Tethys-Marginal Sedimentary Basins in Western Iran

Tethys-marginal sedimentary basins in western Iran

VICTOR B. CHERVEN* MCO Resources, Inc., 10880 Wilshire Boulevard, Los Angeles, California 90024

ABSTRACT paper is to summarize their geology and suggest a plate-tectonic setting for each. Five sedimentary basins formed along the Iranian margin of the Northeast of the Main Zagros Thrust in the Sanandaj-Sirjan and southern Tethys Ocean during its evolution. These basins record the neighboring ranges of the Rezaiyeh-Esfandagheh block lie two basins that opening and closing of the ocean basin and the collision of what is formed along the Iranian continental margin prior to Late Cretaceous now Arabia and llran. Arabian-Iranian collision (Fig. 1). Younger basins related to oceanic clo- The late Paleozoic-Jurassic Isfahan basin opened by continental sure and continental collision lie adjacent to both sides of the /Zagros rifting that began in the Devonian, and contains an early (late Paleo- Thrust. zoic-Triassic), passive-margin sequence and a later clastic-wedge phase. The Early Cretaceous Sanandaj basin is a forearc overlying the EARLY PALEOZOIC MIOGEOCLINE tectonized and subsided Isfahan basin. The latest Cretaceous-Paleo- cene Kermanshali basin is a remnant of the Tethys Ocean basin. It Lower Paleozoic strata throughout Iran, in much of Arabia and Iraq, initially lay along tectonic strike from the lengthening Arabian-Iranian and in parts of Pakistan, Afghanistan, Turkey, and Jordan have a similar collision orogen ito the southeast but was later incorporated into the stratigraphy, which consists of upper Precambrian to Lower Cambrian orogenic foldbell. The late Cenozoic Zagros basin is a suture (fore- rhyolite and basalt overlain by Lower Cambrian salt, dolomite, aid ar- land) basin that formed on the Arabian plate as it attempted subduc- kosic to quartzitic sandstone, and Middle Cambrian to Silurian carbonate tion beneath Iran. The Paleogene tectonic setting of the Kashan-Gav- and shale (see summary in Berberian and King, 1981). This stratigraphic khuni basin is in doubt, but, by mid-Tertiary time, it was a foreland sequence records the development of a widespread Gondwanian piassive basin that lay landward of the collisional foldbelt and was nearly continental margin following late Precambrian orogenesis (Bender, 1975; surrounded by oiiher orogenic highlands that formed during conver- Stocklin, 1974). A nearly complete Paleozoic stratigraphic sequence in gence of other plates within and marginal to Iran. southeast Turkey (Flugel, 1971; Brinkman, 1971) suggests continuous subsidence there, but middle Paleozoic unconformities and thin red- INTRODUCTION bed-volcanic associations in parts of Iran and elsewhere suggest tectonic instability and are the first indications of incipient basin formation. That a majo;: ocean (southern Tethys) separated Arabia from Iran during the Mesozoic is now firmly established by detailed studies of ophio- ISFAHAN BASIN lite sequences that are exposed in the Zagros Mountains of Iran, the Oman Mountains of the Arabian Peninsula, and the Taurus Mountains of Turkey The lower Paleozoic miogeoclinal sequence is preserved (but locally (Alleman and Peters, 1972; Glennie and others, 1973; Haynes and metamorphosed) beneath Devonian or Permian unconformities in several McQuillan, 1974; Hallam, 1976; Gealey, 1977; Welland and Mitchell, places in the Sanandaj-Siijan Ranges (Thiele and others, 1968; Stocklin, 1977; Coleman, 1981). With few exceptions (Kashfi, 1976), earlier inter- 1968; Reyre and Mohafez, 1972; Berberian, 1977). Upper Devonian, pretations in which the ophiolite-chert sequences were autochthonous Carboniferous, and Permian basalt and diabase interbedded with clastic rocks affected by only minor faulting (Wells, 1969; Wilson, 1969) have and carbonate rocks overlie the unconformities along the Main Zagros now been supplanted by plate-tectonic models that involve late Paleozoic Thrust (Figs. 2A and 3) and record the initial development of the Isfahan or early Mesozoic continental rifting, Mesozoic sea-floor spreading, Late basin. Approximately 1 km of upper Carboniferous shallow-watet dolo- Cretaceous subduction, and Late Cretaceous or Tertiary island-arc/conti- mite and limestone is exposed in the Karkas Range in the eastern part of nent and/or continent/continent collision, ophiolite obduction, major the basin and is unconformably overlain by 700-800 m of Permian to thrust faulting, and continental suturing. The numerous studies of ophiolite Middle Triassic limestone and dolomite interbedded with and overlying formation and ofoiuction have, however, focused principally on regional red and white quartzite (Reyre and Mohafez, 1972). In the Abadeh Range plate reconstructions (Stocklin, 1968, 1974, 1977; Dewey and others, farther south, upper Carboniferous strata consist of 500 m of deep-water 1973; Stonely, 1974; Berberian and King, 1981) with little regard to black limestone and shale that contain reefs and reefal debris. They are diverse sedimentary basins that formed during Mesozoic and Cenozoic unconformably overlain by 2.5 km of platform and reef limestone of plate interactions. Several basins can, nevertheless, be recognized from the Permian age and 1 km of interbedded shale and carbonate and 600 m of limited data available from the Zagros Mountains, and the purpose of this dolomite of Late Permian to Middle Triassic age. Northwest of the Abadeh Range, upper Carboniferous strata are apparently absent, and several hundred metres of quartzose turbidites interbedded with basaltic •Present address: Geology Department, California State University-North- flows and tuffs and Permian limestones pinch out onto a horst block of ridge, Northridge, California 91330; and Mesa Verde Exploration and Production Services, 7026 Comstock Avenue, Whittier, California 90602. Precambrian or lower Paleozoic metamorphic rocks (Fig. 2A). Facies

Geological Society of America Bulletin, v. 97, p. 516-522,4 figs., May 1986.

516

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patterns and thicknesses thus suggest that the late Paleozoic Isfahan basin The Isfahan basin probably originated by rifting of the early Paleo- deepened from a shoreline east of present outcrops to a submarine sill of zoic Arabian passive margin along northerly to northwesterly trends Precambrian basement rocks, which is presently exposed along the Main (Stocklin, 1974; Stonely, 1974; Falcon, 1967; Gealey, 1977). The wide Zagros Thrust. range in age of mafic volcanism (Late Devonian to Early Permian) sug- Upper Triassic through Upper Jurassic strata may unconformably gests that rifting may have been slow or episodic. Devonian-Carboniferous (Berberian and King, 1981) or conformably (Reyre and Mohafez, 1972; carbonates and quartzites are compatible with a rift valley/proto-oceanic Polyanskiy, 1976) overlie older strata in the Isfahan basin, but, without gulf interpretation, and the succeeding Permian carbonate/shale wedge doubt, they record a major change from carbonate to clastic deposition. that grades westward to a turbidite/basalt association is compatible with a Approximately 800 m of fine-grained deltaic sandstone and siltstone with passive-margin miogeocline interpretation. some coal in the central Karkas Range (Polyanskiy, 1976) reportedly The overlying middle Mesozoic clastic sequence most surely records thicken westward toward Isfahan to more than 2.5 km of greenish "some- an important tectonic event involving major uplift to the east of the Isfahan times quartzitic" sandstone (Reyre and Mohafez, 1972). To the north and basin. This event has been variously interpreted as rifting and breakup of west of Isfahan, the Upper Triassic-Lower Jurassic section consists of the "Arabian-Iranian Platform" (Stocklin, 1968), microcontinent/micro- turbidite sandstone and shale (Isfahan Flysch) at least 2.5 km thick. These continent collision of the central Iran and Lut blocks (Fig. 1; Reyre and turbidites are interbedded with pillow lava, tuff, and metamorphic-clast Mohafez, 1972), and growth of a continental-margin magmatic arc as a breccia in westernmost outcrops. Quantitative compositional data for this result of northeastward subduction of Tethyan crust beneath the Rezayeh- widespread clastic sequence are not available, but both volcanic (Berber- Esfandagheh block (Berberian and King, 1981). Because the Mesozoic ian and King, 1981) and quartzose (Gansser, 1955) detritus have been position of central Iran and various other tectonic blocks is uncertain, as is reported. the timing of arc-related metamorphism in the Sanandaj-Siijan Ranges, The Isfahan basin was uplifted and strongly deformed in Late Juras- and because the provenance of the Isfahan Flysch remains speculative sic-Early Cretaceous time, concurrent with granitic plutonism, andesitic without modal compositional data, a tectonic interpretation of the Isfahan volcanism, and low-grade metamorphism in the northern part of the basin for Jurassic time is probably premature. Lithologic similarity to Sanandaj-Siijan Ranges. Gansser (1955), Stocklin (1968), and Reyre and folded and faulted deposits in slightly older basins in central Iran, however Mohafez (1972) noted no earlier significant deformation of the basin, (Reyre and Mohafez, 1972), favors a commonality of setting on the fore- whereas Berberian and King (1981) reinterpreted the age of some of the land side of a collisional orogen in eastern and/or northern Iran. igneous and metamorphic rocks as Middle Triassic, thereby suggesting two deformational phases. SAN AND AJ BASIN

Lower Cretaceous (Albian-Aptian) carbonates with basal conglomerate unconformably overlie older rocks in many areas east of the Main Zagros Thrust, indicating that much of the Rezaiyeh-Esfandagheh block

Figure 1. Spatial and temporal distribution of sedimentary basins in western Iran. IB (D-J) = Devonian to Jurassic Isfahan basin, SB (eK) = Early Cretaceous Sanandaj basin, KB (Pa) = Maestrichtian to Paleocene Kerman- shab basin, KGB (N) = Neogene Kasban-Gavkhuni basin, Z (N) = Neo- gene Zagros basin, MZT = Main Za- gros Thrust.

0 KM 200

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Figure 2. Generalized cross sections through five Tethys marginal sedimentary basins. Although generalized in their spatial position with respect to one another, sections show general westward accretion along Iranian continental margin as sedimentation shifted westward from mid-Paleozoic to Tertiary time. During the Tertiary, major basins formed on both sides of Main Zagros Thrust (MZT), concurrent with major uplift along fault ;sone. Location of cross sections shown in Figure 3. P = Pliocene, Mu-P = upper Miocene to Pliocene, Ml = lower Miocene, O-Ml = Oligocene to lower Miocene, E = Eocene, Pa = Paleocene, Km = Maestrichtian, Ku = Upper Cretaceous, K1 = Lower Cretaceous, Kb = Barremian to Altiian, J = Jurassic, Tr = Triassic, Pu = Upper Permian, DC = Devonian to Carboniferous, C = Carboniferous, PC-PI = Precambrian to lower Paleozoic.

remained emergent for perhaps 35 m.y. following the Late Jurassic-Early Cretaceous to perhaps Upper Triassic radiolarian chert, limestone-basalt- Cretaceous orogenic event that deformed the Isfahan basin. Subsidence serpentinite mélange, and lherzolite-harzburgite ophiolite (Haynes and resumed on the Reiiaiyeh-Esfandagheh block in the Sanandaj area (Fig. 3) McQuillan, 1974; Berberian and King, 1981). during the late Early Cretaceous, where 2-3 km of Barremian-Albian Despite controversy over the timing of the initiation of subduction, turbidites accumulated in a successor basin here termed the Sanandaj basin essentially all workers agree that subduction of southern Tethys beneath (Figs. 1, 2B, and 3; Stocklin, 1968). Modal compositional data are not the Rezaiyeh-Esfandagheh block was in full swing by the Cretaceous. available, but derivation from Upper Jurassic to Cretaceous granite (and Subduction gave rise to the magmatic arc whose plutons are exposed in a its presumed volcanic carapace), which is exposed on the east flank of the few places east and southeast of Sanandaj, and detritus shed from the arc basin, appears likely. The basin is probably floored by folded and slightly accumulated in a forearc basin in the Sanandaj area. The basin was metamorphosed Upper Jurassic Isfahan Flysch, which crops out along the bounded on the south by a persistently high horst block of Precambrian eastern and southern margins (Fig. 3). Cenozoic dextral offset along the and lower Paleozoic rocks (Fig. 2A), which formed during the late Pa- Main Zagros Thrust has brought the basin into tectonic contact with leozoic rifting of the Rezaiyeh-Esfandagheh block from Arabia.

Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/5/516/3419449/i0016-7606-97-5-516.pdf by guest on 01 October 2021 Figure 3. Generalized geologic map of western Iran. Cross sections are shown in Figure 2 (modified from Stocklin and Nabavi, 1973, and Gansser, 1955).

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KERMANSHAH BASIN that the overlying deep-water Santonian marl (Gurpi Formation, James and Wynd, 1965) and Coniacian turbidites (Muti Formation, Glennie and Stratigraphic evidence in the Zagros and Oman Mountains indicates others, 1973) represent renewed subsidence as the Arabian platform was that the Tethys Ocean closed diachronously as collision between Arabia drawn down into the subduction zone to the northeast. The turbidites also and the Rezaiyeh-Esfandagheh block began in the Coniacian and pro- show evidence of having been derived from a northeastern source, which gressed northwestward from Oman to Turkey (Fig. 4A). In the southeast- Gealey (1977) interpreted as an uplifted subduction complex. ern Zagros and Oman, a major Cenomanian-Turonian disconformity is The inferred subduction complex is represented by deep-sea radiolar- recorded by rubbly, karstic topography and hematite nodules that cap Al- ian chert and ophiolite that form extensive thrust sheets overlying the bian to Cenomanian platform carbonates (Fig. 4B). Gealey (1977) suggested Santonian and older platform strata in the Neyriz area of the southeastern that this period of emergence and weathering occurred as the Arabian Zagros (Fig. 3) as well as in Oman. In both areas, Maestrichtian reef platform passed over the outer swell of the Iranian subduction zone and limestone depositionally overlies the thrust sheets, implying that the sub-

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Figure 4. Diagram illustrating diachronous collision between Arabia and Oman-Iran-Turkey and origin of Kermanshah basin. Tectonic setting at Cretaceous-Paleocene boundary shown in A; broad arrows are hypothetical convergence vectors, thin arrow is inferred transport direction for Amiran Flysch, and cities shown are Kermanshah (K), Isfahan (I), and Neyriz (N). Stratigraphy along collision zone shown in B; arrows indicate structural position of ophiolite thrust sheets and timing of ophiolite obduction. Incorporation of synorogenic flysch into a suture belt during closure of a remnant ocean basin diagrammatically shown in C (from Graham and others, 1975). Data for southeast Turkey from Hall (1976) and T emple and Perry (1962); other data from references cited in text.

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duction complex, uplifted by incipient collision in the Coniacian, was The foregoing evidence points to diachronous collision, obduction, obducted wholesale onto the Arabian margin in the Campanian to early and suturing of Arabia to the Rezaiyeh-Esfandagheh block. Collision Maestrichtian as suturing progressed (Fig. 4B; James and Wynd, 1965; began in Oman in the Coniacian, progressed to the southeastern Zagros in Glennie and others, 1973; Stocklin, 1974; Haynes and McQuillan, 1974; the Santonian or Campanian, reached the Kermanshah area in the Paleo- Welland and Mitchell, 1977; Gealey, 1977). The causes and mechanism of cene, and affected eastern Turkey in the late Paleocene. Such regional the obduction process are still somewhat controversial, although most diachroneity is to be expected in most continental collisions. workers favor some type of crustal collision, such as between the passive Arabian margin and the active Rezaiyeh-Esfandagheh margin. KASHAN-GAVKHUNI BASIN In contrast to the southeastern Zagros and Oman, stratigraphie relations northwest of Neyriz indicate that a remnant of the Tethys Ocean Cretaceous limestones and older (Isfahan basin) rocks that were de- basin lay to the northwest in the Kermanshah area (Fig. 4A). The formed in the collision with Arabia are unconformably overlain by a Cenomanian-Turonian disconformity of the southeastern Zagros dies out successor basin assemblage of middle to upper Tertiary strata here termed to the northwest, and the complete Upper Cretaceous Series is present, the "Kashan-Gavkhuni basin sequence." Tertiary rocks thicken eastward consisting entirely of deep-water chert, shale, and marl (Fig. 4B; James from a feather edge on the east flank of the Sanandaj-Sirjan Ranges to and Wynd, 1965). Deep-water marl of both Maestrichtian age (Gurpi several kilometres in the Kashan basin east of the Karkas Range (Fig. 2D). Formation) and Paleocene age (Pabdeh Formation) interfingers eastward Conglomeratic red beds form the base of the sequence and are over- toward the Main Zagros Thrust with the Amiran Flysch, a submarine fan lain by >4 km of andesitic to basaltic lava and tuff interbedded with complex that consists of 2 km of mostly chert and ophiolite debris (Figs. middle to upper Eocene limestone that is somewhat tuffaceous (Gansser, 4B and 2C; Falcon, 1958; James and Wynd, 1965). East of Kermanshah, 1955; Reyre and Mohafez, 1972). Lower Oligocene red beds succeeded by the flysch becomes slightly older, coarser, and thicker, which suggests evaporites overlie the volcanic section and are disconformably overlain by eastern derivation, and, between arcuate bends in the Main Zagros and transgressive upper Oligocene to Miocene limestone, sandy marl, evapo- High Zagros Thrusts, mapping by Stocklin and Nabavi (1973) suggests rites, and sandstone. Thickness patterns and paleontologie data suggest that that it lies on a chert-ophiolite sequence that is similar to that in the the basin had restricted outlets at the southeast end of the Rezaiyeh- southeastern Zagros (Fig. 3). The facies relations suggest that the Amiran Esfandagheh block and along part of its eastern side (Gansser, 1955; Flysch was deposited in a remnant ocean basin (terminology of Dickinson, Furrer and Soder, 1956). The marine middle Tertiary grades upward to a 1974a) floored by Tethyan chert and ophiolite and lying along tectonic regressive sequence of evaporites and sandy marls, followed by thick, strike form from the collision orogen to the southeast, where the uplifted upward-coarsening Pliocene lacustrine and alluvial-fan red beds that re- subduction complex was undergoing erosion (Figs. 4A and 4C). cord basin filling. The Amiran Flysch interfingers with and is overlain by limestone of The tectonic affinities of the Eocene volcanics remain puzzling, al- the Taleh Zang Formation, which contains an abundant shallow-water though their largely andesitic with subordinate basaltic and rhyolitic char- fauna and has been interpreted as a reef complex (James and Wynd, acter favors an arc setting. Crawford (1972), Dewey and others, (1973), 1965). The Taleh Zang interfingers westward with deeper water marl of and Farhoudi (1978) interpreted it as arc magmatism that was caused by the Pabdeh Formation and eastward with nonmarine, upward-coarsening, continued subduction of the Arabian plate along the Zagros subduction cherty red sandstone and conglomerate of the Kashkan Formation (Fig. zone. Berberian and King (1981) argued that such intense and widespread 2C). Northeast of Kermanshah, the Kashkan becomes thicker and coarser volcanism after collision is unlikely. Alternatively, they suggested that the and unconformably overlies the Amiran (James and Wynd, 1965). The volcanism may be related to strike-slip faulting, but this idea is unsup- change from deep-water clastic flysch deposition to shallow-water carbon- ported by compelling evidence. Perhaps the volcanism is related to west- ate and nonmarine red-bed deposition probably records some combination ward subduction of oceanic crust that was marginal to the central Iran of basin filling and basin uplift as suturing progressed northwestward along block beneath the northeast (as opposed to the southwest) margin of the the collision zone. The carbonate-red-bed sequence is thus regarded here Rezaiyeh-Esfandagheh block. The tectonic contact between the volcanics as a molasse facies, a typical end product of the evolution of remnant on the Rezaiyeh-Esfandagheh block and Cretaceous to Eocene mélange on ocean basins as they become incorporated into the orogenic belt (Dickin- the central Iran block (Fig. 3) may favor this hypothesis. As pointed out by son, 1974a; Graham and others, 1975). Stocklin (1977), the volcanic belt can be traced southeastward across the The Kermanshah basin or similar basins extended northwest to the central Iran block and the Makran Coast, where it surely represents a major bend in the continental margin near the Iran-Iraq-Turkey border volcanic arc related to subduction in the Gulf of Oman. and then across southeastern Turkey, where the stratigraphy is somewhat Neogene sedimentary strata of the Kashan-Gavkhuni basin record similar (Fig. 4B). Important differences in the Turkish sequence include uplift of the central Iran block following suturing of the various Iranian (1) Campanian emplacement of olistostromes onto Arabian continental- blocks that surround the basin. Sediment was shed westward from central slope marl by gravity sliding from the subduction complex (Fig. 4A), (2) Iran, southward from the Alborz Mountains of northern Iran, and eastward more thorough incorporation of the Maestrichtian-Paleocene flysch se- from the Zagros. The basin is thus best viewed as a foreland basin. quence into the subduction complex by underthrusting, and (3) somewhat later (late Paleocene-early Eocene) emplacement of major nappe sheets ZAGROS BASIN that are analogous to the Zagros and Oman ophiolites (Fig. 4B; Hall, 1976). Hempton (1985) has recently reported Paleogene metamorphism, The Oligocene to middle Miocene Asmari Limestone disconforma- volcanism, and complex deformation along southeastern Turkey's Bitlis bly overlies Paleocene to Eocene deep-water marl (Pabdeh Formation) on suture zone and inferred that island-arc and mélange terranes are impor- the southwest side of the Zagros Thrust and records middle Tertiary onset tant elements of the collision zone in that area. of subsidence in the incipient Zagros basin (Figs. 2E and 3). This transgres-

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sive event was previously noted in the discussion of the stratigraphy of the the manuscript. I thank MCO Resources for support during manuscript Rezaiyeh-Esfandagheh block in the Kashan-Gavkhuni basin. In both ba- preparation. sins, the Oligocene-Miocene transgression was followed by Pliocene-

Pleistocene regression and deposition of an evaporite-clastic sequence. The REFERENCES CITED

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Bender, F., 1975, Geology of the Arabian Peninsula: Jordan: U.S. Geological Survey Professional Paper 560-1, 36 p. thicker than are: sections penetrated by wells nearer the Gulf (Fig. 2E), Berberian, M., 1977, Three phases of metamorphism in Hajiabad quadrangle (southeastern extremity of the Sanandaj- Siijan structural zone): A paleotectonic discussion, in Berberian, M., ed., Contribution to the seismotectonics of which implies that the eastern part of the basin has been cannibalized as Iran (Part HI): Geological Survey of Iran, no. 40, p. 239-260. the foldbelt migrated westward into the axial part of the basin (James and Berberian, M., and King, G.C.P., 1981, Towards a paleogeography and tectonic evolution of Iran: Canadian Journal of Earth Sciences, v. 18, p. 210-265. Wynd, 1965). Brinkman, R., 1971, The geology of western Anatolia, in Campbell, A., ed., The geology and history of Turkey, Proceedings, Petroleum Exploration Society of Libya Annual Field Conference, 13th: p. 171-189. 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(1974), and Gealey (1977) related the foldbelt and crush zone to the Red Gansser, A., 1955, New aspects of the geology in Central Iran: World Petroleum Congress, 4th, Rome, Proceedings, Sec. Sea spreading. I/A/5, p. 280-300. Gealey, W., 1977, Ophiolite obduction and geologic evolution of the Oman Mountains and adjacent area.:: Geological Dickinson (1974a) termed this type of basin, formed on the downgo- Society of America Bulletin, v. 88, p. 1183-1191. Glennie, K., Bouf, M., Hughes-Clark, M., Moody-Stuart, M., and Reinhardt, R., 1973, Late Cretaceous napjes in Oman ing continent in a continent-continent collision, a "peripheral" foreland and their geologic evolution: American Association of Petroleum Geologists Bulletin, v. 57, p. 5-27. basin in order to differentiate it from foreland basins on the overriding Graham, S., Dickinson, W., and Ingersoll, R., 1975, Himalayan-Bengal model for flysch dispersal in Appalachian- Ouachita system: Geological Society of America Bulletin, v. 86, p. 273-286. continent or from foreland basins behind magmatic arcs. I prefer the term Hall, R., 1976, Ophiolite emplacement and the evolution of the Taurus suture zone, southeastern Türke): Geological Society of America Bulletin, v. 87, p. 1078-1088. "suture" basin, emphasizing the genesis of the basin along the suture belt Hallam, A., 1976, Geology and plate tectonics interpretation of the sediments of the Mesozoic radiolaite-ophiolite and the causality of the suturing process. Many of the Tertiary basins along complex in the Neyriz region, southern Iran: Geological Society of America Bulletin, v. 87, p. 47-52 Haynes, S., and McQuillan, H., 1974, Evolution of the Zagros Suture Zone, southern Iran: Geological Sodetv of America the Alpine-Himalayan chain are of this type. Bulletin, v. 85, p. 739-744. Hempton, M., 1985, Structure and deformation history of the Bitlis suture near Lake Hazar, southeastern Turkey: Geological Society of America Bulletin, v. 96, p. 233-243. James, G., and Wynd, J., 1965, Stratigraphic nomenclature of the Iranian oil consortium agreement arei: American CONCLUSIONS Association of Petroleum Geologists Bulletin, v. 49, p. 2182-2245. Kashfi, M. S., 1976, Plate tectonics and structural evolution of the Zagros geosyndine, southwestern Iran: Geological Society of America Bulletin, v. 87, p. 1486-1490. The diverse stratigraphic sequences in western Iran represent a col- Polyanskiy, B. V., 1976, Principal cycles of formation of Triassic-Jurassic basins and the maxima of coal accumulation in central Iran: International Geology Review, v. 19, p. 1031-1040. lage of sedimentary basins that formed sequentially, beginning in the De- Reyre, D., and Mohafez, S., 1972, A first contribution of the NIOC-ERAP agreements to the knowledg: of Iranian vonian, in response to evolving plate interactions along the Iranian margin geology: Paris, Editions Technip., 58 p. Stocklin, J., 1968, Structural history and tectonics of Iran: A reveiw: American Association of Petroleum Geologists of the southern Tethys Ocean. Five major basins that developed on con- Bulletin, v. 52, p. 1229-1258. 1974, Possible ancient continental margins in Iran, in Burk, C., and Drake, C., eds.. The geology ol continental tinental, paracontinental, or paraoceanic crust are distinguishable at pres- margins: New York-Heidelberg-Berlin, Springer-Verlag, p. 889-903. ent on stratigraphic grounds, in addition to the ocean basin itself, which is 1977, Structural correlation of the Alpine ranges between Iran and Central Asia: Societe Geologiqu: de France, Memoire 8, Horse-Serie no. 8, p. 333-353. represented by ophiolitic oceanic crust caught up in thrust slices along the Stocklin, J., and Nabavi, M., 1973, Tectonic map of Iran: Geological Survey of Iran, scale 1:2,500,000. Stoneley, R., 1974, Evolution of the continental margins bounding a former southern Tethys, in Burk, G, and Drake, C, Main Zagros thrust fault. Lithologic sequences, sediment transport pat- eds., The geology of continental margins: New York-Heidelberg-Berlin, Springer-Verlag, p. 889-903. terns, and paleoenvironmental interpretations facilitate interpretations of Temple, P. B., and Perry, L. J., 1962, Geology and oil occurrence, southeast Turkey: American Association of Petroleum Geologists Bulletin, v. 46, p. 1596-1612. the tectonic setting of the other five basins and combine with structural and Thiele, O., Alavi, M., Assefi, R., Hushmandzadeh, A., Seyed-Ememi, K., and Zahedi, M., 1968, Explanatory text of the Gotpaygan quadrangle map, 1:250,000: Tehran, Geological Survey of Iran, E7, 24 p. tectonic relationships to clarify the Phanerozoic tectonic history of this part Weiland, M., and Mitchell, A., 1977, Emplacement of the Oman ophiolite: A mechanism related to subduction and of Iran. collision: Geological Society of America Bulletin, v. 88, p. 1081-1088. Wells, A., 1969, The crush zone of the Iranian Zagros Mountains, and its implications: Geological Magazine, v. 106, p. 385-394. Wilson, H., 1969, Late Cretaceous eugeosyndinal sedimentation, gravity tectonics, and ophiolite emplacement in Oman ACKNOWLEDGMENTS Mountains, southeast Arabia: American Association of Petroleum Geologists Bulletin, v. 53, p. 626-671.

S. A. Graham, W. K. Gealey, M. Hempton, D. W. Powers, and S. Schamel reviewed the manuscript. W. K. Gealey and W. R. Dickinson MANUSCRIPT RECEIVED BY THE SOCIETY MAY 17, 1985 REVISED MANUSCRIPT RECEIVED NOVEMBER 25,1985 contributed valuable discussions and Dickinson reviewed an early draft of MANUSCRIPT ACCEPTED DECEMBER 3,1985

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