subglacially formed till beds are recognized; three of which are of Weichselian age. All the tills are considered to have been deposited at the base of fjord glaciers restricted to the Scoresby Sund basin. The tills are separated by marine, fluvial or deltaic sediments, and demonstrate changes in the depositional environnient considered to represent changes in relative sea level during the ice-free periods. The fossil content. supported by a series of luminescence dates, suggest that most of the succession is of Eemian and Early Weichselian age. From the luminescence dates, a short duration of <10ka is suggested for the Early Weichselian glacial stades. Sedimentation during this period was partly controlled by glacio-isostatic subsidence caused by net growth of the Greenland Ice Sheet. The Middle Weichselian is represented by a large hiatus. whereas the Late Weichselian is represented by a subglacial till.  相似文献   

9.
The sedimentary record from the Ugleelv Valley on central Jameson Land, East Greenland, adds new information about terrestrial palaeoenvironments and glaciations to the glacial history of the Scoresby Sund fjord area. A western extension of a coastal ice cap on Liverpool Land reached eastern Jameson Land during the early Scoresby Sund glaciation (≈the Saalian). During the following glacial maximum the Greenland Ice Sheet inundated the Jameson Land plateau from the west. The Weichselian also starts with an early phase of glacial advance from the Liverpool Land ice cap, while polar desert and ice‐free conditions characterised the subsequent part of the Weichselian on the Jameson Land plateau. The two glaciation cycles show a repeated pattern of interaction between the Greenland Ice Sheet in the west and an ice cap on Liverpool Land in the east. Each cycle starts with extensive glacier growth in the coastal mountains followed by a decline of the coastal glaciation, a change to cold and arid climate and a late stage of maximum extent of the Greenland Ice Sheet. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

10.
Until recently, little was known about the Quaternary marine sedimentary record in East Greenland. Geophysical and geological investigations in Scoresby Sund were undertaken to characterize the nature and chronology of this record. Seismic records show that almost 70% of the outer fjord system is covered by about 10 m of unlithified sediments, making direct correlation with the Quaternary records on land and the adjacent continental margin difficult. These acoustically unstratified sediments are scoured by icebergs above 550 m water depth. Almost 90% of core material is massive diamicton of Holocene age, deposited mainly from iceberg rafting and turbid meltwater. Sedimentation rates are 0.1 -0.3 m 1000 yr-1. Thicker accumulations of unlithified Quaternary sediments in Scoresby Sund occur as sediment ridges and in two other major depocentres. A low sediment ridge runs across the mouth of Scoresby Sund, and is interpreted as an end moraine of Late Weichselian Flakkerhuk stadial age. The very restricted sediment thickness suggests that grounded ice filled the fjord during the Flakkerhuk and an ice shelf was not present. High inputs of ice rafted debris to the continental margin at about 18 000 BP indicate this as a probable age for the moraine. During the Allerød Interstadial, ice probably retreated from the outer fjord system, since massive diamictons similar to those of Holocene age are present at the base of most cores. A major depocentre of acoustically stratified sediments at the head of Hall Bredning is interpreted to represent ice proximal deposits from a glacier margin extending across the fjord. It is adjacent to dated moraines on land and is inferred to be of Milne Land stadial age (about 10 000 BP). A similar age is interpreted for acoustically laminated sediments and a moraine at the entrance of Vikingebugt, on the south side of Scoresby Sund. Dated kame terraces in the inner fjord system indicate that ice retreated to its present position 6–7000 years ago.  相似文献   

11.
Previous work has presented contrasting views of the last glaciation on Jameson Land, central East Greenland, and still there is debate about whether the area was: (i) ice-free, (ii) covered with a local non-erosive ice cap(s), or (iii) overridden by the Greenland Ice Sheet during the Last Glacial Maximum (LGM). Here, we use cosmogenic exposure ages from erratics to reconcile these contrasting views. A total of 43 erratics resting on weathered sandstone and on sediment-covered surfaces were sampled from four areas on interior Jameson Land; they give 10Be ages between 10.9 and 269.1 kyr. Eight erratics on weathered sandstone and till-covered surfaces cluster around ∼70 kyr, whereas 10Be ages from erratics on glaciofluvial landforms are substantially younger and range between 10.9 and 47.2 kyr. Deflation is thought to be an important process on the sediment-covered surfaces and the youngest exposure ages are suggested to result from exhumation. The older (>70 kyr) samples have discordant 26Al and 10Be data and are interpreted to have been deposited by the Greenland Ice Sheet several glacial cycles ago. The younger exposure ages (≤70 kyr) are interpreted to represent deposition by the ice sheet during the Late Saalian and by an advance from the local Liverpool Land ice cap in the Early Weichselian. The exposure ages younger than Saalian are explained by periods of shielding by non-erosive ice during the Weichselian glaciation. Our work supports previous studies in that the Saalian Ice Sheet advance was the last to deposit thick sediment sequences and western erratics on interior Jameson Land. However, instead of Jameson Land being ice-free throughout the Weichselian, we document that local ice with limited erosion potential covered and shielded large areas for substantial periods of the last glacial cycle.  相似文献   

12.
Alexanderson, H., Landvik, J. Y. & Ryen, H. T. 2010: Chronology and styles of glaciation in an inter‐fjord setting, northwestern Svalbard. Boreas, 10.1111/j.1502‐3885.2010.00175.x. ISSN 0300‐9483. A 30‐m‐thick sedimentary succession at Leinstranda on the southwestern coast of Brøggerhalvøya, northwestern Svalbard, spans the two last glacial–interglacial cycles and reveals information on glacial dynamics, sea‐level changes and the timing of these events. We investigated the deposits using standard stratigraphical and sedimentological techniques, together with ground‐penetrating radar, and established an absolute chronology based mainly on optically stimulated luminescence dating. We identified facies associations that represent depositional settings related to advancing, overriding and retreating glaciers, marine and littoral conditions and periglacial surfaces. The environmental changes show an approximate cyclicity and reflect glaciations followed by high sea levels and later regression. The luminescence chronology places sea‐level highstands at 185 ± 8 ka, 129 ± 10 ka, 99 ± 8 ka and 36 ± 3 ka. These ages constrain the timing of recorded glaciations at Leinstranda to prior to c. 190 ka, between c. 170 and c. 140 ka (Late Saalian) and between c. 120 ka and c. 110 ka (Early Weichselian). The glaciations include phases with glaciers from three different source areas. There is no positive evidence for either Middle or Late Weichselian glaciations covering the site, but there are hiatuses at those stratigraphic levels. A high bedrock ridge separates Leinstranda from the palaeo‐ice stream in Kongsfjorden, and the deposits at Leinstranda reflect ice‐dynamic conditions related to ice‐sheet evolution in an inter‐fjord area. The environmental information and the absolute chronology derived from our data allow for an improved correlation with the marine record, and for inferences to be made about the interaction between land, ocean and ice during the last glacial–interglacial cycles.  相似文献   

13.
Four geologic units previously mapped in southern Jameson Land. East Greenland (Funder 1978, 1990) are identifiable on a false colour composite of Landsat Thematic Mapper (TM) spectral hands TM5. TM4 and TM1. The area covered by the Weichselian glaciations has a fresh glacial morphology and a less developed drainage system than the older landscape. The Weichselian glaciers reached more than 200 m a.s.l. in the west. but only about 100 m a.s.l. in the east. A contextual analysis (local frequency and local orientation) was included in a Maximum Likelihood classification (M-L) to map the extent of the Weichselian glaciations. Deposits correlated with the Saalian Scoreshy Sund glaciation are found on the central plateaux of Jameson Land. Landsat TM geological mapping of the surficial distribution of deposits from the Scoreshy Sund glaciation and of weathered Jurassic sandstone or deposits with a high percentage of such sandstone was done using a supervised Maximum Likelihood procedure. Except for the mapping of thc extent of the Late Weichselian Flakkerhuk glaciation, the Maximum Likelihood boundaries between units are in general agrecnient with earlier mapping or with the visual interpretation of the false colour composite. A strong vegetational influence. and similar spectral reflectance lrom deposits of different age due to similarities in lithological composition reduced the possibility of an independent remote sensing approach. Taking already existing general geological knowledge and chronology into account allowed successful Landsat TM geological mapping.  相似文献   

14.
At Kap Herschell, in the outer fjord zone of central northeast Greenland, exposed sections in a Late Pleistocene ice-cored moraine revealed four major stratigraphic units deposited during the complex Kap Herschell Stade . All contain fragmented and redeposited marine shells that most likely belong to an Eemian or Early Weichselian marine episode. The oldest unit consists of buried ground ice with folded and sheared debris bands. Isotopic analyses show that the slope of the regression line for δ2H vs. δ18O of the ice is about 8.5. which suggests correlation with the Global Meteoric Water Line (GMWL). Data strongly suggest that the ground ice at Kap Herschell is a remnant of a Late Pleistocene glacier. It was probably generated at low altitudes (< 1000 m) in the inner fjord region or in the nunatak zone. The ground ice is unconformably overlain by all younger stratigraphic units, the oldest of which is a diamicton probably deposited as ablation till from the ice. A complex unit composed of mainly glaciolacustrine deposits and subordinate beds of fluvial and deltaic origin overlies the till and ground ice. Luminescence dating of the lacustrine sediments indicates maximum ages younger than 43 ka BP, suggesting deposition during isotope stages 3 or 2. The glaciolacustrine deposits suffered strongly from glaciotectonic deformation, caused by renewed glacier advance through the fjord. It reached the inner shelf and led to deposition of a discordant till at Kap Herschell, most probably during the Late Weichselian.  相似文献   

15.
Late Weichselian glacier limits for the Forlandsundet area, western Spitsbergen are reconstructed from the stratigraphic distribution of tills and deglacial deposits, variations in the altitude of the marine limit, distribution of pre-Late Weichselian raised beach deposits, and the rare occurrence of moraines and striated bedrock. The Late Weichselian glaciation was primarily a local event with fjord outlet-glaciers expanding no more than 15 km beyond their present position; cirque glaciers were similar to their neoglacial limits. A previously reconstructed ice sheet centered over the Barents Shelf had little direct influence on the glaciation of the Forlandsundet area. Glacier retreat began at or prior to 10.5 ka ago and possibly as early as 13 ka ago with fjords mostly, and perhaps rapidly deglaciated by 10 to 9 ka ago.  相似文献   

16.
A complete interglacial cycle, named the Fjøsangerian and correlated with the Eemian by means of its pollen stratigraphy, is found in marine sediments just above the present day sea level outside Bergen, western Norway. At the base of the section there are two basal tills of assumed Saalian ( sensu lato ) age in which the mineralogy and geochemistry indicate local provenance. Above occur beds of marine silt, sand and gravel, deposited at water depths of between 10 and 50 m. The terrestrial pollen and the marine foraminifera and molluscs indicate a cold-warm-cold sequence with parallel development of the atmospheric and sea surface temperatures. In both environments the flora/fauna indicate an interglacial climatic optimum at least as warm as that during the Holocene. The high relative sea level during the Eemian (at least 30 m above sea level) requires younger neotectonic uplift. The uppermost marine beds are partly glaciomarine silts, as indicated by their mineralogy, drop stones and fauna, and partly interstadial gravels. The pollen indicates an open vegetation throughout these upper beds, and the correlation of the described interstadial with Early Weichselian interstadials elsewhere is essentially unknown. The section is capped by an Early Weichselian basal till containing redeposited fossils, sediments, and weathering products. Several clastic dikes injected from the glacier sole penetrate the till and the interglacial sediments. Radiocarbon dates on wood and shells gave infinite ages. Amino acid epimerization ratios in molluscs support the inferred Eemian age of the deposit. The Fjøsangerian is correlated with the Eemian and deep sea oxygen isotope stage 5e; other possible correlations are also discussed.  相似文献   

17.
The deglaciation history and Holocene environmental evolution of northern Wijdefjorden, Svalbard, are reconstructed using sediment cores and acoustic data (multibeam swath bathymetry and sub-bottom profiler data). Results reveal that the fjord mouth was deglaciated prior to 14.5±0.3 cal. ka BP and deglaciation occurred stepwise. Biomarker analyses show rapid variations in water temperature and sea ice cover during the deglaciation, and cold conditions during the Younger Dryas, followed by minimum sea ice cover throughout the Early Holocene, until c. 7 cal. ka BP. Most of the glaciers in Wijdefjorden had retreated onto land by c. 7.6±0.2 cal. ka BP. Subsequently, the sea-ice extent increased and remained high throughout the last part of the Holocene. We interpret a high Late Holocene sediment accumulation rate in the northernmost core to reflect increased sediment flux to the site from the outlet of the adjacent lake Femmilsjøen, related to glacier growth in the Femmilsjøen catchment area. Furthermore, increased sea ice cover, lower water temperatures and the re-occurrence of ice-rafted debris indicate increased local glacier activity and overall cooler conditions in Wijdefjorden after c. 0.5 cal. ka BP. We summarize our findings in a conceptual model for the depositional environment in northern Wijdefjorden from the Late Weichselian until present.  相似文献   

18.
Coastal cliffs and stream cut sections at Langelandselv on Jameson Land show a 22 m thick sedimentary succession reflecting the development of shallow marine and fluvial environments during the last interglaciation. The shallow marine sediments were deposited in upper shoreface, back-barrier, and delta environments during a rise in the relative sea level from 0 to 18 m. The interglacial succession ends with glaciotectonically dislocated fluvial sand, and is capped by alternating beds of lodgement till and fluvial sand, deposited during the Early Weichselian. The age is determined by palacoceanographic correlation of molluse and foraminifer faunas with isotopic substage 5e in the deep sea record, supported by luminescencs and U/Th dates and amino acid analysis.  相似文献   

19.
Little is known concerning climate changes in the Eastern Baltic region during the last interglacial–glacial cycle and in particular, climate changes during the Weichselian. In this study, a quantitative reconstruction of the mean January and July temperature for the Medininkai-117 site in Lithuania is presented. The reconstruction is based on pollen and plant macrofossils from this site, which reveal that the vegetation was characteristic of many northern Europe sites during the Eemian and Early Weichselian. Gradual evolution of the vegetation suggests that relatively uniform climate conditions existed during the Eemian. Our reconstructions support the view of a relatively stable Eemian, with short cooling phases of low amplitude. A strong increase in temperature was apparent during the beginning of the interglacial and decrease during the transition to the Weichselian. Reconstructed July temperatures of the Eemian interglacial were approximately 2 °C higher than today (18.5 °C; today: 16.2 °C) and were similar to today for January (− 5.2 °C; today: − 5.1 °C). July temperatures during the Early Weichselian were only ~ 2°C lower than during the Eemian, whereas the January temperatures gradually decreased. Winter temperatures were relatively high (above − 10 °C) during the Early Weichselian.  相似文献   

20.
A coastal cliff facing the ocean at the west coast of Spitsbergen has been studied, and seven formations of Weichselian and Holocene age have been identified. A reconstruction of the palaeoenvironment and glacial history shows that most of the sediments cover isotope stage 5. From the base of the section, the formation 1 and 2 tills show a regional glaciation that reached the continental shelf shortly after the Eemian. Formation 3 consists of glacimarine to marine sediments dated to 105,000–90,000 BP. Amino acid diagenesis indicates that they were deposited during a c . 10,000-year period of continuous isostatic depression, which indicates contemporaneous glacial loading in the Barents Sea. Foraminifera and molluscs show influx of Atlantic water masses along the west coast of Svalbard at the same time. Local glaciers advanced during the latter part of this period, probably due to the penetration of moist air masses, and deposited formation 4. A widespread weathering horizon shows that the glacial retreat was succeeded by subaerial conditions during the Middle Weichselian. Formation 5 is a till deposited during the Late Weichselian glacial maximum in this area. The glaciation was dominated by ice streams from a dome over southern Spitsbergen, and the last deglaciation of the outer coast is dated to 13,000 BP. A correlation of the events with other areas on Svalbard is discussed, and at least two periods of glaciation in the Barents Sea during the Weichselian are suggested.  相似文献   

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