Sedimentary characteristics and facies model of wave-controlled delta-turbidity fan in the Eocene Wenzhou Formation in the Lishui Sag of the East China Sea Shelf Basin

Lishui Sag is an important oil and gas exploration area in the East China Sea Shelf Basin. To accelerate the exploration of lithologic traps in the shallow Eocene Wenzhou Formation, we analyzed new three-dimensional seismic and geological data in sequence stratigraphy theory, by which the sequence stratigraphy of the Wenzhou Formation was divided into three third-order sequences, i.e., SQ1, SQ2, and SQ3. Among them, SQ1 developed typical lowstand, transgressive, and highstand system tract, SQ2 developed transgressive system tract and highstand system tract. There are obvious differences between seismic reflection termination relations and seismic facies in each system tract. Moreover, the sedimentary plane distribution of the SQ1 tracts was anatomized. SQ1 lowstand domain system was a delta and turbidity fan featuring sedimentary microfacies indicative of delta front shore sandbars and thin limestone shoals, based on which the sedimentary model of wave-controlled delta turbidity fan was established. This study clarified the distribution characteristics and formation mechanism of the wave-controlled delta-turbidity fan sedimentary system in the Eocene Wenzhou Formation, in order to provide reference for searching lithological traps.