A Critical Review of Eolian Ichnofacies

Abstract

Two ichnofacies have been named to encompass inland eolian depositional systems, the Octopodichnus and the Entradichnus ichnofacies, and are often combined into a single, Octopodichnus–Entradichnus ichnofacies. In contrast, coastal dune fields are characterized by a mixture of traces produced by marine and nonmarine organisms attributed to a single, Psilonichnus ichnofacies. However, inland eolian depositional systems lack marine organisms and encompass multiple lithofacies, the most extensive and broadly defined as being dunal and interdunal (includes many water laid deposits). The two lithofacies host generally different ichnoassemblages. Dunes are dominated by arthropod and tetrapod walking traces, whereas interdunes are dominated by shallow burrows, though there is some overlap in the ichnoassemblages of both lithofacies. A re-evaluation of the three ichnotaxa unique to the Entradichnus ichnofacies indicates they are invalid: Entradichnus = Taenidium, Pustulichnus = Skolithos, and Digitichnus is not based on a biogenic structure. The Entradichnus ichnofacies is characterized by abundant horizontal, backfilled traces of mobile deposit feeders and other ichnotaxa that indicate it is a synonym of the Scoyenia ichnofacies. I advocate subsuming the Laoporus, Brasilichnium, and Chelichnus ichnofacies of earlier workers under the Octopodichnus ichnofacies. Thus, the two principal ichnofacies of eolian depositional systems are the Octopodichnus and Scoyenia ichnofacies, though several other ichnofacies have been identified. No single ichnofacies characterizes eolian depositional systems.