Shell beds and trace fossils of the Seogwipo Formation (Early Pleistocene), Jeju Island, Korea

Shell beds containing characteristic trace fossils of the Early Pleistocene Seogwipo Formation represent a storm‐influenced succession. They generally consist of: (1) initial firmground substrates in foreshore to offshore environments as indicated by the Glossifungites ichnofacies, including Gastrochaenolites and Thalassinoides, (2) basal storm‐erosive lag deposits, (3) reworked shell beds of main storm deposits, (4) massive sandstone of waning storm deposits containing Skolithos, and (5) bioturbated sandstones of post‐storm offshore deposits indicated by the Cruziana ichnofacies that include Chondrites, Helminthopsis, Laminites, Phycodes and Thalassinoides. This succession of shell beds reflects a gradational decrease in hydraulic energy levels induced by storms. Trace fossils including Gastrochaenolites lapidicus, Helminthopsis ichnosp., Laminites ichnosp. Thalassinoides cf. paradoxica and T. cf. suevicus are systematically described from shell beds of the Seogwipo Formation