The problem of a late quaternary landbridge between Britain and Ireland

The question of whether a possible landbridge(s) existed between Britain and Ireland during Devensian (Midlandian) Late-glacial and Holocene time is analysed in the light of new geological and related environmental information. The problem of landbridge definition as a whole and related palaeogeographic reconstruction is reviewed briefly, particularly in relation to present understanding of the mechanisms conditioning sea-level movements and marine inundation of former land areas. A tentative palaeoenvironmental reconstruction is made for the Irish Sea and neighbouring seas from Late-glacial time onwards. Suggestions are put forward for the lack of a long Quaternary sedimentary record in Ireland. From the palaeoenvironmental data, it is concluded that no land links are likely to have existed via routeways across the southern continental shelf or Irish Sea zones. If any landbridge existed, it could only have operated between the north of Ireland and South West Scotland as a discontinuous linkage, formed by temporary islands at levels >?46 m O.D. The timing of its operation, if at all, is placed at ～11,400 to 10,200 ± 200 BP.     

High-resolution correlations between Gotland and Estonia near the base of the Wenlock

The strata of the Ireviken Event can be correlated between Gotland, Sweden and the Viki core on Saaremaa, Estonia, with a high degree of precision. Most of the ten datum planes are found with a precision of better than 0.1 m in the Lower and upper Visby Beds on Gotland and high in the Mustjala Member of the Jaani Formation on Saaremaa. Five of the latest Llandovery–early Wenlock units defined by these datum planes are between c. 0.12 and 1.77 m thick on Gotland and 0.12 and 0.67 m in Estonia. The duration of each was between a few thousand and c. 31 000 years. The stratigraphic resolution achieved in the interval of the Ireviken Event is 10,000 years. Ultimate range ends are lacking within a preceding, slightly longer interval, but the pattern of intermittent presence of some taxa agrees well with an unchanged relative rate of sedimentation. Their coeval presence in different places indicates ecological, regional or more widespread changes.     

The peculiarities of Jewish settlement in Estonia

The development of Jewish settlement in Estonia can be divided into three historical stages: formation of settlement; adaption and integration; and formation of the new, Soviet type of settlement. Jewish settlement can be viewed together with the Estonian settlement system. Populated places of different ranks can be distinguished, depending on the size and functions of the Jewish communities. The functions depend greatly on the existence of ethnic institutions, and their sphere of activities. These institutions can be congregations, schools, cultural societies, etc., whose hinterland is limited to their close surroundings.     

The politics of identity: Ethnicity, minority and nationalism in Soviet Estonia

Identity has become one of the core concepts of political geography. This reflects the wide recognition of a post-structural conception of society and space, as well as the acknowledgement of the political character of identity. The present article focuses on the politics of identity, and discusses the politicized forms of identity as related to the Soviet state building policies and the Estonian spaces of resistance. It will be argued that neither identity nor the political demand in Soviet Estonia can be viewed in isolation from their historical and social contexts. Both Soviet state politics and the Estonian spaces of resistance reflected the prevailing conceptions of past and the contemporary political realities. This article examines those preconceptions of the political and territorial development in Soviet Estonia, and also illustrates the interdependent character of state politics and non-state activism. The first part of the article concentrates on the Soviet state building practices – the use of power, symbols, education – and the second part examines the various forms of non-state activism of Estonians.     

Maps and mapping in Estonia

Estonia may be taken as an example of how cartography has developed in the national languages of the Baltic States. Late in the 17th century the first survey of Estonian and Latvian territories was carried out by the Swedes. Masterpieces of the 18th century and the first half of the 19th century are the Atlas of Livonia by L. A. Mellin and a special map of Livonia by C. G. Rücker. The first maps in Estonian appeared more than one hundred years ago. The short period of independence, 1918–1940, was one of rapid development in cartography, interrupted by occupation of the Baltic States by the USSR. Maps were destroyed or declared secret; use of maps was limited. From the beginning of the 1990s, a rapid renaissance of national cartography began.     

芬兰晕彩斜长石晕彩成因探讨——包裹体及其与晕彩的关系

对芬兰斜长岩中斜长石的宏观和微观观测显示,无晕彩的斜长石包裹体不发育,有晕彩的斜长石发育定向排列的针状包裹体。依据斜长石中包裹体的发育程度,可将包裹体分为两类:密集型包裹体(35～50条/mm)和稀疏型包裹体(25～35条/mm)。发育密集型包裹体的斜长石的晕彩以蓝色为主,发育稀疏型包裹体的斜长石的晕彩以红色或橙红色为主。电子探针、扫描电镜和激光拉曼光谱的分析结果表明,该晕彩斜长石中的所有包裹体在成分上一致,均为磁铁矿,有晕彩的斜长石和无晕彩的斜长石的成分也一致。这表明该斜长岩中的斜长石是否具有晕彩与斜长石的成分、包裹体的成分及斜长石的双晶发育程度无关,而与包裹体的发育程度有关。斜长石和其中定向排列的磁铁矿针状包裹体类似于光学中的光栅效应,斜长石中晕彩的出现可能是光栅衍射和干涉造成的。     

The national atlases of Finland

The first edition of Atlas of Finland was published in 1899, and since then four more editions have appeared, the fifth started in 1977. The two first editions (the second appeared in 1910) were published in order to define the identity of the nation during a time of Russian political opression and a nationalistic awakening. During the same period, in 1901 J. Gebhard published a social-statistical atlas of Finland, likewise a work of scholarly pioneering. The third edition of Atlas of Finland appeared in 1925, here the geographical analysis was much enhanced thanks to the editorial work of J.G. Granö. At this time Finland was still predominately an agrarian state, however, when the forth edition of the Finnish national atlas was published in 1960, the wind of change had set in. Prof. Leo Aario was the leader of this edition, where the deep changes after WW II were documentated,3also the beginning of the rapi d industrialization of the country.The fifth edition is published in separate thematic folios of some 25 pages each. The first folio on Forestry was published in 1977, and so far 4 folios have appeared of a total of 25. In each folio the graphic material and the text are integrated. There will be some 1 500 statistical maps, most of them on the scale of 1:8 mill., about 10 maps on the scale of 1:1 mill. will be included. The editorial work is organized in connection with the National Board of Survey of Finland, which has also the responsibility for the printing and marketing of the atlas. The fifth edition should be finished in 1986. At the same time the work on the next edition should be on its way.     

The silent articulation of private land rights in Soviet Estonia: A geographical perspective

With an explicit focus on the spatial articulation of landownership, this paper explores various ways in which pre-Soviet land rights were expressed in rural Estonia during the Soviet period (1940-1941, 1944-1991). Drawing on cartographical analyses and interviews made in the rural district of Muhu, the paper demonstrates that people who owned land before the Soviet occupation kept track of the officially annulled pre-Soviet land rights, by relating to inertial landscape elements as memory-aids. To local inhabitants the landscape, in which past and present structures always merge, provided substantial evidence in support of the idea of legal continuity of pre-Soviet land rights. Hence, the post-Soviet land restitution reform often implied a re-discovery or re-expression of property rights that had been silenced, but not lost.     

The mantled gneiss domes of Kuopio (Finland): Interfering diapirs

Finite strain data from the Kuopio mantled gneiss domes are described. Synclines located between two domes have flattening-type strains while those situated between more than two domes exhibit constrictional strains. Cleavage trajectory patterns show that cleavage tends to parallel the dome boundaries and encloses characteristic points termed “cleavage triple points”, at junctions of synclines. The stretching lineation is generally steeply plunging in a mean southwest direction. Folds range from inclined to reclined. Their asymmetry is apparently related to irregularities in the cover-basement boundary. Two shear components of the deformation have been deduced from available data. The major one is steeply plunging and is well exhibited by cleavage fans, steeply plunging lineations and finite-strain gradients. The second shear component is horizontal, as deduced from asymmetric folds and other small-scale structures, and is controlled by bosses and dimples in the cover-basement boundaries.The described structural features are explained in terms of interference between progressively inflating neighbouring diapirs. Furthermore, some of these features, such as cleavage triple points, flattening between two domes and constriction between three or more domes, and horizontal shear components controlled by cover-basement boundary irregularities, could be used as criteria of diapirism. A model of progressive dome interference is presented in which each dome inflates and interacts with neighbours. Such a model could possibly be applied to other orogenic situations with closely spaced diapirs, e.g., Archean greenstone belts or granite-rich orogenic belts.     

峒室围岩松动圈震波探测技术与应用

简要介绍了利用地震波进行巷道围岩松动圈测试与解析的原理和方法技术。通过在煤矿巷道松动圈震波测试的应用实例,说明了单孔检层与跨孔CT方法是一种有效的围岩松动圈测试方法。     

Physical geography in Estonia: Bridging western and eastern schools of landscape synthesis

This paper is an overview of principal investigations in the complex physical geography of Estonia. The focus is on landscape and regional studies, rather than geomorphology or hydrology.Academic geography in Estonia developed in the context of geographic exploration. In the 19th century a leading role among Russian explorers was played by the Baltic Germans Krusenstern, Bellingshausen, Middendorff, Wrangel, and others. After Estonia gained independence in 1919, well-known geographers from Northern (Granö) and Central (Haltenberger) Europe helped to develop landscape studies, which, led by Tammekann, Markus, and Kant, reached a considerable level of excellence by the 1930s. Due to the mass flight of intellectuals to the West during the 1940s, geography in particular sustained heavy losses. A network of state institutes was established when Estonia became an SSR. Even though geography was not among them, some of the institutes did deal with such spatial issues as natural resources and nature protection. During the seventies there was a broadening of research frontiers in physical geography. Various directions were developed in landscape morphology, geochemistry, geophysics, and ecology, parallel to similar developments in the USSR. Today activities are dominated by international cooperation among specialists from the Baltic Sea countries. Investigations have strong interdisciplinary character.     

Comparison between radiocarbon and varve dating in Lake Lampellonjärvi, south Finland

The annual nature of organic laminations in the sediment from a small lake, Lampellonjärvi (61°04'N; 25°04'E), was determined. The core was obtained using an in situ freezing method and the laminations were checked by a detailed microscopical analysis of adhesive tape preparations. A series of six radiocarbon dates were obtained for levels in the core which had previously been dated by means of varve counts to ages between A.D. 182 and AD. 1513. The radiocarbon dates were between 547 and 1525 years older. Two additional ¹⁴C dates from the lower part of the same profile (ca. 1880 B.C. and ca. 3100 B.C.), however, gave expected results. Erosion of old organic terrestrial material due to agricultural activity in the surroundings of the lake was assumed to have been the cause of abnormally old radiocarbon ages. Dates from the pre-agricultural period had a deviation from varve years similar to the difference between tree rings, historical documents and radiocarbon dating recorded in other studies.     

Geochemical Atlas of Finland: preliminary aspects

During 1984 and 1985, the Geological Survey of Finland carried out regional geochemical mapping of till, at a scale of 1:2,000,000, as part of a programme to produce data for the first Geochemical Atlas of Finland. The Atlas is designed to give comprehensive background information on the distribution of elements in rocks, soils, and the surficial environment.     

The 2003 earthquake swarm in Anjalankoski, south-eastern Finland

During May 2003 a swarm of 16 earthquakes (M_L = 0.6–2.1) occurred at Anjalankoski, south-eastern Finland. The activity lasted for three weeks, but additional two events were observed at the same location in October 2004. A comparison of the waveforms indicated that the source mechanisms and the hypocentres of the events were nearly identical.A relative earthquake location method was applied to better define the geometry of the cluster and to identify the fault plane associated with the earthquakes. The relocated earthquakes aligned along an ENE–WSW trending zone, with a lateral extent of about 1.0 km by 0.8 km. The relative location and the waveform-modelling of depth sensitive surface wave (Rg) and S-to-P converted body wave (sP) phases indicated that the events were unusually shallow, most likely occurring within the first 2 km of the surface. The revised historical earthquake data confirm that shallow swarm-type seismicity is characteristic to the area.The focal mechanism obtained as a composite solution of the five strongest events corresponds to dip-slip motion along a nearly vertical fault plane (strike = 250°, dip = 80°, rake = 90°). The dip and strike of this nodal plane as well as the relocated hypocentres coincide with an internal intrusion boundary of the Vyborg rapakivi batholith.The events occur under a compressive local stress field, which is explained by large gravitational potential energy differences and ridge-push forces. Pore-pressure changes caused by intrusion of ground water and/or radon gas into the fracture zones are suggested to govern the swarm-type earthquake activity.     

Relationships between geochemistry of basal till and chemistry of surface soil at forested sites in Finland

Concentrations of several elements extractable with BaCl₂ and acid ammonium acetate (pH 4.65) were measured in the organic and 4 mineral soil layers on the national forest inventory plots of the Finnish Forest Research Institute. The soil data also includes total concentrations of elements in the organic layer and site and soil physical characteristics. Data were compared with the aqua regia extractable element concentrations measured in the nationwide regional till geochemical mapping carried out by the Geological Survey of Finland.Correlations between concentrations in surface soil and underlying basal till were generally highest for K, Mg, Mn, P and Zn; in the organic layer and till they were highest for Cr and Cu. The strength of these correlations did not increase regularly from surface to deeper soil layers. All soil base cations with the exception of Ca, which is of relatively low solubility, were well correlated. The elements Zn, K, P, Al and Mn in till were the most reliable indicators of surface soil chemistry.Fuzzy clustering showed that the correlation between element concentrations in basal till and the two uppermost layers of mineral soil was better within areas of distinct till geochemistry, such as the schist belts in southwestern Finland, the Lake Ladoga–Bothnian Bay zone and the Kuusamo schist belt.Surface soil chemical variables were clearly better in discriminating fertility classes of forest sites than were element concentrations in basal till. The independent ability of till geochemistry to distinguish these productivity classes and to explain surface soil fertility was nevertheless demonstrated.     

Geochemical mapping and databases in Finland

Regional geochemical maps in Finland have been produced from many different programmes. The scale of sampling, the material collected and the analytical methods used varied according to the aim of the study. The entire country was covered at a reconnaissance scale using glacial till, groundwater, surface water and organic stream sediments as sampling media. Glacial till was sampled throughout the country at a regional scale. Local scale mapping and detailed geochemical studies are carried out in selected areas. The main analytical methods have been ICP-AES and ICP-MS, but other methods were used when necessary. In assaying solid material, both total decomposition and strong acid (aqua regia) leaching were used. The results are stored in ALKEMIA, a database developed in the geochemistry department of the Geological Survey of Finland. The data are available as tabulated ASCII files and as digital image files on diskettes, or as various types of symbol and colour maps from desired areas or map sheets. Two examples of the application of geochemical mapping data in prospecting and in environmental research are presented. Indications of the presence of gold and multiple-sulphide ore deposits have been the most useful results obtained from a prospecting standpoint. On the environmental side, reconnaissance scale geochemical mapping data gave more reliable information on the base cation concentration than bedrock maps, making them particularly valuable in devising an acidification assessment model.     

Magnetotelluric and audiomagnetotelluric measurements in Finland

Joint Finnish—Hungarian MT (magnetotelluric) and AMT (audiomagnetotelluric) measurements were carried out in Finland in the framework of the international ELAS project. The conditions for MT measurements are favorable at these latitudes. Five MT and 150 AMT stations gave information on the electrical conductivity distribution in the area: AMT results guided the choice of MT sites with minimal near-surface distortion effects and helped the interpretation of the MT soundings; the MT measurements indicate the presence of large conductivity anomalies and can be best interpreted as lateral induction effects of near-surface dyke structures. This result is confirmed by a certain correspondence between the directions of the maximum impedances and of the tectonic zones of the area.Any information about the upper mantle would require the use of S_q harmonics because of the crustal conductivity anomalies detected by the MT measurements.