Evidence of paleoseismic activity recorded in glaciolacustrine sediments predating the Weichselian glacial maximum in East Lithuania

Soft-sediment deformation structures (SSDS) were identified in proglacial lacustrine (glaciolacustrine) sediments dated to 25–24 ka in the Buivydžiai outcrop, situated 30 km north of Vilnius in east Lithuania. These sediments accumulated in front of the last Weichselian glaciation maximum. The SSDS originated due to sandy silt liquefaction that disrupted the decimeter-thick silty sand interlayer. A NW-SE trending Buivydžiai fault was mapped in the proximity (8 km) of the Buivydžiai outcrop. The fault is well traced by a dense drilling in the sediments of the preglacial Daumantai Formation in the basal part of the Quaternary cover and attributed to the earliest Pleistocene. Depth difference of the formation along the fault is ~5–8 m; the northern flank is relatively uplifted with respect to the southern flank. The Buivydžiai earthquake was most likely induced by formation of an elastic forebulge flexure of the Earth's crust in front of the ice sheet. The magnitude was evaluated ~M = 6.0–6.5 and was most likely of shallow hypocenter depth. Furthermore, the Bystritsa (Belarus) earthquake of magnitude M = 3.5–4.0 was registered in December 1908 to the east (12 km) of the Buivydžiai outcrop along the Buivydžiai fault, which points to recurrent seismic activity of this fault.

Seismic stratigraphy of the Klints Bank east of Gotland (Baltic Sea): a giant drumlin sealing thermogenic hydrocarbons

This work analyses six high-resolution multi-channel seismic profiles across the Klints Bank east of Gotland. The Klints Bank consists of a drop-shaped increase of the Quaternary thickness and is oriented in an approximately north-southern direction with a length of over 50 km, a width of about 15 km and a maximum thickness of 150 m. The glacial origin of the Klints Bank can be verified with the dataset presented in this study. We classify the feature as a (giant) drumlin due to its steep up-ice and tapered down-ice face in combination with an orientation parallel to the ice-flow direction of the Weichselian glaciation. The seismic image of the internal structure of the Quaternary unit shows no uniform stratification or deformation patterns; instead, local sub-parallel reflection patterns interlayered with transparent units are observed. The averaged seismic velocity of this unit is about 2000 m/s, which is interpreted as an autochthonous deposition of glaciogenic sediments. Signs of overprinting are interpreted based on the geometry of the flanks of the structure, which appear mostly in the form of collapse structures and lifted blocks due to compressional thrust faulting. Phase-reversed events within and beneath the Quaternary are perceived as strong evidence of fluid (hydrocarbon) presence within the Klints Bank. Organically enriched Palaeozoic shales in south-easterly direction of the Klints Bank presumably give the origin of these thermogenic hydrocarbons.

Morphometric indicators of insular and marginal morainic uplands (based on LiDAR data) of the Last and pre-Last Glaciations, case of Lithuania

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.

A glaciotectonic complex at the Vastyanskiy Kon’ outcrop, NE European Russia: subglacial or proglacial deformations?

<p>The Vastyanskiy Kon’ (VK) outcrop is the largest exposure of Quaternary sediments in the northeastern European part of the Russian Federation. The VK consists of Eemian to Weichselian marine and continental sediments that were deformed within a glaciotectonic complex of terminal moraine of the advancing Late Weichselian Kara Sea Ice Sheet. However, a few aspects of the stratigraphy and dynamic evolution of the VK glaciotectonic complex remain unresolved and ambiguous.</p><p>A particular debate concerns the structural position and age of the so-called “lower diamicton” (LD), a till-like unit, which generally occurs within the central part of the VK section. Two models on the development of the LD unit have been previously proposed. According to the first model, the LD is situated in its original stratigraphic position and reflects possible earlier Early/Middle Weichselian glaciation and is later deformed by Late Weichselian proglacial glaciotectonism. The second model suggests that the LD unit is a result of an injection of the overlying Late Weichselian lodgement till into underlying sandy units.</p><p>In our study, we performed a detailed tracing of stratigraphic units and structures utilizing classic surface mapping and 3D photogrammetric methods to access previously understudied parts of the VK. Our observations show that the architecture of the VK glaciotectonic complex represents an imbricate fan and partly support the model where the LD likely represents a till flow unit sourced from the overlying lodgement till under subglacial deformation mode. Finally, we conclude there is no evidence for postulated Early/Middle Weichselian glaciation in the study area.</p>

Indication of glacially-induced fault reactivation in Latvia, Lithuania and the Kaliningrad District of Russia from models of glacial isostatic adjustment

<p>We model the change of Coulomb Failure Stress (δCFS) during the Weichselian glaciation up until today at 12 locations in Latvia, Lithuania and Russia that are characterised by soft-sediment deformation structures (SSDS). If interpreted as seismites, these SSDS may point to glacially-induced fault reactivation. The δCFS suggests a high potential of such reactivation when it reaches the instability zone. We show that δCFS at all 12 locations reached this zone several times in the last 120,000 years. Most notably, all locations exhibit the possibility of reactivation after ca. 15 ka BP until today. Another time of possible activity likely happened after the Saalian glaciation until ca. 96 ka BP. In addition, some models suggest unstable states after 96 ka BP until ca. 28 ka BP at selected locations but with much lower positive δCFS values than during the other two periods. For the Valmiera and Rakuti seismites in Latvia, we can suggest a glacially-induced origin, whereas we cannot exactly match the timing at Rakuti. Given the (preliminary) dating of SSDS at some locations, at Dyburiai and Ryadino our modelling supports the interpretation of glacially-induced fault reactivation, while at Slinkis, Kumečiai and Liciškėnai they likely exclude such a source. Overall, the mutual benefit of geological and modelling investigations is demonstrated. This helps in identifying glacially-induced fault reactivation at the south-eastern edge of the Weichselian glaciation and in improving models of glacial isostatic adjustment.</p><p>This work has been published in Steffen et al. (2019).</p><p>Reference:</p><p>Steffen, H., Steffen R., Tarasov L. 2019. Modelling of glacially-induced stress changes in Latvia, Lithuania and the Kaliningrad District of Russia. Baltica, 32 (1), 78–90.</p>

Sea cliff at Glowe: stratigraphy and absolute age chronology of the Jasmund Pleistocene sedimentary record

Four remarkable Pleistocene cliff outcrops scattered across the peninsula of Jasmund exhibit the dynamics of the Scandinavian Ice Sheet during the Weichselian glaciation in this area. The investigated sites display up to 30 m thick sequences of glacial tills with intercalated (glaci)fluvial to (glaci)lacustrine sediments. Based on detailed lithofacies analyses and a physical age chronology, we trace the reconstruction of the depositional sequences and their corresponding stratigraphic position within the Weichselian record.

Modelling of glacially-induced stress changes in Latvia, Lithuania and the Kaliningrad District of Russia

We model the change of Coulomb Failure Stress (δCFS) during the Weichselian glaciation up until today at 12 locations in Latvia, Lithuania and Russia that are characterised by soft-sediment deformation structures (SSDS). If interpreted as seismites, these SSDS may point to glacially-induced fault reactivation. The δCFS suggests a high potential of such reactivation when it reaches the instability zone. We show that δCFS at all 12 locations reached this zone several times in the last 120,000 years. Most notably, all locations exhibit the possibility of reactivation after ca. 15 ka BP until today. Another time of possible activity likely happened after the Saalian glaciation until ca. 96 ka BP. In addition, some models suggest unstable states after 96 ka BP until ca. 28 ka BP at selected locations but with much lower positive δCFS values than during the other two periods. For the Valmiera and Rakuti seismites in Latvia, we can suggest a glacially-induced origin, whereas we cannot exactly match the timing at Rakuti. Given the (preliminary) dating of SSDS at some locations, at Dyburiai and Ryadino our modelling supports the interpretation of glacially-induced fault reactivation, while at Slinkis, Kumečiai and Liciškėnai they likely exclude such a source. Overall, the mutual benefit of geological and modelling investigations is demonstrated. This helps in identifying glacially-induced fault reactivation at the south-eastern edge of the Weichselian glaciation and in improving models of glacial isostatic adjustment.

Existing and Proposed Urban Geosites Values Resulting from Geodiversity of Poznań City

Poznań, a city in central-western Poland, is located in the lowland region but has no less attractive geomorphological and human history. It was here that Poland was born at the end of the tenth century. The city’s location is connected with the meridian course of the Warta River valley. In contrast, in the northern part of the city, there is a vast area of the frontal moraines of the Poznań Phase of the Weichselian Glaciation. Against the backdrop of the geomorphological development of the city, the article presents the existing geosites, classified as urban geosites. The present geosites include three lapidaries with Scandinavian postglacial erratics, one of them also with stoneware, a fragment of a frontal push moraine and impact craters. Besides, three locations of proposed geosites with rich geomorphological and/or human history were identified. These are as follows: the peat bog located in the northern part of the city, defence ramparts as exhumed anthropogenic forms, and the Warta River valley. The existing and proposed geosites in Poznań were evaluated in three ways. In general, it should be assumed that the proposed new geosites are higher ranked than the current ones.