FATTY ACID AND N-ALKANE ASSEMBLAGES IN MODERN TERRESTRIAL AND AQUATIC PLANTS FROM LAKE JUNIN, PERU AND THEIR APPLICATION TO THE SEDIMENTARY BIOMARKER RECORD OVER THE LAST 18,700 YEARS

Leaf wax hydrogen isotopes offer the potential to reconstruct hydroclimate change by recording distinct precipitation and evaporation signals from terrestrial and aquatic biomarkers. Application of this proxy is complicated by biosynthetic differences in hydrogen isotope fractionation among plant functional types and lipid classes, as well as environmental influences. The analysis of leaf waxes in modern plants can identify which compounds may provide reliable isotopic signals of meteoric precipitation and evaporation. Here, we present the n-alkane and fatty acid distributions and abundances in a collection of terrestrial and aquatic plants from Lake Junín, Peru, and in sediments spanning the last 18,700 years. This evaporatively-influenced lake in the central Andes is located in the core South American monsoon region, and is well suited for exploring the application of leaf waxes because carbonate minerals precipitated during interglacials can provide an independent record of lake water oxygen isotope values. Results indicate which chain lengths can provide reliable precipitation and evaporation signals in sediments, and future work will focus on developing a hydrogen isotope calibration for downcore application through several glacial/interglacial cycles.