Lozovskis S., Katinas V., Baltrūnas V. Ruopiškių stambios linijinės subglacialinės formos susidarymo ypatybės: glacialinių nuogulų struktū-ros tyrimas. Geologija. Geografija. 2015. T. 1(4). ISSN 2351-7549.Tyrimui pasirinktas Ruopiškių drumlinoidas -tipiška stambi linijinė subglacialinė forma, esanti Šiaurės Lietuvoje, Biržų-Vabalninko plote. Literatūroje tokios formos dažnai vadinamos mega-scale subglacial lineations (MSGL). Tiriamajame drumlinoide, be anksčiau darytų stebėjimo taškų, buvo iškasti nauji 6 kasiniai, juose pamatuota stambianuotrupinės medžiagos (žvirgždo ir gargždo) ilgųjų ašių orientacija bei polinkio kampas, paimti mėginiai granuliometrinei ir petrografinei analizei, magnetinio imlumo anizotropijai nustatyti. Darbe aptariami naudoti tyrimo metodai. Žvirgždo ir gargždo ilgųjų ašių orientacijos ir polinkio kampo matavimai buvo vizualizuoti stereogramomis, o smulkianuotrupinės, įskaitant ir molingos, medžiagos magnetinio imlumo anizotropijos nustatymo duomenys apibendrinti naudojantis Anisoft42 programine įranga. Atlikti tyrimai išilgai tyrinėto Ruopiškių drumlinoido parodė, kad bent viršutinė jo dalis nėra vienalytė. Tai leido skirti tris drumlinoido dalis, taip pat išsiskiriančias savo morfometrinėmis ypatybėmis ir paviršiuje. Manytina, kad ši stambi linijinė subglacialinė forma iš esmės susidarė slenkančio ledyno plyšyje, išsispaudus jame pagrindo moreninei medžiagai. Susidariusio poledyninio gūbrio šlaitai ir ketera patyrė slenkančio ledyno šoninį glaciodinaminį poveikį, kurio požymius matome stambiųjų nuotrupų orientacijos ir polinkio bei smulkianuotrupinės medžiagos magnetinio imlumo anizotropijos (AMS) stereogramose.Raktažodžiai: Šiaurės Lietuva, linijinė subglacialinė forma, drumlinoidas, magnetinio imlumo anizotropija (AMS) ĮVADASLietuvoje, kaip ir visose buvusio kontinentinio apledėjimo srityse, tiriant subglacialinio (poledyninio) reljefo formas yra aptinkamos ovalios ir pailgos kalvos, kurių ilgoji ašis lygiagreti ledyno slinkimo krypčiai. Tai -drumlinai, fliutingai, drumlinizuoti gūbriai ir kitos formos, apibendrintai kartais vadinamos drumlinoidais, o sudėtingas procesas, kurio metu susidaro šios formos, -drumlinizacija (Brodzikowski, van Loon, 1991). Be pirmųjų geomorfologinių įžvalgų XX a. pr., Lietuvoje drumlinoidiniam reljefui buvo skirta palyginti mažai dėmesio (Čepulytė, 1956;Basalykas, 1965;Mikalauskas, Mikutienė, 1971;Gaigalas, Marcinkevičius, 1982;Gaigalas, 1997). Užsienio šalyse specializuotais tyrimais subglacialinių reljefo formų pažinimas yra pažengęs toliau, taip pat ir kaimyninėje Lat vijoje (Zelčs, Dreimanis, 1997;Zelčs, Markots, 2004).
North Lithuania was chosen for a study of the “drumlinised” morainic surface produced during the Last Glaciation, typified as well-expressed mega-scale glacial lineations (MGSLs). The goal pursued in the present study was to investigate the morphology and macro- and microfabrics of some large glacial lineations to substantiate their formation mechanism. The geological structure of Quaternary strata of an area and the erosion depression of sub-Quaternary surface suggest favourable conditions for the glacier to rapidly fluctuate into the area during deglaciation of Late Glaciation. Investigations of Pleistocene tills observed in the MSGLs of the area preserved on the eastern and western margins of the study area show that these deposits are formed from the upper part of the Baltija Subformation – Middle Lithuanian till. According to two sets of grain sizes, MSGL tills are often notable for increased values of relative entropy. Therefore, morainic material deposited during the redeposition of the Baltija Subformation till was thoroughly mixed. The data on orientation and inclination of long axes of gravel and pebbles in the tills that form MSGLs, as well as the anisotropy of magnetic susceptibility (AMS) of microclast material suggest that the formation of MSGLs may have been influenced by directions of the local glacial stress that are different from the regional direction of glacial motion (about N–S). The change of macro- and microfabric of till confirms the formation of MSGLs during glacier erosion by groove-ploughing from the Baltija Subformation till. This occurred when basal ice carried over clast material to MSGL crests from interridge areas.
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.
<p>In Worlds practice it is known that shale gas can be viable source of energy. Lithuania is situated in the central and eastern parts of the pericratonic Baltic Sedimentary Basin. The Lower Silurian shales are considered as a most prospective formation for gas exploration due to high amount of organic matter (more than 2%) and large thickness (120-200 m). Mineralogical composition and related petrophysical and mechanical properties were assessed for west Lithuanian shales that occur at the depths of 1500-2000 m. Thermal maturity of organic matter Tmax ranges from 432 to 455<sup>o</sup>C (oil window). Shales contain 37&#8211;57% of clay minerals. Illite predominates and chlorite is less abundant mineral. Quartz and feldspars compose about 35&#8211;45% of shale volume. The carbonate content ranges from 1% to 28%. TOC content is about 2%, while interpretation of well logs show higher average amount of TOC ranging from 2.5 to 8%. The Middle Llandovery &#8220;hot&#8221; shales of 4-11m thick show anomalous TOC content up to 20%. The mineral brittleness index was calculated to range mainly from 0.35 to 0.40 (bellow the lower exploitation limit), while logging brittleness index varies from 0.40 to 0.60 (good quality). This difference is explained by logging coverage of the whole Lower Silurian section by contrast to selective drill coring of wells. The bulk porosity decreases with depth from 16% to 3% (linear correlation Depth=-0.0107&#215;Porosity+25.7). The low cation exchange capacity (0.2-8.8 meq/100g) is accounted to specific mineral composition. The low erodibility (Roller Oven technique) is related to high shale compaction. The capillary suction time method was used to estimate the swelling capacity of shales. Rather low values are explained in terms of predominance of illite in clay fraction and high amount of detrital grains. In summary, the exploitation parameters estimated for west Lithuanian shales are classified as good and excellent and can be used to minimize the impact on the environment.</p>
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