First year of routine measurements at the AWI MICADAS 14C dating facility.


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Torben.Gentz [ at ] awi.de

Abstract

In November 2016, the first Mini-Carbon-Dating-System (MICADAS) manufactured by Ionplus AG was delivered and installed at the Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research (AWI), Germany. After one year of establishing the instrument and preparation methods, we started routine operation for scientific purposes in January 2018. The new facility includes a graphitization unit (AGE3) connected to an elemental analyser (EA) or a carbonate handling system (CHS), and a gas inlet system (GIS). The facility at AWI focuses on analysing carbonaceous materials from samples of marine sediments, sea-ice, and water to investigate various aspects of the global carbon cycle. A particular emphasis will be on sediments from high-latitude oceans, in which radiocarbon-based age models are often difficult to obtain due to the scarcity of carbonate microfossils (e.g., foraminifera). One advantage of the MICADAS is the potential to analyse samples as CO2 gas, which allows radiocarbon measurements on samples containing as little as 10 µgC. For example, it is possible to determine 14C ages of foraminifera from carbonate-lean sediments allowing paleoclimate reconstructions in key locations for the Earth’s climate system, such as the Southern Ocean. Likewise, compound-specific 14C analyses receive growing attention in carbon cycle studies and require handling of small samples of typically <100 µgC. The wide range of applications including gas analyses (e.g., foraminifera and isolated compounds), and graphite targets require establishing routine protocols for various methods including sample preparation and precise blank assessment. We report on our standard procedures for dating organic matter from sediments or water including carbonate removal, combustion and graphitization using the AGE3 coupled to the EA, as well as on the methodology applied for carbonate samples using the CHS system and the GIS. We have investigated different sample preparation protocols and present the results using international standard reference materials (e.g., IAEA-C2 F14C = 0.4132 + 0.0052 (n= 14); Ref = 0.4114 + 0.0003). Additionally, we present the first results of process blanks for sediments (Eocene Messel shale F14C= 0.0007; equivalent to an conventional 14C age of > 52000yr (n=29)), as well as Eemian foraminifera (F14C = 0.005; equivalent to an conventional 14C age of >42700yr (n=98)). We are also presenting results of samples processed and analysed as graphite and directly as gas showing a good reproducibility irrespective of the method used.



Item Type
Conference (Poster)
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Not peer-reviewed
Publication Status
Published
Event Details
23rd International Radiocarbon Conference, 17 Jun 2018 - 22 Jun 2018, NTNU.
Eprint ID
47557
Cite as
Gentz, T. , Bonk, E. , Hefter, J. , Grotheer, H. and Mollenhauer, G. (2018): First year of routine measurements at the AWI MICADAS 14C dating facility. , 23rd International Radiocarbon Conference, NTNU, 17 June 2018 - 22 June 2018 .


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