Palaeoenvironmental reconstruction of Northern Spain during the last 8000 cal yr BP based on the biomarker content of the Roñanzas peat bog (Asturias)

We determined the lipid distributions (n-alkanes, n-methyl ketones, n-alkanoic acids, 5-n-alkyl resorcinols and sterols) and total organic carbon (TOC) content in a 2.0 m deep Sphagnum-dominated ombrotrophic peat bog in Northern Spain. From this, we inferred the changes in plant distribution (Sphagnum- vs. non-Sphagnum-dominated), which was related to palaeohydrological and palaeoenvironmental conditions, during the last 8000 cal yr BP. From n-alkane proxies, 10 dry/humid episodes were distinguished: five dry episodes alternating with five humid episodes, the transitions from dry to humid periods not necessarily being linked to changes in temperature. These transitions were found to correlate well with global environmental episodes and are consistent with other Spanish records. Our results suggest that the n-alkane carbon preference index (CPI) could be related to degradation rates linked to variation in temperature rather to changes in the amount of precipitation, whereas the 5-n-alkyl resorcinol/sterol ratio could reflect the abundance of sedges.