Lipid biomarkers are stable organic biosignatures, at geological time scales, that are frequently used as paleoenvironmental proxies [1,2]. Although these biomarkers are commonly reported in marine and terrestrial environments, the source of lipids in subterranean ambients are poorly understood [3]. They can be the result of subsurface microbial activity or vegetation biomass from overlying surface soils [2]. The goal of this work was the assessment of lipid molecules preserved in silicious speleothems in different lava tubes from Lanzarote Island (Spain). The presence of lipid biomarkers was evaluated in 6 speleothem samples from 5 different volcanic caves. n-Alkane homologous series was directly analyzed by analytical pyrolysis (Py-GC/MS), monitoring the m/z 85 single ion. Fatty Acid Methyl Esters (FAMEs) characterization was performed by gas chromatography (GC/MS) techniques after the acidification, derivatization, and purification of the extractable organic matter (EOM). Bulk isotopic signature of light elements (δ13C and δ15N) was measured by an isotope ratio mass spectrometer coupled to an elemental analyzer (EA/IRMS). The characteristic distribution of n-alkanes, with a prevalence of short C chain length (20), which may confirm a relative significant contribution of aboveground fresh vegetation material [1]. The contribution of surface biomass is supported by the significant lowest δ15N and δ13C values, in range of C3 plants [4]. The molecular signatures of lipidlike compounds can be helpful for the search of potential traces of present and past live and their environmental adaptation.

This work was funded by the Spanish Ministry of Science and Innovation – MICINN, through TUBOLAN project (ref. PID2019-108672RJ-I00). The Portuguese Foundation of Science and Technology – FCT, is also acknowledge (MICROCENO project, ref. PTDC/CTA-AMB/0608/2020). Vera Palma acknowledges the support from the Research Scholarship for Master within the scope of the project MICROCENO, ref. PTDC/CTA-MB/0608/2020

Comunicación oral presentada en el XX Meeting of the Spanish Society of Chromatography and Related Techniques SECyTA2021. Virtual edition, 18-19 November, 2021

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