Björn E. Berglund

Human impact and climate changes—synchronous events and a causal link?

Interaction between cultural development and the natural environment is generally accepted. Holocene climate change is described as one of the main environmental factors behind a step-wise development of the cultural landscape in Northwest Europe. Seven periods of human impact changes-5900, 5500, 4500, 3800, 3000-2800, 1500 and 1100 cal. BP-are defined and compared with reconstructed climatic scenarios, based on insolation, glacier activity, lake and sea levels, bog growth, tree line, and tree growth. There is a positive correlation between human impact/land-use and climate change, although precise correlations are difficult because of weaknesses in the chronology. Future studies of annually laminated (varved) lake sediments and wiggle-matched radiocarbon sequences are emphasized, as well as a combination of palaeoecology and archaeology. It is hypothesized that agrarian society and the landscape developed step-wise, dependent on the interaction between the technological/social complex and the ecological capacity of a region, highly influenced by climate

Modern pollen/land-use relationships as an aid in the reconstruction of past land-uses and cultural landscapes: an example from south Sweden

An on-going, integrated project concerning modern pollen/vegetation/land-use relationships in south Sweden is outlined. Some preliminary results and their potential uses in palaeoecological reconstructions are discussed. Moss polsters were collected from 92 examples of vegetation/land-use areas of south Sweden (e.g. nonfertilized grazed areas, burned and grazed heaths, traditionally managed fodder-producing meadows, etc.). A total of 23 land-use (e.g. management type) and environment variables (e.g. soil chemistry) is available for 84 sites. The 84 sample data-set was analysed by canonical correspondence analysis and associated statistical testing using Monte Carlo permutation tests to explore and test patterns of modern pollen variation in relation to the environment, and by weighted averaging regression and calibration to derive local-scale environmental and land-use reconstructions from fossil pollen assemblages preserved in a soil profile.

Littorina Transgressions in Blekinge, South Sweden a Preliminary Survey

Abstract Lagoon sediments from the Littorina time have been investigated in Blekinge by biostratigraphic methods. The absolute chronology is based on 50 radiocarbon datings. The results from nine sites have been synthesised into a diagram to show the shore line displacement. The complex Littorina transgression has been subdivided into six Atlantic and Sub-Boreal transgressions, no. I dated to 5000–4700, II to 4500–4300, III to 3900–3600, IV to 3500–3300 but faintly separated from the preceding one, V to 2700–2500 and VI to 2100–1900 B. C. It is supposed that the sea in this area reached its maximum level during no. IV.

Late-Glacial Stratigraphy and Chronology in South Sweden in the Light of Biostratigraphic Studies on Mt. Kullen, Scania

Abstract Biostratigraphic investigations, mainly pollen-analytical studies of lake sediments, have permitted the recognition of the Allerod as well as the Boiling oscillations on Mt. Kullen in NW Scania. By correlation with other sites this supports the theory that the Boiling zone corresponds to the deglaciation from North Scania to Central Smaland, in varve and radiocarbon years about 10,400–10,100 B. C., and that the Allerod zone corresponds to the deglaciation of Central and North Smaland to the Fennoscandian end moraines about 9,900–9,100 B.C. There is some evidence for local vegetational differentiation due to climate and soil. On the basis of the chemical stratigraphy, soil leaching around the lakes is discussed.

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

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 Biskopsmala 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 10 700-10 100 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.

Soil Conditions and Late-Glacial Stratigraphy

Abstract Referring to Late-Glacial lake sediments at Mt. Kullen (NW Scania) studied by means of biostratigraphic and chemical methods the authors discuss the development of one of the lakes and the surrounding terrestric soils. For all constituents analysed in the sediments the annual deposition per unit area has been calculated. The decreasing supply of inorganic material during the Late-Glacial time is related to the development of a stable humus layer. The content of organic matter in the sediments may be due more to a variation of the soil erosion than to changes in the production of organic matter. Soil leaching during the mild Allerod period is indicated and correlated with the vegetational development.

Biotic responce to climatic changes during the time span 13 000 - 10 000 BP. - A case study from SW Sweden.

Palaeoecological studies based on analysis of pollen, plant macro-fossils and insect remains at a stratigraphic reference site, covering the time span 13,000–10,000 yrs B.P., in SW Sweden (Hakulls Mosse, province of Skane) are interpreted against the two dominant palaeoclimatic models: the palaeobotanical model (Iversen) and the palaeoentomological model (Coope). An important time lag is found in the vegetation response to climatic improvement after deglaciation, which means that the biotic changes are best explained against the palaeoentomological model. This implies optimal summer temperatures 13,000–12,500 followed by a gradual deterioration until 11,000 when a sudden drop of temperature leads to a minimum between 11,000 and 10,500. A distinct rise of summer temperature around 10,500 is confirmed although the time lag in the vegetation response is ab. 300 years.

Mid-Holocene Littorina Sea transgressions based on stratigraphic studies in coastal lakes of NW Russia

Abstract The mid-Holocene Littorina Sea transgression has been studied in sediment cores from four coastal lakes in NW Russia. The basins are situated in the same drainage system at elevations from 6.9 to 9.2 m a.s.l. Complementary parameters have been applied to identify water-level changes. Chronological models are based on AMS radiocarbon dating of bulk sediments but also wood remains and moss sedge peat has been dated in a few cases. All radiocarbon ages have been calibrated to calendar years BP (cal. BP). Between 8000 and 6000 cal. BP the present-day lakes were in contact with the Littorina Sea and brackish conditions prevailed. The water level was higher than 6 m a.s.l. clearly documented in all four basins. A peak reaching above the level of the uppermost lake (9.2 m a.s.l.) has been dated to ca. 7500 cal. BP. During the high level phase a short lived regression/transgression is recognized in all but the uppermost basin. This minor water level fluctuation lasted for a few hundred years around 7000 cal. BP. It is reflected in various parameters in the different basins. Correlations are made with recent studies from Blekinge in southeastern Sweden situated at the 10 m Littorina isobase as the present investigation area. The parallel Littorina Sea history in these two areas seems to confirm a multi-transgression pattern across the southern Baltic Sea.

New insights on the Yoldia Sea low stand in the Blekinge archipelago, southern Baltic Sea

Abstract One sediment core from the Järnavik bay in Blekinge archipelago has been investigated for its content of pollen and diatoms and its chemical properties. Two levels were also dated by radiocarbon. Based on the results the sediment sequence analysed has been divided into three environmental units largely corresponding to the lithology of the sequence. A lowermost unit consisting of weakly varved and homogeneous clay was deposited during the end of the brackish phase of the Yoldia Sea at a moderate water depth. On top of this unit a gyttja-clay unit was deposited. The onset of the deposition of this unit has been dated to c. 11 100 cal. yrs. BP. An increasing organic production and increased terrestrial influence is recorded in the chemical data and a very shallow water depth is indicated in the pollen and diatom flora. These results point to conditions in a bay probably isolated from the Yoldia Sea. A local tentative shore displacement curve have been constructed and it is proposed that this unit represents the low stand at c. -18 m during the Yoldia Sea stage in this part of the Baltic Sea basin. The uppermost unit consists of homogeneous clay with a low content of organic carbon. An increasing water depth is indicated by the composition of both pollen and diatoms. The diatom flora also displays an increase in freshwater species. This environmental change was probably the result of a transgression in the beginning of the Ancylus Lake stage.

Mid-Holocene Baltic Sea transgression along the coast of Blekinge, SE Sweden ancient lagoons correlated with beach ridges

Abstract The mid-Holocene Littorina transgression in southern Scandinavia is well documented. Multiple-stratigraphic sequences in ancient Littorina lagoons in the coastal area of Blekinge, SE Sweden reveal a maximum relative sea level of 7–8 m above present sea level between 8000–6000 cal. BP. Evidence for at least two transgression waves is found within this period. In this study these are documented in one modern lake and correlated with an ancient beach-lagoon stratigraphy. Furthermore, two younger transgressions are documented at one site, altogether establishing a firm transgression chronology for the time span 8000–4000 cal. BP (sea level 5–8 m a.s.l.) as a basis for understanding the dynamics of Baltic sea-level changes. Neolithic cultural layers are correlated to regression periods, indicating more favorable conditions for beach settlement between stormy transgression periods.