Trace fossils from marginal lacustrine deposits of the Cretaceous Jinju Formation, southern coast of Korea

Abstract

Trace fossils from the Cretaceous Jinju Formation of the south coast of Korea occur in interbedded medium- to fine-grained sandstone of a moderate-energy lake shoreface, and mudstone–shales of a periodically exposed low-energy shallow lake, and interfingerings of both of the above. The trace fossils are represented by Beaconites antarcticus, Beaconites coronus, Cochlichnus anguineus, Diplichnites ( Octopodichnus) cf. didactylus, Diplichnites type A, Diplichnites isp., Helminthopsis hieroglyphica, Palaeophycus sulcatus, Palaeophycus tubularis, Planolites annularis, Planolites beverleyensis, Protovirgularia dichotoma, Skolithos magnus, Taenidium barretti, and sauropod tracks. The Diplichnites specimens are among the first arthropod trackways recorded from the Cretaceous. Two of the four trackway-bearing ichnocoenoses present in the study area are considered representative of composite ichnofacies. Sinusoidal burrows or trails and simple irregular interface burrows or trails probably formed in wet, possibly submerged, soupground–softground conditions in low- or medium-energy lake margins, and represent the Mermia ichnofacies. Trackways and meniscate burrows probably formed on the subsequently subaerially exposed lake margins following lake regression and represent an overprinting by the Scoyenia ichnofacies. The other two trackway-bearing ichnocoenoses are from the Scoyenia ichnofacies alone.