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This paper focuses on how landscape development in areas of land uplift has come to direct the primary human colonisation
on the coastal areas in north-western Estonia. A Swedish-speaking minority population has at least since medieval times settled
these areas. On the basis of an estimation of the rate of land uplift, the shoreline development and topography of a section
of the coast was reconstructed. In this respect, it appears that large changes have occurred in that during the Middle Ages,
the coast was much steeper but also much longer than today, full of little bays and points. This means that the drainage of
near-shore areas was more intensive and that it was possible to find suitable landing places and well-sheltered harbours in
some locations. These locations appear to have been primary settlements of the Swedish-speaking colonists and are very similar
to coastal settlements of the same age along other coasts of the central Baltic Sea basin. Thus, the results presented in
the paper allow the selection of primary research sites for field studies of the early settlement history of this ancient
Estonian minority.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Holocene lake-level changes and their reflection in the paleolimnological records of two lakes in northern Estonia 总被引：1，自引：0，他引：1
Jaan-Mati Punning Mihkel Kangur Tiiu Koff Göran Possnert 《Journal of Paleolimnology》2003,29(2):167-178
Sediment cores from two neighbouring lakes (Viitna Linajärv and Viitna Pikkjärv) in northern Estonia were studied to determine lake-level fluctuations during the Holocene and their impact on biogeochemical cycling. Organic matter and pollen records dated by radiocarbon and radiolead indicated a water level rise in both lakes during the early Holocene (c. 10 000–8000 BP). A regression followed around 7500 BP and several transgressions occurred during the latter half of the Holocene, c. 6500 and 3000 BP. Human impact during the last centuries has caused short-term lake-level fluctuations and accelerated sediment accumulation in the lakes. The differences in water depth led to variations in sediment formation. During 10 000–8000 BP (Preboreal and Boreal chronozones) mineral-rich sediments with coloured interlayers deposited in L. Linajärv. These sediments indicate intensive erosion from the catchment and oxygen-rich lake, which favoured precipitation of iron oxides and carbonates. Fluctuations in water depth, leaching of nutrients from catchment soils and climatic changes increased the trophy of L. Linajärv around 6000 BP. The subsequent accumulation of gyttja, the absence of CaCO3 and the decrease in both the C/N ratio and phosphorus content in the sediments also indicate anoxic conditions in the hypolimnion. The similarity in the development of L. Linajärv and L. Pikkjärv and their proximity made it possible to discern the impact of water depths changes on biogeochemical cycling in lakes. 相似文献
3.
Neil L. Rose David Morley Peter G. Appleby Richard W. Battarbee Tiiu Alliksaar Piero Guilizzoni Erik Jeppesen Atte Korhola Jaan-Mati Punning 《Journal of Paleolimnology》2011,45(4):447-468
Sediment accumulation rate (SAR) is an important physical parameter in all lakes and increases have been observed in many
over the last c.100 years. This has been ascribed to changes in land-use and land-management causing accelerated catchment
soil erosion and an increase in autochthonous organic matter production. The EU Water Framework Directive requires that assessment
of biological, hydromorphological and chemical elements of water quality should be based on the degree to which present day
conditions deviate from those expected in the absence of significant anthropogenic influence, termed reference conditions.
Currently however, the reference condition for sediment accumulation rate for lakes of different types is undefined. To improve
our understanding of the controls on SARs we compiled SAR and lake typology data for 207 European lakes derived from 210Pb dated cores to assess how rates have changed through time (in 25 year classes) both overall and for lakes of different
types. Seventy-one percent of these sediment cores showed surface SARs higher than “basal” (mainly nineteenth century) rates,
11% showed no change while 18% showed a decline. Lakes were then classified into lake-types using four variables: alkalinity
(3 classes), altitude (3 classes), maximum depth (2 classes) and lake area (2 classes). This generated a possible 36 lake
classes of which 25 were represented in the dataset. Nine lake-types contained >10 lakes. Little change in SAR occurred prior
to 1900 and most increases occurred in more recent periods, in particular 1950–1975 and post-1975. This indicates a general
acceleration in SAR in European lakes during the second half of the twentieth century. Reference SARs were estimated for six
lake-types with the highest number of sites. European mountain lakes had the lowest reference SAR (0.005 ± 0.003 g cm−2 yr−1) while lowland, high alkalinity sites had the highest (0.03–0.04 g cm−2 yr−1). SARs for other lake-types ranged between 0.012 and 0.024 g cm−2 yr−1. Using the mountain lake-type as an example, the 1850 reference SAR appears to show good agreement with available data for
lakes beyond Europe indicating these values may be more broadly applicable. Contemporary SARs in lakes of all classes showed
exceedence over their defined reference SAR. This may be partly due to diagenetic processes. Greatest exceedences were found
in shallow, low altitude lakes and these are considered to be the ones under the greatest threat from continued elevation
of SAR. It is considered that climate change may play a progressively more important role in driving SAR in the future. 相似文献
4.
Jaan-Mati?PunningEmail author Tiiu?Koff Ene?Kadastik Annika?Mikom?gi 《Journal of Paleolimnology》2005,34(3):377-390
The main aim of this study was to reconstruct the history of water level fluctuations of a small dimictic lake during the Holocene based on the lithological and geochemical composition of sediments. We studied lithological and geochemical parameters in sediment cores extracted along a transect through Lake Juusa in southeastern Estonia. Analysis revealed that LOI550 and CaCO3 content in the accumulated sediment are dependent on water depth. At depths greater than 3 m, the relationship between organic carbon and CaCO3 is inverse, whereas no relationship exists at shallower depths. Lake-level changes are well depicted on the grain-size distribution profiles and macrofossil composition. An increase in the >‰315μm fraction appeared during the initial phases of water level fluctuations, followed by an increase in the 100–315μm fraction. The >‰36μm fraction dominated the silt fraction. Higher OC/N ratios in shallow water sediments reflect the dominance of macrophytes vegetation. 相似文献
5.
Comprehensive paleobotanical and geochemical methods have been used to study the relationship between the spatial scale of landscape development and values of pollen influx to take the bog sediments. The spatial-temporal history of the four lakes and a bog was established in NE Estonia and pollen analyses of thier sediment were made. It was found that the influx of total arboreal pollen directly corresponds with the sizes of the sites studied, and varies with thier expansion or reduction. 相似文献
6.
To describe and analyse the role of sediments in the matter cycling in large shallow transboundary Lake Peipsi (L. Peipsi)
in north-eastern Europe, detailed surface-sediment mapping was conducted. On the basis of grain size the surface sediments
fall into three groups: coarse-grained sediments (prevailingly sands in the lake’s southern part), fine-grained sediments
(mainly silts) and silty sands, both in the central deeper part within the 8-m depth contour. The groups of deposits have
a distinct spatial distribution, determined mainly by the current system in the lake. The main source of bottom sediments
is the erosion of the lake floor and shores, the role of the river input seems to be limited. Fine-grained organic-rich sediments
are very cohesive, playing the main role in the circulation of various inorganic and organic pollutants like nutrients and
xenobiotics. Due to the cohesive character of the sediments their physical and chemical properties are extremely diverse and
if the near-bottom shear stress increases (extreme meteorological events, changes in the water level, etc.), the lake floor
may be subjected to episodic erosion and resuspension, which may cause remobilisation of impurities in muddy sediments and
their return to the food chain. 相似文献
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