Wyniki wyszukiwania - BazTech

1

Geochronology and Palaeomagnetic Records of the Snaigupėlė Section in South Lithuania

Baltrūnas V., Maksimov F. E., Kuznetsov F. Y., Karmaza B., Katinas V.

Geochronometria

|

2015

|

Vol. 42, no.1

172--181

EN

The interglacial deposits in the South Lithuanian Snaigupėlė outcrop and borehole Snaigupėlė-705 are marked for different bedding conditions though the sections are in proximity of each other. In the borehole section, the interglacial deposits are thicker and bedding at a greater depth than the analogous deposits of the outcrop. In the Snaigupėlė outcrop, the highest compatibility of isochronic-correction dates, calculated using L/L (method of leaching) and TSD (method of total sample dissolution) models, was determined for combination of three samples. With the help of the f value (section of isochrones in the axis of ordinates), the contribution of the primary pollution with thorium was determined where, as based on corrected analytical data, isochronic-correction dating was performed: 18 14 127+ − ka years for the L/L model and 22 16 132+ − ka for the TSD model. Palaeomagnetic investigations showed that the section of lacustrine sediments in the lower part of Snaigupėlė outcrop were orientated by reversed magnetic excursion and in the upper part by normal magnetic polarity. Collation of the obtained data with the global geomagnetic scale showed that the palaeomagnetic inversion observed in the Snaigupėlė section was related with the Blake Event in the Eemian Interglacial.

2

The earliest Pleistocene interglacials in Lithuania in the context of global environmental changes

Baltrūnas V., Zinkutė R., Šeirienė V., Katinas V., Karmaza B., Kisielienė D., Stakėnienė R., Pukelytė V.

Geological Quarterly

|

2014

|

Vol. 58, No. 1

145--162

EN

Investigations have been carried out in order to reconstruct the palaeoenvironmental changes during the earliest Pleistocene interglacials and to establish their relation to global environmental changes. Three sections in east Lithuania exposing the earliest Pleistocene lacustrine deposits lying between the Kalviai (Glacial B, Nidanian?) and Dzūkija (Sanian 1) and between Dzūkija (Sanian 1) and Dainava (Sanian 2) glacial deposits were selected for study. Until now the Šlavė-2 and Vindžiūnai-136 successions were considered to have formed during the Vindžiūnai (Augustovian?, Malopolanian) Interglacial and the Kudrė-915 succession during the Turgeliai (Cromerian IV, Ferdynandovian) Interglacial. Geochemical, palaeomagnetic, magnetic susceptibility, anisotropy of magnetic susceptibility and palaeobotanical proxies were applied to establish the cyclicity and dynamics of palaeoenvironmental change. The data obtained enable the subdivision of the section into units related to changes in the sedimentary environment. The Matuyama/Brunhes boundary and Jaramillo subchron of the Matuyama chron have been recognized in the Šlavė section. The results enable correction of the stratigraphic position of the sections studied. The sedimentation in the Šlavė section took place during the Early Pleistocene, while that at the Vindžiūnai-136 and Kudrė-915 took place during two different Middle Pleistocene interglacials.

3

Sedimentary environment changes during the Early-Middle Pleistocene transition as recorded by the Daumantai sections in Lithuania

Baltrūnas V., Zinkutė R., Katinas V., Karmaza B., Šeirienė V., Kisielienė D., Taraškevičius R., Lagunavičienė L.

Geological Quarterly

|

2013

|

Vol. 57, No. 1

45–-60

EN

Two sections (Daumantai-1 and Daumantai-3) in East Lithuania expose Early-Middle Pleistocene lacustrine-alluvial, deposits which lie on a thin Neogene layer and on older Devonian rocks. They are overlain by glacigenic deposits. Geochemical, palaeomagnetic, magnetic susceptibility, plant macrofossil, and diatom investigations were performed to determine the changes in the sedimentary environment. Cluster analysis of the geochemical variables (10 major elements, 16 trace elements, total organic and inorganic carbon) revealed the element groups and factors. The lowermost units are characterized by a major influence of local material and significant fluctuations in heavy mineral content. These fluctuations might reflect short-term climate changes. The transitional units have more expressed trends, especially as regards the trace elements and Zr/Ti. The uppermost units are characterized by a slight influence of local material and small fluctuations in trace elements. The data analysed enable the subdivision of the section into units related to changes in sedimentary environment. The boundary of the Bruhnes/Matuyama reversal in the Daumantai-1 and Daumantai-3 sections was detected by palaeomagnetic studies and enables the stratigraphical correlation of these deposits.

4

Entropy of Pleistocene till composition as an indicator of sedimentation conditions in Southern Lithuania

Baltrūnas V., Gaigalas A.

Geological Quarterly

|

2004

|

Vol. 48, No 2

115--122

EN

The two most complete and stratigraphically most reliably identified Pleistocene sections in Southern Lithuania were chosen as the object of this study. Variations in relative entropy were assessed from the average data on the grain size,mineral and petrographic composition of the individual stratigraphically identified till beds. Data obtained in the current study showed that the relative entropy of till composition, which characterises the even distribution of the components according to relative parameters (such as the fraction intervals and, the number of minerals), indicates that the till composition was modified by matter dispersion (mixing) and condensation (concentration). The relative entropy of the content of different till components (grain size fractions, heavy and light minerals, petrographic groups) in glacial units of various ages is different and indicates different parameters of glacial dynamics and different routes of glacier movement. Also, the relative entropy of till composition in the direction of glacier movement shows repetitive patterns, which are predetermined by loading of the bottom layers of the glacier with till material up to its maximum concentration, followed by their settling. Ice loading with till material proceeds by grinding and mixing the transit and indigenous exarational material until the till mixture reaches its maximum density (volumetric weight) and becomes close to the optimum mixture.