The Baltic Ice Lake in the southwestern Baltic: sequence‐, chrono‐ and biostratigraphy

Abstract

1997 (September): The Baltic Ice Lake in the southwestern Baltic: sequence-, chrono-and biostratigraphy. fkJrcWS, Vol. 26, pp,[217][218][219][220][221][222][223][224][225][226][227][228][229][230][231][232][233][234][235][236] This multidisciplinary study focuses on late-glacial deposits in the Mecklenburg Bay -Arkona Basin area. The sequence stratigraphical method has been used on shallow seismic and lithological data, in combination with biostratigraphical work and radiocarbon dating. Glacial-till deposits underlie sediments from two Baltic Ice Lake phases. Varved clay deposits from the initial phase cover the deepest parts of the basins. A prograding delta is observed at the western margin of the Arkona Basin, prograding from the Darss Sill area. The delta system is possibly related to a highstand dated at 12.8 ka. A maximum transgression level around 20 m below present sea level (b.s.1.) is inferred, followed by a drop in water level and formation of lowstand features. The final ice lake phase is characterized by a new transgression. The transgression maximum as observed in the Mecklenburg Bay is represented by transgressive and highstand deltaic deposits. These also indicate a maximum shore level of 20 m b.s.1. The deltaic scdiments that contain macroscopic plant remains and diatoms have yielded Younger Dryas ages. Mapping of the late-glacial morphology of the Darss Sill area reveals a threshold at 23 to 24 ni b.s.1. This means that the Baltic Ice Lake highstand phases inundated the Darss Sill, which implies that the westernmost extension of the Baltic Ice Lake reached as far as Kiel Bay. Forced regressive coastal deposits at the western margin of the Arkona Basin mark a lowstarid level of around 40 m b.s.1. caused by the final drainage of the Baltic Ice Lake. The lowstand deposits predate lacustrine deposits from the Ancylus Lake, which date to approximately 9.6 ka BP.

Timescales for the development of methanogenesis and free gas layers in recently-deposited sediments of Arkona Basin (Baltic Sea)

“…In this study, we assume that the initial HORM deposition in the southwestern Baltic Sea began 8.0 kyr BP (Jensen, 1995;Jensen et al, 1997Jensen et al, , 1999Witkowski et al, 2005). This date is consistent with the averaged date for the Littorina Sea Stage in the Baltic Sea given by Gustafsson and Westman (2002) if one considers this event in Arkona Basin preceded the averaged date for the Baltic Sea by 500 yr. Figure 2 shows a general overview of the two most recent stages of the Baltic Sea and the chronostratigraphy employed in the model.…”

“…(1) The Baltic Ice Lake stage beginning roughly 13.5 kyr before present (BP) as a result of deglaciation (Jensen, 1995;Jensen et al, 1997). During this stage, evidence points toward probable drainage of Arkona Basin waters through Øresund ( Fig.…”

Diatoms as a proxy in reconstructing the Holocene environmental changes in the south-western Baltic Sea: the lower Rega River Valley sedimentary record

“…Fritz et al, 1999) and freshwater inflow into the coastal (estuarine/lagoonal) systems (Starratt, 2007). A somewhat different situation is found in newly deglaciated areas in which leaching of the solutes can cause a distinct increase in water mineralization which can be reconstructed from diatom assemblages (Jensen et al, 1997). The latter situation was quite common in the Baltic Sea basin after the Vistulian ice sheet retreat and as a result carbonate rich lacustrine deposits originated (Marciniak, 1981;Jensen et al, 1997).…”

“…Diatom analysis has also been applied to studies of shallow water and lagoon deposits, e.g. Przybyłowska-Lange (1974, 1979, Jensen et al (1997), Witkowski et al (2004Witkowski et al ( , 2005, Yu et al (2005), Berglund et al (2005), Janczak- Kostecka & Kostecki (2006). The major aim of these diatom analyses was to document changes in environmental variables.…”

Evolution of Arkona Basin environment in the Holocene in the light of diatom research

“…These fluctuations completely changed the existing ecosystems, which had to adapt to new environmental conditions. Since the 1990s, complex interdisciplinary studies concerning the reconstruction of the sea level and salinity of the Baltic Sea in the Holocene have been carried out in the Arkona Basin area (Jensen et al 1997, Lemke et al 2001, Witkowski et al 2005. These studies determined the maximal extent of the Baltic Ice Lake, which flooded the Arkona Basin during its high level at 10 300 cal BP.…”