Did the modern Yellow River form at the Mid-Pleistocene transition?

现代黄河水系在中更新世气候转型早期形成?

The incision of the Sanmen Gorge marks the birth of the modern Yellow River,but its timing varies from the late Miocene-early Pliocene to the late Pleistocene(~0.15 Ma),and the suggested forcing mechanisms vary from the uplift of the Tibetan Plateau to global climate change.Here,we report sedimentologic,geochronologic,and provenance data from a drill core near the Sanmen Gorge,the last gorge along the main course of the Yellow River.Our results indicate that typical river channel deposits,with detritus from the Ordos Block in the upstream regions,started to accumulate in the Sanmen Gorge at~1.25 Ma.When integrated with river terrace evidence from the upstream and downstream regions,the results provide robust evidence that the final integration of the modern Yellow River occurred at~1.25 Ma,consistent with the beginning of the Mid-Pleistocene transition(MPT).We propose that the accelerated lowering of eustatic sea level during the MPT may play as important a role as tectonism in driving the birth and evolution of the modern Yellow River.

黄河贯通三门峡东流入海是现代黄河水系格局形成的重要标志,但对其形成时代尚存晚中新世-早上新世到晚更新世的不同认识.三门峡是黄河的最后一个峡谷,该地区的沉积记录能为约束现代黄河水系的形成时代提供最直接的地质证据.本文对三门峡盆地中部的钻孔岩芯开展了系统的年代学、沉积学和物源分析.研究结果表明:1.96~1.25 Ma,三门峡盆地以封闭性咸水/微咸水湖沉积为主,沉积物主要来源于盆地周边的中条山、秦岭等近源山体,无上游鄂尔多斯地块的碎屑物质输入;自约1.25 Ma起,典型的河流沉积物开始大规模发育,鄂尔多斯地块的碎屑物质大量涌入,表明黄河中游水系开始连通,现代黄河水系形成.黄河贯通三门峡的时代与中更新世气候转型期全球海平面的加速降低有较好的一致性,暗示全球海平面变化对现代黄河水系的形成演化有重要影响,其贡献可能与中上游地区的构造运动同等重要.