Origin and fate of branched tetraether lipids in river drainage systems: Implications for the use of the MBT/CBT proxy as a continental palaeothermometer in marine sedimentary records

Abstract: Branched tetraethers (brGDGTs) are membrane lipids of still unknown bacteria mainly found in soil, which can adapt to changing environmental conditions. Earlier research showed that the temperature and pH of soil are the main influence on the distribution of nine different brGDGTs. It was investigated if brGDGTs from eroded soil, which are deposited in marine sediment close to a river mouth can be used to reconstruct river basin temperature and pH. Two river systems were studied in detail the Amazon River and Tagus River. It was found that this hypothesis is complicated by the fact that brGDGTs are also produced in river water and in the marine environment. Therefore, this method can only be used for river systems that have a strong input of soil organic matter and in marine sediment cores that are under strong influence of a river.