Extreme erosional events recorded by flood deposits in the late quaternary Santa Barbara Basin, coastal southern California

Terrestrial runoff from major storm and flood events in southern California is captured in Santa Barbara Basin (SBB) as distinct gray layers of well-sorted clay to silt that punctuate typical olive-hued hemipelagic mud. Thirty-two partially overlapping piston cores recovered from a breached anticline provide ultra-high resolution windows into a 700,000-year climate record. Frequency, mass accumulation/event, grain size and mineralogy of pre-Holocene gray layer deposits remain remarkably consistent without apparent chronological or climatically related trends. The Holocene record, even in comparison with previous interglacials, contains twice the total mass of gray layer flood deposits, with 60% larger than a destructive 1969 flood event. These deposits reflect increased storm intensity and frequency, more efficient sediment transport, and/or increased terrestrial erosion during the Holocene. Weak correlations with lower-resolution temperature and precipitation records indicate that gray layer flood deposits must have a different forcing mechanism than mean global and regional climate change.