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Johanna Anjar Lena Adrielsson Nicolaj Krog Larsen Per Möller Kilian Barth 《Boreas: An International Journal of Quaternary Research》2014,43(3):608-626
This study presents the Weichselian stratigraphy on Kriegers Flak in the southwestern Baltic Sea, and correlates it to new sections in southernmost Sweden and to previously published stratigraphic sequences from SW Skåne. A total of four Weichselian advances are identified based on our correlations. The oldest till, observed only on Kriegers Flak, is dated to the Early or Middle Weichselian and tentatively correlated to the Ristinge advance, previously identified in Denmark. It is overlain by three interstadial sediment units, starting with brackish clay and followed by terrestrial and lacustrine deposits, which have been dated to 42–36 ka, and finally by glaciolacustrine clay dated to 28.5–26 ka. After 30 ka, the Fennoscandian ice sheet advanced through the Baltic Basin and into the coastal areas of southernmost Sweden where the Allarp Till was deposited, followed by a deglaciation sequence. The uppermost tills, the Dalby Till and the Lund till, were deposited during the LGM advance and the subsequent re‐advances through the Baltic Basin. Based on the new evidence it has been possible to identify and date a Middle and Late Weichselian till succession in southern Sweden and provide a strong correlation to the established glacial stratigraphies in Sweden and Denmark. 相似文献
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Per Möller Johanna Anjar Andrew S. Murray 《Boreas: An International Journal of Quaternary Research》2013,42(1):25-42
In central and northern Sweden, glacial sediments and landforms, formed during Early and Middle Weichselian stadials and their transition into interstadials, are often preserved in spite of having been overridden by later glacial advances. This study presents an OSL‐dated glacial stratigraphy from Idre in west‐central Sweden, expanding the area in which Middle Weichselian ice‐free conditions have been identified. Three sedimentary units were identified, with the lowermost unit consisting of glaciolacustrine sand, deposited in a stagnant water‐body. Nine OSL samples gave ages ranging from 54 to 41 ka, suggesting deposition during a deglacial phase in MIS 3. Normal faults and silt veins, formed after deposition, indicate that the area was ice‐free for a prolonged period, enabling the melting of buried stagnant ice. Above an erosional unconformity is a sediment unit characterized by gravels and sands deposited in a proximal braided‐river environment. OSL ages range from 180 to 41 ka, indicating poor sediment bleaching during deposition. We thus consider them to give a maximum age of the sedimentation, indicating deposition at or after 41 ka. The uppermost unit consists of a stacked succession of subglacial traction tills and glaciotectonite beds, representing the Late Weichselian glaciation of the area, probably during the inception phase with a wet‐based glacier regime. At the last deglaciation of the area there was extensive meltwater erosion, eroding all sedimentary units and forming a landscape with terraces and channels, and erosional remnants of the uppermost diamict as free‐standing hummocks. 相似文献
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A. N. Bear-Crozier Nugraha Kartadinata Anjar Heriwaseso Ole Nielsen 《Natural Hazards》2012,64(1):821-838
Volcanic ash is the most widespread of all volcanic hazards and has the potential to affect hundreds of thousands, or even millions, of people in the densely populated islands of Indonesia. There is limited information available for this region on the hazard posed by volcanic ash, particularly from volcanoes that have not erupted in recent times. There is a need for computational models capable of accurately predicting volcanic ash dispersal at ground level when coupled with field observations of historical or ongoing eruptive activity. To maximise the effectiveness of such models, they should be readily accessible, easy to use and well tested. Geoscience Australia in collaboration with the Australia-Indonesia Facility for Disaster Reduction and the Indonesian Centre for Volcanology and Geohazard Mitigation has collaboratively adapted an existing open-source volcanic ash dispersion model for use in Indonesia. The core model is the widely used, open-source volcanic ash dispersion model FALL3D. A Python wrapper (name here python-FALL3D) has been developed, which modifies the modelling procedure of FALL3D in order to simplify its use for those with little or no background in computational modelling. The modified procedure does not alter the core functionality of FALL3D, but simplifies the modelling procedure by streamlining the installation process, automating both the pre-processing of input meteorological datasets and configuring and executing each utility program in a single-step process. An application example was presented using python-FALL3D for an active volcano in West Java, Indonesia. The example showed that communities located on the western side of Gunung Gede are always susceptible to volcanic ash ground loading regardless of the seasonal variations in wind conditions, whereas communities on the eastern side of Gunung Gede have a marked increase in susceptibility to ground loading during rainy season conditions when prevailing winds include a strong easterly component. 相似文献
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Astrid Lyså Eiliv A. Larsen Johanna Anjar Naki Akçar Morgan Ganerød Asbjørn Hiksdal Roelant Van Der Lelij Christof Vockenhuber 《Boreas: An International Journal of Quaternary Research》2021,50(1):6-28
The volcanic island of Jan Mayen, remotely located in the Norwegian-Greenland Sea, was covered by a contiguous ice cap during the Late Weichselian. Until now, it has been disputed whether parts of the island south of the presently glaciated Mount Beerenberg area were ever glaciated. Based on extensive field mapping we demonstrate that an ice cap covered all land areas and likely also extended onto the shallow shelf areas southeast and east of the island. Chronological interpretations are based on K-Ar and 40Ar/39Ar dating of volcanic rocks, cosmogenic nuclide (36Cl) surface exposure dating of bedrock and glacial erratics, and radiocarbon dating. We argue that ice growth started after 34 ka and that an initial deglaciation started some 21.5–19.5 ka in the southern and middle parts of the island. In the northern parts, closer to the present glaciers, the deglaciation might have started later, as evidenced by the establishment of vegetation 17–16 cal. ka BP. During full glaciation, the ice cap was likely thickest over the southern part of the island. This may explain a seemingly delayed deglaciation compared with the northern parts despite earlier initial deglaciation. In a broader context, the new knowledge of the Late Weichselian of the island contributes to the understanding of glaciations surrounding the North Atlantic and its climate history. 相似文献
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Johanna Anjar Nicolaj K. Larsen Lena Håkansson Per Möller Henriette Linge Derek Fabel Sheng Xu 《Boreas: An International Journal of Quaternary Research》2014,43(1):132-148
We present 23 cosmogenic surface exposure ages from 10 localities in southern Sweden. The new 10Be ages allow a direct correlation between the east and west coasts of southern Sweden, based on the same dating technique, and provide new information about the deglaciation of the Fennoscandian Ice Sheet in the circum‐Baltic area. In western Skåne, southernmost Sweden, a single cosmogenic surface exposure sample gave an age of 16.8±1.0 ka, whereas two samples from the central part of Skåne gave ages of 17.0±0.9 and 14.1±0.8 ka. Further northeast, in southern Småland, two localities gave ages ranging from 15.2±0.8 to 16.9±0.9 ka (n=5) indicating a somewhat earlier deglaciation of the area than has previously been suggested. Our third locality, in S Småland, gave ages ranging from 10.2±0.5 to 18.4±1.6 ka (n=3), which are probably not representative of the timing of deglaciation. In central Småland one locality was dated to 14.5±0.8 ka (n=3), whereas our northernmost locality, situated in northern Småland, was dated to 13.8±0.8 ka (n=3). Samples from the island of Gotland suggest deglaciation before 13 ka ago. We combined the new 10Be ages with previously published deglaciation ages to constrain the deglaciation chronology of southern Sweden. The combined deglaciation chronology suggests a rather steady deglaciation in southern Sweden starting at c. 17.9 cal. ka BP in NW Skåne and reaching northern Småland, ～200 km further north, c. 13.8 ka ago. Overall the new deglaciation ages agree reasonably well with existing deglaciation chronologies, but suggest a somewhat earlier deglaciation in Småland. 相似文献
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