ÇAĞRILI KONUŞMALAR / KEYNOTES Invited Speeches ... - TPJD

Introduction: Tectonic Assembly of Anatolia: Implications for Hydrocarbon
Prospectivity
Alastair H. F. Robertson 1 , Aral İ. Okay 2 , Osman Parlak 2 , Timur Ustaömer 4
1 University of Edınburgh, School of Geosciences, UK
2 İstanbul Technical University, İstanbul, Turkey
3 Çukurova University, Department of Geological Engineering, Adana
4 İstanbul University, Department of Geology, İstanbul
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.
Keywords : Tectonics, Anatolia, models, alternatives
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