An early Holocene sea‐level jump and delta initiation

Abstract

Early Holocene sea‐level change controlled the evolution of clastic coastal depositional systems. Radiocarbon‐dated borehole cores obtained from three incised‐valley‐fill systems in Asia (Changjiang, Song Hong, and Kiso River) record very similar depositional histories, especially between about 9000 and 8500 cal BP. Sedimentary facies changes from estuarine sand and mud to shelf or prodelta mud suggest that the marine influence in the incised valleys increased during this period. In addition, large decreases in sediment accumulation rates occurred. A sea‐level jump causes an estuarine system and its depocenter to move rapidly landward. It is possible that the final collapse of the Laurentide Ice Sheet, accompanied by catastrophic drainage of glacial lakes, at approximately 8500 cal BP caused such a jump. The jump was followed immediately by a period of decelerated sea‐level rise that promoted delta initiation.