ISSN:
1573-0417
Schlagwort(e):
Early Holocene
;
irregular isostatic uplift
;
western Sweden
;
diatom stratigraphy
;
magnetic stratigraphy
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
,
Geologie und Paläontologie
Notizen:
Abstract In the 1920's the Swedish geologist Lennart von Post found evidence of irregular early Holocene isostatic uplift in the region northwest of Lake Vänern in western Sweden. von Post based his conclusions on levellings of ancient shore lines. These were indirectly dated by pollen stratigraphical investigations in basins situated at approximately the same altitudes as the shore lines. To test von Post's hypothesis, we have adopted a different methodological approach. The sediments in twelve small lake basins, within five minor areas in this region, have been investigated with respect to when they became isolated from ancient Lake Vänern. Initially all the lake thresholds were levelled. Altitudes range between 165 and 96 m above sea level. By combining the results of mineral magnetic and diatom stratigraphical analyses it has been possible to determine the level in the sediment when the basin became isolated. The 14C age of this isolation level has been inferred from AMS dates based on the NaOH-soluble fraction of bulk sediment, partly with very low organic content. Altogether, 36 radiocarbon datings have been carried out, ranging from 10080 to 8800 14C years BP. Pollen analyses, and subsequent correspondence analysis (CA) of all pollen spectra, were carried out around the isolation level in each basin as a complement to the AMS datings. If the region had been subject to irregular isostatic uplift, lakes at the same altitude in the five areas should have been isolated at different times. The AMS determined isolation ages, ‘corrected’ according to CA of the pollen stratigraphy and compensated for the relatively higher rebound of the northerly situated sites support von Post's conclusion, from the beginning of this century, that the region northwest of Lake Vänern has been subjected to irregular isostatic uplift.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00176989
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