Syn-rift to post-rift tectonic transition and drainage reorganization in continental rifting basins: Detrital zircon analysis from the Songliao Basin, NE China

Tectonic transition from a syn-rift stage to subsequent post-rift stage is an important mechanism in the evolution of extensional basins. The sedimentary infill records the crustal response to this process. We have obtained new detrital zircon U-Pb and Lu-Hf signatures from the Lower Cretaceous stratigraphic successions encompassing the commonly accepted synto post-rift transition boundary, the T4 unconformity, in the Songliao Basin, NE China. These constrain the Songliao Basin's evolution from its center to distal margins, providing insights into the sediment provenance and dispersal pattern over the tectonic transition. Analysis of zircons from the syn-rift (the Shahezi and Yingcheng formations) and immediate post-rift (the Lower and Middle Denglouku Formation) stages reveals Phanerozoic age populations with positive sigma Hf(t) values, which were derived from the proximal juvenile mantle-derived melt origin bedrocks of the Songliao Block. In contrast, the overlying samples from the Upper Denglouku Formation deposited in the subsequent post-rift stage contain exotic and ancient zircon populations with ages of 2.5 Ga & 1.8 Ga and complex hafnium signatures, characteristic of a mixed origin. These are interpreted to be transported from distant cratonic terranes via larger drainage networks. It is obvious that the sediment dispersal pattern switched from being a local and hydrologically closed intraregional pattern to a transcontinental pattern during the transition. The time lag between the development of the T4 unconformity and the drainage reorganization also ensures a distinguishable-3 Myr (106103 Ma, Late Albian) transition period of regional extent. During this transition stage, syn-rift faulting was replaced by post rift thermal subsidence, exhibiting a uniform sag configuration. Our new findings are important for understanding other continental rift basins during synto post-rift transition, which often demonstrates a complex interaction between the linkage and integration of sub-basins, and the reorganization of fluvial drainages and catchment systems. (C) 2022 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V.

Automated summary

By studying the sedimentary sequences in the Songliao Basin, China, we can understand the evolution of this extensional basin from the syn-rift to subsequent post-rift stages. During this transition, the sediment dispersal pattern shifted from a local intraregional pattern to a transcontinental pattern, resulting in a complex mixture of sediment sources. These findings are important for understanding the evolution of other continental rift basins.