Grain Size Associations of Branched Tetraether Lipids in Soils and Riverbank Sediments: Influence of Hydrodynamic Sorting Processes

We analyzed the abundance and distribution of branched glycerol dialkyl glyceroltetraethers (brGDGTs) in grain size fractions of 7 globally distributed river flank sedimentsand catchment soils in order to determine if and how the initial soil-brGDGT signatureis influenced by hydrodynamic sorting upon entering a river and during subsequenttransport from land to sea. BrGDGTs are hypothesized to form associations withhigh-surface-area fine-grained minerals in soils. Such associations, if maintained duringtransport, may impart resistance to degradation and promote downstream transport,reducing potential interferences by aquatic brGDGTs. We find that brGDGTs a re indeedprimarily associated with organic carbon (OC) bound t o the clay-silt fraction (