Reimer, Andreas

[["dc.bibliographiccitation.firstpage","195"],["dc.bibliographiccitation.issue","1-2"],["dc.bibliographiccitation.journal","Aquatic Geochemistry"],["dc.bibliographiccitation.lastpage","222"],["dc.bibliographiccitation.volume","15"],["dc.contributor.author","Reimer, Andreas"],["dc.contributor.author","Landmann, Guenter"],["dc.contributor.author","Kempe, Stephan"],["dc.date.accessioned","2018-11-07T08:32:53Z"],["dc.date.available","2018-11-07T08:32:53Z"],["dc.date.issued","2009"],["dc.description.abstract","Saline, 450-m-deep Lake Van (Eastern Anatolia, Turkey) is, with 576 km(3), the third largest closed lake on Earth and its largest soda lake. In 1989 and 1990, we investigated the hydrochemistry of the lake's water column and of the tributary rivers. We also cored the Postglacial sediment column at various water depths. The sediment is varved throughout, allowing precise dating back to ca. 15 ka BP. Furthermore, lake terrace sediments provided a 606-year-long floating chronology of the Glacial high-stand of the lake dating to 21 cal. ka BP. The sediments were investigated for their general mineralogical composition, important geochemical parameters, and pore water chemistry as well. These data allow reconstructing the history of the lake level that has seen several regressions and transgressions since the high-stand at the end of the Last Glacial Maximum. Today, the lake is very alkaline, highly supersaturated with Ca-carbonate and has a salt content of about 22 g kg(-1). In summer, the warmer epilimnion is diluted with river water and forms a stable surface layer. Depth of winter mixing differs from year to year but during time of investigation the lake was oxygenated down to its bottom. In general, the lake is characterized by an Na-CO(3)-Cl-(SO(4))-chemistry that evolved from the continuous loss of calcium as carbonate and magnesium in the form of Mg-silica-rich mineral phases. The Mg cycle is closely related to that of silica which in turn is governed by the production and dissolution of diatoms as the dominant phytoplankton species in Lake Van. In addition to Ca and Mg, a mass balance approach based on the recent lake chemistry and river influx suggests a fractional loss of potassium, sodium, sulfur, and carbon in comparison to chloride in the compositional history of Lake Van. Within the last 3 ka, minor lake level changes seem to control the frequency of deep water renewal, the depth of stratification, and the redox state of the hypolimnion. Former major regressions are marked by Mg-carbonate occurrences in the otherwise Ca-carbonate dominated sediment record. Pore water data suggest that, subsequent to the major regression culminating at 10.7 ka BP, a brine layer formed in the deep basin that existed for about 7 ka. Final overturn of the lake, triggered by the last major regression starting at about 3.5 ka BP, may partly account for the relative depletion in sulfur and carbon due to rapid loss of accumulated gases. An even stronger desiccation phase is proposed for the time span between about 20 and 15 ka BP following the LGM, during which major salts could have been lost by precipitation of Na-carbonates and Na-sulfates."],["dc.description.sponsorship","DFG [395/2-(1-4)]; Volkswagen Foundation"],["dc.identifier.doi","10.1007/s10498-008-9049-9"],["dc.identifier.isi","000264831200008"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?goescholar/3576"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/17440"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","1380-6165"],["dc.rights","Goescholar"],["dc.rights.uri","https://goescholar.uni-goettingen.de/licenses"],["dc.title","Lake Van, Eastern Anatolia, Hydrochemistry and History"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","107"],["dc.bibliographiccitation.issue","1-4"],["dc.bibliographiccitation.journal","Palaeogeography, Palaeoclimatology, Palaeoecology"],["dc.bibliographiccitation.lastpage","118"],["dc.bibliographiccitation.volume","122"],["dc.contributor.author","Landmann, Günter"],["dc.contributor.author","Reimer, Andreas"],["dc.contributor.author","Lemcke, Gerry"],["dc.contributor.author","Kempe, Stephan"],["dc.date.accessioned","2020-05-05T14:25:39Z"],["dc.date.available","2020-05-05T14:25:39Z"],["dc.date.issued","1996"],["dc.description.abstract","In summer 1990, during the third international expedition to Lake Van, eastern Anatolia, 10 sediment cores were retrieved from depths up to 446 m. As reported earlier, the sediments of the lake are finely laminated. The seven cores, recovered up to 30 km apart in the main lake basin, presented sediment sequences which correlate well with respect to ash layers and prominent colour changes, but also lamina for lamina. Here we report on the detailed evaluation of this record, which is varved continuously back to 14,570 yr B.P. (calendar years before 1950 AD). It is independent of 14C calibration, i.e. it is not a floating record, and it is the only detailed varve chronology known from the semi-arid Mediterranean region. Important Late Glacial events, such as the termination of the Oldest and Younger Dryas are clearly recorded in the sediments. Chronozones were defined on the basis of changes of the deposition rate and of chemical composition caused by environmental changes. Analysis of the annual deposition rates revealed abrupt changes within only a few years, declining for example by approximately 30% in the transition period between the Oldest Dryas and the Bølling. In most cases, alterations observed in the sedimentation rates are reflected in changes of the geochemical parameters, such as organic and inorganic carbon, opal, and the major elements Si, Ca, Mg, Al. Our results and palynological studies, performed on material recovered in an earlier expedition, are used to reconstruct palaeoenvironmental conditions. In this study, the termination of the Younger Dryas is dated to 10,920±132 yr B.P. This is younger than the recently published Greenland ice core dates but in accordance with, for example, the central European dendrochronology. We suspect, that higher sediment deposition rates during the cold periods are due to rapid melting and intense wash out of soil, which was fairly loose because of sparse vegetation. This would lead to higher river discharges. Based on the observed increase of the deposition rate in the record, melting of glaciers can only be detected after the termination of the Younger Dryas."],["dc.identifier.doi","10.1016/0031-0182(95)00101-8"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/64844"],["dc.language.iso","en"],["dc.relation.issn","0031-0182"],["dc.title","Dating Late Glacial abrupt climate changes in the 14,570 yr long continuous varve record of Lake Van, Turkey"],["dc.type","journal_article"],["dc.type.internalPublication","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","156"],["dc.bibliographiccitation.lastpage","166"],["dc.contributor.author","Kempe, Stephan"],["dc.contributor.author","Kazmierczak, Jozef"],["dc.contributor.author","Reimer, Andreas"],["dc.contributor.author","Landmann, Günter"],["dc.contributor.author","Reitner, Joachim"],["dc.contributor.editor","Tomascik, Tomas"],["dc.date.accessioned","2020-05-05T14:26:32Z"],["dc.date.available","2020-05-05T14:26:32Z"],["dc.date.issued","1997"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/64846"],["dc.language.iso","en"],["dc.publisher","Oxford University Press"],["dc.relation.isbn","0-19-850186-2"],["dc.relation.isbn","962-593-163-5"],["dc.relation.ispartof","The Ecology of the Indonesian Seas"],["dc.title","Satonda: a porthole view into the oceanic past"],["dc.type","book_chapter"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","797"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Global Biogeochemical Cycles"],["dc.bibliographiccitation.lastpage","808"],["dc.bibliographiccitation.volume","10"],["dc.contributor.author","Landmann, Günter"],["dc.contributor.author","Reimer, Andreas"],["dc.contributor.author","Kempe, Stephan"],["dc.date.accessioned","2020-05-05T14:25:54Z"],["dc.date.available","2020-05-05T14:25:54Z"],["dc.date.issued","1996"],["dc.description.abstract","Sediment core K10 from Lake Van (eastern Turkey) provides a continuous varve record back to 14,570 calendar years B.P. (before present, 1950), the longest unbroken and nonfloating lake varve sequence yet described. The underlying sediment is unvarved and hard. Changes in the aragonite/calcite ratio, the presence of protodolomite and magnesite in certain profile sections, the annual record of the sedimentation rate, the water content of the sediment, the concentrations of organic carbon and opal, and the texture of the sediments from this core provide a record of the lake level history. The new chronology enabled us to redate the old pollen profile [van Zeist and Woldring, 1978a, b] and to establish an accurate timescale for the reconstructed lake level change. Carbon 14 dates show that the highest lake terrace corresponds to high lake level at around 19,000 years B.P. during the Last Glacial, >70 m above its present level. Before 15,000 years B.P. the lake must have been completely dry, marking a reduction of lake level by 500 m in maximum 4000 years. Beginning at 14,600 years B.P. and ending at 12,040 years B.P., the lake level recovered by 250 m to fall again during the next 1400 years. By 10,600 years B.P. the lake began to rise and reached, following another regression between 9000 and 8100 years B.P., the Holocene highstand by about 7500 years B.P., dropping to today's level at about 3000 years B.P."],["dc.identifier.doi","10.1029/96GB02347"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/64845"],["dc.language.iso","en"],["dc.relation.issn","0886-6236"],["dc.title","Climatically induced lake level changes at Lake Van, Turkey, during the Pleistocene/Holocene Transition"],["dc.type","journal_article"],["dc.type.internalPublication","no"],["dspace.entity.type","Publication"]]