Environmental controls on branched tetraether lipid distributions in tropical East African lake sediments

摘要: Abstract Quantifying past continental temperature changes is an important aspect of paleoclimate research as it allows us to constrain the amplitude natural variability, test predictive climate models, and provide a proper context for that may arise in response anthropogenically-induced change. The recently developed biomarker-based methylation index branched tetraethers/cyclization ratio tetraethers (MBT/CBT) proxy shows potential new method reconstruction, but thus far has only been applied successfully ocean margin sediments. To assess whether this also applicable sedimentary record tropical lacustrine systems, we investigated distribution glycerol dialkyl (GDGTs) deposited sediments from 46 lakes East Africa. These span substantial range surface elevation (770–4500 m above sea level), wide gradient mean annual temperature. We find that, saline excepted, GDGTs are universally abundant can be used predict air (MAAT) with high degree accuracy. However, existing global MBT/CBT calibration MAAT based on soils predicts inaccurate temperatures when our African lake dataset. This observation, together fact water pH, lesser extent, depth appear influence among sites, leads conclude situ production likely. robust relationship between GDGT pH freshwater makes these compounds suitable paleoenvironmental however urge caution using infer temperatures, unless their exact origin determined.