Age determination and median grain size of sediment core EN31-PC2

We believe these episodes represent megaflood deposits reflecting historically unprecedented outfall of North American floodwater and terrigenous mud plumes into the gulf, resulting in collapse of the open-ocean pelagic ecosystem.

The deposits record multidecadal episodes of high continental precipitation and large Mississippi River floods at ~4.7, 3.5, 3.0, 2.5, 2.0, 1.2, and 0.3 cal ka (500-1200-year recurrence interval). Variations in tropical plankton frequencies define submillenial warming intervals that culminate in these fluvial episodes. Strengthened tropical currents in the gulf at these times appear to have increased sea surface temperatures and associated flow of moist gulf air to the midwest.