2004: The influence of cesium activity on the annual dose for OSL dating

Abstract: Abstract: Abstract: Abstract: Abstract: Introduction of single aliquot protocols dramatically improved the accuracy of absorbed dose measurements, so now dating of very recent events, which ages are of the order of tens of years or even single years, becomes possible. The overall accuracy of the OSL age is now limited by the correct assignment of the dose rate. Certain types of recent sediments may contain fall-out radioisotopes that increase the average annual dose. In this paper we demonstrate that the contribution from fall-out radioactivity may be significant and the way to take it into account by using a modified age equation

Seasonal dynamics of stable isotopes and element ratios in authigenic calcites during their precipitation and dissolution, Sacrower See (northeastern Germany)

The seasonal evolution of chemical and physical water properties as well as particle fluxes was monitored in Sacrower See (northern Germany) during two consecutive years (Oct 2003 - Oct 2005). Additonally, we measured delta O-18 and delta C-13 as well as Sr:Ca and Mg:Ca ratios of authigenic calcites that were collected in sequencing sediment traps in order to disentangle environmental and climatic factors controlling these parameters. In particular, our aim was to find out if element ratios and the isotopic composition of calcites reflect changes, in water and air temperatures. Lake water is highly enriched in O-18 (-1.3 to -2.5%. VSMOW) with an evaporative increase of 0.6 parts per thousand during summer. Values are 5-6 parts per thousand more positive than groundwater values and 4-5 parts per thousand more positive than long-term weighted annual means of precipitation. During spring and summer, high amounts of dissolved phosphate cause eutrophic conditions and calcite precipitation in isotopic disequilibrium. Measured values are depleted in 180 by 2 to 10 parts per thousand compared to calculated equilibrium values. Resuspension and partial dissolution of calcite in the water column contribute to this isotopic divergence in summer and autumn as delta O-18(ca) and delta C-13 values increased in the hypolimnion during this time. Mg:Ca and Sr:Ca ratios are altered by dissolution as well. In the hypolimnion these ratios were higher than in the epilimnion. Another reason for the huge deviation between measured and theoretical delta O-18(ca) values during summer is the occurrence of large amounts of Phacotus lenticularis in the carbonate - fraction. High amounts of Phacotus lead to more negative delta O-18(ca) and more positive delta C-13 values. Several characteristics of delta O-18(ca) and delta C-13 are also reflected by Mg:Ca and Sr:Ca ratios and isotopic composition of oxygen and carbon were influenced by the onset and stability of stratification. Especially the earlier onset of stratification it? 2005 caused higher sediment fluxes and more positive carbon and oxygen isotope values of bioinduced carbonates compared to 2004

Trace element analysis of climate archives by laser ablation ICP-MS

The analysis of the inorganic composition of climatic archives provides proxies for climate reconstruction. For many applications commercially available inductively coupled plasma quadrupole mass spectrometry (ICP-Q-MS) systems are used for investigations. In this talk I will present different application possibilities of the laser ablation (LA)-ICP-Q-MS analysis of different sample matrices.Polar ice cores:Ice from polar regions is an archive of climate. The analysis of element signatures in ice cores yields information about the strength of sources and transport mechanisms for aerosols in the paleoatmosphere as well as about the paleovolcanism. An ice core section from the Holocene, drilled in the Atlantic sector of Antarctica, was analysed by LA-ICP-Q-MS with a spatial resolution of about 4 mm. The analysis of sea salt tracers, mineral dust tracers and tracers for other natural or anthropogenic sources revealed in general enhanced element concentrations during winter months. The ice core included a tephra horizon which source could be identified by the element composition.Bivalves:During the past 10 years, the enhanced input of sediments due to accelerated glaciermelting is observed in Potter Cove at the Antarctic Peninsula. The analysis of the Antarctic soft shell clam Laternula elliptica (Potter Cove, Antarctic Peninsula) by LA-ICP-Q-MS addressed whether the increased sediment input is reflected in the distribution of Fe, and other elements (Al, Mn, Cu, Pb and U) in the ultimate growth bands, which are formed in bivalve umbos. In contrast to our hypothesis, we proved that the accretion of our investigated elements into the umbo matrix is largely a function of animal ecophysiology and life history rather than of climate change.Frozen lake sediment cores:A frozen lake sediment core from Sacrower See (Potsdam Germany), investigated by LA-ICP-Q-MS, showed annual lamination until a depth of 42.7 cm. Our study targeted to settle the question whether the lamination results in varying elemental signature that corresponds to summer and winter layers, with respectively high and low biological activity. The enrichment or depletion of a certain element in a sample relative to the average composition of the Earths crust is expressed as the enrichment factor (EF). From the increased EF of Ca and Sr in the summer layers, we conclude an increased biological activity

Climate-driven shifts in diatom assemblages recorded in annually laminated sediments of Sacrower See (NE Germany)

Sacrower See is a eutrophic lake with annually laminated sediments extending back to A.D. 1868. Analysis of annual layers revealed multi-decadal periods of distinct diatom assemblages at A.D. 1868-1875, 1876-1940, 1941-1978, and 1979-2000. Detrended correspondence analysis performed on individual seasonal sediment layers showed decadal-scale patterns of turnover in the diatom flora. The spring-summer layers showed higher sample scores until the early 1960s, after which the differences with the autumn-winter layers became smaller. Rates-of-change analysis revealed that the seasonal variability in diatom assemblages was higher than the annual changes. Summer diatom rates of change over the period A.D. 1894-1960 was on average higher than for winter, whereas between the 1960s and 1970s the winter rates of change became higher than the summer ones. Redundancy Analyses showed that seasonal temperatures and wind strength were significant explanatory variables for diatom assemblages in both annual and seasonal layers. These results suggest that meteorological changes indirectly affected diatom assemblages via the mixing regime of the lake. A comparison of the diatom rates of change with the amplitude of inter-annual climate change shows a statistically significant correlation for the spring-summer layers in the period of A.D. 1963-2000, showing that the sensitivity of diatom assemblages to meteorological changes has varied over the past century, with a stronger effect on diatoms registered during the past 40 years

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Luminescence dating of the Volochysk section : a key Podolian loess site (Ukraine)

The Volochysk site belongs to important and unique loess sites in the Podolia Upland (W Ukraine) because it contains relatively well-developed loess deposits representing the last and penultimate glacial cycles. This loess-palaeosol sequence consists of pedocomplex S1 (MIS 5) developed on loess L2, and loess L1 (MIS 4-2) with the palaeosols of lower, interstadial rank. In this sequence, different periglacial structures were found, including the largest ones of ice-wedge cast type. Different quartz and polymineral fractions separated from the samples collected in the Volochysk site were dated using luminescence methods (SAR OSL, post-IR IRSL and TL) in three Polish luminescence laboratories in Gdańsk, Gliwice and Lublin. In total, 69 luminescence dating results were obtained for 18 samples. The methodological and research aims were to carry out mutual verification of the obtained dating results as well as to analyse and interpret the differences between them, and to determine the age of distinguished deposit layers and the period of cryogenic activities. The luminescence dates of the sediments, which were deposited during MIS 2, 3 and 4, corresponded fairly well to the ages attributed to these stages. They also indicate the age of periglacial phenomena. However, the TL dates were generally older than the OSL ones, especially those obtained for the sediments deposited during MIS 5 and 6. The results of the research of the Volochysk sequence were compared with those obtained in past years for the loess deposits of the Volhynian Upland (north of Podolia) during similar inter-laboratory analyses conducted to determine their age. The results of OSL datings of the older deposits (MIS 5 and MIS 6) are underestimated irrespective of the used method, and the type (quartz, polymineral) and size of grains. Numerous attempts were made to explain this phenomenon, which, however, give no answer. It was only found that this underestimation corresponded to the equivalent dose value of ~150 Gy