Status report of the Heidelberg Radiocarbon Laboratory: Precision and application in Mauritanian cold-water corals over the last 30,000 years

Abstract Highly precise and reproducible radiocarbon ( 14 C) measurements are regularly performed at the Heidelberg Institute for Environmental Physics, Heidelberg, Germany, in collaboration with the radiocarbon laboratory of the Curt-Engelhorn-Center Archaeometry in Mannheim, Germany. Here, we report an update of the technical details, focusing on the analysis of cold-water corals (CWC), and present an improved long-term blank value with a mean of (0.190 ± 0.064) pMC (n = 138) and excellent reproducibility of the IAEA-C2 standard with a mean of (41.15 ± 0.16) pMC (n = 75), consistent with its certified consensus value. Furthermore, 33 duplicates of the CWC 14 C measurements agree within 2σ, 85% even within the 1σ range. This provides excellent conditions for accurate 14 C measurements. As an application example, we present combined 230 Th/U and 14 C ages of a coral-bearing sediment core from the upper Mauritanian slope. The resulting ventilation age record confirms decreasing ventilation between 30 and 25 kyr BP, most likely reflecting a northward propagation of a water mass originating from the south. During the LGM, we confirm a previously hypothesized southward displacement of the Cap Verde Frontal Zone. With the onset of the deglaciation, our record documents again an advance of a southern-sourced water mass into the subtropical North Atlantic. During the Bølling-Allerød warm period, strong ventilation fluctuations possibly indicate temporal influence of southern-sourced water.