Leili Saarse

Holocene vegetation and land-use history in the environs of Lake Kahala, northern Estonia

Pollen profiles, based cores taken in Lake Kahala and from the adjoining mire, were used to establish general vegetation history and to reconstruct the extent and types of land-use over most of the Holocene. Modern pollen deposition was studied using moss polsters and the results were used in the interpretation of the fossil pollen data in terms of former land-use practices. The modern-day samples are from settlements, hay meadow and pasture, and overgrown pasture. Indications of human activity can be traced back to the Stone Age. At ca. 6400 cal. B.C., the first indications of possible woodland utilisation by humans are recorded. This may have involved grazing within the forests. From 4200 cal. B.C. onwards, animal husbandry with changing intensity was practised. Arable farming, involving cereals, was introduced to the area at ca. 1800 cal. B.C., but it was only at ca. 500 cal. B.C. that it assumed an important role in the farming economy.Secale cereale (rye) was introduced during the Roman Iron Age, intensive rye cultivation started at the end of the Iron Age, at ca. cal. A.D. 800. Ever increasing farming pressures triggered the formation of openalvars. Open landscape similar to that of today has persisted, with minor forest regeneration phases, since at least 500 cal. B.C.

Palaeogeographic Model for the SW Estonian Coastal Zone of the Baltic Sea

The authors combined geological, geodetic and archaeological shore displacement evidence to create a temporal and spatial water-level change model for the SW Estonian coast of the Baltic Sea since 13,300 cal. years BP. The Baltic Sea shoreline database for Estonian territory was used for the modelling work and contained about 1,200 sites from the Baltic Ice Lake, Ancylus Lake and Littorina Sea stages. This database was combined with a shore displacement curve from the Parnu area (in SW Estonia) and with geodetic relative sea-level data for the last century. The curve was reconstructed on the basis of palaeocoastline elevations and radiocarbon-dated peat and soil sequences and ecofacts from archaeological sites recording three regressive phases of the past Baltic Sea, interrupted by Ancylus Lake and Littorina Sea transgressions with magnitudes of 12 and 10 m, respectively. A water-level change model was applied together with a digital terrain model in order to reconstruct coastline change in the region and to examine the relationships between coastline change and displacement of the Stone Age human settlements that moved in connection with transgressions and regressions on the shifting coastline of the Baltic Sea.

A 700-year decadal scale record of lake response to catchment land use from annually laminated lake sediments in southern Estonia

Lakes, particularly those in fertile soils may have been anthropogenically influenced over long timescales for hundreds to thousands o f years by agricultural activities and may have become more productive and/or disturbed (BERGLUND 1991). Human impact on these landscapes, starting with the development of primitive agriculture, followed by forest clearance and more advanced land-use practices, has affected the lakes through various catchment processes. In this way human-induced nutrient enrichment has caused major problems to aquatic ecosystems. Paleolimnological investigations o f lake sediment cores can be used to document the history of land-use activities and related effects on lake water quality (FRITZ 1989). Varve chronology based on annually deposited lake sediments yields a continuous high-resolution temporal record and allows absolute dating of the sediment sequence. Furthermore, aquatic sub-fossils preserved in varved sediments provide precise data for reconstructing past trophic changes in lakes, whereas pollen evidence allows tracking of prehistoric human impact on vegetation in the lakes catchment area. The aim ofthe present study was to follow the impact of agriculture on water quality in Lake Rõuge Tõugjãrv, southem Estonia using high-resolution proxies ( diatoms, pollen, Cladocera, loss-on-ignition) from varved sediment during the past 700 years.

A high-resolution spectroscopic study of pore-water dissolved organic matter in annually laminated lake sediments: a new tool for reconstructing eutrophication history

Spectroscopic methods have been used widely in studies of dissolved organic matter (DOM) in a Iarge variety of water bodies (ZUMSTEIN & BVFFLE 1989, KOWALCZUK et al. 2003) and marine sediments (DEFLANDRE & ÜAGNÉ 2001, S!ERRA et al. 2001). These methods allow predicting quantities as well as revealing qualitative properties of DOM. The main merits of the methods are (l) simplicity, (2) small sample volume required for analyses and (3) no need for chemical pretreatment of samples. In the present research, spectroscopic methods were employed to detect changes in characteristics of pore-water DOM (pwDOM) in lake sediments. Fluorescence an d absorption spectra were analysed to examine conformity of spectral indicators with the paleolimnological proxies. A lake with annually laminated sediments was chosen, which allowed dating sediments with high accuracy and tracking temporal variations o f paleoindicators in high-resolution scale.

The Physical and Social Effects of the Kaali Meteorite Impact — a Review

There is a concern that the world we know today will end in a global ecological disaster and mass extinction of species caused by a meteorite impact (Chapman and Morrison 1994; Chapman 2004). We are aware that rare large impacts have changed the face of our planet as reflected by extinctions at the Permian/Triassic (∼251 Ma; Becker et al. 2001), Triassic/Jurassic (∼200 Ma; Olsen et al. 2002) and Cretaceous/Tertiary (∼65 Ma; Alvarez et al. 1980) boundaries. Today astronomers can detect and predict the orbits of the asteroids/comets that can cause similar impacts. Yet, Tunguska, Meteor Crater-size and smaller meteorites that could cause local disasters are unforeseeable. However, while planning to avoid the next bombardment by cosmic bodies we can look at past interactions of human societies, environment and meteorite impacts to understand to what extent human cultures were influenced by meteorite impacts. The question is whether the past examples are relevant in the modern situation, but they are certainly useful. The Kaali crater field in Estonia, in that respect, is an excellent case study area for past human-meteorite interactions. Moreover, Kaali is not the only Holocene crater field in this region: in fact, during the last 10 000 years Estonia has been targeted at least by four crater forming impacts and there are five registered meteorite falls (Fig. 15.1). The two large craters, Neugrund and Kardla, originate from 535 and 455 Ma, respectively (Suuroja and Suuroja 2000). cr]

Classification of lake basins and lacustrine deposits of Estonia

Based on extensive data from a long-term investigation, a new genetic classification of lake basins is proposed for Estonia. Eight lake groups are distinguished, tectonic-denudation, glacial, chemical, fluvial, coastal (neotectonic), telmatogenic, cosmogenic and artificial, containing 13 subgroups and 19 basin types. Also proposed is a new lithological classification of Estonias organic and calcareous lake sediments, based on analyses of more than 2000 sediment samples from 90 contemporary and 50 late-glacial (extinct) lakes. Of the ca. 1150 Estonian lake basins that formed on mineral substrate, the two largest basins are of preglacial, tectonic-denudation origin, later modified by glaciers. Eight hundred lakes are of glacial origin, and 300 of other origins in the Holocene. In addition, ca 20 000 bog pools formed on peat in the Holocene. Only minerogenous sedimentation occurred in the lakes in the late-glacial period. After that, organic (gyttjas) and/or calcareous sediments have formed. Azonal factors have been largely responsible for the wide variation in Estonias lacustrine deposits.

Palaeoreconstruction of the Baltic Ice Lake in the Eastern Baltic

A GIS-based palaeogeographic reconstruction of the development of the Baltic Ice Lake (BIL) in the eastern Baltic during the deglaciation of the Scandinavian Ice Sheet is presented. A Late Glacial shoreline database containing sites from Finland, NW Russia, Estonia, Latvia and modern digital terrain models was used for palaeoreconstructions. The study shows that at about 13,300 cal. years BP the BIL extended to the ice-free areas of Latvia, Estonia and NW Russia, represented by the highest shoreline in this region. Reconstructions demonstrate that BIL initially had the same water level as the Glacial Lakes Peipsi and Vortsjarv because these water bodies were connected via strait systems in central and northeast Estonia. These strait systems were gradually closed at about 12,700–11,700 cal. years BP due to isostatic uplift, prior to the final drainage of the BIL. Glacial Lake Vortsjarv isolated from the BIL at about 12,400–12,000 cal. years BP. Exact timing of Glacial Lake Peipsi isolation is not clear, but according to the altitude of the threshold in northeast Estonia and shore displacement data, it was completed at about 12,400–11,700 cal. years BP.

Sea level changes and Neolithic hunter-fisher-gatherers in the centre of Tallinn, southern coast of the Gulf of Finland, Baltic Sea

Relative sea level (RSL) changes and the palaeogeography of a Neolithic hunter-fisher-gatherer settlement site on the former shore of the Gulf of Finland in the city centre of Tallinn were reconstructed by implementing GIS in landscape modelling based on archaeological, sedimentary and shore displacement data. AMS radiocarbon dating of mammal bones from the cultural layer suggests the existence of the hunter-fisher-gatherer settlement around 5.1–4.8 cal. ka BP on a seaward inclining sandy beach of Tallinn palaeo-bay c. 100 m from the Litorina Sea shoreline and at about 2.4 m above the coeval sea level. The shoreline passed the study site at about 5.8 cal. ka BP and retreated towards northeast with an average speed of 13 m per century, while the RSL lowered by c. 2.5 mm annually. Combining radiocarbon dates of terrestrial and marine mammal bones from the Neolithic cultural layer, a marine reservoir effect of 350 14C years for the brackish-water Baltic Sea was calculated. By using high-resolution archaeological data in combination with RSL and other geological proxies, we demonstrate new possibilities to reconstruct the palaeoenvironment of deeply buried coastal settlement sites and to predict a possible continuation of the cultural layer in heavily built-up areas.

Cyclic sedimentation pattern in Lake Veetka, southeast Estonia: a case study

Abstract A sediment core from Lake Veetka, southeast Estonia, 1077 cm in length and covering 10,500 calibrated years, was examined using loss-on-ignition, grain-size distribution and AMS 14C dating to reconstruct depositional dynamics. The studied core, recovered from the northern part of the lake, shows a cyclic pattern of organic and mineral matter concentration with cycle durations of 100-400 years. Cyclicity is displayed better in sediments laid down between 9,200 and 5,600 cal BP. Within two time windows (5,600-5,100 cal BP and from 1,200 cal BP to the present), sediment composition changed drastically on account of a high and fluctuating mineral matter content, obviously driven by different factors. Little Ice Age cooling is characterised by the highest proportion of mineral matter, and the Medieval Warm Period is typified by high organic matter content. The cyclic change of organic and mineral matter has been related to climate dynamics, most likely an alternation of wet and dry conditions, changes in the water level of the lake and differences in bioproduction

Late glacial and early Holocene climate and environmental changes in the eastern Baltic area inferred from sediment C/N ratio

Abstract We assessed the utility of using the sediment total organic carbon/total nitrogen (C/N) ratio as an indicator of paleoclimate changes in the eastern Baltic area during the late glacial and early Holocene. The C/N ratio in sediments from Lake Lielais Svētiņu, eastern Latvia, was compared with other sediment variables that are used as proxies of past climate and environment. Analysis revealed that although the organic matter (OM) content in late glacial sediments was extremely low, the C/N ratio captured information about OM origin, and fluctuations in the ratio tracked climate oscillations. The C/N ratio was significantly positively correlated with pollen-inferred mean summer temperature. Therefore, C/N ratio was lower under colder conditions, indicating a predominantly phytoplankton origin of OM, and was higher during warmer conditions, when there was more vegetation around the lake. A strong positive correlation between C/N ratio and the paleopigment beta carotene suggested that elevated phytoplankton production resulted from higher nutrient availability that was controlled largely by the input of terrestrial OM to the lake during warmer climate episodes. Thus, C/N ratio was a good indicator of paleoclimate changes, at least for the late glacial period, when generally cold conditions prevailed. This study also demonstrates the power of multi-proxy paleolimnological analyses for investigating past environmental changes in lakes and their watersheds.