Plio‐Pleistocene Establishment of Irtysh River in Junggar, Northwest China: Implications for Siberian‐Arctic River System Evolution and Resulting Climate Impact

The influence of Siberian freshwater input to the Arctic Ocean on Northern Hemisphere ice-sheet expansions remains poorly known due to the incomplete geologic record of Siberian-Arctic river systems during the late Pliocene. The Irtysh River is a major Siberian river, rising from the Altay Mountains, northwestern China, and flowing 4,282 km before joining the Ob River. Here, we present new field evidence and chronological data from a combination of cosmogenic 21Ne and 26Al/10Be measurements that constrain the establishment of the Irtysh River to ca. 2.77+0.39/-0.33 Ma. These first quantitative chronological results, together with previous sedimentological, geomorphological, and geochemical evidence, support a young Siberian-Arctic river system. Its coincidence with the late Pliocene ice-sheet expansions in the Northern Hemisphere implies a profound impact of Siberian freshwater input to the Arctic on the major ice advances that significantly affected global oceanographic and climatic systems