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Oil and Gas Occurrences in Southwest TurkeyA. Bozcu a; A. Poisson ba Department of Geological Engineering, Çanakkale Onsekiz Mart University,Çanakkale, Turkeyb University of Paris-Sud, Orsay, France

Online Publication Date: 01 January 2008To cite this Article: Bozcu, A. and Poisson, A. (2008) 'Oil and Gas Occurrences inSouthwest Turkey', Energy Sources, Part A: Recovery, Utilization, andEnvironmental Effects, 30:10, 954 - 962To link to this article: DOI: 10.1080/10826070601082716URL: http://dx.doi.org/10.1080/10826070601082716

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Energy Sources, Part A, 30:954–962, 2008Copyright © Taylor & Francis Group, LLCISSN: 1556-7036 print/1556-7230 onlineDOI: 10.1080/10826070601082716

Oil and Gas Occurrences in Southwest Turkey

A. BOZCU1 and A. POISSON2

1Department of Geological Engineering, Çanakkale Onsekiz Mart University,Çanakkale, Turkey

2University of Paris-Sud, Orsay, France

Abstract In SW Turkey, on both sides of the Antalya basin, two continental micro-plates can be distinguished: the Anatolian micro-plate to the NE and Bey Daglarımicro-plate to the W. These micro-plates are composed of a Paleozoic basement ofGondwana type, surrounded by Mesozoic carbonate platforms. From south to norththe Bey Dagları platforms are made of shallow marine carbonates from Triassic timeup to Cenomanian. The southern part of this carbonate platform remained undershallow marine conditions up to the Eocene. On the contrary, the northern partsubsided during Late Cretaceous time. In the Bey Dagları platform, occurrences oforganic materials are known in the Triassic and in the Early Cretaceous-Cenomaniancarbonates. Rock-eval analysis indicate 0.25 to 1.46% total organic carbon (TOC).These facies could have represented a source rock for oil and gas. In the same areathe uncomformable Early Miocene carbonates are made of bioclastic calcarenites.In some areas these calcarenites are dark colored and contain oil. These carbonatesrepresent a reservoir rock The Anatolian micro- plate is also composed of shallowmarine carbonates from Triassic time up to Eocene. Organic materials are knownin the Akkuyu formation, Late Jurassic in age. According to organic geochemicalcharacteristics, this unit is a good source rock. The total organic carbon (TOC)content of this unit is up to 12%. In the same area, other occurrences of oil and gasare known in two locations, Çirali to the SW of Antalya Bay and the Kizildag to theNE of Antalya. The Çirali location is known since the ancient civilizations as Chimera.Gas of this area is pouring out from a complex tectonic imbricate structure includingultrabasic rocks. The source rock and the reservoir are poorly known. The Kizildagis a large klippen of peridotites in the Antalya nappes complex. Liquid petroleumseepage is observed in this ophiolitic unit.

Keywords Anatolian micro-plate, Bey Dagları micro-plate, oil, SW Turkey

1. Introduction

The study area is located in the western part of the Taurus Belt (SW Turkey), on both sidesof the Antalya gulf known as “the Isparta Angle.” This region exhibits a complex structureinvolving two autochthonous units surrounded and imbricated with three allochthonouscomplexes. The result is a complex pile of thrust sheets. The autochthonous units are partsof the Bey Dagları micro-plate to the west and of the Anatolian micro-plate to the NE(Anamas-Akseki platforms). These micro-plate rifted away from the Gondwana duringthe Triassic, and they were separated during the Mesozoic by the Pamphylian basin,

Address correspondence to Ayse Bozcu, Engineering and Architecture Faculty, Department ofGeological Engineering, Çanakkale Onsekiz Mart University, Terzioglu Campus, 17100 Çanakkale,Turkey. E-mail: abozcu@comu.edu.tr

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Oil and Gas Occurrences in Southwest Turkey 955

a branch of the southern Neotethys. The present situation results from a successionof compressional tectonic events which occurred from the Late Cretaceous up to thePliocene The first compressional event occurred at the end of the Cretaceous and duringthe Paleocene, when the micro-plates came into collision by closure of the Pamphylianbasin. During this period, the Antalya nappes were expelled from this ocean and theywere thrust onto the adjacent autochthons. A second compressional event occurred in theIsparta Angle at the end of the Miocene and during the Pliocene. At that time (Aksuphase; translation from east to west), the Antalya Nappes were imbricated with theplatforms. This event gave way to the Antalya Complex, a pile of slices which sandwichedthe platforms and the basinal sequences. The two other systems of nappes were thrustindependently: the Hoyran-Beysehir-Hadim nappes from the NE onto the Anamas-Aksekiplatforms (during Late Eocene times) and the Lycian nappes from the N-NW onto the BeyDagları (during mid Miocene time). As a result the area is tectonically rather complicated(Figure 1).

Source rocks of gas and oil are known in both autochthon and allochthon units inrather different environments: carbonate platforms and deep ocean basin.

2. Regional Geology and Petroleum Geology

2.1. The Autochthon Micro-plates

These micro-plates are composed of a Paleozoic basement of Gondwana type surroundedby Mesozoic carbonate platforms (Figures 2 and 3).

The Bey Dagları platforms are folded in a huge anticline striking N-S to the west ofthe Antalya gulf. From south to north the Bey Dagları platforms (Figure 2) are made ofshallow marine carbonate from Triassic times up to the Cenomanian. The southern partof these platforms remained under shallow marine conditions up to the Eocene. Theycame to emergence during Late Eocene-Oligocene times, and then they were flowedby the Early Miocene marine transgression. On the contrary, the northern part of theBey Dagları platforms subsided during Late Cretaceous times, mainly at the end of theCenomanian. During the Mesozoic these platforms subsided slowly. Nevertheless, theyremained under very shallow marine to restricted marine conditions. In such environmentsorganic materials were frequently preserved all along this period. The best common faciesare dark-colored laminated pelmicrites, pelsparites. In one section a preliminary rock-evalanalysis indicates 0.25 to 1.46 total organic carbon (TOC) with an hydrogen index (HI)of 8.0. Due to the thickness of the sequence (100 to 200 m), these facies could haverepresented a source rock for oil and gas. In other parts of the Bey Dagları platforms,the source rock potential of the Mesozoic carbonates have been investigated (Demirelet al., 2001). Surface and core samples were obtained from the Beydagi and Kuyubasiformations. The Demre-1 well samples from Beydagi formation have higher TOC andS2 values than the samples from Kas-1 and Kuyubasi-1 wells. The organic matter inthe samples from Kas-1 and Kuyubasi-1 wells are mostly gas-prone Type III kerogen.Although surface samples are rich in organic matter (7.22 to 9.54%), they have lowTmax values (lower than 430ıC), indicating immature source rock. In the same area theuncomformable Early Miocene carbonates are made of bioclastic calcarenites. In someareas these calcarenites are dark colored and contain oil. In this case, rock-eval parametersare as follows: S1 D 0.59, S2 D 0.65, IP D 0.48, and HI D 282. These carbonatesrepresent a reservoir rock. According to Altunsoy (1999), organic geochemical resultsof this formation are as follows: S1: 0.01–2.79 mg HC/g TOC; S2: 0.02–9.24 mg HC/g

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Figure 1. The structurel map of SW Turkey (Poisson et al., 1984) and petroleum seepage locations:1—Continental Neogene deposits; 2—Marine Neogene (Oligocene and Miocene) deposits; 3—Bey Dagları massif, Lower and Middle Miocene; 4—Bey Dagları platform, neritic formations ofwestern carbonate platform (Upper Triassic up to Senonian, locally remaining up to Maestrihtian);5—Eastern carbonate platform (Kırdag, Anamas-Akseki); 6—Barladag ve Zindan massifs; 7—Metamorphic series in internal (Menderes, Sultandag), or External (Alanya) position; 8—Lyciannappes (emplaced during Middle Miocene), Beysehir Hoyran nappes (emplaced during LateMiocene); 9—Antalya nappes, transitional series of the Western platform margin; 10—Antalyanappes, undifferentiated series; 11—Slicings and rejuvenetion of former thrusts during the Aksuphase; 12—Thrust fault.

TOC; HI: 407–1,000 mg HC/g TOC; %: 0.12, 0.13, 0.19, 0.27, 1.89; kerogene type: I–II;Tmax: 419ıC–459ıC; Ro %: 0.17, 0.18, 0.22, 0.28, 0.43, 0.44. When these results areconsidered, the unit is thought to be a source rock for oil at some levels.

The Anamas-Akseki platforms represent the SW margin of the Anatolian micro-platelocated to the NE of the Isparta Angle. These platforms are also composed of shallowmarine carbonates and clastic sediments from Triassic time up to Eocene (Figure 4). Inthese units, organic materials are known in the Akkuyu formation (Late Jurassic). Thisformation consists of dark-grey bituminous shale and bedded and laminated limestones.According to organic geochemical characteristics, this unit is a good source rock. Thetotal organic carbon (TOC) content of this unit, especially in black bituminous shale

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Oil and Gas Occurrences in Southwest Turkey 957

Figure 2. Generalized stratigraphic columnar section of Bey Dagları micro-plate (modified fromPoisson et al., 1984; Senel, 1984).

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958 A. Bozcu and A. Poisson

Figure 3. Stratigraphic columnar section in the Seydisehir region of Anatolian microplate whichwas observed as Paleozoic basement (Brunn et al., 1971). According to Özgül (1976), this sectionis named the Geyik Dagi unit.

levels, is up to 12%. The degree of maturation of organic carbon, according to Tmax

and Ro values, is low maturity (Tmax: 424ıC–438ıC; Ro: 0.27–0.52), kerogene type: I–II(Badgley, 1993, unpublished report). The degree of maturation of the same unit increasesin some areas (Tmax: 475ıC–545ıC; Ro: 1.23–1.32%) (Baudin et al., 1994).

The Allochthons in the Central Part of the Isparta Angle

(Antalya Nappes Units)

The occurrences in ophiolitic units—in this tectonic context, occurrences of oil, asphaltite,and gas are known in two locations, Çiralı to the SW of Antalya Bay and the Kızıldagto the NE of Antalya. The Çiralı location is known since the ancient civilizations asChimera. Gas of this area is pouring out from a complex tectonic imbricate structureincluding ultrabasic rock. The gas analysis results taken from the gas pouring out in

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Oil and Gas Occurrences in Southwest Turkey 959

Figure 4. Stratigraphic columnar section of Anatolian micro-plate in the Akkuyu region (modifiedfrom Gutnic et al., 1979; Demirtaslı, 1979).

Çiralı are as follows: O2: 9.94%, N2: 32.64%, CO2: 0.05%, C1: 57.57%, C2: 0.16%, C3:0.05%, iC4: 0.03%, NC4: 0.04%, iC5: 0.03%, NC5: 0.03%, g13c CH4: �11.64%. Thesource rock and the reservoir are poorly known.

The Kızıldag (S Egirdir) is a large klippen of peridotites in the Antalya nappescomplex (Figure 5). Oil and asphaltite seepages are observed in this ophiolitic unitoutcropping around Yagderesi (Figures 6a and 6b). Organic geochemical results andcarbon isotope values of oil seepage of the Kızıldag indicate that the oil originated froma marine organic matter. The source rock of this seepage could be Jurassic-Cretaceousaged carbonate sequences with high thermal maturity (Illeez et al., 1992). In the samearea, Triassic aged detritic rocks (Kasimlar shale or Kasimlar formation) represent another

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Figure 5. Generalized stratigraphic columnar section in the Karacahisar region. (Source: Bozcu,1996.)

possible source rock. TOC values of the Kasimlar formation are up to 2.15%. The degreeof maturation of organic matter is over-mature (Ro D 2.90–3.66%). Kerogene type istype III (Bozcu, 1996). The unresolved question is the origin of oil seepage: Kasimlarformation or Jurassic-Cretaceous carbonates?

The occurrences of black shales in deep basinal sedimentary units (Doyran nearAntalya and Akdogan near Isparta)—according to Yurtsever et al. (2003), the Doyransection in the Alakırçay Nappe of the Antalya Nappes includes the organic carbon-richblack shales within radiolarian rich pelagic sediments that were deposited in an off-margin abyssal environment. The total organic carbon contents of the black shales in thishorizon vary from 7.89 to 42.19 wt%, with an average value of 22.0 wt%. The calculatedvalues of the hydrogen and oxygen indexes indicate that the organic carbon originatedfrom marine organic matter (Type I–II kerogen).

The sequence in the Akdogan area is fragmented in several tectonic slices whichresults from the duplication of an initial sequence of basinal sedimentary deposits. From

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Oil and Gas Occurrences in Southwest Turkey 961

Figure 6. Oil seepage (5a) and asphaltite seepage (5b) in ophiolitic unit outcropping aroundYagderesi (S Egirdir).

base to top, this sequence includes: Halobia limestones, sandstones and marls, pink-colored micritic limestones, oolithic and fine-grained calcilutites, red radiolarites includ-ing several small beds of black shales rich in organic matter. TOC values of this blackshales varies from 0.8 to 32%. These facies show high HI-values (623 to 668 mg hydro-carbons/g TOC) suggesting a Type II organic matter. This type of organic matter is usuallyrelated to marine reducing environments and derived mainly from algae and/or bacteria.

3. Conclusions and Suggestions

The Isparta Angle is one of the most tectonically complicated areas of Turkey. Sedimen-tologic and regional tectonic problems of this region have not been solved until now. The

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962 A. Bozcu and A. Poisson

Western Taurus Region has a special importance in the geology of Turkey due to V-shapeturning mechanism of the Isparta Angle, which consists of autocthonous rock units havingdifferent stratigraphic sequences and allocthon assemblages. Petroleum seepages such asasphaltite, oil, and gas are observed in different locations within these units. As a result,we offer that the region needs further investigations, as listed below:

1. Exploration of the platforms (essentially for the Bey Dagları).2. Geographic extension of the layers which shows high organic matter.3. Determination of the organic matter (what is the origin?).4. Paleogeographic reconstruction (what kind of depositional environment and mod-

eling).5. Exploration of the organic matter of the deep basin layers in the Antalya Nappes

(Isparta Cay Unit, Alakir Cay Unit).6. Characterization of the organic matter, tectonic setting of the Antalya Nappes,

and paleogeographic reconstitution of these units before tectonics.

References

Altunsoy, M. 1999. Organic geochemical characteristics of the Miocene Yazır limestones in theSouthern Isparta. Geol. Bull. of Turkey 42:51–62.

Badgley, P. C. 1993. Final report on the geology and petroleum potential of Akseki, Isparta andEgridir licenses (Turkey) of Garnet Resources Corporation.

Baudin, F., Monod, O., Begouen, V., Laggoun-Defarge, F., and Person, A. 1994. Caracterisation etdiagenèse de la matiere organique du Jurassique supérieur du Taurusoccidental (Turquie mérid-ionale). Reconstitution paléoenvironnementale, conséquences tectoniques. Bull. Soc. Géol.

France 165:135–145.Bozcu, A. 1996. Examination of the Mesozoic marine sediments in Kasımlar (Sütçüler-Isparta)

area by the geology, petrography and organic geochemistry. Ph.D thesis, Süleyman DemirelUniversity Science Institute, Isparta, p. 135.

Brunn, J. H., Dumont, J. F., Graciansky, P. Ch. De, Gutnic, M., Juteau, Th, Marcoux, J., Monod,O., and Poisson, A. 1977. Outline of the Geology of the Western Taurids: Geology and History

of Turkey, Tripoli: Petroleum Exploration Society of Libya, pp. 225–255.Demirel, I. H., Günay, Y., and Yurtsever, T. S. 2001. Evaluation of petroleum source rocks on the

coastal area of the Western Taurus region, Turkey. Energy Sources 23:541–552.Demirtaslı, E. 1979. Petroleum potential of the Akseki area in the western Taurus Belt. Bulletin

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(Turquie). Mem. Soc. Geol. France 137:112.Illeez, I. H., Harput, A., and Gül, M. A. 1992. Organic geochemistry of Üç Yıldız petroleum

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