Research Information System
European Geoscience Union, Viyana, Austria, 20 - 25 April 2007, vol.9, pp.4263, (Summary Text)
The Izmir-Ankara-Erzincan Suture Zone in the Eastern Pontides, Turkey, is restored as
a Santonian-Maastrichtian (85.8-65.5 Ma) south-facing ‘Western Pacific-Type’ active
margin. The structural vergence of individual units within the suture zone records
their emplacement history and is critical to understanding the tectonic assembly of
northeastern Anatolia.
Santonian-Campanian (85.5-70 Ma) southwards migration of arc volcanism was coupled
with the incorporation of Pontide metamorphic basement rocks into an extensionrelated
diabase dyke complex during subduction ‘rollback’. To the south, in the Taurides,
an abrupt conformable transition from neritic limestones to pelagic limestones
and coarse debrites of Campanian-Maastrichtian age (83.5-65.5 Ma) signifies the arrival
of the Tauride passive margin at the subduction trench. Trench-margin collision
triggered southward and northward emplacement of ophiolite, accretionary melange,
volcanic arc and related units over the Taurides and the Pontides respectively. Five
tectonostratigraphic units within the suture zone yield Late Cretaceous (Campanian-
Maastrichtian) biostratigraphic ages and preserve pervasive shear fabrics, folds and
faults exhibiting a relatively early top-to-the-north kinematic sense of movement.
Later north-vergent compressional deformation of Mid Eocene age is seen in adjacent
areas to the north. However, the Palaeocene-Eocene Sipikör Formation is the oldest
unit in the Eastern Pontides to lack evidence of north-vergent deformation in the area
studied. South-vergent thrusting subsequently imbricated all of the units of the suture
zone together with adjacent basement units and the overlying Sipikör Formation. The
deformed Upper Cretaceous-Lower Cenozoic units are overlain with angular unconformity
by Oligocene-Lower Miocene cover rocks of the Sivas Basin which were later
deformed by further folding and thrusting.
Structural and stratigraphic data support a model for backarc ophiolite emplacement
onto the Eurasian active continental margin during Campanian-Maastrichtian ‘soft
collision’. The backarc lithosphere was also underthrust southwards beneath the volcanic
arc. ‘Hard collision’ resulted in large-scale southwards re-imbrication, together
with northward backthrusting in some areas during Mid-Late Eocene time (48.6-37.4
Ma).