The late Miocene hominoid-bearing site in the Maragheh Formation, Northwest Iran

Abstract

After a long period of inactivity, recent excavations at the late Miocene Maragheh Formation unexpectedly resulted in the discovery of the first fossil hominoid and second Mesopithecus remains from this area. The discovery motivated a new international initiative to conduct research in these rich fossil sites. These studies focused on the fossil hominoid and its locality, aiming to reveal more about the context of this fossil discovery. Detailed stratigraphy, sedimentology and magnetostratigraphy studies were conducted. New samples from volcaniclastic key horizons (pumice beds) in Dareh Gorg, where the hominoid fossil site is located, were dated by radiometric methods. The radiometric age determinations provide a firm tie-point for the geochronology. The polarity pattern in the palaeomagnetically investigated section corroborates the K-Ar results. The preliminary magnetostratigraphic results suggest that the hominoid locality can be correlated to the normal polarity chron C4n.2n (8.108–7.695 Ma), C4n.1n (7.642–7.528 Ma) or C3Br.1n (7.285–7.251 Ma), placing it at intervals corresponding to the mammal units MN11 or possibly early MN12. The study of fossil hominoid indicates broad affinities with a number of contemporaneous taxa from the Balkan-Iranian palaeoprovince, as well as Siwaliks and southeast Asia. A preliminary analysis of the accompanying (in situ) fauna at the hominoid site indicates the highest similarity of this level to Turolian hominoid- and Mesopithecus-bearing localities in Turkey, Greece and Bulgaria. However, some environmental differences are observed among these localities, based on their faunal structure and taxon properties, as well as in the different masticatory adaptations of their hominoids.