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- Bennike, Ole, et al.
(författare)
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An Early Pleistocene interglacial deposit at Pingorsuit, North-West Greenland
- 2023
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Ingår i: Boreas. - : John Wiley & Sons. - 0300-9483 .- 1502-3885. ; 52:1, s. 27-41
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Tidskriftsartikel (refereegranskat)abstract
- At the Pingorsuit Glacier in North-West Greenland, an organic-rich deposit that had recently emerged from the retreating ice cap was discovered at an elevation of 480 m above sea level. This paper reports on macrofossil analyses of a coarse detritus gyttja and peaty soil, which occurred beneath a thin cover of till and glacifluvial deposits. The sediments contained remains of vascular plants, mosses, beetles, caddisflies, midges, bryozoans, sponges and other invertebrates. The flora includes black spruce, tree birch, boreal shrubs and wetland and aquatic taxa, which shows that mires, lakes and ponds were present in the area. We describe a new extinct waterwort species Elatine odgaardii. The fossils were deposited in a boreal environment with a mean July air temperature that was at least 9 degrees C higher than at present. The fossil assemblages show strong similarities with others from Greenland that have been assigned an Early Pleistocene age, and we suggest a similar age for the sediments found at the margin of the Pingorsuit Glacier. At the Pingorsuit Glacier in North-West Greenland, an organic-rich deposit was discovered at an elevation of 480 m above sea level. The sediments contained remains of vascular plants, mosses, beetles, caddisflies, midges, bryozoans, sponges and other invertebrates. The fossils were deposited in a boreal environment with a mean July air temperature that was at least 9 degrees C higher than at present.
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- Bennike, Ole, et al.
(författare)
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Dating of a muskox (Ovibos moschatus) skull fragment from Jamtland, Sweden: Middle Weichselian age
- 2014
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Ingår i: GFF. - : Informa UK Limited. - 2000-0863 .- 1103-5897. ; 136:2, s. 406-409
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Tidskriftsartikel (refereegranskat)abstract
- A radiocarbon age determination of a tundra muskox (Ovibos moschatus) skull fragment from Jamtland, central Sweden gave an age of 44 000 +/- 1500 C-14 years BP or c. 46-49 cal. ka, indicating that the species was a member of the Middle Weichselian fauna of Sweden. The age confirms that central Sweden was ice-free during parts of the Middle Weichselian, prior to the last glacial maximum, as shown by previous studies. The region was probably characterised by treeless arctic to subarctic tundra environments.
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- Bennike, Ole, et al.
(författare)
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Dating of the Narssarssuaq stade in southern Greenland
- 2007
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 17:2, s. 279-282
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Tidskriftsartikel (refereegranskat)abstract
- Following the Holocene thermal maximum, the Greenland ice sheet began to expand, and many local glaciers formed. The maximum extent of most outlet glaciers from the Inland Ice was reached around 100 to 200 years ago. However, some exceptions have been recorded. In southern Greenland, the Neoglacial Narssarssuaq stade marks an older re-advance that exceeded the historical advance. The dating of the Narssarssuaq stade has been much debated. Here we present new radiocarbon dates from a sediment core collected from a small lake within the moraines formed during this stade. A minimum age for the Narssarssuaq stade of around 1200 yr BP is suggested from the dates.
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| 6. |
- Bennike, Ole, et al.
(författare)
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New interglacial deposits from Copenhagen, Denmark : marine Isotope Stage 7
- 2019
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Ingår i: Boreas. - : Wiley-Blackwell. - 0300-9483 .- 1502-3885. ; 48:1, s. 107-118
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Tidskriftsartikel (refereegranskat)abstract
- During a pre-site survey and construction of a new metro route and station in Copenhagen, fossiliferous organic-rich sediments were encountered. This paper reports on multidisciplinary investigations of these organic sediments, which occurred beneath a sediment succession with a lower till, glacifluvial sand and gravel, an upper till and glacifluvial sand. The organic sediments were underlain by glacifluvial sand and gravel. The organic-rich sediments, which were up to 0.5 m thick, accumulated in a low-energy environment, possibly an oxbow lake. They were rich in plant fossils, which included warmth-demanding trees and other species, such as Najas minor, indicating slightly higher summer temperatures than at present. Freshwater shells were also frequent. Bithynia opercula allowed the sediments to be put into an aminostratigraphical framework. The amino acid racemization (AAR) ratios indicate that the organic sediments formed during Marine Isotope Stage 7 (MIS 7), which is consistent with optically stimulated luminescence dating that gave ages of 206 and 248 ka from the underlying minerogenic deposit. The assemblages from Trianglen are similar to interglacial deposits from the former Free Port (1.4 km away) in Copenhagen, except that Corbicula and Pisidium clessini were not found at Trianglen. The presence of these bivalves at the Free Port and the ostracod Scottia tumida at Trianglen indicates a pre-Eemian age. AAR data from archived Bithynia opercula from the Free Port were almost identical to those from Trianglen, indicating that the two sites are contemporary. We suggest the Trianglen interglacial be used as a local name for the MIS 7 interglacial deposits in Copenhagen. MIS 7 deposits have rarely been documented from the region, but MIS 7 deposits may have been mistaken for other ages. The use of AAR ratios in Bithynia opercula has a great potential for correlation of interglacial non-marine deposits in mainland northern Europe.
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| 7. |
- Bennike, Ole, et al.
(författare)
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Strandforskydning i Grönland
- 2006
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Ingår i: Groenland (Charlottenlund). - 0017-4556. ; 5, s. 188-202
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 8. |
- Bennike, Ole, et al.
(författare)
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Tristan da Cunha
- 2005
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Ingår i: Naturens Verden. - 0028-0895. ; 88:7/8, s. 10-23
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 9. |
- Björck, Svante, et al.
(författare)
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Relative sea level changes and glacio-isostatic modelling in the Beagle Channel, Tierra del Fuego, Chile : glacial and tectonic implications
- 2021
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 251
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Tidskriftsartikel (refereegranskat)abstract
- The Beagle Channel crosses the southernmost tip of South America (Tierra del Fuego), connecting the South Atlantic with the Southeastern Pacific. Raised beaches occur up to 10 m above mean sea level (m a.m.s.l.), especially along the northern (Argentinian) shore, and have been dated using marine shells. The southern (Chilean) shore is well-known for its abundance of shell middens at different levels above the present shore, particularly along the island of Isla Navarino, but the relative sea level history in this glacially impacted landscape has not previously been investigated. In this study we present postglacial relative sea level changes on Isla Navarino, based on sediment cores from six lagoons, bogs or lakes, and stratigraphic investigations of three open sections, of which one is of MIS 5e age. In addition, one core from a lagoon in the south-western Beagle Channel has been analysed and a system of terraces was mapped in the north-western Beagle Channel. The analyses of the core sites have resulted in two tentative relative sea level curves, displaying a rapid sea level rise at 8500−6500 cal yr BP, amounting to ∼10 and 14 m in eastern and western Isla Navarino, respectively, and reaching levels of ∼8 and > 10 m, respectively, followed by a slow relative sea level fall. Our sea level observations have been compared with a range of modelling results of glacial-isostatic adjustments (GIA) for estimating timing of deglaciation and ice sheet thicknesses. Based mainly on the GIA modelling of the altitude of the MIS 5e beach sediments, situated at 13 m, we can conclude that no other uplift than GIA is needed to explain their altitude. Regarding the modelling of postglacial sea levels we can conclude that no model has been found that satisfies all of the observational evidence, but that deglaciation most likely preceded Northern Hemisphere main deglaciation by at least 3 kyr, which agrees with the deglaciation age of Isla Navarino (>16 000 cal yr BP). In addition, our model runs imply that the Patagonian and Tierra del Fuego ice sheet thicknesses were in the order of ∼1500 m.
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| 10. |
- Buckland, Philip I., Dr. 1973-, et al.
(författare)
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Mid-Devensian climate and landscape in England : new data from Finningley, South Yorkshire
- 2019
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Ingår i: Royal Society Open Science. - : Royal Society Publishing. - 2054-5703. ; 6:7
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Tidskriftsartikel (refereegranskat)abstract
- While there is extensive evidence for the Late Devensian, less is known about Early and Middle Devensian (approx. 110-30 ka) climates and environments in the UK. The Greenland ice-core record suggests the UK should have endured multiple changes, but the terrestrial palaeo-record lacks sufficient detail for confirmation from sites in the British Isles. Data from deposits at Finningley, South Yorkshire, can help redress this. A channel with organic silts, dated 40 314-39 552 cal a BP, contained plant macrofossil and insect remains showing tundra with dwarf-shrub heath and bare ground. Soil moisture conditions varied from free draining to riparian, with ponds and wetter vegetated areas. The climate was probably low arctic with snow cover during the winter. Mutual climatic range (MCR), based on Coleoptera, shows the mean monthly winter temperatures of -22 to -2 degrees C and summer ones of 8-14 degrees C. Periglacial structures within the basal gravel deposits and beyond the glacial limits indicate cold-climate conditions, including permafrost. A compilation of MCR reconstructions for other Middle Devensian English sites shows that marine isotope stage 3-between 59 and 28 ka-experienced substantial variation in climate consistent with the Greenland ice-core record. The exact correlation is hampered by temporal resolution, but the Finningley site stadial at approximately 40 ka may correlate with the one of the Greenland stadials 7-11.
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