Headward incision of large rivers in response to glacial sea level fall

Abstract

Sea level change is an important forcing on lowland fluvial systems. Although its impact is suggested to extend up to hundreds of kilometers inland, this impact is often considered confined to deltaic regions. We present luminescence dating of cores from the Jianghan Plain in the middle Yangtze River that demonstrates the influence of the last glacially driven sea level fall extended over 1000-kilometers inland. Luminescence ages reveal a common sedimentary hiatus from ~26 to ~17 thousand years ago (ka), reflecting fluvial incision of >35 meters triggered by sea level fall. Subsequent rapid aggradation occurred within these incised valleys during deglaciation between ~17 and ~9 ka and then slowed down afterward. A further synthesis on global continental rivers shows that sea level change affects large, low-gradient lowland fluvial systems farther upstream than generally recognized, with postperturbation geomorphologic equilibrium reachable in timescales comparable to the length of Quaternary glacial cycles.