Bioerosive structures in orbitolinid foraminifera: examples from the Lower Cretaceous of Central Iran

Abstract

Lower Cretaceous orbitolinid assemblages from Central Iran yield various bioerosional structures. The omnipresent traces of different boring taxa and groups (e.g., sponges, calcimicrobes, incertae sedis) represent a characteristic feature of the investigated thin-section material. The assemblage can be attributed to the Entobia ichnofacies dominated by borings assigned to the activity of sponges. The boring galleries are often concentrated in a plane parallel to the test surface, along the boundary of the marginal and the central zone of the orbitolinid tests. The borings are observed in foraminiferan-dasycladalean wackestones to poorly washed-out packstones, which can be referred to a subtidal palaeoenvironment.