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

Abstract

Oligocene and Early Miocene coral assemblages from three sections of central Iran are investigated with respect to their palaeoecological and palaeobiogeographic implications. These corals are compared with faunas from the Mediterranean 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 Plate 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-upward trend. Infrequently distributed solitary corals at the base of the section indicate a turbid environment. Above, a distinct horizon characterised by a Leptoseris-Stylophora assemblage associated with lepidocyclinids and planktonic foraminifers is interpreted as maximum flooding surface. Small patch reefs with a Porites-Faviidae assemblage are a common feature of Late Oligocene to Early Miocene coral occurrences and indicate water depths of less than 20 m. The diversity of the coral faunas shows marked differences. Oligocene corals from the Esfahan-Sirjan fore-arc basin comprise more than 45 species of 32 genera and occur in a wide range of environments. Early Miocene corals from the Qom back-arc basin are less frequent, show a lower diversity (13 genera with 15 species) and occur in single horizons or small patch reefs.

The Oligo-/Miocene Qom Formation (Iran): evidence for an early Burdigalian restriction of the Tethyan Seaway and closure of its Iranian gateways

“…Within this project, basic biostratigraphic data from the Qom Fm. outside the Qom Basin were already published by Schuster and Wielandt (1999). However, up to now no satisfactory stratigraphic framework exists that allows a correlation of the Qom Fm.…”

“…from the Qom and Esfahan-Sirjan basins (Harzhauser et al 2002;Harzhauser 2004;Schuster and Wielandt 1999;Mandic 2000). Within this project, basic biostratigraphic data from the Qom Fm.…”

Timing of uplift in the Zagros belt/Iranian plateau and accommodation of late Cenozoic Arabia–Eurasia convergence

“…Based on the youngest marine sediments dated in Iran, it is beyond doubt that both the Zagros and the Iranian plateau were still below sea-level until Early Miocene time (Schuster & Wielandt, 1999;Harzhauser et al 2007), and one can also be confident that until ∼ 15 Ma the northern Zagros Folded Belt was close to sea-level (Khadivi et al 2010).…”

Facies analysis and sequence stratigraphy of the Asmari Formation in the northern area of Dezful Embayment, south-west Iran

“…The porcelaneous foraminifera associated with Bioclastic packstone with corallineaceans and corals floatstonerudstone facies is typical of shallow and illuminated habitats where sea grass flats intersect adjacent non-vegetated areas (Brandano et al, 2008). Moreover, scattered branching corals are typical for areas with reduced water energy located in the lowest part of the euphotic zone (Schuster and Wielandt, 1999). However, the common coral debris may have derived from adjacent patch reefs or could also have been produced in situ from isolated colonies that are known to grow in sea grass environments (Brasier, 1975).…”