Institute of Geology and Geography of Nature Research Center
Institute of Geology and Geography of Nature Research Center
Motuza G.,Vilnius University |
Sliaupa S.,Institute of Geology and Geography of Nature Research Center
Journal of Asian Earth Sciences | Year: 2017
A volcanic-sedimentary succession of Paleogene age is exposed in isolated patches at the southern margin of the Tajik block in the Ghor province of Central Afghanistan. The volcanic rocks range from basalts and andesites to dacites, including adakites. They are intercalated with sedimentary rocks deposited in shallow marine environments, dated biostratigraphically as Paleocene-Eocene. This age corresponds to the age of the Asyābēd andesites located in the western Ghor province estimated by the 40Ar/39Ar method as 54 Ma. The magmatism post-dates the Cimmerian collision between the Tajik block (including the Band-e-Bayan block) and the Farah Rod block located to the south. While the investigated volcanic rocks apparently bear geochemical signatures typical to an active continental margin environment, it is presumed that the magmatism was related to rifting processes most likely initiated by far-field tectonics caused by the terminal collision of the Indian plate with Eurasia (Najman et al., 2017). This event led to the dextral movement of the Farah Rod block, particularly along Hari Rod (Herat) fault system, resulting in the development of a transtensional regime in the proximal southern margin of the Tajik block and giving rise to a rift basin where marine sediments were interbedded with pillow lavas intruded by sheeted dyke series. © 2017 Elsevier Ltd
Gaigalas A.,Vilnius University |
Pazdur A.,Silesian University of Technology |
Michczynski A.,Silesian University of Technology |
Pawlyta J.,Silesian University of Technology |
And 5 more authors.
Geochronometria | Year: 2012
Abundant wood remains and buried trees have been found in the western part of Lithuania near Zakeliškiai and Lyduvenai on Dubysa River (a tributary of Nemunas River) where deposits are rich in organic remnants and buried soils. In Zakeliškiai and Skiručiai sections of Dubysa River oxbow sediments were investigated by various methods (dendrochronological, carbonate, granulometric, pollen and mollusc fauna analysis). In addition, these sections were dated using the radiocarbon method. Samples were collected from deposits of Dubysa River outcrops. The studied oxbow lakes have existed for more than 5 thousand years (from ca. 4300 BC to 1000 AD). During this period organic rich deposits with trees and branches were formed in the oxbow lake. This indicates that at the end of Atlantic, during Subboreal and in the early Subatlantic periods there was a forest growing that contained mainly oaks which were falling down into an oxbow lake and later were covered by sandy and silty deposits. The granulometry of alluvial deposits, as well as the mixture of medium-grained sand and silt show different stages of Dubysa River palaeochannel formation: riverbed and oxbow lakes. Three climate warming cycles were revealed according to carbonate analysis data in all investigated sections. The rheophile thermophilous Holocene age molluscs species Bithynia tentaculata L., Unio cf. crassus Philipsson, Pisidium amnicum (Müller), Theodoxus fluviatilis (Linnaeus) have been found. The pollen composition and sequences have been divided into five local pollen assemblage zones (LPAZ) and described according to pollen spectra in each zone. In this way it is possible restore palaeoclimatic coherent evolution, trends and cyclical change. © 2012 Versita Warsaw and Springer-Verlag Wien.
Veteikis D.,Vilnius University |
Sabanovas S.,Vilnius University |
Jankauskaite M.,Institute of Geology and Geography of Nature Research Center
Baltica | Year: 2011
This paper addresses changes of landscape structure, mainly by analyzing land use, in the Lithuanian coastal plain. The study marks the changes in the region's land use, which changed in this period because the coastal area became free from the strictly militarized State border limitations that existed during the Soviet period. The main source of data for the investigation are aerial photographs of three dates - 1998, 2005, and 2009, at a scale of 1:10 000. Digitalization of the aerial photographs and data overlay were the main methods for obtaining findings on changes of the landscape structure. The results of the cartographic and statistical analysis reveal two different patterns of land use change, namely before and after 2005. Despite the high tension created by various economic activities, the region experiences forestation processes in its land use structure due to the emergence of abandoned lands, especially those that were clear between 1998 and 2005. One further aspect of landscape change that is noted is the extent of deforestation, characteristic for the period between 2005 and 2009. Being unique to Lithuania, the narrow and short strip of the coastal sea landscape requires much attention for natural protection, but on the other hand, is lacking proper care in some places and has been abandoned. The author's data and findings on land use changes in the coastal region can be used as an additional aid for planners and decision-makers.
Sliaupa S.,Institute of Geology and Geography of Nature Research Center |
Sliaupa S.,Vilnius University
Journal of Vibroengineering | Year: 2013
The Baltic region is characterised by a low seismic activity. The recent Kaliningrad earthquake of magnitude M = 5.0 in 2004 persuades that the previous estimates of the seismic hazard of the Baltic region were underrated. It urges the re-assessment of characteristics of the maximum possible earthquake that may take place elsewhere in the Baltic region. The Kaliningrad earthquake scenario was modelled for Vilnius city area. It is motivated by occurrence of several moderate historical earthquakes that took place close to the city, also the presence of some largescale fault zones in proximity to the city. The maximum probable earthquake of magnitude M = 5.0 and hypocentral depth of 15 km was modelled to take place in Vilnius city area. The modelled seismic response spectra are dominated by low frequencies 2-5 Hz that is accounted to soft soil effect. The peak ground acceleration (PGA) was modelled to range from 1.05 m/s2 to 1.40 m/s2 depending on soil type, i.e. moraine dominated and sand/technosoil dominated, and on stress-strain relationship (linear vs. non-linear soil behaviour). Estimated PGA corresponds to macroseismic intensity I0 = 7 (MSK-64) implying only minor building damages. The modelled seismic signal implies that 2-10 store buildings are subject to the highest (though modest) seismic risk. © VIBROENGINEERING. JOURNAL OF VIBROENGINEERING. JUNE 2013.