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Zuzevicius A.,Institute of Geology and Geography
Baltica | Year: 2010

The reconstruction of hydrogeological conditions during the Late Pleistocene and Holocene has been performed for the southern part of the Baltic Artesian Basin (BAB) situated on the slope of the Belarusian- Masurian crystalline basement. The reconstruction was accomplished modelling the freezing-and-thawing of the subsurface and migration of unfrozen water under the permafrost, which covered the whole 250-270 m thick fresh water zone before the Nemunas (Late Weichselian) glacier advance (22 000-23 000 BP). Due to anomalous high gradients (0.003-0.004) caused by glacier loading (in the north) and draining periglacial lake (in the south), the unfrozen mineralised water could fill a 10-35 km wide strip in the lower beds of the sedimentary cover at the BAB's southern margin. This can explain the current small thickness of the fresh water zone, as well as the older age of water in deeper beds and water mineralisation in the southern part of the BAB as compared to the northern part of the basin, which is in a similar geological setting.

Gelumbauskaite L.Z.,Institute of Geology and Geography
Baltica | Year: 2010

A study is focused on the Palaeo-Nemunas delta morphogenesis and development during Late Glacial and Holocene time span. Geomorphometry and morphological features of the submerged delta were recognized for the first time on the submarine Curonian (Kuršiu{ogonek}) Plateau in 1986-1992. This paper presents a pilot study applied in 2006-2008 and is based on multi-beam echo sounder and side-scan sonar images data. Two geological sections across the Palaeo-Nemunas delta are compiled from the data of core studies. Geomorphologic, sedimentological, biostratigraphical and radiocarbon AMS 14C and IR-OSL analyses suggest that Palaeo-Nemunas delta begun to develop in the palaeotopography of this area during Preboreal time and ended at the second half of Boreal. The basal residual level of the Ancylus (A2) regression phase was identified in the delta trunks at a depth of 41.3-39.9 m and dated 9.31-8.87 ka BP (8300-8000 14C kyr BP). This residual layer is overlapped by marine depositional Litorina (L1 -2 -3)--Post-Litorina complexes up 2 m thick and supported by 7.40±0.5 ka BP; 6.80±0.5 ka BP (IR-OSL, RLQG 1881-118, 1882-118); 6.87±45 ka BP (6030±2514C kyr BP); 4.66±110 ka BP (4100±25 14C kyr BP, UGAMS #03138, 03139).

Grigelis A.,Institute of Geology and Geography
Baltica | Year: 2011

Knowledge of bedrock geology of the Central Baltic Sea (CBS) developed gradually in the last decades of the 20th century. In this period, a deep seismic survey, tectonic analysis ranging over an internal structure of entrails and followed hydrocarbon prospective drilling was performed in the eastern segment of CBS. The geological systems have been subdivided into series and regional stages. At the same time marine expeditions made key point to recent sedimentation and geodynamic processes. After the 1990s international and EU-supported geological-geophysical projects were successfully performed in many aspects of the Baltic marine geology. These data enlightened the Baltic Sea history, development, present status and were used as a basis for 1:500 000 or 1:200 000, versus 1:50 000, mapping. The paper aims to present a historical viewpoint to enlighten the methodology and innovations and to evaluate the exploration of bedrock geology of the CBS as is reflected on existing regional geological maps.

Bogdanova S.,Lund University | Gorbatschev R.,Lund University | Skridlaite G.,Institute of Geology and Geography | Soesoo A.,Tallinn University of Technology | And 2 more authors.
Precambrian Research | Year: 2015

A comparative study of the central and southern parts of the Palaeoproterozoic Svecofennian orogen in the Baltic/Fennoscandian Shield and the platform area to the east and south of the Baltic Sea indicates that at least these parts of the orogen are built up of several NW-SE trending, 100-300. km wide tectonic megadomains separated from each other and complicated by major zones of mostly dextral shearing. The generation of these zones occurred successively between 1.86 and 1.75. Ga, concomitantly with continuing crustal accretion younging towards the southwest. Even considering the distorting presence of a number of microcontinents, this indicates the one-time existence and repeated episodic activity of a master subduction zone stepwise falling back to the present south-southwest. At 1.82-1.80. Ga, the oblique collision of protocontinents Volgo-Sarmatia and Fennoscandia interfered with the accretionary growth of the crust in the Svecofennian orogen. In the west, the system of Svecofennian tectonic domains and shear zones is delimited by 1.70-1.55. Ga orogenic belts marking the Laurentia-Greenland-Baltica margin of Columbia. Altogether, the available U-Pb zircon datings and studies of key rocks and structures in the South Baltic region allow more detailed Trans-Baltic correlation and the creation of new integrated models of the structural and tectonic evolution of the Svecofennian orogen in particular and northern Europe in general. The new findings will be important also in the continuing study of supercontinent formation and supercontinent cycles, and the drifting of Palaeoproterozoic protocontinents during the assembly of Columbia/Nuna. © 2014 Elsevier B.V.

Skridlaite G.,Institute of Geology and Geography | Bogdanova S.,Lund University | Taran L.,Belarussian Research Geological Exploration Institute | Baginski B.,University of Warsaw
Gondwana Research | Year: 2014

The Palaeoproterozoic lower crust, forming several belts and domains, is a major component of the crystalline basement within the large region to the southeast of the Baltic Sea in Belarus, Lithuania and Poland. Four stages of high grade metamorphism have been determined in the Western Lithuanian Granulite domain (WLG) and Belarus-Podlasie Granulite belt (BPG), the western East European Craton (EEC). We have carried out P-T studies, secondary ion mass-spectrometry (SIMS) zircon- and electron probe (EPMA) - monazite dating of peak metamorphism. The first stage occurred at 1.81-1.79. Ga under 800-900. °C and 8-10. kbar and was related to both accretionary and postcollisional tectonics in the South Baltic region, whereas the stages at 1.73-1.68. Ga (700-800. °C, 6-7. kbar), 1.62-1.58. Ga (700. °C, 4-5. kbar), and 1.52-1.50. Ga (900. °C, c. 10. kbar) can be attributed to extensional intracratonic regimes. The 1.81-1.79. Ga stage was connected both to the major Sarmatia-Fennoscandia collision and the eastward accretion, which led to the formation of Baltica (East-European Craton) during the assembly of the Columbia (Nuna) supercontinent. The later high grade events associated with intracratonic extensions and magmatism may be distal manifestations of accretionary processes along the long-lived common Laurentia-Baltica margin. The 1.52-1.50. Ga metamorphism was associated with extensive anorthosite-mangerite-charnockite-granite magmatism in already consolidated crust. © 2013 International Association for Gondwana Research.

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