http://hdl.handle.net/1813/5304 2013-05-21T03:06:19Z 2013-05-21T03:06:19Z Gomez, F. Nemer, T. Tabet, C. Khawlie, M. Meghraoui, M. Barazangi, M. http://hdl.handle.net/1813/9412 2007-12-29T04:00:24Z 2007-01-01T00:00:00Z

Title: Strain partitioning of active transpression within the Lebanese restraining bend of the Dead Sea fault (Lebanon and SW Syria) Authors: Gomez, F.; Nemer, T.; Tabet, C.; Khawlie, M.; Meghraoui, M.; Barazangi, M. Abstract: 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. Description: This material has been published in The Journal of the Geological Society of London, the only definitive repository of the content that has been certified and accepted after peer review. Copyright and all rights therein are retained by The Geological Society of London. Copyright 2001, The Geological Society of London. See also: http://atlas.geo.cornell.edu/deadsea/publications/Gomez2007_GSL.htm

2007-01-01T00:00:00Z Barazangi, Muawia http://hdl.handle.net/1813/5771 2007-04-06T17:31:34Z 2007-04-06T17:31:33Z

Title: Geologic and Strategic Comments on Oil Resources in the Arabian Gulf Region Authors: Barazangi, Muawia Abstract: 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. Description: This audio recording is in Arabic.

2007-04-06T17:31:33Z Seber, Dogan http://hdl.handle.net/1813/5540 2007-04-05T06:08:53Z 1995-01-01T00:00:00Z

Title: Lithospheric and upper mantle structure beneath northern Morocco and central Syria Authors: Seber, Dogan Abstract: Northern Morocco and central Syria accommodate two of the most significant intraplate mountain belts on earth: the Atlas Mountains (High and Middle) and the Palmyride mountains, respectively. In contrast to interplate mountain belts like the Rif mountains in northern Morocco, intraplate mountain belts develop away from any plate boundaries. Hence, their formation is more difficult to explain. In this dissertation, seismological data from a recently installed digital seismic network in Morocco along with other available datasets, such as Bouguer gravity, seismic reflection, and surface geology, are analyzed in order to map the three-dimensional structure of the lithosphere and upper mantle beneath northern Morocco. Seismic data are also used in explaining some aspects of earthquake hazards in Morocco. New geodynamic models are proposed for both the Atlas and Rif mountains of northern Morocco. Teleseismic tomography results show that the lithosphere beneath the Atlas mountains is relatively thinner as evidenced by slower velocity anomalies. In contrast, beneath the Rif mountains a relatively fast upper mantle velocities are observed. Isostatic gravity anomalies show that the central High Atlas has a thick (~45 km) and isostatically compensated crust, whereas the Middle Atlas with a crustal thickness of about 30 km is not compensated, and that they are probably dynamically supported. The spatial distribution of intermediate-depth seismicity, regional seismic waveform propagation characteristics, Bouguer gravity anomalies, seismic reflection and drill hole data as well as surface geology are used to argue that the lithosphere beneath the Rif region has delaminated and it is sinking into the asthenosphere. This ongoing delamination process is proposed to have formed the Rif and Betic mountain belts around the Alboran Sea. The Palmyride intraplate mountain belt in central Syria, which shows a similar geologic history to the Atlas system of Morocco, is also studied. The upper part of the crust is mapped in central Syria beneath the Palmyrides fold-thrust belt and adjacent areas using very dense seismic refraction data. The results show that beneath the axis of the Palmyrides mountain belt a deep (~11 km) trough, formed in the Mesozoic, exists despite the Cenozoic inversion and uplift. Description: Copyright 1995, Dogan Seber. See also: http://atlas.geo.cornell.edu/dissertations/Seber_1995.htm

1995-01-01T00:00:00Z Ni, James http://hdl.handle.net/1813/5539 2007-04-05T06:08:51Z 1984-01-01T00:00:00Z

Title: Seismicity and active tectonics of the Himalayas and Tibetan Plateau Authors: Ni, James Abstract: Available geophysical and geological data are analyzed with additional new data to further the understanding of the fundamental tectonic processes involved in the Himalayan-Tibetan continental collision zone. Seismicity of the Himalayas suggests that at present the Indian Plate underthrusts the Himalayas as a coherent unit along a shallow detachment. The geometry of this detachment beneath the Lesser Himalayas is constrained by well data and well-determined focal depths of moderate-sized earthquakes. This detachment surface, at or near the top of the downgoing Indian plate, dips at approximately a 15 degree angle from about 10-km to 20-km depth. This result supports a model of the active tectonics of the Himalayas as "thin-skinned" and analogous to the Paleozoic tectonics of the southern Appalachian Collision Zone. New seismological observations of velocities and propagation characteristics of Pn, Sn and Lg waves beneath the Himalaya-Tibet and surrounding region can be interpreted, although not uniquely, to indicate the shallow-angle underthrusting of the Indian continental lithosphere beneath the Tibetan Plateau. The most significant observation is that, except beneath the northern part, high-frequency Sn waves propagate efficiently in the uppermost mantle beneath the Tibetan Plateau. Strong attenuation of Sn waves suggests the existence of a low-Q zone in the uppermost mantle beneath northern Tibet. Analysis of Landsat imagery and fault plane solutions of shallow crustal earthquakes in both the Tethyan Himalayas and Tibet indicate that normal faulting and east-west extension are the dominant mode of deformation occurring in the late Cenozoic time. The normal faulting is due to an east-west deviatoric tensional stress within the elevated Tethyan Himalayas and Tibet. Seismicity combined with structural elements mapped from digitally processed Landsat 3 Multispectral Scanner (MSS) data provide valuable information about neotectonic processes in the overthrusting western Himalayan blocks. The rhomboidal-shaped upper Sutlej River Basin consists of many NNE-trending fault blocks and is interpreted as a pull-apart basin. This pull-apart basin is explained as a result of oblique underthrusting of the Indian plate beneath Himalayas-Tibet. Description: Copyright 1984, James Ni. See also: http://atlas.geo.cornell.edu/dissertations/Ni_1984.htm

1984-01-01T00:00:00Z Gomez, Francisco http://hdl.handle.net/1813/5538 2007-04-05T06:08:49Z 1999-01-01T00:00:00Z

Title: Late Cenozoic tectonics of the Middle Atlas Mountains, Morocco: Continental deformation in the diffuse western Mediterranean plate boundary Authors: Gomez, Francisco Abstract: The Atlas Mountains of North Africa, located in the African foreland of the Alpine mountain belts, comprise a 2,000 km long Cenozoic mountain chain whose development was guided by older Mesozoic rift structures. This dissertation examines one component, the Middle Atlas Mountains of Morocco, using geological and geophysical data to constrain the tectonic development of the mountain chain. These results are then placed in the broader context of regional deformation. The NE-SW trending Middle Atlas Mountains are obliquely oriented within the late Cenozoic regional stress field, resulting in deformation partitioned into strike-slip faulting and thrust-related folding. Kinematic analyses of fault-slip data and earthquake focal mechanisms demonstrate that compressional deformation dominates the Folded Middle Atlas, whereas strike-slip faulting, with possible horizontal extension, predominates in the Tabular Middle Atlas. Geological field observations, digital topography, LANDSAT imagery, and seismicity provide evidence for recent tectonics in the Middle Atlas. In the central Middle Atlas, cross-section balancing across the 20 km wide fold belt demonstrates about 4.7 km of Cenozoic horizontal shortening producing 800 m of structural relief. Other constraints on crustal thickening suggest a discrepancy between contraction and thickening. One possible explanation involves partitioning crustal deformation with depth: The upper crust shortens by thickening (faulting and folding), whereas the lower crust deforms laterally. At the northern extent of the mountain chain, the Guercif Basin developed where the Middle Atlas abut the Rif thrust belt. Similar timing of extensional deformation and proximity with the Rif, suggest that the Guercif Basin has been influenced by Rif tectonics. Stratal relations demonstrate that uplift of the Middle Atlas is a late Cenozoic phenomenon. In Morocco, shortening of the High and Middle Atlas Mountains accommodated 20-45% of the total African-Eurasian plate convergence since the Early Miocene. The diffuse plate boundary comprises large, relatively rigid crustal blocks (Moroccan Meseta, High Plateau, and Saharan Platform) bounded by narrow deformable zones (the Atlas). In this context, the Middle Atlas can be interpreted as an accommodation zone resulting from differential movements between two large crustal blocks impinging on stable Africa. The Atlas Mountains exemplify the possible structural influence of inherited crustal weaknesses in a diffuse plate boundary such as the western Mediterranean region. Description: Copyright 1999, Francisco Gomez. See also: http://atlas.geo.cornell.edu/dissertations/Gomez_1999.htm

1999-01-01T00:00:00Z Chaimov, Thomas http://hdl.handle.net/1813/5537 2007-04-05T06:08:50Z 1991-01-01T00:00:00Z

Title: Balanced cross sections, seismic stratigraphy, and structural interpretation of the intracontinental Palmyride fold belt, Syria Authors: Chaimov, Thomas Abstract: The Palmyride fold belt in central Syria is the result of Late Mesozoic and Cenozoic inversion of a Late Paleozoic and Mesozoic intraplate trough located within the northern Arabian platform. Detailed analysis of available seismic reflection profiles from the Palmyrides reveals the Late Mesozoic to present transpressive structures of the Palmyrides and clarifies the timing and magnitude of such deformation within the belt. Uplift of the Mesozoic Palmyride trough began in the Late Cretaceous, rejuvenated in the Middle Eocene, and culminated in the period from the Miocene to present. Each of the three episodes of deformation was temporally associated with a distant (~300 km) Arabian plate margin tectonic event as follows: (1) Late Cretaceous collision between the northern and eastern margin of the Arabian plate and a microplate or island arc; (2) Middle Eocene incipient faulting of the Red Sea/Dead Sea fault system; and (3) Miocene to present shortening of the Arabian-Eurasian plate collision zone along the Bitlis/Zagros suture in Turkey and Iran. Despite this repeated tectonism, only 20-25 km of shortening accumulated in the southwestern, most strongly deformed sector of the belt, diminishing to only a few kilometers 400 km along strike to the northeast. And although Triassic evaporites form local detachment surfaces, there has been no large-scale lateral transport of Mesozoic and Cenozoic rocks over Paleozoic rocks in the Palmyrides of Syria. Rather, deep structures in Paleozoic rocks appear to be in general concord with structures in overlying Mesozoic and Cenozoic rocks. Description: Copyright 1991, Thomas Chaimov. See also: http://atlas.geo.cornell.edu/dissertations/Chaimov_1991.htm

1991-01-01T00:00:00Z Best, John http://hdl.handle.net/1813/5536 2007-04-05T06:08:54Z 1991-01-01T00:00:00Z

Title: Crustal evolution of the northern Arabian Platform beneath the Syrian Arab Republic Authors: Best, John Abstract: Newly released geological and geophysical data from the Syrian Arab Republic are used to document the geological history of the northern Arabian platform in the Middle East. The primary observation of this synthesis is the focusing of various phases of Phanerozoic deformation (Mesozoic rifting and Cenozoic transpression) along strike of a proposed Proterozoic suture that has acted as a long-lived zone of crustal weakness. This deformation zone is presently manifested by the intracontinental Palmyride mountain belt, an inverted rift, trending NE-SW through central Syria. The geological history recognized for the northern Arabian platform is similar in many respects to that of the southern Arabian platform, including: (1) Proterozoic convergence and cratonization, (2) minor Cambrian extension, (3) a relatively stable Paleozoic margin of Gondwanaland marked by predominantly clastic deposition, (4) eastward tilting of the Arabian plate in the Cenozoic. The important difference in the evolution of the northern platform from the southern platform occurs during the Mesozoic with the development of the Levantine margin in the eastern Mediterranean and the Palmyride rift in the continental interior. The intracontinental Palmyride mountain belt is the result of Late Cretaceous-present inversion of the Palmyride rift. Reactivation of rift boundary faults occurred in response to transpressive movement along basement-controlled strike-slip faults. The belt is divided into three provinces based on changes in structural style: the south Palmyride fold belt characterized by narrow, en enchelon ridges, the Bishri, and Bilas blocks expressed as broad, antiformal structures. The mountain belt may be characterized by thin-skinned deformation in the south fold belt and thick-skinned deformation in the northern and eastern provinces. Description: Copyright 1991, John Best. See also: http://atlas.geo.cornell.edu/dissertations/Best_1991.htm

1991-01-01T00:00:00Z Beghoul, Mohammed Noureddine http://hdl.handle.net/1813/5535 2007-04-05T06:08:47Z 1991-01-01T00:00:00Z

Title: Lithospheric structure of the western United States and the Tibetan Plateau: Implications on their mechanism of uplift Authors: Beghoul, Mohammed Noureddine Abstract: This dissertation seeks to determine the upper mantle structure and the mechanisms responsible for the Cenozoic uplift of the high terranes located near plate boundaries: the Tibetan Plateau and western North America. The upper mantle structure is determined using the first P arrivals obtained from the International Seismological Centre (ISC) at regional distances (2 - 22 degrees). In the first chapter a methodology is presented for computing mantle lid Pn velocities using ISC data together with a detailed error analysis. Application of this algorithm to Colorado Plateau yields an average Pn velocity of 8.12 +/- 0.09 km/s. This value is higher than the one reported in the literature but similar to that beneath stable midcontinent regions. We use this Pn value and the Cenozoic history of the plateau to constrain the mode of uplift. In chapter two, using the same techniques, we confirm the lower Pn velocity beneath the Basin and Range Province and show the presence of about 4% intrinsic azimuthal Pn velocity anisotropy in the mantle lid beneath the Basin and Range. The direction of high velocity coincides with the direction of present-day extension in the Basin and Range Province (i.e., NW - SE). We show that this anisotropy is the result of Cenozoic extension rather than a cumulative signature of older tectonic events. In chapter three, a modified version of the algorithm and detailed mapping of Sn attenuation allow the determination of mantle lid thickness beneath the western United States and Tibet. We show that the mantle lid thickness beneath the southern 2/3 of Tibet ranges from 135-165 km thick. This value is similar to the one we find for the Great Plains. The deep structure, Cenozoic uplift, and various other geophysical and geological data of these two high terranes are consistent with the subduction of flat slabs beneath them. The continental Indian Plate is still beneath the southern 2/3 of Tibet, but the oceanic Farallon Plate has already been delaminated from the overriding North American Plate. Description: Copyright 1991, Mohammed Noureddine Beghoul. See also: http://atlas.geo.cornell.edu/dissertations/Beghoul_1991.htm

1991-01-01T00:00:00Z Beauchamp, Weldon http://hdl.handle.net/1813/5534 2007-04-05T06:08:43Z 1998-01-01T00:00:00Z

Title: Tectonic evolution of the Atlas Mountains, North Africa Authors: Beauchamp, Weldon Abstract: The Atlas Mountains of North Africa are one of the largest intracontinental mountain belts in the world. Despite the size of this orogen, the basic kinematic and tectonic evolution of the Atlas Mountains has previously not been well understood. These mountains formed hundreds of kilometers from active plate margins. The formation of the Atlas Mountains was greatly influenced by a previous Mesozoic intracontinental rift system. This rift system spanned half of the African continent and was larger in breadth than the Red Sea. This study set out to synthesize existing data and studies of the Atlas Mountains and integrate these data with new geological, geophysical and remote sensing data. The construction of a tectonic map was undertaken to define the tectonic units and terraines of North Africa. The delineation of these regions allow for the study of how they have interacted during the kinematic evolution of the Atlas system. Geological field work was undertaken to study the kinematics of inversion tectonics and to construct a balanced geological-geophysical transect. The transect suggests shortening across the orogen (36 km) was achieved by thrusting along detachments at several levels in the upper crust. Syn-rift and post-rift sedimentary rocks were uplifted by the reactivation of Synrift normal faults and newly formed thin-skinned thrust faults. A restoration of the deformed cross section indicates the original Atlas rift basin was approximately 113 kilometers wide. Shortening across the High Atlas Mountains resulted in a partitioning of strain, with the greatest magnitude of shortening occurring along the margins of the High Atlas Mountains. The partitioning of strain may involve the transfer of shortening from the margins at shallow depths, to the mid-lower crust in the central region of the orogen. Thrusting in the High Atlas Mountains is bivergent, with thrusts dipping to the south along the northern margin, and northward dipping faults to the south. The presence of preexisting structural geometries such as accommodation zones, fault ramps, fault relays and en echelon faulting formed by rift processes will have an effect on subsequent compressional stress fields generated by plate convergence and other tectonic processes. Superposed folding which is disharmonic may in fact be a unique characteristic to inverted rift systems that result in intracontinental mountain belts. Description: Copyright 1998, Weldon Beauchamp. See also: http://atlas.geo.cornell.edu/dissertations/Beauchamp_1998.htm

1998-01-01T00:00:00Z Gomez, F. Karam, G. Khawlie, M. McClusky, S. Vernant, P. Reilinger, R. Jaafar, R. Tabet, C. Khair, K. Barazangi, M. http://hdl.handle.net/1813/5436 2007-03-22T06:01:03Z 2007-01-01T00:00:00Z

Title: Global Positioning System measurements of strain accumulation and slip transfer through the restraining bend along the Dead Sea fault system in Lebanon Authors: Gomez, F.; Karam, G.; Khawlie, M.; McClusky, S.; Vernant, P.; Reilinger, R.; Jaafar, R.; Tabet, C.; Khair, K.; Barazangi, M. Abstract: 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. Description: An edited version of this paper was published in Geophysical Journal International by Blackwell Publishing. Blackwell Publishing retains the copyright to this paper (Copyright 2007). See also: http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-246X.2006.03328.x; http://atlas.geo.cornell.edu/deadsea/publications/Gomez2007_GJI.htm

2007-01-01T00:00:00Z