Problems and potential of OSL-dating deglacial and interstadial sediments in Sweden

• Several recent OSL-ages from Sweden have been inconsistent with geological interpretation, commonly due to age overestimation, and have been met with some scepticism. We explore the problems and potential of OSL-dating in Sweden by analysing quartz OSL-ages from several known-age deglacial sites in southern and central Sweden and by investigating their luminescence properties. Two problems for obtaining good and reliable ages are incomplete bleaching and low-sensitivity quartz. Incomplete bleaching is partly, but not entirely, the cause of age overestimation and can be avoided by selecting suitable sediment facies. Low sensitivity leads to practical problems in measurements and larger uncertainties in dose estimates. On the other hand, potential for good OSL-dating is shown by high-sensitivity quartz from sites that contain both Dala sandstone clasts and sediments that may have had extensive reworking during the Quaternary. This knowledge is useful for interpreting OSL-results from unknown-age interstadial sites. Most interstadial sites in Sweden contain only fragmentary records and represent single events and OSL-ages from such sites lack a context to which the results can be related. It is for example rarely possible to get OSL-samples from a stratigraphic succession that spans a significantly longer time than the resolution of the method or find sites where dates from more than one stratigraphically overlying interglacial, interstadial or deglacial bed can be compared. As interstadial OSL-ages thus largely have to stand on their own, multiple samples and detailed data analyses are necessary to give credibility to the results given the Swedish record of OSL-difficulties. From a luminescence point of view, sites fulfilling the positive criteria identified for deglacial deposits should be selected, but the setting and nature of the most geologically interesting interstadial sites are not always obliging.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geology (hsv//eng)

Nyckelord

Quaternary geology

Kvartärgeologi

Publikations- och innehållstyp

vet (ämneskategori)

kon (ämneskategori)