Palaeomagnetic study of the Karaman and Karapinar volcanic complexes, central Turkey: neotectonic rotation in the south-central sector of the Anatolian Block

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Tectonophysics 299 (1998) 191–211

Palaeomagnetic study of the Karaman and Karapinar volcanic complexes, central Turkey: neotectonic rotation in the south-central sector of the Anatolian Block H. Gu¨rsoy a , J.D.A. Piper b,Ł , O. Tatar a , L. Mesci a b

a Department of Geology, Cumhuriyet University, 58140 Sivas, Turkey Geomagnetism Laboratory, Department of Earth Sciences, University of Liverpool, Liverpool L69 7ZE, UK

Received 4 October 1997; accepted 9 May 1998

Abstract In the Anatolian sector of the Afro–Eurasian collision zone a palaeotectonic collisional phase (Paleocene to Miocene) responsible for emplacement of the Pontide and Tauride orogens has been replaced by a neotectonic phase of continental deformation (Late Miocene=Early Pliocene to Recent). The latter phase appears to have been accommodated mainly by crustal thickening during Late Miocene and Pliocene times, but was succeeded by complex differential rotations of fault blocks during crustal extrusion in Late Pliocene and Quaternary times. In this study we have investigated palaeomagnetism of Miocene–Recent volcanic rocks comprising the western extension of the Central Anatolian Volcanic Province located in the south-central part of the Anatolian Block with the aim of resolving deformations near to the border with the Tauride orogen. Rock magnetic investigations identify low-Ti magnetite assemblages of primary cooling-related origin. These have predominant multidomain structures but significant fractions of single domains are always present; low-temperature alteration is largely absent. The Karaman Volcanic Complex (Late Pliocene) shows a net rotation of 5:7 š 6:9º not significantly different from the regional field axis during Recent times. The Karapinar Volcanic Field (Brunhes epoch) identifies a larger net rotation of 23:1 š 12:0º in a restricted sample. The adjoining Karacada˘g Volcanic Complex (Late Miocene–Pliocene) and Middle Miocene lavas beneath the Hasanda˘g Complex define net rotations of 8:1 š 5:9º and 16:4 š 8:9º respectively. Analysis of palaeomagnetic results from Late Cretaceous–Recent rock units emplaced in Anatolia during the palaeotectonic and neotectonic regimes shows that rates of rotation have accelerated in post-Pliocene times as crustal thickening has given way to tectonic escape. A near-uniform anticlockwise rotation of 25–35º has characterised much of this block during the most recent phase of deformation and appears to have occurred in common with the Eurasian Plate to the north of the North Anatolian Fault Zone. Whilst this rotation appears to extend south eastwards across the Ecemi¸s Fault Zone towards the East Anatolian Fault, the present study shows that smaller differential anticlockwise rotations have characterised the south-central region of the block where it has interacted at its southwestern margin with oroclinal bending focussed on the Isparta angle.  1998 Elsevier Science B.V. All rights reserved. Keywords: palaeomagnetism; Turkey; Anatolian Block; volcanics; Cenozoic; tectonic rotation

Ł Corresponding

author. Fax: C44 151 794 3464; E-mail: [email protected]

0040-1951/98/$ – see front matter  1998 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 0 - 1 9 5 1 ( 9 8 ) 0 0 2 0 5 - 4

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1. Introduction The neotectonic framework of Turkey was initiated in Late Miocene times as the Arabian sector of the African Plate impinged into the East Anatolian sector of the Anatolian Block along the Bitlis Suture Zone (BSZ, Fig. 1). The palaeotectonic history of orogenic deformation has since been succeeded by an ongoing neotectonic phase of deformation motivated by the northward motion of Arabia at a rate of ¾2.5 cm=year (Oral et al., 1995) relative to the African Plate (¾1.0 cm=year). This differential motion is taken up mainly along the Dead Sea Fault Zone (DSFZ in Fig. 1A) and is responsible for a westward expulsion of the crust in central Turkey (Mantovani et al., 1993). The resulting ‘escape tectonics’ is accommodated primarily by dextral motion along the North Anatolian Fault Zone (NAFZ), a major intracontinental transform defining the tec-

tonic boundary between the Eurasian Plate to the north and the Anatolian Block to the south. Both geological (Sengo ¸ ¨ r et al., 1985; Andrieux et al., 1995) and GPS (Oral et al., 1995) data indicate that the rate of motion on the NAFZ decreases to the west within the range 1.6–2.7 cm=year (Kiratzi, 1993). As a consequence, internal deformation of the Anatolian Block is complex: in part it is probably accommodated by block rotations along side splays such as the Kirikkale–Erbaa and Almus Fault Zones (KEF and AF in Fig. 1A). In addition, continuing impingement of Arabia into Anatolia and Eurasia has produced complex deformation of the terrane within the wedge-shaped eastern sector sited between the NAFZ and the EAFZ (Fig. 1A); this is accompanied by sinistral strike-slip motion on the latter fault at a lower level (¾0.9 cm=year) than along the NAFZ. Onset of the neotectonic regime in Anatolia is dated primarily by reference to the sedimentary

Fig. 1. (A) The tectonic divisions and distribution of major lineaments in Turkey and adjoining regions. The large open arrows show relative motions of the plates and the smaller half arrows are directions of movement on major strike-slip faults. Abbreviations: NAFZ D North Anatolian Fault Zone; EAFZ D East Anatolian Fault Zone; SLF D Lake Salt Fault Zone; KEF D Kirikkale–Erbaa Fault Zone; AF D Almus Fault Zone; EFZ D Ecemi¸s Fault Zone; SZ D East Mediterranean subduction zone; CATB D Central Anatolian Thrust Belt; DSFZ D Dead Sea Fault Zone. The political boundary of Turkey is also shown together with boundaries of areas illustrated in subsequent figures. (B) The inset figure (revised from S¸ engo¨r, 1984 and Guezou et al., 1996) shows the major terrane divisions of Turkey juxtaposed by the collisional events preceding the Neotectonic Phase of deformation.

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basins produced by internal deformation of the crust since collision. Basins along the NAFZ, formerly interpreted as the result of pure strike-slip (S¸ engo¨r, 1979), are now recognised as a result of detailed recent mapping (Koc¸yi˘git, 1996) to be ‘superimposed’ and the consequence of an Early–Middle Miocene piggy-back cycle followed by a Plio–Quaternary strike-slip regime. This observation implies that the neotectonic history sensu stricto is confined to Pliocene and Quaternary times. It has been accompanied by extensive calc-alkaline volcanism which is concentrated into four main regions geographically located in east, central and west Anatolia, plus the Galatean Volcanic Province (GVP in Fig. 2) bordering the NAFZ along the northern margin of the block. The present paper reports a palaeomagnetic study of the Central Anatolian Volcanic Province (CAVP) and evaluates tectonic implications of the data in the context of wider palaeomagnetic investigations of neotectonic rock suites from the Anatolian Block (Fig. 3).

2. Geological framework The Anatolide and Tauride belts formed as a consequence of sub-accretionary ophiolite obduction and microplates collision along several sutures (Fig. 1A). Subsequent suturing along this zone has produced three tectonic provinces classified by Sengo ¸ ¨ r (1980) as the Aegean Graben System, the Central Anatolian ‘Ova’ (D plain) Province and the East Anatolian Contractional Province (Fig. 1B). The CAVP is located within the Ova Province and comprises some 20 eruptive centres extending for 300 km along a NE–SW trend (CAVP in Fig. 2). Volcanic and volcano-clastic successions have been erupted onto Tertiary sedimentary basins (Tuzgo¨lu¨, Ulukı¸sla and Sivas) or older metamorphic complexes (Kir¸sehir, Ni˘gde). The eruptive centres appear to be located at the intersections of major fault zones such as the dextral Salt Lake and the sinistral Ecemi¸s faults (Pasquare et al., 1988, Toprak and Go¨ncu¨o˘glu, 1993). Previous studies of the CAVP have focussed on petrographic and geochemical characteristics, and age dating (Pasquare, 1968; Innocenti et al., 1975; Besang et al., 1977; Batum, 1978a,b; Ercan, 1986;

193

Temel, 1992; Ercan et al., 1992; Olanca et al., 1992). The dominant calc-alkaline chemistry of the volcanism has been related to subduction along the arcuate Eastern Mediterranean Subduction Zone (SZ in Fig. 1A) beneath the Cyprian Arc which causes extension in the Anatolian region above the subducted plate (Innocenti et al., 1975; Batum, 1978a; Tokel et al., 1988; Ercan et al., 1992). Differential plate motions meet in the ‘Isparta angle’ (Fig. 1A) where average slip rates on the eastern flank are 15 mm=year compared with 30 mm=year on the western flank (Barka et al., 1997). Lava flows emplaced during the neotectonic phase have mostly proved to be high-quality recorders of the magnetic field at the time of cooling (Tatar et al., 1995; Piper et al., 1996; Gu¨rsoy et al., 1997) and, because they have never been deeply buried, are little contaminated by later overprinting. Since their tectonic orientations can usually be constrained by flow structures and interbedded strata, they are also effective recorders of subsequent tectonic rotation and form the focus of this study. The main limitation of the volcanic rocks for quantifying rotation is that rapid cooling will usually have recorded a near-instantaneous record of the palaeosecular variation and will not yield a mean geomagnetic field direction. It is therefore important to draw tectonic conclusions from groups of sites yielding a mean approximation to a time-averaged (palaeomagnetic) direction, rather than stressing the significance of results from individual units. The other qualification which can limit the value of some individual results and increase the scatter of inclinations is uncertainty in the tilt adjustments (Table 1): it is probable that some lavas in these study areas have flowed down primary slopes and, when orientation information is based on structures within the flow, the precise amount of the tilt adjustment remains uncertain. Lavas from the volcanic district north of Karaman comprise a partially eroded complex (the Karada˘g) with a core of pink porphyritic basaltic andesites and tuffs. These are overlain by basaltic flows linked to younger parasitic cones and fan deposits eroded from the central part of the complex (Fig. 4). The basalts occur around the periphery of the complex; their primary flow and cone morphologies imply that they are essentially intact and probably all of Quaternary to Recent age. The older basaltic-andesite complex

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Fig. 2. Outline geological map of Central Anatolia including the Central Anatolian Volcanic Province (CAVP). The numbered symbols: 1 D Quaternary basin fill; 2 D Quaternary volcanics; 3 D Pliocene volcanics and volcanoclastics; 4 D Mio–Pliocene volcanics and volcanoclastics; 5 D Tertiary Basins; 6 D ophiolitic melange; 7 D Tokat Massif; 8 D Kir¸sehir Massif; 9 D Central Anatolian Volcanic Province (CAVP) boundary.

is dated Late Pliocene to Quaternary (3.20 to 1:13 š 0:09 Ma) by Besang et al. (1977). The 18 sampling sites in this region are summarised in Table 1 and their distribution is shown in Fig. 4. A field of young spatter cones and blocky lavas is sampled by sites 19 to 24 with details summarised

in Table 1 and a distribution shown in Fig. 5A. Lavas are dated between 1:15 š 0:076 Ma and 64; 000 š 15; 000 years in age (Ercan et al., 1990). Immediately to the northeast lies the Karacada˘g, a degraded volcanic complex which is undated, but inferred to be Late Miocene to Pliocene in age (Er-

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Fig. 3. The three volcanic complexes investigated in the present study. The distribution of the CAVP volcanics is based on Ercan (1986) and the 1 : 2,000,000 geological map of Turkey (Bingo¨l, 1989).

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Table 1 Summary of palaeomagnetic sampling sites in the Karaman, Karapınar, Karacada˘g and Hasanda˘g volcanic districts, central Turkey Site No.

Age

N

J0

(1) Lavas, Karaman Complex 1 Porphyritic andesite 2 Andesite 3 Porphyritic andesite 4 Porphyritic basalt 5 Porphyritic andesite 6 Porphyritic andesite 7 Porphyritic andesite 8 Porphyritic andesite 9 Porphyritic andesite 10 Porphyritic basalt 11 Porphyritic andesite 12 Porphyritic basalt 13 Porphyritic basalt 14 Porphyritic andesite 15 Basalt 16 Basalt 17 Basalt 18 Porphyritic basalt

L. Pliocene L. Pliocene L. Pliocene L. Pliocene L. Pliocene L. Pliocene L. Pliocene L. Pliocene L. Pliocene L. Pliocene L. Pliocene L. Pliocene L. Pliocene L. Pliocene L. Pliocene L. Pliocene L. Pliocene L. Pliocene

7 7 7 7 7 7 7 7 7 7 7 7 7 5 7 7 7 7

26.22–14.38 10.50–4.39 5.72–2.51 0.48–9.08 47.58–16.01 36.55–9.62 26.82–23.70 38.78–26.63 5.21–2.06 12.02–8.70 40.94–17.19 15.38–2.57 5.53–3.68 10.99–2.617 4.30–2.17 4.51–0.96 7.25–4.29 2.91–0.63

(2) Lavas, Karapınar volcanic region 19 Basalt 20 Basalt 21 Basalt 22 Basalt 23 Basalt 24 Basalt

L. Quaternary L. Quaternary L. Quaternary L. Quaternary L. Quaternary L, Quaternary

7 7 7 7 6 7

13.58–6.86 308.90–81.60 27.59–19.05 37.93–12.37 28.70–19.14 59.39–29.08

(3) Lavas, Karacada˘g volcanic region 25 Basalt 26 Andesite 27 Basalt 28 Basalt 29 Basalt 30 Basalt 31 Basalt 32 Basalt 33 Basalt 34 Basalt 35 Basalt 36 Basalt 37 Basalt 38 Basalt 39 Basalt 40 Basalt

L. Miocene–Pliocene L. Miocene–Pliocene L. Miocene–Pliocene L. Miocene–Pliocene L. Miocene–Pliocene L. Miocene–Pliocene L. Miocene–Pliocene L. Miocene–Pliocene L. Miocene–Pliocene L. Miocene–Pliocene L. Miocene–Pliocene L. Quaternary L. Miocene–Pliocene L. Miocene–Pliocene L. Miocene–Pliocene L. Miocene–Pliocene

7 7 7 7 7 7 7 7 7 7 6 7 7 7 7 7

8.94–0.69 40.08–26.99 77.64–1.58 18.01–6.95 10.80–6.53 10.97–2.87 14.33–3.82 66.51–6.51 28.42–9.80 16.69–6.45 2.83–1.67 64.07–24.45 123.10–9.00 6.48–4.15 25.32–4.88 169.0–13.63

(4) Lavas, Hasanda˘g region 41 Basalt 42 Basalt 43 Basalt 44 Basalt 45 Basalt 46 Basalt 47 Basalt

M. Miocene M. Miocene M. Miocene M. Miocene M. Miocene M. Miocene M. Quaternary

7 7 7 7 7 7 6

28.31–1.90 23.56–5.27 2.44–0.96 5.98–1.50 261.49–10.31 139.57–7.06 129.33–94.21

Age subdivisions: M is Middle and L is Late. N is the number of separately oriented cores. Intensities of the natural remanent magnetisation (NRM), J0 , are in ð10 4 A m2 =kg.

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197

Fig. 4. Geological and sampling site map of the Karaman Volcanic Complex.

can, 1986). This has been sampled at fifteen sites numbered 25–35 and 36–40 (Fig. 5A and Table 1); a small younger volcanic field presumed to be an extension of the activity at Karapinar is sampled at site 36. Sampling extends up to the Salt Lake (dextral) Fault system (see Fig. 1A) in the Ta¸spınar region (Fig. 5B) where a field of Miocene volcanics dated 13:7 š 0:3 to 12:4 š 0:6 Ma by Besang et al. (1977) is partially covered by younger lavas derived from

the Hasanda˘g Volcano. These volcanics are sampled at sites 41 to 46. A single young basalt flow (site 47) is located at Kitreli 25 km east of Ta¸spınar on the opposite side of the Hasanda˘g Volcano.

3. Field and laboratory methods Samples were cored in the field using a motorised drill and oriented by both sun and magnetic com-

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Fig. 5. Geological and sampling site map of (A) the Karapinar and (B) the Hasanda˘g volcanic regions. The geology of the Hasanda˘g region is simplified after Toprak and Go¨ncu¨o˘glu (1993).

passes. Typically seven cores were extracted from each unit and distributed across several metres of outcrop. Core collection was accompanied by local investigation to evaluate the setting of each sample

location. Many lava units drilled for this study were recognised to be perceptibly horizontal. Some examples from the Karaman Complex have observable dips of up to 30º, but since directions of dip are

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in each case approximately away from the volcanic centre we conclude that they record primary slopes down which the lavas flowed. This interpretation is supported by the observation that tilt adjustment in every case moves the palaeomagnetic direction away from the predicted palaeofield direction (Section 6). Hence we conclude that these young volcanic domains may have rotated regionally, but have not undergone significant local deformation since formation; the palaeomagnetic directions are accordingly interpreted in situ. In the laboratory the field cores were sliced into 2.4-cm-long cylinders for routine palaeomagnetic measurement employing ‘Minispin’ magnetometers. With the exception of a few units which exhibit instability to cleaning treatment, in common with most other young rocks emplaced during the neotectonic regime, the samples have magnetic structures dominated by discretely defined characteristic remanent magnetisations (ChRMs); these are typically contaminated by only minor amounts of viscous remanent magnetisation (VRM). No significant difference was observed between ChRMs defined by alternating field (a.f.) and thermal demagnetisation and roughly equal numbers of cores were subjected to each cleaning technique. All samples were progressively treated in steps of 50 or 100ºC and 5 or 10 millitesla (mT) which proceeded until components were subtracted or directional behaviour ceased to be stable. Orthogonal projections were then produced and components constituting the NRM isolated. Their equivalent directions were calculated by principal component analysis and common site populations grouped to yield the site means listed in Table 3. Lowest blocking temperature=coercivity components are laboratory or drilling-related acquisitions, or are in the present field direction; these are interpreted as VRMs. Only higher and=or distributed spectra are regarded as ChRMs and included in this compilation.

4. Rock magnetism The most important ferromagnetic mineral in the basaltic and andesitic lavas of this study is likely to be titanomagnetite with a composition of about TM50, i.e. near the middle of the magnetite–

199

ulvo¨spinel solid solution series. During deuteric alteration this typically undergoes sub-solidus exsolution to produce ilmenite and Ti-poor magnetite; this alteration may proceed to the production of pseudobrookite and hematite through seven classes (Haggerty, 1976) ranging from unoxidised to completely oxidised. Strong-field thermomagnetic analysis can indicate the nature of the titanomagnetite from the Curie temperature as well as providing information about the degree of alteration that occurs on heating. In this study saturation magnetisation was measured from room temperature to 700ºC using a computer-controlled horizontal Curie balance. The Curie temperature was estimated from the thermomagnetic curve using the method of Gromme´ et al. (1969); the change in saturation magnetisation at 100ºC following heating and cooling (the ratio RM in Table 2) is a measure of alteration during heating in air. The form of the thermomagnetic curves is notably uniform through the collection: Js illustrates a smooth fall to define the Curie point of a Tipoor titanomagnetite, usually just below the Curie point of pure magnetite (580ºC, see Fig. 6). In a few cases, most notably in the Miocene lavas beneath the Hasanda˘g Volcano, two distinct magnetite phases are discernible, one is a Ti-bearing phase with a Curie point ¾540º and the other a pure magnetite. The only possible signature of low-temperature maghemitisation resulting from the formation of metastable non-stoichiometric titanomaghemite (cation-deficient titanomagnetite) is a weak inflection in a few examples defining Curie points between 180 and 250ºC. Thus, reflecting an absence of appreciable burial, none of the sampled units appear to have experienced significant alteration. The rare identification of hematite (although sometimes evident from hysteresis behaviour) is a consequence of its much lower saturation remanence and incomplete saturation achievable by the fields employed (0.2– 0.5 tesla). The reduction of Js with heating to yield RM values of ¾0.7–0.9, which is the most common feature of this collection (Fig. 6 and Table 2) is probably caused by further oxidation promoted by the heating. Uncommon RM values >1 are usually observed when a low temperature phase is discernible, although alteration of this by heating does not always produce increase in Js .

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Table 2 Results of thermomagnetic and hysteresis investigation of lavas from this study MS

MRS

1 2 3 4 5 6 7 8 9 10 11 12 14 15 16 18 19 20 21 22 23 24 25 26 28 29 30 31 32 33 34 35 36 37 39 40 41 42 43 44 45 46 47

1.09 0.55 – 1.19 – 0.87 – – 0.36 0.93 0.81 0.49 – 0.37 0.46 0.61 0.41 – 1.12 0.74 0.58 – 1.59 – 1.16 2.38 1.04 1.92 2.10 1.90 1.23 – 1.20 2.30 0.93 2.96 1.05 1.19 1.55 1.76 0.88 1.64 0.74

16.09 13.86 0.148 7.02 14.17 0.128 0.01 140.85 – 2.97 2.11 0.025 2.65 16.06 – 10.92 11.51 0.126 2.14 23.92 * 4.14 21.39 – 4.57 12.73 0.126 9.62 7.95 0.103 18.89 12.77 0.232 3.81 9.64 0.077 3.20 22.34 * 2.80 8.94 0.077 2.45 6.13 0.054 2.18 4.28 0.036 6.00 5.44 0.146 9.09 12.20 – 11.38 7.95 0.101 23.51 29.00 0.320 15.15 20.98 0.262 9.92 27.91 * 11.17 5.42 0.070 3.08 28.30 * 12.40 10.84 0.107 15.35 7.40 0.064 11.95 14.52 0.114 13.90 9.30 0.072 17.59 9.42 0.084 16.97 11.68 0.089 14.16 12.14 0.115 – – – 21.81 17.43 0.182 18.79 6.75 0.082 6.67 3.92 0.072 17.84 6.65 0.060 14.33 15.69 0.137 16.66 14.22 0.140 14.80 8.58 0.096 25.76 14.56 0.147 11.04 7.69 0.125 22.95 14.47 0.140 21.71 24.79 0.292

250

220 220 590

180

240

435 540 535 520 525 480

580 570 650 530 570 575 570 575 640

0.45 0.42 0.93 1.00 0.90 0.86 0.89 0.90 0.72

560 570 540

0.97 0.91 0.90

540 540 550 550 520 610 590 580 590 590 585 570 585 565 585 585 580 575 560 550 560 585 590 585 585 580 585 580 545

0.86 0.92 0.83 0.85 0.94 0.91 0.74 0.89 0.71 1.05 0.79 0.83 0.78 0.85 0.84 0.88 0.76 0.77 0.82 1.10 0.97 0.90 0.85 0.89 1.10 0.89 1.12 0.72 0.94

HC

MRS =MS

No. Tc1 Tc2 RM

X MD 0.73 0.78 – 0.99 – 0.78 – – 0.78 – 0.56 0.88 – 0.88 0.93 0.97 0.74 – 0.83 0.38 0.50 – 0.90 – 0.82 0.91 0.80 0.89 0.87 0.86 0.80 – 0.66 0.87 0.89 0.92 0.76 0.75 0.84 0.74 0.78 0.75 0.43

Tc1 and Tc2 are Curie temperatures; RM is the ratio at 100ºC of the magnetisation during cooling to the magnetisation during heating; units of MS and MRS are A m2 kg 1 and ð10 2 A m2 kg 1 , resp., and HC is ð103 A m 1 ; * denotes a constriction in the hysteresis curve due to a mixture of hard and soft magnetic phases; the values of MS and MRS =MS are not given when the sample failed to saturate in a 1-tesla field.

Hysteresis data yield information about mineralogy and domain state: titanomagnetites and titanomaghemites saturate in fields of 300 mT or less, whereas hematites require much larger fields to achieve saturation. Using a Molspin vibrating sample magnetometer (VSM) the following hysteresis parameters were determined: saturation magnetisation, Ms , saturation remanence, MRS , and coercive force, HC. With a maximum field of 1 tesla, it was not possible to saturate hematite and MS could not be determined when this mineral was present in significant amounts (Table 2). The parameters MS and MRS are dependent on the concentration and type of the magnetic minerals present; MS is independent of grain size but MRS is smaller for multidomain (MD) than for single domain (SD) grain properties. Hence the ratio of MRS =MS is a useful indicator of domain states: if MRS =MS < 0:1, the sample is dominated by MD grains; if MRS =MS > 0:1, small but significant fractions of SD grains are indicated within a dominant MD assemblage. Provided that these mixed domain sizes are present within magnetite only (indicated by MRS =MS values of 0.02– 0.5), the equation X MD D .0:5 .MRS=MS // =0:48 yields an estimate of the fraction of MD grains present (Thomas, 1992). Significant fractions of hematite yield unsaturated hysteresis curves at a few sites (example from site 20 in Fig. 7) and occur most notably in the red porphyritic andesites (Table 2). At the remaining sites MRS =MS is always well below 0.5 indicating a dominance of titanomagnetite. X MD values show that this mineral is predominantly MD although 10– 20% fractions of single domain grains are always present and presumably the main carriers of the stable remanence (as indicated by the ratio X MD in Table 2).

5. Palaeomagnetic results Examples of thermal and a.f. demagnetisation of samples from the Karaman district are shown in Fig. 8. Component trajectories are usually dominated by one component subtracted at, or just above, the Curie point of magnetite. These components are of both polarities and tend to be rotated somewhat from the present-day field axis. In the context of

H. Gu¨rsoy et al. / Tectonophysics 299 (1998) 191–211

201

Fig. 6. Representative examples of thermomagnetic curves (saturation magnetisation, Js , against temperature in ºC) from lavas of this study.

Fig. 7. Examples of saturated and unsaturated hysteresis curves from lavas of this study.

this observation and the rock magnetic evidence they are, therefore, interpreted as TRMs acquired during initial cooling which record instantaneous stages in the Late Pliocene secular variation and may also have been subsequently rotated. A present field component of lower coercivity or blocking temperature is removed by demagnetisation temperatures up to 400ºC (sample 9-1 in Fig. 8) to recover normal (e.g. samples 12-3 and 17-2) or reversed (e.g. 2-6) polarity magnetisations. Approximately equal numbers of normal and reversed polarity components are present in the sampled lavas from this complex (Table 3). The young lava flows of the Karapinar district to the northeast have discrete normal polarity magnetisations evidently acquired during the Brunhes polarity chron (Fig. 9). The Late Miocene to Pliocene lavas of the Karacada˘g district are predominantly of reversed polarity with straightforward demagnetisation behaviours requiring no specific comment (Fig. 10 and Table 3). The Miocene lavas from

beneath the Hasanda˘g Volcanic Complex frequently have obvious dual-component structures and discrete higher blocking temperature=coercivity components of both polarities are identified (Fig. 10).

6. Regional interpretation For tectonic interpretation the group mean palaeomagnetic directions are compared with the presentday average dipole field in this region. Derived from a mean latitude of 37.5ºN, this has a direction of D=I D 0= C 56:9º (normal) and D=I D 180= 56:9º (reversed). Since all lavas sampled for this study, with the possible exception of those beneath the Hasanda˘g Volcano (sites 41–47), are younger than 10 Ma in age, movements of the large plates on either side of the Anatolian Block (Afro–Arabia and Eurasia) have been small and yield palaeofield reference directions which are only marginally different from

202 H. Gu¨rsoy et al. / Tectonophysics 299 (1998) 191–211 Fig. 8. Alternating field and thermal demagnetisation results from lavas in the Karaman volcanic region including the Karacada˘g Complex. The demagnetisation behaviours are shown in situ as orthogonal projections of the magnetisation vector onto the horizontal (closed squares) and vertical (open circles) planes. The demagnetisation steps are listed in temperatures (ºC) or peak alternating fields (a.f.) in milliteslas.

H. Gu¨rsoy et al. / Tectonophysics 299 (1998) 191–211 Table 3 Palaeomagnetic results from lavas of the Karaman, Karapınar, Karacada˘g and Hasanda˘g volcanic districts, central Turkey Site

N

R

k

(1) Karaman Volcanic Complex 1 5 4.93 55.7 2 6 5.89 44.8 3 7 6.98 347.9 4 6 5.82 28.0 5 6 5.92 60.3 6 6 5.95 97.7 7 7 6.97 186.7 8 6 5.98 261.7 9 7 6.94 92.7 10 7 6.96 140.2 11 7 6.85 40.1 12 7 6.97 225.7 13 7 6.99 458.9 14 3 2.94 35.2 15 7 6.98 329.5 16 6 5.97 161.5 17 7 6.95 117.2 18 6 5.94 84.9

/95

D

10.3 10.1 3.2 12.9 8.7 6.8 4.4 4.1 6.3 5.1 9.6 4.0 2.8 21.1 3.3 5.3 5.6 7.3

285.5 216.7 188.2 6.6 174.7 206.3 172.8 174.8 44.1 166.3 2.4 348.1 29.2 191.4 143.8 147.6 6.7 290.3

12.3 55.7 53.3 a 43.0 a 48.1 a 20.8 49.1 a 39.8 a 41.1 67.9 a 70.5 a 33.0 a 63.2 a 65.0 a 38.8 a 40.4 a 44.9 a 82.7

337.0

30.7 a

337.9 318.6 358.0 334.9

40.4 a 53.5 a 55.2 a 28.4 a

13.0 3.9 17.1 6.5 9.5 3.9 11.8 6.8 16.7 6.0 4.4 4.9 7.8 6.0 5.7

211.1 162.1 258.4 181.0 194.3 8.3 7.3 188.7 167.3 352.0 172.9 194.1 155.3 162.5 356.3

10.0 59.9 a 11.7 73.9 a 47.0 a 44.4 a 67.0 a 49.4 a 41.7 a 75.9 a 58.8 a 60.4 a 65.3 a 42.1 a 55.2 a

3.6 9.9 11.6 6.3 6.4

341.8 168.5 222.2 174.4 323.8

50.1 a 54.3 a 74.8 a 41.5 a 63.9 a

(2) Young volcanic field, Karapınar 19 6 5.88 42.4 10.4 20 no groupings recognised 21 7 6.90 50.3 7.8 22 5 4.98 182.9 5.7 23 5 4.99 483.0 3.4 24 7 6.96 163.5 4.7 (3) Karacada˘g Volcanic Complex 25 3 2.98 90.7 26 6 5.98 298.5 27 5 4.81 21.0 28 7 6.93 87.1 29 (1) 7 6.85 41.2 (2) 7 6.98 244.5 30 7 6.79 28.2 31 7 6.93 80.4 32 3 2.96 55.6 33 6 5.98 125.7 34 7 8.97 181.9 35 5 4.98 249.4 36 6 5.93 74.2 37 6 5.96 126.5 38 7 6.95 111.3 39 no groupings recognised 40 no groupings recognised (4) Hasanda˘g region 41 8 7.97 42 5 4.93 43 7 6.79 44 7 6.94 45 8 7.91

244.2 60.1 28.0 93.9 77.0

I

203

Table 3 (continued) Site

N

R

k

/95

D

46 47

4 6

4.00 5.88

725.6 43.1

3.4 10.3

171.8 172.4

58.9 a 52.4 a

174.3

51.8

336.9

42.2

177.5

57.6

170.1

57.6

(5) Group mean results (a) Karaman Volcanic Complex 13 lavas 12.50 24.1 8.6 (b) Young volcanic field, Karapınar 5 lavas 4.85 27.5 14.9 (c) Karacada˘g Volcanic Complex 13 lavas 12.66 35.8 7.0 (d) Hasanda˘g region 7 lavas 6.80 31.8 10.9

I

D and I are the mean declination and inclination derived from N samples from site populations given in Table 1; in a few cases N includes two cylinders cut from the same field core. R is the magnitude of the resultant vector derived from the N component directions and k in the Fisher precision parameter (D.N 1/=.N R/); Þ95 is the radius of the cone of 95% confidence about the mean direction in degrees. Where more than one component is recognised at a site they are listed from lower to higher blocking temperature=coercivity. a Site mean directions employed in the group mean calculations.

the present-day field axis. Reference normal polarity palaeofield directions in the study area calculated from the mean poles for Eurasia and Africa at 10 Ma (Besse and Courtillot, 1991) are D=I D 6:5= C 54:5º and D=I D 5:6= C 53:5º, respectively. The majority of site mean directions have inclinations within 25º of the mean normal and reversed field directions and are most obviously interpreted as thermal remanent magnetisations (TRMs) representing near-instantaneous records of the palaeosecular variation. They are thus virtual geomagnetic directions and results from a number of units of different ages are required to yield representative palaeomagnetic directions. Declinations are close to the present field axis with rather more rotated anticlockwise than clockwise so that group mean directions show small anticlockwise rotation (Table 2). A few lavas have magnetic inclinations which are anomalously shallow (sites 1, 6, 25 and 27) or are of opposite inclination to the polarity predicted from the declination (site 2). These might have acquired their magnetisations during periods of polarity transition since the time period under consideration was one of frequent reversal of the geomagnetic field; the NRM intensities are not obviously weaker than magnetisations

204 H. Gu¨rsoy et al. / Tectonophysics 299 (1998) 191–211 Fig. 9. Palaeomagnetic results from the Quaternary basaltic volcanic field at Karapinar (sites 19–24) and the Miocene lava succession on the western margin of the Hasanda˘g Volcanic Complex (sites 41–46). Directions are in situ and symbols are as for Fig. 8.

H. Gu¨rsoy et al. / Tectonophysics 299 (1998) 191–211

Fig. 10. Palaeomagnetic results from the Karacada˘g Volcanic Complex. Directions are in situ and symbols are as for Fig. 8. 205

206

H. Gu¨rsoy et al. / Tectonophysics 299 (1998) 191–211

Fig. 11. Equal area projections showing site mean directions (circles) from this study. Upper-hemisphere plots are open symbols and lower-hemisphere plots are closed symbols. Group mean axes of magnetisation (see Table 3 for site data included in mean calculations) are shown by the diamonds and the present field axis is shown by the squares.

acquired in the main field (Table 1) although formal palaeointensity study would be required to demonstrate this. One lava (9) identifies a large rotation unrepresentative of adjoining units and is therefore likely to be a local effect; the remainder of the collection defines consistent dipolar axes (Fig. 11) with means interpretable in the context of regional rotation. The tectonic rotation, R 0 , is determined by comparison of the site mean direction with the predicted palaeofield axis defined above. Both observed and reference directions will normally have confidence limits (∆D and ∆Dref , respectively). Beck (1980) proposed a confidence limit on R 0 defined p 0 by ∆R D ∆D 2 C ∆Dref . Demarest (1983) concluded that this value overestimates the errors and showed that, provided Þ95 is small and preferably less than 10º, a standard correction factor is applicable. For n ½ 6 (as is the case in 79% of sites in this study) the correction factor lies between 0.78 0 the equation and 0.80; ∆R p can then be derived from 0 2 . Only if R 0 > ∆R 0 can a ∆R D 0:8 ∆D 2 C ∆Dref rotation be regarded as significant. Three of the four group mean results yield insitu inclinations very close to the Late Miocene to Recent field and imply that the inference from field observation, namely that the lavas have not been substantially tilted since emplacement, is correct. The mean magnetic inclination from the young

lava field at Karapinar is shallow (I D 42º) but is based on only five site mean results and does not differ within confidence limits from the present field (Þ95 D 14:9º); this result is due to inclusion of two anomalously shallow inclinations at sites 19 and 24 which may result from sampling of essentially uneroded young blocky surfaces unrepresentative of flow interiors. Since the Karaman volcanic rocks are younger than 5 Ma the mean palaeomagnetic result from this complex (D=I D 354:3=51:8º, Table 3) is comparable with the present field .∆Dref D 0/ from which the apparent anticlockwise rotation does not differ significantly (∆R 0 D š6:9º). The young lavas of the Karapinar district, presumably erupted during the Brunhes polarity chron, are, however, significantly rotated anticlockwise (D D 337 š 12º) by more than 20º. This result is based on only five sites due to paucity of in-depth exposure and may not therefore be a representative palaeomagnetic field direction. However, the inference that relatively large anticlockwise rotation has occurred in Quaternary times is circumstantially suggested by two observations. Firstly, the result from reversed site 36 in an outlier of this young volcanic field to the northeast (Table 3) exhibits comparable rotation. Secondly, several sites have intermediate blocking temperature=coercivity components which are more rotated in an anticlockwise direction than the higher (and presumably primary) components (e.g. sam-

H. Gu¨rsoy et al. / Tectonophysics 299 (1998) 191–211

ples 23-4 and 41-4 in Fig. 9 and sample 34-4 in Fig. 10). The Karacada˘g Complex and lavas beneath the Hasanda˘g Volcano are Late Miocene to Pliocene in age and declinations (D D 357:5 š 5:9º and 350:1 š 8:9º) merit comparison with the palaeofield directions predicted for this region at 10 Ma from the African and Eurasian APW paths. The predicted rotations are: Afro–Arabia: Eurasia: Karacada˘g 8:1 š 5:9º 9:0 š 5:9º Hasanda˘g 15:5 š 8:9º 16:4 š 8:9º Thus significant anticlockwise rotation of these regions is recognised since Early Pliocene times although the amount of rotation is smaller than the typical rotation recognised in the interior of the Anatolian Block to the north (Tatar et al., 1996). We also make the tentative observation that a phase of clockwise rotation may have been overtaken in this region by the present phase of anticlockwise rotation during late Quaternary times. A record of accelerated regional rotation during Quaternary times along the southern border of the Anatolian Block has emerged from the Sivas Basin bordering the Ecemi¸s Fault Zone 400 km to the northeast (Fig. 12, Table 4). Here mean anticlockwise rotations resolved from Miocene, Pliocene and Quaternary rocks of 34º, 25º and 28º imply that the bulk of the regional rotation has been concentrated within the last part of the neotectonic history (Gu¨rsoy et al., 1997). An implication is that postcollisional deformation was initially accommodated by crustal thickening during Miocene and Pliocene times, whilst regional rotations recording lateral escape of the Anatolian Block commenced in a major way when this thickening could no longer be sustained.

7. Discussion and conclusions Previous palaeomagnetic studies in central Turkey have recognised a variable anticlockwise rotation on both sides of the NAFZ (Baydemir, 1990; Platzman et al., 1994; Tatar et al., 1995; Piper et al., 1996). In the Almus region sited between the NAFZ and directly north of the sector of the Central Anatolian

207

Thrust Tatar et al. (1995) identify 34º of rotation in Eocene rocks which compares with an anticlockwise rotation of 26º on the north side of the NAFZ. Further to the east Baydemir (1990) also used rocks of Eocene age to identify a larger anticlockwise rotation of between 44 and 53º in the ˙Imranlı region 100 km east of Sivas. In each case the magnitude of rotation south of the NAFZ has proved to be larger than the rotation in equivalent rocks north of the fault suggesting that differential rotation is occurring by extrusion of blocks along lateral side splays to the main fault. Rock units older than Middle Miocene in age were emplaced during the palaeotectonic history and their cumulative rotations are therefore likely to be a composite of deformation during both the palaeotectonic and neotectonic regimes. Nevertheless rotations recognised in Eocene units are comparable over a large area of central Anatolia (Tatar et al., 1996) and north of the NAFZ (Sarıbudak, 1989), and prove to be similar to rotations recognised in neotectonic rock units (Fig. 12). The regional implication of this observation is that major differential rotations did not occur during continental collision associated with emplacement of Pontide and Tauride belts. Tectonic rotation in this study is recognised in Quaternary rocks and although we are unable to temporally constrain rotation in the older Late Miocene– Pliocene rocks, the presence of rotation similar to that in palaeotectonic rocks does suggest that most regional rotation along this southern margin of the Anatolian Block has been concentrated within the last part of the neotectonic regime as is also recognised in the Sivas Basin (Fig. 12). Thus regional rotation in Anatolia considerably post-dates initiation of the NAFZ. The older limit to the age of this intracontinental transform is the final orogenic shaping of the Pontide=Anatolide suture which occurred during Late Miocene (Burdigalian) times (Seymen, 1975). It therefore seems probable that post-collisional deformation in the NNW-directed compressional regime around the northern margin of the Arabian Plate (Fig. 12) was accommodated mainly by crustal thickening during Late Miocene and Pliocene times. In Late Pliocene times this accommodation could no longer be sustained and a regime dominated by lateral extrusion of fault blocks has taken over.

208

H. Gu¨rsoy et al. / Tectonophysics 299 (1998) 191–211

Fig. 12. Group mean palaeomagnetic directions with Þ95 confidence limits from Late Cretaceous and Cenozoic rock units in central Turkey based on the compilation of Table 4. All directions are shown as reversed polarity fields (with the exception of the third result from the Re¸sadiye area which is shown as a normal polarity direction for clarity). Note that results from rock units emplaced in the palaeotectonic regime may include rotations imparted during continental collision, whereas rotations of rock units emplaced during the neotectonic regime are assigned to this phase of deformation only.

H. Gu¨rsoy et al. / Tectonophysics 299 (1998) 191–211

209

Table 4 Summary of Cenozoic palaeomagnetic results from central Turkey Fault block

Location ºE

Palaeomagnetic direction ºN

N

D

/95

Reference

I

(a) Results from rock units emplaced during the palaeotectonic regime (1) North of the NAFZ Mesudiye (N) 37.7 40.6 7 165.9 Mesudiye (R) 37.7 40.6 8 185.6 Niksar 37.0 40.7 10 152.4 Erbaa 36.3 40.8 7 194.6 Mesudiye 37.7 40.5 7 166.8 Kusuri 35.7 41.5 5 161.2 Kastamonu 33.7 41.2 3 164.2

50.4 45.1 42.5 48.8 49.9 48.4 31.7

6.7 15.1 11.3 15.3 9.6 12.9 10.6

Baydemir, 1990 Baydemir, 1990 Tatar et al., 1995 Piper et al., 1996 Orbay and Bayburdi, 1979 Sarıbudak, 1989 Piper et al., 1996

(2) South of the NAFZ Imranli 38.4 Almus 36.9 Kalehisar 34.5 Akdagmadeni 35.8 Yozgat 34.7 Iskilip 34.5

34.2 47.5 51.0 43.5 46.5 47.1

6.3 7.6 5.2 5.2 18.6 7.7

Baydemir, 1990 Tatar et al., 1995 Piper et al., 1996 Tatar et al., 1996 Tatar et al., 1996 Tatar et al., 1996

47.6 50.8 55.0 47.9 54.1 60.8 32.2 37.3 49.6 33.3 47.7 40.9 37.2 51.8 42.2 57.6 57.6

19.9 11.9 10.9 15.6 14.0 9.6 6.7 7.7 10.0 8.8 7.2 5.3 4.3 8.6 14.9 7.0 10.9

Gu¨rsoy et al., 1997 Gu¨rsoy et al., 1997 Gu¨rsoy et al., 1997 Gu¨rsoy et al., 1997 Gu¨rsoy et al., 1997 Krijgsman et al., 1996 Krijgsman et al., 1996 Krijgsman et al., 1996 Krijgsman et al., 1996 Krijgsman et al., 1996 Krijgsman et al., 1996 Krijgsman et al., 1996 Krijgsman et al., 1996 This paper This paper This paper This paper

(b) Results from rock CATB Yildizeli Sarkisla Kangal Gu¨ru¨n Gemerek (R) Gemerek (N) Inkonak (R) Inkonak (N) Yeniko¨y (R) Yeniko¨y (N) Haramiko¨y (R) Haramiko¨y (N) Karaman Karapınar Karacada˘g Hasanda˘g

39.8 40.4 40.2 39.7 39.8 40.8

10 8 5 3 5 7

146.0 144.1 160.4 133.9 158.4 173.3

units emplaced during the neotectonic regime 36.5 39.8 5 169.7 36.9 39.8 12 150.9 37.0 39.5 18 147.9 37.0 39.0 6 129.6 37.2 38.8 7 157.0 36.0 39.2 35 111.9 41 307.9 37.0 39.4 30 129.8 30 307.1 36.4 39.1 49 126.3 32 329.6 31.8 38.5 37 190.1 45 2.4 33.2 37.2 13 174.3 33.6 37.5 5 156.9 33.7 37.7 13 177.5 34.2 38.0 7 170.1

N is the number of separate units included in the calculated mean and Þ95 is the radius of the cone of 95% confidence about the mean direction. CATB D Central Anatolian Thrust Belt.

The major tectonic boundaries defining the southeastern margin of the Anatolian Block are the subparallel Ecemi¸s and East Anatolian Fault Zones (Fig. 12). The former exhibits a lower level of seismic activity than the latter (Demirta¸s and Yılmaz, 1996), but is interpreted by Koc¸yi˘git and Beyhan (1998) as a sinistral intracontinental transform (the Central Anatolian Fault Zone, CAFZ) conjugate to the Salt Lake Fault (SLF, Fig. 1A and Fig. 12); because subduction is currently inactive along the

eastern part of the Cyprus arc whilst it remains active in the western part of the arc, it is speculated that the Ecemi¸s Fault Zone may in the future replace the East Anatolian Fault as a tectonic boundary of the Anatolian Block. Current neotectonic rotations across this zone are comparable to the Anatolian Block to the northwest (Fig. 12). Rotations defined by the present study southwest of the Ecemi¸s and Salt Lake Faults are, however, lower and imply that the CAFZ and SLF are block boundaries separating

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zones of contrasting (presumed Quaternary) deformation (Fig. 12). Crustal deformation to the west of the present study area must be considered in the context of deformation around the Isparta angle (Fig. 1A). This feature is generally interpreted as the result of interference between southeast vergence of the eastward extension of the Aegean Arc (the Lycian Taurides) and the southwest vergence of the western Taurides sensu stricto (Robertson and Woodcock, 1984). This general model is supported by post-Early Miocene rotations of 30º anticlockwise and 0º in the western and central parts of the arc respectively, and by post-Eocene clockwise rotation of 40º in the eastern sector of the arc (Kissel et al., 1993). Whilst the evolution of the Isparta syntaxis has still to be constrained in temporal terms, and in particular that part of the rotation applicable to the neotectonic evolution of the Anatolian Block requires definition, we suspect the anticlockwise regime in the eastern part of the block will prove to be replaced westwards by a regime of clockwise rotation. The low amounts of rotation identified in the present study area (together with the suggestion of successive clockwise and anticlockwise rotational histories) are consistent with this supposition.

Acknowledgements This study has been facilitated by a link between the University of Cumhuriyet, Sivas and the Geomagnetism Laboratory of the University of Liverpool ¨ B˙ITAK. supported by the British Council and TU

References ¨ ver, S., Poisson, A., Bellier, O., 1995. The North Andrieux, J., O Anatolian Fault Zone: distributed Neogene deformation in its northwest convex part. Tectonophysics 243, 135–154. Barka, A., Reilinger, R., Saroglu, ¸ F., Sengo ¸ ¨ r, A.M.C., 1997. The Isparta angle: its importance in the neotectonics of the eastern Mediterranean region. IESCA-1995, pp. 1–17. Batum, I., 1978a. Nev¸sehir gu¨neybatısındaki Go¨llu¨da˘g ve Acıgo¨l yo¨resi volkanitlerinin jeolojisi ve petrografisi. Yerbilimleri 4 (12), 50–69. Batum, I., 1978b. Nev¸sehir gu¨ney batısındaki Go¨llu¨da˘g ve Acıgo¨l yo¨resi volkanitlerinin jeokimyası ve petrolojisi. Yerbilimleri 4 (12), 70–88.

Baydemir, N., 1990. Palaeomagnetism of the Eocene volcanic rocks in the eastern Black Sea region (in Turkish). Istanbul Univ. Mu¨h. Fak., Yerbilimleri Dergisi 7, 167–176. Beck, M.E., 1980. Palaeomagnetic record of plate margin processes along the western edge of North America. J. Geophys. Res. 87, 7115–7131. Besang, C., Eckhardth, F.J., Harre, W., Kreuzer, H., Mu¨ller, P., 1977. Radiometrische Altersbestimmungen an neogenen Eruptivgesteinen der Turkei. Geol. Jahrb. B 25, 3–36. Besse, J., Courtillot, V., 1991. Revised and synthetic apparent polar wander paths of the African, Eurasian, North American and Indian Plates, and true polar wander since 200 Ma. J. Geophys. Res. 96, 4029–4050. Bingo¨l, E., 1989. 1=2,000,000 scaled geological map of Turkey. MTA Publications, Ankara. Demarest, H.H., 1983. Error analysis for the determination of tectonic rotation from palaeomagnetic data. J. Geophys. Res. 88, 4321–4328. Demirta¸s, R., Yılmaz, R., 1996. Seismotectonics of Turkey. Ministry of Public Works and Settlement, Ankara, 95 pp. Ercan, T., 1986. Orta Anadolu’daki Senozoyik volkanizmasi. MTA Derg. 107, 119–140. Ercan, T., Fujitani, T., Matsuda, J.I., Tokel, S., Notsu, K., Ui, ¨ lmez, M., T., Can, B., Selvi, Y., Yildirim, T., Fi¸sekc¸i, A., O Akba¸slı, A., 1990. The origin and evolution of the Cenozoic volcanism of Hasanda˘gı–Karacada˘g area, Central Anatolia (in Turkish). Bull. Geomorphol. 18, 39–54. Ercan, T., Tokel, S., Matsuda, J.I., Ui, T., Notsu, K., Fujitani, T., 1992. Hasanda˘gı–Karacada˘g (Orta Anadolu) Kuvaterner volkanizmasina ili¸skin yeni jeokimyasal, izotopik ve radyometrik veriler, 45, Tu¨rkiye Jeol. Kurul, Bildiri o¨zleri, 46. Gromme´, S., Wright, T.L., Peck, D.L., 1969. Magnetic properties and oxidation of iron–titanium oxide minerals in Alea and Makaopuhi lava lakes, Hawaii. J. Geophys. Res. 74, 5277– 5293. Guezou, J.C., Temiz, H., Poisson, A., Gu¨rsoy, H., 1996. Tectonics of the Sivas Basin: Neogene record of the Anatolian Accretion along the Inner Tauric suture. Int. Geol. Rev. 38, 901–925. Gu¨rsoy, H., Piper, J.D.A., Tatar, O., Temiz, H., 1997. A palaeomagnetic study of the Sivas Basin, Central Turkey: crustal deformation during lateral extrusion of the Anatolian Block. Tectonophysics 271, 89–105. Haggerty, S.E., 1976. Oxidation of opaque mineral oxides in basalts. In: Rumble, D. (Ed.), Oxide Minerals. Mineral. Soc. Am., Short Course Notes 3, 1–98. Innocenti, F., Mazzuoli, R., Pasquare, G., Redicati de Brozolo, F., Villari, L., 1975. The Neogene calk-alkaline volcanism of central Anatolia: geochronological data from the Kayseri– Ni˘gde area. Geol. Mag. 112, 349–360. Kiratzi, A.A., 1993. A study on the active crustal deformation of the North and East Anatolian Fault zones. Tectonophysics 225, 191–203. Kissel, K., Averbuch, O., Frizon de Lamotte, D., Monod, O., Allerton, S., 1993. First palaeomagnetic evidence for a postEocene clockwise rotation of the Western Taurides thrust belt

H. Gu¨rsoy et al. / Tectonophysics 299 (1998) 191–211 east of the Isparta reentrant (southwestern Turkey). Earth Planet. Sci. Lett. 117, 1–14. Koc¸yi˘git, A., 1996. Superimposed basins and their relations to the Recent strike-slip fault zone: a case study of the Refahiye superimposed basin adjacent to the North Anatolian transform fault, northeastern Turkey. Int. Geol. Rev. 38, 701–713. Koc¸yi˘git, A., Beyhan, A., 1998. A new intracontinental transcurrent structure: the central Anatolian Fault Zone, Turkey. Tectonophysics 284, 317–336. Krijgsman, W., Duermeijer, C.E., Langereis, C.G., Bruijn, H., Sarac¸, G., Andriessen, P.A.M., 1996. Magnetic polarity stratigraphy of late Oligocene to middle Miocene mammal-bearing continental deposits in central Anatolia (Turkey). Newsl. Stratigr. 34 (1), 13–29. Mantovani, E., Albarello, D., Babbucci, D., Tamburelli, C., 1993. Post-Tortonian deformation pattern in the central Mediterranean: a result of extrusion tectonics driven by the African– Eurasia convergence. In: Bochi, E. (Ed.), Recent Evolution and Seismicity of the Mediterranean Region. Kluwer, Dordrecht, pp. 65–104. Olanca, K., Vidal, G., Gougaud, A., Gillot, P.Y., 1992. Calcalkaline volcanism from Central Anatolia in the Quaternary: geochemistry and mineralogy (abstr.). First Turkish Geology Workshop, Keele, p. 42. Oral, M.B., Reilinger, R.E., Tokso¨z, M.N., King, R.W., Barka, A.A., Kınık, I., Lenk, O., 1995. Global positioning system offers evidence of plate motions in eastern Mediterranean. Eos 76 (2), 9–11. Orbay, N., Bayburdi, A., 1979. Palaeomagnetism of dykes and tuffs from the Mesudiye region and rotation of Turkey. Geophys. J. R. Astron. Soc. 59, 437–444. Pasquare, G., 1968. Geology of the Cenozoic volcanic area of Central Anatolia. Atti. Accad. Naz. Lincei Mem. 9, 55–204. Pasquare, G., Venzolli, L., Zanchi, A.M., 1988. Continental arc volcanism and tectonic setting in Central Anatolia, Turkey. Tectonophysics 146, 217–230. Piper, J.D.A., Moore, J., Tatar, O., Gu¨rsoy, H., Park, R.G., 1996. Palaeomagnetic study of crustal deformation across an intracontinental transform: the North Anatolian Fault Zone in Northern Turkey. In: Morris, A., Tarling, D.H. (Eds.), Palaeomagnetism and Tectonics of the Mediterranean Regions. Geol. Soc. London, Spec. Publ. 105, 299–310. Platzman, E.S., Platt, J.P., Tapırdamaz, C., Sanver, M., Rundle, C.C., 1994. Why are there no clockwise rotations along the North Anatolian Fault Zone? J. Geophys. Res. 99, 21705–

211

21716. Robertson, A.F., Woodcock, N.H., 1984. The SW segment of the Antalya complex, Turkey, as a Mesozoic–Tertiary Tethyan continental margin. In: Robertson, A.F., Woodcock, N.H. (Eds.), The Geological Evolution of the Eastern Mediterranean. Geol. Soc. London, Spec. Publ. 17, 217–237. Sarıbudak, M., 1989. New results and a palaeomagnetic overview of the Pontides in northern Turkey. Geophys. J. Int. 90, 521– 531. Seymen, I., 1975. Kelkit Vadisi kesiminde Kuzey Anadolu Fay Zonunun tektonik o¨zelli˘gi. PhD. Thesis, Istanbul Technical University, 192 pp. Sengo ¸ ¨ r, A.M.C., 1979. North Anatolian Fault: its age, offset and tectonic significance. J. Geol. Soc. London 136, 269–282. Sengo ¸ ¨ r, A.M.C., 1980. Turkiye’nin neotektoniginin esaslari (Principles of Neotectonics in Turkey). Geol. Soc. Turkey Conf. Ser. 2, 40 pp. Sengo ¸ ¨ r, A.M.C., 1984. Tu¨rkiye’nin tektonik tarihinin yapısal sınıflaması, Ketin Sempozyumu, Ankara, pp. 37–62. Sengo ¸ ¨ r, A.M.C., Go¨ru¨r, N., Saro˘ ¸ glu, F., 1985. Strike slip faulting and related basin formation in zones of tectonic escape: Turkey as a case study. In: Biddle, K.T., Christie-Blick, N. (Eds.), Strike Slip Deformation, Basin Formation and Sedimentation. Soc. Econ. Palaeontol. Mineral. Spec. Publ. 37, 227–264. Tatar, O., Piper, J.D.A., Park, R.G., Gu¨rsoy, H., 1995. Palaeomagnetic study of block rotations in the Niksar overlap region of the North Anatolian Fault Zone, Central Turkey. Tectonophysics 244, 251–266. Tatar, O., Piper, J.D.A., Gu¨rsoy, H., Temiz, H., 1996. Regional significance of Neotectonic counterclockwise rotation in Central Turkey. Int. Geol. Rev. 38, 692–700. Temel, A., 1992. Kapadokya eksplosif volkanizmasının petrolojik ve jeokimyasal o¨zellikleri. PhD. Thesis, Hacettepe University, Ankara, 209 pp. Thomas, D.N., 1992. Rock Magnetic and Palaeomagnetic Investigations of the Gardar Lava Succession, South Greenland. PhD. Thesis, University of Liverpool, 513 pp. Tokel, S., Ercan, T., Akba¸slı, A., Yıldıriı, T., Fi¸sekc¸i, A., Selvi, ¨ lmez, M., Can, B., 1988. Neogene tholeiitic province Y., O of central Anatolia: implication for magma genesis and postcollision lithospheric dynamics. Tokay Symposium. METU J. Pure Appl. Sci. 21, 461–477. Toprak, V., Go¨ncu¨o˘glu, M.C., 1993. Tectonic control on the development of the Neogene–Quaternary Central Anatolian Volcanic Province, Turkey. Geol. J. 28, 357–369.