Santrauka The Paleocene Yamna Formation represents one of the main oil-bearing sequences in the Ukrainian part of the Carpathian petroleum province. Major oil accumulations occur in the Boryslav-Pokuttya and Skyba Units of the Ukrainian Carpathians. In the great part of the study area, the Yamna Formation is made up of thick turbiditic sandstone layers functioning as reservoir rocks for oil and gas. The reconstructions of depositional environments of the Paleocene flysch deposits performed based on well log data, lithological and petrographic investigations showed that the terrigenous material was supplied into the sedimentary basin from two sources. One of them was located in the northwest of the study area and was characterized by the predominance of coarse-grained sandy sediments. Debris coming from the source located in its central part showed the predominance of clay muds and fine-grained psammitic material. The peculiarities of the terrigenous material distribution in the Paleocene sequence allowed singling out four areas with the maximum development (> 50% of the total section) of sandstones, siltstones and mudstones. The performed petrographic investigations and the estimation of reservoir properties of the Yamna Formation rocks in these four areas allowed establishing priority directions of further exploration works for hydrocarbons in the study territory.
Raktažodžiai Carpathians; Skyba and Boryslav-Pokuttya Units; Yamna Formation; reservoir rocks; oil and gas prospective areas
Numerous granitic intrusions occur along the southern margin of the Tajik Block and the Band-e-Bayan Zone in the Ghor Province of Central Afghanistan. Previously, they used to be linked to the Cimmerian igneous episodes of Triassic and Cretaceous ages. However, the new U-Pb dating has revealed that these granite intrusions occurred during the Eocene within a narrow time span of 41–36 Ma. They are related to the number of local depressions filled with the volcanic-sedimentary sequence of the same age. These data indicate an intense short-termed magmatic event that affected the region in the Palaeogene. The magmatism might be related to the India-Eurasia collision, which started approximately at the same time. It is likely to have induced the horizontal displacement of crustal blocks westwards along the Hari Rod fault.
Raktažodžiai Tadjik block; granite; isotopic dating; geochemistry; escape tectonics
Santrauka There is little known of the basic parameters of the Lower Silurian graptolitic black shales that are considered the most prospective unconventional gas reservoir in west Lithuania, situated in the deep central part of the Baltic sedimentary basin. Hundreds of deep oil exploration wells have been drilled in the area of interest, owing to extensive exploration of oil fields. The lower and middle Llandovery interval was mainly drilled with coring, while most of the section was covered by only logging. Therefore, the knowledge of major parameters of the Lower Silurian shales is rather obscure and is based on scarce rock sample data. The gamma-ray, electrical resistivity and sonic logs were utilised, together with mineralogical studies of rock samples to document vertical and lateral distribution of organic matter. Also, the brittleness index was defined to characterise the whole Lower Silurian section. Some unexpected trends were identified that may redirect exploration strategy in west Lithuania. The combined application of mineralogical studies and well logs indicate a much higher exploitation quality of the Lower Silurian shales than previously believed. A higher organic matter content and brittleness were derived from logging data in the Lower Silurian shales.
Raktažodžiai Baltic basin; sonic; gamma-ray logs; resistivity logs; total organic carbon (TOC); brittleness index
Santrauka Abstract. The LiDAR-based digital elevation models of representative sample areas of morainic uplands of the Last (Weichselian) and pre-Last (Saalian) Glaciations in Lithuania were selected, and the terrain ruggedness index (TRI) and slope angles (SAs) were calculated. Former hypsometric studies of the topography in Lithuania were mainly dealing with the indication of maximum, minimum or average altitudes of relief derived from topographical maps. The SAs and TRI were calculated for the pattern areas (16 × 16 km) and their central smaller parts (5 × 5 km). In order to test how much morphometric parameters are dependent on the size of a sample area, smaller areas (located in the central parts of all five patterns) were analysed in a similar way, calculating SA and TRI values. The same order of the mean values of SAs was determined: the steepest slopes are characteristic of the Tauragnai, Plateliai and Vištytis patterns, and the gentlest slopes of the Varniai and Medininkai patterns. The steepest slopes and the highest TRI were determined for the marginal morainic uplands of the Last (Late Weichselian) Glaciation. The age of the insular Žemaičiai (Samogitian) Upland is under discussions so far. It was proposed by other researchers earlier that the core of the insular Žemaičiai Upland height formed during the Saalian Glaciation and this core is covered by a thin cover of Weichselian deposits. The morphometric parameters display that the highest maturity of the relief is characteristic of the southern slope of the insular Žemaičiai Upland and the Medininkai Upland of the Saalian age. This indicates a likely similar age of both uplands.
Raktažodžiai digital elevation models; terrain ruggedness index; slope angles; maturity of relief; Weichselian; Saalian
The paper summarizes the evidence of litho-, biostratigraphy and 14C dating of sedimentary sequences studied in natural outcrops and bottom deposits in small lakes, as well as data on coastal morphology in the depressions of Ekostrovskaya and Babinskaya Imandra, the southern sub-basins of Lake Imandra. Lithological, 14C and diatom data suggest that the brackish-water reservoir followed by the fresh-water one existed in the Ekostrovskaya Imandra depression during the Younger Dryas chronozone prior to 11,400cal. yr BP. The Fennoscandian Ice Sheet margin is assumed to have been located in the Lake Imandra basin, covering western Babinskaya Imandra earlier than c. 10,250 cal. yr BP. The early Holocene c. 11,400–8,500 cal. yr BP was marked by a significant westward retreat of the ice margin in the western Lake Imandra depression and adjacent areas, and an extensive fresh-water pra-Imandra Lake basin was formed there. At the end of the Preboreal, earlier than c. 9,210–8,500 cal. yr BP, the pra-Imandra Lake coastline was at least 16–18 m higher than the modern one, as can be assumed according to coastal morphology and lithostratigraphical data. The coastline of that reservoir changed, water square slightly reduced, and isolated small lakes emerged on coasts during the early Holocene.
Raktažodžiai lithostratigraphy; diatoms; bottom sediments; natural outcrops; coastal morphology; periglacial fresh-water reservoir; marine inundation
The surface of earth on the territory of Lithuania is covered by sediments of the Quaternary system, which are the object of human economic activities. Reliable assessment of sediment deformations is an important task of modern engineering geology and geotechnical engineering. The deformation of sediments is most often described using the modulus of deformation. The current article overviews different methods employed in deformation moduli determination and their application possibilities. The deformation moduli, which are used in various calculations, are usually calculated using correlation formulas and empirical coefficients. Thus, the obtained results may be inaccurate or completely unsuitable for further interpretation of the numerical situation. This article presents recommendations with regard to the use of various calculated deformation moduli in interpreting Lithuanian Quaternary system sediments.
Raktažodžiai secant modulus of deformation; residual modulus of deformation; dynamic modulus of deformation; oedometer; triaxial compression test apparatus; CPT
The first state reserve in Lithuania was established in 1960; however, no detailed assessments of changes in the state of the protected values therein have been performed ever since. Landscape reserves are the most complex ones and they pursue the twofold goal – to conserve the values and to use them sustainably. In order to be resilient themselves, thus contributing to broader objectives of social-ecological resilience, the reserves should be able to adapt to ever-changing social and ecological conditions in a way that supports the long-term persistence of population, communities, and ecosystems of conservation concern. Therefore, it is necessary to update information on the status of values protected in the reserves. The article addresses this need by offering a concise and user-friendly methodology for assessing the status of landscape reserves. The methodology focuses on three main components: (1) general features of the landscape structure, (2) the effectiveness of protection of values and (3) the pressures and threats they experience. Two state landscape reserves were selected for testing the applicability of the methodology: one in Vilnius city, the other 50 km to the west, in the countryside. Application of the common methodology will allow to assess the condition of landscape reserves in the country. Further development of the methodology could include evaluation of external pressures (e.g. urbanization) as well as addition of remote sensing techniques.
Raktažodžiai protected areas; landscape reserves; landscape resilience; assessment methodology, spatial resilience