Kubischta, F., Knudsen, K.L., Ojala, A.E.K. and Salonen, V.-P., 2011. Holocene benthic foraminiferal record from a high-arctic fjord, Nordaustlandet, Svalbard. Geografiska Annaler: Series A, Physical ...Geography, 93, 227-242. DOI: 10.1111/j.1468-0459.2011.00434.x
This study presents the results of benthic foraminiferal analyses of a marine core record from about 100 m water depth in the fjord environment of Isvika bay, Nordaustlandet, Svalbard. During the Last Glacial Maximum, the bay was glaciated by the north-western sector of the Svalbard-Barents Sea Ice Sheet. The foraminiferal assemblages reflect glaciomarine conditions during deglaciation and early Holocene (about 11-250-9640 cal. yr bp) followed by glacier-distal environment in an open fjord with relatively high influence of Atlantic waters from the open ocean (9640-7430-cal. yr bp). A subsequent foraminiferal indication of a glacial advance was followed by deposition of a diamicton unit within a short time period at 5800-5700 cal. yr bp. The mid- and late Holocene were characterized by assemblages indicating restricted open-ocean connection and gradually more severe conditions, which are considered to be caused partly by a gradual cooling and freshening of the Atlantic water inflow to the shelf area and partly by a continuous isostatic uplift of the area. The foraminiferal record shows that the environmental changes in Murchisonfjorden are not just an effect of changes in solar insolation but are also influenced by local processes, as well as changes in the Atlantic water inflow to the northern Svalbard shelf and to the fjord via Hinlopenstretet.
Benthic foraminiferal assemblages from Nordaustlandet, Svalbard, are described for the first time with the objective of reconstructing the palaeoenvironmental conditions in the area during the late ...Quaternary. Investigations were carried out on marine deposits exposed along the southern shores of Murchisonfjorden. Five foraminiferal assemblages (A1–A5), representing different palaeoenvironmental conditions, were identified from the marine intervals, i.e., the Cassidulina reniforme–Elphidium albiumbilicatum assemblage (A1) from the Early Weichselian, the Islandiella helenae–Cibicides lobatulus assemblage (A2) from the Early Weichselian, the Cibicides lobatulus–Cassidulina reniforme assemblage (A3) from marine isotope stage 3, the Elphidium albiumbilicatum assemblage (A4) from the early Holocene and the Astrononion gallowayi assemblage (A5) from the mid‐Holocene. Assemblages A1–A5 are compared with modern and fossil Quaternary assemblages from Arctic regions. Particularly notable is the fact that a well‐defined Middle Weichselian assemblage in Svalbard is described for the first time, i.e., the Cibicides lobatulus–Cassidulina reniforme assemblage. All the assemblages from Nordaustlandet represent glacier‐distal, inner‐shelf environments with an open connection to the ocean. The results reveal the occurrence of three marine intervals (ice‐free periods) in the north‐western part of Nordaustlandet during the Weichselian, as well as ice‐free conditions during most of the Holocene. A comparison of the assemblages from Nordaustlandet with previously published foraminiferal zones from onshore sections elsewhere in Svalbard show some degree of similarity, but also show considerable variation in species compositions, presumably caused by local environmental differences.
Compared to the other islands in the Svalbard archipelago, Nordaustlandet offers only limited stratigraphical or sedimentological information on its Quaternary deposits. This article aims to fill the ...gap by presenting new results from glacial geological, sedimentological and chronological studies in the southern Murchisonfjorden area. Field data include reconnaissance mapping and detailed logging of vertical sections along cliff‐face outcrops a few metres high adjacent to the present‐day shoreline. Combined with OSL and AMS age determinations, these data provide evidence of three successive Weichselian sequences, each represented by the deposition of till followed by the accumulation of shallow marine deposits. Contrary to earlier conclusions, this study demonstrates that the area was occupied by a Late Weichselian glacier (LWG), although the LWG till is thin and discontinuous. Interstadial sublittoral sand related to the Mid‐Weichselian interstadial was dated to 38–40 kyr, and an Early Weichselian interstadial to 76–80 kyr. The preservation of older sediments, multiple striae generations and abundant observations of weathered local bedrock material indicate weak glacial erosion within the study area. We suggest that the Late Weichselian glacier was relatively inactive and remained mainly cold‐based until the deglaciation. The Isvika sections can be considered a new key site that offers further potential to improve our understanding of the Weichselian stage within the northwestern sector of the Barents–Kara Ice Sheet.
Kubischta, F., Knudsen, K.L., Ojala, A.E.K. and Salonen, V.-P., 2011. Holocene benthic foraminiferal record from a high-arctic fjord, Nordaustlandet, Svalbard. Geografiska Annaler: Series A, Physical ...Geography, 93, 227-242. DOI: 10.1111/j.1468-0459.2011.00434.x This study presents the results of benthic foraminiferal analyses of a marine core record from about 100m water depth in the fjord environment of Isvika bay, Nordaustlandet, Svalbard. During the Last Glacial Maximum, the bay was glaciated by the north-western sector of the Svalbard-Barents Sea Ice Sheet. The foraminiferal assemblages reflect glaciomarine conditions during deglaciation and early Holocene (about 11250-9640 cal. yr bp) followed by glacier-distal environment in an open fjord with relatively high influence of Atlantic waters from the open ocean (9640-7430cal. yr bp). A subsequent foraminiferal indication of a glacial advance was followed by deposition of a diamicton unit within a short time period at 5800-5700 cal. yr bp. The mid- and late Holocene were characterized by assemblages indicating restricted open-ocean connection and gradually more severe conditions, which are considered to be caused partly by a gradual cooling and freshening of the Atlantic water inflow to the shelf area and partly by a continuous isostatic uplift of the area. The foraminiferal record shows that the environmental changes in Murchisonfjorden are not just an effect of changes in solar insolation but are also influenced by local processes, as well as changes in the Atlantic water inflow to the northern Svalbard shelf and to the fjord via Hinlopenstretet.
Benthic foraminiferal assemblages from Nordaustlandet, Svalbard, are described for the first time with the objective of reconstructing the palaeoenvironmental conditions in the area during the late ...Quaternary. Investigations were carried out on marine deposits exposed along the southern shores of Murchisonfjorden. Five foraminiferal assemblages (A1-A5), representing different palaeoenvironmental conditions, were identified from the marine intervals, i.e., the Cassidulina reniforme-Elphidium albiumbilicatum assemblage (A1) from the Early Weichselian, the Islandiella helenae-Cibicides lobatulus assemblage (A2) from the Early Weichselian, the Cibicides lobatulus-Cassidulina reniforme assemblage (A3) from marine isotope stage 3, the Elphidium albiumbilicatum assemblage (A4) from the early Holocene and the Astrononion gallowayi assemblage (A5) from the mid-Holocene. Assemblages A1-A5 are compared with modern and fossil Quaternary assemblages from Arctic regions. Particularly notable is the fact that a well-defined Middle Weichselian assemblage in Svalbard is described for the first time, i.e., the Cibicides lobatulus- Cassidulina reniforme assemblage. All the assemblages from Nordaustlandet represent glacier-distal, inner-shelf environments with an open connection to the ocean. The results reveal the occurrence of three marine intervals (ice-free periods) in the north-western part of Nordaustlandet during the Weichselian, as well as ice-free conditions during most of the Holocene. A comparison of the assemblages from Nordaustlandet with previously published foraminiferal zones from onshore sections elsewhere in Svalbard show some degree of similarity, but also show considerable variation in species compositions, presumably caused by local environmental differences.
Abstract
A2.5−metrelong marine core from Isvika bay inNordaustlandet (80°N, 18°E) was AMS
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C dated and analysed for its sedimentological and magnetic parameters. The studied record was found to ...cover the entire Holocene and indicates major turnovers in the palaeo− hydrography and sedimentary depositional history. The area was deglaciated at around 11,300 BP. The earlyHolocene has indications of rapidmelting of glaciers and frequent deposition of ice−rafted debris (IRD). The climatic optimum terminated with a probable glacier re−advance event occurring ca. 5800 cal BP. This event caused the deposition of a diamicton unit in Isvika bay, followed by a shift towards a colder and amore stratified hydrographic set− ting. The reduction in IRD indicates gradual cooling, which led to the stratification of the bay and eventually to more persistent fast sea−ice conditions by 2500 cal BP. For the last 500 years, Isvika has again been seasonally open.
Luoto, T.P., Nevalainen, L., Kubischta, F., Kultti, S., Knudsen, K.L. and Salonen, V.-P., 2011: Late Quaternary ecological turnover in high arctic Lake Einstaken, Nordaustlandet, Svalbard (80° N). ...Geografiska Annaler: Series A, Physical Geography, 93, 337-354. DOI:10.1111/j.1468-0459.2011.00435.x
Multiproxy palaeolimnological analyses of a sediment core record from Lake Einstaken, Nordaustlandet, give insight into long-term ecological and environmental dynamics in the High Arctic Svalbard during the last c. 13-000 cal yr bp. Fossil remains of foraminifera, chironomidae, cladocera and diatoms (Bacillariophyta) revealed several distinct ecological turnovers during the late Quaternary. The foraminiferal assemblages in a marine interval in the lower part of the core indicated one distinct faunal turnover and two subsequent minor changes. The foraminiferal assemblages reflected high-arctic, shallow-water conditions in an area of changing salinity conditions. A development of gradually more restricted marine conditions, presumably related to a decrease in water depth during the isostatic uplift, was evident from the foraminiferal assemblages. The Holocene was characterized by a freshwater environment in the isolated Lake Einstaken. The cladoceran assemblages experienced two complete faunal turnovers in the early part of the lacustrine sediment sequence, most likely related to inlake processes. The chironomid assemblages went through five distinct Holocene faunal changes that were probably mostly related to climate development and changes in nutrient conditions. The freshwater diatoms revealed four distinct episodes of change in their assemblages that could be related to their sensitivity to pH and nutrient status. The most distinct common feature in the Holocene faunal and floral assemblages was the pioneer phase during the early Holocene. The recent environmental changes, which were most visibly reflected in the chironomid records, are possibly related to a coupled effect of elevated nutrient conditions and increased temperatures.
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