Tectonics versus eustatic control on supersequences of the Zagros Mountains of Iran

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Tectonophysics 451 (2008) 56 – 70 www.elsevier.com/locate/tecto

Tectonics versus eustatic control on supersequences of the Zagros Mountains of Iran Ezat Heydari Department of Physics, Atmospheric Sciences, and Geoscience, Jackson State University, P.O. Box 17660, Jackson, MS 39217, United States Received 15 October 2007; accepted 6 November 2007 Available online 8 December 2007

Abstract At least 12 km of strata ranging in age from the latest Precambrian to the Recent are exposed in the Zagros Mountains of Iran. This sedimentary cover is characterized by distinct stratal packages separated by major unconformities forming twelve supersequences. They are informally named as: (1) Late Precambrian – Cambrian Hakhamanesh Supersequence, (2) Ordovician Kourosh Supersequence, (3) Silurian Camboojiyeh Supersequence, (4) Devonian Darioush Supersequence, (5) Mississippian – Pennsylvanian Khashayar Supersequence, (6) Permian – Triassic Ashk Supersequence, (7) Jurassic Farhad Supersequence, (8) Early Cretaceous Mehrdad Supersequence, (9) Late Cretaceous Ardavan Supersequence, (10) Paleocene – Oligocene Sassan Supersequence, (11) Oligocene – Miocene Ardeshir Supersequence, and (12) Miocene – Pleistocene Shapour Supersequence. These supersequences and their correlatives in neighboring areas have been used to infer tectonic events. The dominant interpretation has been that local or regional epeirogenic movements were responsible for the formation of these supersequences. Unconformities are considered as indications that epeirogenic movements associated with tectonic events affected the area. The present investigation provides an alternative to the established view of the Phanerozoic supersequences of the Zagros Mountains. A good correlation exists between the lithofacies of supersequences in the Zagros Mountains and the second-order eustatic sea-level changes. Deposition of deep-water, marine shales occurred during periods of eustatic sea-level rise. Platform-wide unconformities coincided with eustatic sea-level lows. In fact, supersequences of the Zagros Mountains are nearly identical to those described from the North American Craton and the Russian Platform suggesting that these stratal packages are global. These observations suggest that supersequences of the Zagros Mountains formed by second order eustatic sea-level changes and not by local or regional epeirogenic movements. Although tectonic events did not produce supersequences of the Zagros Mountains, they influenced regional lithofacies patterns through the formation of intrashelf depressions such as the Hormoz Salt Basin during the Precambrian and the Dezful Embayment and the Lorestan Basin during the Mesozoic. Tectonic events also affected sedimentation during the Tertiary collision of Arabia and the Central Iran microplate through uplift, erosion, and the formation of the Zagros Foreland Basin. The results of this investigation necessitate a re-evaluation of the role and the significance of pre-Tertiary tectonic events commonly used to interpret the geological evolution of the Zagros Mountains. © 2008 Elsevier B.V. All rights reserved. Keywords: Zargos Mountains; Central Iran; Supersequence; Sea level change

1. Introduction The Zagros Mountains of Iran are located in the northeastern margin of the Arabian Plate (Fig. 1). This plate is bounded to the northeast by the Zagros Main Thrust Fault (ZMTF), to the northwest by the Dead Sea Fault Zone (DSFZ), to the southwest by the Red Sea rift margin, and in the southeast by the Indian Ocean passive margin (Fig. 1). The Zagros Mountains and adjacent areas are best known for their vast hydrocarbon reservoirs and very young tectonic activities. As a result, E-mail address: [email protected]. 0040-1951/$ - see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.tecto.2007.11.046

detailed investigations have historically concentrated on oil and gas-related topics and structural features of this region (Lees, 1933; Falcon, 1958; Dunnington, 1967; Stöcklin, 1968; Alavi, 1994; Bordenave and Burwood, 1989; Blanc et al., 2003; McQuarrie, 2004; Agard et al., 2005; Bordenave and Hegre, 2005; Hessami et al., 2006). Another remarkable aspect of the Zagros Mountains is the presence of an extensive sedimentary record encompassing strata ranging in age from the latest Precambrian to the Recent (James and Wynd, 1965; Berberian and King, 1981; Motiee, 1993). This sedimentary record consists of distinct stratal packages separated by major unconformities (James

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Fig. 1. Map shows major tectonic features of the Zagros Mountains and adjacent areas. The Zagros Fold and Thrust Belt (ZFTB) is divided into two structural provinces. The High Zagros Zone (HZZ) region is bounded by the Zagros Marin Thrust Fault (ZMTF) to the northeast and the High Zagros Fault (HZF) to the southwest. The HZZ is characterized by intense structural deformation and faulting. Southward is the Simply Folded Zone (SFZ) which is bounded by the HZF to the northeast and the Zagros Frontal Fault (ZFF) to the southwest. The Dezful Embayment (DE) and the Lorestan Basin (LB) are two intrashelf basins that occur in the SFZ area. These two basins are bounded by Kazerun (KF) and Bala Rud (BF) faults. The southern part of the SFB is the Arabian homocline (AH) which is characterized gently dipping strata (data and information from Bahroudi and Koyi, 2004; Sepehr and Cosgrove, 2004; Sherkati and Letouzey, 2004; Sherkati et al., 2006).

and Wynd, 1965; Berberian and King, 1981; Motiee, 1993). These supersequences and their correlatives in adjacent regions have been known for more than four decades and interpreted by epeirogenic movements (Berberian and King, 1981; Beydoun, 1991; Grabowski and Norton, 1994; Motiee, 1993; Alavi, 1994; Sharland et al., 2001). In these interpretations, unconformities are used as indications that epeirogenic movements associated with tectonic events influenced the area.

However, a close examination indicates that supersequences of the Zagros Mountains are similar to those presented by Sloss (1963, 1972) from the North American Craton and the Russian Platform, suggesting that these unconformity-bounded stratal packages are global. In addition, there is a near perfect correlation between the formation of unconformities in the Zagros Mountains and episodes of eustatic sea-level low stands of Vail et al. (1977). Such observations suggest that supersequences of the Zagros Mountains must have formed in

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response to factors which influenced global stratigraphic characteristics. Therefore, the commonly accepted interpretation that these supersequences formed by local or regional epeirogenic movements needs to be re-evaluated. As such, the results of this investigation have broad implications for the evolution of the Zagros Mountains. The goals of this study are as

follows: (1) to provide an overview of existing sedimentological features of the Zagros Mountains, (2) to present a simplified synthesis of the Phanerozoic stratal packages of the Zagros Mountains, (3) to introduce a new, easily applicable nomenclature for these supersequences, and (4) to evaluate factors which led to the formation of these supersequences.

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This study is based on the existing sedimentologic and stratigraphic information. Data for the Zagros Mountains and Central Iran are derived from studies by James and Wynd (1965), Berberian and King (1981), and Motiee (1993). Those from the Arabian Peninsula are from Alsharhan and Kendall, (1986), Husseini (1989), McGillivray and Husseini, (1992), Beydoun (1991), Sharland et al. (2001), and Ziegler (2001). Supersequences of the Zagros Mountains, Central Iran, and the Arabian Peninsula are defined by detailed paleontological and sedimentological studies (James and Wynd, 1965; Motiee, 1993). The bounding unconformities were determined by the absence of well-know biozones (James and Wynd, 1965; Motiee, 1993). In most cases, gaps in paleontological record were accompanied by paleosols and other indicatives of subaerial exposure (James and Wynd, 1965; Motiee, 1993).

begins with the time interval encompassing that supersequence, for example the Ordovician. This is followed first by an indigenous name familiar to the region and then by the word supersequence. An example would be the Ordovician Kourosh Supersequence. The Ordovician prefix is adequate for global correlation of this supersequence. The indigenous names are founders and kings of the three pre-Islamic Iranian dynasties that governed the Zagros Mountains and adjacent regions for over 1200 years (Durant, 1954). Paleozoic supersequence names are derived from kings of the Hakhamaneshian (Achaemenid) Dynasty (550 B.C. to 330 B.C.); Mesozoic supersequences names are based on kings of the Ashkanian (Arsacid) Dynasty (200 B.C. to 100 A.D.); Cenozoic supersequence names originate from kings of the Sassanian (Sassanid) Dynasty (200 A.D. to 760 A.D.). All proposed indigenous names are not only familiar regionally but also known worldwide through Biblical stories and historical records (Durant, 1954; Asimov, 1981).

3. A new nomenclature

4. Regional tectonic history

A sequence consists of genetically related strata bounded by unconformities and their correlative conformities (see Vail et al., 1977; Wilgus et al., 1988; Loucks and Sarg, 1993; Harris et al., 1999; Sharland et al., 2001). Sequences occur in durations ranging from 102 to 107 years. Supersequences of this investigation, also known as Sloss Sequences, represent durations ranging from 10–100 Myr. Sequences are chronostratigraphic units. Therefore, methodology used for naming rock units cannot be used. This is because rock units (formations) are defined only by their lithologic characteristics without regards to the presence or absence of bounding unconformities or any time frameworks in which they occur. Despite their importance as globally distinct stratal packages, no methodology currently exists to name them. Commonly used terms are those of Sloss (1963) for the North American Carton which includes names such as Sauk, Tippecanoe, Kaskaskia, Absaroka, Zuni, and Tejas. Another set of terms were proposed by Sharland et al. (2001) and Ziegler (2001) who recognized these supersequences from the Arabia Peninsula and named them Arabian Plate Tectonostratigraphic Megasequences 1 to 11. Sloss's terminologies are unfamiliar and cumbersome for use in the Zagros Mountains. I have also avoided terminologies of Sharland et al. (2001) and Ziegler (2001) because they imply tectonic origins for these supersequences which contradict the main conclusion of this study. This investigation applies an informal but unique nomenclature to supersequences of the Zagros Mountains. Each name

Sedimentation in the Zagros Mountains occurred under the following three distinct phases (Fig. 2): (1) the Persian Platform Phase (Phase-I) from the latest Precambian to Early Permian, (2) the Arabian Platform Phase (Phase-II) from Permian to the latest Cretaceous, and (3) the Zagros Foreland Basin Phase (Phase-III) from the latest Cretaceous to the Present.

2. Methods

4.1. Persian platform phase This Persian Platform was broad, epeiric sea-type platform that existed from the latest Precambrian to the Permian (Golonka, 2000). It consisted of at least seven microcontinents including Central Iran, Sanandaj — Sirjan, Lut, Turkey, Tibet, Afghanistan, and Arabian microcontinents (Fig. 3A). The evolution of the Persian Platform is not fully understood (see Ramezani and Tucker, 2003; Horton et al., 2008-this volume). It is generally agreed that the Persian Platform was initiated by a cratonization event during the latest Precambrian when these microcontinents were accreted to Africa (Greenwood et al., 1976; Berberian and King, 1981; Husseini, 1989; Gass, 1981; Sharland et al., 2001). This tectonic activity left behind a set of east–west faults such as the Najd Fault system (Fig. 1). It is possible that some of the north–south structural elements of this region also formed during the Late Precambrian tectonic activities (Sharland et al., 2001; Sherkati and Letouzey, 2004). An extensional period either due to continental rifting or due to a back-arch basin affected the platform during the latest Precambrian resulting in the formation of intraplate depressions where

Fig. 2. Sedimentation in the Zagros Mountains experienced three phases during the Phanerozoic. (A) Persian Platform Phase (Phase-I). It occurred from the latest Precambrian to the Permian Period. The platform consisted of at least seven microcontinents including Central Iran, Sanandaj–Sirjan, Lut, Turkey, Tibet, Afghanistan, and Arabia. The platform may have been an active margin during the latest Precambrian to Cambrian and during the Late Devonian. However, the platform was a passive margin during Ordovician, Silurian, Early Devonian, and Carboniferous (see Golonka, 2000; Horton et al., this volume). This reconstruction shows the Precambrian–Early Cambrian interval of Phase-I (modified from Golonka, 2000 and Sharland et al., 2001). (B) Arabian Platform Phase (Phase-II). Several microntinents separated from the Persian Platform during the opening of the Neo-Tethys Ocean in Early Permian. Phase-II continued to the latest Cretaceous. This reconstruction shows Permian to Early Jurassic interval of Phase-II (modified from Golonka, 2000 and Sharland et al., 2001). (C) Zagros Foreland Basin Phase (PhaseIII). This phase was initiated during the latest Cretaceous when an active margin formed in the northeastern Zagros and continues to the Present (modified from Golonka, 2000 and Sharland et al., 2001). (D) Map shows the modern geology of Iran with its structural provinces. SE–NW line the position of stratigaraphic section shown in Fig. 4. This reconstruction shows Paleocene–Eocene part of Phase-III (modified from Alavi, 1994).

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major evaporites of this time interval were deposited (Berberian and King, 1981; Gorin et al., 1982; Husseini, 1989; Sharland et al., 2001; Ramezani and Tucker, 2003). Extensive carbonate deposition suggests the presences of a passive margin setting during the Cambrian but detailed investigations have concluded that the platform was an active margin during this time interval (Golonka, 2000; Horton et al., 2008-this volume) (Fig. 2A). Subsequently, the platform became a passive margin from Ordovician to Middle Devonian and from Mississippian to Permian (Golonka, 2000). Whereas an active margin was established during Late Devonian (Golonka, 2000). The similarity in sedimentological characteristics of the uppermost Precambrian to Permian strata suggests that all microplates of the Persian Platform remained together during this time interval (Stöcklin, 1968; Berberian and King, 1981; Davoudzadeh and Schmidt, 1984; Davoudzadeh et al., 1986; Dacoudzadeh and Weber-Diefenbach, 1987; Beydoun, 1991). 4.2. The Arabian platform phase During the Early Permian time, several microplates collectively referred to as the Cimmerian continent separated from the Persian Platform forming the Neotethys Ocean (Dercourt et al., 1986; Kazmin, 1991; Stampfli et al., 1991; Golonka, 2000) (Fig. 2B). This event could have also produced a horst and graben system close to northeastern edge of the Zagros region (Sharland et al., 2001; Ziegler, 2001; Weidlich and Bernecker, 2003). Then after, the Zagros region became a part of the Arabian Platform. This phase continued until the latest Cretaceous (Fig. 2B). The Zagros region was the site of passive margin sedimentation as the Neotethys Ocean widened. The Sanandaj–Sirjan microplate separated from the Arabian Platform during the latest Triassic to the earliest Jurassic (Golonka, 2000). The regime between the Sanandaj–Sirjan microplate and the Arabian Platform changed during the latest Cretaceous and the platform changed from passive to an convergent margin setting (Golonka, 2000). A specific characteristic of the Arabian Platform phase was the formation of two intrashelf basins (the Dezful Embayment and the Lurestan basin) in the Zagros region during this time interval (see Sepehr and Cosgrove, 2004, 2005).

microcontinent during the Zagros Orogeny closing the Neotethys Ocean and forming the fold and thrust belt of the Zagros Mountains (Berberian and King, 1981; Alavi, 1980, 1994; Golonka, 2000). The timing of this collision is debated, however (see Fakhari et al., 2008-this volume; Horton et al., 2008-this volume). 5. Tectonic provinces of the Zagros Mountains The Zagros Fold and Thrust Belt (ZFTB) consists of two regions (Fig. 1). The High Zagros Zone (HZZ) is bounded by the Zagros Main Thrust Fault (ZMTF) to the northeast and the High Zagros Fault (HZF) to the southwest. The HZZ is characterized by intense structural deformation and faulting (Sepehr and Cosgrove, 2004; Sherkati and Letouzey, 2004; Sherkati et al., 2006). To the south of the HZZ is the Simply Folded Zone (SFZ) which is bounded by the HZF to the northeast and the Zagros Frontal Fault (ZFF) to the southwest (Fig. 1). The Dezful Embayment and the Lorestan Basin are two intrashelf depressions that occur in the SFZ (Fig. 1). These two basins are bounded by the Kazerun (KZ) and Bala Rud (BRF) faults (Fig. 1). The southern part of the SFB is the Arabian Homocline (AH) which is characterized by gently dipping strata (Fig. 1). 6. Phanerozoic migration path of the Zagros Mountains The Zagros region experienced a “C”-shaped migration path during the Phanerozoic (Fig. 3). The area was located near the equator and 150° E longitude during the latest Precambrian (Golonka, 2000). It then followed a southwestward movement that continued during the Ordovician and Silurian reaching as far as 60° S latitude and 30° E longitude (Golonka, 2000). The area began a minor northward path during the Devonian reaching 30° S latitude followed by another minor southward movement (Golonka, 2000). Beginning in Carboniferous, the region began a northerly migration more or less along the 30° E longitude from its southern most position at nearly 50° S latitude. The area reached 30° S latitude by the Permian, 15° S by the Triassic, near the equator by the Cretaceous, and finally to its present-day location of about 30° N latitude by the Oligocene (Golonka, 2000).

4.3. The Zagros Foreland basin phase 7. Previous studies The Arabian Platform Phase was terminated when the Sanandaj–Sirjan microplate collided with the Arabian Platform during the latest Cretaceous (Golonka, 2000). In addition, the Neotethys Ocean became progressively narrower during this time due to a subduction zone in its northern margin (Golonka, 2000). Active margin processes established in the Zagros region. These events initiated the Zagros Foreland Basin Phase which continues to the present time (Fig. 2C) (Sharland et al., 2001; Sepehr and Cosgrove, 2004; Sherkati and Letouzey, 2004; Sherkati et al., 2006). The Zagros Foreland Basin Phase (PhaseIII) was characterized by the formation of a narrow, northwest– southeast foreland basin where Cenozoic strata were deposited (Fig. 2C). The Arabian Plate eventually collided with Iran

Despite their enormous scientific and economic importance, the Phanerozoic strata of the Zagros Mountains are poorly represented in English-language literature. Early studies of this region were related to either cursory examinations of salt plugs or to general characteristics of hydrocarbon reservoirs (Lees, 1933; Falcon, 1958; Kent, 1958; Dunnington, 1967; Ala, 1974; McQuillan, 1991). The most fundamental work was conducted by James and Wynd (1965) who established the framework for Mesozoic and Cenozoic stratigraphy of the Zagros Mountains. This was followed by other equally significant contributions on regional lithofacies patterns by Murris (1980), Berberian and King (1981), Davoudzadeh and Schmidt, (1984), Davoudzadeh

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Fig. 3. The Zagros Mountains experienced a “C”-shaped migration path from the latest Precambrian to the Recent. The platform was located near the equator and 150° E longitude during the latest Proterozoic. It moved a southwestward to as far as 60° S latitude and 30° E longitude by the Carboniferous. It then continued a more or less northerly direction from Early Carboniferous reaching its present-day location of nearly 30° N latitude and 30° E longitude (Data from Golonka, 2000).

et al. (1986), and Dacoudzadeh and Weber-Diefenbach (1987). Motiee (1993) provided a regional synthesis of the Phanerozoic strata of the Zagros Mountains. Few detailed studies that concentrated on individual formations include Szabo and Kheradpir (1978) on Permian strata, Setudehnia (1978) on Mesozoic carbonates, Gill and Ala (1972) and Kashfi (1980) on Miocene strata. Studies which incorporate the modern concepts of stratigaraphy have only recently begun. These include contributions of Goff et al. (1994), Seyrafian (1998, 2000), Moghaddam et al. (2002), Bahroudi and Koyi (2004), Hessami et al. (2001), Mohseni and Al-Aasm (2004), Nadjafi et al. (2004), and VaziriMoghaddam et al. (2005), all on the Cenozoic strata, and Insalaco et al. (2006) on the Permian–Triassic carbonates. A few investigations reported on the organic geochemistry of hydrocarbon source rocks of this region and include studies by Dashti (1987), Bordenave and Burwood (1989), Kamali and Rezaee (2003), and Bordenave and Hegre (2005). Phanerozoic supersequences of the Zagros Mountains have time correlative

equivalents in the neighboring areas which are summarized by Beydoun (1991), Sharland et al. (2001), and Ziegler (2001), and Haq and Al-Qahtani (2005). 8. Supersequences of the Zagros Mountains A NW–SE stratigarphic cross section of the Zagros Mountains is shown in Fig. 4, whereas Fig. 5 demonstrates the Phanerozoic strata of the southeastern part of the Zagros Mountains, those of central Arabia, and the Paleozoic strata of the Central Iran microplate. Formation names, ages, general lithologies, and depositional environments of each region are summarized in Tables 1–3. A cursory look at the Phanerozoic stratigraphy of the Zagros Mountains shows the presence of stratal packages separated by major unconformities (Figs. 4, 5). Twelve supersequences were recognized and named following the proposed nomenclature of this investigation. They include the following: (1) Precambrian– Cambrian Hakhamanesh Supersequence, (2) Ordovician Kourosh Supersequence, (3) Silurian Camboojiyeh Supersequence, (4)

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Fig. 4. NW–SE stratigraphic section of the Zagros Mountains. Names, ages, lithologies, and depositional environments of formations are shown in Table 1 (modified from James and Wynd, 1965; Motiee, 1993). PC = Precambrian; C = Cambrian; O = Ordovician; S = Silurian; D = Devonian; M = Mississippian; Pen = Pennsylvanian; Per = Permian; T = Triassic; J = Jurassic; K = Cretaceous; Pl = Paleocene; Eo = Eocene; Ol = Oligocene; Mi = Miocene; Pl = Pliocene; PH = Pleistocene–Holocene.

Devonian Darioush Supersequence, (5) Mississippian–Pennsylvanian Khashayar Supersequence, (6) Permian–Triassic Ashk Supersequence, (7) Jurassic Farhad Supersequence, (8) Early Cretaceous Mehrdad Supersequence, (9) Late Cretaceous Ardavan Supersequence, (10) Paleocene–Oligocene Sassan Supersequence, (11) Oligocene–Miocene Ardeshir Supersequence, and (12) Miocene–Pleistocene Shapour Supersequence. 9. Discussion The supersequences of the Zagros Mountains and adjacent areas have been known for more than four decades. Previous

investigators have emphasized that these stratal packages were developed primarily as a result of local or regional tectonic activities with little to no influence from sea-level change (Berberian and King, 1981; Beydoun, 1991; Sharland et al., 2001; Alavi, 2004). Some of the causal tectonic events utilized to explain these supersequences include hinterland uplift (Ordovician), Hercynian Orogeny (latest Crboniferous), Neotethys Opening (Late Permian), rifting of India (Early Jurassic), Rifting in the eastern Mediterranean (late Early Jurassic), opening of the south Atlantic (Early Cretaceous), opening of the Mediterranean (middle Cretaceous), beginning of the ophiolite obduction along the northeast margin (Late Cretaceous), end of the ophiolite

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Fig. 5. (A) Geological periods. Symbols as in Fig. 4. Cen = Cenozoic. (B) Geological Epochs. Symbol as in Fig. 4. PPH = Pliocene–Pleistocene–Holocene. E = Early, M = Middle, L = Late. (C) Phanerozoic stratigraphic column from the central portion of the Arabian Peninsula (from Husseini, 1989; Alshahran and Kendall, 1986; Beydoun, 1991; McGillivray and Husseini, 1992). Numbers refer to formation names in Table 3. (D) Phanerozoic stratigraphic column from the southeastern Zagros Mountains (from James and Wynd, 1965; Motiee, 1993). Numbers refer to formation names in Table 1. (E) Paleozoic stratigraphic column from the Central Iran microcontinent (from Berberian and King, 1981). The Central Iran microplate separated from the Persian Platform during the Permian Period. Therefore, its Mesozoic and Cenozoic record is not shown here. Numbers refer to formation names in Table 2. (F) Supersequence names applied to the Zagros Mountains Central, Iran, and Central Arabia. (G) Major glacial events of the Phanerozoic. (H) Major tectonic episodes that occurred during each supersequence (from Golonka, 2000). 1 = Assembly of the Pannotia Supercontinent; 2 = Break-up of the Pannotia Supercontinent to Gondwana, Baltica, Siberia, and Laurentia; 3 = Continued rifting of Baltica, Laurentia, and Siberia and formation ice cap on Gondwada during the Late Ordovician; 4 = Caledonian Orogeny, Acadian Orogeny; 5 = Latest stages of Acadian Orogeny, the onset of Hercynian Orogeny, Antler Orogeny; 6 = Hercynian Orogeny continues, Antler Orogeny Continues, Alleghenian Orogeny; 7 = Assembly of Pangea, Ouachita Orogeny, rifting of Cimmerian Continent from the Persian Platform, opening of the Neotethys Ocean; 8 = Break-up of Pangea, separation of Gondwana from Laaurasia, opening of the North Atlantic, closer of Paleotethys, Sanandaj–Sirjan separated from Arabian margin, break-up of Gondwana began; 9 = Break-up of Pangea and Gondwana continued, initial separation of India from Gondwana began; 10 = South Atlantic opened, Arabian Platform began to converge with Sanandaj–Sirjan microplate, obduction of ophiolite on the Arabian Platform, India moved northward; 11 = India collided with Eurasia, closing of Neotethys, Alpine–Himalaya Orogeny began; 12 = Alpine–Himalaya Orogeny continued, Sanandaj–Siraj began to thrust over Arabian Plate; 13 = Mountain building in Alpine–Himalaya belt. (I) The relative sea-level chart is drawn based on the depositional environments of the adjacent units as well as the coastal on-lap data from Ziegler (2001). Period boundary ages are from Gradstein and Ogg (2004).

obduction (Early Paleocene), closure of the Tethys Ocean (Late Eocene), and opening of the Red Sea (Late Oligocene) (Sharland et al., 2001). Recently, Haq and Al-Qahtani (2005) presented the higher order sequences from the Arabian Peninsula and adjacent regions reemphasizing the role of sea-level in the formation of these stratal packages. A NW–SE trend in sedimentation pattern was established in the Zagros Mountains during the latest Paleozoic and became well developed during Mesozoic and Cenozoic times (Fig. 4). Strata become fine grained, restricted, evaporative, and display deposition in deeper water environments toward the northwestern region of the Zagros Mountains (Fig. 4). Therefore, I agree with the previous interpretations that these changes in lithofacies characteristics were influenced by the tectonically induced formation of intra-shelf depressions such as the Dezful Embayment and the Lorestan Basin (Motiee, 1993; Sepehr and Cosgrove, 2004; Sherkati and Letouzey, 2004). Another similar event included the formation of the Hormoz Salt Basin during the

Precambrian (Fig. 1). However, the following analysis of lithofacies and their depositional environments will demonstrate that the supersequences of the Zagros Mountains formed as a result of the second-order eustatic sea-level changes. 9.1. Precambrian–Cambrian Hakhamanesh Supersequence The name of this supersequence is derived from Hakhamanesh or Achamenes who founded the Achaemnid Dynasty (550 B.C. to 330 B.C.). The Zagros area was located at 5°–20° S latitude during the Precambrian–Cambrian time (Fig. 3). The latest Precambrian Hormoz Salt was deposited in several intrashelf basins during the first incursion of marine water (Figs. 4–5). Strata older than the Hormoz Salt have not yet been discovered from the Zagros region but were reported from adjacent areas such as the central Iran microcontinent (Berberian and King, 1981; Kashfi, 1985; Beydoun, 1991). The continuation of the relative sea-level rise resulted in deposition and subsequent dolomitization of Soltaniah

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Table 1 Table shows names, ages, lithologies, and depositional environments of the latest Precambrian to Recent formations of the Zagros Mountains

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

Fm name

Age

General lithology

Depositional environments

Hormoz Soltaniah Barut Zagun Lalun Mila Ilebeyk Zard Kuh

L. Precambrian–E. Cambrian L. Precambrian–E. Cambrian E. Cambrian E.–M. Cambrian E.–M. Cambrian M. Cambrian–E. Ordovician E. Ordovician E.–M. Ordovician E.–L. Silurian Devonian–M. Permian L. Permian E.–M. Triassic E. Triassic E.–M. Triassic E. Jurassic E.–L. Jurassic L. Jurassic E.–L. Jurassic L. Jurassic E. K: Neocomian E. K: Neocomian–Aptian E. K: Aptian E.–L. K: Albian–Cenomanian E.–L. K: Albian–Turonian E.–L. K: Neocomian–Coniacian L. K: Turonian–Santonian L. K: Santonian–Campanian L. K: Campanian–Maaestrichtian L. K: Campanian–Maaestrichtian L. Cretaceous–E. Eocene Paleocene–L. Eocene Paleocene–Miocene L. Cretaceous–Paleocene Paleocene–M. Eocene Paleocene–M. Eocene M.–L. Eocene Oligocene–E. Miocene E. Miocene E. Miocene E.–M. Miocene L. Miocene–Pliocene L. Pliocene–Pleistocene

Halite with some anhydrite Dolomite and red shale Dolomite and shale Red and purple shale Pink and white sandstone Dolomite, shale, and limestone Gray and green shale Gray shale and sandstone Graptolitic shale Sandstone and conglomerate Carbonate and evaporite Dolomite Carbonate and evaporite Anhydrite Dolomite Dolomite Anhydrite Anhydrite and limestone Anhydrite Limestone Marl and limestone Limestone Bituminous shale Limestone Shale, argilaceous limestone Dark gray shale Argilaceous limestone Dark gray shale and marl Anhydrite Gypsum, marl, limestone Dolomite Gray shale and marl Siltstone and sandstone Limestone Red sandstone and conglomerate Dolomite and limestone Limestone Anhydrite, halite, carbonate Red marl and siltstone Limestone Sandstone and siltstone Conglomerate

Hypersaline lagoon Shallow marine Shallow marine Fluvial Near shore marine, deltaic Shallow marine Fluvial to near shore marine Deep marine Deep marine Fluvial to deltaic Shallow marine Shallow marine Shallow marine Restricted marine Supratidal to shallow marine Shallow marine Hypersaline lagoon Hypersaline lagoon Hypersaline lagoon Shallow marine Shallow marine to bellow wave base Shallow marine Deep marine Shallow marine Deep marine Deep marine Shallow to moderately deep marine Deep marine Shallow marine Restricted marine Shallow marine Deep marine Turbidite Shallow marine Fluvial Shallow marine Shallow marine Restricted shallow marine Terrestrial Shallow marine Lacustrine to near shore marine Alluvial–fluvial

Faraghan Dalan Khaneh Kat Kangan Dashtak Neyriz Surmeh Hith Shireen Gothnia Fahliyan Gadvan Dariyan Kazhdumi Sarvak Garau Surgah Ilam Gurpi Tarbur Sachun Jahrum Pabdeh Amiran Talezang Kashkan Shahbazan Asmari Gachsaran Razak Mishan Agha Jari Bakhtiari

Numbers in the left column correspond to formation names in Figs. 4 and 5. Data and information are from James and Wynd (1965), Berberian and King (1981), and Motiee (1993). The only exception is the informally named Lower to Upper Jurassic Shireen Formation (#18) which occurs in the northwestern part of the Zagros Mountains. The name is derived from the near-by town of Ghaser-e Shireen. In this study, the Shireen Formation is subdivided into five members. From bottom to top, they are: (1) Adaiyah Anhydrite, (2) Mus Limestone, (3) Alan Anhydrite, (4) Sargelu Shale, and (5) Najmeh Limestone (James and Wynd, 1965; Motiee, 1993). E = Early; L = Late; M = Middle; K = Cretaceous.

and Barut formations (Figs. 4–5). Fluvial deposition of the Zagun Formation may have been the result of a minor relative sea-level fall (Figs. 4–5). A second phase of the relative sea-level rise was initiated with the deposition of near-shore marine terrigenous strata of the Lalun Formation, followed by fully marine carbonate and shale of the Mila Formation (Figs. 4–5). 9.2. Ordovician Kourosh Supersequence The name of this supersequence comes from Kourosh (550–529 B.C.) the first king of the Achaemenid Dynastry or Cyrus the Great of the Bible (Asimov, 1981). The Zagros

region was located around 30°–35° S latitude and drifted to 40° S by the end of the Ordovician time (Fig. 3). The deposition of this supersequence initiated a period of stability in a passive margin setting which lasted until the Permian Period (Golonka, 2000). The fluvial to near-shore marine deposits of the Ilebeyk Formation suggest initial stages of a marine incursion (Fig. 4). This was followed by deposition of deep-marine shales of the Zard Kuh Formation, suggesting a major relative sea-level rise which covered the entire Persian Platform (Fig. 5). An abrupt sea-level fall, possibly linked to Late Ordovician glaciations, terminated the deposition of Ordovician Kourosh Supresequence.

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Table 2 Table shows names, ages, lithologies, and depositional environments of Paleozoic formation of the Central Iran microcontinent

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Fm Name

Age

General Lithology

Depositional Environments

Morad Soltaniah Barut Zagun Lalun Kalshaneh Derenjal Shirgest Niur Padeha Sibzar Bahram Shistu Sardar Jamal

L. Precambrian–E. Cambrian L. Precambrian–E. Cambrian E. Cambrian E.–M. Cambrian E.–M. Cambrian M. Cambrian M.–L. Cambrian E.–L. Ordovician M.–L. Silurian L. Silurian–E. Devonian M. Devonian M.–L. Devonian L. Devonian E. Mississippian–E. Permian E. to L. Permian

Halite with some anhydrite Dolomite and red shale Dolomite and shale Red and purple shale Pink and white sandstone Dolomite, shale, gypsum, volcanics Marl, limestone, dolomite, siltstone Shale, limestone, marl Limestone, shale Sandstone Dolomite Limestone, marl, shale Shale, marl, limestone Shale, sandstone, limestone Limestone, dolomite

Hypersaline lagoon Shallow marine Shallow marine Fluvial Near shore marine, deltaic Shallow marine Shallow marine Shallow–moderately deep marine Shallow–moderately deep marine Near shore to shallow marine Shallow marine Shallow marine Shallow marine Shallow marine to coastal Shallow marine

Numbers in the left column correspond to formation names in Fig. 5. Data and information are from Berberian and King (1981). E = Early; L = Late; M = Middle.

9.3. Silurian Camboojiyeh Supersequence The name of this supersequence is derived from Camboojiyeh (529–522 B.C.) the second king of the Achaemenid Dynastry or Cambyses of the Bible (Asimov, 1981). The Zagros region drifted

southwestward reaching near 55° S latitude by the end of Silurian time (Fig. 3). Glacial deposits initiated the latest Ordovician– Silurian Camboojiyeh Supersequence (Fig. 4). The record of such glaciations has not been reported from the Zagros Mountains, but it was preserved in the Arabian Peninsula (McGillivray and Husseini,

Table 3 Table shows names, ages, lithologies, and depositional environments of the latest Precambrian to Recent formations of the central part of the Arabian Peninsula

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Fm Name

Age

General lithology

Depositional environments

Robutain Badayi Muraykhan Saq Qasim Zarqa–Sarah Qaliba Tawil Jauf Jubah Unayzah Khuff Sudair Jilh Minjur Murrat Dhruma Twaig–Arab Hith Sulaiy Biyady Wasia Aruma Radhuma Rus Dammam Hadrukh Dam Hofuf Bahr

L. Precambrian L. Precambrian L. Precambrian–E. Cambrian E. Cambrian–E. Silurian E.–M. Ordovician L. Ordovician E.–M. Silurian E. Devonian E.–M. Devonian M. Devonian M. Carboniferous–E. Permian L. Permian E. Triassic M. Triassic L. Triassic E. Jurassic M. Jurassic L. Jurassic L. Jurassic E. Cretaceous E. Cretaceous E. Cretaceous L. Cretaceous Paleocene–E. Eocene E. Eocene M.–L. Eocene E. Miocene M. Miocene L. Miocene Pliocene–Pleistocene

Sandstone Siltstone Dolomite and limestone Sandstone Shale and sandstone Conglomerate and sandstone Shale at base, sandstone at top Sandstone Sandstone and shale Sandstone Sandstone and conglomerate Carbonate and evaporite Dolomite Dolomite Sandstone Dolomite Limestone Limestone Anhydrite Limestone Siltstone and sandstone Sandstone Limestone Limestone Anhydrite Limestone Siltstone and sandstone Marl and limestone Sandstone and conglomerate Conglomerate

Shallow marine to evaporitic Fluvial to coastal marine Deep marine Glacial Deep marine Fluvial Fluvial to near shore marine Fluvial to near shore marine Fluvial and alluvial Continental to near shore marine Shallow marine Shallow marine Near shore marine Shallow marine to near shore marine Shallow marine Shallow marine Hypersaline lagoon Shallow marine Shallow marine–coastal Marginal marine–coastal Marginal marine–coastal Shallow marine Sabkha–lagoonal Shallow marine Coastal–fluvial Shallow marine Continental–lacustrine Fluvial–Alluvial

Numbers correspond to formation names in Fig. 5. Data and information are from McGillivray and Husseini (1992), Beydoun (1991), Sharland et al. (2001). E = Early; L = Late; M = Middle.

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1992; Sharland et al., 2001) (Fig. 5). A rapid relative sea-level rise, possibly due to the melting of glaciers, during the latest Ordovician resulted in the deposition of deep-water graptolitic shales of the Zagros region and central Arabia (Figs. 4–5). 9.4. Devonian Darioush Supersequence The name of this supersequence is taken from Darioush (522–486 B.C.) the third king of the Achaemenid Dynastry or Darius the Great of the Bible (Asimov, 1981). The platform started its northerly drift, reaching nearly 30° S latitude by the end of Devonian (Fig. 3). Fluvial to deltaic deposits of the Faraghan Formation in the Zagros suggests the initial stages of a sea-level rise that formed the latest Silurian–latest Devonian Darioush Supersequence (Figs. 4–5). Marginal marine equivalent strata in central Arabia and Central Iran support this interpretation. 9.5. Mississippian–Pennsylvanian Khashayar Supersequence The name of this superquence comes from Khashayar (486– 465 B.C.) the fourth king of the Achaemenid Dynastry or Xerxes of the Bible (Asimov, 1981). The Zagros region was located at around 30°–50° S latitude but was rotated in a N–S orientation by the Mississippian time (Fig. 3). The strata belonging to the Khashayar Supersequence have not yet been unequivocally defined in the Zagros Mountains. However, time equivalent shallow marine strata were deposited on the Central Iran microplate (Fig. 5). This hiatus in the Zagros Mountains has frequently been related to the “Hercynian” event (Sharland et al., 2001). However, this time interval coincides with a major glacial episode of the southern Hemisphere (Golonka, 2000). Therefore, the absence of the Khashayar Supersequence in the Zagros Mountains and the Arabian Peninsula indicates a very low sealevel due to the southern Hemisphere glaciations (Fig. 4). 9.6. Permian–Triassic Ashk Supersequence The name of this supersequence is derived from Ashk or Arsaces of the Bible (Asimov, 1981), the founder of the Ashkanian or Parthian Dynasty (200 B.C to 100 A.D.). The Zagros region continued drifting northward reaching approximately 10° S latitude during the Permian–Triassic interval (Fig. 3). A major rifting event resulted in the separation of several segments including the Central Iran microplate from the Persian Platform establishing a passive margin setting (Fig. 2B). A thin layer of sandstone of possible deltaic origin initiated a major sea-level rise which eventually led to the deposition of the Ashk Supersequence (Fig. 4). This supersequence is characterized by major carbonate reservoirs in the Dalan Formation of the Zagros Mountains and equivalent strata in adjacent regions (Fig. 5). The carbonate– evaporite characteristics of the Ashk Supersequence suggest a marine environment which was restricted at times (Szabo and Kheradpir, 1978; Kashfi, 1992). Deposition of the Ashk Supersequence which had begun during the Permian Period continued during the Triassic (Figs. 4–5). The Lower to Middle Triassic Khaneh Kat Formation is primarily

dolomitic and its lithologic and paleontological characteristics suggest deposition in a shallow marine environment (Setudehnia, 1978; Szabo and Kheradpir, 1978). Abundant anhydrite in the Lower Triassic Kangan and the Lower to Middle Triassic Dashtak formations in the northwestern part of the Zagros Mountains suggests an arid climate and restricted marine environments there (Setudehnia, 1978; Szabo and Kheradpir, 1978; Kashfi, 1992). NW–SE variations indicate that tectonic activity initiated a depression toward the northwestern Zagros where evaporites of the Ashk Supersequence were deposited. 9.7. Jurassic Farhad Supersequence The name of this supersequence is taken from Farhad (176– 171 B. C.) the fourth king of the Ashkanian (Parthian) Dynasty or Phraates of the Bible (Asimov, 1981). The Zagros region continued to move northward reaching approximately 10° N by the end of the Jurassic time during which the platform retained its passive margin setting (Fig. 3). Thin-bedded dolomites of the Lower Jurassic Neyriz Formation suggest shallow restricted marine conditions during initial sea-level rise that established the Jurassic Farhad Supersequence (Fig. 4). Thick dolomites of the Lower to Upper Jurassic Surmeh Formation constitute the bulk of this supersequence in the southeastern part of the Zagros Mountains (Fig. 4). Lithofacies of the Surmeh Formation were deposited on an open marine shelf indicating a major relative sea-level rise in the region (James and Wynd, 1965; Setudehnia, 1978; Motiee, 1993). The widespread deposition of the overlying Hith Anhydrite in lagoonal to supratidal environments indicates a lowering of relative sea-level at the end of the Jurassic and the exposure of the platform at that time (Figs. 4–5). Tectonic process continued to form intrashelf depressions in the northwestern region of the Zagros Mountains where the hypersaline strata of the Shirin Formation were deposited (Fig. 4). Deposition of the overlying uppermost Jurassic Gothnia Anhydrite indicates a lowering of sea-level and establishment of evaporitic condition, in the northwestern part of the Zagros Mountains (Figs. 4–5). The NW–SE trend in lithology of time correlative strata of the Jurassic section suggests evidence for well established depocenters in the northwestern Zagros Mountains at this time (Fig. 4). 9.8. Early Cretaceous Mehrdad Supersequence The name of the supersequence is derived from Mehrdad (171–139 B.C.) the fifth King of the Ashkanian (Parthian) Dynasty or Mithradates the Great of the Bible (Asimov, 1981). The Zagros region continued moving northward reaching 15° N latitude during the Early Cretaceous (Fig. 3). The platform maintained its passive margin setting. In the southeastern region of the Zagros Mountains succession begins with open marine strata indicative of a major relative sea-level rise in the Cretaceous initiating deposition of the Mehrdad Supersequence (Fig. 4). Organic-rich strata of the Gadvan and Garau formations formed during a major relative sea-level rise and deposition of deep-water strata (James and Wynd, 1965; Setudehnia, 1978). Marine, fossiliferous strata of the Neocomian Fahliayan Formation and the Aptian Dariyan Formation support this interpretation (Fig. 4). A

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small relative sea-level fall may have occurred at the end of the Dariyan Formation, resulting in minor exposure of the platform (Fig. 4). A subsequent relative sea-level rise led to a second phase of organic-rich marine deposition of the Aptian–Cenomanian Kazhdumi Formation, and its time equivalent the fossiliferours Sarvak Formation (Figs. 4–5). Open marine carbonates of the Mehrdad Supersequence covered the entire platform (Fig. 5). A major unconformity terminated the deposition of the Mehrdad Supersequence leading to the formation of a major paleosol at this interval (James and Wynd, 1965; Motiee, 1993). Tectonics continued to produce intrashelf basins in the northwestern Zagros leading to a well-developed establishment of the NW–SE trend in lithofacies variations during the deposition of Mehrdad Supersequence (Fig. 4). Deep-water marine shales of the Garau Formation were deposited in these intrashelf depressions (Fig. 4). 9.9. Late Cretaceous Ardavan Supersequence The name of this supersequence is derived from Ardavan (129–124 B.C.) or Artanabus of the Ashkanian Dynasty. The platform continued to move northward reaching a location close to 10–15° N latitude in the Late Cretaceous (Fig. 3). The shallow to moderately deep-water deposits of the Santonian– Campanian Ilam Formation suggest a second sea-level rise initiating the late Cretaceous Ardavan Supersequence (Figs. 4–5). The relative sea-level rise flooded the region resulting in the deposition of organic-rich shales of the Campanian–Maestrictian Gurpi Formation across the platform (Fig. 4). Anhydrites of the Campanian–Maestrictian Tarbur Formation suggest the shallowing of relative the sea-level at the end of the Ardavan Supersequence, eventually led to exposure of the platform and formation of paleosols (James and Wynd, 1965; Motiee, 1993). The passive margin setting that had existed since the Permian was terminated near the end of the Ardavan Supersequence (Golonka, 2000; Sharland et al., 2001; Sepehr and Cosgrove, 2004; Sherkati and Letouzey, 2004; Sherkati et al., 2006). The subsequent convergent margin initiated the Zagros Foreland Basin Phase (Phase-III). 9.10. Paleocene–Oligocene Sassan Supersequence The name of this superseuqnece is derived from Sassan, the founder of the Sassanid Dynasty (200 A.D. to 760 A.D.). Closing of the Neotethys Ocean continued during the Paleogene, pushing the Zagros region to approximately 30° N latitude (Fig. 3). Deposition of Paleocene to Miocene marine shales of the Pabdeh Formation in the central and the northwestern Zagros (Fig. 4) initiated deposition of the Sassan Supersequence which coincided with the establishment of a NW–SE-trending foreland basin in the Zagros region (Beydoun, 1991; Sharland et al., 2001; Ziegler, 2001; Sepehr and Cosgrove, 2004; Sherkati and Letouzey, 2004). Therefore, in addition to the relative sea-level change, the deposition of Cenozoic supersequences (Sassan, Ardeshir, Shapour) were also influenced by the collision-related processes (Hessami et al., 2001; Bahroudi and Koyi, 2004). Evaporites of the

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Sachun Formation and dolomites of the Jahrum Formation suggest shallow marine environments in the southeastern part of the Zagros Mountains (James and Wynd, 1965; Motiee, 1993; Seyrafian, 1998). Deep-water turbidites of the Amiran Formation formed by turbidity flows caused by the instability associated with the on-going collision tectonics (James and Wynd, 1965; Motiee, 1993). A major and possibly rapid sealevel fall exposed the platform leading to formation of paleosols and the termination of the deposition of the Sassan Supersequence (Figs. 4–5). 9.11. Oligocene–Miocene Ardeshir Supersequence The name of this supersequence is derived from Ardeshir-I (224–241 A.D.) or Artaxerxes of the Sassanid Dynasty. During the Oligocene–Miocene, the Zagros region continued its northward movement reaching its present location at approximately 35° N latitude as Arabia collided with the Central Iran microcontinent (Figs. 2–3). Deposition of the Asmari Limestone indicates the flooding of the basin and initiation of the Ardeshir Supersequence (Fig. 4). This was followed by carbonate and evaporites of the Gachsaran Formation suggesting that the open marine environments of the Asmari Limestone quickly turned into restricted and lagoonal conditions (James and Wynd, 1965; Gill and Ala, 1972; Kashfi, 1980; Motiee, 1993). Such a rapid change in lithology indicates that the foreland basin was restricted. Strike-parallel heterogenous deformation created as many as six sub-basins which influenced the lithological characteristics of the Gachsaran Formation (Bahroudi and Koyi, 2004). 9.12. Miocene–Pleistocene Shapour Supersequence The name of this supersequence is taken from Shapour-I (241–272 A.D.) or Shapur-I of the Bible (Asimov, 1981). During the Miocene–Pleistocene, the Zagros region was characterized by near shore and fluvial depositional systems. A relative sealevel rise led to the deposition of shallow marine limestones of the Mishan Formation of the Shapour Supersequence (Fig. 4). This supersequence continued with the deposition of lacustrine to shallow marine deposits of the Agha Jari Formation. There after, uplift and erosion of previously deposited strata were the dominant processes leading to deposition of conglomerates of the Bakhtiari Formation (James and Wynd, 1965; Motiee, 1993). 10. Global Correlation of Zagros Supersequences This study reconstructed the relative sea-level history of the Zagros region based on lithofacies characteristics and depositional environments of Phanerozoic strata (Fig. 5). Deposition of deep-water, marine shales indicates episodes of relative sea-level rise (Fig. 5). Unconformities suggest periods of relative sea-level falls (Fig. 5). Surprisingly, the relative sea-level curve constructed for the Zagros Mountains correlates perfectly with the second-order eustatic sea-level curve of Vail et al. (1977) (Fig. 6). In fact, it appears that supersequences of the Zagros region are nearly

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E. Heydari / Tectonophysics 451 (2008) 56–70

Fig. 6. (A) Eustatic second-order sea-level chart from Vail et al. (1977). Also shown are Sloss sequences. (B) The supersequences and the relative sea-level change of the Zagros Mountains of this study. Note that the two sea-level changes correlate very well indicating the supersequences of the Zagros Mountains were formed by changes in eustatic sea-level rather than regional epeirogenic movements and/or tectonic activities. See Figs. 4 and 5 for periods and epoch symbols. Period boundary ages are from Gradstein and Ogg (2004).

identical to those reported from the North American Craton and the Russian Platform by Sloss (1963, 1972) (Fig. 6). Similar Paleozoic supersequences were also described from other regions of Iran (Lasemi, 2000) suggesting that the results of this study can be extended to other Iranian geological provinces and possibly to other parts of the Tethys region. The small difference between the relative sea-level curve of the Zagros Mountains and the second order eustatic sea-level curve of Vail et al. (1977) could be due to poor paleontological data in the Zagros Mountains as well as the differences in tectonic setting of the Zagros Mountains and the North American craton. The origin of Sloss-type supersequences has been the topic of discussions since their introduction by Sloss (1963). Three mechanisms have been proposed: (1) dynamic topography which relates supersequence formation to continent-wide thermal uplift produced by mantle heat. (2) Second-order sea-level change caused by variations in the volume and the spreading rates of midocean ridges; and (3) subsidence at cratonic margins due to extension tectonics or crustal loading (see Plint et al., 1992; Burgess et al., 1997; Eriksson et al., 2005). The first and third mechanism can influence sedimentation on regional scales. However, only a second-order sea-level change is capable of producing the Sloss-type sequences which can be correlated from one continent to another (Plint et al., 1992; Burgess et al., 1997; Eriksson et al., 2005). Therefore, this study concludes that supersequences of the Zagros Mountains are a direct manifestation of the second-order relative sea-level change in this region. It is highly unlikely that

supersequences of the Zagros Mountains were produced by local or regional tectonic features such as those proposed by Sharland et al. (2001) and Ziegler (2001). This conclusion of this study makes it necessary to revaluate the significance of tectonic events so often used to interpret the geological evolution of the Zagros Mountains. Although local or regional tectonic activities were incapable of producing the supersequences of the Zagros Mountains, they influenced sedimentation by the formation of intrashelf basins during the Precambrian and the Mesozoic (Sepehr and Cosgrove, 2004; Sherkati and Letouzey, 2004; Sherkati et al., 2006). Collision margin-related tectonics also influenced regional lithofacies development during the Tertiary (i.e., Hessami et al., 2001; Bahroudi and Koyi, 2004). 11. Conclusions Sedimentation in the Zagros Mountains experienced three phases during the Phanerozoic. The Persian Platform Phase (Phase-I) occurred during the latest Precambrian to Permian when the area encompassed a broad epeiric sea-type platform including at least seven microcontinents including Iran, Sanandaj — Sirjan, Lut, Turkey, Tibet, Afghanistan, and Arabia. Sedimentation patterns were primarily influenced by relative sea-level changes. The Arabian Platform Phase (Phase-II) began during the Permian when several microcontinents separated during the opening of the Neo-Tethys Ocean reducing the platform to its present aerial extent. Phase-II extended to the latest Cretaceous. Sedimentation during the phase-II was controlled by relative sea-level change as

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well as the formation of tectonically induced intrashelf depressions (Dezful Embayment and the Lorestan Basin). The Zagros Foreland Basin Phase (Phase-III) began in the earliest Tertiary during the initial stages of the collision of Arabia with Central Iran and continues to the present time. Collision margin-related processes influenced sedimentation during the Phase-III interval. Phanerozoic strata of the Zagros Mountains are characterized by distinct stratal packages separated by major unconformities forming twelve supersequences. They include: (1) Late Precambrian–Cambrian Hakhamanesh Supersequence, (2) Early– Late Ordovician Kourosh Supersequence, (3) Silurian Camboojiyeh Supersequence, (4) Devonian Darioush Supersequence, (5) Mississippian–Pennsylvanian Khashayar Supersequence, (6) Permian–Triassic Ashk Supersequence, (7) Jurassic Farhad Supersequence, (8) Early Cretaceous Mehrdad Supersequence, (9) Late Cretaceous Ardavan Supersequence, (10) Early Paleocene–Early Oligocene Sassan Supersequence, (11) Middle Oligocene–Late Miocene Ardeshir Supersequence, and (12) Late Miocene–Pleistocene Shapour Supersequence. Unconformities of the Zagros Mountains coincided with lowstands of second-order eustatic sea-level. Deposition of deepwater shales corresponded with major sea-level rise of the secondorder sea-level change. In addition, supersequences of the Zagros Mountains have similar timing to those from the North American Craton and the Russian Platform (Fig. 6) suggesting that these stratal packages are global. Therefore, tectonically induced local or regional events cannot be used to explain their existence. This investigation suggests that supersequences of the Zagros Mountains formed primarily by second-order eustatic sea-level changes. Tectonic activity influenced deposition of these strata packages through the formation of intrashelf basins during the latest Precambrian and Mesozoic, foreland basin development during the Tertiary, and uplift and erosion during late Tertiary and Quaternary. Acknowledgements The author is grateful constructive criticism by Lawrence R. Baria, Khalid Hessami, Rasoul Sorkhabi, Fred Read, and Thomas Wynn. The study was supported by Jackson State University and contributions from ExxonMobil Corporation. References Agard, P., Omrani, J., Jolivet, L., Mouthereau, F., 2005. Convergence history across Zagros (Iran): Constraints from collisional and earlier deformation. International Journal of Earth Science 94, 401–419. Ala, M.A., 1974. Salt diaprism in southern Iran. American Association of Petroleum Geologists Bulletin 58, 1758–1770. Alavi, M., 1980. Tectonostratigraphic evolution of the Zagrosides of Iran. Geology 8, 144–149. Alavi, M., 1994. Tectonics of the Zagros orogenic belt of Iran: New data and interpretations. Tectonophysics 229, 211–238. Alavi, M., 2004. Regional stratigraphy of the Zagros fold–thrust belt of Iran and its proforeland evolution. American Journal of Science 304, 1–20. Alsharhan, A.S., Kendall, C.G.St.C., 1986. Precambrian to Jurassic rocks of the Arabian Gulf and adjacent areas: their facies, depositional settings, and hydrocarbon habitat. American Association of Petroleum Geologists Bulletin 70, 977–1002.

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Asimov, I., 1981. Asimov's Guide to the Bible. Wings Publishing. 1296 p. Bahroudi, A., Koyi, H.A., 2004. Tectono-sedimentary framework of the Gachsaran Formation in the Zagros foreland basin. Marine and Petroleum Geology 21, 1295–1310. Berberian, M., King, G.C.P., 1981. Towards a paleogeography and tectonic evolution of Iran. Canadian Journal of Earth Science 18, 210–265. Beydoun, Z.R., 1991. Arabian plate hydrocarbon geology and potential — a plate tectonic approach. American Association of Petroleum Geologists, Studies in Geology 33. 77 p. Blanc, E.J.P., Allen, M.B., Inger, S., Hassani, H., 2003. Structural styles in the Zagros simple folded zone, Iran. Journal of Geological Society, London 160, 401–412. Bordenave, M.L., Burwood, R., 1989. Source rock distribution and maturation in the Zagros orogenic belt: provenances of the Asmari and Bangestan reservoir oil accumulation. Organic Geochemistry 16, 369–387. Bordenave, M.L., Hegre, J.A., 2005. The influence of tectonics on the entrapment of oil in the Dezful embayment, Zagros fold belt, Iran. Journal of Petroleum Geology 28, 339–368. Burgess, P.M., Gurnis, M., Moresi, L., 1997. Formation of sequences in the cratonic interior of North America by interaction between mantle, eustatic, and stratigraphic processes. Geological Society of America Bulletin 108, 1515–1535. Dashti, G.R., 1987. Evaluation of source rock potential as tectonic enhancemers in Lurestan area of Iran. In: Kumar, R., Dwivedi, P., Banerjie, V., Gupta, V. (Eds.), Petroleum Geochemistry and Exploration in the Afro-Asian region. Balkerma, Rotterdam, pp. 523–529. Davoudzadeh, M., Schmidt, K., 1984. A review of the Mesozoic paleogeographic evolution of Iran. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 168, 182–207. Davoudzadeh, M., Lensch, G., Weber-Dierenbach, K., 1986. Contribution to the paleogeography, stratigraphy and tectonics of the Infracambrian and Lower Paleozoic of Iran. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 172, 245–269. Dacoudzadeh, M., Weber-Diefenbach, K., 1987. Contribution to the paleogeography, stratigraphy and tectonics of the Upper Paleozoic of Iran. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 175, 121–146. Dercourt, J., et al., 1986. Geological evolution of the Tethys belt from the Atlantic to Pamirs since the Lias. Tectonophysics 123, 241–315. Dunnington, H.V., 1967. Stratigraphical distribution of oil fields in the Iraq– Iran–Arabia basins. Journal of the Institute of Petroleum 53, 129–161. Durant, W., 1954. The Story of Civilization. Our Oriental Heritage, vol. 1. Simon and Schuster, New York. 1049 p. Eriksson, P.G., Catuneanu, O., Nelson, D.R., Popa, M., 2005. Controls on Precambrian sea level change and sediment cyclicity. Sedimentary Geology 176, 43–65. Falcon, N.L., 1958. Position of oil fields of southwest Iran with respect to relevant sedimentary basins. In: Weeks, L.G. (Ed.), Habitat of Oil. Tulsa, Oklahoma, pp. 1279–1293. Fakhari, M.D., Axen, G.J., Horton, B.K., Hassanzadeh, J., Amini, A., 2008. Revised age of proximal deposits in the Zagros foreland basin and implications for Cenozoic evolution of the High Zagros. Tectonophysics 451, 170–185 (this volume). Gass, I.G., 1981. Pan African (Upper Proterozoic) plate tectonics of the Arabian–Nubian shield. In: Kroner, A. (Ed.), Precambrian plate tectonics. Elsevier, Amsterdam, pp. 387–405. Gill, W.D., Ala, M.A., 1972. Sedimetology of Gachsaran Formation (lower Fars Series), southwest Iran. American Association of Petroleum Geologists Bulletin 56, 1972–1974. Goff, J.C., Jones, R.W., Horbury, A.D., 1994. In: Al-Husseini, M.I. (Ed.), Cenozoic basin evolution of the northern part of the Arabian Plate and its control on Hydrocarbon habitat. The Middle East Petroleum Geoscience, vol. 1. Gulf Petrolink, Bahrain, pp. 402–412. Golonka, J., 2000. Cambrian–Neogen Plate Tectonic Maps. Wydawnictwo Uniwersytetu Jagiellońskiego, Kraków, Poland. 125 p. Grabowski, G.J., Norton, I.O., 1994. Tectonic controls on the stratigraphic architecture and hydrocarbon systems of the Arabian plat. In: Al-Husseini (Ed.), The Middle East Petroleum Geosciences, vol. 1. Gulf PetroLink, Manama, Bahrain, pp. 413–430.

70

E. Heydari / Tectonophysics 451 (2008) 56–70

Gradstein, F.M., Ogg, J.G., 2004. Geologic time scale 2004 — why, how, and where next! Lethaia 37, 175–181. Greenwood, W.R., Hadley, D.G., Anderson, R.E., Fleck, R.J., Schmidt, D.L., 1976. Late Proterozoic cratonization in southwestern Saudi Arabia. Journal of the Royal Society of London A280, 517–527. Gorin, G.E., Racz, L.G., Walter, W.R., 1982. Late Precambrian sediments of Huqf Group, Sultanate of Oman. American Association of Petroleum Geologist Bulleting 66, 2609–2627. Haq, B.U., Al-Qahtani, A.M., 2005. Phanerozoic cycles of sea-level change on the Arabian Platform. GeoArabia 10, 127–160. Harris, P.M., Saller, A.H., Simo, J.A., 1999. Advances in carbonate sequence stratigraphy: application to reservoirs, outcrops and models. SEPM Special Publication 63. 420 p. Hessami, K., Koyi, H.A., Talbot, C.J., Tabasi, H., Shabanian, E., 2001. Progressive unconformities within an evolving foreland fold–thrust belt, Zagros Mountains. Journal of the Geological Society, London 158, 969–981. Hessami, K., Milforoushan, F., Talbot, C.J., 2006. Active deformation within the Zagros Mountains deduced from GPS measurements. Journal of Geological Society, London 163, 143–148. Horton, B.K., Hassanzadeh, J., Stockli, D.F., Axen, G.H., Gillis, R.J., Guest, B., Amini, A., Fakhari, M., Zamanzadeh, S.M., Grove, M., 2008. Detrital zircon provenance of Neoproterozoic to Cenozoic deposits in Iran: Implications for chronostratigraphy and collisional tectonics. Tectonophysics 451, 97–122 (this volume). Husseini, M.I., 1989. Tectonic and deposition model of Late Precambrian– Cambrian Arabian and adjoining plates. American Association of petroleum Geologists Bulletin 73, 1117–1131. Insalaco, E., Virgone, A., Courme, B., Jérémie, Gaillot, Kamali, M., Moallemi, A., Lotfpour, M., Monibi, S., 2006. Upper Dalan Member and Kangan Formation between the Zagros Mountains and offshore Fars, Iran: depositional system, biostratigraphy and stratigraphic architecture. GeoArabia 11, 75–176. James, G.A., Wynd, J.G., 1965. Stratigraphic nomenclature of Iranian Oil Consortium agreement area. American Association of Petroleum Geologists Bulletin 49, 2183–2245. Kamali, M.R., Rezaee, M.R., 2003. Burial history reconstruction and thermal modeling at Kuh-e Mond, S.W. Iran. Journal of Petroleum Geology 26, 451–464. Kashfi, M.S., 1980. Stratigraphy and environmental sedimentology of lower Fars Group (Miocene), south-southwest Iran. The American Association of Petroleum Geologists Bulletin 64, 2095–2107. Kashfi, M.S., 1985. The pre-Zagros integrity of the Iranian platform. Journal of Petroleum Geology 8, 353–360. Kashfi, M.S., 1992. Geology of the Permian “super-giant” gas reservoirs in the greater Persian Gulf area. Journal of Petroleum Geology 15, 465–480. Kazmin, V.G., 1991. Collision and rifting in the Tethys Ocean: geodynamic implications. Tectonophysics 196, 371–384. Kent, P.E., 1958. Recent studies of south Persian salt plugs. American Association of Petroleum Geologists Bulletin 42, 2951–2972. Lasemi, Y., 2000. Facies, depositional environments, and sequence stratigraphy of Late Precambrian and Paleozoic rocks of Iran. Iranian Geological Survey and National Ore Exploration. 180 p (in Persian). Lees, G.M., 1933. Reservoir rocks of Persian oil fields. American Association of Petroleum Geologists Bulletin 17, 229–240. Loucks, R.G., Sarg, J.F., 1993. Carbonate Sequence, Recent Developments and Applications. American Association of Petroleum Geologists Bulletin, Memoir 57, 551 p. McGillivray, J.G., Husseini, M.I., 1992. The Paleozoic petroleum geology of central Arabia. American Association of Petroleum Geologists Bulletin 76, 1473–1490. McQuillan, H., 1991. The role of basement tectonics in the control of sedimentary facies, structural patterns and salt plug emplacements in the Zagros fold belt of southwest Iran. Journal of Southeast Asia Earth Science 5, 453–463. McQuarrie, N., 2004. Crustal scale geometry of the Zagros fold–thrust belt, Iran. Journal of Structural Geology 26, 519–535. Moghaddam, H.V., Seyafian, A., Taraneh, P., 2002. Biofacies and sequence stratigraphy of the Eocene succession, at Hamzeh–Ali area, north-central Zagros, Iran. Carbonates and Evaporites 17, 60–67.

Mohseni, H., Al-Aasm, I.S., 2004. Tempestite deposits on a storm-influenced carbonate ramp. An example from the Pabdeh Formation (Paleocene), Zagros Basin, SW Iran. Journal of Petroleum Geology 27, 163–178. Motiee, H., 1993. Zagros Stratigraphy. Iranian Geological Survey, Tehran, Iran. 536 p. (in Persian). Murris, R.J., 1980. Middle East: Stratigraphic evolution and oil habitat. American Association of Petroleum Geologists Bulletin 64, 597–618. Nadjafi, M., Mahboubi, A., Moussavi-Harami, Mirzaee, R., 2004. Depositional history and sequence stratigraphy of outcropping Tertiary carbonates in the Jahrum and Asmari carbonates, Shiraz area (SW Iran). Journal of Petroleum Geology 27, 179–190. Plint, A.G., Eyles, N., Eyles, C.H., Walker, R.G., 1992. Control on sea level change. In: Walker, R.G., James, N.P. (Eds.), facies models, response to sea level change. Geological Association of Canada, pp. 15–25. Ramezani, J., Tucker, R.D., 2003. The Saghand region, central Iran: U–Pb geochrobology, petrogenesis and implications for Gondwana tectonics. American Journal of Science 303, 622–665. Sepehr, M., Cosgrove, J.W., 2004. Structural framework of the Zagros Fold– Thrust belt, Iran. Marine and Petroleum Geology 21, 829–843. Sepehr, M., Cosgrove, J.W., 2005. Role of the Kazerun fault zone in the formation and deformation of the Zagros Fold–Thrust belt, Iran. Tectonic 24. doi:10.1029/2004TC001725. Setudehnia, A., 1978. The Mesozoic sequence in south-west Iran and adjacent areas. Journal of Petroleum Geology 1, 3–42. Seyrafian, A., 1998. Petrofacies analysis and depositional environment of the Jahrum Formation (Eocene), south-southwest of Burujen, Iran. Carbonates and Evaporites 13, 90–99. Seyrafian, A., 2000. Microfacies and depositional environments of the Asmari Formation, at Dehdez area (a correlation across central Zagros basin). Carbonates and Evaporites 15, 121–129. Sharland, P.R., Archer, R., Casey, D.M., Davies, R.B., Hall, S.H., Heward, A.P., Horbury, A.D., Simmon, M.D., 2001. Arabian Plate sequence stratigraphy. GeoArabia Special Publication, vol. 2. Oriental Press, Manama Bahrain. 371 p. Sherkati, S., Letouzey, J., 2004. Variation of structural style and basin evolution in the central Zagros (Izeh zone and Dezful Embayment), Iran. Marine and Petroleum Geology 21, 535–554. Sherkati, S., Letouzey, J., de Lamotte, D.F., 2006. Central Zagros Fold–thrust belt (Iran): New insights from seismic data, field observation, and sandbox modeling. Tectonics 25, 1–27. doi:10.1029/2004TC001766. Sloss, L.L., 1963. Sequences in cratonic interior of North America. Geological Society of America Bulletin 74, 93–114. Sloss, L.L., 1972. Synchrony of Phanerozoic sedimentary-tectonic events of the North American craton and the Russian Platform. 24th International Geological Congress, Sect. 6, 24–32. Stampfli, G., Marcoux, J., Baud, A., 1991. Tethyan margins in space and time. Palaeogeography, Palaeoclimatology, Palaeoecology 87, 373–409. Stöcklin, J., 1968. Structural history and tectonics of Iran: A review. American Association of Petroleum Geologists Bulletin 52, 1229–1258. Szabo, F., Kheradpir, A., 1978. Permian and Triassic stratigraphy, Zagros basin, south-west Iran. Journal of Petroleum Geology 1–2, 57–82. Vail, P.R., Mitchem, R.M., Thompson, S., 1977. Seismic stratigraphy and global change of sea-level. In: Payton, C.E. (ed.), Seismic stratigraphy-applications to hydrocarbon exploration, American Association of Petroleum Geologists, Memoir 26, 83–97. Vaziri-Moghaddam, H., Safari, A., Taheri, A., 2005. Microfacies, paleoenvironments and sequence stratigraphy of the Tarbur Formation in Kherameh area, SW Iran. Carbonates and Evaporites 20, 131–137. Weidlich, O., Bernecker, M., 2003. Supersequence and composite sequence carbonate platform growth: Permian and Triassic outcrop data of the Arabian platform and Neo-Tethys. Sedimentary Geology 158, 87–116. Wilgus, C.K., Hastings, B.S., Posamentier, H., Van Wagoner, J., Ross, C.A., Kendall, C.G.St.C., 1988. Sea-Level Changes: An integrated Approach. SEPM Special Publication 42. Ziegler, M.A., 2001. Late Permian to Holocene paleofacies evolution of the Arabian Plate and its hydrocarbon occurrences. GeoArabia 6, 445–504.