Ichnotaxonomy of the Eocene Green River Formation, Soldier Summit and Spanish Fork Canyon, Uinta Basin, Utah: Interpreting behaviors, lifestyles, and erecting the Cochlichnus Ichnofacies

Abstract

The Eocene Green River Formation in the Uinta Basin, Utah, has a diverse ichnofauna. Nineteen ichnogenera and 26 ichnospecies were identified: Acanthichnus cursorius, Alaripeda lofgreni, c.f. Aquatilavipes isp., Aulichnites (A. parkerensis and A. tsouloufeidos isp. nov.), Aviadactyla (c.f. Av. isp. and Av. vialovi), Avipeda phoenix, Cochlichnus (C. anguineus and C. plegmaeidos isp. nov.), Conichnus conichnus, Fuscinapeda texana, Glaciichnium liebegastensis, Glaroseidosichnus ign. nov. gierlowskii isp. nov., Gruipeda (G. fuenzalidae and G. gryponyx), Midorikawapeda ign. nov. semipalmatus isp. nov., Planolites montanus, Presbyorniformipes feduccii, Protovirgularia dichotoma, Sagittichnus linki, Treptichnus (T. bifurcus, T. pedum, and T. vagans), and Tsalavoutichnus ign. nov. (Ts. ericksonii isp. nov. and Ts. leptomonopati isp. nov.). Four ichnocoenoses are represented by the ichnofossils—Cochlichnus, Conichnus, Presbyorniformipes, and Treptichnus—representing dwelling, feeding, grazing, locomotion, predation, pupation, and resting behaviors of organisms in environments at and around the sediment-water-air interface. A new Cochlichnus Ichnofacies is established to represent continental assemblages of traces produced in environmental conditions at and around the sediment-water-air interface. The Cochlichnus Ichnofacies can be identified in deposits from as old as the Carboniferous. The Cochlichnus Ichnofacies replaces the Shorebird Ichnofacies and usage of the Mermia Ichnofacies for ephemeral water bodies, and restricts the Mermia Ichnofacies to traces in deeper, perennial water bodies. A new ichnospecies of Aulichnites is proposed, A. tsouloufeidos. Three new ichnogenera with four ichnospecies are established: Glaroseidosichnus gierlowskii, Midorikawapeda semipalmatus, and Tsalavoutichnus (Ts. ericksonii, Ts. leptomonopati). This is the first detailed ichnotaxonomic study of the Soldier Summit and Spanish Fork Canyon localities of the Eocene Green River Formation.