Provenance of Plio–Pleistocene sediments of the Subei Basin, East China with implication for proto-Yangtze channelization

Abstract

As one of the main depocenters in East China, the Subei Basin (SBB) is crucial for understanding the evolution of the Yangtze River. This study utilises analysis of zircon chronology and heavy minerals on the SBB strata, to gain new insights of the sediment provenance related to the proto-Yangtze River since the late Pliocene. The findings reveal different patterns of provenance evolution during the Plio–Pleistocene between the northern and southern SBB. In the southern SBB, two distinct patterns of zircon age spectra are observed in the late Plio–Pleistocene strata, with changes from a single-peak mode of Mesozoic ages in the late Pliocene strata, to a multi-peak mode in the early Pleistocene strata. Meanwhile, heavy mineral assemblages change correspondingly from epidote–limonite–ilmenite to amphibole–limonite–ilmenite. However, the zircon age spectrum and heavy minerals of the upper Pliocene strata in the northern SBB resemble those of the lower Pleistocene strata in the southern SBB. These observations suggest varying sources of sediment between the northern and southern SBB during the late Pliocene and a unified source during the Pleistocene. During the late Pliocene, the southern SBB primarily accumulated sediments from local sources, including the surrounding areas and the lower reaches of the Yangtze River. Concurrently, the northern SBB began receiving sediments from the upper Yangtze. The provenance evolution implies a connection between the proto-Yangtze River and SBB, at least during the late Pliocene, followed by a southward migration of the river channel towards the modern Yangtze River Delta, which is associated with regional tectonic subsidence.