Origin, architecture, and paleoecology of the early Eocene continental ichnofossilScaphichnium hamatum— integration of ichnology and paleopedology

Abstract

Ichnofossils and alluvial paleosols from the lower Eocene Willwood Formation of the Bighorn Basin in northwest Wyoming documents the origin and paleoecology of the ichnofossil Scaphichnium hamatum as well as provide insight on changes in paleosol hydrology and development through time. In the Willwood Formation, 5. hamatum occurs as a discrete hamate (hook‐shaped) to lunate meniscate burrow with a lower bulbous termination in assemblages that range from a few to hundreds of individuals. The burrows are concentrated within the Bg horizon (gleyed B horizon) of hydromorphic paleosols representing distal floodplain settings. Until recently, the architect responsible for its construction was unknown. Comparisons with modern examples of insect nests and burrows suggests that the architect of S. hamatum was a beetle of the family Scarabaeidae and that nest construction occurred during periods characterized by relatively dry soil conditions and lowered water tables. Interpretations of the trace fossil succession,...