Santrauka Glacial geomorphological mapping of western Latvia using a 1-m-resolution digital elevation model generated from airborne LiDAR data has revealed two sets of mega-scale glacial lineations (MSGLs), one of which is superimposed by crevasse-squeeze ridges (CSRs). CSRs occur as a dense ridge network with a dominant orientation of ridges perpendicular to the ice flow direction. The landform assemblage is interpreted as evidence for two separate phases of fast ice flow with different ice flow directions during the overall deglaciation of the Fennoscandian Ice Sheet (FIS). The first fast ice flow phase occurred from the northwest by the Usma Ice Lobe that extended in the Eastern Kursa Upland. The second fast ice flow occurred from the north by the Venta Ice Tongue in a narrow flow corridor limited mainly to the Kursa Lowland. Active ice streaming caused ice crevassing perpendicular to the ice flow direction and formation of CSRs by squeezing of subglacial till into basal crevasses. A good preservation of the CSRs and general lack of recessional moraines suggest widespread stagnation and ice mass melting after the shutdown of the Venta Ice Tongue followed by the formation of the Venta-Usma ice-dammed lake and glaciolacustrine deposition in the lowest areas of lowland. Our data provide the first evidence of CSRs in the south-eastern terrestrial sector of the FIS suggesting the dynamic ice streaming or surging behaviour of the ice lobes and tongues in this region during deglaciation.
Raktažodžiai surge; fast ice flow; subglacial bedforms; MSGL; basal crevasses
Eva Raudonytė-Svirbutavičienė*, Rimutė Stakėnienė, Ieva Baužienė, Kęstutis Jokšas
Santrauka In this study, results on PAHs distribution, origin and ecological risks from several surveys are combined with a special focus on naphthalene. The study area comprises a large part of the Lithuanian territory and includes two biggest Lithuanian rivers, Nemunas and Neris (sampling locations with different hydrodynamics and varying anthropogenic pressure), four different lakes and the central part of the Curonian Lagoon. ∑16PAHs concentrations in the surface sediment ranged between 74.5 and 6377 ng g-1 dw. In 9 locations out of 14, naphthalene concentration exceeded TEL and posed a threat to the environment. Naphthalene was a significant contributor to the total PAHs concentration in the study area with concentrations ranging from 0.78 to 106 ng g-1 dw. Despite the highest naphthalene concentration recorded in Lake Talkša, naphthalene had only a minor contribution to the PAH profile in this lake. Even a lower impact of naphthalene was observed in the Curonian Lagoon. Naphthalene was found to be the prevailing compound in the Nemunas River Delta region, in a relatively clean Lithuanian Lake Dusia and in some Neris River locations. The highest contribution of naphthalene was observed in the areas with low urbanization degree, but close to peatlands. The main naphthalene source in the study area might be related to peatlands, albeit additional naphthalene sources, such as food cooking, burning of agricultural residues, wood and coal could not be completely rejected either. The sources of other PAHs are attributed to the vehicular emission, emissions from industry, biomass and coal burning.
Raktažodžiai naphthalene sources; surface sediment; PAHs from vehicular emissions; Lake Talkša; Curonian Lagoon
Santrauka The research is focused on the topographic modelling and mapping of the Aleutian Trench. The study area is situated in the Bering Sea, a marginal sea located northernmost of the Pacific Ocean, between Alaska and Kamchatka Peninsula. The geological setting of the region is characterized by the subduction of the oceanic Pacific Plate below the continental North American Plate. Other features include high seismic activity along the Aleutian island arcs bordering the oceanic seafloor. The objective of this paper is to explore the interaction between the geophysical setting affecting the relief of the seafloor by using geoinformation techniques and geological analysis. In the hypothesis of this study, variations in the geophysical fields as independent variables are reflected in the morphology of the seafloor, which can be observed using data visualization by the advanced cartographic scripting solutions. The open source high-resolution topographic map (ETOPO1), marine free-air gravity and Bouguer gravity anomaly data were used and integrated to investigate the potential correlation between the geophysical, geological, tectonic and topographic settings of the Bering Sea. Our main method includes bathymetric mapping of the area with publicly available bathymetric data using GMT. Materials include open source data: ETOPO1 raster grid with 1 arc-minute resolution, EGM96 gravity and vector contour layers of GMT. The research included complex thematic mapping of the region, including topographic, contour, geodetic and geophysical mapping, 3D modelling and geomorphological plotting of the 30 cross-section segments of the trench located SE off the Bowers Ridge. According to the processed ETOPO1 dataset, the minimal depth is -8480 m and the mean is -3089.154 m. The geoid undulations model shows that the majority of the gravity values lie in the interval between -10 and 20 m with the lowest values along the trench. The statistical histogram shows that the most common depth value in the segment of the Aleutian Trench is -4800 m, occurring 1722 times. The profile linear trend modelling was done with four different approaches of the regression model (y = f(x) + e) by weighted least squares (WLS) with arguments: 1) m2t = a + bt (polynomial model degree one); 2) m3t = a + bt + ct2 (polynomial model degree two); 3) m4t = a + bt + ct2 + dcos2π*t + esin2π*t (polynomial model with Fourier series one); and 4) additional plotting residuals. Surface modelling was performed using xyz modelling from the ASCII data enlarging fragment towards SE of the Bowers Ridge. The tested functionality of modules of GMT presented an effective cartographic scripting toolset enabling a precise topographic mapping and 3D modelling. The paper contributes to a more detailed understanding of the Pacific Ocean seafloor bathymetry, more specifically of the selected segment of the Aleutian Trench near Bowers Ridge area.
Raktažodžiai GMT; cartography; geology; 3D modelling; geophysics; gravity
Santrauka In this study, a sandy beach in Šventoji, Lithuania, a popular albeit not highly urbanised touristic destination, was analysed for microplastic pollution in the summer of 2019. The presence and abundance of microplastics in different sites of the beach were evaluated. Šventoji Beach was found to be significantly polluted with microplastic, its concentration ranging from 85 to 325 MPs kg−1dw. Such concentrations are relatively high if compared to other Baltic Sea coasts and worldwide. The physico-chemical characteristics of the plastics showed limited variability. Blue fibres were prevailing over other types of microplastics. Blue and red/orange fibres were identified as nylon containing copper–phthalocyanine dyes, while red/orange fibres as high-density polyethylene. This study provides new insights into the application and development of microplastic analysis methods for the coastal sands of the Baltic Sea.
Raktažodžiai Baltic Sea; non-tidal beach; microplastic identification; marine debris; coastal pollutants
Santrauka This study presents a detailed spatiotemporal analysis for the Frakull-Durrës (F-D) fault zone at the beginning of 2020. For this purpose, the most frequently used statistical seismicity parameters such as magnitude completeness, Mc-value, Gutenberg-Richter b-value, recurrence times, annual probabilities and standard normal deviate, Z-value, were mapped. The F-D fault zone was divided into two seismogenic subregions, and Mc-value was taken as 2.5 for both the south and north parts. The b-value was estimated as 0.83 ± 0.06 for the south part and 0.85 ± 0.06 for the north part. b-values for both zones are smaller than 1.0 and these values may be considered to be a larger stress accumulation to build up over time and to be released by the next possible earthquakes. Clear decreasing trends were observed in time variations of b-values before the occurrences of several strong main shocks. Analyses of annual probabilities and recurrence times suggest that the study region has an intermediate/long-term earthquake hazard in comparison to occurrences of strong/destructive earthquakes in the short term. Some anomaly regions of a small b-value and a large Z-value were found along the F-D fault zone at the beginning of 2020: i) among Lushnje-Tirana-Durrës including the middle part of the F-D fault zone, ii) in and around Lezha including the north end of the F-D fault zone. Thus, the combination of regions with the lowest b-value and largest Z-value may supply preliminary results for earthquake hazard, and these regions may be considered to be the most likely regions for future strong/large earthquakes in the F-D fault zone.
Raktažodžiai seismicity; b-value; Z-value; recurrence time; annual probability; earthquake hazard
Santrauka The current study has analyzed active fault data along the East Anatolian Fault Zone (EAFZ) applying both manual (classic) and modern versions of the box counting method. The EAFZ active fault dataset used for analysis was taken from the Geoscience Map Viewer and the Drawing Editor from the website of the General Directorate of Mineral Research and Exploration. The study covered an area stretching from Karlıova in the north to Kırıkhan in the south. The fractal analysis of the earthquake surface rupture and the Holocene fault data was performed. Fractal dimensions of the EAFZ active-fault data were calculated for 15 boxes and compared with correlation coefficient values. The calculated fractal dimension values were found to vary with the density of the active-fault data falling into the boxes. The maximum fractal dimension value D1 was determined for Karlıova and its surroundings, which can be associated with the fault density due to the branching geometry.
Raktažodžiai the box counting method; fractal geometry; fractal analysis; correlation coefficient; earthquake surface rupture
Santrauka Potentially favourable conditions for overflows of water between the Vistula and Curonian lagoons via two branches of the Pregolya River were studied using water level data (2002–2007) at the hydrological stations located in lagoons and the river. The episodes (of two days and longer) of the ‘reversed slope’, when the water level in the Vistula Lagoon (7 cases) and the Curonian Lagoon (41 cases) was higher than in the river streams connecting them, were found. This confirms the theoretical possibility of water overflow between the Vistula and Curonian lagoons, back and forth. Some unusual cases (of two days and longer) when the ‘reverse slope’ of water level existed simultaneously in both recipient bodies (Vistula and Curonian lagoons) were also found. The analysis showed that wind conditions were not the single determining factor. Direct measurements of near-bottom currents showed that backward water flow appeared in both branches. Backward water flow developed mainly in the low parts of river branches, i.e. closer to the lagoons. Time delay in water flow variations and the appearance of backward water flow between downstream and upstream points was 2–7 hours, or about 4 hours on average. The signal of backward current in one branch penetrated upstream not only the other branch (correlation coefficient was about 0.64 and 0.71 for 1-h and 12-h running averaged series, respectively) but further upstream the mainstream of the Pregolya River.
Raktažodžiai river mouth; currents; water flow; measurements; backflow; overflow; Pregolya River; Deyma River
Santrauka The focal-mechanism solution for the second shock of the Kaliningrad earthquake on 21 September 2004 (13:32 UTC) with a magnitude of Mw 5.2 was obtained using the waveform inversion (WFI) method. The method was used with the aim of its subsequent application as a discriminator in the East Baltic region for recognizing the genesis of seismic events based on data from a limited number of stations. The WFI method was tested by broadband channels. The results of focal-mechanism solution (strike = 119°; dip = 73°; rake = –163°) allowed (1) to state the source mechanism as a right-lateral strike-slip, (2) to estimate the optimal source depth equal to 3.0 km, and (3) to estimate the parameters of the compression axes (Paz = 340°; Ppl = 29°), tension (Taz = 252°; Tpl = 1°) and the axis coinciding with the intersection of two nodal planes (Baz = 162°; Bpl = 66°). These results are in satisfactory agreement with the results of the leading seismological agencies. Seismotectonic analysis showed that the epicentre of the earthquake is located inside the structure formed by the Yantarnensk fault zone and the zone of the Bakalinsk ruptured flexure. The WFI method showed its potential use as a discriminator of the genesis of seismic events.
Raktažodžiai East Baltic region; seismic moment tensor; seismotectonic analysis; strike; dip; rake; compression; t ension; nodal plane; point source; direct waves
Santrauka The main goal of the study is to evaluate changes that have occurred in the Pūčkoriai outcrop surface over the 2014–2019 period and to compare the accuracy of ground-based measurements with that of UAV aerial image models. Ground-based measurements were performed applying the original methodology, which involves comparison of the first one and subsequent beam direction. For surface change surveys, we used repeated terrestrial geodetic measurements and UAV imagery. Ground-based measurements were performed using a Trimble M3 Total Station (with RTK); aerial images were captured using UAV INSPIRE1 with a ZENMUSE X3 camera. Pix4D photogrammetric software was used to create a DEM. The comparison of repeated terrestrial measurements and UAV aerial imagery revealed that the average change in the outcrop surface altitude over the period 2014–2019 amounted to 8.3 cm, with a maximum of 24.23 cm and a minimum of 0.33 cm. Contactless remote sensing allows obtaining data without affecting or altering the surface of the exposed deposits. The difference between terrestrial geodetic measurements and the UAV-based DEM did not exceed the following values: ΔX and ΔY ≤ 68 mm; ΔZ ≤ 21 mm. Previous research has shown that the use of UAV aerial photography images for assessing changes in outcrops consisting of loose sediment layers yields sufficiently accurate results. The present study focuses on the determination of quantitative indicators of seasonal changes in the outcrop surface. Quantitative surface changes of the outcrop were mapped based on dynamic signs, surface comparison and a formal choropleth map (10 × 10 m); dynamic zones of the outcrop were distinguished based on the results obtained employing these methods. The data obtained can be extrapolated to other Lithuanian river outcrops, which are characterized by a variety of sediments.
Raktažodžiai high-precision GPS; remote sensing; UAV; geomorphological mapping
Raktažodžiai modern diatoms; lake sediments; Principal Component Analysis; spatial analysis