Radiocarbon Dating of Leaf Waxes in the Loess-Paleosol Sequence Kurtak, Central Siberia

Abstract

Loess-paleosol sequences (LPS) are valuable archives for Quaternary climate and environmental changes. So far, LPS are generally dated using luminescence, with ~10% uncertainties, or radiocarbon (14C) analyses in the rare cases that charcoal or macrofossils are available. For this study, we determined 14C ages of leaf waxes (long-chain n-alkanes) extracted from the LPS Kurtak in central Siberia. 14C ages range from 16.7 to 22.9 ka cal BP for the last glacial loess and from 24.5 to 35.3 ka cal BP for the paleosol correlated with marine isotope stage (MIS) 3. Overall, this is in good agreement with independent age control based on stratigraphy, infrared stimulated luminescence (IRSL) dating, and 14C dating on charcoal and macrofossils. However, strong cryoturbation and solifluction seem to have affected the MIS 3 paleosol early during MIS 2. Our results corroborate the stratigraphic integrity of leaf waxes, and highlight their potential for dating LPS back to ~35–40 ka BP. Compared to compound-specific 14C analyses, which are very time-consuming and require specialized instrumentation (gas chromatograph with fraction collector), 14C dating of leaf waxes as a whole compound class is relatively quick and straightforward and warrants further investigation as a chronological tool.

Late Quaternary climate and environmental reconstruction based on leaf wax analyses in the loess sequence of Möhlin, Switzerland

“…orate that radiocarbon analyses of n-alkanes are a promising new tool for dating LPS back to ∼ 30 ka (Häggi et al, 2014;Haas et al, 2017;Zech et al, 2017). Moreover, the stratigraphic integrity and synsedimentary nature of the longchain n-alkanes could be confirmed for the uppermost 6 m. The OSL, IR50 (Gaar and Preusser, 2017) and our radiocarbon ages show that the major part of the sequence was developed between 35 and 30 kyr and that older deposits are probably influenced by erosion.…”

“…Another possibility might be incorporation of root-derived n-alkanes by roots from plants growing after deposition, as suggested, for example, by Gocke et al (2014). But a post-sedimentary production of roots can most probably be excluded, as shown by Häggi et al (2014), and Haas et al (2017).…”

“…Compound-specific radiocarbon analyses on sedimentary n-alkanes is a new tool in geochronology (Häggi et al, 2014;Haas et al, 2017;Zech et al, 2017). It allows us to test the synsedimentary nature, and thus the stratigraphic integrity of leaf waxes, and can complement other dating methods, for example based on luminescence.…”

“…The 14 C measurements were performed on the MICADAS accelerator mass spectrometer, coupled to an element analyzer (Ruff et al, 2010;Salazar et al, 2015), at the LARA AMS Laboratory, University of Bern (Szidat et al, 2014). 14 C results are reported as fraction modern carbon (F 14 C) and were corrected for constant and blank contamination (Salazar et al, 2015;Haas et al, 2017). The blank contamination was 0.4 µg C for a single tin capsule with a F 14 C value of 0.734 ± 0.19.…”

Lipid biomarkers in aeolian sediments under desert pavements – potential and first results from the Black Rock Desert, Utah, USA, and Fuerteventura, Canary Islands, Spain

“…Radiocarbon dating was carried out using accelerated mass spectrometry (AMS) at the University of Bern (Szidat et al, 2014). Results of radiocarbon dating were corrected for constant and cross contamination (Haas et al, 2017). All 14 C ages were calibrated using the Intcal 13 calibration curve (Table 1).…”