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- Anjar, Johanna, et al.
(författare)
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MIS 3 marine and lacustrine sediments at Kriegers Flak, southwestern Baltic Sea
- 2010
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Ingår i: Boreas. - : Wiley. - 1502-3885 .- 0300-9483. ; 39:2, s. 360-366
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Tidskriftsartikel (refereegranskat)abstract
- Sediment cores from the Kriegers Flak area in the southwestern Baltic Sea show a distinct lithological succession, starting with a lower diamict that is overlain by a c. 10 m thick clay unit that contains peat, gyttja and other organic remains. On top follows an upper diamict that is inter-layered with sorted sediments and overlain by an upward-coarsening sequence with molluscs. In this paper we focus on the clay unit, which has been subdivided into three subunits: (A) lower clay with benthic foraminifera and with diamict beds in the lower part; (B) thin beds of gyttja and peat, which have been radiocarbon-dated to 31-35 14C kyr BP (c. 36-41 cal. kyr BP); and (C) upper clay unit. Based on the preliminary results we suggest the following depositional model: fine-grained sediments interbedded with diamict in the lower part (subunit A) were deposited in a brackish basin during a retreat of the Scandinavian Ice Sheet, probably during the Middle Weichselian. Around 40 kyr BP the area turned into a wetland with small ponds (subunit B). A transgression, possibly caused by the damming of the Baltic Basin during the Kattegat advance at 29 kyr BP, led to the deposition of massive clay (subunit C). The data presented here provide new information about the paleoenvironmental changes occurring in the Baltic Basin following the Middle Weichselian glaciation.
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| 3. |
- Anjar, Johanna, et al.
(författare)
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OSL dating of Weichselian ice-free periods at Skorgenes, western Norway
- 2018
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Ingår i: Norwegian Journal of Geology. - : Geological Society of Norway. - 2387-5852 .- 2387-5844. ; 98:3, s. 301-313
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Tidskriftsartikel (refereegranskat)abstract
- During recent years, many sites with sediments pre-dating the Last Glacial Maximum have been identified in formerly glaciated areas. As more and better dates are presented from these sites, the dynamic behaviour of the Scandinavian Ice Sheet is becoming increasingly clear. In this study, we revisited the site Skorgenes in western Norway. Here, sediments from two ice-free periods are found below and interbedded with glacial diamicts. We present an updated chronology for the site, based on ten new Optically Stimulated Luminescence (OSL) dates, and discuss possible correlations. The samples had poor OSL properties but still provide a substantial improvement of the existing chronology. The oldest sediments identified at Skorgenes were deposited in a proglacial subaqueous setting at some point between 21 and 42 ka. This period was followed by a glacial advance and, during the subsequent ice retreat, a delta or subaqueous fan formed at Skorgenes. OSL ages from the foreset beds indicate deposition at some point between 17 and 30 ka, implying that the ice-front retreated east of Skorgenes at least once during the Late Weichselian. A substantial ice advance followed this retreat. The youngest sediments, forming a proglacial delta succession, were deposited during the final deglaciation of the site.
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| 5. |
- Anjar, Johanna, et al.
(författare)
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Palaeoenvironments in the southern Baltic Sea Basin during Marine Isotope Stage 3 : a multi-proxy reconstruction
- 2012
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 34, s. 81-92
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Tidskriftsartikel (refereegranskat)abstract
- Sediment cores from Kriegers Flak in the southwestern Baltic Sea provide a unique possibility to study the Middle Weichselian history of the Baltic Basin. Three Weichselian interstadial units have been identified and are attributed to Marine Isotope Stage 3 (MIS 3, 60-25 ka). The oldest unit A is characterized by a deglaciation sequence, gradually turning into brackish-water clay. The low-diversity benthic foraminiferal fauna, stable oxygen isotope values and Mg/Ca ratios indicate low temperature and salinity for unit A. A hiatus separates unit A from the overlying unit B, which was deposited in wetlands and shallow lakes between 42 and 36 cal. ka BP. Macrofossil and pollen analyses indicate deposition of unit B in an area dominated by a tree-less open tundra environment, possibly with some birch and pine in sheltered positions. The uppermost unit C is characterized by clay deposition, including redeposition of material from older sediments (unit B). Optically stimulated luminescence (OSL) ages indicate deposition of unit C between 26 and 28.5 ka. Radiocarbon ages of 39 and 40 cal. ka BP for unit C are considered to be too old. The following depositional model is suggested: (I) Isostatic depression of the region after an advance of the Scandinavian Ice Sheet (SIS), most likely the Ristinge ice advance, previously dated to c. 55-50 ka, enabled an inflow of marine waters into the Baltic Basin during the deposition of unit A. (II) Isostatic rebound caused a regression at Kriegers Flak, and a hiatus between units A and B. (III) Wetlands and smaller lakes formed in the uplifted area between 42 and 36 cal. ka BP (unit B). (IV) Deposition of glaciolacustrine clays at Kriegers Flak demonstrates that a growing SIS dammed Kattegat and the Baltic Basin c. 28.5 to 26 ka. The new evidence from Kriegers Flak provides a solid framework for future MIS 3 palaeoenvironmental reconstructions in the circum-Baltic area.
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| 6. |
- Anjar, Johanna
(författare)
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The Weichselian in southern Sweden and southwestern Baltic Sea : glacial stratigraphy, palaeoenvironments and deglaciation chronology
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis the Weichselian glaciation history of southernmost Sweden and the southwestern Baltic Basin is discussed, with special emphasis on Middle and Late Weichselian ice advances and subsequent deglaciations. The main study area was Kriegers Flak in the southwestern Baltic Sea where pre-Late Weichselian sediments were identified. We suggest that the lowermost till on Kriegers Flak, dated to the Early or Middle Weichselian, was deposited during the Ristinge advance, which implies an age of c. 55-50 ka. Following the deglaciation after this advance, isostatic depression enabled a marine influence in the southern Baltic Basin. During this time Kriegers Flak unit A, with a low-diversity benthic foraminifera fauna indicative of cold water and low salinities, was deposited. This was followed by a forced regression on Kriegers Flak, probably caused by a combination of isostatic rebound and a falling global sea level. Between 42 and 36 cal. ka BP wetlands and shallow lakes existed on Kriegers Flak (unit B). Macrofossil and pollen from this unit suggest tundra-like, or forest tundra-like vegetation, possibly with birch and pine in sheltered locations. From 28.5 to 26 ka, a thick succession of glaciolacustrine clay, unit C, was deposited at Kriegers Flak indicating a damming the Baltic Basin by an ice advance into Kattegat. The upper part of the stratigraphy has been reconstructed from published and new terrestrial sections in Skåne. Here three tills are identified. The lowermost, the Allarp Till, was deposited after the damming of the Baltic Basin at c. 30 ka. It was followed, after a deglaciation, by deposition of the Dalby Till, representing the Last Glacial Maximum advances including an early advance from southeast, the main advance from northeast and the first Young Baltic advances from southeast. The uppermost till, the Lund Till was deposited by the Öresund advance after a deglaciation. The deglaciation of southern Sweden was dated using cosmogenic nuclide surface exposure dating. We suggest that central Skåne was deglaciated between 17 and 16 ka. The deglaciation in southern Småland was dated to 15.6±0.8 and 16.6±0.9 ka, while a site in northern Småland was dated to 14.6±1.0 ka. Our northernmost site, situated only 25 km south of the Younger Dryas Moraine, was dated to c. 13.8±0.8 ka while cosmogenic surface exposure ages from Gotland suggest a deglaciation before 13.0±0.8 ka.
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| 9. |
- Möller, Per, et al.
(författare)
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Data set on sedimentology, palaeoecology and chronology of Middle to Late Pleistocene deposits on the Taimyr Peninsula, Arctic Russia
- 2019
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Ingår i: Data in Brief. - : Elsevier. - 2352-3409. ; 25, s. 1-35
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Tidskriftsartikel (refereegranskat)abstract
- This Data in Brief paper contains data (including images) from Quaternary sedimentary successions investigated along the Bol'shaya Balakhnya River and the Luktakh-Upper Taimyra-Logata river system on southern Taimyr Peninsula, NW Siberia (Russia). Marine foraminifera and mollusc fauna composition, extracted from sediment samples, is presented. The chronology (time of deposition) of the sediment successions is reconstructed from three dating methods; (i) radiocarbon dating of organic detritus (from lacustrine/fluvial sediment) and molluscs (marine sediment) as finite ages (usually <42 000 years) or as non-finite ages (>42 000-48 000 years) on samples/sediments beyond the radiocarbon dating limit; (ii) Electron Spin Resonance (ESR) dating on marine molluscs (up to ages >400 000 years); (iii) Optically Stimulated Luminescence (OSL) dating, usually effective up to 100-150 0000 years. Terrestrial Cosmogenic Nuclide (TCN) exposure dating has been applied to boulders resting on top of moraine ridges (Ice Marginal Zones). See (Moller et al., 2019) (doi.org/10.1016/j.earscirev.2019.04.004) for interpretation and discussion of all data. (c) 2019 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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| 10. |
- Möller, Per, et al.
(författare)
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Glacial history and palaeo-environmental change of southern Taimyr Peninsula, Arctic Russia, during the Middle and Late Pleistocene
- 2019
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Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 196
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Forskningsöversikt (refereegranskat)abstract
- We here reconstruct a glacial and climate history of arctic NW Siberia for the last similar to 600,000 years, based on the stratigraphy and chronology of 35 studied river sections on the southern Taimyr Peninsula. From this strati graphic mosaic we have identified four glacial events, marked by tills/glaciotectonics, which are intercalated with mainly marine sediments deposited in proglacial settings during transitions from glacial conditions into subsequent interglacials/interstadials. The traces of early shelf-based Kara Sea Ice Sheet (KSIS) glaciations in marine isotope stages (MIS) 12-14 and 8 are sparsely preserved, but these ice advances are suggested to have terminated far south into the central Siberian uplands, as also was the case with the younger Taz glaciation (MIS 6). The inception phase of the latter glaciation was complex, with ice advancing into a proglacial marine basin both from the south (Putorana - Anabar uplands) and the north. The deglaciation leading into the Karginsky interglacial (MIS 5e) was marked by the development of the southerrunost ice-marginal zones (IMZs) on the Taimyr lowlands - the Urdakh and Sampesa IMZs. The most recent (late Pleistocene) glacial cycle is recorded by three successively smaller KSIS advances from the Kara Sea shelf onto Taimyr, of which only the first, during Early Zyryanka (MIS 5d), reached south of the Byrranga Mountains, with its maximum extent marked by the Jangoda - Syntabul - Severokokorsky IMZ. Retreat of the ice margin during MIS 5c-b was accompanied by deposition of glaciomarine sediment in the proglacial basin and deposition of large successions of delta sediments in the foothills of the Byrranga Motmtains, reaching a >= 100 m above present sea level. The region north of the Byrranga Mountains was subjected to two subsequent KSIS glaciations, during MIS 4 and MIS 2, while the area south of the Byrranga Mountains transitioned to a terrestrial environment from the Middle into the Lower Zyryanka, as evidenced by deposition of fluvial, aeolian and ice-complex (Yedoma) sediments.
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