LAUSR

Abstract The study of drainage evolution in the Songnen Plain, Northeast China, is essential for understanding the interactions between tectonics-topography-climate-drainage evolution in the region. Despite this, it remains unclear whether the paleo-Songhua River (upper-middle reaches of the Songhua River) once flowed westward into the Songnen Plain and what forcings influenced the drainage development of the Songnen Plain. In this contribution, we provide insight into drainage development on the Songnen Plain using an integrated approach of magnetic susceptibility, geochemical (elemental and Sr Nd isotopic) and heavy mineral composition recovered from a 102-m sediment core sediments extracted from the eastern edge of the Songnen Plain with sedimentological and topographic archives. Our results show that a dramatic provenance shift occurred at the depth of 62.2 m (~0.94 Ma) in the core sediments. It is proposed that the Songhua River was separated by the Jia-Yi (Jiamushi-Yilan) divide into two segments before ~0.94 Ma, the west-flowing proto-Songhua River and the east-flowing proto-Sanjiang River (lower reach of the Songhua River). However, the proto-Songhua River reversed direction at ~0.94 Ma when the Jia-Yi divide was cut through by headward erosion of the proto-Sanjiang River, marking the birth of the Songhua River as a single, eastward-flowing river system. Tectonics is suggested as the first-order control on the evolution of the Songhua River before 1.20 Ma, whereas climate changes may be responsible after 1.20 Ma.