Oligocene and Early Miocene coral faunas from Iran: palaeoecology and palaeobiogeography

Oligocene and Early Miocene coral assemblages from three sections of centra l Iran are investigated with respect to their palaeoecological and palaeobi ogeographic implications. These corals are compared with faunas from the Me diterranean Tethys and the Indopacific. Associated larger foraminifers are used for biostratigraphy and to support the palaeoecological interpretation . The studied sections are situated in the foreland basins of the Iranian P late which is structured into a fore-arc and a back-arc basin separated by a volcanic arc. The coral assemblages from Abadeh indicate a shallowing-upw ard trend. Infrequently distributed solitary corals at the base of the sect ion indicate a turbid environment. Above, a distinct horizon characterised by a Leptoseris-Stylophora assemblage associated with lepidocyclinids and p lanktonic foraminifers is interpreted as maximum flooding surface. Small pa tch reefs with a Porites-Faviidae assemblage are a common feature of Late O ligocene to Early Miocene coral occurrences and indicate water depths of le ss than 20 m. The diversity of the coral faunas shows marked differences. O ligocene corals from the Esfahan-Sirjan fore-arc basin comprise more than 4 5 species of 32 genera and occur in a wide range of environments. Early Mio cene corals from the Qom back-arc basin are less frequent, show a lower div ersity (13 genera with 15 species) and occur in single horizons or small pa tch reefs.