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Home , Geosyncline, Iranian Plateau, Zagros Mountains

and structural evolution of the Zagros geosyncline, southwestern

MANSOUR S. KASHFI Ultramar Iran Oil Company, P.O. Box 14-1899, Tehran, Iran

ABSTRACT STRATIGRAPHY AND the sediments are terrigenous- SEDIMENTATION OF THE detrital sediments, whereas from Permian The Zagros geosyncline has been a ZAGROS GEOSYNCLINE to Late time, carbonate deposits geologic unit extending from the Turkish dominate the sedimentation (Fig. 3). Over- frontier, north of Mosul, to the entrance of Lees (1933) believed that sediments were lying this carbonate sequence are detrital the at least since the beginning deposited continuously in a geosyncline in flysch-type sediments represented by chalk, of Paleozoic time. The the southwestern of Iran at least marl, and that were deposited can be interpreted as being the final product from late Paleozoic to Pliocene time. Lees from Late Cretaceous to time. of a geosynclinal cycle. In contrast, the evi- described a rather incomplete history of The seas climaxed during the dence for a plate tectonic history in this re- sedimentation from Cambrian to Permian Cretaceous Period. The great central belt of gion is too fragmentary to be meaningful at time and a continuous sedimentary record the Tethys, extending from to India, this time. from Permian to late time. During was very active in Mesozoic time. The Paleozoic time, the Zagros region was af- northern boundary of the Tethys extended INTRODUCTION fected only by epeirogenic movements, and onto the Russian platform and westward to there is no evidence of folding. In late the shelf-sea areas just north of the Black The formed as a result of Paleozoic time, however, the sedimentation Sea. The Tethys extended eastward through tectonic forces that folded and faulted the changed from terrigenous clastic to mainly the to India; the southern two bounding ranges (Fig. 1). The carbonate. Therefore, the major portion of shore of the central Tethys Sea reached the Mountains strike eastward and are folded and thrust toward the sunken foreland of the Caspian Sea; the Zagros Mountains oc- cupy the western part of Iran and portions of and extend from eastern Turkey to Bandar Abbas at the edge of the Persian Gulf. The structural pattern and tectonic behavior of the Zagros geosyncline are remarkably similar to those of the miogeosynclinal part of the Appalachian geosyncline, except that the Zagros Mountains are younger and comparatively uneroded. The Zagros Mountains rise gradually northeastward from an unfolded shelf, extend through a belt of intact anti- clines and into a thrust belt and imbricated zone, and merge into an intru- sive and metamorphic zone near Hamedan (Figs. 1,2). Geosynclinal conditions existed here from Cambrian into time and were part of the main Tethys geosynclinal system. At least as early as time, two tectonic zones in the Zagros geosyncline were becoming differentiated, as was a much wider platform zone in Arabia. The Zagros, , and are the final peripheral products of the vast Tethyan mobile belts of subsidence. Tectonic activity still continues along this line of crustal weakness, as evidenced by frequent . The main purpose of this paper is to show that the classical hypothesis of geo- synclines explains the Zagros Mountains as being originally a mobile geosyncline of predominantly compressional nature.

Geological Society of America Bulletin, v. 87, p. 1486-1490, 3 figs., October 1976, Doc. no. 61014.

1486

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Figure 2. Regional cross section of major structural zones of the Zagros geosyncline.

Ethiopian shield and central Saudi Arabia. mobile belt and extends eastward to an area trusion did help induce thrusting in the The transgressive seas of Oligocene and of metamorphic and igneous rocks (Fig. 1). eastern half of the Zagros geosyncline. A early time produced the Asmari This eastern part of the geosyncline appar- huge sheet of Cretaceous limestone was Formation, a cliff-forming limestone and a ently was developed during the Late Cre- thrust toward the southwest near - well-known oil reservoir (Kashfi, 1974). taceous , and the western part was shah, probably by the intrusion. The upper Tertiary and Quaternary beds formed in later Tertiary time, as indicated Oberlander (1965) believed that the are dominantly terrigenous detrital rock, by the rock types and more intensive de- thrust belts in the eastern part of the particularly coarse-grained sandstone and formations in the eastern part of the geosyncline originated by the shearing of conglomerate. geosyncline. Thus, some workers refer to folds similar in magnitude to shearing in Late Cretaceous mountain building these two zones as the older and younger folds in the western part of the geosyncline. within the Zagros geosyncline began for the Zagros geosynclines, respectively. Several Those in the eastern part, however, proba- first time to influence sedimentation. The periods of compressive stress from the bly are somewhat older and have been bro- carbonate succession of Mesozoic time was northeast in late Mesozoic and Tertiary ken and were themselves folded by the followed from the Himalayas to the Alps by time produced the structure of the Zagros newer compressive stress from the north- an accumulation of flysch layers of Late Mountains. The gradual southwestward east; this new compression produced the Cretaceous age, with an abrupt return to decrease in deformation is illustrated in younger structures in the western part of carbonate deposition prior to Cenozoic up- Figure 2. the geosyncline (Table 1). The faults in the lift. As a result, sedimentary facies in the The western part of the Zagros geo- extreme eastern part of the geosyncline are different sectors of the geosyncline are not syncline is dominated by unbroken, asym- high-angle thrusts and gradually become completely synchronous. metric, doubly plunging folds — large an- low-angle thrusts toward the southwest; all Lagoonal and transitional conditions led ticlines and synclines similar to those of the of the thrust planes dip toward the north- to the deposition of the Fars Group, which French Jura but on a larger scale. There are east. The structures were most likely not ranges from shale, marl, salt, anhydrite, also some subordinate thrust faults that ap- controlled by the basement. The frontal and to sandstone and finally to pear to have developed from simple folds. faults of the eastern half of the geosyncline conglomerate of the Bakhtiari Formation, Anticlines generally have the steeper flank are clearly parallel to the structural trend of which was deposited during early middle on the southwest and have slightly sheared the western part of the geosyncline. The Miocene to early Pliocene time. Massive crests. These young folds also were pro- general strike of the entire belt is northwest. conglomerate of the Bakhtiari Formation tected during deformation by the covering The first major deformation in the Zag- overlies the formations below with marked marl and evaporite beds of the Gachsaran ros geosyncline took place in Late Creta- angular unconformity. The unconformity Formation of the lower Fars Group, which and the nature of the overlying deposits in- acted to transfer the orogenic pressure over dicate a violent upheaval in late Pliocene the substratum of the Asmari Formation; TABLE 1. SUMMARY OF TECTONIC time. The coarse-grained sandstone layers thus, the anticlines that were formed in the EVENTS IN THE ZAGROS of the Bakhtiari Formation indicate rapid upper Tertiary terrigenous clastic layers are GEOSYNCLINE emergence and increase of relief at that disharmonic with those of the underlying time. The pebbly units of the Bakhtiari geosynclinal marine sediments (Dun- Western zone Eastern zone Formation, which contain carbonate, chert nington, 1967). Cenozoic Orogeny: uplift, Orogeny: second fragments, and metamorphic debris, might The eastern part of the Zagros geo- folding — cycle of folding have been derived from the crystalline zone syncline is characterized by northeast- latest phase and thrust far northeast of the geosyncline. dipping thrust faults. Paleozoic rocks have of the Alpine faulting been brought to the surface by these orogeny TECTONIC HISTORY OF THE thrusts. Metamorphic rocks, Paleozoic and Mesozoic Subsidence with Orogeny: uplift, ZAGROS GEOSYNCLINE Mesozoic in age, occupy much of the accumulation folding, abrupt northeastern zone of the overthrusting; in of marine facies and The Zagros Mountains can be divided places, they are thrust southwestward over sediments thickness longitudinally into two zones. The south- younger rocks. changes, uncon- western part is primarily a zone of strong According to Oberlander (1965), the formities and folding that forms the shelf area to the Hamedan crystalline zone is the protaxial metamorphism west; it is referred to as the western part of zone of the Zagros orogenic system. The Paleozoic Epeirogeny: shallow-water sedi- the Zagros geosyncline. The thrust zone oc- origin and time of emplacement of this in- ments, absence of any major angu- cupies the northeastern part of the Zagros trusive mass are not clearly known, but in- lar unconformity

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was characteristic of a platform facies, Formation of Turkey, the Quweira ZAGROS GEOSYNCLINE being composed mainly of shallow-water Sandstone of Jordan, and the Saq carbonate deposits. The absence of major Sandstone of Saudi Arabia. The Lalun PERIOD SERIES FORMATION angular unconformities in Cambrian Sandstone is also equivalent to a nearly through rocks in the western part identical unit, the "Purple Shales," of Paki- BAKHTIARI :„ of Iran supports this view. Continuous sub- stan and the central part of the Indian PLIOCENE " - • ' O * 4 sidence during Mesozoic and Tertiary time shield (Meyerhoff and Meyerhoff, 1972, A'GHA :jARI in the western part of the Zagros 1974). Furthermore, Stocklin discovered > geosyncline contrasts sharply with the east- widespread Cambrian beds with trilobite OC MIOCENE -MISHAN— — ern part, which is characterized by abrupt index fossils in Iran, which is another indic- < facies and thickness changes, unconformi- ation of the tectonic unity of this region h- GACHSARAN ties, and metamorphism. The final marine from at least early Paleozoic time. tz invasion took place in late Miocene time, The argument against plate tectonics in Lj ASM ARI but this submergence was followed by a this region is further substantiated by the I- OLIGOCENE sharp, younger uplift that was accompanied observation of Stocklin (1968a) of EOCENE by folding in the western part of the PABDEH > JAHRUM similarities between what he called the In- PALEOCENE geosyncline. The climax of uplift and fracambrian (Eocambrian) Hormuz Salt of orogeny occurred in early Pliocene time, Iran and salt beds of the same age elsewhere which is the latest phase of the Alpine in the . The late Precambrian orogeny. and Cambrian seas covered a major portion Upper Pliocene conglomerate apparently of the and Persian Gulf area, was deposited in conjunction with the most which was a primary source of carbonate intensive mountain building in Zagros sediments. The most important salt deposit geosynclinal history. The conglomerate is of Cambrian age is located in south and relatively undeformed compared to the un- east-central Iran and in the greater Persian derlying lower Pliocene rocks. Quaternary Gulf area, with a significant portion in east- rocks lie unconformably on upper Pliocene ern Arabia (Mina and others, 1967; rocks. Stocklin, 1968a, 1968b). This widespread salt distribution indicates basin continuity ZAGROS GEOSYNCLINE AND across the alleged subduction zone pro- PLATE TECTONICS posed in plate tectonics. Stocklin pointed out the presence of the The Zagros geosyncline is interpreted by transitional beds of Permian many workers in terms of plate tectonics; and Triassic age in the northern part of Iran they disregard many years of thorough as well as in the south-southwestern part of geologic investigations in order to explain Iran. He also noted that the Devonian Sys- the of this part of the world. They tem in western Iran is represented by a thin NEYRIZ insist that the present Zagros Mountains sandstone and shale facies and can be corre- V) X are the result of collision between lated closely with Devonian strata of cen- < KHANEH KAT and . Such an argument carries little tral Saudi Arabia. The upper cr weight, however, when all the geologic data beds of the Zagros geosyncline area have are considered. These data demonstrate also been correlated with similar facies in that the concept of plate tectonics is com- central Saudi Arabia. Most fossils from the Figure 3. Generalized stratigraphic chart. pletely in error in the Tethys region. Devonian System of western Iran have been ceous time when the eastern part of the The advocates of plate tectonics insist found in the USSR (for example, Spirifer geosyncline was folded and later thrust that Africa traveled about 1,500 to 2,000 anossofi). Most Carboniferous fossils of southwestward. Generally, Paleozoic and, km since Jurassic time to collide with Asia. western Iran are similar to Carboniferous in some places, lower Mesozoic rocks were Detailed stratigraphic studies by Falcon fossils of the Urals, Turkey, and the thrust southwestward over Tertiary and (1967), Stocklin (1968b), Kent (1969), Himalayas; for example, Spirifer uppper Mesozoic folded sedimentary rocks. Kamen-Kaye (1970), and Meyerhoff and mosquensis, which is a Carboniferous The deepest part of the geosyncline during Meyerhoff (1972, 1974), however, demon- index fossil of the USSR, is found widely in Mesozoic and the early part of Tertiary strate that some stratigraphic units of middle and upper Carboniferous rocks of time was in this area, with flysch-type de- Early Cambrian to Middle Triassic age in Iran (Clapp, 1940). posits derived from rising adjacent lands. Arabia and northeastern Africa can be The advocates of plate tectonics believe The deposits were gradually shifted south- traced through Iraq, Iran, and into Soviet that India joined Asia in a cratonic collision westward and finally reached the modern . The continuity of certain in middle Cenozoic time. Such a conclusion Persian Gulf geosyncline (Kamen-Kaye, stratigraphic units between Turkey and is unwarranted, because they have ignored 1970). The Late Cretaceous orogenic Egypt is established; furthermore, some the fact that comprehensive geologic inves- episode resulted in a major unconformity in stratigraphic units in northern Turkey have tigations reveal that India has been part of at least the northeast part of the Zagros been correlated with units in the southern Asia at least since Proterozoic time. The In- geosyncline. In the folded zone or western Taurus Range (Ilhan, 1967; Meyerhoff and dian saline series (known as the Punjah part of the geosyncline, dominantly marine Meyerhoff, 1972, 1974). Saline) can be correlated with the salt series sediments were laid down conformably The basal unit of the Cambrian System in of Hormuz Island of the Persian Gulf area through Miocene time. Iran is a shallow-water, cross-bedded, pur- and Iran (Ahmed, 1969). A trilobite zone According to Stocklin (1968b), tectonic ple, arkosic sandstone — the Lalun (Redlichia) extends from western India into activity from Precambrian to Triassic time Sandstone. Stocklin (1968b) was able to central China (Misch, 1946; Meyerhoff and was negligible; deposition during this time correlate this sandstone with the Sadan Meyerhoff, 1972, 1974). Some strati-

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graphic units of Paleozoic age in crust and the accumulation of sediments in CONCLUSION and western China are correlated across the the subsiding trough, coupled with simple Himalayas to northern India and westward isostatic balance and compressive move- Africa, Arabia, and India have been inte- to the entrance of the Persian Gulf ments, were sufficient to produce the Zag- gral parts of and Asia since late Pro- (Meyerhoff and Meyerhoff, 1972, 1974; ros geosyncline. There is no need to call for terozoic time. There were no plate tectonic Chang and Cheng, 1973). collision of Africa with Asia to produce it. collisions in the Tethys area after at least The warm-water and tropical Tethyan Great emphasis has been placed by "drift- late Proterozoic and possibly earlier time. facies of Jurassic to middle Cenozoic age in ers" on the association of colored mélange The preferred mechanism to explain the southern and southeastern India indicate and as indications of a Zagros geosyncline and other Tethyan that India did not move from an Antarctic subduction zone in the Zagros region. How- ranges is represented by the geosynclinal polar realm in Jurassic time to the Tethyan ever, there are colored mélange assemblages theory as expounded by Aubouin (1965) region in middle Tertiary time (Meyerhoff of larger scale in many other parts of Iran. and others. and Meyerhoff, 1974). Mantura (1972) has Colored mélange has been reported exten- questioned how India could have subsided sively in Sabzevar and Nain in east-central ACKNOWLEDGMENTS beneath Asia, almost 30 km below the Iran and in the Mokran Ranges in southeast- lithosphere, in order to lift the Himalayan ern Iran. Aubouin (1965) described radiola- I thank J. Stocklin of the Geological Sur- and Tibetan thousands of metres rite formations in all the Alpine chains of the vey of Iran and J. R. Fasbender and R. F. yet did not melt at such depths. Of equal ; he further pointed out Hulstrand of the Iran Nippon importance is the work by Wilson (1969), that radiolarite is uniquely characteristic of Company for reading the manuscript. I which demonstrates structural continuity geosynclinal chains. Therefore, before leap- thank J. Glance of Oil Services Company of between Arabia, , and western ing to a conclusion from a small body of col- Iran for stimulating discussions. India since late Paleozoic time. ored mélange in western Iran, the supporters Tectonic activity took place in Late of plate tectonics should ponder the geologic REFERENCES CITED Triassic time when the Zagros geosyncline significance of the many Iranian mélange as- began to assume its modern character; the semblages. As for colored mélange, de Sitter Ahmed, S. S., 1969, Tertiary geology of south same tectonic phase with similar charac- (1959) wrote that geosynclinal development Mokran, Baluchistan, west Pakistan: Am. Assoc. Petroleum Geologists Bull., v. 53, teristics was recognized in the by passes through a phase in which a barrier is formed between the geosynclinal trough and p. 1480-1499. Khain and Milanovsky (1963). Aubouin, Jean, 1965, Geosynclines: Amsterdam, It appears that plate tectonicists consider the open ocean basin; this barrier in Zagros Elsevier Pub. Co., p. 115-130. only one aspect of tectonics, the horizontal geosynclinal history is the radiolarite and Burk, C. A., 1968, Buried ridges within continen- motion of the lithosphere. Therefore, they colored mélange zone, which becomes a zone tal margins: New York Acad. Sci. Trans., insist that Africa moved hundreds or of high-angle thrust faults. A similar phe- ser. 2, v. 30, p. 397-409. thousands of kilometres and bent down- nomenon occurs in the central zone of the Caire, A., 1970, Sicily in its Mediterranean set- ward into a subduction zone, causing uplift Piedmont province of the Appalachian ting, in Geology and history of Sicily: Libya of the Zagros region. Arguments by Man- geosyncline. Furthermore, de Sitter believed Petroleum Exploration Soc., 12th ann. field conf., p. 147-170. tura (1972) challenge the plausibility of this that the incompetent radiolarite acts as a lu- bricant for the movement of thrusts over it. Chang Cheng-fa and Cheng Hsi-Lau, 1973, unscientific speculation. He questioned Some tectonic features of the Mt. Jolmo how Africa could have moved eastward De Sitter's observations pose potential limi- Lungma (Everest) area, southern , away from the Mid-Atlantic Ridge, yet tations on the colored mélange as being an China: Sci. Sinica, v. 16, p. 257-265. simultaneously moved westward away indication of subduction, as proposed by Clapp, G. F., 1940, Geology of eastern Iran: from the Mid- Ridge, while at some workers for southwestern Iran. Geol. Soc. America Bull., v. 51, p. 1-102. the same time Africa had to rotate coun- Advocates of plate tectonics claim that de Sitter, L. U., 1959, Structural geology: New terclockwise relative to the Tethys on the deep earthquakes are concentrated only in York, McGraw-Hill Book Co., p. 480- 481. north in order to collide with and areas of crustal convergence at subduction produce the Alps and the Zagros zones and are absent within existing Dewey, J. F., Pitman, W. C., Ryan, W. B., and Mountains. Maiitura also questioned how Bonnin, Jean, 1973, Plate tectonics and the tectonic plates. Major earthquakes with evolution of the Alpine system: Geol. Soc. the Arabian foreland, with the powerful deep foci, however, are recognized in east- America Bull., v. 84, p. 3137-3180. support of Africa from behind, could form southeastern Iran, far from the proposed Dunnington, H. V., 1967, Stratigraphical dis- the relatively small Zagros geosyncline, yet subduction zone. tribution of oil fields in the Iraq-Iran-Arabia at the same time, tiny and unsupported Another important question that must be basin: Inst. Petroleum Jour., v. 53, India could collide with Asia in such a reconciled is, how does plate tectonics ac- p. 129-153. manner as to raise the Himalayas. Geology, count for the presence of the Alborz Falcon, N. L., 1967, Equal areas of geophysics, and oceanography provide a several hundred kilometres and Laurasia: Nature, v. 213, p. 580—581. large body of evidence that leads me to be- northeast of the Zagros geosyncline? Is this Gill, W. D., 1965, The Mediterranean basin, in lieve that Africa and Eurasia have been in Salt basins around Africa: London, Inst. Pe- another subduction zone? Recently, Dewey troleum, p. 101-111. fixed position since the beginning of and others (1973) proposed the idea of Ilhan, E., 1967, Toros-Zagros folding and its re- Paleozoic time (Klemme, 1958; Gill, 1965; "microplates" and tried to explain the re- lation to Middle East oil fields: Am. Assoc. Kent, 1969; Caire, 1970; Maxwell, 1970; gional and the Middle East Petroleum Geologists Bull., v. 51, p. 651 — Sander, 1970; Triimpy, 1971; Meyerhoff by moving these speculated microplates 667. and Meyerhoff, 1972, 1974). around during each geologic period. They Kamen-Kaye, M., 1970, Geology and pro- The geosynclinal theory (Lees, 1933; failed, however, to explain the mechanism ductivity of Persian Gulf synclinorium: Am. Clapp, 1940; Aubouin, 1965; Falcon, for these quick motions of microplates in Assoc. Petroleum Geologists Bull., v. 54, p. 2371-2394. 1967; Stocklin, 1968b; Kamen-Kaye, such a limited area. It is worth mentioning Kashfi, M. S., 1974, A brief study of reservoir that Burk (1968) raised the question of the 1970; Meyerhoff and Meyerhoff, 1972, rocks wetability of the Iranian oil fields: 1974) provides the means for producing the relation of convection currents in the man- Energy Sources Jour., v. 1, p. 316—317. Zagros geosyncline without invoking plate tle to the young vertical movements that Kent, P. E., 1969, The geological framework of tectonics. The simple subsidence of the produced the Iranian plateau. petroleum exploration in Europe and North

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Africa and the implications of continental Meyerhoff, A. A., and Meyerhoff, H. A., 1972, conf., p. 43-132. drift hypothesis, in The exploration for pe- "The new global tectonics," major inconsis- Stöcklin, J., 1968a, Salt deposits of the Middle troleum in Europe and North Africa: Lon- tencies: Am. Assoc. Petroleum Geologists East, in Mattox, R. B., ed., Saline deposits: don, Inst. Petroleum, p. 3-17. Bull., v. 56, p. 269-336. Geol. Soc. America Spec. Paper 88, Khain, V. E., and Milanovsky, E. E., 1963, Struc- 1974, Tests of plate tectonics, in Kahle, C. p. 157-181. ture tectonique du Coucase d'après les don- F., ed., Plate tectonics — Assessments and 1968b, Structural history and tectonics of nées modernes, in Livre à la memoire du reassessments: Am. Assoc. Petroleum Iran: Am. Assoc. Petroleum Geologists prof. P. Fallot, Tome II: Soc. Géol. France Geologists Mem. 23, p. 43-145. Bull., v. 52, p. 1229-1258. Mém., p. 663-703. Mina, P., Razaghnia, M. T., and Paran, Y., 1967, Triimpy, R., 1971, Stratigraphy in mountain Klemme, H. D., 1958, Regional geology of Geological and geophysical studies and ex- belts: Geol. Soc. London Quart. Jour, v. circum-Mediterranean region: Am. Assoc. ploratory drilling of the Iranian continental 126, pt. 3, p. 293-318. Petroleum Geologists Bull., v. 42, p. 477- shelf, Persian Gulf: World Petroleum Wilson, H. H., 1969, Late Cretaceous and 512. Cong., 7th, Mexico, Proc., v. 2, p. 870- eugeosynclinal sedimentation, gravity Lees, G. M., 1933, The reservoir rocks of Persian 903. tectonics, and ophiolite emplacement in oil fields: Am. Assoc. Petroleum Geologists Misch, P., 1946, On the discovery of Upper Per- Oman Mountains, southeast Arabia: Am. Bull., v. 17, p. 229-240. mian (Lopingian) in western Yunnan: Assoc. Petroleum Geologists Bull., v. 53, Mantura, A. J., 1972, Geophysical illusions of [Peiping] Geol. Soc. China Bull., v. 26, p. 626-671. : Am. Assoc. Petroleum p. 65-82. Geologists Bull., v. 56, p. 1552-1556. Oberlander, T., 1965, The Zagros streams: Syra- Maxwell, J. C., 1970, The Mediterranean, cuse Univ. Geog. Ser. 1, p. 18-50. MANUSCRIPT RECEIVED BY THE SOCIETY MAY , and continental drift, in The Sander, N. J., 1970, Structural evolution of the 19, 1975 megatectonics of and oceans: Mediterranean region during the Mesozoic REVISED MANUSCRIPT RECEIVED JANUARY 19, Rutgers, N. J., Rutgers Univ. Press, Era, in Geology and history of Sicily: Libya 1976 p. 167-193. Petroleum Exploration Soc., 12th ann. field MANUSCRIPT ACCEPTED FEBRUARY 18, 1976

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