POST-GLACIAL MARINE TERRACES ON SAN JUAN ISLAND, WASHINGTON: A PRODUCT OF MULTIPLE MELTWATER PULSES 1A

Exposure ages were obtained for twelve till boulders from the Cattle Point moraine on San Juan Island, WA, USA. Five of these samples were collected from a pair of wave-cut terraces, which were incised during periods when the isostatic recovery rate was comparable to eustatic sea level rise. Be-10 dating indicates that the terraces' ages both fall within the time interval constrained by existing dates for Meltwater Pulse 1A. Because eustatic sea level rise and isostatic uplift rates would only correspond during a period of catastrophic ice-sheet downwasting described by a meltwater pulse, the data thus imply that Meltwater Pulse 1A comprised at least two distinct episodes of enhanced flow, thus allowing reconciliation of the diverse distribution of dates derived from corals and other sources for this event.