Genesis, distribution and dynamics of lagoon marl extrusions along the Curonian Spit, southeast Baltic Coast

A unique geological process involving the extrusion of lagoon marl from beneath massive migrating sand dunes characterizes large segments of the Curonian Spit, a 100-km-long sandy barrier separating the Curonian Lagoon from the Baltic Sea. This study reveals that relict lagoon marl, composed of Holocene organic sediments like gyttja and clayey gyttja, was deformed, compacted, and dehydrated by landward-migrating dunes during the Littorina Sea transgression—a phenomenon termed 'dune tectonics.' Using advanced techniques such as side-scan sonar, multibeam echosounder, seismic imaging, sediment sampling, and video observations, researchers identified extensive underwater marl outcrops at depths of 5–15 m along the southern half of the spit. Spatial analysis further constrained the southeastward migration rates of the dune massif. A conceptual model explains both onshore marl exposures above the regional water table and offshore relict marl diapirs, offering new insights into the dynamic interplay between coastal geomorphology and sedimentary processes in this UNESCO World Heritage Site.

Sergeev, A. Y., Zhamoida, V. A., Ryabchuk, D. V., Buynevich, I. V., Sivkov, V. V., Dorokhov, D. V., Bitinas, A., & Pupienis, D. (2016). Genesis, distribution and dynamics of lagoon marl extrusions along the Curonian Spit, southeast Baltic Coast. Boreas, 46(1), 69–82. Portico. https://doi.org/10.1111/bor.12177