Introduction: Tectonic Assembly of Anatolia: Implications for Hydrocarbon Prospectivity

Abstract

In this talk we will discuss some of the major recent advances and controversial aspects bearing on the tectonic assembly of Anatolia. The Precambrian rocks of the NW Pontides are widely seen as one or several circum-Gondwanan terranes that originated off NW Africa and, following eastward terrane dispersal, amalgamated to Eurasian by early Paleozoic and mid mid-Carboniferous time. The Palaeozoic units of the Taurides and Anatolides are commonly seen as having been located along the southern margin of a wide Palaeotethys, although some palaeontological data question the existence of any wide ocean during this time. The Variscan Pontide magmatic rocks are commonly interpreted as a subduction-related arc that was located along the southern margin of Eurasia. However, a location on the opposite side of Palaeotethys near Gondwana is also proposed. There is also a discussion about the direction of subduction; i.e. beneath Eurasia, beneath Gondwana, or both. In different interpretations, Palaeotethys was either entirely closed by latest Triassic or remained open and evolved into Neotethys by means of subduction and seafloor spreading. Triassic subduction is generally seen as northwards beneath Eurasia but some envisage southward subduction. Units like the Karakaya Complex are commonly seen as accretionary prisms but continental rift scenarios are still popular. Debate persists as the location, size and timing of closure of the Mesozoic Neotethyan oceans. Multiocean scenarios are gaining acceptance (e.g. Izmir-Ankara; Inner Tauride; S Neotethys) but are still questioned. Some see the Izmir-Ankara ocean as closed by latest Cretaceous but for others is remained partially open until Mid-Eocene. The S Neotethys (assuming its existence) closed in latest Cretaceous, Eocene, or Early Miocene time in different views. Probably all of the large emplaced ophiolites (mostly Late Cretaceous) formed above subduction zones and not at spreading ridges, significantly changing traditional views. The above and other tectonic scenarios directly or indirectly influence hydrocarbon prospectivity (e.g. presence or absence of buried continental platforms/slopes; regional heat flow variations, burial/exhumation and terrane dispersal. In the talk we will indicate the alternatives and some of our preferred solutions to the tectonic problems and we will emphasise where more work is needed to solve outstanding issues.