Dinosaur egg-bearing deposits (Upper Cretaceous) of Boseong, Korea: occurrence, palaeoenvironments, taphonomy, and preservation

Dinosaur (sauropod and ornithopod) egg-bearing deposits of the Upper Cretaceous Seonso Conglomerate, Boseong, Korea were examined sedimentologically for palaeoenvironmental and preservational interpretation. Dinosaur eggs are commonly preserved as clutches, although isolated eggs also occur. The clutches are found in at least six horizons consisting of sandy mudstones to mudstones. These strata are interpreted as terminal fan deposits. Calcite rims and calcite aureols around detrital grains, pedotubular to nodular calcretes, and circumgranular to circumnodular cracks are present in the dinosaur egg deposits. These features indicate calcareous pedogenesis which appears to have assisted in the preservation of the eggs. In one egg deposit, in which clutches are mostly found, vertic features including pedogenic slickensides, pseudoanticlines, and calcite-filled deep desiccation cracks occur. The preservation of these dinosaur eggs in calcic and vertic palaeosols suggests that the palaeoclimate of the nested area was semiarid. The lack of displacement of eggs and egg shells, the presence of some egg clutches 5–10 cm below flood deposits, and the porous nature of the eggshells suggest that the eggs were laid in excavated nests that were buried during incubation. The preservation of numerous dinosaur clutches in several horizons at Boseong is consistent with site fidelity.