Avulsion of the Yellow River into the South Yellow Sea during the early to middle Holocene: Evidence from Clay Provenance of the Yangtze Paleovalley

The location of the Yellow River estuary controls the pattern of mud dispersal and therefore influences the ecology of China's marginal seas. However, little is known regarding the Holocene history of Yellow River avulsion. The Yangtze estuary, south of the Yellow River estuary, may provide some clues, as a large amount of Holocene sediments has accumulated in a major paleovalley in this area, incised during the Last Glacial Maximum (LGM). In this paper, we identify clay contributions from the Yellow River in the three Holocene cores (TZ, DY, and HM) of the Yangtze estuary using provenance analogues of clay geochemistry associated with the modern rivers, and reveal the history of Yellow River avulsion into the South Yellow Sea. The results show that clay geochemistry in the Holocene cores is similar to that of the Yangtze River, except for the period of ∼9.5–7.0 cal. kyr B.P. when it is represented by lower element contents more closely similar to those of Yellow River clays. Provenance end-member analysis shows 40%–60% clays of the Yangtze paleovalley was derived from the Yellow River during this period. These findings indicate that, at least, one channel of the Yellow River avulsed southward into the South Yellow Sea during the early to middle Holocene (∼9.5–7.0 cal. kyr B.P.). Fine-grained sediments from the Yellow River paleoestuary could be transported southward to the Yangtze paleovalley by enhanced marine energy during the early to middle Holocene. This study, not only, provides new evidence for Yellow River avulsion in the Holocene, but also sheds light on the impact of the Yellow River sediments on the depositional system along the coast of China, especially in the Yangtze delta.