Planktic14C Plateaus: A Result of Short-Term Sedimentation Pulses?

Abstract

AbstractThe tuning of plateaus in glacial and deglacial planktic radiocarbon records to pertinent structures in the atmospheric14C record of Lake Suigetsu results in both a record of surface water reservoir ages and a centennial-scale absolute age model. However, the atmospheric origin of planktic14C plateaus may be questioned. Alternatively, plateaus may result from short pulses of increased hemipelagic sediment deposition, which challenges the technique of14C plateau tuning. To test the two rationales for the interval 23–12 cal ka, we calculated hypothetical sedimentation rates for all14C plateaus identified in five Atlantic sediment cores assuming sediment pulses that either span 10, 100, 200, or 300 yr each. These rates were compared to rates derived by14C plateau tuning that assumes an atmospheric origin of the plateaus. In each plateau suite, our hypothetical sedimentation rates result in at least one or two cases in extreme values that exceed the rates reported for short-lasting pulses of sediment deposition in contourites by a factor of 50 and therefore appear unrealistic. Moreover, they result in entire suites of plateau structures that incidentally appear closely aligned to the pattern of atmospheric14C plateau suites rather than to any pulses of climate-controlled sediment discharge.