To solve a long-lasting controversy on the timing and mechanism of generation of the western Anatolian graben system, new data have been collected from a mapping project in western Anatolia, which reveal that initially north-south trending graben basins were formed under an east-west extensional regime during Early Miocene times. The extensional openings associated with approximately north-south trending oblique slip faults provided access for calc-alkaline, hybrid magmas to reach the surface. A northsouth extensional regime began during Late Miocene time. During this period a major breakaway fault was formed. Part of the lower plate was uplifted and cropped out later in the Bozda~ Horst, and above the upper plate approximately north-south trending crossgrabens were developed. Along these fault systems, alkaline basalt lavas were extruded. The north-south extension was interrupted at the end of Late Miocene or Early Pliocene times, as evidenced by a regional horizontal erosional surface which developed across Neogene rocks, including Upper Miocene-Lower Pliocene strata. This erosion nearly obliterated the previously formed topographic irregularities, including the Bozda~ elevation. Later, the erosional surface was disrupted and the structures which controlled development of the Lower-Upper Miocene rocks were cut by approximately east-west trending normal faults formed by rejuvenated north-south extension. This has led to development of the present-day east-west trending grabens during Plio-Quaternary time.cene ($eng6r et al. 1985; GOrt~r et al. 1995).

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Recently acquired data lead to a revision of the structure around the apex of the Isparta Angle (area around Isparta). In the autochthonous/parautochthonous carbonate platform several blocks are identified as having followed distinctive palaeogeographical evolutions during Mesozoic times. These blocks are: the Kır Dağları, the Barla Dağ, the Söbü Dağ and the Bey Dağları. However, the latter two blocks cannot be considered as identical as previously believed. A major thrust fault may separate these blocks, which may be substantially allochthonous with respect to the relatively autochthonous Bey Dağları. Within the allochthon, in the Isparta Çay area, studied here, Mesozoic deep‐marine sequences are thrust duplicated many times. The tectonic history of the area is polyphased, the main events being in the Late Cretaceous (initiation of shortening), pre‐Miocene (Antalya Nappe emplacement), and Late Miocene/Pliocene (Aksu thrusting). The Aksu phase reactivates older thrusts and has given rise to the most prominent relief of the area (the Davras Dağ, 2600 m). Palaeogeographic reconstructions are proposed to take account of all the above data. Copyright © 2003 John Wiley & Sons, Ltd.

The Tokat Massif consists of a pre-Jurassic metamorphic complex that crops out widely between Amasya and Refladiye in the western part of eastern Pontides, and which can be correlated with the Karakaya Complex of the western Pontides. This complex is named the Tokat Group, and is divided into two main units, namely, the Turhal Metamorphics and Devecida¤ Mélange. The Turhal Metamorphics form a volcano-sedimentary sequence in the northern part of the Tokat Massif. The lower level of the formation is made up of gneiss, amphibolite and mica schists, whereas the upper part is represented by an alternation of mica schist, phyllite, metaclastic rocks, metabasite and marble, which probably reflects an arc association. The Devecida¤ Mélange is characterised by a metavolcano-sedimentary olistostrome, which forms the southern part of the massif. This unit is quite heterogeneous and reflects, in places, a subduction mélange and/or a fore-arc sequence. The Devecida¤ Mélange may have formed in a setting between a subduction zone and a fore-arc. The units of the Tokat Massif can be traced along the eastern Pontides and also along the North Anatolian Ophiolitic Belt. These units have been accreted to the mélange prism as tectonic slices along the North Anatolian Ophiolite Belt before the Campanian. Some of Late Cretaceous ophiolitic mélange slices also crop out in the Tokat Group as E-W-trending tectonic slices. The ophiolites and ophiolitic mélange are believed to have been emplaced both to the north and to the south during the Late Cretaceous. The north-vergent thrusts have been later realigned into south-dipping thrusts during a neotectonic phase.

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