The Palorbitolinoides event in the Kazhdumi Formation of Southwest Iran and equivalent strata of the Arabian Plate: An expression of the K100 middle Albian transgression

Distinctive beds with abundant large, discoidal specimens of the orbitolinid foraminifera Palorbitolinoides hedini Cherchi and Schroeder are recorded from the Kazhdumi Formation from a section in south-west Iran where ammonite data and associated microfauna suggest a middle Albian age. This taxon, partly previously referred to Orbitolina or high-evolved mesorbitolinids (subconcava-aperta group), has been reported from other sections of the Kazhdumi Formation, the Nahr Umr Formation (Kazhdumi equivalent) of Oman, and the Tisje Formation of northern Somalia. Stratigraphic context and consideration of controlling factors on orbitolinid morphology places these accumulations of flat-discoidal orbitolinids within horizons forming the transgression to the regional Arabian MFS K100 maximum flooding sensu Sharland et al. (2001). These Palorbitolinoides limestones thus form useful marker beds assisting in regional correlation and age calibration. These records also confidently extend the range of P. hedini into younger Albian strata than previously recognised by most authors.

Automated summary

Abundant discoidal specimens of the orbitolinid foraminifera Palorbitolinoides hedini Cherchi and Schroeder are recorded from the Kazhdumi Formation in south-west Iran. These limestone beds are useful for regional correlation and age calibration.