TY - JOUR
T1 - A 200-300 year cyclicity in sediment deposition in the Gotland Basin, Baltic Sea, as deduced from geochemical evidence
AU - Kunzendorf, H.
AU - Larsen, B.
N1 - Funding Information:
This study profited very much by part funding from the EU MAST Programme and the good overall coordination of the project by Dr. C. Fragakis, EU DGXII, B. von Bodungen, IOW Warnemünde, Germany, and Dr. B. Winterhalter, Geological Survey of Finland, is greatly acknowledged. During the sampling and analytical steps P. Sørensen, Risø, carried out skilful work and we thank him for this.
Funding Information:
During the past years there has been renewed focus on the Baltic Sea. Not only because the Baltic is one of the world's largest estuarine systems but also because the area is of focal importance for 15 countries as a transportation channel, recreational area and fishing ground. The Baltic Sea area's advantage when planning scientific work is that it is relatively easily accessible. The fact that the Baltic Sea has been studied for many years and that a new political situation has been established since 1989 with new possibilities for international cooperation, were the basis for a new effort to include the Baltic Sea seafloor into a multidisciplinary project. A large Regional Seas project of 3-a duration, the Baltic Sea System Study (BASYS), was funded by the EU Marine Science and Technology Programme (starting in 1996).
PY - 2002/1
Y1 - 2002/1
N2 - During the EU funded project BASYS (Baltic Sea System Study) short (Niemistö-type) and long (box and piston cores) sediment cores were taken which cover sedimentation during the past 8 ka. The uppermost part of the sedimentary sequence was chosen for a detailed geochemical study and freeze dried samples were analysed for about 20 elements but only the elements Mn and Ca are discussed. An age model was constructed using radiometric dating results by
210Pb/
137Cs and
14C AMS. Significant correlation exists along the cores between very high Mn and moderately high Ca due to occrrences of the mineral rhodochrosite (kuthnahorite), a complex Mn(Ca) carbonate. This mineral is thought to be produced when salt water meets the pool of dissolved Mn at the bottom of the Gotland Basin. During favourable hydrographic conditions, e.g. strong northwesterly winds, salt water from the North Sea invades even the deepest parts of the central Baltic. Mn
2+ which is produced mainly by the dissolution of ferromanganse oxides/oxyhydroxides in the water colum and in the course of destruction of organic matter in the sediments, combines with HCO
3
2- and Ca
2+ in the seawater to form rhodochrosite. After burial, this mineral stays in the sediment and is seen as light-coloured layers. A certain cyclicity in the upper 1.5 m of the cores was observed in that about 200-300 a periods of elevated Mn - Ca are followed by periods with lower Mn - Ca of similar duration. An explanation for the observed cyclicity may be sea level variations: during rising sea level (transgression) more and more saline water is pushed into the deep basin of the Baltic Sea and if conditions are favourable (high dissolved Mn) the mineral rhodochrosite is precipitated.
AB - During the EU funded project BASYS (Baltic Sea System Study) short (Niemistö-type) and long (box and piston cores) sediment cores were taken which cover sedimentation during the past 8 ka. The uppermost part of the sedimentary sequence was chosen for a detailed geochemical study and freeze dried samples were analysed for about 20 elements but only the elements Mn and Ca are discussed. An age model was constructed using radiometric dating results by
210Pb/
137Cs and
14C AMS. Significant correlation exists along the cores between very high Mn and moderately high Ca due to occrrences of the mineral rhodochrosite (kuthnahorite), a complex Mn(Ca) carbonate. This mineral is thought to be produced when salt water meets the pool of dissolved Mn at the bottom of the Gotland Basin. During favourable hydrographic conditions, e.g. strong northwesterly winds, salt water from the North Sea invades even the deepest parts of the central Baltic. Mn
2+ which is produced mainly by the dissolution of ferromanganse oxides/oxyhydroxides in the water colum and in the course of destruction of organic matter in the sediments, combines with HCO
3
2- and Ca
2+ in the seawater to form rhodochrosite. After burial, this mineral stays in the sediment and is seen as light-coloured layers. A certain cyclicity in the upper 1.5 m of the cores was observed in that about 200-300 a periods of elevated Mn - Ca are followed by periods with lower Mn - Ca of similar duration. An explanation for the observed cyclicity may be sea level variations: during rising sea level (transgression) more and more saline water is pushed into the deep basin of the Baltic Sea and if conditions are favourable (high dissolved Mn) the mineral rhodochrosite is precipitated.
UR - http://www.scopus.com/inward/record.url?scp=0036146052&partnerID=8YFLogxK
U2 - 10.1016/S0883-2927(01)00088-9
DO - 10.1016/S0883-2927(01)00088-9
M3 - Article
SN - 0883-2927
VL - 17
SP - 29
EP - 38
JO - Applied Geochemistry
JF - Applied Geochemistry
IS - 1
ER -