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 glycerol tetraethers (brGDGTs) in grain size fractions of 7 globally distributed river flank sediments and catchment soils in order to determine if and how the initial soil-brGDGT signature is influenced by hydrodynamic sorting upon entering a river and during subsequent transport from land to sea. BrGDGTs are hypothesized to form associations with high-surface-area fine-grained minerals in soils. Such associations, if maintained during transport, may impart resistance to degradation and promote downstream transport, reducing potential interferences by aquatic brGDGTs. We find that brGDGTs are indeed primarily associated with organic carbon (OC) bound to the clay-silt fraction (