We acquired high-resolution reflection seismic data using a broadband
digital-based landstreamer system to characterize a depression related
to the Mesoproterozoic (Jothnian) Satakunta sandstone basin in the
Köyliö study area, southwest Finland. This ca. 800-m-wide depression is
infilled with up to 100-m-thick (late) Quaternary interlobate
glaciofluvial complex sediments. The seismic images clearly reveal
details of the glaciofluvial complex, sandstone depression topography,
and brittle structures related to the formation of the sandstone basin
by oblique transtension. Additionally, we identified the setting of a
diabase laccolith within the sandstone and the geometry and position of
the steep sandstone contact. The esker core does not follow the
sandstone-Svecofennian basement rock contact or lean to it. The esker
core is at a depth of 50–60 m on the flank of the depression. The
seismic data image the esker core and other architectural elements of
the esker. We highlight the potential of the digital-based landstreamer
in the research of complex Quaternary sediments in major bedrock
depressions including the characterization of the underlying bedrock
properties. We also discuss the possible tunnel valley origin of the
sandstone depression.