Regressions and transgressions of the Baltic basin reflected by a new high‐resolution deglacial and postglacial lithostratigraphy for Arkona Basin sediments (western Baltic Sea)

Abstract

2002 (June): Regressions and transgression s of the Baltic basin re ected by a new high-resolutio n deglacia l and postglacia l lithostratigraphy for Arkona Basin sediments (western Baltic Sea). Boreas, Vol. 31, pp. 151-162. Oslo. ISSN 0300-9483.Seismoacoustic pro les from the Arkona Basin show a late Pleistocene and Holocene successio n of several distinct re ectors. The physical , sedimentological , mineralogical and geochemica l propertie s of more than 30 sediment cores were analysed in order to assign these re ectors to speci c sedimentar y discontinuit y layers. Additionally , AMS 14 C data and biostratigraphi c information were gathered . Based on this multi-proxy approach, seven lithostratigraphi c units (AI, AII, B to F) were distinguished . These consist of ne-grained clay, silt and mud, and are separate d from each other by thin basin-wide traceable sandy layers (S ab -S ef ). The most sensitive parameter to mark the lithostratigraphi c boundarie s is the weight percentag e of the grain-siz e fraction >63 mm. In addition, some of the quartz-grain-dominate d sandy layers cause the strong re ection lines recorded in seismoacousti c pro les. The sandy layers are interpreted to re ect enhanced hydrodynami c energy induced by episodes of basin-wide water-level low-stand conditions. These low stands resulted from waterlevel drops that occurred frequentl y during the Baltic Sea's history and presumably affected the entire Baltic basin. The thick ne-graine d units AI, AII to F, in which coarser material is absent, represen t water-level high-stands . We conclude that the units AI and AII are Baltic Ice Lake sediments deposite d before and after the Billingen-1 regression , respectively . We assign the most prominent sandy layer S ab to the nal drainage of the Baltic Ice Lake (Billingen-2) , whereas the sandy layers between units B, C, D and E are related to the Yoldia Sea and Ancylus Lake regression s of the Baltic Sea's history. The uppermost ne-grained unit F with its high organic carbon content contains marine sediments deposite d after the Littorina Transgression . The macroscopicall y well-visible sediment colour change from reddish/brown-to-grey , previousl y interprete d as a regional stratigraphi c boundary, varies from core to core. It has been shown by our new data that this colour change has a diagenetic origin, and thus does not represent a stratigraphi c boundary. Previous subdivision s therefore have to be revised.

Stages of the Baltic Sea evolution in the geochemical record and radiocarbon dating of sediment cores from the Arkona Basin

“…and, despite possible re-deposition, could be interpreted as coastal sediments deposited after the final regression of the Baltic Ice Lake (Moros et al 2002). This date is consistent with other similar dates determined in this area (Lampe 2005) and with the assumption that the water level during the early Preboreal Chronozone was at 25 m b.s.l.…”

“…The above-described composition reflected the dominance of mineral deposition with an input of organic detritus presumably due to re-deposition from flooded land areas and transported during the Ancylus regression into deeper parts of the basin. Similar sediments of terrestrial origin of organic material deposited with coarse mineral material were also identified previously in the Arkona Basin (Moros et al 2002) and the Bornholm Basin .…”

“…Changes in the geochemical composition confirmed that the environment changed rapidly from the freshwater Ancylus Lake into the marine Littorina Sea as it was described in the previous studies (Emelyanov and Vaikutienė 2013, Kostecki and Janczak-Kostecka 2012, Moros et al 2002. The increasing content of loss on ignition, biogenic silica reflected an increase in the primary production that was stimulated by an inflow of saline, oxygenated water enriched with nutrients.…”

“…The onset of marine environment in the Gdańsk Basin was dated at around 7600 cal BP (Emelyanov and Vaikutienė 2013). The youngest date of 7200 cal BP was found in the Arkona Basin (Moros et al 2002, Rößler et al 2011. The problem of age discrepancy was described by Kortekaas et al (2007) and Rößler et al (2011) where bulk 14 C ages, 14 C ages of macrofossils and OSL ages of marine sediment were compared.…”

“…Billingen in the south of Sweden (Björck 1995). The age of the first regression of the Baltic Ice Lake was estimated at 12 800 cal BP in the Allerød (Moros et al 2002). After the final regression of the Baltic Ice Lake, the connection with the North Atlantic was established.…”