Haluk Temiz

A PALAEOMAGNETIC STUDY OF THE SIVAS BASIN, CENTRAL TURKEY : CRUSTAL DEFORMATION DURING LATERAL EXTRUSION OF THE ANATOLIAN BLOCK

Abstract The Sivas Basin is a complex collage of Eocene and younger rocks located within the wedge-shaped eastern margin of the Anatolian Block between the (dextral) North Anatolian Fault Zone and the (sinistral) Eastern Anatolian Fault Zone. It has been subject to ongoing deformation by movement of the Arabian Block into Eurasia and concomittant sideways expulsion of the Anatolian Block. Post-collisional deformation since mid-Miocene times has been dominated by NS to NWSE compression expressed by thrusting and strike-slip faulting. Cretaceous and Eocene rocks were magnetically overprinted to variable degrees during the collisional phase although these overprints have since been rotated mostly anticlockwise. Rocks emplaced during the neotectonic history are high-fidelity palaeomagnetic recorders of subsequent block movements. Regional anticlockwise rotation is recognised across the basin with differential rotation of fault and thrust-bounded blocks. An absence of perceptible differences between group mean rotations identified from Miocene, Pliocene and Quaternary units shows that most regional rotation has been concentrated within the latest phase of the neotectonic history during Quaternary times at an average rate of ∼ 10°/Ma. Commencement of this rotation postdates initiation of the North Anatolian Fault Zone implying that compression following collision was accomodated initially by crustal thickening during Late Miocene and Pliocene times. Subsequent anticlockwise rotations have resulted from sideways expulsion of blocks to the south of the Central Anatolian Thrust along major NESW sinistral faults to achieve the crustal shortening resulting from NS compression. These fault orientations and their sense of motion are explained by a Prandtl model involving deformation of a triangular plastic terrane (the Anatolian Block) between two rigid plates (Eurasia and Afro-Arabia). The variations in regional rotation identified by palaeomagnetism show that average contemporary anticlockwise rotation of Anatolia revealed by GPS data (∼ 1.2°/Ma) is achieved by variable, and locally large, block rotations between major thrusts and strike-slip faults.

Regional Significance of Neotectonic Counterclockwise Rotation in Central Turkey

Counterclockwise rotation is a characteristic feature of the results of most paleomagnetic studies of the Pontides and Anatolides of central Turkey, applicable to regions both north and south of the North Anatolian fault zone. In this paper, we report new data from Eocene volcanics and assess existing data from the calc-alkaline volcanic suites of this age. Although there are regional variations, probably resulting from rotations of individual fault blocks, an average counterclockwise rotation of ∼33° is identified across a region extending from 34° to 38° E Long. A mean Eocene paleolatitude of 27° N is compatible with ongoing northward movement and residual closure of a few degrees across the Pontide orogen during the latter part of its paleotectonic history. It seems probable that this rotated domain extends as far west as the Aegean graben system of western Turkey and as far south as the Taurides. Paleomagnetic evidence from younger volcanics suggests that the bulk of the rotation occurred during Quate...

Tectonics of the Sivas Basin: The Neogene Record of the Anatolian Accretion Along the Inner Tauric Suture

The Sivas Basin extends over a major crustal structure underlying the contact zone between the Tauride and Pontide belts. The Kirsehir block, a continental crustal element lying between the main belts, introduces a subordinate suture in front of the Pontides—the Inner Tauride suture. The junction of the two main sutures occurs between Hafikand Imranli. Four structural zones have been considered. The northern basement of the basin, which includes both the Kirsehir continental crust and thrust sheets of ophiolite and pelagic sediments, forms an imbricate stack with an Eocene cover. The Eocene cover shows two distinct sequences: marine neritic and continental basalts overlying the Kirsehir basement, and deltaic and basinal deposits lying to the southeast. Southward tectonic stacking of the entire pile has occurred repeatedly since Oligocene time. The Sivas Basin proper is separated from the Kirsehir basement by the Kizilirmak Basin. This new structural unit consists of nearly undeformed, middle Miocene sands...

Tectonostratigraphy and Thrust Tectonics of the Central and Eastern Parts of the Sivas Tertiary Basin, Turkey

The Sivas Tertiary Basin is one of the central Anatolian basins that formed over the collision zone between the Pontides and the Anatolide-Tauride belts. The basin, which is floored by southerly obducted Neotethyan ophiolite sheets onto the Taurides during the Late Cretaceous time interval, occupies a key position in the sedimentary record of the continental collision processes. The central and easternmost parts of the Sivas Basin around the Hafik (Sivas) and Kemah (Erzincan) regions have been studied with respect to tectonostratigraphy, tectonic style, and kinematics. The tectonic style of the Sivas Basin is characterized mainly by polyphase thrust systems developed along a regional NNW-SSE shortening direction. The general transport directions are oriented toward the south and southeast. However, N-vergent thrust development in the late Oligocene and late Pliocene-Quaternary epochs occurred in the central part of the Sivas Basin where thrust propagation is controlled mainly by a decollement surface at t...

Miocene transgression in the central and eastern parts of the Sivas Basin (Central Anatolia, Turkey) and the Cenozoic palaeogeographical evolution

We present here a reappraisal of the tectonic setting, stratigraphy and palaeogeography of the central part of the Sivas Basin from Palaeocene to late Miocene. The Sivas Basin is located in the collision zone between the Pontides (southern Eurasia) and Anatolia (a continental block rifted from Gondwana). The basin overlies ophiolites that were obducted onto Anatolia from Tethys to the north. The Central Anatolian Crystalline Complex (CACC) experienced similar ophiolite obduction during Campanian time, followed by exhumation and thrusting onto previously emplaced units during Maastrichtian time. To the east, crustal extension related to exhumation of the CACC created grabens during the early Tertiary, including the Sivas Basin. The Sivas Basin underwent several tectonic events during Paleogene–Neogene. The basin fill varies, with several sub-basins, each being characterised by a distinctive sequence, especially during Oligocene and Miocene. Evaporite deposition in the central part of the basin during early Oligocene was followed by mid-late Oligocene fluvio-lacustrine deposition. The weight of overlying fluvial sediments triggered salt tectonics and salt diapir formation. Lacustrine layers that are interbedded within the fluviatile sediments have locally yielded charophytes of late Oligocene age. Emergent areas including the pre-existing Sivas Basin and neighbouring areas were then flooded from the east by a shallow sea, giving rise to a range of open-marine sub-basins, coralgal reef barriers and subsiding, restricted-marine sub-basins. Utilising new data from foraminifera, molluscs, corals and nannoplankton, the age of the marine transgression is reassessed as Aquitanian. Specifically, age-diagnostic nannoplankton assemblages of classical type occur at the base of the transgressive sequence. However, classical stratigraphic markers have not been found within the planktic foraminiferal assemblages, even in the open-marine settings. In the restricted-marine sediments, there are rich planktic foraminiferal assemblages of classical type but these are of little use in stratigraphy. In contrast, the gastropod fauna indicate a Burdigalian age. Sediment reworking in the restricted-marine environments precludes stratigraphic determination. In such environments, micro- and nano-organisms experienced atypical developmental conditions. The small benthic foraminifera and associated ostracod assemblages are good indicators of salinity which varied considerably within the restricted-marine sub-basins. Some of the corals within the coralgal reefs barriers are also dated as Aquitanian. A combination of the salt tectonics and the late Miocene north-westward-verging thrusting created the present basin complexity.

Kinematics of Late Pliocene-Quaternary Normal Faulting in the Southeastern End of the Gediz Graben, Western Anatolia, Turkey

The kinematic analysis of fault-slip data obtained from lower Pliocene and Pleistocene deposits indicates two successive extensional events in the southeastern end of the Gediz graben. The late Pliocene N-S extensional phase was followed by a NNE-SSW extension in the Pleistocene. This change in extension direction from N-S to NNE-SSW is indicated by slip vectors on active fault planes and historic fault offsets. This younger extensional event is still active, as suggested by recent seismic activity and focal mechanisms of earthquakes in the region. The slip regime has important implications for the Neogene tectonic evolution of western Anatolia.

Tectonostratigraphy of the Tercan-Çayirli Basin: Implications for the Neogene-Quaternary Tectonic Deformation of the Northeast Anatolian Block, Turkey

The Tercan-Çayirli Basin is located in the Northeast Anatolian Block, and is bordered by the North Anatolian fault zone to the south and the Northeast Anatolian fault zone to the north. The basin developed on top of a southerly obducted, Upper Cretaceous ophiolitic mélange and low-grade metamorphic thrust sheets during Oligocene time. The lower sequences of the basin consist of coarse-grained continental clastics, reflecting foreland basin development. An Early Miocene transgression covered eastern Anatolia; deposition during this event corresponds to the upper sequences in the Tercan-Çayirli Basin. Late Miocene-Early Pliocene time is represented by basaltic-andesitic volcanism and continental sediments deposited in foreland basins. Coarse fluviatile clastics were deposited in strike-slip fault-controlled basins during the Quaternary. Tectonic deformation styles of the Northeast Anatolian Block and the Tercan-Çayirli Basin are shaped by Late Miocene-Early Pliocene thrust tectonics and Late Pliocene-Quaternary strike-slip tectonics, respectively. Kinematic analyses of fault slip data show NNW-SSE directions of movement. The tectonic deformation style of the Northeast Anatolian block reflects the combined effect of Late Miocene-Early Pliocene southward accretion and Late Pliocene-Quaternary eastward escape of the block toward the Caucasus.

The role of thrust ramp reactivation in pull-apart mechanism of the Erzincan basin, North Anatolian Fault Zone, Turkey

The new field data obtained from the southwestern margin of the Erzincan pull-apart basin located on the eastern segment of North Anatolian Fault Zone indicate that the opening of the basin is not only controlled by pull-apart mechanism but also by a lateral ramp structure associated with SSE-NNW Late Miocene thrusting along the Sivas Basin. The fault bordering the southwestern margin of the basin is the lateral part of the Karada thrust that is the roof thrust of the Sivas fold-thrust system, rather than a segment of the North Anatolian Fault Zone. The Erzincan basin was nucleated as a lateral ramp basin during the Pliocene on the lateral ramp-related folds and expanded by the pull-apart opening mechanism between two segments of the North Anatolian Fault Zone. The WSW-ENE pull-apart opening of the basin was recorded by the Pliocene lacustrine-fluvial sediments and Quaternary volcanics as listric normal faulting.

Geochemical characteristics of ophiolitic rocks from the southern margin of the Sivas basin and their implications for the Inner Tauride Ocean, Central-Eastern Turkey

Abstract Number of dismembered ophiolite bodies crop out between Sivas and Malatya on the top of the Eastern Tauride platform in the central-eastern Turkey. One of which at the southern margin of the Sivas basin in the Tecer Mountain area comprises melange and the lower part of an oceanic lithospheric section on top of the Tauride platform. The mantle tectonites are characterized by variably serpentinized harzburgites and dunites, and are intruded by numerous isolated dykes. The gabbroic cumulates consist of olivine gabbro, gabbro and gabbronorite. The major and trace element geochemistry of the mafic cumulate rocks suggests that the primary magma was compositionally similar to those observed in modern island-arc tholeiitic sequences. The isolated dykes are exclusively basaltic in composition and display geochemically two distinct subgroups: Group I is represented by high TiO2 (.87–1.47 wt.%) and other incompatible elements, whereas Group II is characterized by low TiO2 (.36–.66 wt.%) and other incompatible elements. The Group I isolated diabase dykes have flat to slightly LREE-depleted profiles (La/YbN = .32–.79), whereas the Group II isolated diabase dykes are more depleted in general and have a LREE-depleted character (La/YbN = .19–.49). This suggests that the isolated dykes were derived from an island arc tholeiitic magma (Nb/Y = .02–.05) with different degrees of partial melting (Group II > Group I) and relatively high oxygen fugacity in intra-oceanic subduction zone. The ophiolitic rocks in the study area may well be compared with the Divriği ophiolite to the southeast. All the evidence suggests that the isolated dykes in the Tecer Mountain area differ from the alkaline isolated dykes cutting the Divriği ophiolite. Since the late stage dykes (~76 Ma) in the Divriği area are alkaline, the tholeiitic isolated dykes in the present study should have been emplaced prior to the alkaline dykes during Late Cretaceous SSZ-spreading (~90 Ma) within the Inner Tauride Ocean.

Differentiation of Neotethyan ophiolitic mélange and an approach revealing its surficial chromite deposits using ASTER image and spectral measurements (Sivas, Turkey)

This work is aimed at differentiation of ophiolitic mélange rocks which were outcropped 60 km far from Sivas city center using image processing and spectral measurement methods. These rocks are known as oceanic crust remnants which were made up of different rocks. Turkey hosts several paleo-oceans and their realms in Alpine-Himalayan orogenic belt. The Neotethyan ophiolites in Turkey are characterized by supra subduction zone (SSZ-type) ophiolites. Ophiolitic rocks are generally coloured with greenish tones and human eye could not separate these tone differences. But satellite images such as ASTER can realize these separation utilizing spectral enhancement methods such as classification and decorrelation stretching. Chromite is a valuable mineral and is formed in only ophiolitic rocks. Dunites and harzburgites named as also ultramafic tectonits of ophiolitic serie mainly contain these deposits in study area. In this study, an approach was also realized to find target regions of chromite deposits with the aid of spectral methods. Spectral measurements were realized to determine boundaries between different mélange rocks using spectroradiometer. Reflectance curves collected from field and laboratory analysis were evaluated together and compared with ASTER image of the study area respectively. A detailed differentiation generally was accompanied with petrographic and geochemical analyses.