A Late Pleistocene lacustrine transgression in the Fehmarn Belt, southwestern Baltic Sea

Abstract

In order to reconstruct the late Pleistocene seismic stratigraphy, 550 km of high-density 3.5 kHz subbottom seismic-reflection profiles were recorded within a 70 km(2) area in the narrow offshore border zone between Germany and Denmark. A depositional unit 3 was analysed for its seismic facies association, and in the central study area mound, oblique, channel, reflection-free, shingled, hummocky, broken and parallel associations occurred. The rims of the association shows mound, oblique, hummocky and minor parallel seismic facies. Stratigraphic control was available from 32 coring sites. In the central study area, unit 3 represents rhythmic layers of silt with fine sand and clay in an overall fining-upward 3 to 5-m-thick sequence. At the rim of the basin, the unit comprises fine sand, silt and rhythmic layers of silt with clay and fine sand. Unit 3 is proposed as having formed, partly in contact with during the transgression of a lake. the Baltic Ice Lake, some time between 10.8-10.0 C-14 ka BP. After 10.0 C-14 ka BP the water body stagnated when contact with the Baltic Basin was cut off. Analysis of base level of the subunits implies tectonic activity resulting in subsidence of the central study area which could possibly have influenced the transgressive development. (Less)