Kinematic and structural development of the Çankiri Basin (Central Anatolia, Turkey): a paleostress inversion study

Kinematic and structural development of the Çankiri Basin (Central Anatolia, Turkey): a paleostress inversion study

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  Kinematic and structural development of the C  ankiri Basin(Central Anatolia, Turkey): a paleostress inversion study  Nuretdin Kaymakci a, *, Stanley H. White  b , Paul M. Vandijk  c a  Geological Engineering Department, Faculty of Engineering, Middle East Technical University, 06531-Ankara, Turkey  b  Faculty of Earth Sciences, Utrecht University, Budapestlaan 4, 3508 Utrecht, The Netherlands c  ITC Hengelosestr 99, P.O. Box 6, 7500 AA Enschede, The Netherlands Received 13 November 2002; accepted 23 January 2003 Abstract Three different deformation phases have been recognized in the southern part of the C  ankırı Basin from (1) the major structures and (2) through using paleostress inversion techniques for fault slip data. The deformation phases recognized from the paleostress data are correlated with those recognized from the major structures and dated accordingly. The first phase occurredin the Late Paleocene to pre-Burdigalian and is characterized by an oblique  r 2  and NNE–SSW to NE–SW trendingsubhorizontal  r 1  and WNW–ESE to NW–SE trending  r 3  patterns which indicate transcurrent deformation associated with acombination of thrusting and strike slip faulting (transpression) possibly due to indentation of the Kırs  ehir Block to the SakaryaContinent. The second phase occurred from the Burdigalian to the Serravallian and is characterized by a subvertical  r 1  andoblique  r 2  and  r 3 , which indicate oblique extension associated with normal faulting possibly due to a post-orogenic collapse.The third deformation phase is characterized by a vertical  r 2  while the other stresses were horizontal, which indicate regionaltranscurrent tectonics, which is correlated with the current transcurrent tectonics controlled by the North Anatolian Fault Zone. D  2003 Elsevier Science B.V. All rights reserved.  Keywords:  Paleostress inversion; C  ankırı; Kinematics; Transcurrent; Turkey 1. Introduction Paleostress inversion methods provide an estima-tion of the orientation of the principal stress axesusing fault slip data sets. The direction of slip isinferred from the fault slip data, which are assumedto record the direction of maximum shear stress on afault surface (Carey and Brunier, 1974; Etchecopar et al., 1981; Angelier, 1979, 1984, 1994; Petit andLaville, 1985; Means, 1987; Reches, 1987; Krantz,1988; Lisle, 1987; Doblas, 1998). The faults in three dimension may conform to the Coloumb criterion, but due to anisotropy and inherited planes of weakness,faults may develop at angles to principal stress direc-tions other than those predicted for isotropic media(Wojtal and Pershing, 1991). Wallace (1951) and Bott  (1959) suggested that slip on pre-existing surfacesoccurs parallel to the maximum resolved shear stress.After the pioneering paleostress inversion techniqueof  Carey and Brunier (1974), a number of paleostress techniques have been developed. They have been 0040-1951/03/$ - see front matter   D  2003 Elsevier Science B.V. All rights reserved.doi:10.1016/S0040-1951(03)00043-X* Corresponding author.  E-mail addresses: (N. Kaymakci), (S.H. White), (P.M. Vandijk) 364 (2003) 85–113   N. Kaymakci et al. / Tectonophysics 364 (2003) 85–113 86  applied to fault slip data for a variety of tectoniccontext with consistent results. Thanks to this success, paleostress inversion procedures are becoming a rou-tine analytical technique in structural geology (Pollardet al., 1993).The purposes of this study are to apply paleostressinversion techniques to unravel the paleostress historyof the southern part of the C  ankırı Basin, includingthe Kırs  ehir Block (basement), and to constrain thetiming of each deformation phase. We relate theresults to the major structures that were active duringeach deformation phase. This is a complement toanother study carried out in the northern part of theC  ankırı Basin. Therefore, the numbering of subareasand the analytical and numerical procedures followthose outlined in detail in Kaymakci et al. (2000) and briefly described in Section 3. 2. Regional setting The C  ankırı Basin lies adjacent to the I˙zmir– Ankara–Erzincan Suture Zone along which theSakarya continent  (Pontides) and the Kırs  ehir Block (Taurides) (Fig. 1) are thought to have collided and amalgamated (S  engo n        r and Yılmaz, 1981; Tu n        ysu n        zand Dellalog˘lu, 1992). Besides being affected bycollisional processes, the C  ankırı Basin was sub- jected to further deformation in the post-Late Mio-cene as part of the Anatolian wedge caught betweenthe transcurrent  motions on the North and East Anatolian Faults (Fig. 1). This has resulted in a number of northwards convex dextral strike-slipfaults, which bifurcate from the North AnatolianFault Zone (NAFZ) (Barka and Hancock, 1984;S  engo n        r et al., 1985; Kaymakci and Koc  yig˘it, 1995).The Kızılırmak and Sungurlu Fault Zones are thetwo major splays of the NAFZ in this area, which partly controlled the Late Miocene evolution of theC  ankırı Basin (Fig. 2).The major structures defining the western, northernand eastern margin of the C  ankırı Basin are com pres-sional (Kaymakci, 2000; Kaymakci et al., 2000). They define a distinctive V -shape to the C  ankırı Basin (Figs.1 and 2). Along these faults, an ophiolitic me´lange andassociated Late Cretaceous volcano-sedimentary suc-cessions have been thrust over the basin fill (Akyu n       rek et al., 1984; Dellalog˘lu et al., 1992; Tu n        ysu n       z andDellalog˘lu, 1992; O n        zc  elik, 1994; Koc  yig˘it et al.,1995; Kaymakci et al., 1998, 2000). To the south,the granitoids of the Kırs  ehir Block delimit the south-ern margin of the basin and constitute the basement (Dellalog˘lu et al., 1992; Tu n        ysu n       z and Dellalog˘lu, 1992;Kaymakci, 2000).The other major structures that affected theC  ank ırı Basin are NE –SW trending strike-slip faults(see Figs. 1c and 2), namely, the Kızılırmak Fault  Zone (KFZ), Yag˘ basa Faras  lı Fault Zone (YFFZ),Sivritepe Fault Zone (STFZ) and the Ezinepazarı-Sungurlu Fault Zone (ESFZ), all of which splay off the NAFZ. They cross the basin and displace the basin fill, the rim, and the basement. The south-central part of the basin is dominated by generally NNW–SSE- to NE–SW-oriented normal faults (Fig.2). The southern area is dominated by the ESFZ, one of the major splays of the NAFZ (Fig. 1d) that partlyruptured during the Erzincan Earthquake (Mw. 7.9,26 December 1939).The fill of the C  ankırı Basin is more than 4 kmthick and accumulated during five different cycles of sedimentation (Fig. 3). The cycles are discussed in detail in Kaymakci (2000) and only a summary isgiven here. The oldest cycle comprises the LateCretaceous volcanoclastics and regressive shallowmarine units, and the Paleocene mixed environment red clastics and carbonates (O n       zc  elik, 1994; Kay-makci, 2000). The second cycle is a Paleocene toOligocene regressive flysch to molasse sequenceoverlain by a widespread thin (<100 m) nummuliticlimestone, Middle Eocene in age, that passes into very Fig. 1. (a) Inset map showing the geological outline of the Eastern Mediterranean area (modified after  Go n       ru n       r et al., 1984; S  engo n       r et al., 1984).EAAC: East Anatolian Accretionary Complex. (b) Active tectonic outline of Turkey and surrounding regions (modified after  Barka andHancock, 1984; S  engo n       r et al., 1985; Koc  yig˘it, 1989; O n       zc  elik, 1994; Kaymakci and Koc  yig˘it, 1995). C  B: C  ankırı Basin, DFZ: Dead Sea Fault Zone, EAFZ: East Anatolian Fault Zone, NAFZ: North Anatolian Fault Zone. Large black arrows are the movement directions of Arabian plateand Aegean–Anatolian Block. (c) Detailed tectono-stratigraphical map of the central Anatolia. Box shows the location of the study area.Concentric circles are major towns.  N. Kaymakci et al. / Tectonophysics 364 (2003) 85–113  87  Fig. 2. Geological map of the C  ankırı Basin. The numbers and the boxes indicate the locations of the subareas.  N .K a  y m a k   c i    e t   a l    . /   T  e c t   o n o  p h    y s  i    c s  3   6   4   (   2   0   0   3    )    8   5 –1  1   3    8   8    Fig. 3. Generalized tectono-stratigraphic column for the units exposed in and around the C  ankırı Basin. MN zones are after  Kaymakci et al.(2001b).  N. Kaymakci et al. / Tectonophysics 364 (2003) 85–113  89
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