Palaeoliquefaction features in Baltic Ice Lake sediments: A case study from Western Latvia

Abstract

Studies of liquefaction features in sedimentary archives offer valuable insights into past deformation processes. This study investigates palaeoliquefaction-induced soft-sediment deformation structures (SSDS) preserved within Late Pleistocene nearshore deposits at the Sārnate site in western Latvia, formed during the Baltic Ice Lake. Sedimentological, microstructural, and geochronological analyses were employed to reconstruct depositional conditions and constrain the timing of deformation events. Changes in depositional environments associated with the Baltic Ice Lake, specifically the transition from deeper to shallower water at the study site, were likely driven by the drainage of the Baltic Ice Lake. This may have created conditions conducive to liquefaction and fluidisation, leading to sediment destabilisation and the formation of SSDS, like injection structures, load structures (load casts, pseudonodules) and flame structures. These environmental shifts likely increased pore water pressure within the heterolithic deposits, composed of alternating coarse and fine sediments, rendering them more prone to liquefaction. Liquefaction and the resulting SSDS in these water-saturated nearshore deposits were primarily triggered by overloading, which exerted additional, uneven pressure on the underlying layers, thereby enhancing their liquefaction potential. This process was likely intensified by storm and wave activity. Our findings highlight the critical role of site-specific sedimentological characteristics in influencing liquefaction susceptibility and deformation styles. The spatial distribution, morphology, and textural features of the observed SSDS, indicate past episodes of sediment deformation driven by water level changes in the Baltic Ice Lake. These insights contribute to a broader understanding of non-seismic SSDS formation in nearshore settings and offer a valuable reference for similar features in formerly glaciated regions.