Structure and deformation history of the Bitlis suture near Lake Hazar, southeastern

MARK R. HEMPTON* Department of Geological Sciences, State University of New York at Albany, Albany, New York 12222

ABSTRACT north. During middle to late Eocene, conver- followed by a later phase of gence caused thrust stacking of the Elazig, in the Miocene. French geologists do not accept Detailed mapping of the Bitlis suture zone Maden, and Puturge Complexes; second- the concept of a Bitlis suture (Ricou and others, near Lake Hazar shows that it is composed of generation deformation in the Puturge Com- 1974, 1979; Delaune-Mayere and others, 1977; three tectonostratigraphic units which crop plex; and first-generation deformation in the Ricou and Marcoux, 1979). They propose that out as distinct north-dipping thrust slices. Maden Mélange. Continued convergence thrust sheets composing the zone emanated as From south to north, these are the Puturge with the Arabian plate in the late Miocene large from near the Pontide Mountains, Metamorphic Complex, the Maden Mélange, caused kink banding in the Puturge and several hundred kilometres to the north. Dewey and the Elazig Igneous Complex. The Pu- Maden Complexes. Since the late Miocene, and Sengor (1979), Sengor (1979), and Sengor turge Metamorphic Complex consists of pre- this convergence has been accommodated by and Yilmaz (1981) refined the model of Dewey Tertiary, continental-margin sediments shortening and thickening along numerous and others (1973) by relating the of the metamorphosed to the greenschist facies dur- internal faults. Bitlis suture zone to the regional geology of the ing the Campanian-Maastrichtian and de- entire eastern Mediterranean area and offering formed by four generations of structures. INTRODUCTION more detailed paleogeographic interpretations. These are, in sequence (1) isoclinal folds and All the models proposed to explain the struc- a transposition , (2) open folds, cren- The Bitlis suture zone is a belt of high strain tural and tectonic evolution of the Bitlis su- ulation , and north-dipping thrust and rapid uplift that marks the convergent ture zone suffer from a limited data base, over- faults, (3) kink bands, and (4) small-displace- boundary between the Arabian platform to the simplifications, and unclear paleogeographic ment faults. The Maden Mélange represents south and a collage of continental fragments, implications. The biggest problem for construct- middle Eocene, back-arc-basin sediments island arcs, and ophiolitic mélange to the north ing well-constrained tectonic models is the lack and volcanics metamorphosed to the green- (Dewey and others, 1973; Sengor and Yilmaz, of reliable data from this rugged and inhospita- schist facies and deformed by three genera- 1981). The zone strikes east across southeastern ble terrain. Clearly, there is a need for large-scale tions of structures: (1) a north-dipping Turkey, forming the Tauride Mountains, which mapping to clarify key lithological and struc- cleavage, (2) kink bands, and (3) small- merge into the Zagros Mountains in Iran tural details with which to test and constrain displacement faults. The Elazig Igneous (Fig. 1). Based on regional mapping, Ketin tectonic scenarios. I conducted a detailed map- Complex comprises an imbricated Maastrich- (1959, 1966) delineated major lithologic units ping project (scale 1:10,000) across 450 km2 of tian-early Eocene island arc and young within the Taurides. He recognized that thrust- the suture near Lake Hazar (Hempton, 1982a). marginal-basin terrain. Thrust faults between ing was south-directed and had progressed from This area was chosen because major units of the units are north-dipping, listric, and form a north to south. Ketin proposed that the strongest suture and their interrelationships are well ex- thin-skinned system. "orogenic movement" occurred in the Late Cre- posed (Fig. 1). The purpose of this paper is to These features suggest the following de- taceous but was followed by a "paroxysmal report the results of this mapping and to exam- formational and tectonic history. The Puturge movement" in the Oligocene. Reconnaissance ine their implications for the deformation history Metamorphic Complex was generated by mapping and borehole studies by Rigo de Righi and tectonic development of this part of the Bit- isoclinal folding and of sedi- and Cortesini (1964) delineated an Upper Cre- lis suture zone. ments composing the Arabian continental taceous ophiolitic assemblage within the pre- margin during Campanian-Maastrichtian Tertiary Arabian platform. They constructed a TECTONOSTRATIGRAPHIC to the south. The Elazig detailed cross section of the Taurides, showing FRAMEWORK arc developed on the deformed margin be- numerous north-dipping thrust sheets, and pro- cause of subsequent southward of posed two deformation events—an "Alpine di- In the Lake Hazar region, the Bitlis suture oceanic lithosphere. The arc migrated to the astrophism" and a late Miocene phase of gravity zone consists of the following tectonostrati- north, opening a back-arc basin. By the early gliding. Dewey and others (1973) synthesized graphic units, outcropping as distinct north- Eocene, the back-arc basin was filling with the available data within a plate-tectonic dipping thrust slices north of the frontal thrust volcaniclastics of the Maden Mélange, and framework and proposed that the Bitlis suture and transected by the East Anatolian . the Elazig arc collided with a to the zone began to form in the late Miocene as the From south to north these are (1) the Puturge between the continental Complex, (2) the Maden Mélange, and (3) the plates of Arabia and Eurasia. Based on limited Elazig Complex (Figs. 1, 2, 3). These units are •Present address: Bellaire Research Center, Shell mapping, Hall (1976) proposed that "initial su- Development Company, P.O. Box 481, Houston, major components of the suture zone over most Texas 77001. turing" began in the Late Cretaceous and was of its length. Subordinate tectonostratigraphic

Geological Society of America Bulletin, v. 96, p. 233-243, 7 figs., 1 table, February 1985.

233

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39 00

Figure 1. Sketch map of Bitlis suture near Lake Hazar, illustrating distribution and structural relationships of major tectonostratigraphic units. Horizontally ruled areas represent Upper Cretaceous to Paleocene sediments, including the Simaki Formation. Black areas represent tectonic slivers of Guleman serpentinite. Rectangle near Lake Hazar shows area of Figure 2. Index map shows frontal thrust of Bitlis suture (barbed) and area of Figure 1.

units include the Guleman serpentinite and the base, and amphibolites that have undergone sists of a multiply deformed, low-grade meta- Simaki Formation. In the following sections, metamorphism in the greenschist and almandine- morphic terrain, at least 2,730 m thick, which each of these units is considered in detail. Each amphibolite fades (Altinli and others, 1963; contains 80% metapelite, 15% metaquaitzite, section briefly summarizes reported data and Perincek, 1979). Sengor and others (1979) and 5% recrystallized limestone (Fig. 2). then describes and interprets salient lithological showed that it is multiply deformed. Rigo de The metapelite unit forms the lower 1,780 m and structural data generated by this study. Righi and Cortesini (1964) noted that a recrystal- of the exposed complex and includes phyllite, lized limestone contains Permian-Carboniferous; slate, quartz-muscovite schist, calcschist, and Puturge Metamorphic Complex fossils. They suggested that the Puturge Meta- very low-grade, thinly interbedded metapielite morphic Complex was the product of regional (Fig. 4). Replicate whole-rock, K-Ar age The Puturge Metamorphic Complex crops metamorphism during "Alpine diastrophism." dates obtained from an unweathered, coarse- out in the southern third of the map area, south Because the complex is unconformably overlain grained mica schist yield an average of of the East Anatolian fault. Previous studies of by the middle Eocene Maden Complex, it must 71.2 ± 3.6 Ma. The mica schist contains 2.5% this unit in other localities reported that it con- be pre-middle Eocene (Hempton, 1982a). potassium, and 90% of all argon is radiogenic tained mica schist, clayey schist, quartz-bearing Mapping of the Puturge Metamorphic Com- 40AR. This indicates a Campanian-Maastiich- schist, quartzite, calcschist, marble, meta-dia- plex within the study area shows that it con- tian minimum age of recrystallization and cool-

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ing. The recrystallized limestone unit outcrops oping metapelite. (2) In many exposures, west-oriented, irregular shapes, which indicate above the metapelite unit as irregular and elon- first-generation structures are overprinted by a that they formed from isoclinal recumbent folds. gate discontinuous bodies surrounded by meta- second generation of structural elements includ- These folds have been subsequently deformed

pelite (Figs. 2 and 3). These bodies strike ing folds (F2), a foliation (S2), and a on by more open folds, whose vertical axial sur- northwest, dip northeast, and are up to 650 m S|. Second-generation folds generally lack a faces strike at 90° to the original axial surfaces

thick. They are especially numerous in the east- well-defined foliation (S2). Some F2 folds, how- (Fig. 2). Because F2 folds would correspond to ern half of the mapped complex. The meta- ever, possess a weak to strongly developed S2 the later open folds and because F2 axes trend quartzite unit crops out as large, irregular, cleavage parallel to their axial sur- northwest, the isoclinal F, axes must have northwest-striking bodies and thrust slices up to faces. (3) A third generation of structural originally trended northeast. The predominant

300 m thick at the top of the complex, on the elements is represented by kink bands that are northwest plunge of the F2 axis, defined by the eastern margin of the mapped terrain (Figs. 2 especially prominent in muscovite-rich layers projection of S^ and the fold interference pat- and 4). and overprint earlier features. (4) Numerous in- terns suggest that the isoclinal F, folds may have The basal metapelite unit is interpreted as tersecting, small-displacement (1-20 cm) faults dipped slightly toward the northwest. Northeast- having originally been a continental slope/rise cut all previous structural elements and consti- dipping thrust faults imbricate the northeast sequence because of its thinly interbedded char- tute fourth-generation structural features. margin of the metamorphic complex and strike acter, its low frequency and thinness of meta- The of poles to S[ northwest, which suggests that they might be psammite beds, and its interbedded carbonate foliation defines a broad girdle that suggests S] related to F2 folding. conglomerates (Blatt and others, 1980). The was folded about a northwest axis that plunged In summary, the Puturge Metamorphic Com- metapsammite and recrystallized limestone in- to the northwest (Figs. 5a, 5b). This corresponds plex represents an original continental-margin, terbeds are turbidity-current deposits derived to the orientation of hinge lines of second- sedimentary sequence that has been metamor- from the continental shelf. This slope/rise se- generation folds (Fig. 5c). Hinge lines of third- phosed to the greenschist facies and subjected to quence exhibits features which are similar to the generation kink bands are randomly oriented four phases of deformation. The first deforma- western Atlantic slope/rise environment (Hollis- (Fig. 5d). Irregular map patterns of metaquartz- tion phase was the most intense. It generated ter and Heezen, 1972; Damuth and Komar, ite, recrystallized limestone, and metapelite in northeast-trending, isoclinal recumbent folds on 1977) and to the lower Paleozoic slope/rise sed- the eastern part of the metamorphic terrain are the macroscale and a transposition foliation (Si) iments of the northern Appalachians (Keith and similar to macroscopic-fold interference patterns and rare fold closures (F[) on the mesoscale. Friedman, 1977). The stratigraphically higher produced experimentally by Reynolds and This deformation probably caused the green- recrystallized limestone and metaquartzite units Holmes (1954) and theoretically by Ramsay schist facies metamorphism. A second deforma- are interpreted as continental-shelf deposits be- (1967). The fold interference structures in the tion phase was less intense but formed open to cause of the lithologic similarity to modern Puturge Metamorphic Complex include north- tight, slightly south-verging folds which reori- continental-shelf environments (Milliman and others, 1972; Selley, 1978). The characteristic mineral assemblage of quartz + muscovite (phengite) ± chlorite within the Puturge Meta- Figure 2 explanation (map appears on two following pages). morphic Complex indicates that it experienced greenschist-facies metamorphism (Miyashiro, I [ • j Qai Quaternary alluvium —•— Uthological boundary 1973; Winkler, 1979). I Ev Maden Complex .vv\v.vw Fault zone boundary Structural features within the Puturge Meta- Middle Eocene morphic Complex show at least four genera- Oblique-slip fault tions of structural elements. (1) The most I I | I Ks Simaki Formation pervasive structural element is a weak to Maast.- Paleocene -*•—*- strongly developed foliation that is prominent in Elazig Complex - Maast.-Middle Eocene the metapelite unit but not in the less-ductile —Bedding metaquartzite' and recrystallized limestone. This I* „* I Ka Andesite unit L—' Cleavage in Ev foliation is parallel to bedding, which in most I v I Kb Basalt unit exposures is discontinuous and marked by First generation pinched beds or separate, elongate lenticles with I ' .'I Kd Diabase unit foliation in Pm pinched ends. Rare isoclinal fold closures, the I + I Kg Gabbro unit Second-generation axial surfaces of which are parallel to the foliation in Pm stretched bedding and foliation, are present. iffgfr plagiogranite / diorite These fabric elements are characteristic of trans- First-generation fold axis posed bedding (Hobbs and others, 1976). The Puturge Complex - Camp-Maast. transposition foliation is labelled S|. Many bod- Second-generation fold axis [ I Pm Metapelite unit ies of the recrystallized limestone unit appear as Kink band axis isolated, tight to isoclinal macroscopic fold (Fj) 1 ; I ;| Pr Recrystallized limestone unit closures enveloped by the metapelite unit. They Pq Metaquartzite Diabase are interpreted as representing transposition and boudinage on a much larger scale. These struc- Siliceous dike tures indicate that similar folds are in the envel- Guleman Gp serpentinite

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^

X 60 Pm 80

36, 24 V 27 5\

Figure 2. Map of Bitlis suture zone wear Lake Hazar, based on 5V detailed mapping by Hempton Pm (1982). 2 KM 80 Pm

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Figure 3. Croiis sections of study area (note position on Fig. 2). Pm = Puturge metapelite unit, Pq = Puturge metaquartzite unit, Pr = Puturge recrystallized limestone unit, Ev = Maden Mélange, Kg = Elazig gabbro unit, Kd = Elazig diabase unit, Kb = Elazig basalt unit, Ka = Elazig andesite unit. Horizontal scale equals vertical scale.

PUTURGE COMPLEX Zo I11Z N N Q4 < -<

METAQUARTZITE

RECRYSTALLIZED

'poles to S-\

METAPELITE

/*2 hinge kink band hinge lines Figure 4. Representative north-south lines cross-sectional column through the Puturge Complex and Maden Mélange, representing Figure 5. Stereograms for Puturge Complex structural data. a. Poles to Si, n = 240. Great

the thickness, distribution, contact relations, circle represents middle of girdle, b. Contours of poles to St. Contour intervals are 5%, 3%, 2%, and metamorphic grade of component units. 1%, and c. Hinge lines for F2 folds, n = 27. d. Hinge lines to kink bands, n = 55.

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ented S[ and in places formed an S2 crenulation gest that the facies of the Maden Mélange shaped packets of relatively undeformed, more cleavage. It also imbricated the northeast edge of formed within or near an island arc. The pre- brittle beds that are assumed to have been origi- the metamorphic complex along northeast- dominance of basalt, basaltic andesite, and an- nally laterally continuous. On the macroscopic dipping thrusts. A third deformation phase was desite suggests that the island arc was generated scale, the volcaniclastic facies is the most volum- even less intense and generated randomly ori- within an oceanic setting (Miyashiro, 1974). inous and deformed. It envelops blocks of other ented kink bands. Small-displacement faults Metamorphic minerals in the mélange include more brittle fades and serves as a more ductile mark a later phase of brittle deformation. actinolite, chlorite, epidote, calcite, and musco- matrix which has accommodated most of the vite. This assemblage is characteristic of the strain. On the mesoscopic scale, the volcaniclas- Maden Mélange greenschist facies (Miyashiro, 1973; Winkler, tic and pelagic limestone facies are the most The Maden Mélange is exposed as large 1979). strained. The volcaniclastic facies exhibits cleav- thrust slices in the eastern half of the map area, The Maden Mélange is highly deformed but age parallel to bedding, segmented and stretched as small thrust slices within the Elazig Complex, heterogeneously strained. It contains three gen- interbeds, anastomosing zones, and rare or as on the Puturge Complex (Fig. 2). erations of structural elements. The dominant intrafolial folds. More intense strain caused pha- Previous studies of the Maden Complex, outside structural motif of the mélange at the macro- coid elongation and denser spacing of shear the study area, reported that it is composed of scopic, mesoscopic, and microscopic scales is the zones. Cleavage morphology ranges from slaty volcaniclastic sandstone, siltstone, interdigitating isolation of phacoids, boudins, or blocks within in tuffaceous mudstones and pelagic limestone volcanics, red marl, and red conglomerate, and a fine-grained, highly deformed, more ductile to phacoidal in volcaniclastics. Bedding within that it is variably deformed (Altinli and others, matrix. On all scales, shear has been accommo- the Maden Mélange dips to the north or north- 1963; Sungurlu, 1974; Erdogan, 1977; Ozkaya, dated in thin, subparallel, anastomosing zones east, parallel to the boundary thrust faults 1978; Perincek, 1979). Perincek (1979) and Per- comprising a network around phacoidally (Fig. 6a). Cleavage also dips to the northeast incek and Ozkaya (1981) showed that (1) it contains middle Eocene fossils, and (2) it uncon- formably overlies the Puturge Metamorphic MADEN COMPLEX Complex in places. The Maden rocks have been interpreted as being an immature island arc (Er- dogan, 1977) and more recently as a marginal basin (Sengor and others, 1980; Sengor and Yilmaz, 1981; Aktas and Robertson, 1983). Mapping of the Maden Mélange within the study area shows that it consists of a variably deformed, colored mélange metamorphosed to the greenschist facies. The maximum observed structural thickness is 500 m (Fig. 4). Seven lithologic facies compose the colored mélange. In order of decreasing abundance they are (1) undifferentiated volcaniclastics; (2) high- ly vesicular basalt, basaltic andesite, and ande- site pillows and flows; (3) pelagic limestone, (4) red mudstone; (5) massive limestone; (6) calcirudite; and (7) basal conglomerate. Despite tectonic disruption, facies 3-6 crop out as blocks at regular structural levels within the mélange and indicate an original stratigraphy with "ho- rizons" of (in ascending order) pelagic lime- stone, red mudstone, massive limestone, and calcirudite. The voluminous volcaniclastic facies appears at all horizons within the complex and serves as mélange matrix. The volcaniclastic and volcanic facies suggest that the depositional en- vironment of the Maden rocks was adjacent to a volcanic terrain. Volcanic activity was the pri- mary control on facies composition. Volcanic eruptions provided flows and volcaniclastics that composed all or part of many facies. During periods of volcanic quiescence, volcanogenic deposits were reworked, and carbonate or muddy sediments accumulated. Facies similar to Figure 6. Stereograms for Maden Complex structural data. a. Poles to bedding, n = 45. b. those of the Maden Mélange have been reported Poles to cleavage, n = 106. c. Filled circles = hinge lines of folds, n = 9. Filled triangles = poles from a Miocene island-arc terrain in New Heb- to axial planes of folds, n = 5. d. Filled circles = hinge lines of kink bands, n = 9. Filled triangles rides (Mitchell, 1970). These similarities sug- = poles to axial planes of kink bands, n = 7.

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but exhibits a greater concentration of poles Based on regional mapping and limited geo- contains basaltic pillows and flows, minor dia- (Fig. 6b). Rare mesoscopic folds within the chemical analyses, Yazgan (1981) suggested that base dikes, rhyolitic and andesitic pyroclastic in- Maden Mélange are open to tight, with the complex was generated as a continental- terbeds, andesitic dikes and flows, and s :ocks of or cylindrical profiles. Their orientation suggests margin arc. gabbro and diorite. A thrust slice of Maden that they are related to first-generation structures Within the map area, the Elazig Complex Complex is exposed between the basalt unit and (Fig. 6c). These features indicate that the Maden is 1,210 m thick and consists of four units (from the overlying andesite unit. The andesiti; unit is Complex was subjected to transposition at all bottom to top): gabbro, diabase, basalt, and an- characterized by a northwest-striking thrust scales and experienced a large amount of shear desite (Figs. 2 and 7). The gabbro unit measures slice, at least 235 m thick, composed of andesitic strain. This strain was probably generated dur- at least 200 m thick and is 95% isotropic gabbro, flows, volcaniclastics, and dikes with minor ing displacement on the boundary thrust faults of variable texture, with minor layered gabbro, basaltic-andesitic flows and dacitic dikes. All and was synchronous with the greenschist-facies mafic intrusions, and stocks of diorite and quartz contacts between the units strike northwest and metamorphism. A second generation of struc- diorite. Mafic intrusions include thin, diabase dip from 25°-0° to the northeast. All are thrust tural elements is represented by rare kink bands dikes (average 15 cm) of random orientation faults except the gabbro/diabase contact. The (Fig. 6d). Pervasive, randomly oriented small- (with no chill margins), irregular metagabbro metamorphic character of the complex ranges displacement faults mark a third generation of bodies up to hundreds of metres in diameter— from prehnite-pumpellyite in the andesite unit to structural elements. representing small magma chambers—and gab- lower-amphibolite facies in the gabbro unit bro pegmatites. The upper contact of the gabbro (Fig. 7). At any level in these units, the distri- Elazig Igneous Complex unit with the diabase unit is marked by a 50-m bution of metamorphic minerals is patchy and transition from gabbro with few diabase dikes; to probably reflects the effects of hydrothermal cir- The largest exposure of the Elazig Complex 70% diabase dikes with screens of gabbro. The culation in the original environment. All igneous occupies the northern half of the map area, diabase unit is 400 m thick and consists of a and volcaniclastic beds within the Elazig Com- north of the East Anatolian fault. Smaller expo- heterogeneous mixture of diabase dikes, screens plex dip toward the northeast at angles up to sures occur just south of the East Anatolian fault of metagabbro and microgabbro, massive dia- 25°, parallel to its internal and external thrust (Figs. 1 and 2). On the basis of field work out- base, and quartz-diorite intrusions as large as 1 faults. Each unit is cut by many small- side of the map area, this unit was reported to km in diameter. Diabase dikes are nonsheeted, displacement faults of random orientation. contain Maastrichtian limestone, shale, sand- randomly oriented, thin (20-50 cm), and pos- An idealized sequence of the Elazig Complex stone, granite, and granodiorite (Altinli and oth- sess chill margins on both sides or no chill mar- is represented in Figure 7. The gabbro, diabase, ers, 1963; Perincek, 1979). Hempton and Savci gins at all. Quartz-diorite dikes also are ran- and basalt sequence is interpreted as an ophiolite (1982) and Savci (1983) showed that near domly oriented. A thrust fault striking northwest sequence generated in a young back-arc -basin Elazig (Fig. 1), this complex is predominantly and delineated by a 10-m-thick breccia zone se- environment because of (1) its aggregate thin- igneous, and so i;hey proposed that it formed parates the diabase unit from the overlying ba- ness of 975 m, (2) the character of the diabase near a Maastrichtian intra-oceanic island arc. salt unit. The basalt unit is 375 m thick and dikes, (3) rhyolitic and andesitic-pyroclastic

Metamorphic Facies

PREHNITE PUMPELLYITE IrEj Andesitic volcaniclastics

~!1 Andesitic (lows PREHNITE PUMPELLYITE \/f\ Andesitic ard dacitic dikes Figure 7. Schematic reconstructed to B section from the Elazig Complex, illus- Pillow basclt trating composition, contact relations, LOWER GREENSCHIST and metamorphic grade of component || || Basaltic flow units. A = andesite, B = basalt. D = |V Basaltic volcaniclastics diabase, G = gabbro. Heavy linis be- tween units A, B, and D represent | v | Rhyolitic pyroclastics thrust faults.

| | Massive diabase GREENSCHIST

| J | Diabase dike

UPPER GREENSCHIST Microgabbro to I.V.'I Gabbro LOWER AMPHIBOLITE

Diorite, granodiorite

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beds within and overlying the basalt unit, are interpreted as representing interarc-basin Lithologic Implications (4) andesite dikes within the basalt unit, and deposits coeval with the Elazig Complex. (5) many large diorite and quartz-diorite intru- In their regional synthesis, Sengor and Yilmaz sions. Back-arc-basin crust and lithosphere is STRUCTURAL RELATIONS (1981) proposed that (1) the Puturge Complex thinner than mid-ocean-ridge crust and litho- BETWEEN THE PUTURGE, ELAZIG, had originally been part of the Arabian platform sphere, especially in the beginning stages of AND MADEN COMPLEXES (Gondwanaland), but that since it rifted away back-arc-basin opening (Sclater and others, in the Triassic, it had behaved as a microconti- 1976; Lawver and Hawkins, 1978). In the dia- All contacts between the Puturge, Maden, nent; and (2) deformation and metamorphism base unit, the random orientation, nonsheeted and Elazig rocks are thrust faults (Figs. 1 and 3). occurred in the Late Cretaceous when character, thinness, and lack of one-way chill The original unconformity between the Puturge were obducted over the Puturge microcontinent margins of the diabase dikes suggest that their Complex and Maden Mélange has been nearly from the north. In this study, the interpretation intrusion was not related to a mid-ocean-ridge obliterated by thrust faults which strike east or of the Puturge Metamorphic Complex as having spreading environment. Rather, it was most southeast and dip toward the north or north- originally been a continental-margin sequence likely related to a setting involving point-source east at 20°-30°. The Puturge/Maden thrust is supports the model of Sengor and Yilmaz spreading and discontinuous ridge segments marked by a single thrust surface in the central (1981). These sediments could have once over a broad area, as is interpreted to be com- region of the study area but is characterized by formed part of the northern continental margin mon in young, active back-arc basins (Karig and several subparallel thrust faults and interleaving of Gondwanaland. There is no stratigraphic or others, 1978; Lawver and Hawkins, 1978). The thrust slivers in the eastern half of the map. structural proof, however, that the Puturge calc-alkalic intrusions and pyroclastics within These thrust slivers are parallel to those compris- Complex rifted away to form a microcontinent and overlying the ophiolite, including the ande- ing the imbricated northeastern edge of the Pu- during the Triassic. A simpler explanation is that site unit, indicate the close presence of a volcanic turge Metamorphic Complex. A small klippe of it remained part of the northern edge of Arabia. island arc. The predominance of andesite and Maden Mélange rocks overlying Puturge Com- The 71.2 ± 3.6 Ma K-Ar date obtained from the basaltic andesite and absence of continental plex rocks (in the southwest corner of the map) Puturge Complex by this study indicates the basement implies that the arc was intra-oceanic, suggests that displacement along this thrust was minimum age of recrystallization and cooling set perhaps similar to the modern Marianas arc at least 5 km. The thrust between the Maden after the demise of thrusting. The Puturge Com- (Miyashiro, 1974). Complex and the Elazig Complex is nearly hor- plex could have formed as a deformed and izontal or slightly dipping toward the north or metamorphosed sliver off the leading edge of the Subordinate Units northeast. All units of the Elazig Complex are in Arabian continental margin during the Campa- thrust contact with the underlying Maden Mé- nian-Maastrichtian, south-directed ophiolite ob- Subordinate tectonostratigraphic units have lange. Both the andesite and the basalt units duction event. This process is happening now in limited exposure within the study area. The overlie the Maden Complex near the northern Taiwan, where the Luzon arc is converging onto Guleman serpentinite is exposed as small thrust edge of the study area. In the central map area, a the South China Sea platform (Bowin and oth- slivers or "horses," to use the terminology of large klippe of the diabase unit overlies the ers, 1978; Ernst, 1983). Maden Mélange. In most other areas, basal gab- Boyer and Elliot (1982), along thrust faults The interpretation of the Elazig Complex as bro overlies Maden Mélange. A thrust sliver (or within the northeastern edge of the Puturge being a marginal-basin and island-arc assem- ) of Maden Mélange crops out within the Complex. The largest horse is 2 km by 250 m. blage is new. Hempton and Savci (1982) and basalt unit. That must mark an internal thrust The Guleman serpentinite is of uncertain age, Sengor and Yilmaz (1981) had previously inter- fault of at least several kilometres of displace- although Erdogan (1977) assumed that it is Ju- preted the Elazig Complex as an island-arc ter- ment. There is enough vertical relief to show rassic to Cretaceous in age and is related to rain with no associated marginal basin. The that some of the thrust faults have more gentle Campanian-Maastrichtian ophiolite obduction Maastrichtian age reported by Perincek (1979) dips at depth. The geometry of the thrust faults onto the Arabian platform. Much larger serpen- implies that island-arc volcanism started during and their associated lineations indi- tinite outcrops are found east of the study area. or shortly after ophiolite obduction to the south. cate that deformation was thin-skinned and that In places outside the map area, the Guleman Sengor and Yilmaz (1981) suggested that island- thrusting was south-directed. The similarity of serpentinite forms the foundation of the Elazig arc volcanism continued into the middle Paleo- orientation of the thrust contacts suggests that all Complex. The Simaki Formation is exposed as a cene and that subduction was south-directed. 2 of the thrusts developed during the same episode large (~ 1 km ) , completely bounded That polarity of subduction is supported by the of thrusting, after the middle Eocene, based on by subsidiary faults of the East Anatolian fault location of the marginal-basin and island-arc the age of the Maden Mélange. zone, along the south shore of Lake Hazar. It rocks. Because the Elazig Complex overlies consists of 600 m of thinly bedded, medium- to Guleman serpentinite in places, the initial phases fine-grained sediments that are interpreted as DISCUSSION AND CONCLUSIONS of island-arc volcanism probably started on the being distal turbidite deposits that had an island- deformed edge of the Arabian continental mar- arc source. Based on fossil content, it has been Having reported and interpreted the salient gin that had just been overthrust by ophiolite. A dated as Maastrichtian to Paleocene (S. Ercu- field data generated by this study, it is appro- modern tectonic analog may be found in Tai- ment, 1983, personal commun.). Larger out- priate to consider its greater implications for the wan, where westward subduction of Philippine crops of Simaki Formation rocks occur east of geologic development of the Bitlis suture and Sea oceanic lithosphere beneath Taiwan is be- the study area, where they unconformably over- how it might constrain existing models or lead to ginning to occur in the reactivated Philippine lie the Elazig Complex. Simaki Formation rocks the development of new ones. Trench. This is taking place because conver-

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gence between the Philippine Sea plate and the southwest-directed folding. In addition, there latest-middle Eocene to late Eocene. This pro- Asian plate can no longer be accommodated by was a later deformation phase that produced posal states that the northern margin of :he Bitlis the collision of the Luzon Arc with the Asian kink bands and an even later brittle phase that suture zone has been assembled since the late continental margin (Ernst, 1982). yielded small-displacement faults. The Maden Eocene. The proposal also implies that the first The interpretation of the Maden Complex as Mélange has been thrust over and structurally phase of penetrative strain in the Puturge Com- being arc or near-arc basin deposits supports the interleaved with the Puturge Complex along plex occurred before the Eocene. It most likely marginal-basin model of Sengor and others, thrusts parallel to the structural grain in the Pu- happened during the Campanian-Maastrichtian 1980; Sengor and Yilmaz, 1981; and Aktas and turge Complex. This structural grain was im- ophiolite obduction event over the Arabian plat- Robertson, 1983. Maden rocks overlie the Si- parted by the second phase of penetrative strain. form. The kink bands in the Puturge anil Maden maki Formation flysch, which in turn overlies The Maden Mélange was deformed by one Complexes may reflect terminal collision in the the Elazig Complex (Perincek, 1979). Maden phase of penetrative strain, manifested as cleav- late Miocene, when the full thickness of the rocks unconforrnably overlie the Puturge Com- age, which strikes and dips parallel to the thrust Arabian lithosphère converged with the thrust plex, Guleman serpentinite, and the Elazig faults and to the structural grain within the Pu- stacks to the north. The small-displacement frac- Complex just to the east of the study area. The turge Complex. Later phases of deformation are tures probably are related to slight internal Maden rocks cover a larger area of southeastern represented by kink bands and by small- movements associated with continued conver- Turkey and are interpreted as representing the displacement faults. The Elazig Complex struc- gence across the suture zone since the late sedimentary infill of a larger marginal basin than turally overlies the Maden Mélange along a Miocene. is represented by the gabbro, diabase, and basalt thrust whose strike parallels that of the other forming the marginal-basin basement of the major structural features. These relationships Tectonic Synthesis Elazig Complex. The question arises as to what suggest that the second phase of penetrative The preceding discussion of the data and the arc the Maden Mélange volcaniclastics and vol- strain in the Puturge Complex is correlated with interpretations generated by this stud} suggest canics are associated with. Sengor and others the only phase of penetrative strain in the the following sequence of tectonic even s. (1980) and Sengor and Yilmaz (1981) stated Maden Complex. Because the Maden rocks Campanian-Maastrichtian. Ophiolites were that Elazig Complex island-arc volcanism lasted range up to middle Eocene in age, this phase of obducted to the south over the continental mar- until the middle Paleocene. The Maden Mé- penetrative strain must be post-middle Eocene. gin of Arabia, deforming the northern edge of lange, however, contains middle Eocene basaltic It is probably associated with the thrust stacking the margin into isoclinal folds and rretamor- and andesitic flows that clearly are not re- of the Puturge, Maden, and Elazig Complexes. phosing it to the greenschist facies to form the worked. Hence, the Maden volcanics and vol- A thrust contact on the northern border of the Puturge Metamorphic Complex. During and/or caniclastics are interpreted as representing part Elazig Complex separates it from the Keban after obduction, subduction of oceanic litho- of the island arc associated with the Elazig metamorphic terrain to the north, and it is sealed sphère southward under the deformed margin Complex that was active until the Eocene. by sediments bracketed in age between late Pa- gave rise to the Elazig Complex island arc and leocene and early Eocene. This relation suggests incipient marginal basin. that thrusting along the northern border of the Structural Implications Medial to Late Eocene. The Elazig Complex Elazig Complex had ceased by the early Eocene, island arc and marginal basin evolved until the at the latest. If we accept the concept of Ketin Structural data from the Puturge, Maden, and middle Eocene. The marginal basin grew larger (1959, 1966) that thrusting progressed south- Elazig Complexes are summarized in Table 1. and filled with volcaniclastics and volcanics of ward and note that no sediments younger than The Puturge Complex has undergone at least the Maden Complex. By the early Eocene, the middle Eocene are in the Maden Mélange, then two phases of penetrative strain. The second arc collided with the Keban metamorphic ter- it seems reasonable to propose that the thrust phase was related to a northeast-southwest- rain to the north. Continued convergence was stacking in the study area occurred during the maximum-compressive which caused accommodated by thrusting to the south. By the middle to late Eocene, this convergence caused southward thrust stacking of the Elazig, Maden, and Puturge Complexes. This marks the obliter- TABl.E I. SUMMARY OF STRUCTURES AND DEFORMATION HISTORY OF BITLIS SUTURE ZONE ation of oceanic lithosphère (the Elazig Com- plex marginal-basin crust) and initial suturing Date Structure Deformation and proposed tectonic event between the converging Arabian and Eurasian Puurge Maden Etazig Complex Complex Complex plates. The thrust stacking metamorphosed and cleaved the Maden Complex to produce a Campanian- S,.F, Isoclinal folding (NE axes) of Arabian continental margin under greenschist facies, colored mélange. It formed Maastrichtian south-directed ophiolite obduction northwest-trending F2 folds in the Puturge

Middle to late s2,f2, Cleavage, Thrust stacking of Elazig, Maden, and Puturge Complexes caused by Complex that refolded the earlier F[ folds. The Eocene thrust faults thrust faults thrust faults initial suturing between Arabia and Eurasia Elazig Complex, as the structurally higher unit, was imbricated. Horses of greenschist facies Late Miocene Kink bands Kink bands Full thickness of Arabian lithosphere reached convergence zone to result in terminal suturing Maden Mélange from below were carried into lower-grade Elazig Complex along thrust faults. Pliocene-Recent Small- Small- Small- Continued convergence across suture zone accommodated by many ditpl&cemeni displacement displacement internal faults Late Miocene. By the late Miocene, con- faults faults faults tinued convergence across the suture zone de-

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