Radiocarbon measurements of small gaseous samples at CologneAMS

A second SO-110 B (Arnold et al., 2010) ion source was installed at the 6 MV CologneAMS for the measurement of gaseous samples. For the gas supply a dedicated device from Ionplus AG was connected to the ion source. Special effort was devoted to determine optimized operation parameters for the ion source, which give a high carbon current output and a high C-14(-) yield. The latter is essential in cases when only small samples are available. Additionally a modified immersion lens and modified target pieces were tested and the target position was optimized. (C) 2017 Elsevier B.V. All rights reserved

Improvements in the measurement of small (CO2)-C-14 samples at CologneAMS

Since 2015, the CologneAMS started operating a second SO-110 B ion source (Arnold et al., 2010; Klein and Mous, 2017) from High Voltage Engineering Europe (HVE) with a gas injection system (GIS) from Ionplus AG (Wacker et al., 2013) for the measurement of gaseous CO2 samples. Significant effort was spent increasing the efficiency of C- ion beam extraction as well as the operational reliability. Details are described in Stolz et al. (2017). Recent work was aimed at prolonging the cleaning intervals and allowing unattended routine (CO2)-C-14 measurements. Problems related to sparking inside the source chamber could be eliminated by electrically shielding the ceramic linear actuator that is used to move the target pieces into the source head. Furthermore, the Cs reservoir temperature was decreased from 135 degrees C to 120 degrees C. The negative ion formation efficiency has dropped only slightly to about 5% with the current settings. Additionally, the GIS sample magazine capacity was doubled to 16 ampules, which enables longer measurements without user interaction. A dedicated software (Gas Injection Control Software, GICS) was developed that controls GIS and AMS hardware for fully autonomous measurements, including the source and accelerator startup, sample cracking or combustion, sample mixing with the He carrier gas and the transfer to the source, as well as the subsequent data analysis. This tool also comprises error detection routines in order to minimize the risk of losing a sample due to hardware failures. The blank value was reduced from typically 7.10(-15) to similar to 3.10(-15). This was achieved by modifications in the cleaning and measurement procedures. Recently a EuroVector EA3000 elemental analyzer (EA) was coupled to the GIS and integrated into the GICS software. First EA test measurements with standards, blanks and tree rings were performed as well as first automated overnight measurements with ampules and EA samples

Cambrian rhynchonelliform nisusioid brachiopods : phylogeny and distribution

A comprehensive review and phylogenetic analysis of genera and species presently assigned to the rhynchonelliform superfamily Nisusioidea and family Nisusiidae suggests that this short-lived but important group of brachiopods first appeared in peri-Gondwana during the second half of the Cambrian Series 2, before going extinct by the end of Drumian times. Nisusiides achieved their maximum morphological disparity and geographical distribution during the Wuliuan Age, and Laurentia was probably the major centre of their dispersal. A new phylogenetic analysis suggests an early separation of the lineages of spinose and non-spinose nisusiids. The non-spinose nisusiids probably evolved in Laurentia by the end of Cambrian Series 4. The new nisusiid genus Bellistrophia is described. The new species Nisusia multicostata represents the first documented rhynchonelliform (kutorginide) brachiopod from the Miaolingian (Drumian) of the Alborz Mountains, Iran

Marine Carbon-Sulfur Biogeochemical Cycles during the Steptoean Positive Carbon Isotope Excursion (SPICE) in the Jiangnan Basin, South China

Global occurrences of Steptoean Positive Carbon Isotope Excursion (SPICE) during Late Cambrian recorded a significant perturbation in marine carbon cycle, and might have had profound impacts on the biological evolution. In previous studies, SPICE has been reported from the Jiangnan slope belt in South China. To evaluate the bathymetric extent of SPICE, we investigate the limestone samples from the upper Qingxi Formation in the Shaijiang Section in the Jiangnan Basin. Our results show the positive excursions for both carbonate carbon (delta C-13) and organic carbon (delta C-13(org)) isotopes, as well as the concurrent positive shifts in sulfur isotopes of carbonate associated sulfate (CAS, delta S-34(CAS)) and pyrite (delta S-34(pyrite)), unequivocally indicating the presence of SPICE in the Jiangnan Basin. A 4 parts per thousand increase in delta C-13(carb) of the Qingxi limestone implies the increase of the relative flux of organic carbon burial by a factor of two. Concurrent positive excursions in delta S-34(CAS) and delta S-34(pyrite) have been attributed to the enhanced pyrite burial in oceans with extremely low concentration and spatially heterogeneous isotopic composition of seawater sulfate. Here, we propose that the seawater sulfur isotopic heterogeneity can be generated by volatile organic sulfur compound (VOSC, such as methanethiol and dimethyl sulfide) formation in sulfidic continental margins that were widespread during SPICE. Emission of S-32-enriched VOSC in atmosphere, followed by lateral transportation and aerobic oxidation in atmosphere, and precipitation in open oceans result in a net flux of S-32 from continental margins to open oceans, elevating 8345 of seawater sulfate in continental margins. A simple box model indicates that about 35% to 75% of seawater sulfate in continental margins needs to be transported to open oceans via VOSC formation.Natural Science Foundation of China [41272017, 41322021]SCI(E)中国科学引文数据库(CSCD)[email protected]