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asin and the coeval dolomite (Soltanieh) in Central Iran and the Alborz. Thus, these tectonic lines appear to have been in existence at least since late Precambrian time (Fig. 10). The trend of the Main Zagros and High- Zagros faults is parallel to the northwest-southeast leftlateral Najd wrench fault system (Brown 1972; Moore 1979), and like them might have developed during the Najd orogeny (about 560 or 540 Ma). During Asir (1050 Ma), Hijaz or Pan African (Aqiq (960 Ma), Ranyah (800 Ma), Yafikh (650-600 and Bishah (550 Ma) orogenies, the rocks of the Arabian shield were folded and faulted about north-south axes. These north-south trends were later cross-cut by the Najd northwest-southeast left-lateral wrench fault system (540-510 Ma according to Greenwood et al. 1976, or 560 Ma according to Schmidt et al. 1978), which affected large parts of the eastern and northern Arabian Shield. Displacements of more than 100 km took place in the northwestern part of the fault zone (Schmidt et al. 1973; Greenwood etal. 1976). The northwest-southeast Najd fault system along the northeastern Arabian shelf was responsible for rifting and subsidence of the Arabian-Iranian block during the Late Precambrian, Permian, and Late Triassic - Jurassic extensional periods. The northeastern sets of these faults presumably behaved as multi-role faults at various times: as wrench faults (during the Najd orogeny), normal faults (Late Precambrian, Permian, Late Triassic - Jurassic, Cretaceous), and thrust faults (Late Cretaceous, Plio-Pleistocene, and Recent; Berberian 1979). BERBERIAN AND KING 229 Arabia (Huqf Group; Murris 1978) to the Alborz mountains in the north (Fig. 10; Table 1) and to Central Afghanistan (Lower Bedak Dolomite (Lapparent 1977; Termier and Termier 1977)), and Pakistan (Penjab Saline Series or Salt Range Formation) in the east. This and the Lower Cambrian shallow sea deposits of the Zaigun-Lalun red arkosic sandstone - shale Formation in Zagros (Setudehnia 1975), Central Iran (Huckriede et al. 1962), and Alborz (Assereto 1963) and its (possibly time transgressive) equivalents (Table 1), the Saq Sandstone in Arabia (Steineke et al. 1958; Powers et al. 1966; Powers 1968), Quwiera Sandstone in Jordan (Quennell 1951; Daniel 1963), Sadan, Kaplander, Cardak Yalu-Calaktepe in southeastern Turkey (Ketin 1966; Ala and Moss 1979), Tor Petaw Sandstone in Zargaran, central Afghanistan (Lapparent 1977), and the Purple Sandstone and Shale in the Salt Range of Pakistan (Cotter and Khan 1956), suggest that at least from late Precambrian to late Paleozoic times, Iran was a part of Gondwanaland and possibly an extension of the Afro-Arabian continental platform (Stocklin 1968a,b, 1973, 1974, 1977; Nabavi 1976; Berberian 1976a; Kashfi 1976; see also Figs. 3 and 10). The clastic deposits were mainly provided by the Precambrian uplifted granitic and metamorphic highlands in Arabia, Iran, and other nearby continental areas. In late Early Cambrian time, widespread dolomite, marl, and shale with salt pseudomorphs were deposited in a shallow, shelf-sea (Member 1 of the Mila Formation) in the Alborz mountains (Stocklin et al. 1964; Kushan 1973, 1978), in Central Iran (Ruttner et al. 1968), in the Zagros mountains (Harrison 1930; King 1937; Setudehnia 1975), in the Salt Range of Pakistan (Schindewolf and Seilacher 1955), and in the Himalayas (Reed 1910). The disappearance of the salt pseudo- I1.2 PALEOZOIC (570--230 MA) ll.2a---Gondwanian Iran (Zagros, Central lran (including Lut), and Alborz) Following the Late Precambrian (Katangan) orogeny and the consolidation of the basement, the Precambrian morphs in Middle Cambrian time indicates a steady craton oflran, Pakistan, central Afghanistan, southeastern Turkey, and Arabia became a relatively stable continental platform with epicontinental shelf deposits (mainly clastics) and lack of major magmatism or folding. This regime presumably lasted until late Paleozoic time, although there was some epeirogenic movements in the Late Silurian - Early Devonian time (Table 1; Section 11.2.1). The Upper Precambrian Hormoz Salt and its nonevaporitic equivalents (Soltanieh Stromatolite Dolomite in Iran (Stocldin et al. 1964), and Jubaylah Group in Arabia (Brown and Jackson 1979)) are found from subsidence of the Cambrian sedimentary basin. By the beginning of the Late Cambrian Epoch, a fully marine environment with the deposition of fossiliferous limestones prevailed (Members 2 to 4 of the Mila Formation, Middle to Upper Cambrian). During Early Ordovician time (Member 5 of the Mila Formation) the sediments changed from marine carbonates to quartzitic sandstone, suggesting the regression of the sea (Table 1). The Cambrian of Iran, Pakistan, and north India is marked by fossils of the Western Pacific (Redlichian) province (Kobayashi 1972). Trilobite fauna indicate that during the Middle and Late Cambrian Epochs marine commumetamorphosed basement rocks, have been found as erratic rock fragments brought up by the Hormoz salt domes in the Zagros belt. The magmatic activity in the eastern part of Central Iran along the Chapedony and Posht-e-Badam faults seems to be related to the Precarnbrian island arc cratonization of Iranian basement. 7. Geosynclinal areas in the north. Principal sources of data: Stocklin (1968b); Keller and Predtechensky (1968); Kent (1970); Brown (1972); Setudehnia Berberian (1976a,b); Huber (1978); Berberian and Berberian (1980); Berberian (198 I); and all available data from the cal and Mineral Survey of Iran to 1980. Lambert Conformal Conic Projection.
230 CAN. J. EARTH SCI. VOL. 18, 1981 nication existed between the Eastern Asiatic (Chinese) region and Iran (Kushan 1973, 1978; Wolfart 1967; Kobayashi 1972). The Iranian Upper Precambrian Cambrian sedimentary rocks, which are widespread and dominant in south, central, and north Iran, apparently pinch out northward in the northern Alborz mountains. During early Ordovician time, Arabia (Tabuk Formation (Powers 1968)), the Zagros (Zard Kuh Formation (Setudehni 1975; Harrison 1930)), and parts of Central Iran and Alborz (Lashkarak Formation (Gansser and Huber 1962)), were covered by marine graptolitebearing shale deposits (Table 1). Parts of east Iran were covered by the marine carbonates, marls, and shales of the Shirgest Formation (Lower to Middle Ordovician; Ruttner et al. 1968). The rock sequence deposited during the Paleozoic Era in Iran (Table 1) has all of the characteristics of a true platform cover (predominance of pre-Permian terrigenous clastic deposits and Permian carbonates). They are epicontinental deposits and contain important sedimentary gaps and thickness and facies changes indicating repeated epeirogenic movements or possibly eustatic sea-level changes. The Paleozoic platform deposits of Central Iran, which generally lack major magmatism and metamorphism, were presumably separated by some rift-like narrow mobile belts (Haghipour and Sabzehei 1975). These mobile belts, like the Sanandaj-Sirjan (intracontinental) rifted basin (Fig. 1), were presumably developed between platform blocks by fragmentation of the platform along the major old active faults and are characterized by extensive alkaline continental volcanic activity and increased subsidence at the end of the Paleozoic Era (Figs. 11 and 12). H.2a.l--Paleozoic volcanic activity Following the Late Precambrian alkali acid volcanism (discussed in Section II. 1; see also Fig. 10), some basic to intermediate volcanic rocks appeared in Central Iran during the Paleozoic Era. Three ’Paleozoic extensional phases’ are identified within the continental crust of Iran, which are indicated by tensional faulting, sedimentation, and volcanism (Table 1). There is evidence for subduction to explain these volcanics. Extension and uplift appear to follow each other sequentially. Folding or other types of compressional deformation do not occur except in the Late Paleozoic (Hercynian) phase. H.2a.l.l--Late Precambrian to Middle Silurian extensionalphase--The first Early Paleozoic volcanic activity accompanied normal faulting and stretching of the continental crust. The start of this phase is marked by Late Precambrian alkali acid volcanism, with some basic volcanism (Section II. 1; and Fig. 10), and later diabase in the Soltanieh Dolomite Formation (see Table 1) in the north Tabas area (Ruttner et al. 1968). An ignimbritic sequence about 400 m thick (Mohamadabad ignimbrite) overlies the late Precambrian Gorgan schists, and is underlain by the Cambrian Lalun sandstone in the Gorgan area of the northern Alborz, southeast of the Caspian Sea (Jenny 1977). The Cambrian basic volcanics occur near the base of the Zaigun Formation in the Taleqan area and in the Vatan Formation of the Djam area (Annells et al. 1975; Alavi-Naini 1972); diabases occur in the Lalun-Zaigun Formation in north Tabas and Avaj (Ruttner et al. 1968; Bolourchi 1977), and basic volcanics (olivine basalt, olivine-augitehornblende dolerite) in the Kalshaneh Formation of the Tabas region (Ruttner et al. 1968). Ordovician dacite and andesite volcanics appear in the Maku region of northwestern Iran (Berberian 1976c, 1977b; Berberian and Hamdi 1977). About 200 m of thick basic (spilitic) volcanics appears in the Ordovician Ghelli Formation in the Ghelli region, northeastern Iran (Afshar-Harb 1979). Some basic volcanics are also observed below the Ordovician limestone of the Tatavrud area of Talesh mountain, southwest Caspian Sea (Davies et al. 1972; Clark et al. 1975). Ordovician olivine basalt, quartz keratophyre, trachyandesite, and olivine andesite are reported from the northern Tabas region of Central Iran (Ruttner et al. 1968). The Soltan Maidan basalts (250- 700 m thick) are developed above the Ordovician and below the Devonian beds in the Gorgan area of northern Alborz mountains, and are probably Silurian in age (Jenny 1977). Silurian spilitic to basaltic (with some andesitic) lavas and tuffs occur beneath the red Orthoceras limestone in the Kolur area, southwest Caspian Sea (Davies et al. 1972; Clark et al. 1975). There are also Silurian volcanics of the Niur Formation (olivine basalt at the base of the formation in the northern part of the Shotori area (Ruttner et al. 1968), basic volcanics at Ghelli and Robat-e-Gharabil area, northeastern Iran (Afshar-Harb 1979), dolerite and basalt at the base of the formation in the Soh area (Zahedi 1973), trachyandesite in the Torud area (Hushmandzadeh et al. 1978), and trachyandesite at the top of the formation in the Djam area (Alavi-Naini 1972)). Ordovician volcanics (Chalki) have been reported in one section from the western Zagros in northern Iraq. The Chalki volcanics occur within and towards the top of the Pirispiki red beds (Bellen et al. 1959). Unlike the Upper Precambrian thick alkali volcanics in Central Iran and the Upper Paleozoic volcanics along the Sanandaj-Sirjan belt, the Iranian Paleozoic volcanic rocks form a few thin layers interbedded with sediments (Table 1). ll.2a. 1.2--Early Devonian and Carboniferous extensional phase--The known volcanic activity of this phase is represented by the Lower Devonian basic volcanics in the Qazvin area (Annels et al. 1975), and the 150m thick Upper Devonian basalts in Member A of the
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