Search

The susceptibility of grains in sediment to the liquefaction process causes the development of deformation structures. Some sediments undergo liquefaction, others do not. There is a group of sediments especially prone to liquefaction, which was proven during laboratory experiments. However, the field results are often slightly different from those obtained experimentally because of many unpredictable factors influencing the course of the liquefaction process. For this reason, we tested 144 samples of unconsolidated Quaternary‐age sediments, collected from eight study sites in Germany, Lithuania and Latvia, which have been liquefied. We also present some new dating results. These samples were divided into two groups of soft‐sediment deformation structures: concave up (e.g., injection structures) and concave down (e.g., load casts, pseudonodules). The granulometry of all deformation types was statistically evaluated, which allowed identifying textural differences between sediment contained in concave up and concave down structures. We suggest that the mobilization of silt fraction is responsible for the further deforming process. We also confirm that the maximum content of clay in sediment prone to liquefaction cannot exceed 14%, but only with a significant content of coarser fractions (silt and sand). Moreover, we identified two separate zones of the specific grain size in which only concave down structures or only concave up structures develop as an effect of liquefaction, and the third "transitional zone" where all forms occur. The "transitional zone" is separated from the concave up structures and concave down structures zones by two "gap zones" in which no liquefied sediments were observed. Plain Language Summary: Liquefaction is a process of temporary loss of shear strength of water‐saturated sediments, during which the solid‐state sediment behaves like a plastic mass or a viscous solid. It can be triggered in natural conditions by numerous factors, including waving, rapid sedimentation, earthquakes and the fall of meteorites. Sandy silt and silty sand are commonly known as the most liquefaction‐prone sediments, but the specific granulometric features are still insufficiently characterized. We analyzed 144 samples of unconsolidated Quaternary‐age sediments deposited in lacustrine, shallow marine and fluvial environments, which were liquefied. We divided all liquefaction‐induced soft‐sediment deformation structures into active and passive concave up (e.g., injection structures) and active and passive concave down (e.g., load structures). As a result of statistical tests, provided for each group separately, we observed that the silt content is the main factor for sediment deformation processes initiating the further development of all deformation structures. On the basis of grain‐size composition of liquefied sediments, we also identified two separate zones for which only concave down structures or only concave up structures develop as an effect of liquefaction, and the third "transitional zone" where all forms occur. These zones are separated by two "gap zones," where no liquefied sediments were observed. Key Points: Liquefaction‐induced soft‐sediment deformation structures were divided into active and passive concave up structures and active and passive concave down structuresContent of silt is the main factor for deformation processes initiating the further development of all deformation structuresConcave up structures zone, concave down structures zone and transitional zone were distinguished on the basis of grain‐size composition of liquefied sediments [ABSTRACT FROM AUTHOR]

We present a study based on four inland eolian locations in Eastern, Central and Southeastern Lithuania belonging to the northeastern part of the ‘European Sand Belt’ (ESB). Although there have been several previous studies of the ESB, this north-eastern extension has not been investigated before in any detail. The sedimentary structural–textural features are investigated and a chronology was derived using optically stimulated luminescence on both quartz and feldspar. The sedimentary structures and the rounding and surface characteristics of the quartz grains argue for a predominance of eolian transport. Additionally, some structural alternations and a significant contribution of non-eolian grains are interpreted as inherited local glacial/glaciofluvial-bearing lithologies. Three main (glaciolacustrine–) eolian phases are distinguished based on the position in the landscape and the luminescence ages: (1) An older eolian series around 15 to 16 ka, possibly correlated with the cold GS-2a event according to the GRIP stratigraphy, and (2) a younger eolian series around 14.0 ka, possibly representing the GI-1d and 1c events. The older eolian series is underlain by (3) a glaciolacustrine – eolian series for which the period of deposition remains uncertain due to the significant discrepancy between the ages based on quartz and feldspar. [ABSTRACT FROM AUTHOR]