Geochemical response on redox fluctuations in Holocene lake sediments, Lake Steisslingen, Southern Germany

摘要: Abstract Holocene sediments of Lake Steisslingen record sedimentation under different redox conditions. This is proven by the changing depth chemocline and resulting varying extension laminated from deepest part lake to shallower water depths. Redox fluctuations are additionally reflected colour changes between red green quality nonglacial varves. Major trace elements were analysed on bulk sediment samples (period 8200–6200 2650–2000 cal a BP) test their response observed in past depositional environments. Mn, Mo, U, Fe S found be redox-sensitive Steisslingen. almost entirely fixed pyrite, because pyrite formation limited availability. A parallel distribution 8200–7200 BP interpreted as signal for syngenetic anoxic sulfidic hypolimnetic waters. Since bioproductivity was low this must have been caused conditions favouring longterm stable stratification (i.e. high level, summer temperatures, ice cover, wind protection and/or storm activity). Between 6000–2000 frequently dysoxic assumed. Mo U curves mirror images Fe, Mn variations. showing diagenetic pore waters, which enhanced during times availability rather oxygenated conditions, i.e. when input oxy-hydroxides possible, but cannot necessarily sediments. Changes slightly disturbed lamination (dysoxic, restricted mixis) homogenous (oxic holomixis) traced within geochemical record. The 6000 2000 not correlated bioproductivity, detrital or cultural influences therefore natural, probably climatic origin. North Atlantic Oscillation discussed possible cause.