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The Interactions of Volcanism and Clastic Sedimentary Systems in Rift Basins: An Example From the Paleogene Bohai-Bay Basin, China


Abstract: The interactions of volcanism and clastic sedimentary systems are still a relatively underexplored topic in rift basins. Previous studies have set up numerous high-resolution sedimentary models in nonvolcanic rift basins, but seldom consider the influences of volcanism on clastic sedimentary systems in the volcanic rift basins. This study builds on well-based sedimentology and seismic-based geomorphology in Paleogene rift strata of Bohai-Bay Basin to investigate the interactions of volcanism on the dispersal of clastic sedimentary systems in the syn-rift and post-rift stages. SLT Uplift and surrounding depressions contain a syn-rift succession > 2 km thick and post-rift succession > 500 m that deposited in 5-20 km-wide grabens. Four volcanic inter/intra-eruptive units in temporal and five volcanic systems in spatial are identified and consider controlled by the main faults. Volcanism mainly supplies volcanic clasts, fills the lower topography and forms mounded volcanic dams in rift basins. A generic model is devised that concludes the influences of volcanism on clastic sedimentary systems in rift stages. In the syn-rift stage, a considerable amount of volcanic sediments fills and smooths the lower topography within rift segments, thus resulting in a shallow basin and increasing the connectivity between isolated depocenters. Also, the input of volcanic clasts in a short period triggers the slumping and sliding sediments in front of fan deltas/braided-river deltas. In the post-rift stage, on the relatively flat topography, the mounded landscape which formed by volcanic eruptions and intrusions mainly hinders the dispersal of the axial fluvial/deltaic systems, resulting in splitting/shifting of sedimentary systems. With the input of volcanic clasts, sedimentary systems occur as “muddy” fluvial/deltaic systems with a relatively large area. Keywords: volcanic facies; depositional systems; sediments supplement; landscape; rift basin.