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MC-ICP-MS has become the clearly dominant technology in 230Th/U-dating over the last 20 years. The ongoing increase in measurement performance allows for ε-precision by now (Andersen et al., 2004; Cheng et al., 2013) and enabled the production of a large amount of datasets and insights covering a broad range of fields. Despite this large database, systematic studies on the impact of individual corrections on the raw data, long-term instrumental stability and on data processing routines are still sparse. We present the measurement and data analysis protocols developed and applied at the Institute for Environmental Physics at Heidelberg University and examine the contribution of individual corrections, such as tailing and hydride correction, to the total uncertainties of the atomic ratios 230Th/238U and 234U/238U and of the ages for this procedure. As demonstration examples, three different speleothem samples of different U and Th concentrations and ages were chosen. This puts specific quantitative constraints on general findings as the dominance of tailing correction. Long-term instrumental stability is examined by compiling a multi-year dataset of (230Th/238U) and (234U/238U) for the Harwell-Uraninite 1 (HU-1) reference material of more than thousand measurements which is then used for the recalibration of the inhouse 229Th, 233U and 236U spike. Lastly, we present a Python-based GUI for the combined evaluation of mass-spectrometric data and age determination that offers high flexibility with regard to the variation of input constants, such as the initial (230Th/232Th) used for detritus correction.

In this study, the dead carbon fraction (DCF) variations in stalagmite M1-5 from Socotra Island in the western Arabian Sea were investigated through a new set of high-precision U-series and radiocarbon (14C) dates. The data reveal an extreme case of very high and also climate-dependent DCF. For M1-5, an average DCF of 56.2±3.4 % is observed between 27 and 18 kyr BP. Such high DCF values indicate a high influence of aged soil organic matter (SOM) and nearly completely closed-system carbonate dissolution conditions. Towards the end of the last glacial period, decreasing Mg∕Ca ratios suggest an increase in precipitation which caused a marked change in the soil carbon cycling as indicated by sharply decreasing DCF. This is in contrast to the relation of soil infiltration and DCF as seen in stalagmites from temperate zones. For Socotra Island, which is influenced by the East African–Indian monsoon, we propose that more humid conditions and enhanced net infiltration after the Last Glacial Maximum (LGM) led to dense vegetation and thus lowered the DCF by increasing 14CO2 input into the soil zone. At the onset of the Younger Dryas (YD) a sudden change in DCF towards much higher, and extremely variable, values is observed. Our study highlights the dramatic variability of soil carbon cycling processes and vegetation feedback on Socotra Island manifested in stalagmite DCF on both long-term trends and sub-centennial timescales, thus providing evidence for climate influence on stalagmite radiocarbon. This is of particular relevance for speleothem studies that aim to reconstruct past atmospheric 14C (e.g., for the purposes of 14C calibration), as these would rely on largely climate-independent soil carbon cycling above the cave.

By resolving small structures the wavelength must have the same order of magnitude as the structure itself. Today’s research focuses on the analysis of substructure of the size about 1/1000 the diameter of the proton that is 1 fm or 10−15 m. Due to the Heisenberg uncertainty principle a very large momentum for forcing the particles to approach each other very closely is needed.

In this thesis the measurement protocols and data corrections for U-series dating with the highest achievable precision on a MC-ICP mass spectrometer are described. U and Th isotope ratios of sample solutions with high [U] and [Th] above 6 ppt can be measured reproducibly on a 6 ε-scale (ε = 1·10−4). U and Th isotope ratios of sample solutions with moderate [U] and [Th] are routinely determined with 8 to 18 ε-precision. Results from measurements on various mass spectrometers were reproducible within their uncertainties, confirming the credibility of our dating results. Using high-resolution dating, the beginning of the penultimate deglaciation at the Spannagel Cave (Northern Alps) was dated delayed by 2,000 a at 133,183 ± 833 a BP achieving a higher precision of 400 a compared to formerly published results. This age interval is broadly coincident with the rise in boreal summer insolation and seems more concordant to Milankovitch hypothesis. Furthermore, the growth rates of two stalagmites from adjacent caves in the Swiss Alps were compared on a resolution of Δt = 220 a in the last 6,500 a. Both growth rates show individual growth histories, however when combined with a tree-line record, provide additional insights into the local vegetation history.

High-precision U-series dating of scleractinian cold-water corals is a key chronological tool for studies of past environmental and climate conditions. Here, we tested and optimized an automated chemical extraction system (ESI prepFAST-MC equipped with an Eichrom TRU-resin chromatographic column) for its ability to purify U and Th isotopes for mass spectrometric U-series dating at the sub-‰ precision level. Chemical yields are constantly high, on average around 90% for both U and Th. Analytical blanks are comparable to manual purification (< 0.15 pg U, 0.15 pg Th for a typical sample of 50 mg) and memory effects due to the recycling of the column are mostly insignificant as the carry-over fraction is about 10− 5 for Th and 10− 3 for U isotopes. However, it was found that the built-in UTh (TRU-resin) column must be pre-conditioned for analysis using > 1 μg g− 1 Th and U in order to achieve the above mentioned chemical yields. This conditioning has no impact on the Th/U data. The automated chemical preparation protocol described here is compared to conventional high precision U-series dating with manual sample purification. For the 34 cold-water corals extracted from a sediment core collected from a coral mound off Angola, the differences between 230Th/238U- and 234U/238U-ratios and U-series ages measured with the two analytical methods are smaller than the respective analytical uncertainty of < 3.0‰, 0.8‰ and 3.0‰, respectively. Overall, ages of the studied corals span 34,000 years and perfectly meet quality control constrains, such as initial seawater δ234U0. Finally, our record of coral ages indicates vigorous coral growth under warm and cold climate conditions in the temperate south-eastern Atlantic, contrasting climate influenced coral occurrences in the north-eastern Atlantic., Chemical Geology, 475, ISSN:0009-2541, ISSN:1872-6836