NAFİZ MADEN, KENAN GELİŞLİ, YENER EYÜBOĞLU & OSMAN BEKTAŞ

Two-and-Three-Dimensional Crustal Thickness of the Eastern Pontides (NE Turkey)

The Eastern Pontide orogenic belt is divided into three subzones (northern, southern and axial zones) based on present lithologies and facies associations. NE-SW-, NW-SE- and E-W-trending fault systems, which play an important role in palaeotectonics and neotectonics of the Eastern Pontides, separate these zones. Three different methods were used to estimate the Moho depth from observed gravity value, namely (i) empirical relationship between Moho depth and Bouguer anomaly; (ii) spectral analysis of the radial wave number and; (iii) by the gravity inversion method. Power spectrum, a statistical approach, is a widely used technique to determine the depth of geological sources successfully. The empirical linear relations between the Bouguer anomalies and seismically determined crustal thicknesses have been used to compute depths to the Conrad and Moho discontinuities, which are consistent with the average depths obtained from the power spectrum method. The crustal structure was also determined from the inversion of a Bouguer anomaly profile along longitude 39°. Gravity inversion results are consistent with those obtained from the empirical relations and power spectrum methods. We calculated the maximum crustal thickness of 43.8 km in the studied region by using the gravity inversion method, which also showed that crustal thickness increases from north to south.

Anahtar Kelimeler:

Eastern Pontides, crustal structure, moho depth, Bouguer gravity, gravity inversion

Two-and-Three-Dimensional Crustal Thickness of the Eastern Pontides (NE Turkey)

Keywords:

Eastern Pontides, crustal structure, moho depth, Bouguer gravity, gravity inversion,

PDF

___

ADAMIA, S., LORDKIPANIDZE, M.B. & ZAKARIADZE, G.S. 1977. Evolution of an active continental margin as exemplified by the Alpine history of the Caucasus. Tectonophysics 40, 183–189.
AL-LAZKI, A., SANDVOL, E., SEBER, D., TÜRKELLİ, N., MOHAMAD, R. & BARAZANGI, M. 2003. Tomographic Pn velocity and anisotropy structure beneath the Anatolian plateau (Eastern Turkey) and the surrounding regions. Geophysical Research Letters 30, 8043.
ATEŞ, A., BİLİM, F. & BÜYÜKSARAÇ, A. 2005. Curie point depth investigation of Central Anatolia, Turkey. Pure and Applied Geophysics 162, 357–371.
BANSAL, A.R. & DIMRI, V.P. 2001. Depth estimation from the scaling power spectral density of nonstationary gravity profile. Pure and Applied Geophysics 158, 799–812.
BANSAL, A.R., DIMRI, V.P. & SAGAR, G.V. 2006. Depth estimation from gravity data using the maximum entropy method (MEM) and the multi taper method (MTM). Pure and Applied Geophysics 163, 1417–1434
BEKTAŞ, O. 1986. Paleostress trajectories and polyphase rifting in arc- back arc of Eastern Pontides. Mineral Research and Exploration Institute (MTA) Bulletin 103/104, 1–15.
BEKTAŞ, O. & ÇAPKINOĞLU, Ş. 1997. Neptunian dikes and block tectonics in the Eastern Pontide magmatic arc, NE Turkey, implications for the kinematics of the Mesozoic basins. Geosound 30, 451–461.
BEKTAŞ, O. & GÜVEN, İ.H. 1995. Alaskan appinitic type ultramafic and mafic complexes as the root zone of the Eastern Pontide magmatic arc (NE Turkey).International, Symposium on the Geology of the Black Sea Region, Proceedings, 189–196.
BEKTAŞ, O., ŞEN, C., ATICI, Y. & KÖPRÜBAŞI, N. 1999. Migration of the upper Cretaceous subduction-related volcanism towards the back- arc basin of the Eastern Pontide magmatic arc (NE Turkey). Geological Journal 34, 95–106.
BHATTACHARYA, B.K. 1966. Continuous spectrum of the total magnetic anomaly due to a rectangular prismatic body. Geophysics 31, 97– 121.
BHATTACHARYYA, B.K. & LEU, L.K. 1975. Spectral analysis of gravity and magnetic anomalies due to two-dimensional structures. Geophysics 40, 993–1013.
BHATTACHARYYA, B.K. & LEU, L.K. 1977. Spectral analysis of gravity and magnetic anomalies due to rectangular prismatic bodies. Geophysics 42, 41–50.
BOZKURT, E. 2001. Neotectonics of Turkey – a synthesis. Geodinamica Acta 14, 3–30.
BURKE, K. & ŞENGÖR, A.M.C. 1986. Tectonic escape in the evolution of the continental crust. In: BARAZANGI, M. (ed), Reflection Seismology, Continental Crust, Geodynamic Series, 14. American Geophysical Union Special Publication, 41–51.
CHAVEZ, R.E., LAZARO-MANCILLA, O., CAMPOS-ENRIQUEZ, J.O. & FLORES- MARQUEZ, E.L. 1999. Basement topography of the Mexicali valley from spectral and ideal body analysis of gravity data. Journal of South American Earth Sciences 12, 579–587.
CHOROWICZ, J., DHONT, D. & ADIYAMAN, Ö. 1998. Black Sea-Pontide relationship: interpretation in terms of subduction.Third International Turkish Geology Symposium, Abstracts, p. 258.
CURTIS, C.E. & JAIN, S. 1975. Determination of volcanic thickness and underlying structures from aeromagnetic maps of the Silet area of Algeria. Geophysics 40, 79–90.
DEBARI, S.M. & SLEEP, N.H. 1991. High-Mg, low-Al bulk composition of the Talkeetna island arc, Alaska; implications for primary magmas and the nature of arc crust. Geological Society of America Bulletin 103, 33–47.
DEMENITSKAYA, R.M. 1967. Crust and Mantle of the Earth. Nedra, Moscow.
DEWEY, J.F., PITMAN, W.C., RYAN, W.B.F. & BONIN, J. 1973. Plate tectonics and the evolution of the Alpine system. Geological Society of America Bulletin 84, 3137–3180.
DEWEY, J.F., HEMPTON, M.R., KIDD, W.S.F., ŞAROĞLU, F. & ŞENGÖR, A.M.C. 1986. Shortening of continental lithosphere; the neotectonics of Eastern Anatolia, a young collision zone. In: COWARD, M.P. & RIES, A.C. (eds), Collision Tectonics. Geological Society, London, Special Publications 19, 3–36.
DIMITRIADIS, K., TSELENTIS, G.A. & THANASSOULAS, K. 1987. A basic program for 2-D spectral analysis of gravity data and source depth determination. Computers and Geosciences 13, 549–560.
DOLMAZ, M.N., HISARLI, Z.M., USTAÖMER, T. & ORBAY, N. 2005. Curie point depths based on spectrum analysis of aeromagnetic data, West Anatolian extensional province, Turkey. Pure and Applied Geophysics 162, 571–590.
EYÜBOĞLU, Y., BEKTAŞ, O., ŞEREN, A., MADEN, N., ÖZER, R. & JACOBY, W.R. 2006. Three-directional extensional deformation and formation of the Liassic rift basins in the Eastern Pontides (NE Turkey). Geologica Carpathica 57, 337–346.
EYÜBOĞLU, Y., BEKTAŞ, O. & PUL, D. 2007. Mid-Cretaceous olistostromal ophiolitic melange developed in the back-arc basin of the eastern Pontide magmatic arc (NE Turkey). International Geology Review 49, 1103–1126.
FLIEDNER, M.M. & KLEMPERER, S.L. 1999. Structure of an island arc: wide- angle seismic studies in the eastern Aleutian Islands, Alaska. Journal of Geophysical Research 104, 10667–10694.
GÖK, R., SANDVOL, E., TÜRKELLİ, N., SEBER, D. & BARAZANGI, M. 2003. Sn attenuation in the Anatolian and Iranian plateaus and surrounding regions. Geophysical Research Letters 30, 8042.
GÖK, R., PASYANOS, M.E. & ZOR, E. 2007. Lithospheric structure of the continent-continent collision zone: eastern Turkey. Geophysical Journal International 169, 1079–1088.
GOMEZ-ORTIZ, D., TEJERO-LOPEZ, R., BABIN-VICH, R. & RIVAS-PONCE, A. 2005. Crustal density structure in the Spanish Central System derived from gravity data analysis (Central Spain). Tectonophysics 403, 131–149
HOFSTETTER, A., DORBATH, C., RYBAKOV, M. & GOLDSHMIDT, V. 2000. Crustal and upper mantle structure across the Dead Sea rift and Israel from teleseismic P-wave tomography and gravity data. Tectonophysics 327, 37–59.
KISHIRO, I. 1987. A petrological model of the mantle wedge and lower crust in the Japanese island arcs. In: MYSEN, B.O. (ed), Magmatic Processes, Physicochemical Principles. Geochemical Society, London, Special Publications 1, 165–181.
LEFORT, J.P. & AGARWAL, B.N.P. 2002. Topography of the Moho undulations in France from gravity data: their age and origin. Tectonophysics 350, 193–213.
MADEN, N. 2005.Doğu Pontid Orojenik Kuşağının Yapı Stillerinin ve Kabuk Yapısının Jeofizik Yöntemlerle İncelenmesi [Geophysical Investigation of Eastern Pontide Orogenic Belt Structural Styles and Crust Structure]. PhD Thesis, Karadeniz Technical University, Trabzon, Turkey [in Turkish with English abstract, unpublished]
MCKENZIE, D. 1972. Active tectonics of the Mediterranean region. Geophysical Journal of the Royal Astronomical Society 30, 109– 185.
MILLER, D.J. & CHRISTIENSEN, N. 1994. Seismic signature and geochemistry of an island arc: a multidisciplinary study of the Kohistan accreted terrene, Northern Pakistan.Journal of Geophysical Research 99, 11623–11642.
MİNDEVALLI, Ö.Y. & MITCHELL, B.J. 1989. Crustal structure and possible anisotropy in Turkey from seismic surface wave dispersion. Geophysical Journal International 98, 93–106.
NNANGE, J.M., NGAKO, V., FAIRHEAD, J.D. & EBINGER, C.J. 2000. Depths to density discontinuities beneath the Adamawa plateau region, Central Africa, from spectral analyses of new and existing gravity data. Journal of African Earth Sciences 30, 887–901.
NWOGBO, P.O. 1998. Spectral prediction of magnetic sources depths from simple numerical models. Computers and Geosciences 24, 847–852.
OKAY, A.İ. & ŞAHİNTÜRK, Ö. 1997. Geology of the Eastern Pontides. In: ROBINSON, A.G. (ed), Regional and Petroleum Geology of the Black Sea and Surrounding Region. American Associatian of Petroleum Geologists (AAPG) Memoir 68, 291–311.
PAL, P.C., KHURANA, K.K. & UNNIKRISHNA, P. 1979. Two examples of spectral approach to source depth determination in gravity and magnetics.Pure and Applied Geophysics 117, 772–783.
PAMUKCU, O.A., AKÇIĞ, Z., DEMİRBAŞ, Ş. & ZOR, E. 2007. Investigation of crustal thickness in Eastern Anatolia using gravity, magnetic and topographic data. 10.1007/s00024-007-0267-7.
POUDJOMDJOMANI, Y.H., DIAMENTM. & ALBOUYY., 1992. Mechanical behaviour of the lithosphere beneath the Adamawa Uplift (Cameroon, West Africa) based on gravity data. Journal of African Earth Sciences 15, 81–90.
RADHAKRISHNAMURTHY, I.V. 1998. Gravity and Magnetic Interpretation in Exploration Geophysics. Geological Society of India, Bangalore, India.
RAMBABU, H.V. 1997. Average crustal density of the Indian lithosphere: an inference from gravity anomalies and deep seismic soundings. Journal of Geodynamics 23, 1–4.
REAGAN, R.D. & HINZE, W.J. 1976. The effect of finite data length in the spectral of ideal gravity anomalies. Geophysics 41, 44–55.
RIVERO, L., PINTO, V. & CASAS, A. 2002. Moho depth structure of the eastern part of the Pyrenean belt derived from gravity data. Journal of Geodynamics 33, 315–332.
SEBER, D., SANDVOL, E., BRINDISI, C. & BARAZANGI, M. 2001. Crustal model for the Middle East and North Africa region: implications for the isostatic compensation mechanism. Geophysical Journal International 147, 630–638.
SPECTOR, A. & GRANT, F.S. 1970. Statistical models for interpreting aeromagnetic data. Geophysics 35, 293–302.
ŞENGÖRA.M.C. & YILMAZY. 1981. Tethyan evolution of Turkey: a plate tectonic approach. Tectonophysics 75, 181–241.
ŞENGÖR, A.M.C., GÖRÜR, N. & ŞAROĞLU, 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. Society of Economic Palaeontology and Mineralogy, Special Publications 37, 227–264.
ŞENGÖR, A.M.C., ÖZEREN, S., ZOR, E. & GENÇ, T. 2003. East Anatolian high plateau as a mantle-supported, N-S shortened domal structure. Geophysical Research Letters 30, 24.
TRIETEL, S., CLEMENT, W.G. & KAUL, R.K. 1971. The spectral determination of depths to buried magnetic basement rocks. Geophysical Journal of the Royal Astronomical Society 24, 415– 428.
TOKEL, S. 1981. Plaka tektoniğinde magmatik yerleşimler ve jeokimya: Türkiye’den örnekler [Magma emplacement in plate tectonics and geochemistry: examples from Turkey]. Yeryuvarı ve İnsan 6, 53– 65 [in Turkish].
TSOKAS, G.N., HANSEN, R.O. & FYTIKAS, M. 1998. Curie point depth of the island of Crete (Greece). Pure and Applied Geophysics 152, 747– 757.
USTAÖMER, T. & ROBERTSON, A.H.F. 1995. Palaeotethyan tectonic evolution of the north Tethyan margin in the Central Pontides, N Turkey. In: ERLER, A. & ERCAN, T. (eds), Proceedings of the International Symposium on the Geology of the Black Sea Region, 23–42.
WOLLARD, G.P. 1959. Crustal structure from gravity and seismic soundings.Journal of Geophysical Research 64, 1524–1544.
WOLLARD, G.P. & STRANGE, W.E. 1962. Gravity anomalies and crust of the earth in the Pacific basin. In: The Crust of the Pacific Basin. Geophysical Monograph 6, 12.
ZOR, E., SANDVOL, E., GÜRBÜZ, C., TÜRKELLİ, N., SEBER, D. & BARAZANGI, M. 2003. The crustal structure of the East Anatolian plateau (Turkey) from receiver functions. Geophysical Research Letters 30, 8044.