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Palynology and sediment slumping in a high arctic Greenland lake 总被引：1，自引：1，他引：1
BENT FREDSKILD 《Boreas: An International Journal of Quaternary Research》1995,24(4):345-354
A 103-cm core from a high arctic lake (80°49'N, 15°00'W) on Amdrup Land, NE Greenland has been analysed for pollen and other microfossils, as well as bulk samples from 10 cores for macrofossils. AMS 14 C-dating of aquatic mosses ( Drepanocladus exannulatus and Scorpidiurn scorpioides ) revealed that the lowermost 90 cm of the core was deposited during a 1.5-2 ka interval in the early Holocene, before the appearance of Salix arctica which immigrated to N Greenland c . 7 ka BP. Armeria scabra , now extinct in the area, larval cases and apotomes of Apatcmiu zonella , today not known north of c. 77°N, and other indices point to a climate warmer than that of today. A thin, sandy layer 13 cm below the lake bottom, accompanied by marked changes in the content of pollen and macrofossils, such as the sudden occurrence of large amounts of Salix pollen and leaves, indicates a large hiatus. This is confirmed by the dating to c . 7 ka BP of mosses just below the sand, and of Salix leaves just above it to c . 1 ka BP. The hiatus must be caused by sediment slumping which transported all the sediment from the intervening period to the deeper part of the lake. A similar, sandy layer in the uppermost 2–6 cm may be caused by younger, (sub-)recent slumping, or both may be the result of the same disturbance. The possibility of a reservoir effect causing too old 14 C-ages for the moss is discussed. 相似文献
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PER SANDGREN BENT FREDSKILD 《Boreas: An International Journal of Quaternary Research》1991,20(4):315-331
Magnetic measurements have been carried out on four lake sediment successions in interior S. Greenland. The longest record extends back to 7000 C14 years BP. Based on the magnetic susceptibility six units have been distinguished. The results of the magnetic analyses show a close correlation between the four investigated sites, corroborated by pollen stratigraphy and radiocarbon dates. The period after the deglaciation, lasting for some thousand years, was characterized by sparse vegetation on the unstable soils. Erosion rates were high as revealed by the high concentration of magnetic minerals. Along with the spreading of dwarf-shrub heaths the soils stabilized, reducing the eroding capacity, and are seen as decreasing concentrations of magnetic minerals in the sediments. During the subsequent period there seems to have been an equilibrium between climate and vegetation resulting in minimal erosion. The arrival of the Norsemen in c. AD 1000, introducing cattle and cutting down the 'forests', seems to have caused a disturbance in the fragile environment. It destroyed the attained equilibrium and is seen in the sediment records as an increase in magnetic concentrations. Due to the disappearance of the Norsemen in the 15th century, or slightly later, a new phase of soil stabilization began. A new and still ongoing phase of even more severe soil erosion is connected with the reappearance of man, now as a sheep breeder, in the beginning of this century. Magnetic concentrations are again high, being in the same order of magnitude as during early Holocene time. 相似文献
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BENT HASHOLT M.Sc. 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):30-39
Hasholt, B., 1976; Hydrology and transport of material in the Sermilik area 1972. Geografisk Tidsskrift 75: 30–39 København june 1976. Investigations of water discharge and transport of material have been carried out in the area around the Mitdluagkat glacier in East Greenland. Precipitation and snow-melt were measured and compared with the discharge. The relationship between stage, discharge and concentration of suspended sediments were found, and the results were used to calculate hourly values of suspended sediment transport. In a few cases bed-load and dissolved load were measured at the same time as suspended load. The ratio between the transport components has been used to estimate the total load into the sea. 相似文献
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BENT VALEUR 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):23-28
Valeur, Bent: Nyere tendenser i dansk geografiundervisning på det gymnasiale niveau. Geografisk Tidsskrift 83: 23–27. Copenhagen, June 1, 1983. Education in geography at the secondary schools in Danmark. 相似文献
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BENT FREDSKILD ULRIK RØEN 《Boreas: An International Journal of Quaternary Research》1982,11(3):181-185
Examination two peat samples collected at Kep København, Peary Land, Northgreenland, revealed the presence fo fossils of Betula nana, Menyanthes trifoliata and other plants which do not occur as fao north today. likewise, remains fo Cladocera (e.g. Alonella excisa ), beetles (e. g. Gyrinus opacus and Bembidion grapi ) and other animals, none of which live in the area today, are present. The occurrence of these fossils, coupled with a radiocarbon date giving an infinite age, suggest that the peat is an interglacials deposit. 相似文献
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Abstract— Precise radiometric age determination of the Kaalijärv meteorite craters on the island of Saaremaa in Estonia have so far proved inconclusive. Here we present trace element analyses of peat cores taken several kilometers away from the Kaalijärv craters that reveal a distinct Ir‐enriched layer produced by the meteorite impact. By radiocarbon dating the peat cores, we have determined for the first time the precise age of the impact that generated the Kaalijärv craters. The calibrated date of the impact is 400–370 B.C. at ± 1σ. 相似文献
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BENT FREDSKILD 《Boreas: An International Journal of Quaternary Research》1990,19(2):201-201
Book reviewed in this article:
Faegri, K. & Iversen, J. 1989: Textbook of Pollen Analysis 相似文献
Faegri, K. & Iversen, J. 1989: Textbook of Pollen Analysis 相似文献
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In the raised bog Draved Mose, rates of peat formation and degrees of humification were determined in two peat sections. Based on 59 calibrated C-14 dates, accumulation rates during the last 6500 years of 0.16 to 0.80 mm/year were found. The peat layers were analyscd for Sphagnum species, rhizopods, and pollen and spores. A clear relation between humification degrees and humidity at the time of formation was found, while the relation between measured growth rates and degrees of humification varied throughout the 2.5 m thick peat section. These variations are thought to be mostly a result of autocompaction. 相似文献
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BENT HASHOLT HENRIK SØGAARD 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):72-92
Hasholt, B. & H. Søgaard 1978: Et forsøg på en klimatisk-hydrologisk regionsinddeling af Holsteinsborg kommune (Sisimut). Geografisk Tidsskrift 77: 72–92. København juni 1,1978. The Holsteinsborg municipality (Sisimut) has been divided into climatic and hydrological regions. The investigation is of a preliminary character due to the limited possibilities for field work. The regionalization is based upon selected climatological and hydrological parameters; these were primarily snow cover (precipitation), potential evapotranspiration, run-off, and temperature. Measurements of water quality have been used as indicator of the aridity in the area. 相似文献