Scratch circles and circular purported ammoglyphs: Novel observations from the Cape south coast of South Africa

Abstract

Scratch circles, previously defined as ‘bedding plane parallel sedimentary structures formed by the passive rotation of a tethered organism into the surrounding sediment’, have hitherto been identified in the geological record from the Ediacaran to the Paleocene, as well as in modern settings. They have not met the definition of trace fossils, being passively registered by a part of a plant. Several variations of scratch circle morphology have been identified in or on Pliocene and Pleistocene deposits on the Cape south coast of South Africa, allowing for an expansion of the scratch circle temporal range. Furthermore, these novel forms require a redefinition of the term ‘scratch circle’. Anthropogenic origins need to be considered for occurrences in the Pleistocene; guidelines to assist in distinguishing such causes from typical scratch circles are presented. Scratch circles may conceivably have inspired the creation of circular patterns (palaeo-art) in sand by Middle Stone Age hominins. Evaluation of scratch circles in snow allows for subtle features to be determined. A re-evaluation of what the term ‘trace fossil’ constitutes could be considered, in order to include the term palaeo-ichnobotany.