Late Holocene climate and environmental history based on biomarker analyses from Lake Tislit, Morocco

The High Atlas in Morocco is sensitive to climate change and influenced by both the subtropical and mid-latitude atmospheric circulation systems, making it a key region for paleoclimate and -environmental research. Here, we present first results of lipid biomarker analyses on a ~2 m sediment core from Lake Tislit, covering approximately the last 1500 years at 30-year temporal resolution. Specifically, we aim to apply compound-specific hydrogen isotope analyses (δ²H) on n-alkanes to investigate past changes in the hydrological cycle. Further, polycyclic aromatic hydrocarbons (PAHs) are used as a proxy for paleofires. This combined approach allows us to explore the interactions between hydrological variability and (anthropogenic) fire activity during the Late Holocene.

Our preliminary results indicate that n-alkanes (n-C₂₃ - n-C₃₃) are well preserved with an odd-over-even predominance of >7. n-C₂₉ and n-C₃₁ are the most abundant homologues (~1 μg g^-), likely reflecting input from terrestrial plants. Short-chain n-alkanes (n-C₂₃ and n-C₂₅), likely derived from aquatic organisms, are also abundant (~0.25 μg g^-), providing a reliable basis for compound-specific δ²H analyses. Therefore, we will run these measurements in the coming weeks to investigate paleohydrological changes.

PAHs are consistently present throughout the sediment core. High molecular weight PAHs (m/z 252 to 278) increase strongly towards the top of the core, reaching almost 1 μg g^-. This is probably indicative of high temperature combustion and the onset of industrialisation. Perylene is considered separately, as it has recently been proposed to rather serve as possible proxy for soil erosion. Perylene is often the most abundant PAH in our core and has a pronounced maximum at ~50 cm core depth, possibly indicating significant anthropogenic land use.