The Holocene history of the southwestern Baltic Sea as reflected in a sediment core from the Bornholm Basin

Abstract

A study of changes in siliceous microfossil assemblages and chemical analyses in a well‐dated offshore sediment core from the Bornholm Basin, southwestern Baltic Sea, is carried out with the objective of increasing knowledge of the Holocene history of the area. The core covers about 11300 calendar years from the brackish phase of the Yoldia Sea stage to the present. The first weak marine influence in the Ancylus Lake stage is recorded about 10100 cal. yr BP (c. 8900 14C BP), indicating a complex transition to the Litorina Sea with different phases of brackish‐water inflow. The lithology, organic carbon content and C/N and C/S ratios indicate no major changes in the sedimentary environment during the Litorina‐Post‐Litorina Sea stages. A high productivity event recorded in the Post‐Litorina Sea stage around 950 cal. yr BP correlates with the Medieval warm event. A biostratigraphical change indicating a colder climate is recorded in the sediment at about 800 cal. yr BP, which might mark the beginning of the Little Ice Age.

Holocene diatom biostratigraphy of the SW Gulf of Gdańsk, Southern Baltic Sea (part III)

“…On the basis of ecological group contents and lithology it is presumed that environmental conditions were much more stable in the area of core 7/2001. Noticeable fluctuations within habitat and halobian groups in core 2/2001 might either result from successive Littorina transgressions, previously mentioned in the literature (Witkowski 1994, Andrén et al 2000, that were documented only in the shallower part of the Gulf of Gdańsk, or from climate change influencing the scale of the Vistula River inflow. More riverine diatoms were observed in 2-I than in 7-II DAZ.…”

“…Littorina flora has also been documented in Hel Peninsula sediments (Schulz 1926, Bohr & Sokół 1972, BogaczewiczAdamczak 1982, Bogaczewicz-Adamczak & Żukowska 1990. The most characteristic diatoms of the Littorina Sea stage, such as Thalassionema nitzschioides, Pseudosolenia calcar-avis and Rhizosolenia hebetata f. hebetata (Ignatius & Tynni 1978, Witkowski 1994, Snoeijs 1999, Andrén et al 2000, Witak 2000, Witak & Bogaczewicz-Adamczak 2006, Witak & Dunder 2007 were seen in both investigated assemblages. Nevertheless, their percentage content was much lower than that reported in other parts of the Gulf of Gdańsk (Witkowski 1994, Stachura-Suchoples 1999, Witak & Dunder 2007.…”

Relative sea-level changes and development of the Hiiumaa Island, Estonia, during the Holocene

“…The Mastogloia Sea has been rec og nized be tween the fresh wa ter Ancylus Lake and the brack ish-wa ter Litorina Sea as a tran si tional di a tom-strati graphic unit (Kessel and Pork, 1974;Cker et al, 1988;Hyvärinen et al, 1988Hyvärinen et al, , 1992Haila et al, 1991) based on the pres ence of weakly brack ish-wa ter di atom as sem blages par tic u larly in the lit to ral se quences (Hyvärinen, 1984(Hyvärinen, , 2000, whereas in the off shore se quences such a tran si tional unit is com monly ab sent (Ignatius et al, 1981). Lately, this sub-stage was re named Early (Ini tial) Litorina Sea, mark ing pen e tra tion of sa line wa ter to the BSB about 9800-8500 cal yr BP (Andrén et al, 2000;Berglund et al, 2005;Harff et al, 2011). The slightly brack ish-wa ter di a toms oc cur in the sed i ment se quences of Fin land since 8800 cal yr BP (Eronen, 1974), and about 8500 cal yr BP in west ern Es to nia (Hyvärinen et al, 1988).…”

Holocene environmental changes during transition Ancylus-Litorina stages in the Gdansk Basin, south-eastern Baltic Sea

“…Numerous studies gave results, that saline water of the North Sea reached the Ancylus Lake in the beginning of the Middle Но1осеnе, when the Danish Straits were formed (Andrén et al 2000b;Berglund et al 2005). There were several strong inflows of saline water into the lake.…”