Holocene pollen stratigraphy of southern Sweden: a reappraisal using numerical methods   总被引：3，自引：0，他引：3  

H. JOHN B. BIRKS  BJÖRN E. BERGLUND 《Boreas: An International Journal of Quaternary Research》1979,8(3):257-279

Holocene pollen data from two sites in Blekinge and one site in Scania were zoned independently by four different numerical methods. Local or site pollen assemblage zones were established for each sequence. Numerical comparisons of the two sites in Blekinge reveal similarities which allow the definition of a series of regional pollen assemblage zones for Blekinge. Numerical comparisons between Blekinge and Scania indicate no such similarities, and emphasise the necessity to establish regional zones for each area. Correlations between areas can then be attempted using radiocarbon dates. The advantages and disadvantages of applying numerical methods for these purposes are discussed, and their broader applications to a Nordic pollen correlation project are outlined.  相似文献   

Diagenesis of aragonite from Upper Cretaceous ammonites: a geochemical case-study     

BJØRN BUCHARDT  STEPHEN WEINER 《Sedimentology》1981,28(3):423-438

Shell aragonite from ammonites collected in the Upper Cretaceous of West Greenland was investigated by means of macroscopic/microscopic visual evaluation, analyses of calcite/aragonite ratios, carbon and oxygen isotopic compositions and Sr and Mg concentrations of shell carbonate and of amino acid compositions of organic matrices. The results are: (1) Material visually classified as well preserved may have suffered diagenetic modifications of mineralogical and chemical composition. (2) Of the chemical and mineralogical parameters studied, amino acid composition, calcite/aragonite ratios and magnesium concentrations were found to be most sensitive to post-depositional modifications, while oxygen isotope composition and strontium concentrations showed detectable diagenetic modifications only after more pronounced alterations. (3) Based on the Mg/Ca ratios and calcite concentrations of the shell aragonite, a diagenetic classification has been proposed grouping the material into well preserved, moderately preserved and poorly preserved. (4) The chemical and mineralogical composition of the best preserved material suggests that the Upper Cretaceous ammonites had a shell composition similar to that of modern Nautilus and other aragonite-shelled molluscs.  相似文献   

Past changes in the geomagnetic field caused by glaciations and deglaciations     

ERIC OLAUSSON  BJÖRN SVENONIUS 《Boreas: An International Journal of Quaternary Research》1975,4(1):55-62

Contributions have been made to the theory of the relation between terrestrial magnetism and glaciations. The results are applied to the ice sheets of high-latitude regions. A review of Pleistocene palcomagnetic dating is given.  相似文献   

Quaternary stratigraphy of Norden, a proposal for terminology and classification   总被引：27，自引：0，他引：27  

JAN MANGERUD  SVEND T. ANDERSEN  BJÖRN E. BERGLUND  JOAKIM J. DONNER 《Boreas: An International Journal of Quaternary Research》1974,3(3):109-126

Principles and terminology for classification of the Quaternary are discussed, including lithostratigraphy, biostratigraphy. morphostratigraphy, climatostratigraphy and chronostratigraphy. The main conclusion is a proposal for a common chronostratigraphical classification of the Quaternary in Norden (and partly continental NW Europe). The Quaternary is subdivided into the Pleistocene and the Holocene Series. The Pleistocene is further subdivided into several provisional stages (Weichselian, Eemian, etc.), based on the sequence of glacials/interglacials. but with the boundaries preferably defined by stratotypes. The Late Weichselian and the Flandrian (Holocene) are subdivided into chronozoncs (Bolling, Older Dryas, Allerød, Younger Dryas, Preboreal, Boreal, Atlantic, Subboreal, Subatlantic) with the boundaries dcfined in conventional radiocarbon years.  相似文献   

RECENT LITTORAL AND SUBLITTORAL HIGH-MG CALCITE LITHIFICATION IN THE MEDITERRANEAN     

TORBJÖRN ALEXANDERSSON 《Sedimentology》1969,12(1-2):47-61

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Holocene humidity fluctuations in Sweden inferred from dendrochronology and peat stratigraphy   总被引：1，自引：0，他引：1  

BJÖRN ERIK GUNNARSON  ERS BORGMARK  STEFAN WASTEGÅRD 《Boreas: An International Journal of Quaternary Research》2003,32(2):347-360

Tree-ring and peat stratigraphy data were examined back to 5000 BC in order to identify and compare humidity changes in Fennoscandia. The temporal variation in distribution of Scots pine ( Pinus sylvestris L.) was used as a measure of past lake-level fluctuations in central Sweden. The chronology, which spans 2893 BC–AD 1998 with minor gaps in AD 887–907 and 1633–1650 BC and with additional floating chronologies back to 4868 BC, was cross-dated and fixed to an absolute timescale using a chronology from Torneträsk, northern Sweden. The peat stratigraphy from the Stömyren peat bog, south-central Sweden, was transformed into humification indices to evaluate humidity changes during the past 8000 years. The peat chronology is established by four tephra datings and eight ¹⁴C datings. Synchronous periods of drier conditions, interpreted from regeneration and the mortality pattern of pine, tree-ring chronology and peat humification, were recognized at c. 4900–4800 BC, 2400–2200 BC, 2100–1800 BC, 1500–1100 BC, AD 50–200, AD 400–600 and AD 1350–1500. Possible wetter periods were encountered at 3600–3400 BC, 3200–2900 BC, 2200–2100 BC, 1700–1500 BC, 1100–900 BC, 100 BC-AD 50, AD 200–400, AD 750–900 and AD 1550–1700. The wet and dry periods revealed by the tree rings and peat stratigraphy data indicate considerable humidity changes in the Holocene.  相似文献   

Holocene palaeoecology and shoreline displacement on the Biskopsmåla Peninsula, southeastern Sweden     

SHI-YONG YU  ELINOR ANDRÉN  LENA BARNEKOW  BJÖRN E. BERGLUND  PER SANDGREN 《Boreas: An International Journal of Quaternary Research》2003,32(4):578-589

High-resolution palaeoecological proxies of pollen, macrofossils and diatoms from an isolation lake provide a long-term record of the Holocene landscape history and shoreline displacement on the Biskopsmåla Peninsula in central Blekinge, SE Sweden. During the Preboreal/Boreal transition, the peninsula was sparsely vegetated by woodlands, along with lateglacial dwarf shrub/steppe communities. The lake basin was isolated from the shallow Yoldia Sea during this time. The regional climate improved from 10 700 cal. BP, evident as progressive expansion of Pinus-dominated mixed forest with deciduous trees. The lake basin was probably connected with the Ancylus Lake during the period 10700–10 100 cal. BP. Subsequently the basin became isolated again, corresponding to the Early Littorina Sea phase. Replacement of freshwater diatoms by those with brackish-water affinity at 8100 cal. BP indicates the initial transgression of the Littorina Sea in this basin. But not until 7500 cal. BP were brackish conditions fully established. Peaks of brackish-marine diatoms and dinoflagellates during 7500–7000 cal. BP indicate increased saltwater inflow to the Baltic Sea in response to global meltwater pulse 3. However, interactive changes in seagrass and stonewort macrofossil concentrations suggest that three minor transgressions during 5900–5300, 5000–4700 and 4400–4000 cal. BP occurred locally, associated with centennial-scale variations in regional wind pattern or coastal storminess. By 3000 cal. BP, the lake basin was finally isolated from the Baltic, and thereafter the landscape on the peninsula became gradually more influenced by human activities.  相似文献   

Late Quaternary environmental history of central Prins Karls Forland, western Svalbard   总被引：1，自引：0，他引：1  

TORBJÖRN ANDERSSON  STEVEN L. FORMAN  ÓLAFUR INGÓLFSSON  WILLIAM F. MANLEY 《Boreas: An International Journal of Quaternary Research》1999,28(2):292-307

This paper presents the results from stratigraphic and geomorphologic investigations in the Poolepynten area, Prins Karls Forland, western Svalbard. Field mapping, soil profile development and ¹⁴C dating reveal the existence of at least two generations of raised beach deposits. Well-developed raised beaches rise to the Late Weichselian marine limit at 36 m a.s.l. Discontinuous pre-Late Weichselian beach deposits rise from the Late Weichselian marine limit to approximately 65 m a.s.l. Expansion of local glaciers in the area during the Late Weichselian is indicated by a till that locally overlies pre-Late Weichselian raised beach deposits. Stratigraphic data from coastal sections reveal two shallow marine units deposited during part of oxygen isotope stage 5. The two shallow marine units are separated by a subglacially deposited till that indicates an ice advance from Prins Karls Forland into the Forlandsundet basin some time during the latter part of stage 5. Discontinuous glaciofluvial deposits and a cobble-boulder lag could relate to a Late Weichselian local glacial advance across the coastal site. Late Weichselian/early Holocene beach deposits cap the sedimentary succession. Palaeotemperature estimates derived from amino acid ratios in subfossil marine molluscs indicate that the area has not been submerged or covered by warm based glacier ice for significant periods of time during the time interval ca. 70 ka to 10 ka.  相似文献   

Relationship between Late Pleistocene sea‐level variations,carbonate platform morphology and aragonite production (Maldives,Indian Ocean)     

ANDREAS PAUL  JOHN J. G. REIJMER  JÖRN FÜRSTENAU  HANNO KINKEL  CHRISTIAN BETZLER 《Sedimentology》2012,59(5):1640-1658

A piston core from the Maldives carbonate platform was investigated for carbonate mineralogy, grain‐size distributions, calcium carbonate content and organic carbon. The sedimentary record was linked to Late Pleistocene sea‐level variations, using an age model based on oxygen isotopes obtained from planktonic foramanifera, nannofossil biostratigraphy and ¹⁴C age determinations. The correlation between the sedimentary record and Late Pleistocene sea‐level showed that variations in aragonite and mud during the past 150 000 years were clearly related to flooding and sea floor exposure of the main lagoons of the atolls of the Maldives carbonate platform. Platform flooding events were characterized by strongly increased deposition of aragonite and mud within the Inner Sea of the Maldives. Exposure events, in contrast, can be recognized by rapid decreases in the values of both proxy records. The results show that sediments on the Maldives carbonate platform contain a continuous record of Pleistocene sea‐level variations. These sediments may, therefore, contribute to a better understanding of regional and even global sea‐level changes, and yield new insights into the interplay between ocean currents and carbonate platform morphology.  相似文献   

Øvre Æråsvatn - palynostratigraphy of a 22,000 to 10,000 BP lacustrine record on Andøya, northern Norway     

TORBJØRN ALM 《Boreas: An International Journal of Quaternary Research》1993,22(3):171-188

Radiocarbon datings of a 4.10 m long lacustrine sequence from Lake Øvre Æråsvatn reveal continuous sediment accumulation during most of the Late Weichselian. starting before 21.800 ± 410 BP. The pollen record for the period 21,800 to 12,800 RP is uniform and is strongly dominated by Poaceae. Pollen influx variations suggest a succession of climatic ameliorations and deteriorations. Low to Middle Arctic. interstadial conditions prevailed from 21.000 to 19.650 (19.000) BP. A pronounced climatic deterioration followed. culminating at c. 18,85018,500 BP. synchronous with a glacial advance over the nearby Endletvatn and Nedre Æråsvatn basins At c 18.300 BP. a climatic amelioration triggered important changes in the lacustrine environment. Organogenic gyttja (2.56 m) accumulated from 18,300 to 15,000 BP. indicating a eutrophic lacustrine environment. Sparsity of minerogenic material suggests an arid climate with low surface runoff. Further ameliorations occurred from c. 17,400 to 16,800 BP and 16,000 to 15,000 BP. From c. 15.000 BP onwards. a climatic deterioration is indicated. The 17,800 to 10,500 BP record is fragmentary. At c. 10,500 BP. an improving climate induced establishment of Betula nana –Empetrum heaths. rapidly succeeded by mesic Betula pubescens Filipendula woodlands.  相似文献