Distinction between fill channels and abrasion furrows on ammonoid internal moulds

Abstract

Ammonoid sedimentary internal moulds can display grooves on the external or ventral region that have been formed by diverse taphonomic processes. In particular, draft-filling spiral channels and abrasion annular furrows are taphonomic structures useful as palaeoenvironmental indicators of turbulent waters and conditions of low rate of sedimentation, although they can show some common morphological properties that may lead to erroneous identifications. However, the morphological features, formation processes and palaeogeographic conditions in which the structures of these two types have been developed are very different. In consequence, it is important to keep in mind the distinctive characters of these taphonomic structures before using their occurrence in the palaeoenvironmental or palaeogeographic interpretations.