Tore Påsse

Shore-level displacement in Fennoscandia calculated from empirical data

Abstract Shore-level displacement and glacio-isostatic uplift in the area affected by the Scandinavian ice is calculated from empirical data. Besides 79 shore-level curves from Scandinavia the calculations are also based on some detailed lake-tilting investigations and information concerning present relative uplift recorded by precision levelling and tide gauge data. The course of glacio-isostatic uplift is expressed in solely mathematical terms. The model is transformed to a GIS-application using levelling data. Maps showing the distribution between land, lakes and sea at different times are produced by this application. These maps can also be designed to show changes of the hydrography through time including changes in lakes, glacial lakes, rivers and drainage basins. The accuracy of the calculated shore-levels is generally very high. A result of the calculation is that the existence of the Baltic Ice Lake is questioned as both the calculations and an analysis of the earlier used proofs of the Baltic Ice Lake show that the Baltic basin was most probably at sea level.

Isostatic land uplift and Mesolithic landscapes: lake-tilting, a key to the discovery of Mesolithic sites in the interior of Northern Sweden

Until recently only a few Mesolithic sites were known from the interior of N. Sweden, although extensive archaeological surveys have been carried out since the 1950s. The lack of archaeological data made every attempt to interpret the process of pioneer colonization quite fruitless. In this paper we present a model of non-uniform glacio-isostatic uplift and lake-tilting used to identify potential areas of Mesolithic habitation. By reconstructing shoreline displacement of ancient lakes, archaeological, palaeoecological and geological studies have resulted in the discovery of a significant number of Mesolithic sites and of an early post-glacial landscape previously unknown.

Shore displacement during the Late Weichselian and Holocene in the Sandsjöbacka area, SW Sweden

Abstract A shore displacement curve has been constructed for the Sandsjobacka area in northern Halland comprising the period 13,000 years B. P. to the present day. The course of the shore level displacement was a rapid regression during the Late Weichselian with a regression rate of 24 mm/year. The regression minorant was reached at about 9,200 B. P. and followed by a sequence of oscillation minima at about 9,200, 8,750, 8,300, 7,850 and 7,400 years B. P. The transgression majorant was reached about 7,200 years B. P.

Cotton wool filtering for pollen enrichment

Abstract Clay and clayey sediments usually have a low content of pollen and consequently some form of enrichment is required before a pollen analysis can be performed. The cotton wool method offers the opportunity of concentrating pollen from samples containing clay in a quick and effective manner. It involves removing the clay fraction from the deflocculated sample by filtering through a cotton wool filter. The residue left on the filter is then removed and concentrated by density separation.

Distribution, genesis and annual-origin of De Geer moraines in Sweden: insights revealed by LiDAR

Abstract De Geer moraines (DGMs) were first identified in Sweden by Gerard De Geer in 1889 and have been mapped since then in many parts of Sweden. Using airborne Light Detection and Ranging (LiDAR) data, we have mapped DGMs over the entire country, and we show that they occur predominantly in two distinct areas: in south-central Sweden north of the Middle Swedish end-moraine zone and in northeast Sweden. DGM formation occurs predominantly where the local relief is low, the ice-margin retreat rate was high and the sedimentation rate low. Formation of DGMs occurred over short time spans of a few hundred years – between 11 500 and 11 000 cal years BP for the southern group and from 10 700 and 9900 cal years BP for the DGMs in the north. DGMs have been suggested to be made by a number of processes at subaquatic ice margins, including pushing during winter readvance, squeezing into subglacial crevasses, deformation during calving events and deposition as subaquatic fans. Therefore, we recognize DGMs to be equifinal landforms, made by several related mechanisms. However, we observe that the most common occurrence of DGMs in Sweden are as regularly spaced even ridges below the highest shoreline whose spacing closely corresponds to independently determined ice-margin retreat rates. We therefore suggest that where regular evenly spaced DGMs occur, their spacing likely represents the local ice-margin retreat rate, and that the majority of these ridges were made annually by winter advances.

Erratic flint along the Swedish west coast

Abstract Sedimentary rock clasts, especially flint, are abundant in glacial clay and shore deposits in the coastal area of Halland, southwestern Sweden, while they are absent in till and glaciofluvial sediments in this same area. The clasts were deposited as drop from icebergs or drift ice. Qualitative analyses reveal that the most likely provenance of the clasts is the Oresund area, including western Skane and eastern Danmark. 14C-dating of shells of marine molluses and barnacles enabled a determination of the time interval for the deposition of the sedimentary rock clasts. The deposition started in connection with the deglaciation of the area c. 13,500 B.P., or somewhat later, and it ceased c. 12,200–12,000 B.P. The deposition of sedimentary rock clasts during this period indicates the existence of a glacier with a frontal position in the Kattegat. This glacier is correlated to the Low Baltic readvance.

Empirical estimation of isostatic uplift using the lake-tilting method at Lake Fegen and Lake Säven, Southwestern Sweden

AbstractA nonuniform glacio-isostatic uplift results in differential uplift for different parts of a lake. If the lake outlet is situated in the area with the greatest rate of uplift, then the lake will be continuously transgressed. Ancient lake levels can be estimated by dating transgressed peat at different depths in such a lake. Two lakes in southwestern Sweden have been investigated by this method and the course of glacio-isostatic uplift has been determined empirically. The uplift can be expressed by an exponential function through the following formula

Genesis of hummocks found in tunnel valleys : an example from Hörda, southern Sweden

U = - \frac{{\upsilon _0 }}{{2.25 \times 10^{ - 4} }} + \frac{{\upsilon _0 }}{{2.25 \times 10^{ - 4} }}e^{2.25 \times 10^{ - 4} xt}