Middle East and North Africa Region Projects

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This is a collection of active tectonics, geophysics research papers as they apply to the regions of the Midel East and North Africa.


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Now showing 1 - 20 of 72
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    Strain partitioning of active transpression within the Lebanese restraining bend of the Dead Sea fault (Lebanon and SW Syria)
    Gomez, F.; Nemer, T.; Tabet, C.; Khawlie, M.; Meghraoui, M.; Barazangi, M. (Geological Society of London, 2007)
    Recent neotectonic, palaeoseismic, and GPS results along the central Dead Sea fault system elucidate the spatial distribution of crustal deformation within a large (~180 km long) restraining bend along this major continental transform. Within the "Lebanese" restraining bend, the Dead Sea fault system splays into several key branches, and we suggest herein that active deformation is partitioned between NNE-SSW strike-slip faults and WNW-ESE crustal shortening. When plate motion is decomposed into strike-slip parallel to the two prominent NNE-SSW strike-slip faults (the Yammouneh and Serghaya faults) and orthogonal motion, their slip rates are sufficient to account for all expected strike-slip motion. Shortening of the Mount Lebanon range is inferred from the geometry and kinematics of the Roum fault, as well as preliminary quantification of coastal uplift. The results do not account for all expected crustal shortening, suggesting that some contraction is likely accommodated in the Anti Lebanon range. It also seems unlikely that the present kinematic configuration characterizes the entire Cenozoic history of the restraining bend. Present-day strain partitioning contrasts with published observations on finite deformation in Lebanon demonstrating distributed shear and vertical-axis block rotations. Furthermore, the present-day proportions of strike-slip displacement and crustal shortening are inconsistent with the total strike-slip offset and the lack of a significantly thickened crust. This suggests that the present rate of crustal shortening has not persisted for the longer life of the transform. Hence, we suggest that the Lebanese restraining bend evolved in a polyphase manner: An earlier episode of wrench-faulting and block rotation, followed by the later period of strain partitioning.
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    Geologic and Strategic Comments on Oil Resources in the Arabian Gulf Region
    Barazangi, Muawia (2007-04-06T17:31:33Z)
    Peak oil production in the Middle East's Arabian/Persian Gulf region and worldwide could be delayed if major multinational and national oil companies would invest more heavily in drilling and extraction technologies and push to explore new sites. Barazangi argued that the "exploration story" in the Middle East is not yet complete. Two-thirds of the world's proven recoverable oil reserves exist in the Arabian Gulf, and there are more oil fields to be discovered through offshore and deep-water drilling, as well as more oil to be extracted from existing fields. Barazangi stressed the fact that only seven countries worldwide (Saudi Arabia, Iran, Iraq, Kuwait, United Arab Emirates, Venezuela, and Russia) contain 80 percent of the world's proven recoverable oil reserves. Five of those are notably in the Arabian Gulf region and share Islamic cultures. He argued that in order to better understand oil issues in the Gulf, the world must understand the Arab and Persian people, and Islam's history and culture.
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    Global Positioning System measurements of strain accumulation and slip transfer through the restraining bend along the Dead Sea fault system in Lebanon
    Gomez, F.; Karam, G.; Khawlie, M.; McClusky, S.; Vernant, P.; Reilinger, R.; Jaafar, R.; Tabet, C.; Khair, K.; Barazangi, M. (Blackwell Publishing, 2007)
    Approximately 4 yr of campaign and continuous Global Positioning System (GPS) measurements across the Dead Sea fault system (DSFS) in Lebanon provide direct measurements of interseismic strain accumulation along a 200-km-long restraining bend in this continental transform fault. Late Cenozoic transpression within this restraining bend has maintained more than 3000 m of topography in the Mount Lebanon and Anti-Lebanon ranges. The GPS velocity field indicates 4-5 mm yr-1 of relative plate motion is transferred through the restraining bend to the northern continuation of the DSFS in northwestern Syria. Near-field GPS velocities are generally parallel to the major, left-lateral strike-slip faults, suggesting that much of the expected convergence across the restraining bend is likely accommodated by different structures beyond the aperture of the GPS network (e.g. offshore Lebanon and, possibly, the Palmyride fold belt in SW Syria). Hence, these geodetic results suggest a partitioning of crustal deformation involving strike-slip displacements in the interior of the restraining bend, and crustal shortening in the outer part of the restraining bend. Within the uncertainties, the GPS-based rates of fault slip compare well with Holocene-averaged estimates of slip along the two principal strike-slip faults: the Yammouneh and Serghaya faults. Of these two faults, more slip occurs on the Yammouneh fault, which constitutes the primary plate boundary structure between the Arabia and Sinai plates. Hence, the Yammouneh fault is the structural linkage that transfers slip to the northern part of the transform in northwestern Syria. From the perspective of the regional earthquake hazard, the Yammouneh fault is presently locked and accumulating interseismic strain.
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    Upper crustal velocity structure and basement morphology beneath the intracontinental Palmyride fold-thrust belt and north Arabian platform in Syria
    Seber, D.; Barazangi, M.; Chaimov, T.; Al-Saad, D.; Sawaf, T.; Khaddour, M. (Blackwell Publishing on behalf of The Royal Astronomical Society and The Deutsche Geophysikalische Gesellschaft, 1993)
    The intracontinental Palmyride fold-thrust belt, which is the site of an inverted Mesozoic rift, is sandwiched between two crustal blocks, the Aleppo plateau in the north and the Rutbah uplift in the south. The 400 x 100 km belt merges with the Dead Sea fault system in the southwest and gradually ends near the Euphrates depression in the northeast. Very dense (i.e., 100 m geophone spacing), reversed and multifold seismic refraction profiling was carried out to map approximately the upper 15 km of the crust in the early 1970s. These refraction data are utilized to model sedimentary rock thickness, seismic velocity, and basement morphology. Extensive data coverage also enables identification of the major faults of the region. A 2-D ray tracing technique is used in the modeling. Interpretation of these data indicates that five distinct velocity layers characterize the upper crust of the northern Arabian platform in Syria. The P-wave velocities within these layers are (in km s-1): 2.0-2.8, 4.0-4.4, 5.2-5.3 , 5.5-5.7, corresponding to sedimentary rocks from Quaternary to late Precambrian in age, and 5.9-6.0, corresponding to metamorphic basement. A comparison of the velocity models with the available drill hole information and seismic reflection profiles shows strong velocity variations in a given geologic formation, depending on the depth and location of the formation. The depth to metamorphic basement beneath the Palmyride fold belt clearly shows a deep trough, filled with Phanerozoic sedimentary rocks. These rocks decrease in thickness from about 11 km in the southwest to about 9 km in the central segment of the belt. The basement depth is about 6 km in the Aleppo plateau and not less than 8 km in the Rutbah uplift. Deeper basement in the Rutbah uplift is probably the result of a Precambrian rifting episode, clearly identified to the south in Jordan and Saudi Arabia. Cenozoic crustal shortening of about 20-25% across the southwestern segment of the Palmyride belt has not been sufficient to substantially reduce the size of the basement trough beneath this mountain belt. Finally, northeast decreasing basement depth in the Palmyrides supports the idea that the Palmyride Mesozoic rifting was developed as an aulacogen of the rifted Levantine margin along the eastern Mediterranean.
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    Stratigraphy and structure of eastern Syria across the Euphrates depression
    Sawaf, T.; Al-Saad, D.; Gebran, A.; Barazangi, M.; Best, J.; Chaimov, T. (Elsevier Science, 1993)
    Along a 450 km transect across central Syria seismic reflection data, borehole information, potential field data and surface geologic mapping have been combined to examine the crustal structure of the northern Arabian platform beneath Syria. The transect is surrounded by the major plate boundaries of the Middle East, including the Dead Sea transform fault system along the Levantine margin to the west, the Bitlis suture and East Anatolian fault to the north, and the Zagros collisional belt to the northeast and east. Three main tectonic provinces of the northern Arabian platform in Syria are crossed by this transect from south to north: the Rutbah uplift, the Palmyra fold-thrust belt, and the Aleppo plateau. The Rutbah uplift in southern Syria is a broad, domal basement-cored structure with a thick Phanerozoic (mostly Paleozoic) cover of 6-7 km. Isopachs based on well and seismic reflection data indicate that this region was an early Paleozoic depocenter. The Palmyra fold-thrust belt, the northeastern arm of the Syrian Arc, is a northeast- southwest trending intracontinental mountain belt that acts as a mobile tectonic zone between the relatively stable Rutbah uplift to the south and the less stable Aleppo plateau to the north. Short wavelength en echelon folds characterized by relatively steep, faulted southeast flanks dominate in the southwest, most strongly deformed segment of the belt, while a complex system of deeply rooted faults and broad folds characterize the northeast region, described in this study. The Aleppo plateau lies immediately north of the Palmyride belt, with a combined Paleozoic and Mesozoic sedimentary section that averages 4-5 km in thickness. Although this region appears relatively undeformed on seismic reflection data when compared to Palmyride deformation, a system of near vertical, probable strike-slip faults crosscut the region in a dominantly northeasterly direction. Gravity and magnetic modeling constrains the deep crustal structure along the transect. The crustal thickness is estimated to be approximately 38 km. Interpretation of the gravity data indicates two different crustal blocks beneath the Rutbah uplift and the Aleppo plateau, and the presence of a crustal-penetrating, high-density body beneath the northeast Palmyrides. The two distinct crustal blocks suggest that they were accreted possibly along a suture zone and/or a major strike-slip fault zone located approximately in the present-day position of the Palmyrides. The age of the accretion is estimated to be Proterozoic or early Cambrian, based on the observation of a pervasive reflection (interpreted as the Middle Cambrian Burj limestone) in the Rutbah uplift and in the Aleppo plateau and by analogy with the well-mapped Proterozoic sutures of the Arabian shield to the south.
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    Geologic evolution of the intraplate Palmyride basin and Euphrates fault system, Syria
    Sawaf, T.; Brew, G.; Litak, R.; Barazangi, M. (Museum Nationale D'Histoire Naturelle, France, 2001)
    The Palmyride Basin and the Euphrates fault system are two Late Paleozoic / Mesozoic rifts that formed on the southern margin of the NeoTethys Ocean. Data collected during hydrocarbon exploration are analyzed to determine the geologic history and regional tectonic implications of these structures. The Palmyride Basin formed during Late Paleozoic aulacogen-type rifting and subsequent Mesozoic thermal subsidence and fault reactivation. Basin inversion in the Cenozoic resulted in the formation of the Palmyride fold and thrust belt. In contrast, the Euphrates fault system is an aborted intracontinental rift, formed during the Late Cretaceous, that experienced minor transpression in the Cenozoic. Both these structures are hypothesized to have formed along zones of Proterozoic crustal weakness inherited from the accretion of the Arabian plate. Both regions also contain significant hydrocarbon reserves; predominantly gas in the Palmyride Basin and oil in the Euphrates fault system. The tectonic histories of these features are inseparably linked to the intraplate stresses generated in the northern Arabian plate by the polyphase opening and closing of the adjacent NeoTethys Ocean.
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    Seismic reflection structure of intracratonic Palmyride fold-thrust belt and surrounding Arabian platform, Syria
    McBride, J.; Barazangi, M.; Best, J.; Al-Saad, D.; Sawaf, T.; Al-Otri, M.; Gebran, A. (American Association of Petroleum Geologists (AAPG), 1990)
    Seismic reflection and drillhole data from central Syria provide a detailed view of the subsurface structure (10-15 km depth) of the relatively little studied intracratonic Palmyride fold and thrust belt. The data set, together with surface geologic mapping, constrain a structural/stratigraphic section spanning the northeast sector of the belt and the surrounding subprovinces of the Arabian platform. The seismic and drillhole data show Mesozoic stratigraphic sequences thickening rapidly into the Palmyrides from the adjacent, arched Paleozoic platforms. Neogene (Alpine) folding and thrusting of the Mesozoic basin, as documented on the seismic data, are sharply restricted to the narrow width of the belt (~100 km), which is in contrast to the relatively undeformed, Phanerozoic strata of the platforms to the north and south. The regional subsurface structure of the northeastern Palmyrides consists of a northeast-plunging anticlinorium whose outer flanks are marked by smaller superimposed asymmetric, anticlines associated with outward verging thrusts, giving this part of the belt a rough symmetry. The general structural style of folding is characterized by simple, relatively narrow anticlines and broad synclines that can be traced concordantly from the surface to at least 5 km depth on the seismic data--the level of any decollement appears to be below the imaged Mesozoic sequence. A fundamental feature of the surrounding Arabian platform subprovinces is a deep (~6-7 km, maximum) and pervasive bright reflection that forms the base of the reflective section of the platform but disappears abruptly beneath the Palmyrides. This basal reflector is important as a regional strain marker and may represent a Cambrian/Infracambrian carbonate-evaporite sequence or a remarkably uniform crystalline basement surface. The seismic and drillhole data support the hypothesis of the Palmyrides beginning as a Permian-Triassic failed rift, connected to the Levantine passive continental margin, that was inverted and complexly deformed by the interfering effects of Cenozoic movements along the Dead Sea (Levant) transform fault system and the Turkish Bitlis (Tauride) convergent zone. The seismic data provide a first-time view into the extent and depth of the early basin formation and subsequent compressional deformation, and as such provide a necessary basis for constraining reconstructions of northern Middle East plate motions.
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    Mesozoic-Cenozoic evolution of the Intraplate Euphrates fault system, Syria: Implications for regional tectonics
    Litak, R.; Barazangi, M.; Beauchamp, W.; Seber, D.; Brew, G.; Sawaf, T.; Al-Youssef, W. (The Geological Society of London, 1997)
    A lack of dramatic surface geologic structures along the Euphrates River in Syria belie a complex tectonic history revealed by newly-released seismic reflection and well data. We document the intraplate Euphrates fault system, characterize the variation in structural style along its 350 km length in Syria, and infer its Mesozoic-Cenozoic tectonic and deformational history. We then relate the deformation of the Euphrates system and other proximate intraplate structures to nearby Arabian plate boundary processes in order to develop a new model for the kinematic evolution of the northern Arabian plate. Throughout most of Mesozoic time, the Euphrates area experienced minor deposition compared to the Palmyride trough to its southwest, and the Sinjar trough to its northeast. During latest Cretaceous time, however, significant sinistral transtension occurred along the length of the Euphrates fault system in Syria, with graben formation especially noteworthy in southeastern Syria. This episode was probably related to events at nearby plate boundaries, and may have reactivated a zone of weakness formed during Pan-African accretion of the Arabian plate. A Paleogene sag basin formed over the graben system in southeastern Syria. Neogene continental collision along the northern and eastern Arabian plate boundaries precipitated minor reactivation of the Euphrates fault system in a dextral transpressional sense, in concert with significant inversion and the main phase of uplift of the nearby Palmyride and Sinjar mountains.
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    Structure and evolution of the petroliferous Euphrates graben system, southeast Syria
    Litak, R.; Barazangi, M.; Brew, G.; Sawaf, T.; Al-Imam, A.; Al-Youssef, W. (American Association of Petroleum Geologists (AAPG), 1998)
    The northwest-trending Euphrates graben system is an aborted intracontinental rift of Late Cretaceous age that has subsequently been hidden by Cenozoic burial. Approximately 100 km wide, the system comprises an extensive network of grabens and half grabens extending some 160 km from the Anah Graben in western Iraq to the Palmyride fold belt in central Syria, where it becomes more subdued. The youngest prerift rocks are presently at a maximum depth of about 5 km. Based primarily on interpretation of 1500 km of seismic reflection profiles and data from 35 wells, we mapped a complex network of numerous branching normal and strike-slip faults, generally striking northwest and west-northwest. Both branched and single-strand linear normal faults of generally steep dip, as well as positive and negative flower structures, are manifest on seismic sections. No single rift-bounding fault is observed; instead, a major flexure coupled with minor normal faulting marks the southwestern edge of the basin, with considerable variation along strike. To the northeast, deformation diminishes on the Rawda high near the Iraqi border. The Euphrates graben system likely formed in a transtensional regime, with active rifting primarily restricted to the Senonian and with an estimated maximum extension of about 6 km. Minor Cenozoic inversion of some structures also is evident. Approximately 30 oil fields have been discovered in the Euphrates graben system since 1984. Recoverable reserves discovered to date reportedly exceed 1 billion barrels of oil and lesser amounts of gas. Light oil is primarily found in Lower Cretaceous sandstone reservoirs juxtaposed by normal faulting against Upper Cretaceous synrift sources and seals.
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    Seismic fabric and 3-D upper crustal structure of the southwestern intracontinental Palmyride fold belt, Syria
    Chaimov, T.; Barazangi, M.; Al-Saad, D.; Sawaf, T.; Khaddour, M. (American Association of Petroleum Geologists (AAPG), 1993)
    The Palmyride fold belt, a 400 X 100 km transpressive belt in central Syria that is the northeastern arm of the Syrian Arc, which includes the Negev fold belt in the Sinai, is the result of Late Mesozoic and Cenozoic inversion of a Late Paleozoic and Mesozoic, NE-trending, linear intracontinental basin located within the northern Arabian platform. The southwestern Palmyrides, near the Dead Sea transform fault system and the Anti-Lebanon mountains, are characterized by short wavelength (5-10 km) en echelon folds separated by small intermontane basins that developed mainly in Neogene to Recent times. A new three-dimensional data cube, 60 X 70 km, generated on a Landmark Graphics (TM) workstation and based on approximately 700 km of two-dimensional seismic reflection profiles, elucidates the structure of the upper 10 km of the crust in the southwestern Palmyrides. Visualization of the subsurface structure, which is represented by a prominent Upper Cretaceous reflection surface in the data cube, is augmented by the topography and Bouguer gravity of the same region. Preexisting discontinuities, probable normal fault relicts of the Mesozoic Palmyride rift, likely controlled the development of individual Neogene thrusts. The new subsurface image shows important structural features not identified in outcrop. Short, WNW-trending transcurrent, or transfer, faults link the short, en echelon NE-trending thrust faults and blind thrusts of the Palmyrides. A pervasive regional decollement is not observed, even though Triassic evaporites host local detachments. There has been no wholesale transport of shallower strata on a regional decollement that decouples Mesozoic and Cenozoic rocks from underlying Paleozoic rocks. Unlike topographic relief, which only roughly resembles subsurface structures, the Bouguer gravity signature of the southwestern Palmyrides closely mimics underlying shallow geologic structures both on a large (~50 km wavelength) and a small (~5-10 km) scale. Relatively uncommon reflections from deformed Paleozoic rocks and the excellent correlation between Bouguer gravity and shallow structures indicate a general concordance between shallow Mesozoic and Cenozoic rocks and deeper Paleozoic rocks. Hence, Paleozoic rocks either deformed together with shallower strata, or structures within Paleozoic rocks controlled the development of shallower Neogene and younger structures. Our structural analysis and many other recent studies of the region are indicative of minor right-lateral shear coupled with compression in the Palmyrides.
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    Mesozoic and Cenozoic deformation inferred from seismic stratigraphy in the southwestern intracontinental Palmyride fold-thrust belt, Syria
    Chaimov, T.; Barazangi, M.; Al-Saad, D.; Sawaf, T.; Gebran, A. (Geological Society of America (GSA), 1992)
    The Palmyride fold belt in central Syria is an intracontinental northeast-trending, 400 by 100 km transpressive belt embedded in the northern Arabian platform. During the Late Paleozoic and most of the Mesozoic the region of the present-day mountains was a rift-like trough that collected over 5 km of sediments, for a total Phanerozoic thickness of over 10 km. The southwestern sector of the fold belt is bounded in the north by the Jhar fault and in the south by the south-vergent frontal thrust faults of the Palmyrides, with the broad Al-Daww depression in between. Structural features that characterize the southern and southwestern region of the Palmyrides include a short wavelength, typically 5-10 km, fold style controlled by a regional low-angle decollement within Triassic beds, and small inverted Jurassic and Early Cretaceous normal faults. Small intermontane basins (about 10 X 30 km) whose strata can be used to document the history of Palmyride deformation flank growth fault-bend folds and are mainly a product of Cenozoic shortening in the belt. These structures are elucidated by about 2000 km of newly available seismic reflection data in the Palmyrides. Synthetic seismic traces generated solely from forward modeling of outcrop information constrain seismic stratigraphic picks in two small basins about 100 km northeast of Damascus. There, minor Late Cretaceous uplift caused local onlap, marking the first inversion phase of the Palmyride trough. Tectonic quiescence throughout the Paleogene, interrupted only in the Middle Eocene by minor tectonism, resulted in monotonous deposition of about 2500 m of mostly limestone. Marked onlap and probable downlap of Lower Miocene strata onto an Oligocene angular unconformity indicate accelerated tectonism by Late Oligocene to Early Miocene time. This marks the beginning of the major phase of inversion and uplift of the Palmyrides. Recent seismicity indicates that transpression continues today. Despite its relative remoteness from convergent plate boundaries (the nearest, the Bitlis suture in southern Turkey, is about 300 km distant), the Late Cretaceous, Middle Eocene, and Neogene phases of deformation in the intraplate setting of the Palmyrides have a direct temporal relationship with major regional tectonism that occurred along the surrounding Arabian plate boundaries. The Palmyride trough was inverted in Late Cretaceous time and, subsequently, developed into a transpressive zone throughout Neogene and Quaternary times. Thus, the initiation of inversion in the Palmyrides, an integral part of the Syrian Arc, which extends from central Syria southward to central Sinai, apparently predates development of the Red Sea/Dead Sea plate boundary. In contrast, the intense Neogene through Quaternary deformational episode is clearly related to development of the Red Sea/Dead Sea fault system and to convergence along the northern boundary of the Arabian plate in southern Turkey.
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    Crustal shortening in the Palmyride fold belt, Syria, and implications for movement along the Dead Sea fault system
    Chaimov, T.; Barazangi, M.; Al-Saad, D.; Sawaf, T.; Gebran, A. (American Geophysical Union (AGU), 1990)
    The Palmyride fold belt is a northeast-trending, 400 by 100 km transpressive belt in central Syria embedded in the northern Arabian platform, bounded to the north by the Aleppo plateau and to the south by the Rutbah uplift. Palinspastically restored cross sections from three transects across the Palmyride fold belt demonstrate a minimum NW-SE shortening of about 20% or 20 km across the southwestern segment of the belt, diminishing to 1-2 km in the northeast, close to the Euphrates graben system. The cross sections are based on the 1:200,000 scale geologic map of Syria and previously unavailable seismic reflection and well data, all provided by the Syrian Petroleum Company. These results differ significantly from those predicted by kinematic models of Middle East plate motions. In western Syria and eastern Lebanon the Palmyrides obliquely intersect (at about 45 degrees) the roughly north-trending Dead Sea transform fault system. The Dead Sea fault system shows well-documented evidence of 105 km of left-lateral displacement since mid-Tertiary time south of its intersection with the Palmyrides, yet only about 25 km of motion has been documented north of that juncture in Lebanon and western Syria. Thus, kinematic models of Middle East plate motions predict 80 km of shortening in Syria, most of which should be accommodated in the Palmyride fold belt. Several possibilities exist to explain the discrepancy between the 80 km of predicted shortening and the only 20 km of shortening measured from restored cross sections. Restored cross sections offer only minimum shortening estimates, so the calculated 20 km may underestimate shortening. Second, evidence of strike-slip displacement recognized in the field and reported in the literature, and indicated by new focal mechanism solutions of two recent earthquakes in the Palmyrides, indicates that some of the still "missing" displacement may be distributed throughout central and northern Syria as strike-slip motion oblique to the relative northward convergence of the Arabian plate on the Eurasian plate. Alternatively, previous estimates of slip along the northern segment of the Dead Sea transform fault system may be only minimum estimates. A final possibility is that the Dead Sea transform fault in northwestern Syria has been active for only the past 5-6 m.y. or so, implying that it was either nonexistent or moved only slightly before the Pliocene. This would suggest that there is a total of only 45 km of N-S convergence to be found in central and northern Syria, about 25 km on the Dead Sea fault system and about 20 km in the Palmyrides. This last possibility requires that the northern and southern segments of the Dead Sea fault system developed independently during most of the past 15-20 m.y. In light of the documented but unquantified strike-slip motion in the Palmyrides, it seems reasonable that strike-slip motion does accommodate a significant portion of the convergence between the Arabian and Eurasian plates. It is likely, however, that one or more of the other proposed mechanisms also accounts for a component of the expected 80 km of shortening.
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    Summary of the geological evolution of Syria through geophysical interpretation: Implications for hydrocarbon exploration
    Brew, G.; Litak, R.; Seber, D.; Barazangi, M.; Sawaf, T.; Zaza, T. (Society of Exploration Geophysicists (SEG), 1997)
    Intracontinental deformation, caused by plate boundary processes, dominates the past and present tectonics of Syria (Figure 1). This deformation has created structures that form hydrocarbon traps in several different areas of the country. Current production from Syria is around 600,000 barrels per day and the country hosts ongoing exploratory efforts. Deformation within Syria can be conveniently divided into four zones (Figure 2): the Dead Sea fault system; the Palmyride fold and thrust belt; the Euphrates fault system; and the Abd el Aziz / Sinjar structures in the northeast of the country. Each of these areas have been, and continue to be, studied in detail by the Cornell Syria Project. The Syria Project is an industry sponsored collaborative program between Cornell and Syrian Petroleum Company (SPC) scientists that uses diverse geophysical and geological data to analyze the tectonics of the northern Arabian platform.
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    Basement depth and sedimentary velocity structure in the northern Arabian platform, Eastern Syria
    Brew, G.; Litak, R.; Seber, D.; Barazangi, M.; Sawaf, T.; Al-Imam, A. (Blackwell Publishing on behalf of The Royal Astronomical Society and The Deutsche Geophysikalische Gesellschaft, 1997)
    Basement depth in the Arabian plate beneath eastern Syria is found to be much deeper than previously supposed. Deep-seated faulting in the Euphrates graben system is also documented. Data from a detailed, 300 km long, reversed refraction profile, with offsets up to 54 km, are analyzed and interpreted, yielding a velocity model for the upper ~ 9 km of continental crust. The interpretation integrates the refraction data with seismic reflection profiles, well logs and potential field data, such that the results are consistent with all available information. A model of sedimentary thicknesses and seismic velocities throughout the region is established. Basement depth on the north side of the Euphrates is interpreted to be around 6 km, whilst south of the Euphrates basement depth is at least 8.5 km. Consequently, the potentially hydrocarbon-rich pre-Mesozoic section is shown, in places, to be at least 7 km thick. The dramatic difference in basement depth on adjacent sides of the Euphrates graben system might suggest that the Euphrates is a suture zone, possibly inherited from Late Proterozoic accretion of the Arabian plate. Gravity modeling across the southeast Euphrates system tends to support this hypothesis. Incorporation of previous results allows us to speculate on the position of possible suture zones in Syria.
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    Tectonic map and geologic evolution of Syria: The role of GIS
    Brew, G.; Barazangi, M.; Sawaf, T.; Al-Maleh, K. (Society of Exploration Geophysicists (SEG), 2000)
    For the past 12 years, Cornell Syria Project scientists and colleagues at the Syrian Petroleum Company have studied the regional structure and geologic evolution of Syria. We are currently generating new structural maps and tectonic models for the whole country. Information on this region is relatively limited, despite the local importance of hydrocarbon production and abundant surface and subsurface data. Our regional approach involves new interpretations of seismic reflection profiles, well data, remote sensing imagery, and potential-field data, merged with existing interpretations of similar data sets. These interpretations, integrations, analyses, and map preparation are all performed within a GIs platform. As detailed elsewhere in this issue, the importance of GIs as a data storage and interrogation tool for petroleum exploration is well established. This article describes our use of GIs to facilitate regional tectonic mapping in Syria. Although not directly related to the search for hydrocarbons, the maps and models generated have obvious utility for oil exploration. Herein we detail the types of data being used, their integration and interpretation within the GIs, and our preliminary analysis and findings. We will show how a GIs approach eases data archiving and map generation and also provides interpretational possibilities not available with more traditional mapping procedures.
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    Tectonic evolution of Syria Interpreted from Integrated Geophysical and Geological Analysis
    Brew, G. (Cornell University, 2001-01)
    Using a variety of geophysical and geological data, the Phanerozoic tectonic evolution of Syria has been interpreted. The study is inspired by the diverse styles of tectonic deformation within Syria generated by long-lived proximity to active plate boundaries. The work is also relevant to hydrocarbon exploration. The availability of seismic reflection and refraction profiles, wells, and other resources made this research possible. Three studies focused on specific areas of Syria are presented. The first is a seismic refraction interpretation along a north-south profile in eastern Syria. The results show that metamorphic basement depth (and hence Paleozoic thickness) in southeast Syria is greater, by >2 km, than that in the northeast. The next study interprets the structure and tectonics in northeast Syria. During Late Paleozoic and Mesozoic time northeast Syria was an extension of the Palmyride trough. In the Maastrichtian, regional extension opened the Abd el Aziz and Sinjar graben that were structurally inverted in the Late Cenozoic to form the present topography. The third study concerns the Ghab Basin in western Syria. This 3.4 km deep Plio- Quaternary pull-apart basin suggests that the Dead Sea Fault System has only been active in Syria since the end of the Miocene in accordance with a two-phase model of Red Sea opening. The final study integrates the previous interpretations with new work to provide a tectonic evolutionary model that shows the Phanerozoic development of all Syria. This model is closely tied to stratigraphic data that improve the interpretation of many tectonic events, and put the results into a paleogeographical context. The model shows how specific deformation episodes within Syria have been penecontemporaneous with regional plate tectonic events. The Late Paleozoic / Mesozoic northeast trending Palmyride / Sinjar trough formed across central Syria in response to Permo-Triassic opening of the NeoTethys Ocean. Proximal subduction in the NeoTethys created the Late Cretaceous Euphrates Fault System and Abd El Aziz / Sinjar graben in eastern Syria. Late Cretaceous to Late Miocene collisions and shortening along the northern Arabian margin caused platform-wide structural inversion, uplift, and shortening. This compression continues today under the influence of Arabia / Eurasia convergence.
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    Tectonic evolution of the northeast Palmyride mountain belt, Syria: the Bishri crustal block
    Brew, G.; Best, J.; Barazangi, M.; Sawaf, T. (Geological Society of London, 2003)
    Investigating the Bishri block, centrally positioned amid the diverse tectonic and structural zones of Syria, reveals details of the intraplate Phanerozoic development of the northern Arabian platform. The Bishri block is a broad northeast plunging inverted basin located at the northeast portion of the Palmyride mountain belt where the mountains intersect the Euphrates fault system. Well and seismic data show that subsidence and sedimentation in the Bishri area was generally continuous from Carboniferous to Palaeocene time, with the Bishri block part of the extensive Palmyride / Sinjar trough. Major bounding faults and a rift-type environment are documented in the Permo-Triassic, Jurassic and Cretaceous. The present Bishri structural and topographic high has been formed through transpressive structural inversion since the Middle Miocene; high-angle Mesozoic bounding normal faults now have net reverse offsets with a significant dextral strike-slip component. East of the Bishri block, towards the Euphrates fault system, north-northwest - south-southeast striking normal faults exhibit less reverse movement. This deformation history correlates with the opening and closing of the nearby NeoTethys ocean that has driven the evolution of the intracontinental Syria.
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    Bouguer gravity trends and crustal structure of the Palmyride mountain belt and surrounding northern Arabian platform in Syria
    Best, J.; Barazangi, M.; Al-Saad, D.; Sawaf, T.; Gebran, A. (Geological Society of America (GSA), 1990)
    This study examines the crustal structure of the Palmyrides and the northern Arabian platform in Syria by two- and three-dimensional modeling of the Bouguer gravity anomalies. Results of the gravity modeling indicate that: (1) western Syria is composed of at least two different crustal blocks, (2) the southern crustal block is penetrated by a series of crustal-scale, high-density intrusive complexes, and (3) short-wavelength gravity anomalies in the southwest part of the mountain belt are clearly related to basement structure. The crustal thickness in Syria, as modeled on the gravity profiles, is approximately 40 +/- 4 km, which is similar to crustal thicknesses interpreted from refraction data in Jordan and Saudi Arabia. The different crustal blocks and large-scale mafic intrusions are best explained, though not uniquely, by Proterozoic convergence and suturing and early Paleozoic rifting, as interpreted in the exposed rocks of the Arabian shield. These two processes, combined with documented Mesozoic rifting and Cenozoic transpression, comprise the crustal evolution of the northern Arabian platform beneath Syria.
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    Continental margin evolution of the northern Arabian platform in Syria
    Best, J.; Barazangi, M.; Al-Saad, D.; Sawaf, T.; Gebran, A. (American Association of Petroleum Geologists (AAPG), 1993)
    Synthesis of available geological and geophysical data in the Syrian Arab Republic permits a descriptive account of the pre-Cenozoic geologic history of the northern Arabian platform. The northern Arabian platform appears to be a composite plate similar to that interpreted in the rocks of the Arabian shield. The structural and stratigraphic relationships of the Paleozoic and Mesozoic sedimentary sections in Syria record the transformation of an east-facing Gondwanaland passive-margin in the early Paleozoic into a west-facing Levantine margin in the Mesozoic, at which time the northern platform was intimately associated with the creation of the eastern Mediterranean basin. Timing of the margin transformation is inferred from the orientation and thickness variations of Lower Triassic rocks, but the transformation may have initiated as early as the Permian. The diversity and timing of geologic features in Syria suggest that the northern Arabian platform did not behave as a rigid plate throughout its geologic history. The present-day Palmyride mountain belt located within the northern Arabian platform in Syria, initiated in early Mesozoic time as a northeast trending rift nearly perpendicular to the Levantine margin, was subsequently inverted in the Cenozoic by transpression. The location of the rift may be associated with the reactivation of a zone of crustal weakness, i.e., a Proterozoic suture zone previously proposed from modeling of Bouguer gravity data. Thus, the northern and southern portions of the Arabian platform have similarities in their geologic history during the Proterozoic and Paleozoic; however, the northern Arabian platform was intimately affected by Mesozoic rifting and the creation of the eastern Mediterranean basin during the Mesozoic.
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    Structure of the intracontinental Palmyride mountain belt in Syria and its relationship to nearby Arabian plate boundaries
    Barazangi, M.; Seber, D.; Al-Saad, D.; Sawaf, T. (Cukurova University, 1992)
    The intracontinental Palmyride mountain belt strikes NE and is located within the northern Arabian platform. The belt is about 400 km in length and about 100 km in width. Abundant data, including seismic reflection and refraction profiles, drill holes, gravity, magnetics, and geologic maps are used to infer the crustal structure and geologic evolution of this belt. The Palmyrides were the site of an early Mesozoic aulacogen-type depression that was linked to the Levantine rifted continental margin in the eastern Mediterranean. Seismic stratigraphic analysis indicates that inversion of the Palmyride depression was initiated in late Cretaceous time, but especially intensified in Neogene and Quaternary times. The inversion process varies considerably along strike and involves both shortening by folding and reverse faulting (including the inversion of some of the Mesozoic rift-bounding normal faults) as well as translation and rotation along numerous strike-slip faults. The inversion processes formed at least three structurally distinct crustal blocks within the Palmyrides. The two blocks in the northeast Palmyrides (Bilas and Bishri) consist of broad anticlines that exhibit symmetrical thick-skinned deformation with reverse faults on the southern and northern flanks of the belt, whereas the southwestern Palmyrides consist of long linear ridges with intervening depressions that exhibit clear south vergence and local detachment, probably within Triassic evaporites. Depth to metamorphic basement beneath the Palmyrides increases from 9 km in the northeast to 11 km in the southwest. This is in contrast to a basement depth of about 6-8 km beneath the adjacent stable Arabian platform. A 20-25% estimated shortening across the southwestern Palmyrides has not been sufficient to invert the basement morphology beneath this mountain belt. Close temporal relations between inversion episodes in the Palmyrides and well-documented episodes of convergence and collision along nearby Arabian plate boundaries suggest that plate boundary stresses are transmitted hundreds of kilometers across the northern Arabian platform to the Palmyrides. Finally, Bouguer gravity observations provide an estimate of crustal thickness of about 38 km beneath the Palmyrides, but also require different crustal properties to the north and south of the Palmyrides. These observations suggest that the Palmyrides occupy the location of a possible Precambrian (Proterozoic?) suture and/or strike-slip fault zone along which the two crustal blocks of northern Arabia were accreted. This possible early history may explain the subsequent development of the Palmyrides in early Mesozoic time as due to a reactivation of a zone of crustal weakness along the postulated Proterozoic suture zone.