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Sample records for rift system final

  1. Discussion on final rifting evolution and breakup : insights from the Mid Norwegian - North East Greenland rifted system

    NASA Astrophysics Data System (ADS)

    Peron-Pinvidic, Gwenn; Terje Osmundsen, Per

    2016-04-01

    In terms of rifted margin studies, the characteristics of the distal and outer domains are among the today's most debated questions. The architecture and composition of deep margins are rarely well constrained and hence little understood. Except from in a handful number of cases (eg. Iberia-Newfoundland, Southern Australia, Red Sea), basement samples are not available to decipher between the various interpretations allowed by geophysical models. No consensus has been reached on the basement composition, tectonic structures, sedimentary geometries or magmatic content. The result is that non-unique end-member interpretations and models are still proposed in the literature. So, although these domains mark the connection between continents and oceans, and thus correspond to unique stages in the Earth's lithospheric life cycle, their spatial and temporal evolution are still unresolved. The Norwegian-Greenland Sea rift system represents an exceptional laboratory to work on questions related to rifting, rifted margin formation and sedimentary basin evolution. It has been extensively studied for decades by both the academic and the industry communities. The proven and expected oil and gas potentials led to the methodical acquisition of world-class geophysical datasets, which permit the detailed research and thorough testing of concepts at local and regional scales. This contribution is issued from a three years project funded by ExxonMobil aiming at better understanding the crustal-scale nature and evolution of the Norwegian-Greenland Sea. The idea was to take advantage of the data availability on this specific rift system to investigate further the full crustal conjugate scale history of rifting, confronting the various available datasets. In this contribution, we will review the possible structural and sedimentary geometries of the distal margin, and their connection to the oceanic domain. We will discuss the definition of 'breakup' and introduce a first order conceptual

  2. European Cenozoic rift system

    NASA Astrophysics Data System (ADS)

    Ziegler, Peter A.

    1992-07-01

    The European Cenozoic rift system extends from the coast of the North Sea to the Mediterranean over a distance of some 1100 km; it finds its southern prolongation in the Valencia Trough and a Plio-Pleistocene volcanic chain crossing the Atlas ranges. Development of this mega-rift was paralleled by orogenic activity in the Alps and Pyrenees. Major rift domes, accompanied by subsidence reversal of their axial grabens, developed 20-40 Ma after beginning of rifting. Uplift of the Rhenish Shield is related to progressive thermal lithospheric thinning; the Vosges-Black Forest and the Massif Central domes are probably underlain by asthenoliths emplaced at the crust/mantle boundary. Evolution of this rift system, is thought to be governed by the interaction of the Eurasian and African plates and by early phases of a plate-boundary reorganization that may lead to the break-up of the present continent assembly.

  3. Venus: Geology of Beta Regio rift system

    NASA Technical Reports Server (NTRS)

    Nikishin, A. M.; Borozdin, V. K.; Bobina, N. N.

    1992-01-01

    Beta Regio is characterized by the existence of rift structures. We compiled new geologic maps of Beta Regio according to Magellan data. There are many large uplifted tesserae on beta upland. These tesserae are partly buried by younger volcanic cover. We can conclude, using these observations, that Beta upland formed mainly due to lithospheric tectonic uplifting and was only partly constructed by volcanism. Theia Mons is the center of the Beta rift system. Many rift belts are distributed radially to Theia Mons. Typical widths of rifts are 40-160 km. Rift valleys are structurally represented by crustal grabens or half-grabens. There are symmetrical and asymmetrical rifts. Many rifts have shoulder uplifts up to 0.5-1 km high and 40-60 km wide. Preliminary analysis for rift valley structural cross sections lead to the conclusion that rifts originated due to 5-10 percent crustal extension. Many rifts traverse Beta upland and spread to the surrounding lowlands. We can assume because of these data that Beta rift system has an active-passive origin. It formed due to regional tectonic lithospheric extension. Rifting was accelerated by upper-mantle hot spot origination under the center of passive extension (under the Beta Regio).

  4. The role of inheritance in structuring hyperextended rift systems

    NASA Astrophysics Data System (ADS)

    Manatschal, Gianreto; Lavier, Luc; Chenin, Pauline

    2015-04-01

    -related mantle processes may control the rheology of the mantle, the magmatic budget, the thermal structure and the localization of final rifting Conversely, the deformation in hyperextended domains is strongly controlled by weak hydrated minerals (e.g. clay, serpentinite) that result form the breakdown of feldspar and olivine due to fluid and reaction assisted deformation and is consequently not inherited but the result of rift induced processes. These key observations show that both inheritance and rift-induced processes play a significant role in the development of magma-poor rift systems and that the role of inheritance may change as the physical conditions vary during the evolving rifting and as rift-induced processes (serpentinization; magma) become more important. Thus, it is not only important to determine the "genetic code" of a rift system, but also to understand how it interacts and evolves during rifting. Understand how far these new ideas and concepts derived from the southern North Atlantic and Alpine Tethys can be translated to other less explored hyperextended rift systems will be one of the challenges of the future research in rifted margins.

  5. Numerical modeling of continental rifting: Implications for the East African Rift system

    NASA Astrophysics Data System (ADS)

    Koptev, Alexander; Burov, Evgueni; Calais, Eric; Leroy, Sylvie; Gerya, Taras; Guillou-Frottier, Laurent; Cloetingh, Sierd

    2016-04-01

    The East African Rift system (EARS) provides a unique system with juxtaposition of two contrasting yet simultaneously formed rift branches, the eastern, magma-rich, and the western, magma-poor, on either side of the old thick Tanzanian craton embedded into younger lithosphere. Here we take advantage of the improvements in our understanding of deep structures, geological evolution and recent kinematics, together with new cutting edge numerical modeling techniques to design a three-dimensional ultra-high resolution viscous plastic thermo-mechanical numerical model that accounts for thermo-rheological structure of the lithosphere and hence captures the essential geophysical features of the central EARS. Based on our experiments, we show that in case of the mantle plume seeded slightly to the northeast of the craton center, the ascending plume material is deflected by the cratonic keel and preferentially channeled along the eastern side of the craton, leading to formation of a large rift zone characterized by important magmatic activity with substantial amounts of melts derived from mantle plume material. This model is in good agreement with the observations in the EARS, as it reproduces the magmatic eastern branch and at the same time, anticlockwise rotation of the craton. However, this experiment does not reproduce the observed strain localization along the western margin of the cratonic bloc. To explain the formation of contrasting magmatic and amagmatic rift branches initiating simultaneously on either side of a non-deforming block as observed in the central EARS, we experimentally explored several scenarios of which three can be retained as specifically pertaining to the EARS: (1) The most trivial first scenario assumes rheologically weak vertical interface simulating the suture zone observed in the geological structure along the western border of the craton; (2) The second scenario involves a second smaller plume initially shifted in SW direction; (3) Finally, a

  6. Along-rift Variations in Deformation and Magmatism in the Ethiopian and Afar Rift Systems

    NASA Astrophysics Data System (ADS)

    Keir, D.; Bastow, I. D.; Corti, G.; Mazzarini, F.; Rooney, T. O.

    2015-12-01

    The geological record at rifts and margins worldwide often reveals along-strike variations in volumes of extruded and intruded igneous rocks. These variations may be the result of asthenospheric heterogeneity, variations in rate, and timing of extension; alternatively, preexisting plate architecture and/or the evolving kinematics of extension during breakup may exert first-order control on magmatism. The Ethiopian and Afar Rift systems provide an excellent opportunity to address this since it exposes, along strike, several sectors of asynchronous rift development from continental rifting in the south to incipient oceanic spreading in the north. Here we perform studies of distribution and style of volcanism and faulting along strike in the MER and Afar. We also incorporate synthesis of geophysical, geochemical, and petrological constraints on magma generation and emplacement in order to discriminate between tectonic and mantle geodynamic controls on the geological record of a newly forming magmatic rift. Along-rift changes in extension by magma intrusion and plate stretching, and the three-dimensional focusing of melt where the rift dramatically narrows each influence igneous intrusion, volcanism and subsidence history. In addition, rift obliquity plays an important role in localizing intrusion into the crust beneath en echelon volcanic segments. Along-strike variations in volumes and types of igneous rocks found at rifted margins thus likely carry information about the development of strain during rifting, as well as the physical state of the convecting mantle at the time of breakup.

  7. Morphotectonics of the Tunka rift and its bordering mountains in the Baikal rift system, Russia

    NASA Astrophysics Data System (ADS)

    Shchetnikov, Alexander

    2016-11-01

    The Tunka section of the Baikal rift system presents a uniform alternation of the following neostructural forms: tilted horsts and asymmetrical block uplifts on the northern flank; the central system of the rift valleys; and the arched uplift of the southern flank. This is a standard set of morphostructural elements for the Baikal rift system. The main morphological feature of the Tunka rift is the strong inclination of its floor, ranging from 900 m to 200 km in general elevation above Lake Baikal. Such traits of recent geodynamics as volcanism, thermal activity, and seismicity are also different from other parts of the rift zone. All of these features of the Tunka rift are related to the deep structure of the rift zone. The peculiarities of the neotectonic structure of the Tunka rift, which are clearly expressed morphologically as is typical of the Baikal rift system, as well as its unique features are in accordance with deep geodynamic processes of the region. On the other hand, the development of the rift basin structures of the southwestern area near Baikal is complicated by inversion deformations. Local uplifts followed by deformations of the basin sedimentary cover and inverted morphostructures expressed in relief are fixed against the background of the general subsidence of blocks of the pre-Cenozoic basement grabens. The Tunka rift has repeatedly experienced inversion deformations throughout its history. The last wave of such deformations involved the southwestern region near Baikal in the second half of the late Pleistocene. During the Quaternary, the positive component prevailed in the whole range of vertical movements of the inter-rift and interbasin blocks; since the late Neogene, these structures have experienced a slow but steady uplift, accompanied by their extension at the expense of the bordering basins. The remote influence of the India-Asia collision on the formation of the southwestern section of the Baikal rift system is very significant and

  8. Rifting Attractor Structures in the Baikal Rift System: Location and Effects

    NASA Astrophysics Data System (ADS)

    Klyuchevskii, Anatoly V.

    2014-07-01

    The current geodynamics and tectonophysics of the Baikal rift system (BRS) as recorded in lithospheric stress and strain are discussed in the context of self organization of nonlinear dissipative dynamic systems and nonlinear media. The regional strain field inferred from instrumental seismic moment and fault radius data for almost 70,000 MLH ⩾ 2.0 events of 1968 through 1994 shows a complex pattern with zones of high strain anisotropy in the central part and both flanks of the rift system (the South Baikal, Hovsgöl, and Muya rift basins, respectively). The three zones of local strain anisotropy highs coincide with domains of predominantly vertical stress where earthquakes of different magnitudes are mostly of normal slip geometry. Pulse-like reversals of principal stresses in the high-strain domains appear to be nonlinear responses of the system to subcrustal processes. In this respect, the BRS lithosphere is interpreted in terms of the self organization theory as a geological dissipative system. Correspondingly, the domains of high strain anisotropy and stress change, called rifting attractor structures (RAS), are the driving forces of its evolution. The location and nonlinear dynamics of the rifting attractors have controlled lithospheric stress and strain of the rift system over the period of observations, and the same scenario may have been valid also in the Mesozoic-Cenozoic rifting history. The suggested model of a positive-feedback (fire-like) evolution of nonlinear dynamical systems with rifting attractors opens a new perspective on the current geodynamics and tectonophysics of the Baikal rift system.

  9. Kinematics and Dynamics of Observed Along-Rift Surface Motions in the East African Rift System

    NASA Astrophysics Data System (ADS)

    Stamps, D. S.; Bangerth, W.; Hager, B. H.; Kreemer, C.; Saria, E.

    2015-12-01

    Geodetic observations of Nubian and Somalian plate interiors measure ~E-W divergence across the East African Rift System (EARS), which, in the absence of slab pull forces, is driven by shallow, lithospheric buoyancy and mantle shear tractions. Previous studies indicate the former drives E-W divergence a with minimal role of basal shear. In addition to E-W extension, an increasing number of Global Navigation Satellite System (GNSS) stations within the deforming zones of the EARS detect an along-rift component of motion that is inconsistent with our current understanding of the EARS. In this work we investigate the kinematics and dynamics of these along-rift motions. We first calculate a strain rate and velocity field by fitting bi-cubic Bessel splines to new and existing GNSS observations. We resolve regions of localized compression and transtension within individual rifts that are corroborated by independent seismic and geologic observations. In a second step we test the competing roles of shallow topographic stresses and sub-lithospheric basal shear stresses acting beneath individual rifts where we observe along-rift surface motions using the finite element code ASPECT to solve for Stokes flow in a 3D regional geodynamic model. We compare predicted surface motions and mantle flow directions from our geodynamic simulations with our new continuous deformation model based on GNSS observations. Our work indicates topside driven upper mantle flow directions correspond with anomalous along-rift surface motions in several key locations, but our modeled rheological structure impedes basal shear stresses (<1-3 MPa) from driving surface deformation where we observe along-rift surface motions. This work suggests along-rift surface motions are decoupled from asthenospheric flow.

  10. The mesoproterozoic midcontinent rift system, Lake Superior region, USA

    USGS Publications Warehouse

    Ojakangas, R.W.; Morey, G.B.; Green, J.C.

    2001-01-01

    Exposures in the Lake Superior region, and associated geophysical evidence, show that a 2000 km-long rift system developed within the North American craton ??? 1109-1087 Ma, the age span of the most of the volcanic rocks. This system is characterized by immense volumes of mafic igneous rocks, mostly subaerial plateau basalts, generated in two major pulses largely by a hot mantle plume. A new ocean basin was nearly formed before rifting ceased, perhaps due to the remote effect of the Grenville continental collision to the east. Broad sagging/subsidence, combined with a system of axial half-grabens separated along the length of the rift by accommodation zones, provided conditions for the accumulation of as much as 20 km of volcanic rocks and as much as 10 km of post-rift clastic sediments, both along the rift axis and in basins flanking a central, post-volcanic horst. Pre-rift mature, quartzose sandstones imply little or no uplift prior to the onset of rift volcanism. Early post-rift red-bed sediments consist almost entirely of intrabasinally derived volcanic sediment deposited in alluvial fan to fluvial settings; the exception is one gray to black carbon-bearing lacustrine(?) unit. This early sedimentation phase was followed by broad crustal sagging and deposition of progressively more mature red-bed, fluvial sediments with an extra-basinal provenance. ?? 2001 Elsevier Science B.V. All rights reserved.

  11. Geophysical glimpses into the Ferrigno Rift at the northwestern tip of the West Antarctic Rift System

    NASA Astrophysics Data System (ADS)

    Bingham, Robert; Ferraccioli, Fausto

    2014-05-01

    The West Antarctic Rift System (WARS) forms one of the largest continental rift systems on Earth. The WARS is of major significance as it forms the lithospheric cradle for the marine-based and potentially unstable West Antarctic Ice Sheet (WAIS). Seismic refraction, reflection, aeromagnetic, gravity and drilling in the Ross Sea have revealed most of what we know about its structure, tectonic and magmatic patterns and sedimentary basins. Aerogeophysical research and passive seismic networks have considerably extended our knowledge of the WARS and its influence on the overlying WAIS in the Siple Coast and Amundsen Sea Embayment (ASE) regions. The Bellingshausen Sea Embayment region has however remained largely unexplored, and hence the possible extent of the WARS in this sector has remained poorly constrained. Here we use a combination of reconnaissance ground-based and airborne radar observations, airborne gravity, satellite gravity and aeromagnetic data to investigate the WARS in the Bellingshausen Sea Embayment, in the area of the Ferrigno Ice Stream (Bingham et al., 2012, Nature). This region is of high significance, as it one of the main sectors of the WAIS that is currently exhibiting rapid ice loss, thought to be driven primarily by oceanic warming. Assessing geological controls on subice topography and ice dynamics is therefore of prime importance in this part of the WAIS. Ground-based and airborne radar image a subglacial basin beneath the Ferrigno Ice Stream that is up to 1.5 kilometres deep and that connects the ice-sheet interior to the Bellingshausen Sea margin. We interpret this basin as a narrow, glacially overdeepened rift basin that formed at the northwestern tip of the WARS. Satellite gravity data cannot resolve such a narrow rift basin but indicate that the crust beneath the region is likely thinned, lending support to the hypothesis that this area is indeed part of the WARS. Widely-spaced aeromagnetic data image a linear low along the inferred

  12. Geochemical evidence for pre- and syn-rifting lithospheric foundering in the East African Rift System

    NASA Astrophysics Data System (ADS)

    Nelson, W. R.; Furman, T.; Elkins-Tanton, L. T.

    2015-12-01

    The East African Rift System (EARS) is the archetypal active continental rift. The rift branches cut through the elevated Ethiopian and Kenyan domes and are accompanied by a >40 Myr volcanic record. This record is often used to understand changing mantle dynamics, but this approach is complicated by the diversity of spatio-temporally constrained, geochemically unique volcanic provinces. Various sources have been invoked to explain the geochemical variability across the EARS (e.g. mantle plume(s), both enriched and depleted mantle, metasomatized or pyroxenitic lithosphere, continental crust). Mantle contributions are often assessed assuming adiabatic melting of mostly peridotitic material due to extension or an upwelling thermal plume. However, metasomatized lithospheric mantle does not behave like fertile or depleted peridotite mantle, so this model must be modified. Metasomatic lithologies (e.g. pyroxenite) are unstable compared to neighboring peridotite and can founder into the underlying asthenosphere via ductile dripping. As such a drip descends, the easily fusible metasomatized lithospheric mantle heats conductively and melts at increasing T and P; the subsequent volcanic products in turn record this drip magmatism. We re-evaluated existing data of major mafic volcanic episodes throughout the EARS to investigate potential evidence for lithospheric drip foundering that may be an essential part of the rifting process. The data demonstrate clearly that lithospheric drip melting played an important role in pre-flood basalt volcanism in Turkana (>35 Ma), high-Ti "mantle plume-derived" flood basalts and picrites (HT2) from NW Ethiopia (~30 Ma), Miocene shield volcanism on the E Ethiopian Plateau and in Turkana (22-26 Ma), and Quaternary volcanism in Virunga (Western Rift) and Chyulu Hills (Eastern Rift). In contrast, there is no evidence for drip melting in "lithosphere-derived" flood basalts (LT) from NW Ethiopia, Miocene volcanism in S Ethiopia, or Quaternary

  13. Metallogeny of the midcontinent rift system of North America

    USGS Publications Warehouse

    Nicholson, S.W.; Cannon, W.F.; Schulz, K.J.

    1992-01-01

    The 1.1 Ga Midcontinent rift system of North America is one of the world's major continental rifts and hosts a variety of mineral deposits. The rocks and mineral deposits of this 2000 km long rift are exposed only in the Lake Superior region. In the Lake Superior region, the rift cuts across Precambrian basement terranes ranging in age from ??? 1850 Ma to more than 3500 Ma. Where exposed, the rift consists of widespread tholeiitic basalt flows with local interlayered rhyolite and clastic sedimentary rocks. Beneath the center of Lake Superior the volcanic and sedimentary rocks are more than 30 km deep as shown by recent seismic reflection profiles. This region hosts two major classes of mineral deposits, magmatic and hydrothermal. All important mineral production in this region has come from hydrothermal deposits. Rift-related hydrothermal deposits include four main types: (1) native copper deposits in basalts and interflow sediments; (2) sediment-hosted copper sulfide and native copper; (3) copper sulfide veins and lodes hosted by rift-related volcanic and sedimentary rocks; and (4) polymetallic (five-element) veins in the surrounding Archean country rocks. The scarcity of sulfur within the rift rocks resulted in the formation of very large deposits of native metals. Where hydrothermal sulfides occur (i.e., shale-hosted copper sulfides), the source of sulfur was local sedimentary rocks. Magmatic deposits have locally supported exploration and minor production, but most are subeconomic presently. These deposits occur in intrusions exposed near the margins of the rift and include CuNiPGE and TiFe (V) in the Duluth Complex, U-REE-Nb in small carbonatites, and breccia pipes resulting from local hydrothermal activity around small felsic intrusions. Mineralization associated with some magmatic bodies resulted from the concentration of incompatible elements during fractional crystallization. Most of the sulfide deposits in intrusions, however, contain sulfur derived from

  14. The Midcontinent rift system in Kansas

    SciTech Connect

    Berendsen, P. . Kansas Geological Survey)

    1993-03-01

    A sequence of rift-related mafic volcanic rocks, volcanoclastic-, and clastic sedimentary rocks are recognized in cuttings and cores from about seventy wells in Kansas. The age (1,097.5 Ma) for gabbro in the Poersch [number sign]1 well in northern Kansas, as well as the general petrographic characteristics of the sedimentary rocks throughout the area favors a correlation with established Keweenawan stratigraphy in the Lake Superior region. Rift-related northeast-trending faults and older northwest-trending faults divide the area up into a number of orthogonal fault blocks or basins. Depending upon the tectonic history of the individual basin all or part of the Keweenawan section may be preserved. It is believed that large amounts of Keweenawan clastic sedimentary rock were eroded from the nemaha uplift east of the central graben of the rift and transported in an easterly direction. Prior to deposition of Paleozoic rocks the area was peneplaned. Correlation of various stratigraphic units over any distance is complicated by tectonic activity occurring at several times during the Precambrian and Paleozoic. Stratabound or stratiform deposits can occur both in the Precambrian as well as the overlying Paleozoic rocks. The possibility of massive sulfides to occur in the mafic intrusive rocks must not be excluded. In the core from the Poersch [number sign]1 well sulfides are recognized in gabbroic sills or dikes. Dark, fissile shale, similar to the Nonesuch Shale in the [number sign]1--4 Finn well averages 0.75% organic carbon. Thermal maturation within the rift probably ranges from within the oil window to over maturity.

  15. Turbidite systems of lacustrine rift basins: Examples from the Lake Kivu and Lake Albert rifts, East Africa

    NASA Astrophysics Data System (ADS)

    Zhang, Xuewei; Scholz, Christopher A.

    2015-07-01

    The Holocene turbidite systems of Lake Kivu and the Pliocene turbidite systems of Lake Albert in the East African Rift were examined using high-resolution 2-D and 3-D seismic reflection data and sediment core information. Based on investigations of seismic facies and lithofacies, several key turbidity-flow depositional elements were observed, including channels, overbank levees with sediment waves, and depositional lobes. Analyses of the sources of the recent and ancient turbidite systems in these two extensional basins suggest that flood-induced hyperpycnal flows are important triggers of turbidity currents in lacustrine rift basins. From source to sink, sediment dispersal, facies distribution, and depositional thickness of the turbidite systems are strongly influenced by rift topography. The Lake Kivu and Lake Albert rifts serve as excellent analogues for understanding the sedimentary patterns of lacustrine turbidites in extensional basins.

  16. Magmatic lithospheric heating and weakening during continental rifting: A simple scaling law, a 2-D thermomechanical rifting model and the East African Rift System

    NASA Astrophysics Data System (ADS)

    Schmeling, Harro; Wallner, Herbert

    2012-08-01

    Continental rifting is accompanied by lithospheric thinning and decompressional melting. After extraction, melt is intruded at shallower depth thereby heating and weakening the lithosphere. In a feedback mechanism this weakening may assist rifting and melt production. A one-dimensional kinematic lithospheric thinning model is developed including decompressional melting and intrusional magma deposition. The intrusional heating effect is determined as a function of thinning rate and amount, melting parameters, potential temperature, and the depth range of emplacement. The temperature increases approximately proportionally to the square root of the thinning rate and to the square of the supersolidus potential temperature. Simple scaling laws are derived allowing predicting these effects and the surface heat flux for arbitrary scenarios. Two-dimensional thermomechanical extension models are carried out for a multicomponent (crust-mantle) two-phase (melt-matrix) system with a rheology based on laboratory data including magmatic weakening. In good agreement with the 1-D kinematic models it is found that the lithosphere may heat up by several 100 K. This heating enhances viscous weakening by one order of magnitude or more. In a feedback mechanism rifting is dynamically enforced, leading to a significant increase of rift induced melt generation. Including the effect of lateral focusing of magma toward the rift axis the laws are applied to different segments of the East African Rift System. The amount of intrusional heating increases with maturity of the rift from O(10 K) to up to 200 K or 400 K at the Afar Rift depending on the depth range of the magmatic emplacement.

  17. Petroleum system of the Shelf Rift Basin, East China Sea

    SciTech Connect

    Cunningham, A.C.; Armentrout, J.M.; Prebish, M.

    1996-12-31

    The Tertiary section of the Oujioang and Quiontang Depressions of the East China Sea Basin consists of at least eight rift-related depositional sequences identified seismically by regionally significant onlap and truncation surfaces. These sequences are calibrated by several wells including the Wenzhou 6-1-1 permitting extrapolation of petroleum system elements using seismic facies analysis. Gas and condensate correlated to non-marine source rocks and reservoired in sandstone at the Pinghu field to the north of the study area provides an known petroleum system analogue. In the Shelf Rift Basin, synrift high-amplitude parallel reflections within the graben axes correlate with coaly siltstone strata and are interpreted as coastal plain and possibly lacustrine facies with source rock potential. Synrift clinoform seismic facies prograding from the northwest footwall correlate with non-marine to marginal marine conglomerate, sandstone and siltstone, and are interpreted as possible delta or fan-delta facies with reservoir potential although porosity and permeability is low within the Wenzhou 6-1-1 well. Post-rift thermal sag sequences are characterized by parallel and relatively continuous seismic reflections and locally developed clinoform packages. These facies correlate with porous and permeable marine sandstone and siltstone. Shales of potential sealing capacity occur within marine flooding intervals of both the synrift and post-rift sequences. Traps consist of differentially rotated synrift fill, and post-rift inversion anticlines. Major exploration risk factors include migration from the synrift coaly source rocks to the post-rift porous and permeable sandstones, and seismic imaging and drilling problems associated with extensive Tertiary igneous intrusions.

  18. Petroleum system of the Shelf Rift Basin, East China Sea

    SciTech Connect

    Cunningham, A.C.; Armentrout, J.M.; Prebish, M. )

    1996-01-01

    The Tertiary section of the Oujioang and Quiontang Depressions of the East China Sea Basin consists of at least eight rift-related depositional sequences identified seismically by regionally significant onlap and truncation surfaces. These sequences are calibrated by several wells including the Wenzhou 6-1-1 permitting extrapolation of petroleum system elements using seismic facies analysis. Gas and condensate correlated to non-marine source rocks and reservoired in sandstone at the Pinghu field to the north of the study area provides an known petroleum system analogue. In the Shelf Rift Basin, synrift high-amplitude parallel reflections within the graben axes correlate with coaly siltstone strata and are interpreted as coastal plain and possibly lacustrine facies with source rock potential. Synrift clinoform seismic facies prograding from the northwest footwall correlate with non-marine to marginal marine conglomerate, sandstone and siltstone, and are interpreted as possible delta or fan-delta facies with reservoir potential although porosity and permeability is low within the Wenzhou 6-1-1 well. Post-rift thermal sag sequences are characterized by parallel and relatively continuous seismic reflections and locally developed clinoform packages. These facies correlate with porous and permeable marine sandstone and siltstone. Shales of potential sealing capacity occur within marine flooding intervals of both the synrift and post-rift sequences. Traps consist of differentially rotated synrift fill, and post-rift inversion anticlines. Major exploration risk factors include migration from the synrift coaly source rocks to the post-rift porous and permeable sandstones, and seismic imaging and drilling problems associated with extensive Tertiary igneous intrusions.

  19. Geophysical studies of the West Antarctic Rift System

    NASA Astrophysics Data System (ADS)

    Behrendt, J. C.; Lemasurier, W. E.; Cooper, A. K.; Tessensohn, F.; TréHu, A.; Damaske, D.

    1991-12-01

    The West Antarctic rift system extends over a 3000 × 750 km, largely ice covered area from the Ross Sea to the base of the Antarctic Peninsula, comparable in area to the Basin and Range and the East African rift system. A spectacular rift shoulder scarp along which peaks reach 4-5 km maximum elevation marks one flank and extends from northern Victoria Land-Queen Maud Mountains to the Ellsworth-Whitmore-Horlick Mountains. The rift shoulder has maximum present physiographic relief of 5 km in the Ross Embayment and 7 km in the Ellsworth Mountains-Byrd Subglacial Basin area. The Transantarctic Mountains part of the rift shoulder (and probably the entire shoulder) has been interpreted as rising since about 60 Ma, at episodic rates of ˜1 km/m.y., most recently since mid-Pliocene time, rather than continuously at the mean rate of 100 m/m.y. The rift system is characterized by bimodal alkaline volcanic rocks ranging from at least Oligocene to the present. These are exposed asymmetrically along the rift flanks and at the south end of the Antarctic Peninsula. The trend of the Jurassic tholeiites (Ferrar dolerites, Kirkpatric basalts) marking the Jurassic Transantarctic rift is coincident with exposures of the late Cenozoic volcanic rocks along the section of the Transantarctic Mountains from northern Victoria Land to the Horlick Mountains. The Cenozoic rift shoulder diverges here from the Jurassic tholeiite trend, and the tholeiites are exposed continuously (including the Dufek intrusion) along the lower- elevation (1-2 km) section of Transantarctic Mountains to the Weddell Sea. Widely spaced aeromagnetic profiles in West Antarctica indicate the absence of Cenozoic volcanic rocks in the ice covered part of the Whitmore-Ellsworth-Mountain block and suggest their widespread occurrence beneath the western part of the ice sheet overlying the Byrd Subglacial Basin. A German Federal Institute for Geosciences and Natural Resources (BGR)-U.S. Geological Survey (USGS) aeromagnetic

  20. Rifting, Volcanism, and the Geochemical Character of the Mantle Beneath the West Antarctic Rift System (Invited)

    NASA Astrophysics Data System (ADS)

    Mukasa, S. B.; Aviado, K. B.; Rilling-Hall, S.; Bryce, J. G.; Cabato, J.

    2013-12-01

    The West Antarctic Rift System (WARS) is one of the largest extensional alkali volcanic provinces on Earth, but the mechanisms responsible for generating the massive amounts of its associated magmatism remain controversial. The failure of both passive and active decompression melting models to adequately explain the observed lava volumes has prompted debate about the relative roles of thermal plume-related melting and ancient subduction-related flux melting. 40Ar/39Ar dating and geochemical analyses of the lavas, as well as volatile and trace-element determinations of olivine-hosted melt inclusions shed light on the relationship between rifting and volcanism, and also improve our understanding of the geochemical character of the mantle beneath the WARS. Results show that the magmatism post-dates the main phase of extension along the Terror Rift within the WARS, which supports a decompression-melting model without the benefit of a significant thermal anomaly. However, the observed large magma volumes seem to require a volatile-fluxed mantle, a notion supported by a long history of subduction (>500 Myr) along the paleo-Pacific margin of Gondwana. In fact, the legacy of that subduction may manifest itself in the high H2O concentrations of olivine-hosted melt inclusions (up to 3 wt% in preliminary results from ion probe measurements). The major oxide compositions of lavas in the WARS are best matched to experimental melts of garnet pyroxenite and carbonated peridotite sources. The Pb and Nd isotopic systems are decoupled from each other, suggesting removal of fluid-mobile elements from the mantle source possibly during the long history of subduction along this Gondwana margin. Extremely unradiogenic 187Os/188Os ranging to as low as 0.1081 × 0.0001 hints at the involvement of lithospheric components in generation of magmas in the WARS.

  1. Innovative tephra studies in the East African Rift System

    NASA Astrophysics Data System (ADS)

    WoldeGabriel, Giday; Hart, William K.; Heiken, Grant

    Geosciences investigations form the foundation for paleoanthropological research in the East African Rift System. However, innovative applications of tephra studies for constraining spatial and temporal relations of diverse geological processes, biostratigraphic records, and paleoenvironmental conditions within the East African Rift System were fueled by paleoanthropological investigations into the origin and evolution of hominids and material culture. Tephra is a collective, size-independent term used for any material ejected during an explosive volcanic eruption.The East African Rift System has become a magnet for paleoanthropological research ever since the discovery of the first hominids at Olduvai Gorge, in Tanzania, in the 1950s [Leakey et al., 1961]. Currently, numerous multidisciplinary scientific teams from academic institutions in the United States and Western Europe make annual pilgrimages for a couple of months to conduct paleoanthropological field research in the fossil-rich sedimentary deposits of the East African Rift System in Ethiopia, Kenya, and Tanzania. The field expedition consists of geological, paleontological, archaeological, and paleoenvironmental investigations.

  2. Mapping of the major structures of the African rift system

    NASA Technical Reports Server (NTRS)

    Mohr, P. A. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. ERTS-1 imagery of the African rift system has already proved of great value in structural geological studies. One of the interesting megastructures expressed on the imagery occurs some 40 km east of the eastern margin of the main Ethiopian rift, in Arussi province, and extending between latitude 71/2 and 81/4 deg N. The Badda-Encuolo ridge proves to have been a line of major Tertiary volcanism and probably supplied the thick Trap Series flood basalt sequence exposed farther east in the canyons of the Webi Shebeli drainage system. The ridge itself was built up by the waning activity of the Sagatu line of volcanism. Serendipitious has been the discovery on Mt. Badda of several deeply glaciated valleys, many of which show clearly on the ERTS-1 imagery. It seems that Mt. Badda was one of the most important glacial centers in eastern Africa during the Pleistocene. Three major late-Tertiary trachytic centers lie between the Badda-Encuolo ridge and the rift valley. The relationships of these three volcanoes to each other and to the rift faulting is revealed for the first time by the ERTS-1 imagery, as is the form of the cladera of Baltata and the crater of Chilalo.

  3. Clastic rocks associated with the Midcontinent rift system in Iowa

    USGS Publications Warehouse

    Anderson, Raymond R.; McKay, Robert M.

    1997-01-01

    The Middle Proterozoic Midcontinent Rift System (MRS) of North America is a failed rift that formed in response to region-wide stresses about 1,100 Ma. In Iowa, the MRS is buried beneath 2,200?3,500 ft of Paleozoic and Mesozoic sedimentary rocks and Quaternary glaciogenic deposits. An extremely large volume of sediments was deposited within basins associated with the rift at several stages during its development. Although the uplift of a rift-axial horst resulted in the erosional removal of most of these clastic rocks from the central region of the MRS in Iowa, thick sequences are preserved in a series of horst-bounding basins. Recent studies incorporating petrographic analysis, geophysical modeling, and other analytical procedures have led to the establishment of a preliminary stratigraphy for these clastic rocks and interpretations of basin geometries. This information has allowed the refinement of existing theories and history of MRS formation in Iowa. Additionally, drill samples previously interpreted as indicating the existence of early Paleozoic basins overlying the Proterozoic MRS basins were re-examined. Samples previously interpreted as deep-lying Paleozoic rocks are now known to have caved from upper levels of the drillhole and were out of stratigraphic position. No deep Paleozoic basins exist in this area. These investigations led to the development of petrographic parameters useful in differentiating the Proterozoic MRS Red clastics from Paleozoic clastic rocks having similar lithologies.

  4. Ouachita trough: Part of a Cambrian failed rift system

    NASA Astrophysics Data System (ADS)

    Lowe, Donald R.

    1985-11-01

    Pre-flysch (Cambrian-Mississippian) strata of the Ouachita Mountains of Arkansas and Oklahoma include two main sandstone lithofacies: (1) a craton-derived lithofacies made up largely of mature medium- to coarse-grained quartzose and carbonate detritus and, in some units, sediment eroded from exposed basement rocks and (2) an orogen-derived facies made up mainly of fine-grained quartzose sedimentary and metasedimentary debris and possibly, in lower units, a volcaniclastic component. Paleocurrent and distribution patterns indicate that detritus of facies I in the Benton uplift was derived from north and detritus of facies II throughout the Ouachitas was derived from south and east of the depositional basin. Overall sedimentological results suggest that the Ouachita trough was a relatively narrow, two-sided basin throughout most and probably all of its existence and never formed the southern margin of the North American craton. Regional comparisons suggest that it was one of several basins, including the Southern Oklahoma aulacogen, Reelfoot Rift, Illinois Basin, and Rome trough, that formed as a Cambrian failed rift system 150 to 250 m.y. after initial rifting along the Appalachian margin of the North American craton.

  5. Benue trough and the mid-African rift system

    SciTech Connect

    Thomas, D.

    1996-01-29

    Large areas of the Anambra and Gongola basins have distinct petroleum exploration problems: a geologically persistent high geothermal gradient that promoted Cretaceous source rock maturation into the gas phase very early on; intrusive lead-zinc mineralization veins attributed to the Senonian igneous and folding event; and meteoric water-flushing along the periphery of the basins. From preliminary analysis, these basins have to be considered high risk for the discovery of commercial oil accumulations. On the other hand, the petroleum potential of the Bornu basins seems favorable. This Nigerian northernmost rift basin continues into the Kanem basin of western Chad, which has proven oil accumulations in Coniacian deltaic sands. Cretaceous paleofacies is considered to be relatively continuous throughout both basins. Paleo-geothermal history is also considered to be similar, although some igneous activity is recorded in the Bornu basin (Senonian?). There is a very real possibility of kerogen-rich non-marine basal Albo-Aptian basin fill lacustrine source rocks, as found in the Doba basin, could be present in the deepest sections of the Nigerian rift basins. Due to the depths involved, no well is expected to penetrate the incipient graben-fill stage sequences; however, possible oil migration from these tectono-stratigraphic units would certainly enhance the petroleum potential of cooler sections of the rift system. As opposed to interpreted thermogenic gas which seems to be prevalent in the Anambra basin.

  6. Hydrothermal vents is Lake Tanganyika, East African Rift system

    SciTech Connect

    Tiercelin, J.J.; Pflumio, C.; Castrec, M.

    1993-06-01

    Sublacustrine hydrothermal vents with associated massive sulfides were discovered during April 1987 at Pemba and Cape Banza on the Zaire side of the northern basin of Lake Tanganyika, East African Rift system. New investigations by a team of ten scuba divers during the multinational (France, Zaire, Germany, and Burundi) TANGANYDRO expedition (August-October 1991) found hydrothermal vents down to a depth of 46 m along north-trending active faults bounding the Tanganyika rift on the western side. Temperatures from 53 to 103 {degrees}C were measured in hydrothermal fluids and sediments. Veins of massive sulfides 1-10 cm thick (pyrite and marcasite banding) were found associated with vents at the Pemba site. At Cape Banza, active vents are characterized by 1-70-cm-high aragonite chimneys, and there are microcrystalline pyrite coatings on the walls of hydrothermal pipes. Hydrothermal fluid end members show distinctive compositions at the two sites. The Pemba end member is a NaHCO{sub 3}-enriched fluid similar to the NaHCO{sub 3} thermal fluids form lakes Magadi and Bogoria in the eastern branch of the rift. The Cape Banza end member is a solution enriched in NaCl. Such brines may have a deep-seated basement origin, as do the Uvinza NaCl brines on the eastern flank of the Tanganyika basin. Geothermometric calculations have yielded temperatures of fluid-rock interaction of 219 and 179 {degrees}C in the Pemba and Cape Banza systems, respectively. Abundant white or reddish-brown microbial colonies resembling Beggiatoa mats were found surrounding the active vents. Thermal fluid circulation is permitted by opening of cracks related to 130{degrees}N normal-dextral faults that intersect the north-south major rift trend. The sources of heat for such hydrothermal systems may relate to the existence of magmatic bodies under the rift, which is suggested by the isotopic composition of carbon dioxide released at Pemba and Cape Banza. 21 refs., 2 figs.

  7. Sedimentology of rift climax deep water systems; Lower Rudeis Formation, Hammam Faraun Fault Block, Suez Rift, Egypt

    NASA Astrophysics Data System (ADS)

    Leppard, Christopher W.; Gawthorpe, Rob L.

    2006-09-01

    In most marine rift basins, subsidence outpaces sedimentation during rift climax times. Typically this results in sediment-starved hangingwall depocentres dominated by deep-marine mudstones, with subordinate local development of coarser clastics in the immediate hangingwall derived from restricted catchments on the immediate footwall scarp. To highlight the spatial variability of rift climax facies and the controls upon them, we have investigated the detailed three-dimensional geometry and facies relationships of the extremely well exposed Miocene, rift climax Lower Rudeis Formation in the immediate hangingwall to the Thal Fault Zone, Suez Rift, Egypt. Detailed sedimentological analyses allows the Lower Rudeis Formation to be divided into two contemporaneous depositional systems, (1) a laterally continuous slope system comprising, hangingwall restricted (< 250 m wide) slope apron, slope slumps, fault scarp degradation complex and laterally extensive lower slope-to-basinal siltstones, and (2) a localized submarine fan complex up to 1 km wide and extending at least 2 km basinward of the fault zone. Interpretation of individual facies, facies relationships and their spatial variability indicate that deposition in the immediate hangingwall to the Thal Fault occurred via a range of submarine concentrated density flows, surge-like turbidity flows, mass wasting and hemipelagic processes. Major controls on the spatial variability and stratigraphic architecture of the depositional systems identified reflect the influence of the steep footwall physiography, accommodation and drainage evolution associated with the growth of the Thal Fault. The under-filled nature of the hangingwall depocentre combined with the steep footwall gradient result in a steep fault-controlled basin margin characterised by either slope bypass or erosion, with limited coastal plain or shelf area. Sediment supply to the slope apron deposits is controlled in part by the evolution and size of small

  8. The Lake Albert Rift (uganda, East African Rift System): Deformation, Basin and Relief Evolution Since 17 Ma

    NASA Astrophysics Data System (ADS)

    Brendan, Simon; François, Guillocheau; Cécile, Robin; Olivier, Dauteuil; Thierry, Nalpas; Martin, Pickford; Brigitte, Senut; Philippe, Lays; Philippe, Bourges; Martine, Bez

    2016-04-01

    .5 Ma: Rift stage 1 (subsidence rate: > 500m/Ma up to 600-800 m/Ma; sedimentation rate: 2.4 km3/Ma) - Rifting climax; - 2.5-0.4 Ma: uplift of the Ruwenzori Mountains and shifting from an alluvial system to a network of bedrock river incision - Rift Stage 2 (subsidence rate: 450 to 250 m/Ma; sedimentation rate: 1.5 km3/Ma); - 0.4-0 Ma: long wavelength downwarping of the Tanzanian Craton, initiation of the Lake Victoria trough, drainage network inversion and uplift of the present-day Ugandan escarpment (normal faulting motion of the border faults) with formation of perched valleys associated to the Lower Pleistocene (2.5-0.4 Ma) rivers network. At larger scale, comparison of the Lake Albert Rift evolution with the data available in the basins of both eastern and western branches of the East African Rift System shows that most of the sedimentary basins experienced the same geometrical evolution from large basins with limited fault controls during Late Miocene to narrow true rift in Late Pleistocene (e.g. Northern and Central Kenyan Basins), in agreement with the volcanism distribution, large (width >100 km) during the Miocene times, narrower (width x10 km) from Late Pliocene to Pleistocene times and today limited to narrow rifts.

  9. Geochronological and geochemical assessment of Cenozoic volcanism from the Terror Rift region of the West Antarctic Rift System

    NASA Astrophysics Data System (ADS)

    Rilling, Sarah E.

    The work presented in this dissertation explains results from three different methods to determine the relation between tectonism and rift-related volcanism in the Terror Rift region of the West Antarctic Rift System (WARS). Alkaline lavas from seven submarine features, Beaufort Island and Franklin Islands, and several locations near Mt Melbourne were dated by 40Ar/39Ar geochronology and analyzed for elemental and isotopic chemical signatures. Each chapter addresses a different aspect of the hypothesis that the presence of volatiles, primarily H2O or CO2, in the magma source has led to anomalously high volumes of magmatism after rift-related decompressional melting rather than requiring an active mantle plume source. Chapter 2 provides the temporal framework, illustrating that the sampled features range in age from 6.7 Ma to 89 ka, post-dating the main Miocene age phase of Terror Rift extension. Chapter 3 illustrates the traditional enriched elemental and isotopic chemical signatures to support the overall homogeneity of these lavas and previously analyzed areas of the WARS. This chapter also provides a new model for the generation of the Pb isotopic signatures consistent with a history of metasomatism in the magma source. Chapter 4 provides an entirely new chemical dataset for the WARS. The first platinum group element (PGE) abundances and extremely unradiogenic Os isotopic signatures of Cenozoic lavas from Antarctica provide the strongest evidence of melting contributions from a lithospheric mantle source. The combined results from these three studies consistently support the original hypothesis of this dissertation. New evidence suggests that WARS related lavas are not related to a mantle plume(s) as previously proposed. Instead, they are generated by passive, decompressional melting of a source, likely a combination of the asthenospheric and lithospheric mantle, which has undergone previous melting events and metasomatism.

  10. The East African rift system in the light of KRISP 90

    USGS Publications Warehouse

    Keller, Gordon R.; Prodehl, C.; Mechie, J.; Fuchs, K.; Khan, M.A.; Maguire, Peter K.H.; Mooney, W.D.; Achauer, U.; Davis, P.M.; Meyer, R.P.; Braile, L.W.; Nyambok, I.O.; Thompson, G.A.

    1994-01-01

    On the basis of a test experiment in 1985 (KRISP 85) an integrated seismic-refraction/teleseismic survey (KRISP 90) was undertaken to study the deep structure beneath the Kenya rift down to depths of 100-150 km. This paper summarizes the highlights of KRISP 90 as reported in this volume and discusses their broad implications as well as the structure of the Kenya rift in the general framework of other continental rifts. Major scientific goals of this phase of KRISP were to reveal the detailed crustal and upper mantle structure under the Kenya rift, to study the relationship between mantle updoming and the development of sedimentary basins and other shallow structures within the rift, to understand the role of the Kenya rift within the Afro-Arabian rift system and within a global perspective and to elucidate fundamental questions such as the mode and mechanism of continental rifting. The KRISP results clearly demonstrate that the Kenya rift is associated with sharply defined lithospheric thinning and very low upper mantle velocities down to depths of over 150 km. In the south-central portion of the rift, the lithospheric mantle has been thinned much more than the crust. To the north, high-velocity layers detected in the upper mantle appear to require the presence of anistropy in the form of the alignment of olivine crystals. Major axial variations in structure were also discovered, which correlate very well with variations in the amount of extension, the physiographic width of the rift valley, the regional topography and the regional gravity anomalies. Similar relationships are particularly well documented in the Rio Grande rift. To the extent that truly comparable data sets are available, the Kenya rift shares many features with other rift zones. For example, crustal structure under the Kenya, Rio Grande and Baikal rifts and the Rhine Graben is generally symmetrically centered on the rift valleys. However, the Kenya rift is distinctive, but not unique, in terms of

  11. Rift-wide correlation of 1.1 Ga Midcontinent rift system basalts: Implications for multiple mantle sources during rift development

    USGS Publications Warehouse

    Nicholson, S.W.; Shirey, S.B.; Schulz, K.J.; Green, J.C.

    1997-01-01

    Magmatism that accompanied the 1.1 Ga Midcontinent rift system (MRS) is attributed to the upwelling and decompression melting of a mantle plume beneath North America. Five distinctive flood-basalt compositions are recognized in the rift-related basalt succession along the south shore of western Lake Superior, based on stratigraphically correlated major element, trace element, and Nd isotopic analyses. These distinctive compositions can be correlated with equivalent basalt types in comparable stratigraphic positions in other MRS localities around western Lake Superior. Four of these compositions are also recognized at Mamainse Point more than 200 km away in eastern Lake Superior. These regionally correlative basalt compositions provide the basis for determining the sequential contribution of various mantle sources to flood-basalt magmatism during rift development, extending a model originally developed for eastern Lake Superior. In this refined model, the earliest basalts were derived from small degrees of partial melting at great depth of an enriched, ocean-island-type plume mantle source (??Nd(1100) value of about 0), followed by magmas representing melts from this plume source and interaction with another mantle source, most likely continental lithospheric mantle (??Nd(1100) < 0). The relative contribution of this second mantle source diminished with time as larger degree partial melts of the plume became the dominant source for the voluminous younger basalts (??Nd(1100) value of about 0). Towards the end of magmatism, mixtures of melts from the plume and a depleted asthenospheric mantle source became dominant (??Nd(1100) = 0 to +3).

  12. Tectonics and stratigraphy of the East Brazil Rift system: an overview

    NASA Astrophysics Data System (ADS)

    Hung Kiang Chang; Kowsmann, Renato Oscar; Figueiredo, Antonio Manuel Ferreira; Bender, AndréAdriano

    1992-10-01

    The East Brazilian Rift system (Ebris) constitutes the northern segment of the South Atlantic rift system which developed during the Mesozoic breakup of South America and Africa. Following crustal separation in the Late Aptian, it evolved into a passive continental margin. Along the continental margin six basins are recognized, while three onshore basins form part of an aborted rift. Three continental syn-rift stratigraphic sequences are recognized, spanning Jurassic to Barremian times. The Jurassic (Syn-rift I) and Neocomian (Syn-rift II) phases were most active in the interior rift basins. During the Barremian (Syn-rift III), rift subsidence rates were twice as large as during the Neocomian (Syn-rift II), both in the interior rift and in the marginal rift segments, indicating that rift axis did not migrate from the interior to the marginal setting. Rift magmatism was centered on the southern EBRIS and peaked between 130 and 120 Ma during syn-rift phase II. Rift phase III was followed by a transitional marine, evaporitic megasequence of Aptian age, which directly overlies the rift unconformity and a marine drift megasequence which spans Albian to Recent times. During the Late Cretaceous, sedimentation rates responded to first-order eustatic sea-level fluctuations. Tertiary accelerated sedimentation rates can be related to local clastic supply which filled in spaces inherited from previous starved conditions. Between 60 and 40 Ma, post-rift magmatism, centered on the Abrolhos and Royal Charlotte banks, is probably related to development of a hot spot associated with the Vitória-Trindade Seamount Chain. Although crossing three distinct Precambrian tectono-thermal provinces, ranging from Archean through Late Proterozoic, rift structures follow a general NE trend, subparallel to the principal basement fabric. A NW-SE oriented stress field appears to be compatible with both Neocomian and Barremian phases of crustal extension. Profiles transverse to the rift axis

  13. Beta Regio rift system on Venus: Geologic interpretation of Magellan images

    NASA Technical Reports Server (NTRS)

    Nikishin, A. M.; Bobina, N. N.; Borozdin, V. K.; Burba, G. A.

    1993-01-01

    Magellan SAR images and altimetric data were used to produce a new geologic map of the Northern part of Beta Regio within the frames of C1-30N279 mapsheet. It was part of our contributions into C1-formate geologic mapping efforts. The original map is at 1:8,000,000 scale. The rift structures are typical for Beta Regio on Venus. There are many large uplifted tessera areas on Beta upland. They occupy areas of higher topography. These tessera are partly burried by younger volcanic cover of plain material. These observations show that Beta upland was formed mainly due to lithospheric tectonical uplifting, and only partly was constructed by volcanic activity. A number of rift valleis traverse Beta upland and spread to the surrounding lowlands. The largest rift crosses Beta N to S. Typical width of rifts is 40 to 160 km. Rift valleis in this region are structurally represented by crustal grabens and half-grabens. There are symmetrical and asymmetrical rifts. A lot of them have shoulder uplifts with the relative high up to 0.5-1 km and width 40 to 60 km. Preliminary analysis of the largest rift valley structural cross-sections leads to the conclusion that it originated due to a 5-10 percent crustal extension. The prominent shield volcano - Theia Mons - is located at the center of Beta rift system. It could be considered as the surface manifestation of the upper mantle hot spot. Most of the rift belts are located radially to Theia Mons. The set of these data leads to conclusion that Beta rift system has an 'active-passive' origin. It was formed due to the regional tectonic lithospheric extension. Rifting was accelerated by the upper mantle hot spot located under the center of passive extension (under Beta Regio).

  14. Topographic and Structural Analysis of Devana Chasma, Venus: A Propagating Rift System

    NASA Astrophysics Data System (ADS)

    Kiefer, W. S.; Swafford, L. C.

    2003-12-01

    Devana Chasma is a rift system on Venus that formed due to extensional stresses from the Beta Regio and Phoebe Regio mantle plumes. Devana has often been compared to the East African Rift system on Earth. Here, we focus on the portion of Devana in the lowland plains between Beta and Phoebe, 20 North - 4 South, a distance of 2500 km. Over this region, Devana is typically 150 to 250 km wide. Recent gravity modeling (Kiefer and Peterson, Geophys. Res. Lett., Jan. 2003) demonstrated that most of this segment of the rift is presently underlain by hot, low density mantle material. The rift has a 600 km lateral offset near 8 North latitude, where the gravity results show no evidence for hot mantle. This lead Kiefer and Peterson to propose that Devana is actually two propagating rifts, one propagating southward from Beta Regio and the other propagating northward from Phoebe Regio. As a test of this hypothesis, we have examined the detailed structural geology of this section of the rift using topographic profiles and radar imagery from the Magellan mission. We constructed a series of topographic transects spaced at approximately 50 km intervals along the rift and measured the average flank height and the maximum rift depth. We measured the total vertical offset along faulted surfaces and converted this to horizontal extension assuming a characteristic normal fault dip of 60 degrees. Plots of these quantities as a function of distance along the rift reveals several characteristic zones. Average flank height has maximum values near the edges of Beta Regio (3.5 km) and Phoebe Regio (2.75 km) and decreases rapidly as the rift crosses the intervening plains. This is consistent with the rift forming due to thermal anomalies centered at Beta and Phoebe. The virtual absence of elevated rift flanks in the offset region near 8 North is consistent with the absence of hot mantle in this region, as inferred from the gravity model. The horizontal extension decreases strongly with

  15. Orthorhombic faults system at the onset of the Late Mesozoic-Cenozoic Barents Sea rifting

    NASA Astrophysics Data System (ADS)

    Collanega, Luca; Breda, Anna; Massironi, Matteo

    2016-04-01

    been observed that, in the upper part of the succession, devoid of pre-existing discontinuities and detached from the lower part of the succession by the Upper Triassic shales, the deformation has been accommodated by the newly-formed orthorhombic system; while, in the deeper part of the succession, likely to host pre-existing weakness zones, the deformation has been accommodated through the graben/half-graben system. Hence, during the Late Mesozoic/Cenozoic Barents Sea rifting it seems that the absence of pre-existing discontinuities played a key-role in the development of an orthorhombic fault arrangement in the upper part of the succession rather than a classical plain strain system. Indeed pre-existing discontinuities in the lower part of the succession can focus the deformation, preventing the formation of new faults and in this case favouring a plain strain mode. Furthermore, the Upper Triassic detachment limited the influence of deep structures on the upper part of the succession, allowing initially for the development of an entirely new fault system. As the rifting proceeded, the deep reactivated structures propagated towards the surface and, finally, their activity became predominant on the activity of the orthorhombic system, as indicated by time-thickness maps.

  16. Seismic Migration Imaging of the Lithosphere beneath the Afar Rift System, East Africa

    NASA Astrophysics Data System (ADS)

    Lee, T. T. Y.; Chen, C. W.; Rychert, C.; Harmon, N.

    2015-12-01

    The Afar Rift system in east Africa is an ideal natural laboratory for investigating the incipient continental rifting, an essential component of plate tectonics. The Afar Rift is situated at the triple junction of three rifts, namely the southern Red Sea Rift, Gulf of Aden Rift and Main Ethiopian Rift (MER). The ongoing continental rifting at Afar transitions to seafloor spreading toward the southern Red Sea. The tectonic evolution of Afar is thought to be influenced by a mantle plume, but how the plume affects and interacts with the Afar lithosphere remains elusive. In this study, we use array seismic data to produce high-resolution migration images of the Afar lithosphere from scattered teleseismic wavefields to shed light on the lithospheric structure and associated tectonic processes. Our preliminary results indicate the presence of lithospheric seismic discontinuities with depth variation across the Afar region. Beneath the MER axis, we detect a pronounced discontinuity at 55 km depth, characterized by downward fast-to-slow velocity contrast, which appears to abruptly deepen to 75 km depth to the northern flank of MER. This discontinuity may be interpreted as the lithosphere-asthenosphere boundary. Beneath the Ethiopian Plateau, on the other hand, a dipping structure with velocity increase is identified at 70-90 km depth. Further synthesis of observations from seismic tomography, receiver functions, and seismic anisotropy in the Afar region will offer better understanding of tectonic significance of the lithospheric discontinuities.

  17. Investigation of rifting processes in the Rio Grande Rift using data from an unusually large earthquake swarm. Final report, October 1, 1992--September 30, 1993

    SciTech Connect

    Sanford, A.; Balch, R.; Hartse, H.; House, L.

    1995-03-01

    Because the Rio Grande Rift is one of the best seismically instrumented rift zones in the world, studying its seismicity provides an exceptional opportunity to elucidate the active tectonic processes within continental rifts. Beginning on 29 November 1989, a 15 square km region near Bernardo, NM, produced the strongest and longest lasting sequence of earthquakes in the rift in 54 years. Our research focuses on the Bernardo swarm which occurred 40 km north of Socorro, New Mexico in the axial region of the central Rio Grande rift. Important characteristics concerning hypocenters, fault mechanisms, and seismogenic zones are discussed.

  18. ALVIN investigation of an active propagating rift system, Galapagos 95.5° W

    USGS Publications Warehouse

    Hey, R.N.; Sinton, J.M.; Kleinrock, M.C.; Yonover, R.N.; MacDonald, K.C.; Miller, S.P.; Searle, R.C.; Christie, D.M.; Atwater, T.M.; Sleep, Norman H.; Johnson, H. Paul; Neal, C.A.

    1992-01-01

    ALVIN investigations have defined the fine-scale structural and volcanic patterns produced by active rift and spreading center propagation and failure near 95.5° W on the Galapagos spreading center. Behind the initial lithospheric rifting, which is propagating nearly due west at about 50 km m.y.−1, a triangular block of preexisting lithosphere is being stretched and fractured, with some recent volcanism along curving fissures. A well-organized seafloor spreading center, an extensively faulted and fissured volcanic ridge, develops ~ 10 km (~ 200,000 years) behind the tectonic rift tip. Regional variations in the chemical compositions of the youngest lavas collected during this program contrast with those encompassing the entire 3 m.y. of propagation history for this region. A maximum in degree of magmatic differentiation occurs about 9 km behind the propagating rift tip, in a region of diffuse rifting. The propagating spreading center shows a gentle gradient in magmatic differentiation culminating at the SW-curving spreading center tip. Except for the doomed rift, which is in a constructional phase, tectonic activity also dominates over volcanic activity along the failing spreading system. In contrast to the propagating rift, failing rift lavas show a highly restricted range of compositions consistent with derivation from a declining upwelling zone accompanying rift failure. The lithosphere transferred from the Cocos to the Nazca plate by this propagator is extensively faulted and characterized by ubiquitous talus in one of the most tectonically disrupted areas of seafloor known. The pseudofault scarps, where the preexisting lithosphere was rifted apart, appear to include both normal and propagator lavas and are thus more lithologically complex than previously thought. Biological communities, probably vestimentiferan tubeworms, occur near the top of the outer pseudofault scarp, although no hydrothermal venting was observed.

  19. Influence of heterogeneities within the lithosphere on the deformation pattern of continental rift systems.

    NASA Astrophysics Data System (ADS)

    Philippon, Melody; Thieulot, Cedric; van Wijk, Jolante; Sokoutis, Dimitrios; Willingshofer, Ernst; Cloetingh, Sierd

    2013-04-01

    Understanding how heterogeneities within the lithosphere influence the deformation pattern in continental rifts still remains a challenge and is of real importance to constrain continental break-up. We have selected the Main Ethiopian Rift in East Africa and the Rio Grande Rift in the south-western U.S. These two rifts are perfect natural laboratories to investigate the effect of inherited as they share similar structural characteristics but develop above different kinds of lithosphere-scale heterogeneities. From a structural point of view both rifts show similar length (1000km), width (50 to 70 km) and asymmetry. The Main Ethiopian rift is the NE-SW trending plate boundary between the Nubian and Somalian plates that has been developing for the past 11 Ma above a palaeo-Proterozoic lithospheric-scale weak zone re-heated by the Afar hotspot, whereas the Rio Grande Rift is the eastern "boundary" of the Basin & Range system which has been developing for the past 30 Ma in the frame of a westward-retreating Farallon subduction zone. However, the Rio Grande Rift shows evidence of low angle normal faulting whereas the Main Ethiopian Rift shows steeply dipping (with a mean close to 70°) normal faults. The Main Ethiopian Rift shows larger volume of erupted lavas than the Rio Grande Rift. Combined with a structural analyses of both rifts, we present here a series of 2D cross sections numerical models that allow better understanding of the influence of initial heterogeneities such as 1) the rheological state of the crust; 2) the presence of a crustal-scale to lithospheric-scale discrete weak or strong zone, 3) the effects of the presence of magma. We illustrate that rheological boundaries are not reactivated if the rheological contrast it too high, which is the case of the Rio Grande Rift that developed to the east of the North American Craton within thinned lithosphere. We also illustrate that the width of the weak zone do no have any influence on the exhumation of the

  20. East Antarctic Rift Systems - key to understanding of Gondwana break-up

    NASA Astrophysics Data System (ADS)

    Golynsky, D. A.; Golynsky, A. V.

    2012-04-01

    The results of analysis of radio-echo sounding surveys, the RADARSAT satellite data, magnetic and gravity information give evidence that East Antarctica contains 13 riftogenic systems and/or large linear tectonic structures. Among known and suggested rifts of East Antarctica the Lambert rift has a pivotal position and it manifests oneself as symmetry axis. Six additional systems are revealed on both sides of it and any one of them possesses special features in geologic and geomorphologic aspects. In most cases they inherited the anisotropy of long-lived cratonic blocks. Riftogenic and/or large linear tectonic structures along the East Antarctica coastal regions are distributed with a steady regularity with average distance between them about 650 km. For six (7) structures from 13 (Lambert, Jutulstraumen-Pencksökket, Vestfjella, Mellor-Slessor (Bailey), Wilkes Basin, Gaussberg (?) and Rennick) there is a distinct spatial coupling with trough complexes of the Beacon Supergroup and their subsequent reactivation in Late Jurassic - Permian time when the East Gondwana started break-up. Rift system of the Lambert-Amery Glaciers and Prydz Bay is related to Mesozoic extension events and it inherited structures of Paleozoic grabens. The total length of the rift system exceeds 4000 km of the same scale as largest the World rift belts. The length of the western branch of the Lambert rift that includes the Mellor rift and graben-like structures of the Bailey and Slessor glaciers exceeds 2300 km. Results of radio-echo sounding investigation of the subglacial Aurora Basin allow to suggest that this large basin of sub-meridian extension is underlain by an extensive (> 1000 km) riftogenic structure that is running towards the Transantarctic Mountains where it forms a triple junction with the eastern branch of the Lambert rift and structures of the Wilkes Basin. It is hereby proposed that Aurora-Scott rift is formed by complex system of sub-parallel depressions divided by

  1. CASERTZ aeromagnetic data reveal late Cenozoic flood basalts (?) in the West Antarctic rift system

    USGS Publications Warehouse

    Behrendt, John C.

    1994-01-01

    The late Cenozoic volcanic and tectonic activity of the enigmatic West Antarctic rift system, the least understood of the great active continental rifts, has been suggested to be plume driven. In 1991-1992, as part of the CASERTZ (Corridor Aerogeophysics of the Southeast Ross Transect Zone) program, an ~25 000 km aeromagnetic survey over the ice-covered Byrd subglacial basin shows magnetic "texture' critical to interpretations of the underlying extended volcanic terrane. The aeromagnetic data reveal numerous semicircular anomalies ~100-1100 nT in amplitude, interpreted as having volcanic sources at the base of the ice sheet; they are concentrated along north-trending magnetic lineations interpreted as rift fabric. The CASERTZ aeromagnetic results, combined with >100 000 km of widely spaced aeromagnetic profiles, indicate at least 106 km3 of probable late Cenozoic volcanic rock (flood basalt?) in the West Antarctic rift beneath the ice sheet and Ross Ice Shelf. -from Authors

  2. Structural geology of the African rift system: Summary of new data from ERTS-1 imagery. [Precambrian influence

    NASA Technical Reports Server (NTRS)

    Mohr, P. A.

    1974-01-01

    ERTS imagery reveals for the first time the structural pattern of the African rift system as a whole. The strong influence of Precambrian structures on this pattern is clearly evident, especially along zones of cataclastic deformation, but the rift pattern is seen to be ultimately independent in origin and nature from Precambrian tectonism. Continuity of rift structures from one swell to another is noted. The widening of the Gregory rift as its northern end reflects an underlying Precambrian structural divergence, and is not a consequence of reaching the swell margin. Although the Western Rift is now proven to terminate at the Aswa Mylonite Zone, in southern Sudan, lineaments extend northeastwards from Lake Albert to the Eastern Rift at Lake Stefanie. The importance of en-echelon structures in the African rifts is seen to have been exaggerated.

  3. Genetic features of petroleum systems in rift basins of eastern China

    USGS Publications Warehouse

    Qiang, J.; McCabe, P.J.

    1998-01-01

    Most oil-bearing basins in eastern China are Mesozoic-Cenozoic continental rifts which have played a habitat for oil and gas in China. Investigation of the petroleum systems may give a better understanding of the oil and gas habitats in these basins. Of the essential elements of the petroleum system, the source rock is the most important in rift basins. However, rift tectonic evolution controls all the essential elements and processes nevessary for a petroleum system. A four stage evolution model is suggested for the controls in the rift basin. A rift basin may consist of sub-basins, depressions, sub-depressions, and major, moderate, and minor uplifts. A depression or sub-depression has its own depocentre (mainly occupied by source rock) and all kinds of lacustrine sediments, and thus has all the essential elements of a petroleum system. However, only those depressions or sub-depressions which are rich in organic matter and deeply buried to generate oil and gas form petroleum systems. Immature oil, another characteristic, complicates the petroleum system in the rift basins. Three types of oil and gas habitats are described as a result of this analysis of the petroleum systems of the 26 largest oil and gas fields discovered in eastern China rift basins: uplifts between oil source centres are the most prospective areas for oil and gas accumulations, slopes connecting oil source centres and uplifts are the second, and the third type is subtle traps in the soil source centre.Most oil-bearing basins in eastern China are Mesozoic-Cenozoic continental rifts which have played a habitat for oil and gas in China. Investigation of the petroleum systems may give a better understanding of the oil and gas habitats in these basins. Of the essential elements of the petroleum system, the source rock is the most important in rift basins. However, rift tectonic evolution controls all the essential elements and processes necessary for a petroleum system. A four stage evolution model

  4. Feedback between magmatic, tectonic and glacial processes in the West Antarctic Rift System (Invited)

    NASA Astrophysics Data System (ADS)

    Rocchi, S.

    2010-12-01

    swarms related to the main NW-SE discontinuities. (3) From the late Miocene to Present, the mantle flow led to normal faulting of the collapsing rift shoulder, which favored the rise of magmas building up large volcanoes along N-S normal-transtensional faults. This evolution of the WARS tectonic-magmatic activity is coeval with the main episodes of ice sheet development in Antarctica. The two main episodes of climate worsening, at the Eocene-Oligocene and early-mid Miocene transitions, were alternated with advances and retreats of ice sheets, with significant volume and thickness changes, that could be invoked as effective in triggering magma generation. It is thus possible to envisage a feedback system involving the WARS Cenozoic geological processes. The strike-slip rift regime affects magma genesis as well as segmentation and uplift of the Transantarctic Mountains (geodynamic forcing on magmatism and tectonics). Surface uplift affects landscape and temperature (tectonic forcing on environment). Mountainous landscape triggers glaciation (geomorphological forcing on climate), and climate affects temperature, hence erosive potential of glaciers (climate forcing on environment). Finally, ice load-unload cycles could affect magma genesis (glacial forcing on magmatism).

  5. Littoral sedimentation of rift lakes: an illustrated overview from the modern to Pliocene Lake Turkana (East African Rift System, Kenya)

    NASA Astrophysics Data System (ADS)

    Schuster, Mathieu; Nutz, Alexis

    2015-04-01

    Existing depositional models for rift lakes can be summarized as clastics transported by axial and lateral rivers, then distributed by fan-deltas and/or deltas into a standing water body which is dominated by settling of fine particles, and experiencing occasional coarser underflows. Even if known from paleolakes and modern lakes, reworking of clastics by alongshore drift, waves and storms are rarely considered in depositional models. However, if we consider the lake Turkana Basin (East African Rift System, Kenya) it is obvious that this vision is incomplete. Three representative time slices are considered here: the modern Lake Turkana, the Megalake Turkana which developed thanks to the African Humid Period (Holocene), and the Plio-Pleistocene highstand episodes of paleolake Turkana (Nachukui, Shungura and Koobi Fora Formations, Omo Group). First, remarkable clastic morphosedimentary structures such as beach ridges, spits, washover fans, lagoons, or wave-dominated deltas are very well developed along the shoreline of modern lake Turkana, suggesting strong hydrodynamics responsible for a major reworking of the fluvial-derived clastics all along the littoral zone (longshore and cross-shore transport) of the lake. Similarly, past hydrodynamics are recorded from prominent raised beach ridges and spits, well-preserved all around the lake, above its present water-level (~360 m asl) and up to ~455 m. These large-scale clastic morphosedimentary structures also record the maximum extent of Megalake Turkana during the African Humid Period, as well as its subsequent regression forced by the end of the Holocene climatic optimum. Several hundreds of meters of fluvial-deltaic-lacustrine deposits spanning the Pliocene-Pleistocene are exposed in the Turkana basin thanks to tectonic faulting. These deposits are world famous for their paleontological and archeological content that documents the very early story of Mankind. They also preserve several paleolake highstand episodes with

  6. Plate kinematics of the Afro-Arabian Rift System with emphasis on the Afar Depression, Ethiopia

    NASA Astrophysics Data System (ADS)

    Bottenberg, Helen Carrie

    This work utilizes the Four-Dimensional Plates (4DPlates) software, and Differential Interferometric Synthetic Aperture Radar (DInSAR) to examine plate-scale, regional-scale and local-scale kinematics of the Afro-Arabian Rift System with emphasis on the Afar Depression in Ethiopia. First, the 4DPlates is used to restore the Red Sea, the Gulf of Aden, the Afar Depression and the Main Ethiopian Rift to development of a new model that adopts two poles of rotation for Arabia. Second, the 4DPlates is used to model regional-scale and local-scale kinematics within the Afar Depression. Most plate reconstruction models of the Afro-Arabian Rift System relies on considering the Afar Depression as a typical rift-rift-rift triple junction where the Arabian, Somali and Nubian (African) plates are separating by the Red Sea, the Gulf of Aden and the Main Ethiopian Rift suggesting the presence of "sharp and rigid" plate boundaries. However, at the regional-scale the Afar kinematics are more complex due to stepping of the Red Sea propagator and the Gulf of Aden propagator onto Afar as well as the presence of the Danakil, Ali Sabieh and East Central Block "micro-plates". This study incorporates the motion of these micro-plates into the regional-scale model and defined the plate boundary between the Arabian and the African plates within Afar as likely a diffused zone of extensional strain within the East Central Block. Third, DInSAR technology is used to create ascending and descending differential interferograms from the Envisat Advanced Synthetic Aperture Radar (ASAR) C-Band data for the East Central Block to image active crustal deformation related to extensional tectonics and volcanism. Results of the DInSAR study indicate no strong strain localization but rather a diffused pattern of deformation across the entire East Central Block.

  7. Crustal and lithospheric structure of the west Antarctic Rift System from geophysical investigations: a review

    USGS Publications Warehouse

    Behrendt, John C.

    1999-01-01

    The active West Antarctic Rift System, which extends from the continental shelf of the Ross Sea, beneath the Ross Ice Shelf and the West Antarctic Ice Sheet, is comparable in size to the Basin and Range in North America, or the East African rift systems. Geophysical surveys (primarily marine seismic and aeromagnetic combined with radar ice sounding) have extended the information provided by sparse geologic exposures and a few drill holes over the ice and sea covered area. Rift basins developed in the early Cretaceous accompanied by the major extension of the region. Tectonic activity has continued episodically in the Cenozoic to the present, including major uplift of the Transantarctic Mountains. The West Antarctic ice sheet, and the late Cenozoic volcanic activity in the West Antarctic Rift System, through which it flows, have been coeval since at least Miocene time. The rift is characterized by sparse exposures of late Cenozoic alkaline volcanic rocks extending from northern Victoria Land throughout Marie Byrd Land. The aeromagnetic interpretations indicate the presence of > 5 x 105 km2 (> 106 km3) of probable late Cenozoic volcanic rocks (and associated subvolcanic intrusions) in the West Antarctic rift. This great volume with such limited exposures is explained by glacial removal of the associated late Cenozoic volcanic edifices (probably hyaloclastite debris) concomitantly with their subglacial eruption. Large offset seismic investigations in the Ross Sea and on the Ross Ice Shelf indicate a ~ 17-24-km-thick, extended continental crust. Gravity data suggest that this extended crust of similar thickness probably underlies the Ross Ice Shelf and Byrd Subglacial Basin. Various authors have estimated maximum late Cretaceous-present crustal extension in the West Antarctic rift area from 255-350 km based on balancing crustal thickness. Plate reconstruction allowed < 50 km of Tertiary extension. However, paleomagnetic measurements suggested about 1000 km of post

  8. Combining hydrologic and groundwater modelling to characterize a regional aquifer system within a rift setting (Gidabo River Basin, Main Ethiopian Rift)

    NASA Astrophysics Data System (ADS)

    Birk, Steffen; Mechal, Abraham; Wagner, Thomas; Dietzel, Martin; Leis, Albrecht; Winkler, Gerfried; Mogessie, Aberra

    2016-04-01

    The development of groundwater resources within the Ethiopian Rift is complicated by the strong physiographic contrasts between the rift floor and the highland and by the manifold hydrogeological setting composed of volcanic rocks of different type and age that are intersected by numerous faults. Hydrogeochemical and isotope data from various regions within the Ethiopian Rift suggest that the aquifers within the semi-arid rift floor receive a significant contribution of groundwater flow from the humid highland. For example, the major ion composition of groundwater samples from Gidabo River Basin (3302 km²) in the southern part of the Main Ethiopian Rift reveals a mixing trend from the highland toward the rift floor; moreover, the stable isotopes of water, deuterium and O-18, of the rift-floor samples indicate a component recharged in the highland. This work aims to assess if the hydrological and hydrogeological data available for Gidabo River Basin is consistent with these findings and to characterize the regional aquifer system within the rift setting. For this purpose, a two-step approach is employed: First, the semi-distributed hydrological model SWAT is used to obtain an estimate of the spatial and temporal distribution of groundwater recharge within the watershed; second, the numerical groundwater flow model MODFLOW is employed to infer aquifer properties and groundwater flow components. The hydrological model was calibrated and validated using discharge data from three stream gauging stations within the watershed (Mechal et al., Journal of Hydrology: Regional Studies, 2015, doi:10.1016/j.ejrh.2015.09.001). The resulting recharge distribution exhibits a strong decrease from the highland, where the mean annual recharge amounts to several hundred millimetres, to the rift floor, where annual recharge largely is around 100 mm and below. Using this recharge distribution as input, a two-dimensional steady-state groundwater flow model was calibrated to hydraulic

  9. The hydrothermal system associated with the Kilauea East Rift Zone, Hawaii

    SciTech Connect

    Thomas, D.M.; Conrad, M.E.

    1997-12-31

    During the last twenty years drilling and fluid production on the Kilauea East Rift Zone (KERZ) has shown that an active hydrothermal system is associated with much of the rift. Well logging and fluid geochemistry indicate that reservoir temperatures exceed 360 C but are highly variable. Although neither well testing nor pressure decline data have clearly demonstrated the lateral limits of the reservoir, divergent fluid compositions over short distances suggest that the larger hydrothermal system is strongly compartmentalized across the rift zone. The chemical compositions of production fluids indicate that recharge is derived from ocean water and meteoric recharge and isotopic data suggest that the latter may be derived from subsurface inflow from the flanks of Mauna Loa.

  10. Modeling fault kinematics, segment interaction and transfer zone geometry as a function of pre-existing fabrics: the Albertine rift, East African Rift System.

    NASA Astrophysics Data System (ADS)

    Aanyu, Kevin; Koehn, Daniel

    2010-05-01

    This study focuses on the development of the Rwenzori Mountains, an uplift horst block within the northern-most segment of the western branch of the East African Rift System (EARS). Attention is drawn to the role of pre-existing crustal weaknesses left behind by Proterozoic mobile belts that pass around cratonic Archean shields namely the Tanzanian Craton to the southeast and the Congo craton to the northwest. We study how the southward propagating sub-segment of the rift that contains Lake Albert to the north interacts with the northward propagating sub-segment that contains the lakes Edward and George and how this interaction produces the structural geometries observed within and around the Rwenzori horst block. Analogue experiments are used to simulate behavior of the upper crust with pre-cut rubber strips of varying overstep/overlap, placed oblique and/or orthogonal to the extension vector. The points of connection to the basal sheet present velocity discontinuities to localize deformation below the sand. Surface geometry of the developing rifts and section cuts are used to study the kinematics that result from the given boundary conditions. In general we try to model two parallel rifts that propagate towards each other and interact. Results show that greater overstep of rifts produces an oblique shear-dominated transfer zone with deep grabens (max.7.0km) in the adjoining segments. Smaller overlap ends in extension-dominated transfer, offset rift segments without oblique transfer faults to join two adjacent rift arms and produces moderately deep grabens (max.4.6km). When overlap doubles the overstep (SbR5), rifts propagate sub-orthogonal to the extension direction in a rotation-dominated transfer and form shallow valleys (max.2.9km). Whether a block like the Rwenzori Mountains is captured and rotates, depends on the overlap/overstep ratio where the rotation direction of a captured block is determined by the sense of overlap (right- or left-lateral). Fault

  11. Rift border system: The interplay between tectonics and sedimentation in the Reconcavo basin, northeastern Brazil

    SciTech Connect

    Magnavita, L.P.; Silva, T.F. da

    1995-11-01

    A geometric and depositional model is proposed to explain the tectonic and sedimentary evolution of the main border of the Reconcavo basin. The architecture of the rift margin is characterized by a rift border system constituted by (1) a master fault, (2) a step, and (3) a clastic wedge. This footwall-derived clastic wedge is interpreted as alluvial fans and fan deltas composed of conglomerates that interfinger with hanging-wall strata. The analysis of the vertical distribution of coarse-grained components of this wedge suggests that its composition is geographically controlled, and no regular inverted stratigraphy is commonly described for this type of succession. During an initial lacustrine phase, turbidites accumulated farther from and parallel to the rift margin. The mapping of marker beds that bound these lacustrine turbidite deposits may be used to infer major periods of clastic influx and, therefore, to correlate with periods of fault-related subsidence or climatic fluctuations in the depositional basin and erosion of the sediment source area. Periods of limited back-faulting and basin expansion toward the main border are distinguished through patterns of progradation and aggradation indicating progressive retreat of the rift border and younging; in the footwall direction. The overall evolution of the rift border seems to be related to extension, block rotation, hanging-wall subsidence, and footwall uplift associated with the initial master fault, with limited propagation of faults away from the basin into the footwall.

  12. Where is the West Antarctic Rift System in the Amundsen Sea and Bellingshausen Sea sectors?

    NASA Astrophysics Data System (ADS)

    Gohl, Karsten; Kalberg, Thomas; Eagles, Graeme; Dziadek, Ricarda; Kaul, Norbert; Spiegel, Cornelia; Lindow, Julia

    2015-04-01

    The West Antarctic Rift System (WARS) is one of the largest continental rifts globally, but its lateral extent, distribution of local rifts, timing of rifting phases, and mantle processes are still largely enigmatic. It has been presumed that the rift and its crustal extensional processes have widely controlled the history and development of West Antarctic glaciation with an ice sheet of which most is presently based at sub-marine level and which is, therefore, likely to be highly sensitive to ocean warming. While the western domain of the WARS in the Ross Sea has been studied in some detail, only recently have various geophysical and geochemical/thermochronological analyses revealed indications for its eastern extent in the Amundsen Sea and Bellingshausen Sea sectors of the South Pacific realm. The current model, based on these studies and additional data, suggests that the WARS activity included tectonic translateral, transtensional and extensional processes from the Amundsen Sea Embayment to the Bellingshausen Sea region of the southern Antarctic Peninsula. We present the range of existing hypotheses regarding the extent of the eastern WARS as well as published and yet unpublished data that support a conceptual WARS model for the eastern West Antarctica with implications for glacial onset and developments.

  13. The Midcontinent rift system and the Precambrian basement in southern Michigan

    SciTech Connect

    Smith, W.A. . Dept. of Geology)

    1994-04-01

    The Precambrian basement within Michigan consists of at least three provinces, each characterized by distinctive potential field anomalies: (1) the Eastern Granite-Rhyolite Province (EGRP) in the south, (2) the Grenville Province in the southeast and (3) the Penokean Province to the north. Also located within the basement is the Mid-Michigan rift (MMR), which is the eastern arm of the Midcontinent rift system (MRS). Southwest and parallel to the MMR is a series of linear positive gravity anomalies which has been referred to as the Ft. Wayne rift (FWR) and the Southwest Michigan Anomaly (SWMA). The EGRP, which is characterized by undeformed and unmetamorphosed rhyolite to dacite and epizonal granites, was emplaced ca. 1510--1450 Ma. However, the EGRP may be comprised of several terranes of varying extent and origin based on analysis of potential field data and rock and mineral ages. The MMR and the FWR/SWMA are characterized by linear arrays of positive magnetic and gravity anomalies, which are probably due to thick accumulations of mafic igneous rocks within the rifts. The extent and trends of the FWR/SWMA have been largely inferred from geophysical data with a presumption of the age of about 1,100 Ma. The continuation of the MMR southward into Ohio and Kentucky as a sequence of gravity highs is questionable and needs further resolution. The FWR/SWMA may be part of the East Continent Rift Basin (ECRB). The ECRB, which is a large complex of related rift basins of Keweenawan age (1300 --1100 Ma), may be an extension of the MRS but it is not physically continuous with it. The ECRB lies to the west of the Grenville Front and extends at least from northwest Ohio to central Kentucky. Extensions of the ECRB north and south are speculative.

  14. Current kinematics and dynamics of Africa and the East African Rift System

    NASA Astrophysics Data System (ADS)

    Stamps, D. S.; Flesch, L. M.; Calais, E.; Ghosh, A.

    2014-06-01

    Although the East African Rift System (EARS) is an archetype continental rift, the forces driving its evolution remain debated. Some contend buoyancy forces arising from gravitational potential energy (GPE) gradients within the lithosphere drive rifting. Others argue for a major role of the diverging mantle flow associated with the African Superplume. Here we quantify the forces driving present-day continental rifting in East Africa by (1) solving the depth averaged 3-D force balance equations for 3-D deviatoric stress associated with GPE, (2) inverting for a stress field boundary condition that we interpret as originating from large-scale mantle tractions, (3) calculating dynamic velocities due to lithospheric buoyancy forces, lateral viscosity variations, and velocity boundary conditions, and (4) calculating dynamic velocities that result from the stress response of horizontal mantle tractions acting on a viscous lithosphere in Africa and surroundings. We find deviatoric stress associated with lithospheric GPE gradients are ˜8-20 MPa in EARS, and the minimum deviatoric stress resulting from basal shear is ˜1.6 MPa along the EARS. Our dynamic velocity calculations confirm that a force contribution from GPE gradients alone is sufficient to drive Nubia-Somalia divergence and that additional forcing from horizontal mantle tractions overestimates surface kinematics. Stresses from GPE gradients appear sufficient to sustain present-day rifting in East Africa; however, they are lower than the vertically integrated strength of the lithosphere along most of the EARS. This indicates additional processes are required to initiate rupture of continental lithosphere, but once it is initiated, lithospheric buoyancy forces are enough to maintain rifting.

  15. Historical volcanism and the state of stress in the East African Rift System

    NASA Astrophysics Data System (ADS)

    Wadge, Geoffrey; Biggs, Juliet; Lloyd, Ryan; Kendall, Michael

    2016-09-01

    Crustal extension at the East African Rift System (EARS) should, as a tectonic ideal, involve a stress field in which the direction of minimum horizontal stress is perpendicular to the rift. A volcano in such a setting should produce dykes and fissures parallel to the rift. How closely do the volcanoes of the EARS follow this? We answer this question by studying the 21 volcanoes that have erupted historically (since about 1800) and find that 7 match the (approximate) geometrical ideal. At the other 14 volcanoes the orientation of the eruptive fissures/dykes and/or the axes of the host rift segments are oblique to the ideal values. To explain the eruptions at these volcanoes we invoke local (non-plate tectonic) variations of the stress field caused by: crustal heterogeneities and anisotropies (dominated by NW structures in the Protoerozoic basement), transfer zone tectonics at the ends of offset rift segments, gravitational loading by the volcanic edifice (typically those with 1-2 km relief) and magmatic pressure in central reservoirs. We find that the more oblique volcanoes tend to have large edifices, large eruptive volumes and evolved and mixed magmas capable of explosive behaviour. Nine of the volcanoes have calderas of varying ellipticity, 6 of which are large, reservoir-collapse types mainly elongated across rift (e.g. Kone) and 3 are smaller, elongated parallel to the rift and contain active lava lakes (e.g. Erta Ale), suggesting different mechanisms of formation and stress fields. Nyamuragira is the only EARS volcano with enough sufficiently well-documented eruptions to infer its long-term dynamic behaviour. Eruptions within 7 km of the volcano are of relatively short duration (<100 days), but eruptions with more distal fissures tend to have greater obliquity and longer durations, indicating a changing stress field away from the volcano. There were major changes in long-term magma extrusion rates in 1977 (and perhaps in 2002) due to major along-rift dyking

  16. Characterising East Antarctic Lithosphere and its Rift Systems using Gravity Inversion

    NASA Astrophysics Data System (ADS)

    Vaughan, Alan P. M.; Kusznir, Nick J.; Ferraccioli, Fausto; Leat, Phil T.; Jordan, Tom A. R. M.; Purucker, Michael E.; Golynsky, A. V. Sasha; Rogozhina, Irina

    2013-04-01

    Since the International Geophysical Year (1957), a view has prevailed that East Antarctica has a relatively homogeneous lithospheric structure, consisting of a craton-like mosaic of Precambrian terranes, stable since the Pan-African orogeny ~500 million years ago (e.g. Ferracioli et al. 2011). Recent recognition of a continental-scale rift system cutting the East Antarctic interior has crystallised an alternative view of much more recent geological activity with important implications. The newly defined East Antarctic Rift System (EARS) (Ferraccioli et al. 2011) appears to extend from at least the South Pole to the continental margin at the Lambert Rift, a distance of 2500 km. This is comparable in scale to the well-studied East African rift system. New analysis of RadarSat data by Golynsky & Golynsky (2009) indicates that further rift zones may form widely distributed extension zones within the continent. A pilot study (Vaughan et al. 2012), using a newly developed gravity inversion technique (Chappell & Kusznir 2008) with existing public domain satellite data, shows distinct crustal thickness provinces with overall high average thickness separated by thinner, possibly rifted, crust. Understanding the nature of crustal thickness in East Antarctica is critical because: 1) this is poorly known along the ocean-continent transition, but is necessary to improve the plate reconstruction fit between Antarctica, Australia and India in Gondwana, which will also better define how and when these continents separated; 2) lateral variation in crustal thickness can be used to test supercontinent reconstructions and assess the effects of crystalline basement architecture and mechanical properties on rifting; 3) rift zone trajectories through East Antarctica will define the geometry of zones of crustal and lithospheric thinning at plate-scale; 4) it is not clear why or when the crust of East Antarctica became so thick and elevated, but knowing this can be used to test models of

  17. Twenty-five years of geodetic measurements along the Tadjoura-Asal rift system, Djibouti, East Africa

    NASA Astrophysics Data System (ADS)

    Vigny, Christophe; de Chabalier, Jean-Bernard; Ruegg, Jean-Claude; Huchon, Philippe; Feigl, Kurt L.; Cattin, Rodolphe; Asfaw, Laike; Kanbari, Khaled

    2007-06-01

    Since most of Tadjoura-Asal rift system sits on dry land in the Afar depression near the triple junction between the Arabia, Somalia, and Nubia plates, it is an ideal natural laboratory for studying rifting processes. We analyze these processes in light of a time series of geodetic measurements from 1978 through 2003. The surveys used triangulation (1973), trilateration (1973, 1979, and 1981-1986), leveling (1973, 1979, 1984-1985, and 2000), and the Global Positioning System (GPS, in 1991, 1993, 1995, 1997, 1999, 2001, and 2003). A network of about 30 GPS sites covers the Republic of Djibouti. Additional points were also measured in Yemen and Ethiopia. Stations lying in the Danakil block have almost the same velocity as Arabian plate, indicating that opening near the southern tip of the Red Sea is almost totally accommodated in the Afar depression. Inside Djibouti, the Asal-Ghoubbet rift system accommodates 16 ± 1 mm/yr of opening perpendicular to the rift axis and exhibits a pronounced asymmetry with essentially null deformation on its southwestern side and significant deformation on its northeastern side. This rate, slightly higher than the large-scale Arabia-Somalia motion (13 ± 1 mm/yr), suggests transient variations associated with relaxation processes following the Asal-Ghoubbet seismovolcanic sequence of 1978. Inside the rift, the deformation pattern exhibits a clear two-dimensional pattern. Along the rift axis, the rate decreases to the northwest, suggesting propagation in the same direction. Perpendicular to the rift axis, the focus of the opening is clearly shifted to the northeast, relative to the topographic rift axis, in the "Petit Rift," a rift-in-rift structure, containing most of the active faults and the seismicity. Vertical motions, measured by differential leveling, show the same asymmetric pattern with a bulge of the northeastern shoulder. Although the inner floor of the rift is subsiding with respect to the shoulders, all sites within the

  18. Tomography of the East African Rift System in Mozambique

    NASA Astrophysics Data System (ADS)

    Domingues, A.; Silveira, G. M.; Custodio, S.; Chamussa, J.; Lebedev, S.; Chang, S. J.; Ferreira, A. M. G.; Fonseca, J. F. B. D.

    2014-12-01

    Unlike the majority of the East African Rift, the Mozambique region has not been deeply studied, not only due to political instabilities but also because of the difficult access to its most interior regions. An earthquake with M7 occurred in Machaze in 2006, which triggered the investigation of this particular region. The MOZART project (funded by FCT, Lisbon) installed a temporary seismic network, with a total of 30 broadband stations from the SEIS-UK pool, from April 2011 to July 2013. Preliminary locations of the seismicity were estimated with the data recorded from April 2011 to July 2012. A total of 307 earthquakes were located, with ML magnitudes ranging from 0.9 to 3.9. We observe a linear northeast-southwest distribution of the seismicity that seems associated to the Inhaminga fault. The seismicity has an extension of ~300km reaching the Machaze earthquake area. The northeast sector of the seismicity shows a good correlation with the topography, tracing the Urema rift valley. In order to obtain an initial velocity model of the region, the ambient noise method is used. This method is applied to the entire data set available and two additional stations of the AfricaARRAY project. Ambient noise surface wave tomography is possible by computing cross-correlations between all pairs of stations and measuring the group velocities for all interstation paths. With this approach we obtain Rayleigh wave group velocity dispersion curves in the period range from 3 to 50 seconds. Group velocity maps are calculated for several periods and allowing a geological and tectonic interpretation. In order to extend the investigation to longer wave periods and thus probe both the crust and upper mantle, we apply a recent implementation of the surface-wave two-station method (teleseismic interferometry - Meier el al 2004) to augment our dataset with Rayleigh wave phase velocities curves in a broad period range. Using this method we expect to be able to explore the lithosphere

  19. Impact of geodynamic development of the Barents Sea deep rift on evolving petroleum systems

    NASA Astrophysics Data System (ADS)

    Balanyuk, I.; Dmitrievsky, A.

    2009-04-01

    All the Barents Sea deposits are situated in the epicenter on active geodynamic development of the Barents Sea rift and, most important, over the zone of listric faults intersection, which consist a knot system over the mantle diapir. This is confirmed by prospecting seismology. Intrusion of hot mantle matter with further cooling down of abnormal lense might be a possible cause of appearance and evolution of ultradeep depressions. A high "seismic stratification" of the lower crust (nearly reaching the basement surface) at time scale about 8 sec. is typical for the inner, the deepest part of the depression. Supposing the "seismic stratified" lower crust correspond to "basalt" layer, this area is nearly upper crust ("granitic-gneiss") free. This fact confurmes conception on development of "granite free gaps" in the depression basement. Thick blocks of "seismically transparent" upper crust corresponding to the "granitic-gneiss" layer are marked out within Kolsk-Kanin monocline. An abrupt thickness decrease and appearance of "stratified" areas takes place at the southern edge of the depression. A filling of the over-rift sag with sediments, revival of the faults and their effect on the filtration processes and gas hydrates formation took place in the South Barents Sea depression. Repeating activation of the fault blocks in the basement, especially during late Jurassic - early Cretaceous period contributed to formation of the structures related to the greatest deposits of the South Barents Sea depression. An extended field acoustic data collected in the Barents Sea led to understanding of general fundamental problems for all Arctic Seas and, first of all, the problem of Quaternary glaciations. An analysis of Eurasian-Arctic continental margin shows correspondence between the rift systems of the shelf with those of the ocean. This relation can be observed by an example of the central Arctic region. All the rift systems underlying the sediment basin are expressed in the

  20. Revised Eocene-Oligocene kinematics for the West Antarctic rift system

    NASA Astrophysics Data System (ADS)

    Granot, R.; Cande, S. C.; Stock, J. M.; Damaske, D.

    2013-01-01

    Abstract<p label="1">Past plate motion between East and West Antarctica along the West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span> had important regional and global implications. Although extensively studied, the kinematics of the <span class="hlt">rift</span> during Eocene-Oligocene time still remains elusive. Based on a recent detailed aeromagnetic survey from the Adare and Northern Basins, located in the northwestern Ross Sea, we present the first well-constrained kinematic model with four rotations for Anomalies 12o, 13o, 16y, and 18o (26.5-40.13 Ma). These rotation poles form a cluster suggesting a stable sense of motion during that period of time. The poles are located close to the central part of the <span class="hlt">rift</span> implying that the local motion varied from extension in the western Ross Sea sector (Adare Basin, Northern Basin, and Victoria Land Basin) to dextral transcurrent motion in the Ross Ice Shelf and to oblique convergence in the eastern end of the <span class="hlt">rift</span> zone. The results confirm previous estimates of 95 km of extension in the Victoria Land Basin.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active"><span>3</span></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_3 --> <div id="page_4" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="61"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T51G3011O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T51G3011O"><span>Surface Wave Analysis of Regional Earthquakes in the Eastern <span class="hlt">Rift</span> <span class="hlt">System</span> (Africa)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oliva, S. J. C.; Guidarelli, M.; Ebinger, C. J.; Roecker, S. W.; Tiberi, C.</p> <p>2015-12-01</p> <p>The Northern Tanzania Divergence (NTD), the youngest part of the East African <span class="hlt">Rift</span> <span class="hlt">System</span>, presents the opportunity to obtain insights about the birth and early stages of <span class="hlt">rifting</span> before it progresses to mature <span class="hlt">rifting</span> and seafloor spreading. This region is particularly interesting because the Eastern <span class="hlt">rift</span> splits into three arms in this area and develops in a region of thick and cold lithosphere, amid the Archaean Tanzanian craton and the Proterozoic orogenic belt (the Masai block). We analyzed about two thousand seismic events recorded by the 39 broadband stations of the CRAFTI network during its two-year deployment in the NTD area in 2013 to 2014. We present the results of surface wave tomographic inversion obtained from fundamental-mode Rayleigh waves for short periods (between 4 to 14 seconds). Group velocity dispersion curves obtained via multiple filter analysis are path-averaged and inverted to produce 0.1º x 0.1º nodal grid tomographic maps for discrete periods using a 2D generalization of the Backus and Gilbert method. To quantify our results in terms of S-wave velocity structure the average group velocity dispersion curves are then inverted, using a linearized least-squares inversion scheme, in order to obtain the shear wave velocity structure for the upper 20 km of the crust. Low velocity anomalies are observed in the region 50 km south of Lake Natron, as well as in the area of the Ngorongoro crater. The implications of our results for the local tectonics and the development of the <span class="hlt">rifting</span> <span class="hlt">system</span> will be discussed in light of the growing geophysical database from this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JAfES.111..288S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JAfES.111..288S"><span>Sedimentary budgets of the Tanzania coastal basin and implications for uplift history of the East African <span class="hlt">rift</span> <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Said, Aymen; Moder, Christoph; Clark, Stuart; Abdelmalak, Mohamed Mansour</p> <p>2015-11-01</p> <p>Data from 23 wells were used to quantify the sedimentary budgets in the Tanzania coastal basin in order to unravel the uplift chronology of the sourcing area located in the East African <span class="hlt">Rift</span> <span class="hlt">System</span>. We quantified the siliciclastic sedimentary volumes preserved in the Tanzania coastal basin corrected for compaction and in situ (e.g., carbonates) production. We found that the drainage areas, which supplied sediments to this basin, were eroded in four episodes: (1) during the middle Jurassic, (2) during the Campanian-Palaeocene, (3) during the middle Eocene and (4) during the Miocene. Three of these high erosion and sedimentation periods are more likely related to uplift events in the East African <span class="hlt">Rift</span> <span class="hlt">System</span> and earlier <span class="hlt">rift</span> shoulders and plume uplifts. Indeed, rapid cooling in the <span class="hlt">rift</span> <span class="hlt">system</span> and high denudation rates in the sediment source area are coeval with these recorded pulses. However, the middle Eocene pulse was synchronous with a fall in the sea level, a climatic change and slow cooling of the <span class="hlt">rift</span> flanks and thus seems more likely due to climatic and eustatic variations. We show that the <span class="hlt">rift</span> shoulders of the East African <span class="hlt">rift</span> <span class="hlt">system</span> have inherited their present relief from at least three epeirogenic uplift pulses of middle Jurassic, Campanian-Palaeocene, and Miocene ages.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70021879','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70021879"><span>Tectonic and sediment supply control of deep <span class="hlt">rift</span> lake turbidite <span class="hlt">systems</span>: Lake Baikal, Russia</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Nelson, C.H.; Karabanov, E.B.; Colman, Steven M.; Escutia, C.</p> <p>1999-01-01</p> <p>Tectonically influenced half-graben morphology controls the amount and type of sediment supply and consequent type of late Quaternary turbidite <span class="hlt">systems</span> developed in the active <span class="hlt">rift</span> basins of Lake Baikal, Russia. Steep border fault slopes (footwall) on the northwest sides of half-graben basins provide a limited supply of coarser grained clastic material to multiple small fan deltas. These multiple sediment sources in turn laterally feed small (65 km) axially fed elongate mud-rich fans sourced by regional exterior drainage of the Selenga River that supplies large quantities of silt. Basin plain turbidites in the center of the linear basins and axial channels that are controlled by <span class="hlt">rift</span>-parallel faults are fed from, and interfinger with, aprons and fans. The predictability of the turbidite <span class="hlt">systems</span> in Lake Baikal provides the best example yet studied of how tectonics and sediment supply interact to control the development of a wide variety of coeval turbidite <span class="hlt">systems</span> on a single basin floor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.5869C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.5869C"><span>Diachronous Growth of Normal Fault <span class="hlt">Systems</span> in Multiphase <span class="hlt">Rift</span> Basins: Structural Evolution of the East Shetland Basin, Northern North Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Claringbould, Johan S.; Bell, Rebecca E.; A-L. Jackson, Christopher; Gawthorpe, Robert L.; Odinsen, Tore</p> <p>2015-04-01</p> <p>Our ability to determine the structural evolution and interaction of fault <span class="hlt">systems</span> (kinematically linked group of faults that are in the km to 10s of km scale) within a <span class="hlt">rift</span> basin is typically limited by the spatial extent and temporal resolution of the available data and methods used. Physical and numerical models provide predictions on how fault <span class="hlt">systems</span> nucleate, grow and interact, but these models need to be tested with natural examples. Although field studies and individual 3D seismic surveys can provide a detailed structural evolution of individual fault <span class="hlt">systems</span>, they are often spatially limited and cannot be used examine the interaction of fault <span class="hlt">systems</span> throughout the entire basin. In contrast, regional subsurface studies, commonly conducted on widely spaced 2D seismic surveys, are able to capture the general structural evolution of a <span class="hlt">rift</span> basin, but lack the spatial and temporal detail. Moreover, these studies typically describe the structural evolution of <span class="hlt">rifts</span> as comprising multiple discrete tectonic stages (i.e. pre-, syn- and post-<span class="hlt">rift</span>). This simplified approach does not, however, consider that the timing of activity can be strongly diachronous along and between faults that form part of a kinematically linked <span class="hlt">system</span> within a <span class="hlt">rift</span> basin. This study focuses on the East Shetland Basin (ESB), a multiphase <span class="hlt">rift</span> basin located on the western margin of the North Viking Graben, northern North Sea. Most previous studies suggest the basin evolved in response to two discrete phases of extension in the Permian-Triassic and Middle-Late Jurassic, with the overall geometry of the latter <span class="hlt">rift</span> to be the result of selective reactivation of faults associated with the former <span class="hlt">rift</span>. Gradually eastwards thickening intra-<span class="hlt">rift</span> strata (deposited between two <span class="hlt">rift</span> phases) that form wedges between and within fault blocks have led to two strongly contrasting tectonic interpretations: (i) Early-Middle Jurassic differential thermal subsidence after Permian-Triassic <span class="hlt">rifting</span>; or (ii</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.2307D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.2307D"><span>Sismotectonics in the western branch of the East African <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Delvaux, Damien; Kervyn, François; Mulumba, Jean-Luc; Kipata, Louis; Sebagenzi, Stanislas; Mavonga, Georges; Macheyeki, Athanas; Temu, Elly Bryan</p> <p>2013-04-01</p> <p>The western branch of the East African <span class="hlt">rift</span> <span class="hlt">system</span> is known of its particular seismic activity with larger magnitude (up to Ms 7.3) and more frequent destructive earthquakes than in the eastern branch. As a contribution to the IGCP 601 project Seismotectonic Map of Africa, we compiled the known active faults, thermal springs and historical seismicity in Central Africa. Using the rich archives of the Royal Museum for Central Africa, publications and own field observations, we present a compilation of available data relative to the current seismotectonic activity along the western branch of the East African <span class="hlt">rift</span> <span class="hlt">system</span>, in DRC, Rwanda, Burundi and Tanzania. Neotectonic activity related to the western <span class="hlt">rift</span> branch is in general well expressed and relatively well studied in the eastern flank of this <span class="hlt">rift</span> branch, in Uganda, Rwanda, Burundi and Tanzania. In contrast, the western flank of this <span class="hlt">rift</span> branch, largely exposed in the DRC, has attracted less attention. However, data collected during the colonial times show significant sismotectonic activity in East DRC, not only in the western flank of the western <span class="hlt">rift</span> branch, but extending far westwards up to the margin of the Congo basin. In particular, our predecessors paid a special attention to the mapping and description of thermal springs, noticing that they are often controlled by active faults. In addition, the operators of the relatively dense network of meteorological stations installed in the DRC, Rwanda and Burundi also recorded were with variable level of completeness and detail the earthquakes that they could felt. This provides a rich database that is used to complete the existing knowledge on historical seismicity. An important effort has still to be paid to identify and map potentially active fault due to poor field accessibility, tropical climate weathering and vegetation coverage. The main problem in the compilation of active fault data is that very few of them have been investigated by paleoseismic trenching</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70021976','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70021976"><span>Transect across the West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span> in the Ross Sea, Antarctica</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Trey, H.; Cooper, A. K.; Pellis, G.; Della, Vedova B.; Cochrane, G.; Brancolini, Giuliano; Makris, J.</p> <p>1999-01-01</p> <p>In 1994, the ACRUP (Antarctic Crustal Profile) project recorded a 670-km-long geophysical transect across the southern Ross Sea to study the velocity and density structure of the crust and uppermost mantle of the West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span>. Ray-trace modeling of P- and S-waves recorded on 47 ocean bottom seismograph (OBS) records, with strong seismic arrivals from airgun shots to distances of up to 120 km, show that crustal velocities and geometries vary significantly along the transect. The three major sedimentary basins (early-<span class="hlt">rift</span> grabens), the Victoria Land Basin, the Central Trough and the Eastern Basin are underlain by highly extended crust and shallow mantle (minimum depth of about 16 km). Beneath the adjacent basement highs, Coulman High and Central High, Moho deepens, and lies at a depth of 21 and 24 km, respectively. Crustal layers have P-wave velocities that range from 5.8 to 7.0 km/s and S-wave velocities from 3.6 to 4.2 km/s. A distinct reflection (PiP) is observed on numerous OBS from an intra-crustal boundary between the upper and lower crust at a depth of about 10 to 12 km. Local zones of high velocities and inferred high densities are observed and modeled in the crust under the axes of the three major sedimentary basins. These zones, which are also marked by positive gravity anomalies, may be places where mafic dikes and sills pervade the crust. We postulate that there has been differential crustal extension across the West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span>, with greatest extension beneath the early-<span class="hlt">rift</span> grabens. The large amount of crustal stretching below the major <span class="hlt">rift</span> basins may reflect the existence of deep crustal suture zones which initiated in an early stage of the <span class="hlt">rifting</span>, defined areas of crustal weakness and thereby enhanced stress focussing followed by intense crustal thinning in these areas. The ACRUP data are consistent with the prior concept that most extension and basin down-faulting occurred in the Ross Sea during late Mesozoic time, with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5456203','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5456203"><span>Keweenaw hot spot: Geophysical evidence for a 1. 1 Ga mantle plume beneath the Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hutchinson, D.R. ); White, R.S. ); Cannon, W.F.; Schulz, K.J. )</p> <p>1990-07-10</p> <p>The Proterozoic Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span> of North America is remarkably similar to Phanerozoic <span class="hlt">rifted</span> continental margins and flood basalt provinces. Like the younger analogues, the volcanism within this older <span class="hlt">rift</span> can be explained by decompression melting and rapid extrusion of igneous material during lithospheric extension above a broad, asthenospheric, thermal anomaly which the authors call the Keweenaw hot spot. Great Lakes International Multidisciplinary Program on Crustal evolution seismic reflection profiles constrain end-member models of melt thickness and stretching factors, which yield an inferred mantle potential temperature of 1,500-1,570C during <span class="hlt">rifting</span>. Combined gravity modeling and subsidence calculations are consistent with stretching factors that reached 3 or 4 before <span class="hlt">rifting</span> ceased, and much of the lower crust beneath the <span class="hlt">rift</span> consists of relatively high density intruded or underplated synrift igneous material. The isotopic signature of Keweenawan volcanic rocks, presented in a companion paper by Nicholson and Shirey (this issue), is consistent with the model of passive <span class="hlt">rifting</span> above an asthenospheric mantle plume.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T43C2693M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T43C2693M"><span>Nature of the Mantle Sources and Bearing on Tectonic Evolution in the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mukasa, S. B.; Rilling-Hall, S.; Marcano, M. C.; Wilson, T. J.; Lawver, L. A.; LeMasurier, W. E.</p> <p>2012-12-01</p> <p>We collected samples from subaerial lava flows and dredged some Neogene basanitic lavas from seven volcanic edifices in the Ross Sea, Antarctica - a part of the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> (WARS) and one of the world's largest alkaline magmatic provinces - for a study aimed at two principal objectives: (1) Geochemical interrogation of the most primitive magmatic rocks to try and understand the nature of the seismically abnormal mantle domain recently identified beneath the shoulder of the Transantarctic Mountains (TAM), the Ross Sea Embayment and Marie Byrd Land; and (2) Using 40Ar/39Ar geochronology to establish a temporal link between magmatism and tectonism, particularly in the Terror <span class="hlt">Rift</span>. We have attempted to answer the questions of whether magmatism is due to a hot mantle or wet mantle, and whether <span class="hlt">rifting</span> in the area triggered magmatic activity or vice versa. Results show that the area does not have an age-progressive hotspot track, and the magmatism post-dates the main phase of extension along the Terror <span class="hlt">Rift</span> within the WARS, which supports a decompression-melting model without the benefit of a significant thermal anomaly. In fact, preliminary volatile measurements on olivine-hosted melt inclusions have yielded water concentrations in excess of 2 wt%, indicating that flux melting was an important complementary process to decompression melting. The major oxide compositions of lavas in the WARS are best matched to experimental melts of carbonated peridotite, though garnet pyroxenite can also be a minor source. The Pb and Nd isotopic <span class="hlt">systems</span> are decoupled from each other, suggesting removal of fluid-mobile elements from the mantle source possibly during the long history of subduction along the Paleo-Pacific margin of Gondwana. Extremely unradiogenic 187Os/188Os ranging to as low as 0.1081 ± 0.0001 hints at the involvement of lithospheric components in generation of magmas in the WARS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T43A4705S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T43A4705S"><span>Regional 3D Numerical Modeling of the Lithosphere-Mantle <span class="hlt">System</span>: Implications for Continental <span class="hlt">Rift</span>-Parallel Surface Velocities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stamps, S.; Bangerth, W.; Hager, B. H.</p> <p>2014-12-01</p> <p>The East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS) is an active divergent plate boundary with slow, approximately E-W extension rates ranging from <1-6 mm/yr. Previous work using thin-sheet modeling indicates lithospheric buoyancy dominates the force balance driving large-scale Nubia-Somalia divergence, however GPS observations within the Western Branch of the EARS show along-<span class="hlt">rift</span> motions that contradict this simple model. Here, we test the role of mantle flow at the <span class="hlt">rift</span>-scale using our new, regional 3D numerical model based on the open-source code ASPECT. We define a thermal lithosphere with thicknesses that are systematically changed for generic models or based on geophysical constraints in the Western branch (e.g. melting depths, xenoliths, seismic tomography). Preliminary results suggest existing variations in lithospheric thicknesses along-<span class="hlt">rift</span> in the Western Branch can drive upper mantle flow that is consistent with geodetic observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1614484S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1614484S"><span>Mode of <span class="hlt">rifting</span> in magmatic-rich setting: Tectono-magmatic evolution of the Central Afar <span class="hlt">rift</span> <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stab, Martin; Bellahsen, Nicolas; Pik, Raphaël; Leroy, Sylvie; Ayalew, Dereje</p> <p>2014-05-01</p> <p>Observation of deep structures related to break-up processes at volcanic passive margins (VPM) is often a troublesome exercise: thick pre- to syn-breakup seaward-dipping reflectors (SDR) usually mask the continent-ocean boundary and hide the syn-<span class="hlt">rift</span> tectonic structures that accommodate crustal stretching and thinning. Some of the current challenges are about clarifying 1) if tectonic stretching fits the observed thinning and 2) what is the effect of continuous magma supply and re-thickening of the crust during extension from a rheological point of view? The Afar region in Ethiopia is an ideal natural laboratory to address those questions, as it is a highly magmatic <span class="hlt">rift</span> that is probably close enough to breakup to present some characteristics of VPM. Moreover, the structures related to <span class="hlt">rifting</span> since Oligocene are out-cropping, onshore and well preserved. In this contribution, we present new structural field data and lavas (U-Th/He) datings along a cross-section from the Ethiopian Plateau, through the marginal graben down to the Manda-Hararo active <span class="hlt">rift</span> axis. We mapped continent-ward normal fault array affecting highly tilted trapp series unconformably overlain by tilted Miocene (25-7 Ma) acid series. The main extensional and necking/thinning event took place during the end of this Miocene magmatic episode. It is itself overlain by flat lying Pliocene series, including the Stratoid. Balanced cross-sections of those areas allow us to constrain a surface stretching factor of about 2.1-2.9. Those findings have the following implications: - High beta factor constrained from field observations is at odd with thinning factor of ~1.3 predicted by seismic and gravimetric studies. We propose that the continental crust in Central Afar has been re-thickened by the emplacement of underplated magma and SDR. - The deformation in Central Afar appears to be largely distributed through space and time. It has been accommodated in a 200-300 km wide strip being a diffuse incipient</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JAESc..29..722Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JAESc..29..722Z"><span>Structure and geochronology of the southern Xainza-Dinggye <span class="hlt">rift</span> and its relationship to the south Tibetan detachment <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Jinjiang; Guo, Lei</p> <p>2007-03-01</p> <p>The Xainza-Dinggye <span class="hlt">rift</span> is one of several north-south trending <span class="hlt">rifts</span> in central and southern Tibet created by Cenozoic east-west extension during Indo-Asian convergence. The southern part of the <span class="hlt">rift</span> cuts through the Tethyan and High Himalayas. In the Tethyan Himalaya, this <span class="hlt">rift</span> consists of an early domal structure and a late normal fault developed during the progressive deformation. The dome is cored by leucogranitic plutons that intruded during extension. Muscovite 40Ar/ 39Ar ages of the mylonitic leucogranite indicate that extension in the Tethyan Himalaya began at ˜8 Ma or before. In the High Himalaya, the <span class="hlt">rift</span> is controlled by a normal fault dipping to the southeast. This fault has a structural constitution similar to a detachment fault. Its lower block is made up of mylonitic High Himalayan gneiss, intruded by early mylonitic leucogranite sills and late less-deformed biotite-bearing leucogranite dikes. Mica 40Ar/ 39Ar ages of these leucogranites and the retrograded metamorphosed gneiss of the lower block range from ˜13 to ˜10 Ma. In the study area, the south Tibetan detachment <span class="hlt">system</span> (STDS) is a ductile shear zone composed of mylonitic leucogranite that is intruded by less-deformed leucogranite and overlain by low grade metamorphic rocks. Mica 40Ar/ 39Ar ages of leucogranites in the shear zone and schist from the detachment hanging wall indicate a protracted deformation history of the STDS from ˜19 to ˜13 Ma. The Xainza-Dinggye <span class="hlt">rift</span> is younger than the STDS because it offsets the STDS; this north-south trending <span class="hlt">rift</span> belongs to a different tectonic <span class="hlt">system</span> from the east-west striking STDS, and may be caused by geological process related to India-Asia convergence. This temporal and spatial relationship of the STDS to the <span class="hlt">rift</span> may indicate an important change in tectonic regime at ˜13 Ma in the building of the plateau.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJEaS.105.1693K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJEaS.105.1693K"><span>The Rwenzori Mountains, a Palaeoproterozoic crustal shear belt crossing the Albertine <span class="hlt">rift</span> <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koehn, D.; Link, K.; Sachau, T.; Passchier, C. W.; Aanyu, K.; Spikings, A.; Harbinson, R.</p> <p>2016-09-01</p> <p>This contribution discusses the development of the Palaeoproterozoic Buganda-Toro belt in the Rwenzori Mountains and its influence on the western part of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> in Uganda. The Buganda-Toro belt is composed of several thick-skinned nappes consisting of Archaean Gneisses and Palaeoproterozoic cover units that are thrusted northwards. The high Rwenzori Mountains are located in the frontal unit of this belt with retrograde greenschist facies gneisses towards the north, which are unconformably overlain by metasediments and amphibolites. Towards the south, the metasediments are overthrust by the next migmatitic gneiss unit that belongs to a crustal-scale nappe. The southwards dipping metasedimentary and volcanic sequence in the high Rwenzori Mountains shows an inverse metamorphic grade with greenschist facies conditions in the north and amphibolite facies conditions in the south. Early D1 deformation structures are overgrown by cordierite, which in turn grows into D2 deformation, representing the major northwards directed thrusting event. We argue that the inverse metamorphic gradient develops because higher grade rocks are exhumed in the footwall of a crustal-scale nappe, whereas the exhumation decreases towards the north away from the nappe leading to a decrease in metamorphic grade. The D2 deformation event is followed by a D3 E-W compression, a D4 with the development of steep shear zones with a NNE-SSW and SSE-NNW trend including the large Nyamwamba shear followed by a local D5 retrograde event and D6 brittle reverse faulting. The Palaeoproterozoic Buganda-Toro belt is relatively stiff and crosses the NNE-SSW running <span class="hlt">rift</span> <span class="hlt">system</span> exactly at the node where the highest peaks of the Rwenzori Mountains are situated and where the Lake George <span class="hlt">rift</span> terminates towards the north. Orientation of brittle and ductile fabrics show some similarities indicating that the cross-cutting Buganda-Toro belt influenced <span class="hlt">rift</span> propagation and brittle fault development</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.T11A1232P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.T11A1232P"><span>Neogene-Quaternary Volcanic Alignments in the Transantarctic Mountains and West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> of Southern Victoria Land, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Paulsen, T. S.; Wilson, T. J.</p> <p>2004-12-01</p> <p>Neogene-Quaternary volcanism in southern Victoria Land, Antarctica, produced the Erebus Volcanic Province, a suite of alkaline volcanic rocks that extend from the Transantarctic Mountains <span class="hlt">rift</span>-flank uplift to offshore localities within the West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span>. We are mapping volcanic vent patterns in the province to detect alignments indicative of stress/strain patterns during <span class="hlt">rift</span> evolution. In the southern sector of the Erebus Volcanic Province in the Royal Society Range Block of the Transantarctic Mountains, mapping shows that elliptical scoria cones, fissures, dikes, and linear vent arrays define volcanic alignments that have a dominant NNE trend, with subsidiary WNW trends. Age data for the alignments suggest that this pattern persisted from 14.6 to 0.25 Ma. We are currently completing mapping along an east-west transect crossing the <span class="hlt">rift</span> margin, and results obtained so far within the <span class="hlt">rift</span> region indicate a similar pattern of alignments. On the northern flank of Mount Morning, a large volcano just to the east of the Royal Society Range, elliptical scoria cones and linear vent arrays define volcanic alignments that have a dominant NE trend, with a subsidiary NNW trend. Available age data suggest that many of these cone alignments may be of Quaternary age. At Brown Peninsula, further east from the <span class="hlt">rift</span> flank, cone alignments trend NNE and available ages range from 2 to 3 Ma. To the east of Brown Peninsula, cone alignments trend NW at Black Island, but are of uncertain age; age data on Black Island range from 11 to 3.4 Ma. At White Island, the farthest east into the <span class="hlt">rift</span>, cone alignments trend NNE and available age data suggest volcanism as young as 0.2 Ma. Although some differences in cone alignment trends are apparent between the <span class="hlt">rift</span> flank and the <span class="hlt">rift</span> <span class="hlt">system</span> across our transect, both regions appear to be dominated by NE trending alignments, which implies a WNW to NW minimum horizontal stress (Shmin) direction. This is oblique to the ENE Shmin Cape</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SedG..343..190S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SedG..343..190S"><span>Evolution of the western East African <span class="hlt">Rift</span> <span class="hlt">System</span> reflected in provenance changes of Miocene to Pleistocene synrift sediments (Albertine <span class="hlt">Rift</span>, Uganda)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schneider, Sandra; Hornung, Jens; Hinderer, Matthias</p> <p>2016-08-01</p> <p>Miocene to Pleistocene synrift sediments in the Albertine Graben reflect the complex geodynamic evolution in the Western branch of the East African <span class="hlt">Rift</span> <span class="hlt">System</span>. In this study we focus on the provenance of these siliciclastic deposits to identify sediment sources and supply paths with the ultimate goal to reconstruct the exhumation history of different tectonic blocks during prolonged <span class="hlt">rifting</span>, with specific focus on the uplift of the Rwenzori Mountains in Uganda. We present framework and heavy mineral petrographic data combined with varietal studies of detrital garnet and rutile, based on logged sediment sections on the Ugandan side of Lake Albert (Kisegi-Nyabusosi area). The analyzed sedimentary units have a feldspatho-quartzose composition and distinct variations in heavy mineral assemblages and mineral chemical composition indicating two provenance changes. The Miocene part of the stratigraphy is dominated by garnet, zircon, tourmaline and rutile, whereas Pliocene to Pleistocene sediment yields high amounts of less stable amphibole and epidote. An abrupt switch in heavy mineral assemblages occurs during the early Pliocene ( 5.5-5.0 Ma) and clearly postdates the formation of Palaeolake Obweruka at 8 Ma. Provenance signatures point to major sediment supply from the northeast and subsequently from the southeast. We interpret this first shift as transition from the pre-<span class="hlt">rift</span> to the syn-<span class="hlt">rift</span> stage. In this scenario, formation of Palaeolake Obweruka is due to higher humidity in the upper Miocene, rather than forced <span class="hlt">rifting</span>. A second change of sediment composition is documented by mineral geochemistry and coincides with fragmentation of Palaeolake Obweruka starting at 2.5 Ma. Detrital garnet in sediment of Miocene to Pliocene age is rich in pyrope and almandine and calculated Zr-in-rutile temperatures range between 550 and 950 °C. In contrast, garnet occurring in Pleistocene sediment (Nyabusosi Formation) has a higher spessartine component and rutile thermometry is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T13A2512A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T13A2512A"><span>Melt generation in the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span>: the volatile legacy of Gondwana subduction?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aviado, K.; Rilling-Hall, S.; Mukasa, S. B.; Bryce, J. G.; Cabato, J.</p> <p>2013-12-01</p> <p>The West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> (WARS) represents one of the largest extensional alkali volcanic provinces on Earth, yet the mechanisms responsible for driving <span class="hlt">rift</span>-related magmatism remain controversial. The failure of both passive and active models of decompression melting to explain adequately the observed volume of volcanism has prompted debate about the relative roles of thermal plume-related melting and ancient subduction-related flux melting. The latter is supported by roughly 500 Ma of subduction along the paleo-Pacific margin of Gondwana, although both processes are capable of producing the broad seismic anomaly imaged beneath most of the Southern Ocean. Olivine-hosted melt inclusions from basanitic lavas provide a means to evaluate the volatile budget of the mantle responsible for active <span class="hlt">rifting</span> beneath the WARS. We present H2O, CO2, F, S and Cl concentrations determined by SIMS and major oxide compositions by EMPA for olivine-hosted melt inclusions from lavas erupted in Northern Victoria Land (NVL) and Marie Byrd Land (MBL). The melt inclusions are largely basanitic in composition (4.05 - 17.09 wt % MgO, 37.86 - 45.89 wt % SiO2, and 1.20 - 5.30 wt % Na2O), and exhibit water contents ranging from 0.5 up to 3 wt % that are positively correlated with Cl and F. Coupling between Cl and H2O indicates metasomatic enrichment by subduction-related fluids produced during dehydration reactions; coupling between H2O and F, which is more highly retained in subducting slabs, may be related to partial melting of slab remnants [1]. Application of source lithology filters [2] to whole rock major oxide data shows that primitive lavas (MgO wt % >7) from the Terror <span class="hlt">Rift</span>, considered the locus of on-going tectonomagmatic activity, have transitioned from a pyroxenite source to a volatilized peridotite source over the past ~4 Ma. Integrating the volatile data with the modeled characteristics of source lithologies suggests that partial melting of lithosphere modified by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1987Geo....15..430W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1987Geo....15..430W"><span>Chow Bahir <span class="hlt">rift</span>: A “failed” <span class="hlt">rift</span> in southern Ethiopia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>W-Gabriel, Giday; Aronson, James L.</p> <p>1987-05-01</p> <p>The Chow Bahir <span class="hlt">rift</span> <span class="hlt">system</span> is a major graben in a 300-km-broad <span class="hlt">rift</span> zone recognized in southern Ethiopia between the Kenyan and Ethiopian domes where the East African <span class="hlt">rift</span> is not well defined. An extinct (failed) <span class="hlt">rift</span> discovered along the Omo Canyon to the north and on strike with the Chow Bahir <span class="hlt">rift</span> ceased activity about 4 m.y. ago. Chow Bahir is in a younger stage of abandonment as the main Ethiopian <span class="hlt">rift</span> propagates south into this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Tectp.688...65J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Tectp.688...65J"><span>Jurassic failed <span class="hlt">rift</span> <span class="hlt">system</span> below the Filchner-Ronne-Shelf, Antarctica: New evidence from geophysical data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jokat, Wilfried; Herter, Ulrich</p> <p>2016-10-01</p> <p>During the austral summer of 1994/95, reasonable ice conditions in the Weddell Sea allowed the acquisition of new high quality seismic refraction data parallel to the Filchner-Ronne Ice Shelf (FRS), Antarctica. Although pack ice conditions resulted in some data gaps, the <span class="hlt">final</span> velocity-depth/2D-density models cover the entire FRS in E-W direction using all available deep seismic data/picks from this remote area. The velocity-depth model shows a sedimentary basin with a thickness up to 12 km and a large velocity inversion in the lowermost sedimentary unit. The crustal thickness reaches a maximum of 40 km along the basin's margins in the Antarctic Peninsula and East Antarctica. In the central shelf area, numerous interfering seismic phases occur from the crust-mantle boundary at decreasing distances indicating a thinning of the crust. Here, the modelled velocities and densities reveal a thickness of 20 km for the igneous crust. This corridor of overthickened oceanic or close to oceanic crust is 160 km wide. The corridor is characterized by weak, but in general continuous magnetic anomalies, which we interpret as isochrons developed during the <span class="hlt">rifting</span> or the initial formation of oceanic crust. If the crustal composition represents an old stripe of oceanic crust, a minimum estimate for the early formation of the oceanic crust is 145/148 Ma (Late Jurassic). However, based on the velocity of <span class="hlt">rift</span> propagation during the initial opening of the adjacent Weddell Sea the oceanic crust is likely to have formed around 160 Ma. The onset of <span class="hlt">rifting</span> and development of a thick igneous crust can be related to stresses developed between the interior and the southwestern paleo-Pacific subduction margin of the fragmenting Gondwana supercontinent in combination with additional melt supply from a deeper mantle source that arrived and spread in the period 183-155 Ma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Geote..50..223S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Geote..50..223S"><span>Spatial instability of the <span class="hlt">rift</span> in the St. Paul multifault transform fracture <span class="hlt">system</span>, Atlantic Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sokolov, S. Yu.; Zaraiskaya, Yu. A.; Mazarovich, A. O.; Efimov, V. N.; Sokolov, N. S.</p> <p>2016-05-01</p> <p>The structure of the acoustic basement of the eastern part of the St. Paul multifault transform fracture <span class="hlt">system</span> hosts <span class="hlt">rift</span> paleovalleys and a paleonodal depression that mismatch the position of the currently active zones. This displacement zone, which is composed of five fault troughs, is unstable in terms of the position of the <span class="hlt">rift</span> segments, which jumped according to redistribution of stresses. The St. Paul <span class="hlt">system</span> is characterized by straightening of the transform transition between two remote segments of the Mid-Atlantic Ridge (MAR). The eastern part of the <span class="hlt">system</span> contains anomalous bright-spot-like reflectors on the flattened basement, which is a result of atypical magmatism, that forms the standard ridge relief of the acoustic basement. Deformations of the acoustic basement have a presedimentation character. The present-day deformations with lower amplitude in comparison to the basement are accompanied by acoustic brightening of the sedimentary sequence. The axial Bouguer anomalies in the east of the <span class="hlt">system</span> continue to the north for 120 km from the active segments of the St. Paul <span class="hlt">system</span>. Currently seismically active segments of the spreading <span class="hlt">system</span> are characterized by increasing amplitudes of the E-W displacement along the fault troughs. Cross-correlation of the lengths of the active structural elements of the MAR zone (segments of the ridge and transform fracture zones of displacement) indicates that, statistically, the multifault transform fracture <span class="hlt">system</span> is a specific type of oceanic strike-slip faults.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991Tectp.191...55C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991Tectp.191...55C"><span>Post-Pan-African tectonic evolution of South Malawi in relation to the Karroo and recent East African <span class="hlt">rift</span> <span class="hlt">systems</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Castaing, C.</p> <p>1991-05-01</p> <p>Structural studies conducted in the Lengwe and Mwabvi Karroo basins and in the basement in South Malawi, using regional maps and published data extended to cover Southeast Africa, serve to propose a series of geodynamic reconstructions which reveal the persistence of an extensional tectonic regime, the minimum stress σ3 of which has varied through time. The period of Karroo <span class="hlt">rifting</span> and the tholeiitic and alkaline magmatism which terminated it, were controlled by NW-SE extension, which resulted in the creation of roughly NE-SW troughs articulated by the Tanganyika-Malawi and Zambesi pre-transform <span class="hlt">systems</span>. These were NW-SE sinistral-slip <span class="hlt">systems</span> with directions of movement dipping slightly to the Southeast, which enabled the Mwanza fault to play an important role in the evolution of the Karroo basins of the Shire Valley. The Cretaceous was a transition period between the Karroo <span class="hlt">rifting</span> and the formation of the Recent East African <span class="hlt">Rift</span> <span class="hlt">System</span>. Extension was NE-SW, with some evidence for a local compressional episode in the Lengwe basin. Beginning in the Cenozoic, the extension once more became NW-SE and controlled the evolution in transtension of the Recent East African <span class="hlt">Rift</span> <span class="hlt">System</span>. This history highlights the major role of transverse faults <span class="hlt">systems</span> dominated by strike-slip motion in the evolution and perpetuation of the continental <span class="hlt">rift</span> <span class="hlt">systems</span>. These faults are of a greater geological persistence than the normal faults bounding the grabens, especially when they are located on major basement anisotropies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T11C4571C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T11C4571C"><span>Tectonoestratigraphic and Thermal Models of the Tiburon and Wagner Basins, northern Gulf of California <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Contreras, J.; Ramirez Zerpa, N. A.; Negrete-Aranda, R.</p> <p>2014-12-01</p> <p>The northern Gulf of California <span class="hlt">Rift</span> <span class="hlt">System</span> consist sofa series faults that accommodate both normal and strike-slip motion. The faults formed a series of half-greens filled with more than 7 km of siliciclastic suc­cessions. Here, we present tectonostratigraphic and heat flow models for the Tiburón basin, in the southern part of the <span class="hlt">system</span>, and the Wag­ner basin in the north. The models are constrained by two-dimensional seis­mic lines and by two deep boreholes drilled by PEMEX­-PEP. Analysis of the seismic lines and models' results show that: (i) subsidence of the basins is controlled by high-angle normal faults and by flow of the lower crust, (ii) basins share a common history, and (iii) there are significant differences in the way brittle strain was partitioned in the basins, a feature frequently observed in <span class="hlt">rift</span> basins. On one hand, the bounding faults of the Tiburón basin have a nested geometry and became active following a west-to-east sequence of activation. The Tiburon half-graben was formed by two pulses of fault activity. One took place during the protogulf extensional phase in the Miocene and the other during the opening of Gulf of California in the Pleistocene. On the other hand, the Wagner basin is the result of two fault generations. During the late-to middle Miocene, the west-dipping Cerro Prieto and San Felipe faults formed a domino array. Then, during the Pleistocene the Consag and Wagner faults dissected the hanging-wall of the Cerro Prieto fault forming the modern Wagner basin. Thermal modeling of the deep borehole temperatures suggests that the heat flow in these basins in the order of 110 mW/m2 which is in agreement with superficial heat flow measurements in the northern Gulf of California <span class="hlt">Rift</span> <span class="hlt">System</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_4 --> <div id="page_5" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="81"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009IJEaS..98.1581P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009IJEaS..98.1581P"><span>The <span class="hlt">final</span> <span class="hlt">rifting</span> evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Péron-Pinvidic, Gwenn; Manatschal, Gianreto</p> <p>2009-10-01</p> <p>In classical <span class="hlt">rift</span> models, deformation is either uniformly distributed leading to symmetric fault bounded basins overlying stretched ductile lower crust (e.g. pure shear McKenzie model) or asymmetric and controlled by large scale detachment faulting (simple shear Wernicke model). In both cases <span class="hlt">rifting</span> is considered as a mono-phase process and breakup is instantaneous resulting in the juxtaposition of continental and oceanic crust. The contact between these two types of crusts is often assumed to be sharp and marked by a first magnetic anomaly; and breakup is considered to be recorded as a major, basin wide unconformity, also referred to as breakup unconformity. These classical models, are currently challenged by new data from deep <span class="hlt">rifted</span> margins that ask for a revision of these concepts. In this paper, we review the pertinent observations made along the Iberia-Newfoundland conjugate margins, which bear the most complete data set available from deep magma-poor margins. We reevaluate and discuss the polyphase nature of continental <span class="hlt">rifting</span>, discuss the nature and significance of the different margin domains and show how they document extreme crustal thinning, retardation of subsidence and a complex transition into seafloor spreading. Although our study is limited to the Iberia-Newfoundland margins, comparisons with other margins suggest that the described evolution is probably more common and applicable for a large number of <span class="hlt">rifted</span> margins. These new results have major implications for plate kinematic reconstructions and invite to rethink the terminology, the processes, and the concepts that have been used to describe continental <span class="hlt">rifting</span> and breakup of the lithosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoJI.198..414A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoJI.198..414A"><span>Upper mantle seismic anisotropy beneath the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> and surrounding region from shear wave splitting analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Accardo, Natalie J.; Wiens, Douglas A.; Hernandez, Stephen; Aster, Richard C.; Nyblade, Andrew; Huerta, Audrey; Anandakrishnan, Sridhar; Wilson, Terry; Heeszel, David S.; Dalziel, Ian W. D.</p> <p>2014-07-01</p> <p>We constrain azimuthal anisotropy in the West Antarctic upper mantle using shear wave splitting parameters obtained from teleseismic SKS, SKKS and PKS phases recorded at 37 broad-band seismometres deployed by the POLENET/ANET project. We use an eigenvalue technique to linearize the rotated and shifted shear wave horizontal particle motions and determine the fast direction and delay time for each arrival. High-quality measurements are stacked to determine the best fitting splitting parameters for each station. Overall, fast anisotropic directions are oriented at large angles to the direction of Antarctic absolute plate motion in both hotspot and no-net-rotation frameworks, showing that the anisotropy does not result from shear due to plate motion over the mantle. Further, the West Antarctic directions are substantially different from those of East Antarctica, indicating that anisotropy across the continent reflects multiple mantle regimes. We suggest that the observed anisotropy along the central Transantarctic Mountains (TAM) and adjacent West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> (WARS), one of the largest zones of extended continental crust on Earth, results from asthenospheric mantle strain associated with the <span class="hlt">final</span> pulse of western WARS extension in the late Miocene. Strong and consistent anisotropy throughout the WARS indicate fast axes subparallel to the inferred extension direction, a result unlike reports from the East African <span class="hlt">rift</span> <span class="hlt">system</span> and <span class="hlt">rifts</span> within the Basin and Range, which show much greater variation. We contend that ductile shearing rather than magmatic intrusion may have been the controlling mechanism for accumulation and retention of such coherent, widespread anisotropic fabric. Splitting beneath the Marie Byrd Land Dome (MBL) is weaker than that observed elsewhere within the WARS, but shows a consistent fast direction, possibly representative of anisotropy that has been `frozen-in' to remnant thicker lithosphere. Fast directions observed inland from the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T21A2519Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T21A2519Z"><span>Active fault <span class="hlt">systems</span> of the Kivu <span class="hlt">rift</span> and Virunga volcanic province, and implications for geohazards</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zal, H. J.; Ebinger, C. J.; Wood, D. J.; Scholz, C. A.; d'Oreye, N.; Carn, S. A.; Rutagarama, U.</p> <p>2013-12-01</p> <p>H Zal, C Ebinger, D. Wood, C. Scholz, N. d'Oreye, S. Carn, U. Rutagarama The weakly magmatic Western <span class="hlt">rift</span> <span class="hlt">system</span>, East Africa, is marked by fault-bounded basins filled by freshwater lakes that record tectonic and climatic signals. One of the smallest of the African Great Lakes, Lake Kivu, represents a unique geohazard owing to the warm, saline bottom waters that are saturated in methane, as well as two of the most active volcanoes in Africa that effectively dam the northern end of the lake. Yet, the dynamics of the basin <span class="hlt">system</span> and the role of magmatism were only loosely constrained prior to new field and laboratory studies in Rwanda. In this work, we curated, merged, and analyzed historical and digital data sets, including spectral analyses of merged Shuttle Radar Topography Mission topography and high resolution CHIRP bathymetry calibrated by previously mapped fault locations along the margins and beneath the lake. We quantitatively compare these fault maps with the time-space distribution of earthquakes located using data from a temporary array along the northern sector of Lake Kivu, as well as space-based geodetic data. During 2012, seismicity rates were highest beneath Nyiragongo volcano, where a range of low frequency (1-3 s peak frequency) to tectonic earthquakes were located. Swarms of low-frequency earthquakes correspond to periods of elevated gas emissions, as detected by Ozone Monitoring Instrument (OMI). Earthquake swarms also occur beneath Karisimbi and Nyamuragira volcanoes. A migrating swarm of earthquakes in May 2012 suggests a sill intrusion at the DR Congo-Rwanda border. We delineate two fault sets: SW-NE, and sub-N-S. Excluding the volcano-tectonic earthquakes, most of the earthquakes are located along subsurface projections of steep border faults, and intrabasinal faults calibrated by seismic reflection data. Small magnitude earthquakes also occur beneath the uplifted <span class="hlt">rift</span> flanks. Time-space variations in seismicity patterns provide a baseline</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6082H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6082H"><span>Seismic hazard assessment of the Kivu <span class="hlt">rift</span> segment based on a new sismo-tectonic zonation model (Western Branch of the East African <span class="hlt">Rift</span> <span class="hlt">system</span>)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Havenith, Hans-Balder; Delvaux, Damien</p> <p>2015-04-01</p> <p>In the frame of the Belgian GeoRisCA multi-risk assessment project focused on the Kivu and Northern Tanganyika Region, a seismic hazard map has been produced for this area. It is based on a on a recently re-compiled catalogue using various local and global earthquake catalogues. The use of macroseismic epicenters determined from felt earthquakes allowed to extend the time-range back to the beginning of the 20th century, thus spanning about 100 years. The magnitudes have been homogenized to Mw and the coherence of the catalogue has been checked and validated. The seismo-tectonic zonation includes 10 seismic source areas that have been defined on the basis of the regional geological structure, neotectonic fault <span class="hlt">systems</span>, basin architecture and distribution of earthquake epicenters. The seismic catalogue was filtered by removing obvious aftershocks and Gutenberg-Richter Laws were determined for each zone. On the basis of this seismo-tectonic information and existing attenuation laws that had been established by Twesigomwe (1997) and Mavonga et al. (2007) for this area, seismic hazard has been computed with the Crisis 2012 (Ordaz et al., 2012) software. The outputs of this assessment clearly show higher PGA values (for 475 years return period) along the <span class="hlt">Rift</span> than the previous estimates by Twesigomwe (1997) and Mavonga (2007) while the same attenuation laws had been used. The main reason for these higher PGA values is likely to be related to the more detailed zonation of the <span class="hlt">Rift</span> structure marked by a strong gradient of the seismicity from outside the <span class="hlt">rift</span> zone to the inside. Mavonga, T. (2007). An estimate of the attenuation relationship for the strong ground motion in the Kivu Province, Western <span class="hlt">Rift</span> Valley of Africa. Physics of the Earth and Planetary Interiors 62, 13-21. Ordaz M, Martinelli F, Aguilar A, Arboleda J, Meletti C, D'Amico V. (2012). CRISIS 2012, Program for computing seismic hazard. Instituto de Ingeniería, Universidad Nacional Autónoma de M</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5872335','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5872335"><span>Age relationships for magmatic units of Mid-Continent <span class="hlt">rift</span> <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Van Schmus, W.R.</p> <p>1989-03-01</p> <p>K-Ar ages ranging from about 600 to 1000 Ma have recently been reported for gabbro and basalt recovered from the Texaco 1 Poersch well in Kansas. This has prompted suggestions that <span class="hlt">rift</span> magmatism there may be distinctly younger than that in the Lake Superior region, and that development of the <span class="hlt">rift</span> may have lasted several hundred million years. Review of ages from Keweenawan volcanic and plutonic rocks in the Lake Superior region shows that the best results are obtained from U-Pb analyses of zircon and baddeleyite; recent published results range from 1087 to 1108 Ma, with uncertainties on individual ages of /plus minus/ 4 m.y. This finding is consistent with earlier reported U-Pb zircon results. Virtually all other techniques are susceptible to geologic error and generally yield ages of significant less than 1100 Ma. The reliability decreases approximately in the sequence Rb-Sr (whole rock), K-Ar (biotite), Ar/sup 39/-Ar/sup 40/ (whole rock), K-Ar (whole rock), with fresh, coarse-grained plutonic rocks yielding older ages than altered, fine-grained volcanic rocks. K-Ar data on altered, fine-grained mafic rocks, therefore, are very poor indicators of original crystallization ages. Since the rocks from the Texaco 1 Poersch well are fine grained and slightly to moderately altered, their true ages are probably substantially older than 800-900 Ma. Interpretations based on the K-Ar ages from this well are ill advised; tectonic interpretation of the Mid-Continent <span class="hlt">rift</span> <span class="hlt">system</span> must wait for more accurate results. Several possibilities exist for obtaining more reliable ages from samples of the Poersch well and other, older wells in the region. These studies are in progress, and any available results will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJEaS.105.1779S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJEaS.105.1779S"><span>The East African <span class="hlt">Rift</span> <span class="hlt">System</span> and the impact of orographic changes on regional climate and the resulting aridification</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sommerfeld, Anja; Prömmel, Kerstin; Cubasch, Ulrich</p> <p>2016-09-01</p> <p>Several proxy data indicate an aridification of the East African climate during the Neogene, which might be influenced by the orographic changes of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS) induced by tectonic forcing during the last 20 million years. To investigate the impact of the orography and especially of the <span class="hlt">rifts</span>, the regional climate model CCLM is used, covering the EARS with Lake Victoria in the centre of the model domain. CCLM is driven by the ERA-Interim reanalysis and applied with a double-nesting method resulting in a very high spatial resolution of 7 km. The resolution clearly shows the shoulders and <span class="hlt">rifts</span> of the western and eastern branch of the EARS and the Rwenzoris within the western branch. To analyse the orographic influence on climate, a new technique of modifying the orography is used in this sensitivity study. The shoulders of the branches are lowered and the <span class="hlt">rifts</span> are elevated, resulting in a smoothed orography structure with less altitude difference between the shoulders and <span class="hlt">rifts</span>. The changes in 2 m-temperature are very local and associated with the changes in the orography. The vertically integrated moisture transport is characterised by less vortices, and its zonal component is increased over the branches. The resulting amount of precipitation is mainly decreased west of the western branch and increased in the <span class="hlt">rift</span> of the western branch. In the eastern branch, however, the changes in the amount of precipitation are not significant. The changes in the precipitation and temperature patterns lead to a shift of biomes towards a vegetation coverage characterised by more humid conditions in the northern part of the model domain and more arid conditions in the South. Thus, the aridification found in the proxy data can be attributed to the orographic changes of the <span class="hlt">rifts</span> only in the northern model domain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012SedG..281...21F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012SedG..281...21F"><span>Footwall progradation in syn-<span class="hlt">rift</span> carbonate platform-slope <span class="hlt">systems</span> (Early Jurassic, Northern Apennines, Italy)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fabbi, Simone; Santantonio, Massimo</p> <p>2012-12-01</p> <p>The so-called Umbria-Marche Domain of Northern Apennines represents a vast depositional <span class="hlt">system</span>, also stretching across the Adriatic Sea subsurface, that was characterized by dominantly pelagic sedimentation through most of its Jurassic to Oligocene/Early Miocene history. The pelagic succession is underlain by Hettangian shallow-water carbonates (Calcare Massiccio Fm.), constituting a regional carbonate platform that was subjected to tectonic extension due to <span class="hlt">rifting</span> of the Adria/African Plate in the earliest Jurassic. While tectonic subsidence of the hangingwalls drove the drowning of the platform around the Hettangian/Sinemurian boundary, the production of benthic carbonate on footwall blocks continued parallel to faulting, through a sequence of facies that was abruptly terminated by drowning and development of condensed pelagites in the early Pliensbachian. By then <span class="hlt">rifting</span> had ceased, so that the Pliensbachian to Early Cretaceous hangingwall deposits represent a post-<span class="hlt">rift</span> basin-fill succession onlapping the tectonically-generated escarpment margins of the highs. During the early phases of syndepositional faulting, the carbonate factories of footwall blocks were still temporarily able to fill part of the accommodation space produced by the normal faults by prograding into the incipient basins. In this paper we describe for the first time a relatively low-angle (< 10°) clinoform bed package documenting such an ephemeral phase of lateral growth of a carbonate factory. The clinoforms are sigmoidal, and form low-relief (maximum 5-7 m) bodies representing a shallow-water slope that was productive due to development of a Lithocodium-dominated factory. Continued faulting and hangingwall subsidence then decoupled the slope from the platform top, halting the growth of clinoforms and causing the platform margin to switch from accretionary to bypass mode as the pre-<span class="hlt">rift</span> substrate became exposed along a submarine fault escarpment. The downfaulted clinoform slope was then</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70015574','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70015574"><span>Mineralization potential along the trend of the Keweenawan- age Central North American <span class="hlt">Rift</span> <span class="hlt">System</span> in Iowa, Nebraska, and Kansas</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Berendsen, P.</p> <p>1989-01-01</p> <p>The tectonic and sedimentary environment of the Central North American <span class="hlt">Rift</span> <span class="hlt">System</span> (CNARS) provides an excellent setting for major mineral deposits. Major north-northeast-trending high-angle normal or reverse faults and northwest-trending transcurrent fault <span class="hlt">systems</span> may exercise control over ore forming processes. Gabbro and basalt are the dominant igneous rock types. Carbonatite and kimberlite occur in Nebraska and Kansas. Concentrations of Cu, Ni, Co, Ti, Au, Ag and PG minerals are known to occur in this setting. Arkosic sandstone, siltstone, shale, and minor carbonate units occur on top of the <span class="hlt">rift</span> basalts and in flanking basins where they may reach thicknesses of 10 km (6 miles). The potential for stratiform or unconformity-related metalliferous deposits should be considered. The <span class="hlt">rift</span> as a whole remains largely unexplored.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5993676','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5993676"><span>Stratigraphy of Mid-Continent <span class="hlt">rift</span> <span class="hlt">system</span> in Kansas as revealed by recent exploration wells</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Newell, K.D.; Berendsen, P.; Watney, W.L.; Doveton, J.H.; Steeples, D.</p> <p>1989-03-01</p> <p>The Texaco 1 Poersch well in Kansas (11,300 ft TD) was the first significant exploration test of the Mid-Continent <span class="hlt">Rift</span> <span class="hlt">System</span> (MRS). An upper succession of <span class="hlt">rift</span>-related rocks (2846-7429 ft) contains approximately 90% mafic igneous rocks with minor pegmatites and 10% oxidized siltstone and arkose. Arkose and subarkose with minor siltstone and shale make up 90% of a lower succession (7429 ft to TD). The remaining lower succession is composed of mafic igneous rocks. Mafic rocks are typically alkali basalts. Individual flows (detected by presence of amygdules, interflow sediments, compositional differences, and oxidized zones) range in thickness from 20 to 250 ft. Sedimentary rocks in the lower succession are divided into three sequences, each 1000-2000 ft thick. The sequences overlie relatively thin mafic flows or intrusives. Each sequence is generally composed of fining-upward units (50-150 ft thick) attributed to episodic movement and erosion of fault blocks in alluvial fan-dominated sedimentary environments. Shales and siltstones are too oxidized to be viable petroleum source rocks, but gray shale with approximately 0.5% total organic carbon was found in the MRS by the 1-4 Finn well, 21 mi to the northeast. Geologic examination of several shallower Precambrian tests holes near 1 Poersch shows considerable variability in sedimentary and tectonic settings along the MRS. Correlation between wells in Kansas and exposed areas of the MRS is still problematic. Additional wells will be necessary to better understand its hydrocarbon potential.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985Tecto...4..497S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985Tecto...4..497S"><span>The Najd Fault <span class="hlt">System</span>, Saudi Arabia and Egypt: a Late Precambrian <span class="hlt">Rift</span>-Related Transform <span class="hlt">System</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stern, Robert J.</p> <p>1985-08-01</p> <p>The Najd Fault <span class="hlt">System</span> is a complex set of left-lateral strike-slip faults and ductile shear zones that strike NW-SE across the Precambrian of Arabia and Egypt. This <span class="hlt">system</span> was developed during the interval 540-620 Ma. It is up to 400 km wide with an exposed length of 1100 km; inferred buried extensions of the Najd give it a total length of 2000 km. It is the best exposed and may be the largest pre-Mesozoic zone of transcurrent faulting on earth. Previous models for the Najd Fault <span class="hlt">System</span> suggest it formed as a result of a major Late Precambrian continent-continent collision. This model is not preferred here because (1) the lack of evidence for a pre-Late Precambrian continent to the east of the Najd Fault <span class="hlt">System</span>; (2) the difference between the orientation of the Najd Fault <span class="hlt">System</span> and that predicted by slip-line theory; (3) the younger age of Najd movements compared with that of collisional sutures in the Arabian Shield; and (4) lack of evidence for wide-spread crustal uplift that would be expected to accompany collision. A new model for the origin of the Najd Fault <span class="hlt">System</span> accounts for each of these objections: The Najd Fault <span class="hlt">System</span> formed in response to a broad zone of NW-SE directed crustal extension that accompanied juvenile continental crustal formation in northernmost Afro-Arabia. This model also accounts for the following observations: (1) Strands of the Najd parallel the direction of extension in the North Eastern Desert of Egypt and Sinai; (2) the timing of the principal <span class="hlt">rifting</span> movements (ca. 575-600 Ma) overlap with those of the Najd (ca. 560-620 Ma); (3) in spite of observation (2), the Najd Fault <span class="hlt">System</span> is not recognized in northernmost Afro-Arabia; instead the Najd deformation becomes increasingly ductile and these zones are more commonly intruded by sheared and foliated granites as the principal zone of extension is approached. The Najd Fault <span class="hlt">System</span> thus represents a set of continental transforms developed in response to a major episode of Late</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/878274','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/878274"><span>Calibration <span class="hlt">Systems</span> <span class="hlt">Final</span> Report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Myers, Tanya L.; Broocks, Bryan T.; Phillips, Mark C.</p> <p>2006-02-01</p> <p>The Calibration <span class="hlt">Systems</span> project at Pacific Northwest National Laboratory (PNNL) is aimed towards developing and demonstrating compact Quantum Cascade (QC) laser-based calibration <span class="hlt">systems</span> for infrared imaging <span class="hlt">systems</span>. These on-board <span class="hlt">systems</span> will improve the calibration technology for passive sensors, which enable stand-off detection for the proliferation or use of weapons of mass destruction, by replacing on-board blackbodies with QC laser-based <span class="hlt">systems</span>. This alternative technology can minimize the impact on instrument size and weight while improving the quality of instruments for a variety of missions. The potential of replacing flight blackbodies is made feasible by the high output, stability, and repeatability of the QC laser spectral radiance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://onlinelibrary.wiley.com/doi/10.1029/91JB02572/abstract','USGSPUBS'); return false;" href="http://onlinelibrary.wiley.com/doi/10.1029/91JB02572/abstract"><span>Variations in the reflectivity of the moho transition zone beneath the Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span> of North America: results from true amplitude analysis of GLIMPCE data</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hutchinson, Deborah R.; Lee, Myung W.; Behrendt, John C.; Cannon, William F.; Green, Adrian</p> <p>1992-01-01</p> <p>True amplitude processing of The Great Lakes International Multidisciplinary Program on Crustal Evolution seismic reflection data from the Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span> of North America shows large differences in the reflectivity of the Moho transition zone beneath the axial <span class="hlt">rift</span>, beneath the <span class="hlt">rift</span> flanks, and outside of the <span class="hlt">rift</span>. The Moho reflection from the axial <span class="hlt">rift</span> has a discontinuous, diffractive character marginally stronger (several decibels) than an otherwise transparent lower crust and upper mantle. Beneath the axial <span class="hlt">rift</span>, Moho is interpreted to be a synrift igneous feature. Beneath the <span class="hlt">rift</span> flanks, the reflectivity of the Moho transition is generally well developed with two identifiable boundaries, although in places it is weakly reflective to nonreflective, similar to Moho outside the <span class="hlt">rift</span>. The two boundaries are interpreted as the base of essentially intact, although stretched, prerift Archean crust (upper boundary) and new synrift Moho 1-2 s (6-7 km) deeper (lower boundary). Beneath the <span class="hlt">rift</span> flanks, the layered reflection Moho transition results from the preexisting crustal composition and fabric modified by synrift igneous processes and extensional tectonic/metamorphic processes. The geologic evidence for extensive basaltic magmatism in the <span class="hlt">rift</span> is the basis for interpreting the Moho signature as a Keweenawan structure that has been preserved for 1.1 b.y. Extension and magmatism appear to enhance reflectivity in the lower crust and Moho transition zone only where stretching factors are moderate (<span class="hlt">rift</span> flanks) and not where they are extreme (axial <span class="hlt">rift</span>). This leads to the prediction that the reflectivity across analogous volcanic passive continental margins should be greatest beneath the moderately stretched continental shelves and should decrease towards the ocean-continent boundary.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5930257','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5930257"><span>Continental <span class="hlt">rifts</span> and mineral resources</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Burke, K. . Geosciences Dept.)</p> <p>1992-01-01</p> <p>Continental <span class="hlt">rifts</span> are widespread and range in age from the present to 3 b.y. Individual <span class="hlt">rifts</span> may form parts of complex <span class="hlt">systems</span> as in E. Africa and the Basin and Range. <span class="hlt">Rifts</span> have originated in diverse environments such as arc-crests, sites of continental collision, collapsing mountain belts and on continents at rest over the mantle circulation pattern. Continental <span class="hlt">rift</span> resources can be classified by depth of origin: For example, in the Great Dike, Norilsk and Mwadui magma from the mantle is the host. At shallower depths continental crust partly melted above mafic magma hosts ore (Climax, Henderson). <span class="hlt">Rift</span> volcanics are linked to local hydrothermal <span class="hlt">systems</span> and to extensive zeolite deposits (Basin and Range, East Africa). Copper (Zambia, Belt), zinc (Red Dog) and lead ores (Benue) are related to hydrothermal <span class="hlt">systems</span> which involve hot rock and water flow through both pre-<span class="hlt">rift</span> basement and sedimentary and volcanic <span class="hlt">rift</span> fill. Economically significant sediments in <span class="hlt">rifts</span> include coals (the Gondwana of Inida), marine evaporites (Lou Ann of the Gulf of Mexico) and non-marine evaporites (East Africa). Oil and gas in <span class="hlt">rifts</span> relate to a variety of source, reservoir and trap relations (North Sea, Libya), but <span class="hlt">rift</span>-lake sediment sources are important (Sung Liao, Bo Hai, Mina, Cabinda). Some ancient iron ores (Hammersley) may have formed in <span class="hlt">rift</span> lakes but Algoman ores and greenstone belt mineral deposits in general are linked to oceanic and island arc environments. To the extent that continental environments are represented in such areas as the Archean of the Superior and Slave they are Andean Arc environments which today have locally <span class="hlt">rifted</span> crests (Ecuador, N. Peru). The Pongola, on Kaapvaal craton may, on the other hand represent the world's oldest preserved, little deformed, continental <span class="hlt">rift</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T31C4635D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T31C4635D"><span>Syn-<span class="hlt">Rift</span> <span class="hlt">Systems</span> of East Godavari Sub Basin: Its Evolution and Hydrocarbon Prospectivity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dash, J., Jr.; Zaman, B.</p> <p>2014-12-01</p> <p>Krishna Godavari (K.G.) basin is a passive margin basin developed along the Eastern coast of India. This basin has a polyhistoric evolution with multiple <span class="hlt">rift</span> <span class="hlt">systems</span>. <span class="hlt">Rift</span> basin exploration has provided the oil and gas industry with almost one third of discovered global hydrocarbon resources. Understanding synrift sequences, their evolution, depositional styles and hydrocarbon prospectivity has become important with recent discovery of the wells, G-4-6,YS-AF and KG-8 in the K.G. offshore basin. The East Godavari subbasin is a hydrocarbon producing basin from synrift and pre-<span class="hlt">rift</span> sediments, and hence this was selected as the study area for this research. The study has been carried out by utilizing data of around 58 wells (w1-w58) drilled in the study area 25 of which are hydrocarbon bearing with organic thickness varying from 200 m to 600 m. Age data generated by palaentology and palynology studies have been utilized for calibration of key well logs to differentiate between formations within prerift and synrift sediments. The electrologs of wells like resistivity, gamma ray, neutron, density and sonic logs have been utilized for correlation of different formations in all the drilled wells. The individual thicknesses of sand, shale and coal in the formations have been calculated and tabulated. For Golapalli formation, the isopach and isolith maps were generated which revealed that there were four depocentres with input from the north direction. Schematic geological cross sections were prepared using the well data and seismic data to understand the facies variation across the basin. The sedimentological and petrophysical analysis reports and electro log suites were referred to decipher the environment of deposition, the reservoir characteristics, and play types. The geochemical reports [w4 (Tmax)= 455-468 °C; w1 (Tmax) = 467-514 °C; w4(VRO)= 0.65-0.85; w1(VRO)= 0.83-1.13] revealed the source facies, its maturation and migration timings i.e. the petroleum <span class="hlt">systems</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997Tecto..16..425O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997Tecto..16..425O"><span>A shortened intraplate <span class="hlt">rift</span> <span class="hlt">system</span> in the Proterozoic Mount Isa terrane, NW Queensland, Australia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>O'Dea, Mark G.; Lister, Gordon S.; Betts, Peter G.; Pound, Katherine S.</p> <p>1997-06-01</p> <p>The Leichhardt River Fault Trough of the Mount Isa terrane developed a complex extensional architecture between approximately 1800 and 1600 Ma, forming the underlying template upon which compressional structures were superimposed during the 1590 to 1500 Ma Isan Orogeny. Basin-fill material accumulated during at least five multiphase periods of <span class="hlt">rifting</span> and associated postrift subsidence forming a stacked succession of unconformity-bounded sequences. Initial E-W extension was associated with a massive magmatic event. Half graben greater than 50 km in width and of alternating asymmetry localized the extrusion of up to 4 km of continental tholeiites. Thereafter a period of N-S extension resulted in southward tapering north tilted half graben in which synrift basaltic and siliciclastic strata accumulated. N-S extension was followed by regional postrift subsidence and the deposition of a laterally continuous quartzite-carbonate package. A multiphase period of E-W to NW-SE extension ensued during which time two unconformity-bounded sequences accumulated. The stratal architectures of these sequences are strongly asymmetric in cross section, exhibiting a pronounced rotational thickening toward the east, consistent with their deposition in the hanging walls of east dipping tilt blocks between 15 and 40 km in width. <span class="hlt">Finally</span>, a period of N-S extension resulted in the development of E-W trending F1 drag synclines in the highest level cover rocks. The association of angular unconformities and block-bounding faults, E-W trending synclines and E-W striking faults, and the unique internal fold geometries of fault blocks suggest that many fault-bounded blocks originated as coherent structural entities during <span class="hlt">rifting</span> and continued to act as such during subsequent shortening.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.6710L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.6710L"><span>The Okavango Dike Swarm (ODS) of Northern Botswana: Was it associated with a failed <span class="hlt">Rift</span> <span class="hlt">System</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>LePera, Alan; Atekwana, Estella; Abdelsalam, Mohamed</p> <p>2014-05-01</p> <p> basement extends to a depth of about 24km and is segmented into a number of along-strike magnetic bodies. The lack of significant crustal thinning below the ODS and poor relationship with the Precambrian basement fabric suggests either the ODS was not associated with a failed <span class="hlt">rift</span> <span class="hlt">system</span> or the remnants of the crustal disturbance have since been modified to depict a normal continental crust. The along-strike magnetic bodies conceivably represent mid-crustal feeder chambers, similar to those found in modern extensional environments such as Afar, or magma pooling zones developed along Proterozoic discontinuities. Due to the relative inconsistency of the magnetic anomaly below the swarm we speculate that a majority of the dikes are confined to the upper 5-10km of the crust. The ODS is thus interpreted to be a magma enhanced fissure network emplaced within the upper crust during an extensive period of regional tension induced by a continental wide upwelling of the asthenosphere caused by thermal incubation of the mantle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JGeo...49...19K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JGeo...49...19K"><span>Nonlinear geodynamics of the Baikal <span class="hlt">rift</span> <span class="hlt">system</span>: An evolution scenario with triple equilibrium bifurcation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klyuchevskii, Anatoly V.</p> <p>2010-01-01</p> <p>This is an attempt to analyze the current lithospheric stress pattern in the Baikal <span class="hlt">rift</span> in terms of nonlinear dynamics as an open self-organizing <span class="hlt">system</span> in order to gain more insights into the general laws of regional seismicity. According to the suggested approach, the stress pattern inferred from seismic moments of 70,000 MLH ≥ 2.0 events that occurred in the region between 1968 and 1994 is presented as a phase portrait in the phase spaces of the seismic moments. The obtained phase portrait of the <span class="hlt">system</span> evolution fits well a scenario with triple equilibrium bifurcation where stress bifurcations account for the frequency of M > 5.5 earthquakes. Extrapolation of the results into the nearest future indicates probability of such a bifurcation (a catastrophe of stress), i.e., there is growing risk that M ≈ 7 events may happen in the region within a few years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.2814A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.2814A"><span>Differentiating climatic- and tectonic-controlled lake margin in <span class="hlt">rift</span> <span class="hlt">system</span>: example of the Plio-Quaternary Nachukui Formation, Turkana depression, Kenya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexis, Nutz; Mathieu, Schuster; Abdoulaye, Balde; Jean-Loup, Rubino</p> <p>2016-04-01</p> <p>The Turkana Depression is part of the eastern branch of the East African <span class="hlt">Rift</span> <span class="hlt">System</span>. This area consists of several Oligo-Pliocene north-south oriented half-grabens that connect the Ethiopian and Kenyan <span class="hlt">rift</span> valleys. Exposed on the west side of the Lake Turkana, the Nachukui Formation represents a Plio-Quaternary syn-<span class="hlt">rift</span> succession mainly outcropping near the border fault of the North Lake basin. This Formation consists of a > 700 m thick fluvial-deltaic-lacustrine sediments deposited in this area between 4.2 and 0.5 Ma. In this contribution, we present preliminary results from the investigation of the complete succession based on field geology. Facies description and sequence analyses are provided focusing on lake margin evolution through time and deciphering their controlling factors. Two main types of facies association can be distinguished in the Nachukui Fm and reveal two main types of lake margins that alternatively developed in the Turkana basin. Type-1 is characterized by thick conglomeratic proximal alluvial fan fining laterally from the border fault to the central portion of the lake to gravelly distal alluvial fan. Conglomerate and gravel beds display recurrent wave reworking (ripples, clasts sorting, open-work), as well as intercalated shells placer and stromatolites beds. Laterally, facies rapidly grade to offshore siliciclastic muds. These facies are interpreted as aggrading and prograding coarse fan deltas that entered directly in the lake. Their subaqueous parts were then affected by waves and allowed the development of shell placers and stromatolite reefs. This facies association is generally included in thick packages representing long-term prograding trends of several hundred thousand years duration (> 500 ka). Type-2 is characterized by poorly developed alluvial fan near the border fault, rapidly grading laterally to a fluvial plain and then to well-developed wave-dominated coast (beaches, washover fans, coastal wedges), <span class="hlt">finally</span> connected to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JVGR..303..112M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JVGR..303..112M"><span><span class="hlt">Rift</span> zones and magma plumbing <span class="hlt">system</span> of Piton de la Fournaise volcano: How do they differ from Hawaii and Etna?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Michon, Laurent; Ferrazzini, Valérie; Di Muro, Andrea; Villeneuve, Nicolas; Famin, Vincent</p> <p>2015-09-01</p> <p>On ocean basaltic volcanoes, magma transfer to the surface proceeds by subvertical ascent from the mantle lithosphere through the oceanic crust and the volcanic edifice, possibly followed by lateral propagation along <span class="hlt">rift</span> zones. We use a 19-year-long database of volcano-tectonic seismic events together with detailed mapping of the cinder cones and eruptive fissures to determine the geometry and the dynamics of the magma paths intersecting the edifice of Piton de la Fournaise volcano. We show that the overall plumbing <span class="hlt">system</span>, from about 30 km depth to the surface, is composed of two structural levels that feed distinct types of <span class="hlt">rift</span> zones. The deep plumbing <span class="hlt">system</span> is rooted between Piton des Neiges and Piton de la Fournaise volcanoes and has a N30-40 orientation. Above 20 km below sea level (bsl), the main axis switches to a N120 orientation, which permits magma transfer from the lithospheric mantle to the base of the oceanic crust, below the summit of Piton de la Fournaise. The related NW-SE <span class="hlt">rift</span> zone is 15 km wide, linear, spotted by small to large pyroclastic cones and related lava flows and emits slightly alkaline magmas resulting from high-pressure fractionation of clinopyroxene ± olivine. This <span class="hlt">rift</span> zone has low magma production rate of ~ 0.5-3.6 × 10- 3 m3s- 1 and an eruption periodicity of around 200 years over the last 30 ka. Seismic data suggest that the long-lasting activity of this <span class="hlt">rift</span> zone result from regional NNE-SSW extension, which reactivates inherited lithospheric faults by the effect of underplating and/or thermal erosion of the mantle lithosphere. The shallow plumbing <span class="hlt">system</span> (< 11 km bsl) connects the base of the crust with the Central Cone. It is separated from the deep plumbing <span class="hlt">system</span> by a relatively large aseismic zone between 8 and 11 km bsl, which may represent a deep storage level of magma. The shallow plumbing <span class="hlt">system</span> feeds frequent, short-lived summit and flank (NE and SE flanks) eruptions along summit and outer <span class="hlt">rift</span> zones, respectively</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850053973&hterms=origin+crude+oil&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dorigin%2Bcrude%2Boil','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850053973&hterms=origin+crude+oil&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dorigin%2Bcrude%2Boil"><span><span class="hlt">Rift</span> basins - Origin, history, and distribution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Burke, K. C.</p> <p>1985-01-01</p> <p><span class="hlt">Rifts</span> are elongate depressions overlying places where the lithosphere has ruptured in extension. Where filled with sediment they may contain exploitable quantities of oil and gas. Because rits form in a variety of tectonic settings, it is helpful to define the particular tectonic environment in which a specific <span class="hlt">rift</span> or set of <span class="hlt">rifts</span> has developed. A useful approach has been to relate that environment to the Wilson Cycle of the opening and the closing of oceans. This appreciation of tectonic setting can help in better understanding of the depositional, structural and thermal history of individual <span class="hlt">rift</span> <span class="hlt">systems</span>. The global distribution of <span class="hlt">rifts</span> can also be related to tectonic environment. For example, <span class="hlt">rifts</span> associated with continental rupture at a temporary still-stand of a continent over the mantle convective <span class="hlt">system</span> (<span class="hlt">rifts</span> like those active in East Africa today) can be distinguished from those associated with continental collision (<span class="hlt">rifts</span> like the Cenozoic <span class="hlt">rifts</span> of China).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005IJEaS..94..594Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005IJEaS..94..594Z"><span>Evolution of the lithosphere in the area of the Rhine <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ziegler, P. A.; Dèzes, P.</p> <p>2005-09-01</p> <p>The Rhine <span class="hlt">Rift</span> <span class="hlt">System</span> (RRS) forms part of the European Cenozoic <span class="hlt">Rift</span> <span class="hlt">System</span> (ECRIS) and transects the Variscan Orogen, Permo-Carboniferous troughs and Late Permian to Mesozoic thermal sag basins. Crustal and lithospheric thicknesses range in the RRS area between 24 36 km and 50 120 km, respectively. We discuss processes controlling the transformation of the orogenically destabilised Variscan lithosphere into an end-Mesozoic stabilised cratonic lithosphere, as well as its renewed destabilisation during the Cenozoic development of ECRIS. By end-Westphalian times, the major sutures of the Variscan Orogen were associated with 45 60 km deep crustal roots. During the Stephanian-Early Permian, regional exhumation of the Variscides was controlled by their wrench deformation, detachment of subducted lithospheric slabs, asthenospheric upwelling and thermal thinning of the mantle-lithosphere. By late Early Permian times, when asthenospheric temperatures returned to ambient levels, lithospheric thicknesses ranged between 40 km and 80 km, whilst the thickness of the crust was reduced to 28 35 km in response to its regional erosional and local tectonic unroofing and the interaction of mantle-derived melts with its basal parts. Re-equilibration of the lithosphere-asthenosphere <span class="hlt">system</span> governed the subsidence of Late Permian-Mesozoic thermal sag basins that covered much of the RRS area. By end-Cretaceous times, lithospheric thicknesses had increased to 100 120 km. Paleocene mantle plumes caused renewed thermal weakening of the lithosphere. Starting in the late Eocene, ECRIS evolved in the Pyrenean and Alpine foreland by passive <span class="hlt">rifting</span> under a collision-related north-directed compressional stress field. Following end-Oligocene consolidation of the Pyrenees, west- and northwest-directed stresses originating in the Alps controlled further development of ECRIS. The RRS remained active until the Present, whilst the southern branch of ECRIS aborted in the early Miocene. Extensional</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26PSL.455...62M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26PSL.455...62M"><span>Spatio-temporal trends in normal-fault segmentation recorded by low-temperature thermochronology: Livingstone fault scarp, Malawi <span class="hlt">Rift</span>, East African <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mortimer, Estelle; Kirstein, Linda A.; Stuart, Finlay M.; Strecker, Manfred R.</p> <p>2016-12-01</p> <p>The evolution of through-going normal-fault arrays from initial nucleation to growth and subsequent interaction and mechanical linkage is well documented in many extensional provinces. Over time, these processes lead to predictable spatial and temporal variations in the amount and rate of displacement accumulated along strike of individual fault segments, which should be manifested in the patterns of footwall exhumation. Here, we investigate the along-strike and vertical distribution of low-temperature apatite (U-Th)/He (AHe) cooling ages along the bounding fault <span class="hlt">system</span>, the Livingstone fault, of the Karonga Basin of the northern Malawi <span class="hlt">Rift</span>. The fault evolution and linkage from <span class="hlt">rift</span> initiation to the present day has been previously constrained through investigations of the hanging wall basin fill. The new cooling ages from the footwall of the Livingstone fault can be related to the adjacent depocentre evolution and across a relay zone between two palaeo-fault segments. Our data are complimented by published apatite fission-track (AFT) data and reveal significant variation in rock cooling history along-strike: the centre of the footwall yields younger cooling ages than the former tips of earlier fault segments that are now linked. This suggests that low-temperature thermochronology can detect fault interactions along strike. That these former segment boundaries are preserved within exhumed footwall rocks is a function of the relatively recent linkage of the <span class="hlt">system</span>. Our study highlights that changes in AHe (and potentially AFT) ages associated with the along-strike displacement profile can occur over relatively short horizontal distances (of a few kilometres). This is fundamentally important in the assessment of the vertical cooling history of footwalls in extensional <span class="hlt">systems</span>: temporal differences in the rate of tectonically driven exhumation at a given location along fault strike may be of greater importance in controlling changes in rates of vertical exhumation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T21B2542Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T21B2542Y"><span>Crustal and mantle structure and anisotropy beneath the incipient segments of the East African <span class="hlt">Rift</span> <span class="hlt">System</span>: Preliminary results from the ongoing SAFARI</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Y.; Reed, C. A.; Gao, S. S.; Liu, K. H.; Massinque, B.; Mdala, H. S.; moidaki, M.; Mutamina, D. M.; Atekwana, E. A.; Ingate, S. F.; Reusch, A.; Barstow, N.</p> <p>2013-12-01</p> <p>Despite the vast wealth of research conducted toward understanding processes associated with continental <span class="hlt">rifting</span>, the extent of our knowledge is derived primarily from studies focused on mature <span class="hlt">rift</span> <span class="hlt">systems</span>, such as the well-developed portions of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS) north of Lake Malawi. To explore the dynamics of early <span class="hlt">rift</span> evolution, the SAFARI (Seismic Arrays for African <span class="hlt">Rift</span> Initiation) team deployed 50 PASSCAL broadband seismic stations across the Malawi, Luangwa, and Okavango <span class="hlt">rifts</span> of the EARS during the summer of 2012. The cumulative length of the profiles is about 2500 km and the planned recording duration is 2 years. Here we present the preliminary results of systematic analyses of data obtained from the first year of acquisition for all 50 stations. A total of 446 high-quality shear-wave splitting measurements using PKS, SKKS, and SKS phases from 84 teleseismic events were used to constrain fast polarization directions and splitting times throughout the region. The Malawi and Okavango <span class="hlt">rifts</span> are characterized by mostly NE trending fast directions with a mean splitting time of about 1 s. The fast directions on the west side of the Luangwa <span class="hlt">Rift</span> Zone are parallel to the <span class="hlt">rift</span> valley, and those on the east side are more N-S oriented. Stacking of approximately 1900 radial receiver functions reveals significant spatial variations of both crustal thickness and the ratio of crustal P and S wave velocities, as well as the thickness of the mantle transition zone. Stations situated within the Malawi <span class="hlt">rift</span> demonstrate a southward increase in observed crustal thickness, which is consistent with the hypothesis that the Malawi <span class="hlt">rift</span> originated at the northern end of the <span class="hlt">rift</span> <span class="hlt">system</span> and propagated southward. Both the Okavango and Luangwa <span class="hlt">rifts</span> are associated with thinned crust and increased Vp/Vs, although additional data is required at some stations to enhance the reliability of the observations. Teleseismic P-wave travel-time residuals show a delay of about</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1254465','SCIGOV-DOEDE'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1254465"><span>Hawaii <span class="hlt">Rifts</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/dataexplorer">DOE Data Explorer</a></p> <p>Nicole Lautze</p> <p>2015-01-01</p> <p><span class="hlt">Rifts</span> mapped through reviewing the location of dikes and vents on the USGS 2007 Geologic Map of the State of Hawaii, as well as our assessment of topography, and, to a small extent, gravity data. Data is in shapefile format.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=STS032-94-040&hterms=tea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dtea','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=STS032-94-040&hterms=tea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dtea"><span>East African <span class="hlt">Rift</span> Valley, Kenya</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1990-01-01</p> <p>This rare, cloud free view of the East African <span class="hlt">Rift</span> Valley, Kenya (1.5N, 35.5E) shows a clear view of the Turkwell River Valley, an offshoot of the African REift <span class="hlt">System</span>. The East African <span class="hlt">Rift</span> is part of a vast plate fracture which extends from southern Turkey, through the Red Sea, East Africa and into Mozambique. Dark green patches of forests are seen along the <span class="hlt">rift</span> margin and tea plantations occupy the cooler higher ground.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70014173','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70014173"><span>The Goodman swell: a lithospheric flexure caused by crustal loading along the Midcontinent <span class="hlt">rift</span> <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Peterman, Z.E.; Sims, P.K.</p> <p>1988-01-01</p> <p>Rb-Sr biotite ages of Archean and Early to Middle Proterozoic crystalline rocks in northern Wisconsin and adjacent Upper Peninsula of Michigan describe a regionally systematic pattern related to differential uplift. An "age low' occurs in northern Wisconsin where values range from 1070-1172 Ma for rocks with crystallization ages of 1760 to 1865 Ma. These values overlap with the main episode of mafic igneous activity (1090 to 1120 Ma) along the Midcontinent <span class="hlt">rift</span> <span class="hlt">system</span> (MRS). We interpret these low biotite ages as registering closure due to cooling below the 300??C isotherm as a consequence of uplift and rapid erosion of an area that we are informally naming the Goodman swell. We interpret the swell to be a forebulge imposed on an elastic crust by loading of mafic igneous rocks along and within the axis of the MRS. -from Authors</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910031351&hterms=rainy+season&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Drainy%2Bseason','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910031351&hterms=rainy+season&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Drainy%2Bseason"><span>Modelling <span class="hlt">Rift</span> Valley fever (RVF) disease vector habitats using active and passive remote sensing <span class="hlt">systems</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ambrosia, Vincent G.; Linthicum, K. G.; Bailey, C. L.; Sebesta, P.</p> <p>1989-01-01</p> <p>The NASA Ames Ecosystem Science and Technology Branch and the U.S. Army Medical Research Institute of Infectious Diseases are conducting research to detect <span class="hlt">Rift</span> Valley fever (RVF) vector habitats in eastern Africa using active and passive remote-sensing. The normalized difference vegetation index (NDVI) calculated from Landsat TM and SPOT data is used to characterize the vegetation common to the Aedes mosquito. Relationships have been found between the highest NDVI and the 'dambo' habitat areas near Riuru, Kenya on both wet and dry data. High NDVI values, when combined with the vegetation classifications, are clearly related to the areas of vector habitats. SAR data have been proposed for use during the rainy season when optical <span class="hlt">systems</span> are of minimal use and the short frequency and duration of the optimum RVF mosquito habitat conditions necessitate rapid evaluation of the vegetation/moisture conditions; only then can disease potential be stemmed and eradication efforts initiated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T43A4674Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T43A4674Y"><span>Exploring Crustal Structure and Mantle Seismic Anisotropy Associated with the Incipient Southern and Southwestern Branches of the East African <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Y.; Reed, C. A.; Gao, S. S.; Liu, K. H.; Massinque, B.; Mdala, H. S.; Chindandali, P. R. N.; Moidaki, M.; Mutamina, D. M.</p> <p>2014-12-01</p> <p>In spite of numerous geoscientific studies, the mechanisms responsible for the initiation and development of continental <span class="hlt">rifts</span> are still poorly understood. The key information required to constrain various geodynamic models on <span class="hlt">rift</span> initiation can be derived from the crust/mantle structure and anisotropy beneath incipient <span class="hlt">rifts</span> such as the Southern and Southwestern branches of the East African <span class="hlt">Rift</span> <span class="hlt">System</span>. As part of a National Science Foundation funded interdisciplinary project, 50 PASSCAL broadband seismic stations were deployed across the Malawi, Luangwa, and Okavango <span class="hlt">rift</span> zones from the summer of 2012 to the summer of 2014. Preliminary results from these 50 SAFARI (Seismic Arrays for African <span class="hlt">Rift</span> Initiation) and adjacent stations are presented utilizing shear-wave splitting (SWS) and P-S receiver function techniques. 1109 pairs of high-quality SWS measurements, consisting of fast polarization orientations and splitting times, have been obtained from a total of 361 seismic events. The results demonstrate dominantly NE-SW fast orientations throughout Botswana as well as along the northwestern flank of the Luangwa <span class="hlt">rift</span> valley. Meanwhile, fast orientations beneath the eastern Luangwa <span class="hlt">rift</span> flank rotate from NNW to NNE along the western border of the Malawi <span class="hlt">rift</span>. Stations located alongside the western Malawi <span class="hlt">rift</span> border faults yield ENE fast orientations, with stations situated in Mozambique exhibiting more E-W orientations. In the northern extent of the study region, fast orientations parallel the trend of the Rukwa and Usangu <span class="hlt">rift</span> basins. Receiver function results reveal that, relative to the adjacent Pan-African mobile belts, the Luangwa <span class="hlt">rift</span> zone has a thin (30 to 35 km) crust. The crustal thickness within the Okavango <span class="hlt">rift</span> basin is highly variable. Preliminary findings indicate a northeastward thinning along the southeast Okavango border fault <span class="hlt">system</span> congruent with decreasing extension toward the southwest. The Vp/Vs measurements in the Okavango basin are roughly</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995Tecto..14..531W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995Tecto..14..531W"><span>Cenozoic transtension along the Transantarctic Mountains-West Antarctic <span class="hlt">rift</span> boundary, southern Victoria Land, Antarctica, Ohio</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilson, Terry J.</p> <p>1995-04-01</p> <p>Brittle fault arrays mapped along the structural boundary between the Transantarctic Mountains and the West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span> are oriented obliquely to the axis of the mountains and offshore <span class="hlt">rift</span> basins. The north to northwest trending regional <span class="hlt">rift</span> boundary is thus not controlled by continuous <span class="hlt">rift</span> border faults. Instead, the <span class="hlt">rift</span> margin trend must be imposed by inherited lithospheric weaknesses along the ancestral East Antarctic craton margin. Fault kinematic solutions indicate that a dextral transtensional regime characterized the <span class="hlt">rift</span> boundary in the Cenozoic and that dominantly transcurrent motion occurred during the most recent faulting episode. The Transantarctic Mountains are considered to be a <span class="hlt">rift</span>-flank uplift, yet no substantial isostatic uplift is expected in a transtensional setting, and the mechanism of large-magnitude Cenozoic uplift of the mountains remains problematical. Regional deformation patterns in Victoria Land and the Ross Sea can be explained by a transtensional model and are not compatible with large-magnitude crustal stretching within the West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span> in the Cenozoic. The crustal thinning across the <span class="hlt">rift</span> <span class="hlt">system</span> more likely took place in the Mesozoic, when major West Antarctic crustal block motions occurred. The Cenozoic intracontinental deformation can be related to plate interaction resulting from the global Eocene plate reorganization, prior to the <span class="hlt">final</span> separation between Antarctica and a narrow salient of the southeastern Australian margin. Displacement magnitude was probably minor, and thus early Tertiary east-west Antarctic motion is unlikely to account for discrepancies in global plate motion circuits.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19198772','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19198772"><span>Tectonics of the baikal <span class="hlt">rift</span> deduced from volcanism and sedimentation: a review oriented to the Baikal and Hovsgol lake <span class="hlt">systems</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ivanov, Alexei V; Demonterova, Elena I</p> <p>2009-01-01</p> <p>As known from inland sedimentary records, boreholes, and geophysical data, the initiation of the Baikal <span class="hlt">rift</span> basins began as early as the Eocene. Dating of volcanic rocks on the <span class="hlt">rift</span> shoulders indicates that volcanism started later, in the Early Miocene or probably in the Late Oligocene. Prominent tectonic uplift took place at about 20 Ma, but information (from both sediments and volcanics) on the initial stage of the <span class="hlt">rifting</span> is scarce and incomplete. A comprehensive record of sedimentation derived from two stacked boreholes drilled at the submerged Akademichesky ridge indicates that the deep freshwater Lake Baikal existed for at least 8.4 Ma, while the exact formation of the lake in its roughly present-day shape and volume is unknown. Four important events of tectonic/environmental changes at about approximately 7, approximately 5, approximately 2.5, and approximately 0.1 Ma are seen in that record. The first event probably corresponds to a stage of <span class="hlt">rift</span> propagation from the historical center towards the wings of the <span class="hlt">rift</span> <span class="hlt">system</span>. <span class="hlt">Rifting</span> in the Hovsgol area was initiated at about this time. The event of ~5 Ma is a likely candidate for the boundary between slow and fast stages of <span class="hlt">rifting</span>. It is reflected in a drastic change of sedimentation rate due to isolation of the Akademichesky ridge from the central and northern Lake Baikal basins. The youngest event of 0.1 Ma is reflected by the (87)0Sr/ (86)Sr ratio increase in Lake Baikal waters and probably related to an increasing rate of mountain growth (and hence erosion) resulting from glacial rebounding. The latter is responsible for the reorganization of the outflow pattern with the termination of the paleo-Manzurka outlet and the formation of the Angara outlet. The event of approximately 2.5 Ma is reflected in the decrease of the (87)Sr/(86)Sr and Na/Al ratios in Lake Baikal waters. We suggest that it is associated with a decrease of the dust load due to a reorganization of the atmospheric circulations in Mainland</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JSAES..56....1B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JSAES..56....1B"><span>Lower Pliensbachian caldera volcanism in high-obliquity <span class="hlt">rift</span> <span class="hlt">systems</span> in the western North Patagonian Massif, Argentina</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Benedini, Leonardo; Gregori, Daniel; Strazzere, Leonardo; Falco, Juan I.; Dristas, Jorge A.</p> <p>2014-12-01</p> <p>In the Cerro Carro Quebrado and Cerro Catri Cura area, located at the border between the Neuquén Basin and the North Patagonian Massif, the Garamilla Formation is composed of four volcanic stages: 1) andesitic lava-flows related to the beginning of the volcanic <span class="hlt">system</span>; 2) basal massive lithic breccias that represent the caldera collapse; 3) voluminous, coarse-crystal rich massive lava-like ignimbrites related to multiple, steady eruptions that represent the principal infill of the <span class="hlt">system</span>; and, <span class="hlt">finally</span> 4) domes, dykes, lava flows, and lava domes of rhyolitic composition indicative of a post-collapse stage. The analysis of the regional and local structures, as well as, the architectures of the volcanic facies, indicates the existence of a highly oblique <span class="hlt">rift</span>, with its principal extensional strain in an NNE-SSW direction (˜N10°). The analyzed rocks are mainly high-potassium dacites and rhyolites with trace and RE elements contents of an intraplate signature. The age of these rocks (189 ± 0.76 Ma) agree well with other volcanic sequences of the western North Patagonian Massif, as well as, the Neuquén Basin, indicating that Pliensbachian magmatism was widespread in both regions. The age is also coincident with phase 1 of volcanism of the eastern North Patagonia Massif (188-178 Ma) represented by ignimbrites, domes, and pyroclastic rocks of the Marifil Complex, related to intraplate magmatism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoJI.201..505L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoJI.201..505L"><span>Stress pattern of the Shanxi <span class="hlt">rift</span> <span class="hlt">system</span>, North China, inferred from the inversion of new focal mechanisms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Bin; Atakan, Kuvvet; Sørensen, Mathilde Bøttger; Havskov, Jens</p> <p>2015-05-01</p> <p>Earthquake focal mechanisms of the Shanxi <span class="hlt">rift</span> <span class="hlt">system</span>, North China, are investigated for the time period 1965-April 2014. A total of 143 focal mechanisms of ML ≥ 3.0 earthquakes were compiled. Among them, 105 solutions are newly determined in this study by combining the P-wave first motions and full waveform inversion, and 38 solutions are from available published data. Stress tensor inversion was then performed based on the new database. The results show that most solutions in the Shanxi <span class="hlt">rift</span> <span class="hlt">system</span> exhibit normal or strike-slip faulting, and the regional stress field is transtensional and dominated by NNW-SSE extension. This correlates well with results from GPS data, geological field observations and levelling measurements across the faults. Heterogeneity exists in the regional stress field, as indicated by individual stress tensor inversions conducted for five subzones. While the minimum stress axis (σ3) appears to be consistent and stable, the orientations, especially the plunges, of the maximum and intermediate stresses (σ1 and σ2) vary significantly along the strike of the different subzones. Based on our results and combining multidisciplinary observations from geological surveys, GPS and cross-fault monitoring, a kinematic model is proposed for the Shanxi <span class="hlt">rift</span> <span class="hlt">system</span>, in which the <span class="hlt">rift</span> is situated between two opposite rotating crustal blocks, exhibiting a transtensional stress regimes. This model illustrates the present-day stress field and its correlation to the regional tectonics, as well as the current crustal deformation of the Shanxi <span class="hlt">rift</span> <span class="hlt">system</span>. Results obtained in this study, may help to understand the geodynamics, neotectonic activity, active seismicity and potential seismic hazard in this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.V31A2103T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.V31A2103T"><span><span class="hlt">Rifting</span> process of the Izu-Ogasawara-Mariana arc-backarc <span class="hlt">system</span> inferred from active source seismic studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takahashi, N.; Kodaira, S.; Miura, S.; Sato, T.; Yamashita, M.; No, T.; Takizawa, K.; Kaiho, Y.; Kaneda, Y.</p> <p>2008-12-01</p> <p>The Izu-Ogasawara-Mariana (IBM) arc-backarc <span class="hlt">system</span> has continued the crustal growth through crustal thickening by magmatic activities and crustal thinning by backarc opening. Tatsumi et al (2008) proposed petrological crustal growth model started from basaltic magmas rising from the slab, and showed the consistency with the seismic velocity model. Although crustal growth by the crustal thickening are modeled, crustal structural change by the backarc opening are not still unknown yet. The Shikoku Basin and Parece Vela Basin were formed by the backarc opening during approximately 15-30 Ma. Since 6 Ma, the Mariana Trough has opened and the stage already moved to spreading process from <span class="hlt">rifting</span> process. In the northern Izu-Ogasawara arc, the Sumisu <span class="hlt">rift</span> is in the initial <span class="hlt">rifting</span> stage. Therefore, understanding of the crustal change by the backarc opening from <span class="hlt">rifting</span> to spreading is indispensable to know the crustal growth of whole Izu-Ogasawara-Mariana island arc. Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has carried out seismic studies using a multichannel reflection survey <span class="hlt">system</span> and ocean bottom seismographs (OBSs) around the IBM arc since 2003 (Takahashi et al., 2007; Kodaira et al., 2007; Takahashi et al., 2008; Kodaira et al., 2008). We already obtained eight P-wave velocity models across the IBM arc and these structures record the crustal structural change during the backarc opening process from the <span class="hlt">rifting</span> stage to the spreading stage. As the results, we identified characteristics of the crustal structural change accompanied with backarc opening as follows. (1) Beneath the initial <span class="hlt">rifting</span> stage without normal faults, for example, in the northern tip of the Mariana Trough, crustal thickening are identified. (2) Beneath the initial <span class="hlt">rifting</span> stage with normal faults, for example, in the Sumisu <span class="hlt">Rift</span>, the crustal thickness is almost similar to that beneath the volcanic front. Although an existence of the crust-mantle transition layer with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP21A2221G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP21A2221G"><span>Constraining the Thermal History of the Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span> with Clumped Isotopes and Organic Thermal Maturity Indices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gallagher, T. M.; Sheldon, N. D.; Mauk, J. L.; Gueneli, N.; Brocks, J. J.</p> <p>2015-12-01</p> <p>The Mesoproterozoic (~1.1 Ga) North American Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span> (MRS) has been of widespread interest to researchers studying its economic mineral deposits, continental <span class="hlt">rifting</span> processes, and the evolution of early terrestrial life and environments. For their age, the MRS rocks are well preserved and have not been deeply buried, yet a thorough understanding of the regional thermal history is necessary to constrain the processes that emplaced the mineral deposits and how post-burial alteration may have affected various paleo-records. To understand the thermal history of the MRS better, this study presents carbonate clumped isotope (Δ47) temperatures from deposits on the north and south sides of the <span class="hlt">rift</span>. Due to the age of these deposits and known post-depositional processes, uncertainties exist about whether the clumped isotope signature has been reset. To test this, three generations of calcite were analyzed from the Nonesuch Fm. from the White Pine mine in Michigan including: sedimentary limestone beds, early diagenetic carbonate nodules, and hydrothermal calcite veins associated with the emplacement of copper mineralization. Clumped isotope temperatures from the White Pine mine range from 84 to 131°C, with a hydrothermal vein producing the hottest temperature. The clumped isotope temperature range for samples throughout the <span class="hlt">rift</span> expands to 41-134°C. The hottest temperatures are associated with areas of known copper mineralization, whereas the coolest temperatures are found on the northern arm of the <span class="hlt">rift</span> in Minnesota, far from known basin-bounding faults. Our hottest temperatures are broadly consistent with preexisting maximum thermal temperature estimates based on clay mineralogy, fluid inclusions, and organic geochemistry data. Clumped isotope results will also be compared to new hydrocarbon maturity data from the Nonesuch Fm., which suggest that bitumen maturities consistently fall within the early oil window across Michigan and Wisconsin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110023310','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110023310"><span>DoD-GEIS <span class="hlt">Rift</span> Valley Fever Monitoring and Prediction <span class="hlt">System</span> as a Tool for Defense and US Diplomacy</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anyamba, Assaf; Tucker, Compton J.; Linthicum, Kenneth J.; Witt, Clara J.; Gaydos, Joel C.; Russell, Kevin L.</p> <p>2011-01-01</p> <p>Over the last 10 years the Armed Forces Health Surveillance Center's Global Emerging Infections Surveillance and Response <span class="hlt">System</span> (GEIS) partnering with NASA'S Goddard Space Flight Center and USDA's USDA-Center for Medical, Agricultural & Veterinary Entomology established and have operated the <span class="hlt">Rift</span> Valley fever Monitoring and Prediction <span class="hlt">System</span> to monitor, predict and assess the risk of <span class="hlt">Rift</span> Valley fever outbreaks and other vector-borne diseases over Africa and the Middle East. This <span class="hlt">system</span> is built on legacy DoD basic research conducted by Walter Reed Army Institute of Research overseas laboratory (US Army Medical Research Unit-Kenya) and the operational satellite environmental monitoring by NASA GSFC. Over the last 10 years of operation the <span class="hlt">system</span> has predicted outbreaks of <span class="hlt">Rift</span> Valley fever in the Horn of Africa, Sudan, South Africa and Mauritania. The ability to predict an outbreak several months before it occurs provides early warning to protect deployed forces, enhance public health in concerned countries and is a valuable tool use.d by the State Department in US Diplomacy. At the international level the <span class="hlt">system</span> has been used by the Food and Agricultural Organization (FAD) and the World Health Organization (WHO) to support their monitoring, surveillance and response programs in the livestock sector and human health. This project is a successful testament of leveraging resources of different federal agencies to achieve objectives of force health protection, health and diplomacy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611128D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611128D"><span>Groundwater dynamics in the complex aquifer <span class="hlt">system</span> of Gidabo River Basin, southern Main Ethiopian <span class="hlt">Rift</span>: Evidences from hydrochemistry and isotope hydrology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Degu, Abraham; Birk, Steffen; Dietzel, Martin; Winkler, Gerfried; Moggessie, Aberra</p> <p>2014-05-01</p> <p>Located in the tectonically active Main Ethiopian <span class="hlt">Rift</span> <span class="hlt">system</span>, the Gidabo River Basin in Ethiopia has a complex hydrogeological setting. The strong physiographic variation from highland to <span class="hlt">rift</span> floor, variability in volcanic structures and disruption of lithologies by cross-cutting faults contribute for their complex nature of hydrogeology in the area. Until now, the groundwater dynamics and the impact of the tectonic setting on groundwater flow in this region are not well understood, though the local population heavily depends on groundwater as the major water supply. A combined approach based on hydrochemical and isotopic data was applied to investigate the regional flow dynamics of the groundwater and the impact of tectonic setting. Groundwater evolves from slightly mineralized Ca-Mg-HCO3 on the highland to highly mineralized Na-HCO3 dominating type in the deep <span class="hlt">rift</span> floor aquifers. δ18O and δD composition of groundwater show a general progressive enrichment from the highland to the <span class="hlt">rift</span> floor, except in thermal and deep <span class="hlt">rift</span> floor aquifers. Relatively the thermal and deep <span class="hlt">rift</span> floor aquifers are depleted and show similar signature to the groundwaters of highland, indicating groundwater inflow from the highland. Correspondingly, rising HCO3 and increasingly enriched signatures of δ 13C points to hydrochemical evolution of DIC and diffuse influx of mantle CO2 into the groundwater <span class="hlt">system</span>. Thermal springs gushing out along some of the fault zones, specifically in the vicinity of Dilla town, display clear influence of mantle CO2 and are an indication of the role of the faults acting as a conduit for deep circulating thermal water to the surface. By considering the known geological structures of the <span class="hlt">rift</span>, hydrochemical and isotopic data we propose a conceptual groundwater flow model by characterizing flow paths to the main <span class="hlt">rift</span> axis. The connection between groundwater flow and the impact of faults make this model applicable to other active <span class="hlt">rift</span> <span class="hlt">systems</span> with similar</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.V33C2649A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.V33C2649A"><span>Open <span class="hlt">system</span> evolution of trachyte and phonolite magmas from the East Africa <span class="hlt">Rift</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anthony, E. Y.; Espejel, V.</p> <p>2011-12-01</p> <p>The Quaternary Suswa volcanic <span class="hlt">system</span> consists of a large shield volcano that developed two nested summit calderas and erupted metaluminous to peralkaline trachyte and phonolite lavas and tuffs. Suswa is adjacent to the Greater Olkaria Volcanic Center, Longonot, Eburru, and Menengai volcanic <span class="hlt">systems</span>, which erupted trachyte, comendite, and pantellerite. These volcanoes comprise the Central Kenya Peralkaline Province and are the site of active geothermal energy production and exploration. Mafic to intermediate lavas (Elementieta, Ndabibi, and Lolonito-Akira-Tandamara volcanic fields) lie in the <span class="hlt">rift</span> floor between the shield volcanoes and occur as components of mixed magmas within the complexes. Suswa includes two suites of trachyte-phonolite lavas and tuffs. The first suite (C1) consists of lavas that built the original shield volcano and lavas and tuffs related to the formation of the first caldera; the second suite (C2) consists of lavas and tuffs erupted during and after the formation of the second caldera. Trachyte-carbonate immiscibility has been recorded in C1 ash flow units. The lavas and tuffs of the C2 suite are generally less peralkaline and more silica undersaturated than those of the C1 suite and did not share a common parental magma. Geochemical modeling precludes fractional crystallization as the sole process for Suswa magmas. Instead, assimilation of syenitic material (probably the crystal mush left over from C1 fractional crystallization), resorption, and mixing between the mafic to intermediate lavas satellite to the shield volcanoes have contributed to the composition and eruptive style of these volcanoes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.3695L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.3695L"><span>Stress Pattern of the Shanxi <span class="hlt">Rift</span> <span class="hlt">System</span>, North China, Inferred from the Inversion of New Focal Mechanisms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Bin; Sørensen, Mathilde; Atakan, Kuvvet; Havskov, Jens</p> <p>2015-04-01</p> <p>The Shanxi <span class="hlt">rift</span> <span class="hlt">system</span> is one of the most outstanding intra-plate transtensional fault zones in the North China block. Earthquake focal mechanisms of the <span class="hlt">rift</span> <span class="hlt">system</span> are investigated for the time period 1965 - Apr. 2014. A total of 143 focal mechanisms of ML ≥ 3.0 earthquakes were compiled. Among them, 105 solutions are newly determined by combining the P-wave first motions and full waveform inversion, and 38 solutions are from available published data. Stress tensor inversion was then performed based on the new database. The results show that most solutions exhibit normal or strike-slip faulting, and the regional stress field is transtensional and dominated by NNW-SSE extension. This correlates well with results from GPS data, geological field observations and leveling measurements across the faults. Heterogeneity exists in the regional stress field, as indicated by individual stress tensor inversions conducted for five subzones. While the minimum stress axis (σ3) appears to be consistent and stable, the orientations, especially the plunges, of the maximum and intermediate stresses (σ1 and σ2) vary significantly among the different subzones. Based on our results and combining multidisciplinary observations from geological surveys, GPS and cross-fault monitoring, a kinematic model is proposed, in which the Shanxi <span class="hlt">rift</span> <span class="hlt">system</span> is situated between two opposite rotating blocks, exhibiting a transtensional stress regime. This model illustrates the present-day stress field and its correlation with the regional tectonics, as well as the current crustal deformation of the Shanxi <span class="hlt">rift</span> <span class="hlt">system</span>. Results obtained in this study, may help to understand the geodynamics, neotectonic activity, active seismicity and potential seismic hazard in this region of North China.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017HydJ...25..519M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017HydJ...25..519M"><span>Groundwater flow dynamics in the complex aquifer <span class="hlt">system</span> of Gidabo River Basin (Ethiopian <span class="hlt">Rift</span>): a multi-proxy approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mechal, Abraham; Birk, Steffen; Dietzel, Martin; Leis, Albrecht; Winkler, Gerfried; Mogessie, Aberra; Kebede, Seifu</p> <p>2017-03-01</p> <p>Hydrochemical and isotope data in conjunction with hydraulic head and spring discharge observations were used to characterize the regional groundwater flow dynamics and the role of the tectonic setting in the Gidabo River Basin, Ethiopian <span class="hlt">Rift</span>. Both groundwater levels and hydrochemical and isotopic data indicate groundwater flow from the major recharge area in the highland and escarpment into deep <span class="hlt">rift</span> floor aquifers, suggesting a deep regional flow <span class="hlt">system</span> can be distinguished from the shallow local aquifers. The δ18O and δ2H values of deep thermal (≥30 °C) groundwater are depleted relative to the shallow (<60 m below ground level) groundwater in the <span class="hlt">rift</span> floor. Based on the δ18O values, the thermal groundwater is found to be recharged in the highland around 2,600 m a.s.l. and on average mixed with a proportion of 30 % shallow groundwater. While most groundwater samples display diluted solutions, δ13C data of dissolved inorganic carbon reveal that locally the thermal groundwater near fault zones is loaded with mantle CO2, which enhances silicate weathering and leads to anomalously high total dissolved solids (2,000-2,320 mg/l) and fluoride concentrations (6-15 mg/l) exceeding the recommended guideline value. The faults are generally found to act as complex conduit leaky barrier <span class="hlt">systems</span> favoring vertical mixing processes. Normal faults dipping to the west appear to facilitate movement of groundwater into deeper aquifers and towards the <span class="hlt">rift</span> floor, whereas those dipping to the east tend to act as leaky barriers perpendicular to the fault but enable preferential flow parallel to the fault plane.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6029E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6029E"><span>Characterization of basement highs in hyper-extended <span class="hlt">rift</span> <span class="hlt">systems</span>: examples from the Err nappe, SE Switzerland.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Epin, Marie-Eva; Manatschal, Gianreto; Haupert, Isabelle; Decarlis, Alessandro</p> <p>2015-04-01</p> <p>Despite of the fact that many studies investigated magma-poor <span class="hlt">rifted</span> margins, there are still open questions that are related to the nature of basement highs and the timing and processes related to their formation. While these questions are difficult to answer at present-day margins due to the lack of drill hole data, field analogues provide important insights and enable to find some answers to these questions. This is particularly true for the Err nappe in southeastern Switzerland, which is one of the world's few exposed and preserved <span class="hlt">rift</span>-related hyper-extended domains. This nappe preserves a <span class="hlt">rift</span> related extensional detachment <span class="hlt">system</span> that is exposed over more than 200km2, characterized by distinctive black gouges and green cataclasites and preserving the relation to its hanging wall and footwall rocks and the pre-, syn-, and post-tectonic sediments. The aim of our study was to investigate the 3D architecture of the detachment <span class="hlt">system</span> based on detailed mapping of this structure north and south of the Julier valley between Bivio and San Moritz in Central Grisons, SE Switzerland. Our results show the lateral variation of the morphology of the major detachment fault and its relation to extensional allochthons and the pre-, syn- and post-tectonic sediments. The main observation is that the architecture of the detachment <span class="hlt">system</span> changes over very short distance across the Julier valley. While in the north the detachment is overlain by an allochthonous block (e.g. the Bardella block), to the south this block disappears and the detachment fault is exhumed at the seafloor. The mapping of the syn-tectonic sediments show that they are thick in the north and get thinner to the south where they are locally absent and the post-<span class="hlt">rift</span> sediments directly overlie the detachment <span class="hlt">system</span>. Furthermore the syn-tectonic sediments are locally characterized by basement clasts. These relationships suggest a rapid change from a domain where the detachment is overlain by allochthons and thick</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70027062','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70027062"><span>A hydrogeologic model of stratiform copper mineralization in the Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span>, Northern Michigan, USA</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Swenson, J.B.; Person, M.; Raffensperger, J.P.; Cannon, W.F.; Woodruff, L.G.; Berndt, M.E.</p> <p>2004-01-01</p> <p>This paper presents a suite of two-dimensional mathematical models of basin-scale groundwater flow and heat transfer for the middle Proterozoic Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span>. The models were used to assess the hydrodynamic driving mechanisms responsible for main-stage stratiform copper mineralization of the basal Nonesuch Formation during the post-volcanic/pre-compressional phase of basin evolution. Results suggest that compaction of the basal aquifer (Copper Harbor Formation), in response to mechanical loading during deposition of the overlying Freda Sandstone, generated a pulse of marginward-directed, compaction-driven discharge of cupriferous brines from within the basal aquifer. The timing of this pulse is consistent with the radiometric dates for the timing of mineralization. Thinning of the basal aquifer near White Pine, Michigan, enhanced stratiform copper mineralization. Focused upward leakage of copper-laden brines into the lowermost facies of the pyrite-rich Nonesuch Formation resulted in copper sulfide mineralization in response to a change in oxidation state. Economic-grade mineralization within the White Pine ore district is a consequence of intense focusing of compaction-driven discharge, and corresponding amplification of leakage into the basal Nonesuch Formation, where the basal aquifer thins dramatically atop the Porcupine Mountains volcanic structure. Equilibrium geochemical modeling and mass-balance calculations support this conclusion. We also assessed whether topography and density-driven flow <span class="hlt">systems</span> could have caused ore genesis at White Pine. Topography-driven flow associated with the Ottawan orogeny was discounted because it post-dates main-stage ore genesis and because recent seismic interpretations of basin inversion indicates that basin geometry would not be conductive to ore genesis. Density-driven flow <span class="hlt">systems</span> did not produce focused discharge in the vicinity of the White Pine ore district.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/7036216','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/7036216"><span>Probing the processes and products of an ancient continental crustal rupture: Scientific drillng into the Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hinz, W.J.</p> <p>1988-01-01</p> <p>Geochemical and geophysical investigations over the past decade suggest a laterally as well radially heterogeneous upper mantle. The sources of this variability are mantle dynamics and interactions with the crust. The opportunities to sample these variations directly are limited within continental regions. However, the basalts of the Midcontinent <span class="hlt">Rift</span> (MCR) <span class="hlt">System</span> of North America are particularly attractive for studying subcontinental mantle. The MCR is an 1100 Ma paleorift that extends for more than 2000 km across the North American midcontinent. Drill holes into the MCR to obtain samples of the basalt can be located to answer critical questions regarding the origin and evolution of this aborted Precambrian <span class="hlt">rift</span>. Outcrops of the MCR rocks occur only in the Lake Superior region, and the rocks that crop out are restricted largely to the margins of the structure and the upper part of the stratigraphic section. Available drill holes are shallow and poorly distributed for scientific purposes and provide only limited samples for analysis. Many sites along the <span class="hlt">rift</span> have been pinpointed where holes of 5 km or less in depth can be drilled to sample the Proterozoic (Keweenawan) igneous rocks of the <span class="hlt">rift</span>. In September, 1987, approximately 90 geoscientists from North America and Europe met in Duluth, Minnesota, for a workshop. The goals of the workshop were to define the scientific objectives of drilling the MCR and to develop a plan for achieving these objectives. As a result of the workshop and subsequent deliberations, we proposed a multi-year, multi-hole program of drilling and related scientific investigation of the MCR utilizing shallow to intermediate depth holes. 18 refs. 5 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T53B4674B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T53B4674B"><span><span class="hlt">Rift</span> Fault Geometry and Distribution in Layered Basaltic Rocks: A Comparison Between the Koa'e (Hawai'i) and Krafla (Iceland) Fault <span class="hlt">Systems</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bubeck, A.; Walker, R. J.; MacLeod, C. J.; Imber, J.</p> <p>2014-12-01</p> <p>Fault <span class="hlt">systems</span> within incipient <span class="hlt">rifts</span> that cut basaltic rocks comprise an array of fine-scale structures, including networks of fractures and small displacement (<15 m) faults that accommodate regional extension. These zones of damaged rock have mechanical and physical properties distinct from the surrounding intact host rock. As the <span class="hlt">rift</span> <span class="hlt">system</span> evolves this early-formed damage can be reactivated, and influence the distribution and growth of new fractures. Constraining the role of this inter-fault deformation in <span class="hlt">rift</span> zone development is therefore important to characterizing the regional distribution of extensional strains, and the evolving physical and fluid flow properties of the host rock. Here we use high resolution field and remote mapping of the Koa'e insipient <span class="hlt">rift</span> fault <span class="hlt">system</span> on the south flank of Kilauea Volcano on Hawaii's Big Island, and the Krafla <span class="hlt">rift</span> <span class="hlt">system</span>, Iceland, to investigate the evolution of segmented <span class="hlt">rift</span> fault <span class="hlt">systems</span> in layered basalts, formed at low confining pressures. Extension in the Koa'e <span class="hlt">system</span> is accommodated dominantly by interaction of zones of opening-mode fractures and areas of surface flexure rather than surface-breaching normal faults, which is attributed to gravitational collapse of Kilauea. Extension in the Krafla <span class="hlt">system</span> is localised on segmented, large displacement (>20 m) normal faults, the development of which may have been controlled by dyke emplacement. Preliminary comparison between the Koa'e and Krafla <span class="hlt">systems</span> suggests that strain rate and/or the effective stress path plays a primary role in controlling the geometry, characteristics, and distribution of major faults, and the scale and distribution of secondary (oblique) brittle structures within <span class="hlt">rift</span> zones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T11F..02G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T11F..02G"><span>Evolution of bimodal volcanism in Gona, Ethiopia: geochemical associations and geodynamic implications for the East African <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghosh, N.; Basu, A. R.; Gregory, R. T.; Richards, I.; Quade, J.; Ebinger, C. J.</p> <p>2013-12-01</p> <p>The East African <span class="hlt">rift</span> <span class="hlt">system</span> in Ethiopia formed in the Earth's youngest flood basalt province, and provides a natural laboratory to study the geochemistry of bimodal volcanism and its implications for plume-derived magmatism, mantle-lithosphere interactions and evolution of continental <span class="hlt">rifts</span> from plate extension to rupture. Our geochemical studies of the ~6 Ma to recent eruptive products from Gona within the Afar <span class="hlt">Rift</span> Zone are understood in context of crustal and upper mantle seismic imaging studies that provide constraints on spatial variations. Geochemical (major element, trace element and isotope) analyses of basalts and rhyolitic tuff from Gona indicate a common magma source for these bimodal volcanics. Light rare earth elements (LREEs) are enriched with a strong negative Eu anomaly and a positive Ce anomaly in some of the silicic volcanic rocks. We observe strong depletions in Sr and higher concentrations of Zr, Hf, Th, Nb and Ta. We hypothesize that the silicic rocks may be residues from a plume-derived enriched magma source, following partial melting with fractional crystallization of plagioclase at shallow magma chambers. The absence of Nb-Ta anomaly shows no crustal assimilation by magmas. Sr isotopes, in conjunction with Nd and Pb isotopes and a strong Ce anomaly could reflect interaction of the parent magma with a deep saline aquifer or brine. Nd isotopic ratios (ɛNd = 1.9 to 4.6) show similarity of the silicic tuffs and basalts in their isotopic compositions except for some ~6 Ma lavas showing MORB-like values (ɛNd = 5 to 8.7) that suggest involvement of the asthenosphere with the plume source. Except for one basaltic tuff, the whole rock oxygen isotopic ratios of the Gona basalts range from +5.8‰ to +7.9‰, higher than the δ values for typical MORB, +5.7. The oxygen isotopes in whole rocks from the rhyolite tuffs vary from 14.6‰ to 20.9‰ while their Sr isotope ratios <0.706, indicative of post-depositional low T alteration of these silicic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6614I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6614I"><span>Hydrogeological structure of a seafloor hydrothermal <span class="hlt">system</span> related to backarc <span class="hlt">rifting</span> in a continental margin setting</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ishibashi, Jun-ichiro</p> <p>2016-04-01</p> <p>Seafloor hydrothermal <span class="hlt">systems</span> in the Okinawa Trough backarc basin are considered as related to backarc <span class="hlt">rifting</span> in a continental margin setting. Since the seafloor is dominantly covered with felsic volcaniclastic material and/or terrigenous sediment, hydrothermal circulation is expected to be distributed within sediment layers of significantly high porosity. Deep drilling through an active hydrothermal field at the Iheya North Knoll in the middle Okinawa Trough during IODP Expedition 331 provided a unique opportunity to directly access the subseafloor. While sedimentation along the slopes of the knoll was dominated by volcanic clasts of tubular pumice, intense hydrothermal alteration was recognized in the vicinity of the hydrothermal center even at very shallow depths. Detailed mineralogical and geochemical studies of hydrothermal clay minerals in the altered sediment suggest that the prevalent alteration is attributed to laterally extensive fluid intrusion and occupation within the sediment layer. Onboard measurements of physical properties of the obtained sediment revealed drastic changes of the porosity caused by hydrothermal interactions. While unaltered sediment showed porosity higher than 70%, the porosity drastically decreased in the layer of anhydrite formation. On the other hand, the porosity remained high (~50%) in the layer of only chlorite alteration. Cap rock formation caused by anhydrite precipitation would inhibit the ascent of high temperature fluids to the seafloor. Moreover, an interbedded nature of pelagic mud units and matrix-free pumice deposits may prompt formation of a tightly layered architecture of aquifers and aquicludes. This sediment architecture should be highly conducive to lateral flow pseudo-parallel to the surface topography. Occurrence of sphalerite-rich sulfides was recognized as associated with detrital and altered sediment, suggesting mineralization related to subsurface chemical processes. Moreover, the vertical profiles of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.V24B..06L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.V24B..06L"><span>Patterns of Volcanism Associated With Oligocene to Recent Dome Uplift, West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Le Masurier, W. E.</p> <p>2005-12-01</p> <p>The Marie Byrd Land dome lies on the Pacific coast of the West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span>. It is a structural dome defined by elevations of a low-relief erosion surface that is exposed in fault- block nunataks. The dome has roughly 3000 m of structural relief and is about 800 km in diameter.The growth of the dome has been closely associated with two rather unusual patterns of volcanic activity that provide keys to the timing and rate of uplift. (1) The ages of basaltic rocks that rest on the erosion surface become systematically older with increasing elevation of the surface, e.g. 6.27 Ma at 600 m elevation, 27 Ma at 2700 m, etc., suggesting that uplift began around 27 Ma and continued to 6 Ma at roughly 100m/m.y. (2) The oldest of 18 felsic shield volcanoes formed around 19 Ma at the dome crest. The remaining felsic volcanoes become systematically younger toward the distal flanks of the dome, along linear, fault-controlled, N-S and E-W chains. Late Pleistocene (active) volcanoes lie at the north, south, east, and west margins of the dome, suggesting that uplift proceeded systematically from 19 Ma to the present by centrifugal extension of relict fractures during uplift, accompanied by the rise of felsic magmas from crustal reservoirs. Teleseismic studies (Winberry and Anandakrishnan, 2004) show that the crust has been thinned over the dome crest, and that the dome is supported by low density mantle. Tomographic images near the dome (Sieminski, et al., 2003) show a low velocity column extending down to the transition zone. The Antarctic plate has been stationary at least since the Eocene. In the apparent absence of a mechanism driven by plate tectonics, it is reasonable to infer that mantle plume activity has produced these spatial and temporal patterns of volcanism focused around dome uplift, rather than the more familiar linear volcanic chains associated with moving plates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1987Tectp.141...33K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1987Tectp.141...33K"><span>Structural geometry and evolution of the Dead Sea-Jordan <span class="hlt">rift</span> <span class="hlt">system</span> as deduced from new subsurface data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kashai, E. L.; Croker, P. F.</p> <p>1987-09-01</p> <p>Analysis of deep drilling data and seismic reflection surveys obtained in recent years permit establishment of a tectonic model of the Dead Sea-Jordan <span class="hlt">rift</span> <span class="hlt">system</span> that is in part conformable with some of the many, often controversial, theories on this subject, but which also introduces new information negating some concepts that are widely accepted in the literature. The Dead Sea-Jordan <span class="hlt">rift</span> <span class="hlt">system</span> is not a tensional graben between two parallel sets of faults, but instead can be best defined as a sinistral transform connecting an incipient oceanic ridge—the Red Sea—with an upthrusted collision zone, the Taurus range. The shear is caused by the opening of the Red Sea and the motion of the Arabian sub-plate away from the African plate. The shearing occurs along a largely south-north trending, slightly arcuate Une, consisting of a series of en echelon left-stepping left-lateral strike-slip master faults of varying lengths. These faults characteristically die out to the north by bending outward (northeast), and the movement is taken up by the strike-slip faults to the left (i.e. to the west). Where overlap of the two faults occurs, very narrow and very deep grabens have evolved, in places the width being equal to the depth. The narrowness of these grabens is dictated by the closeness of the overlapping segments of the successive strike-slip faults. This feature points to the probability that the en echelon strike-slip faults have a common root zone at great depth. These grabens are not typical "leaky" pull-aparts in that they have no gravimetric, magnetic or heat flow anomalies; nor are they closed on all four sides by large faults. Their northern ends are characterized by gradually rising graben floors without major diagonal cross faults. The Dead Sea-Jordan <span class="hlt">rift</span> <span class="hlt">system</span> sensu stricto extends over a distance of 420 km, from the northern shore of the Gulf of Elat to the northern margin of the Hula Valley. Southward, it is connected with the Red Sea along the Gulf of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850056208&hterms=Cenozoic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DCenozoic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850056208&hterms=Cenozoic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DCenozoic"><span>Cenozoic <span class="hlt">rift</span> formation in the northern Caribbean</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mann, P.; Burke, K.</p> <p>1984-01-01</p> <p><span class="hlt">Rifts</span> form in many different tectonic environments where the lithosphere is put into extension. An outline is provided of the distribution, orientation, and relative ages of 16 Cenozoic <span class="hlt">rifts</span> along the northern edge of the Caribbean plate and it is suggested that these structures formed successively by localized extension as the Caribbean plate moved eastward past a continental promontory of North America. Evidence leading to this conclusion includes (1) recognition that the <span class="hlt">rifts</span> become progressively younger westward; (2) a two-phase subsidence history in a <span class="hlt">rift</span> exposed by upthrusting in Jamaica; (3) the absence of <span class="hlt">rifts</span> east of Jamaica; and (4) the observation that removal of 1400 km of strike-slip displacement on the Cayman Trough fault <span class="hlt">system</span> places the Paleogene <span class="hlt">rifts</span> of Jamaica in an active area of extension south of Yucatan where the <span class="hlt">rifts</span> of Honduras and Guatemala are forming today.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T44C..05B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T44C..05B"><span>Miocene Onset of Extension in the Turkana Depression, Kenya: Implications for the Geodynamic Evolution of the East African <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boone, S.; Gleadow, A. J. W.; Kohn, B. P.; Seiler, C.</p> <p>2015-12-01</p> <p>The Paleogene-Recent East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS) is the foremost modern example of continental <span class="hlt">rifting</span>, providing much of our understanding of the early stages of continental breakup. The EARS traverses two regions of crustal uplift, the Ethiopian and East African Domes, separated by the Turkana Depression. This wide region of subdued topography coincides with the NW-SE trend of the Jurassic-Paleogene Anza <span class="hlt">Rift</span>. Opinions on the fundamental geodynamic driver for EARS <span class="hlt">rifting</span> are divided, however, principally between models involving migrating plume(s) and a single elongated 'superplume'. While competing models have similar topographic outcomes, they predict different morphotectonic evolutions for the Turkana Depression. Models inferring southward plume-migration imply that the plume must have passed below the Turkana Depression during the Paleogene, in order to have migrated to the East African Dome by the Miocene. The possible temporal denudational response to such plume activity is testable using low temperature thermochronology. We present apatite fission track (AFT) and (U-Th)/He (AHe), and zircon (U-Th)/He (ZHe) data from the Lapurr Range, an uplifted Precambrian basement block in northern Turkana. Low radiation damage ZHe results displaying an age range of ~70-210 Ma, and combined with stratigraphic evidence, suggest ~4-6 km of Jurassic-Early Cretaceous denudation, probably associated with early Anza <span class="hlt">Rift</span> tectonism. AFT ages of ~9-15 Ma imply subsequent burial beneath no more than ~4 km of overburden, thus preserving the Jurassic-Cretaceous ZHe ages. Together with AFT results, AHe data (~3-19 Ma) support ~2-4 km of Miocene-Pliocene uplift of the Lapurr Range in the footwall of the E-dipping Lapurr normal fault. Miocene AFT and AHe ages are interpreted to reflect the initiation of the EARS in the Turkana Depression. If extension is associated with plume activity, then upwelling in the Turkana region is unlikely to have started prior to the Miocene, much</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6064904','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6064904"><span>Pre-breakup geology of the Gulf of Mexico-Caribbean: Its relation to Triassic and Jurassic <span class="hlt">rift</span> <span class="hlt">systems</span> of the region</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bartok, P. )</p> <p>1993-02-01</p> <p>A review of the pre-breakup geology of west-central Pangea, comprised of northern South America, Gulf of Mexico and West Africa, combined with a study of the Mesozoic <span class="hlt">rift</span> trends of the region confirms a relation between the <span class="hlt">rift</span> <span class="hlt">systems</span> and the underlying older grain of deformation. The pre-breakup analysis focuses attention on the Precambrian, Early Paleozoic and Late Paleozoic tectonic events affecting the region and assumes a Pindell fit. Two Late Precambrian orogenic belts are observed in the west central Pangea. Along the northern South American margin and Yucatan a paleo northeast trending Pan-African aged fold belt is documented. A second <span class="hlt">system</span> is observed along West Africa extending from the High Atlas to the Mauritanides and Rockelides. During the Late Paleozoic, renewed orogenic activity, associated with the Gondwana/Laurentia suture, affected large segments of west central Pangea. The general trend of the <span class="hlt">system</span> is northeast-southwest and essentially parallels the Gyayana Shield, West African, and eastern North American cratons. Mesozoic <span class="hlt">rifting</span> closely followed either the Precambrian trends or the Late Paleozoic orogenic belt. The Triassic component focuses along the western portions of the Gulf of Mexico continuing into eastern Mexico and western South America. The Jurassic <span class="hlt">rift</span> trend followed along the separation between Yucatan and northern South America. At Lake Maracaibo the Jurassic <span class="hlt">rift</span> <span class="hlt">system</span> eventually overlaps the Triassic <span class="hlt">rifts</span>. The Jurassic <span class="hlt">rift</span> resulted in the [open quotes]Hispanic Corridor[close quotes] that permitted Tethyan and Pacific marine faunas to mix at a time when the Gulf of Mexico underwent continental sedimentation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JAfES..59..168A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JAfES..59..168A"><span>Influence of pre-existing fabrics on fault kinematics and <span class="hlt">rift</span> geometry of interacting segments: Analogue models based on the Albertine <span class="hlt">Rift</span> (Uganda), Western Branch-East African <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aanyu, K.; Koehn, D.</p> <p>2011-02-01</p> <p>This study aims at showing how far pre-existing crustal weaknesses left behind by Proterozoic mobile belts, that pass around cratonic Archean shields (Tanzania Craton to the southeast and Congo Craton to the northwest), control the geometry of the Albertine <span class="hlt">Rift</span>. Focus is laid on the development of the Lake Albert and Lake Edward/George sub-segments and between them the greatly uplifted Rwenzori Mountains, a horst block located within the <span class="hlt">rift</span> and whose highest peak rises to >5000 m above mean sea level. In particular we study how the southward propagating Lake Albert sub-segment to the north interacts with the northward propagating Lake Edward/George sub-segment south of it, and how this interaction produces the structures and geometry observed in this section of the western branch of the East African <span class="hlt">Rift</span>, especially within and around the Rwenzori horst. We simulate behaviour of the upper crust by conducting sandbox analogue experiments in which pre-cut rubber strips of varying overstep/overlap connected to a basal sheet and oriented oblique and/or orthogonal to the extension vector, are placed below the sand-pack. The points of connection present velocity discontinuities to localise deformation, while the rubber strips represent ductile domain affected by older mobile belts. From fault geometry of developing <span class="hlt">rift</span> segments in plan view and section cuts, we study kinematics resulting from a given set of boundary conditions, and results are compared with the natural scenario. Three different basal model-configurations are used to simulate two parallel <span class="hlt">rifts</span> that propagate towards each other and interact. Wider overstep (model SbR3) produces an oblique transfer zone with deep grabens (max. 7.0 km) in the adjoining segments. Smaller overlap (model SbR4) ends in offset <span class="hlt">rift</span> segments without oblique transfer faults to join the two, and produces moderately deep grabens (max. 4.6 km). When overlap doubles the overstep (model SbR5), <span class="hlt">rifts</span> propagate sub-orthogonal to the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70020527','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70020527"><span>The provenance and chemical variation of sandstones associated with the Mid-continent <span class="hlt">Rift</span> <span class="hlt">System</span>, U.S.A.</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Cullers, R.L.; Berendsen, P.</p> <p>1998-01-01</p> <p>Sandstones along the northern portion of the Precambrian Mid-continent <span class="hlt">Rift</span> <span class="hlt">System</span> (MRS) have been petrographically and chemically analyzed for major elements and a variety of trace elements, including the REE. After the initial extrusion of the abundant basalts along the MRS, dominantly volcaniclastic sandstones of the Oronto Group were deposited. These volcaniclastic sandstones are covered by quartzose and subarkosic sandstones of the Bayfield Group. Thus the sandstones of the Oronto Group were derived from previously extruded basalts, whereas, the sandstones of the Bayfield Group were derived from Precambrian granitic gneisses located on the <span class="hlt">rift</span> flanks. The chemical variation of these sandstones closely reflects the changing detrital modes with time. The elemental composition of the sandstones confirms the source lithologies suggested by the mineralogy and clasts. The Oronto Group sandstones contain lower ratios of elements concentrated in silicic source rocks (La or Th) relative to elements concentrated in basic source rocks (Co, Cr, or Sc) than the Bayfield Group. Also, the average size of the negative Eu anomaly of the sandstones of the Oronto Group is significantly less (Eu/Eu* mean ?? standard deviation = 0.79 ?? 0.13) than that of the Bayfield Group (mean + standard deviation = 0.57 ?? 0.09), also suggesting a more basic source for the former than the latter. Mixing models of elemental ratios give added insight as to the evolution of the <span class="hlt">rift</span>. These models suggest that the volcanistic sandstones of the lower portion of the Oronto Group are derived from about 80 to 90 percent basalt and 10 to 20 percent granitoids. The rest of the Oronto Group and the lower to middle portion of the Bayfield Group could have formed by mixing of about 30 to 60 percent basalt and 40 to 70 percent granitoids. The upper portion of the Bayfield Group is likely derived from 80 to 100 percent granitoids and zero to 20 percent basalt.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JAfES..57..345K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JAfES..57..345K"><span>Active fault segments as potential earthquake sources: Inferences from integrated geophysical mapping of the Magadi fault <span class="hlt">system</span>, southern Kenya <span class="hlt">Rift</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuria, Z. N.; Woldai, T.; van der Meer, F. D.; Barongo, J. O.</p> <p>2010-06-01</p> <p> uplifted, heavily fractured and deformed basin to the north (highly disturbed magnetic signatures) characteristic of on going active <span class="hlt">rifting</span>; and a refined architecture of the asymmetry graben to the south with an intrarift horst, whose western graben is 4 km deep and eastern graben is much deeper (9 km), with a zone of significant break in magnetic signatures at that depth, interpreted as source of the hot springs south of Lake Magadi (a location confirmed near surface by ground magnetic and resistivity data sets). The magnetic sources to the north are shallow at 15 km depth compared to 22 km to the south. The loss of magnetism to the north is probably due to increased heat as a result of magmatic intrusion supporting active <span class="hlt">rifting</span> model. Conclusively, the integrated approach employed in this research confirms that fault <span class="hlt">system</span> delineated to the north is actively deforming under E-W normal extension and is a potential earthquake source probably related to magmatic intrusion, while the presence of fluids within the south fault zone reduce intensity of faulting activity and explains lack of earthquakes in a continental <span class="hlt">rift</span> setting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050176001','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050176001"><span>Parga Chasma: Coronae and <span class="hlt">Rifting</span> on Venus</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Smrekar, S. E.; Stofan, E. R.; Buck, W. R.; Martin, P.</p> <p>2005-01-01</p> <p>The majority of coronae (quasicircular volcano-tectonic features) are found along <span class="hlt">rifts</span> or fracture belts, and the majority of <span class="hlt">rifts</span> have coronae [e.g. 1,2]. However, the relationship between coronae and <span class="hlt">rifts</span> remains unclear [3-6]. There is evidence that coronae can form before, after, or synchronously with <span class="hlt">rifts</span> [3,4]. The extensional fractures in the <span class="hlt">rift</span> zones have been proposed to be a result of broad scale upwelling and traction on the lower lithosphere [7]. However, not all <span class="hlt">rift</span> <span class="hlt">systems</span> have a significant positive geoid anomaly, as would be expected for an upwelling site [8]. This could be explained if the <span class="hlt">rifts</span> lacking anomalies are no longer active. Coronae are generally accepted to be sites of local upwelling [e.g. 1], but the observed <span class="hlt">rifting</span> is frequently not radial to the coronae and extends well beyond the coronae into the surrounding plains. Thus the question remains as to whether the <span class="hlt">rifts</span> represent regional extension, perhaps driven by mantle tractions, or if the coronae themselves create local thinning and extension of the lithosphere. In the first case, a regional extension model should be consistent with the observed characteristics of the <span class="hlt">rifts</span>. In the latter case, a model of lithospheric loading and fracturing would be more appropriate. A good analogy may be the propagation of oceanic intraplate volcanoes [9].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2007/1047/kp/kp09/of2007-1047kp09.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2007/1047/kp/kp09/of2007-1047kp09.pdf"><span>Tectonics of the West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span>: new light on the history and dynamics of distributed intracontinental extension</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Siddoway, C.S.</p> <p>2007-01-01</p> <p>The West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span> (WARS) is the product of multiple stages of intracontinental deformation from Jurassic to Present. The Cretaceous <span class="hlt">rifting</span> phase accomplished >100 percent extension across the Ross Sea and central West Antarctica, and is widely perceived as a product of pure shear extension orthogonal to the Transantarctic Mountains that led to breakup and opening of the Southern Ocean between West Antarctica and New Zealand. New structural, petrological, and geochronological data from Marie Byrd Land reveal aspects of the kinematics, thermal history, and chronology of the Cretaceous intracontinental extension phase that cannot be readily explained by a single progressive event. Elevated temperatures in "Lachlan-type" crust caused extensive crustal melting and mid-crustal flow within a dextral transcurrent strain environment, leading to rapid extension and locally to exhumation and rapid cooling of a migmatite dome and detachment footwall structures. Peak metamorphism and onset of crustal flow that brought about WARS extension between 105 Ma and 90 Ma is kinematically, temporally, and spatially linked to the active convergent margin <span class="hlt">system</span> of East Gondwana. West Antarctica-New Zealand breakup is distinguished as a separate event at 83-70 Ma, from the standpoint of kinematics and thermal evolution</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T24B..06L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T24B..06L"><span>Stress Pattern of the Shanxi <span class="hlt">Rift</span> <span class="hlt">System</span>, North China, Inferred from the Inversion of New Focal Mechanisms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, B.; Atakan, K.; Sorensen, M. B.; Havskov, J.</p> <p>2014-12-01</p> <p>Earthquake focal mechanisms of the Shanxi <span class="hlt">rift</span> <span class="hlt">system</span>, North China, are investigated for the time period 1965 - Apr. 2014. A total of 143 focal mechanisms of ML ≥ 3.0 earthquakes were compiled. Among them, 105 solutions are newly determined by combining the P-wave first motions and full waveform inversion, and 38 solutions are from available published data. Stress tensor inversion was then performed based on the new database. The results show that most solutions exhibit normal or strike-slip faulting, and the regional stress field is characterized by a stable, dominating NNW-SSE extension and an ENE-WSW compression. This correlates well with results from GPS data, geological field observations and leveling measurements across the faults. Heterogeneity exists in the regional stress field, as indicated by individual stress tensor inversions conducted for five subzones. While the minimum stress axis (σ3) appears to be consistent and stable, the orientations, especially the plunges, of the maximum and intermediate stresses (σ1 and σ2) vary significantly among the different subzones. Based on our results and combining multidisciplinary observations from geological surveys, GPS and cross-fault monitoring, a kinematic model is proposed, to illustrate the present-day stress field and its correlation with the regional tectonics, as well as the current crustal deformation of the Shanxi <span class="hlt">rift</span> <span class="hlt">system</span>. Results obtained in this study, may help to understand the geodynamics, neotectonic activity, active seismicity and potential seismic hazard in this region of North China.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT........23R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT........23R"><span>Quantifying the Temporal and Spatial Response of Channel Steepness to Changes in <span class="hlt">Rift</span> Basin Architecture</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Robinson, Scott M.</p> <p></p> <p>Quantifying the temporal and spatial evolution of active continental <span class="hlt">rifts</span> contributes to our understanding of fault <span class="hlt">system</span> evolution and seismic hazards. <span class="hlt">Rift</span> <span class="hlt">systems</span> also preserve robust paleoenvironmental records and are often characterized by strong climatic gradients that can be used to examine feedbacks between climate and tectonics. In this thesis, I quantify the spatial and temporal history of <span class="hlt">rift</span> flank uplift by analyzing bedrock river channel profiles along footwall escarpments in the Malawi segment of the East Africa <span class="hlt">Rift</span>. This work addresses questions that are widely applicable to continental <span class="hlt">rift</span> settings: (1) Is <span class="hlt">rift</span>-flank uplift sufficiently described by theoretical elliptical along-fault displacement patterns? (2) Do orographic climate patterns induced by <span class="hlt">rift</span> topography affect <span class="hlt">rift</span>-flank uplift or morphology? (3) How do uplift patterns along <span class="hlt">rift</span> flanks vary over geologic timescales? In Malawi, 100-km-long border faults of alternating polarity bound half-graben sedimentary basins containing up to 4km of basin fill and water depths up to 700m. Orographically driven precipitation produces climatic gradients along footwall escarpments resulting in mean annual rainfall that varies spatially from 800 to 2500 mm. Temporal oscillations in climate have also resulted in lake lowstands 500 m below the modern shoreline. I examine bedrock river profiles crossing the Livingstone and Usisya Border Faults in northern Malawi using the channel steepness index (Ksn) to assess importance of these conditions on <span class="hlt">rift</span> flank evolution. River profiles reveal a consistent transient pattern that likely preserves a temporal record of slip and erosion along the entire border fault <span class="hlt">system</span>. These profiles and other topographic observations, along with known modern and paleoenvironmental conditions, can be used to interpret a complete history of <span class="hlt">rift</span> flank development from the onset of <span class="hlt">rifting</span> to present. I interpret the morphology of the upland landscape to preserve the onset</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70016810','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70016810"><span>Evidence of rapid Cenozoic uplift of the shoulder escarpment of the Cenozoic West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span> and a speculation on possible climate forcing</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Behrendt, John C.; Cooper, A.</p> <p>1991-01-01</p> <p>The Cenozoic West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span>, characterized by Cenozoic bimodal alkalic volcanic rocks, extends over a largely ice-covered area, from the Ross Sea nearly to the Bellingshausen Sea. Various lines of evidence lead to the following interpretation: the transantarctic Mountains part of the <span class="hlt">rift</span> shoulder (and probably the entire shoulder) has been rising since about 60 Ma, at episodic rates of ~1 km/m.y., most recently since mid-Pliocene Time, rather than continuously at the mean rate of 100 m/m.y. Uplift rates vary along the scarp, which is cut by transverse faults. It is speculated that this uplift may have climatically forced the advance of the Antarctic ice sheet since the most recent warm period. A possible synergistic relation is suggested between episodic tectonism, mountain uplift, and volcanism in the Cenozoic West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span> and waxing and waning of the Antarctic ice sheet beginning about earliest Oligocene time. -from Authors</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850066340&hterms=Continental+Drift&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DContinental%2BDrift','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850066340&hterms=Continental+Drift&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DContinental%2BDrift"><span>Is the Ventersdorp <span class="hlt">rift</span> <span class="hlt">system</span> of southern Africa related to a continental collision between the Kaapvaal and Zimbabwe Cratons at 2.64 Ga AGO?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Burke, K.; Kidd, W. S. F.; Kusky, T.</p> <p>1985-01-01</p> <p>Rocks of the Ventersdorp Supergroup were deposited in a <span class="hlt">system</span> of northeast trending grabens on the Kaapvaal Craton approximately 2.64 Ga ago contemporary with a continental collision between the Kaapvaal and Zimbabwe Cratons. It is suggested that it was this collision that initiated the Ventersdorp <span class="hlt">rifting</span>. Individual grabens strike at high angles toward the continental collision zone now exposed in the Limpopo Province where late orogenic left-lateral strike-slip faulting and anatectic granites are recognized. The Ventersdorp <span class="hlt">rift</span> province is related to extension in the Kaapvaal Craton associated with the collision, and some analogy is seen with such <span class="hlt">rifts</span> as the Shansi and Baikal <span class="hlt">Systems</span> associated with the current India-Asia continental collision.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015DokES.465.1191S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015DokES.465.1191S"><span>Modern fault formation in the Earth's crust of the Baikal <span class="hlt">rift</span> <span class="hlt">system</span> according to the data on the mechanisms of earthquake sources</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>San'kov, V. A.; Dobrynina, A. A.</p> <p>2015-11-01</p> <p>The spatial characteristics of seismotectonic deformations and the most likely fracture planes in the earthquake sources of the Baikal <span class="hlt">rift</span> <span class="hlt">system</span> (BRS) are determined using the method of cataclastic analysis of fractures [1]. It is shown that extension conditions with a strike of modern fractures parallel to the <span class="hlt">rift</span>-controlling faults are dominant in the central zone and in most of the NE flank of the BRS. The flat average dip of fractures in the earthquake sources of the main fault zones for some <span class="hlt">rift</span> depressions allow a suggestion about the flattening of faults in the middle crust. The antithetic faults are steeper. The BRS flanks are characterized by dominant shear deformations and more diverse morphogenetic faults in the earthquake sources (strike-slip faults, reversed faults, and normal faults). The modern faults at the BRS flanks weakly inherit the neotectonic structure.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70019000','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70019000"><span>Patterns of late Cenozoic volcanic and tectonic activity in the West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span> revealed by aeromagnetic surveys</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Behrendt, John C.; Saltus, R.; Damaske, D.; McCafferty, A.; Finn, C.A.; Blankenship, D.; Bell, R.E.</p> <p>1996-01-01</p> <p>Aeromagnetic surveys, spaced ???5 km, over widely separated areas of the largely ice- and sea-covered West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span>, reveal similar patterns of 100- to 1700-nT, shallow-source magnetic anomalies interpreted as evidence of extensive late Cenozoic volcanism. We use the aeromagnetic data to extend the volcanic <span class="hlt">rift</span> interpretation over West Antarctica starting with anomalies over (1) exposures of highly magnetic, late Cenozoic volcanic rocks several kilometers thick in the McMurdo-Ross Island area and elsewhere; continuing through (2) volcanoes and subvolcanic intrusions directly beneath the Ross Sea continental shelf defined by marine magnetic and seismic reflection data and aeromagnetic data and (3) volcanic structures interpreted beneath the Ross Ice Shelf partly controlled by seismic reflection determinations of seafloor depth to (4) an area of similar magnetic pattern over the West Antarctic Ice Sheet (400 km from the nearest exposed volcanic rock), where interpretations of late Cenozoic volcanic rocks at the base of the ice are controlled in part by radar ice sounding. North trending magnetic <span class="hlt">rift</span> fabric in the Ross Sea-Ross Ice Shelf and Corridor Aerogeophysics of the Southeast Ross Transect Zone (CASERTZ) areas, revealed by the aeromagnetic surveys, is probably a reactivation of older <span class="hlt">rift</span> trends (late Mesozoic?) and is superimposed on still older crosscutting structural trends revealed by magnetic terrace maps calculated from horizontal gradient of pseudogravity. Longwavelength (???100-km wide) magnetic terraces from sources within the subvolcanic basement cross the detailed survey areas. One of these extends across the Ross Sea survey from the front of the Transantarctic Mountains with an east-southeast trend crossing the north trending <span class="hlt">rift</span> fabric. The Ross Sea-Ross Ice Shelf survey area is characterized by highly magnetic northern and southern zones which are separated by magnetically defined faults from a more moderately magnetic central zone</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ESASP.740E.168L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ESASP.740E.168L"><span>Developing a Satellite Based Automatic <span class="hlt">System</span> for Crop Monitoring: Kenya's Great <span class="hlt">Rift</span> Valley, A Case Study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lucciani, Roberto; Laneve, Giovanni; Jahjah, Munzer; Mito, Collins</p> <p>2016-08-01</p> <p>The crop growth stage represents essential information for agricultural areas management. In this study we investigate the feasibility of a tool based on remotely sensed satellite (Landsat 8) imagery, capable of automatically classify crop fields and how much resolution enhancement based on pan-sharpening techniques and phenological information extraction, useful to create decision rules that allow to identify semantic class to assign to an object, can effectively support the classification process. Moreover we investigate the opportunity to extract vegetation health status information from remotely sensed assessment of the equivalent water thickness (EWT). Our case study is the Kenya's Great <span class="hlt">Rift</span> valley, in this area a ground truth campaign was conducted during August 2015 in order to collect crop fields GPS measurements, leaf area index (LAI) and chlorophyll samples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhDT........19T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhDT........19T"><span>Using remote sensing, ecological niche modeling, and Geographic Information <span class="hlt">Systems</span> for <span class="hlt">Rift</span> Valley fever risk assessment in the United States</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tedrow, Christine Atkins</p> <p></p> <p>The primary goal in this study was to explore remote sensing, ecological niche modeling, and Geographic Information <span class="hlt">Systems</span> (GIS) as aids in predicting candidate <span class="hlt">Rift</span> Valley fever (RVF) competent vector abundance and distribution in Virginia, and as means of estimating where risk of establishment in mosquitoes and risk of transmission to human populations would be greatest in Virginia. A second goal in this study was to determine whether the remotely-sensed Normalized Difference Vegetation Index (NDVI) can be used as a proxy variable of local conditions for the development of mosquitoes to predict mosquito species distribution and abundance in Virginia. As part of this study, a mosquito surveillance database was compiled to archive the historical patterns of mosquito species abundance in Virginia. In addition, linkages between mosquito density and local environmental and climatic patterns were spatially and temporally examined. The present study affirms the potential role of remote sensing imagery for species distribution prediction, and it demonstrates that ecological niche modeling is a valuable predictive tool to analyze the distributions of populations. The MaxEnt ecological niche modeling program was used to model predicted ranges for potential RVF competent vectors in Virginia. The MaxEnt model was shown to be robust, and the candidate RVF competent vector predicted distribution map is presented. The Normalized Difference Vegetation Index (NDVI) was found to be the most useful environmental-climatic variable to predict mosquito species distribution and abundance in Virginia. However, these results indicate that a more robust prediction is obtained by including other environmental-climatic factors correlated to mosquito densities (e.g., temperature, precipitation, elevation) with NDVI. The present study demonstrates that remote sensing and GIS can be used with ecological niche and risk modeling methods to estimate risk of virus establishment in mosquitoes and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JAESc.135..257Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JAESc.135..257Z"><span>Contemporary kinematics of the Ordos block, North China and its adjacent <span class="hlt">rift</span> <span class="hlt">systems</span> constrained by dense GPS observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Bin; Zhang, Caihong; Wang, Dongzhen; Huang, Yong; Tan, Kai; Du, Ruilin; Liu, Jingnan</p> <p>2017-03-01</p> <p>The detailed kinematic pattern of the Ordos block, North China and its surrounding <span class="hlt">rift</span> <span class="hlt">systems</span> remains uncertain, mainly due to the low signal-to-noise ratio of the Global Positioning <span class="hlt">System</span> (GPS) velocity data and the lack of GPS stations in this region. In this study, we have obtained a new and dense velocity field by processing GPS data primarily collected from the Crustal Motion Observation Network of China and from other GPS networks between 1998 and 2014. The GPS velocities within the Ordos block can be interpreted as counterclockwise rotation of the block about the Euler pole with respect to the Eurasia plate. Velocity profiles across the graben-bounding faults show relatively rapid right-lateral strike-slip motion along the Yinchuan graben, with a rate of 0.8-2.6 mm/a from north to south. In addition, a right-lateral slip rate of 1.1-1.6 mm/a is estimated along the central segment of the Shanxi <span class="hlt">rift</span>. However, strike-slip motion is not detected along the northern and southern margins of the Ordos block. Conversely, significant extension motion is detected across the northwestern corner of the block, with a value of 1.6 mm/a, and along the northern segment of the Shanxi <span class="hlt">rift</span>, where an extensional rate of 1.3-1.7 mm/a is measured. Both the Daihai and Datong basins are experiencing crustal extension. On the southwestern margin of the block, deformation across the compressional zone of the Liupanshan range is subtle; however, the far-field shorting rate is as high as 3.0 mm/a, implying that this region is experiencing ongoing compression. The results reveal that present-day fault slip occurs mainly along the block bounding faults, with the exception of faults along the northern and southern margins of the block. These results provide new insights into the nature of tectonic deformation around the Ordos block, and are useful for assessing the seismic activity in this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/888778','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/888778"><span>NONLINEAR DYNAMICAL <span class="hlt">SYSTEMS</span> - <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Philip Holmes</p> <p>2005-12-31</p> <p>This document is the <span class="hlt">final</span> report on the work completed on DE-FG02-95ER25238 since the start of the second renewal period: Jan 1, 2001. It supplements the annual reports submitted in 2001 and 2002. In the renewal proposal I envisaged work in three main areas: Analytical and topological tools for studying flows and maps Low dimensional models of fluid flow Models of animal locomotion and I describe the progess made on each project.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JAESc..99...13W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JAESc..99...13W"><span>The subsurface structure and stratigraphic architecture of <span class="hlt">rift</span>-related units in the Lishu Depression of the Songliao Basin, China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Hongyu; Fan, Tailiang; Wu, Yue</p> <p>2015-03-01</p> <p>This contribution reports the basin configuration feature, stratigraphy and sedimentary architecture of the Lishu Depression in the Songliao Basin, China. The activity rate, distribution and style of local faulting demonstrate the timing and extent of regional <span class="hlt">rifting</span>. Distinct episodes of compressional tectonic activity caused uplift and exposure of strata evident as the traditional syn- and post-<span class="hlt">rift</span> stages of basin evolution. These episodes led to the sequential denudation of the Upper Jurassic Huoshiling Formation, Lower Cretaceous Yingcheng and Denglouku Formations, and corresponding regional unconformities. Acting in tandem with regional compression, activity along the major boundary faults influenced the evolving basin configuration, as well as seismic sequences and sedimentary patterns. Seismic, well log and drill core data described here show subdivision sections of the Lishu Depression strata according to discrete phases of the traditional syn-<span class="hlt">rift</span> stage of deposition. We refer to these sub-stages as the initial <span class="hlt">rifting</span>, the intensive <span class="hlt">rifting</span> and the recession phases. The basin configuration shifted from a graben/half-graben configuration during the initial <span class="hlt">rifting</span> phase, to a dustpan-shaped half-graben pattern during the subsequent phase of intensive <span class="hlt">rifting</span>, and <span class="hlt">finally</span> into a gentle sedimentary basin during the <span class="hlt">final</span> recession phase. The early seismic sequence divides into a lowstand <span class="hlt">systems</span> tract (LST), transgressive <span class="hlt">systems</span> tract (TST) and highstand <span class="hlt">systems</span> tract (HST). Evidence of the LST within the seismic sequence becomes less apparent with the intensive <span class="hlt">rifting</span> phase, while the HST occupied an increasing proportion of the section. The shallow water depositional fill formed during the <span class="hlt">final</span> recession phase consists only of TST and HST components. Depositional environment then shifts from alluvial fan and shallow lacustrine <span class="hlt">systems</span> to fan delta, braided delta - lake, and <span class="hlt">finally</span> to a braided fluvial setting. The vertical stacking pattern shifts</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24589100','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24589100"><span>Analysis of surveillance <span class="hlt">systems</span> in place in European Mediterranean countries for West Nile virus (WNV) and <span class="hlt">Rift</span> Valley fever (RVF).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cito, F; Narcisi, V; Danzetta, M L; Iannetti, S; Sabatino, D D; Bruno, R; Carvelli, A; Atzeni, M; Sauro, F; Calistri, P</p> <p>2013-11-01</p> <p>West Nile virus (WNV) and <span class="hlt">Rift</span> Valley fever virus (RVFV) represent an important group of viral agents responsible for vector-borne zoonotic diseases constituting an emerging sanitary threat for the Mediterranean Basin and the neighbouring countries. WNV infection is present in several Mediterranean countries, whereas RVF has never been introduced into Europe, but it is considered a major threat for North African countries. Being vector-borne diseases, they cannot be prevented only through an animal trade control policy. Several approaches are used for the surveillance of WNV and RVFV. With the aim of assessing the surveillance <span class="hlt">systems</span> in place in Mediterranean countries, two disease-specific questionnaires (WNV, RVFV) have been prepared and submitted to Public Health and Veterinary Authorities of six EU countries. This study presents the information gathered through the questionnaires and describes some critical points in the prevention and surveillance of these diseases as emerged by the answers received.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoJI.203.1642L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoJI.203.1642L"><span>Coulomb stress evolution in the Shanxi <span class="hlt">rift</span> <span class="hlt">system</span>, North China, since 1303 associated with coseismic, post-seismic and interseismic deformation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Bin; Sørensen, Mathilde Bøttger; Atakan, Kuvvet</p> <p>2015-12-01</p> <p>The Shanxi <span class="hlt">rift</span> <span class="hlt">system</span> is one of the most active intraplate tectonic zones in the North China Block, resulting in devastating seismicity. Since 1303, the <span class="hlt">rift</span> has experienced fifteen Ms ≥ 6.5 earthquakes. Aiming at a better understanding of Coulomb stress evolution and its relationship with the seismicity in the <span class="hlt">rift</span> <span class="hlt">system</span>, we investigated the Coulomb stress changes due to coseismic slip and post-seismic relaxation processes following strong earthquakes as well as the interseismic tectonic loading since the 1303 Hongdong Ms = 8.0 earthquake. Our calculation applies a specified regional medium model, takes the gravity effect into account and uses the fault geometry of the next event as the receiver fault in a given calculation. Our results show that nine out of 12 Ms ≥ 6.5 earthquakes since the 1303 Hongdong earthquake and more than 82 per cent of small-medium instrumental events after the 1989 Datong-Yanggao Ms = 6.1 earthquake fall into the total stress increased areas. Our results also reveal the different roles of the coseismic, post-seismic and interseismic Coulomb stress changes in the earthquake triggering process in the Shanxi <span class="hlt">rift</span> <span class="hlt">system</span>. In a short period after a strong event, the stress field changes are dominated by coseismic Coulomb stress due to sudden slip of the ruptured fault, while in the long term, the stress field is mainly dominated by the accumulation of interseismic tectonic loading. Post-seismic stress changes play an important role by further modifying the distribution of stress and therefore cannot be ignored. Based on the current stress status in the Shanxi <span class="hlt">rift</span> <span class="hlt">system</span>, the Linfen basin, southern and northern Taiyuan basin, Xinding basin and the north part of the <span class="hlt">rift</span> <span class="hlt">system</span> are identified as the most likely locations of large events in the future. The results of this study can provide important clues for the further understanding of seismic hazard in the Shanxi <span class="hlt">rift</span> <span class="hlt">system</span> and thus help guiding earthquake risk mitigation efforts in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70032593','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70032593"><span>Mercury isotopic composition of hydrothermal <span class="hlt">systems</span> in the Yellowstone Plateau volcanic field and Guaymas Basin sea-floor <span class="hlt">rift</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Sherman, L.S.; Blum, J.D.; Nordstrom, D.K.; McCleskey, R.B.; Barkay, T.; Vetriani, C.</p> <p>2009-01-01</p> <p>To characterize mercury (Hg) isotopes and isotopic fractionation in hydrothermal <span class="hlt">systems</span> we analyzed fluid and precipitate samples from hot springs in the Yellowstone Plateau volcanic field and vent chimney samples from the Guaymas Basin sea-floor <span class="hlt">rift</span>. These samples provide an initial indication of the variability in Hg isotopic composition among marine and continental hydrothermal <span class="hlt">systems</span> that are controlled predominantly by mantle-derived magmas. Fluid samples from Ojo Caliente hot spring in Yellowstone range in δ202Hg from - 1.02‰ to 0.58‰ (± 0.11‰, 2SD) and solid precipitate samples from Guaymas Basin range in δ202Hg from - 0.37‰ to - 0.01‰ (± 0.14‰, 2SD). Fluid samples from Ojo Caliente display mass-dependent fractionation (MDF) of Hg from the vent (δ202Hg = 0.10‰ ± 0.11‰, 2SD) to the end of the outflow channel (&delta202Hg = 0.58‰ ± 0.11‰, 2SD) in conjunction with a decrease in Hg concentration from 46.6pg/g to 20.0pg/g. Although a small amount of Hg is lost from the fluids due to co-precipitation with siliceous sinter, we infer that the majority of the observed MDF and Hg loss from waters in Ojo Caliente is due to volatilization of Hg0(aq) to Hg0(g) and the preferential loss of Hg with a lower δ202Hg value to the atmosphere. A small amount of mass-independent fractionation (MIF) was observed in all samples from Ojo Caliente (Δ199Hg = 0.13‰ ±1 0.06‰, 2SD) but no significant MIF was measured in the sea-floor <span class="hlt">rift</span> samples from Guaymas Basin. This study demonstrates that several different hydrothermal processes fractionate Hg isotopes and that Hg isotopes may be used to better understand these processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Tecto..34.2367T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Tecto..34.2367T"><span>Cenozoic extension in the Kenya <span class="hlt">Rift</span> from low-temperature thermochronology: Links to diachronous spatiotemporal evolution of <span class="hlt">rifting</span> in East Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Torres Acosta, Verónica; Bande, Alejandro; Sobel, Edward R.; Parra, Mauricio; Schildgen, Taylor F.; Stuart, Finlay; Strecker, Manfred R.</p> <p>2015-12-01</p> <p>The cooling history of <span class="hlt">rift</span> shoulders and the subsidence history of <span class="hlt">rift</span> basins are cornerstones for reconstructing the morphotectonic evolution of extensional geodynamic provinces, assessing their role in paleoenvironmental changes and evaluating the resource potential of their basin fills. Our apatite fission track and zircon (U-Th)/He data from the Samburu Hills and the Elgeyo Escarpment in the northern and central sectors of the Kenya <span class="hlt">Rift</span> indicate a broadly consistent thermal evolution of both regions. Results of thermal modeling support a three-phased thermal history since the early Paleocene. The first phase (~65-50 Ma) was characterized by rapid cooling of the <span class="hlt">rift</span> shoulders and may be coeval with faulting and sedimentation in the Anza <span class="hlt">Rift</span> basin, now located in the subsurface of the Turkana depression and areas to the east in northern Kenya. In the second phase, very slow cooling or slight reheating occurred between ~45 and 15 Ma as a result of either stable surface conditions, very slow exhumation, or subsidence. The third phase comprised renewed rapid cooling starting at ~15 Ma. This <span class="hlt">final</span> cooling represents the most recent stage of <span class="hlt">rifting</span>, which followed widespread flood-phonolite emplacement and has shaped the present-day landscape through <span class="hlt">rift</span> shoulder uplift, faulting, basin filling, protracted volcanism, and erosion. When compared with thermochronologic and geologic data from other sectors of the East African <span class="hlt">Rift</span> <span class="hlt">System</span>, extension appears to be diachronous, spatially disparate, and partly overlapping, likely driven by interactions between mantle-driven processes and crustal heterogeneities, rather than the previously suggested north-south migrating influence of a mantle plume.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5580485','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5580485"><span>Experimental lithium <span class="hlt">system</span>. <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kolowith, R.; Berg, J.D.; Miller, W.C.</p> <p>1985-04-01</p> <p>A full-scale mockup of the Fusion Materials Irradiation Test (FMIT) Facility lithium <span class="hlt">system</span> was built at the Hanford Engineering Development Laboratory (HEDL). This isothermal mockup, called the Experimental Lithium <span class="hlt">System</span> (ELS), was prototypic of FMIT, excluding the accelerator and dump heat exchanger. This 3.8 m/sup 3/ lithium test loop achieved over 16,000 hours of safe and reliable operation. An extensive test program demonstrated satisfactory performance of the <span class="hlt">system</span> components, including the HEDL-supplied electromagnetic lithium pump, the lithium jet target, the purification and characterization hardware, as well as the auxiliary argon and vacuum <span class="hlt">systems</span>. Experience with the test loop provided important information on <span class="hlt">system</span> operation, performance, and reliability. This report presents a complete overview of the entire Experimental Lithium <span class="hlt">System</span> test program and also includes a summary of such areas as instrumentation, coolant chemistry, vapor/aerosol transport, and corrosion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED026849.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED026849.pdf"><span>Inventory <span class="hlt">Systems</span> Laboratory. <span class="hlt">Final</span> Report.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Naddor, Eliezer</p> <p></p> <p>Four computer programs to aid students in understanding inventory <span class="hlt">systems</span>, constructing mathematical inventory models, and developing optimal decision rules are presented. The program series allows a user to set input levels, simulates the behavior of major variables in inventory <span class="hlt">systems</span>, and provides performance measures as output. Inventory…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5426478','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5426478"><span>Laboratory test <span class="hlt">system</span>. <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Asher, G.L.</p> <p>1980-03-01</p> <p>This project was initiated to develop a laboratory test capability for evaluating new and existing digital product designs. In recent years, Bendix Kansas City has become more active in syppling early development hardware to the design laboratories for evaluation. Because of the more complex electronic designs being used in new components, more highly automated test <span class="hlt">systems</span> are needed to evaluate development hardware. To meet this requirement, a universal test <span class="hlt">system</span> was developed to provide both basic test capabilities and flexibility to adapt easily to specific product applications. This laboratory evaluation <span class="hlt">system</span> will reduce the need to develop complex dedicated test <span class="hlt">systems</span> for each new product design, while still providing the benefits of an automated <span class="hlt">system</span>. A special purpose interface chassis was designed and fabricated to permit a standardized interface between the test <span class="hlt">system</span> and the product application. Connector assignments by <span class="hlt">system</span> functions provide convenience and function isolation. Standard cables were used to reduce the need for special purpose hardware. Electrical testing of a developmental electronics assembly demonstrated the adaptability of this <span class="hlt">system</span> for a typical product application. Both the interface hardware and the software were developed for this application.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Tectp.630..300W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Tectp.630..300W"><span>Anomalous seafloor mounds in the northern Natal Valley, southwest Indian Ocean: Implications for the East African <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wiles, Errol; Green, Andrew; Watkeys, Mike; Jokat, Wilfried; Krocker, Ralph</p> <p>2014-09-01</p> <p>The Natal Valley (southwest Indian Ocean) has a complicated and protracted opening history, as has the surrounding southwest Indian Ocean. Recently collected multibeam swath bathymetry and 3.5 kHz seismic data from the Natal Valley reveal anomalous seafloor mounds in the northern Natal Valley. The significance, of these domes, as recorders of the geological history of the Natal Valley and SE African Margin has been overlooked with little attempt made to identify their origin, evolution or tectonic significance. This paper aims to describe these features from a morphological perspective and to use their occurrence as a means to better understand the geological and oceanographic evolution of this basin. The seafloor mounds are distinct in both shallow seismic and morphological character from the surrounding seafloor of the Natal Valley. Between 25 km and 31 km long, and 16 km and 18 km wide, these features rise some 400 m above the sedimentary deposits that have filled in the Natal Valley. Such macro-scale features have not previously been described from the Natal Valley or from other passive margins globally. They are not the result of bottom water circulation, salt tectonics; rather, igneous activity is favoured as the origin for these anomalous seafloor features. We propose a hypothesis that the anomalous seafloor mounds observed in the Natal Valley are related to igneous activity associated with the EARS. The complicated opening history and antecedent geology, coupled with the southward propagation of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> creates a unique setting where continental <span class="hlt">rift</span> associated features have been developed in a marine setting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5130219','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5130219"><span>Paleoseismologic studies of the Pajarito fault <span class="hlt">system</span>, western margin of the Rio Grande <span class="hlt">rift</span> near Los Alamos, NM</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kelson, K.I. ); Hemphill-Haley, M.A.; Wong, I.G. ); Gardner, J.N.; Reneau, S.L. )</p> <p>1993-04-01</p> <p>As in much of the Basin and Range province, low levels of historical seismicity in the Rio Grande <span class="hlt">rift</span> (RGR) are inconsistent with abundant geologic evidence for large-magnitude, late Pleistocene and Holocene earthquakes. Recent trenching and surficial mapping along the 40-km-long, north-trending Pajarito fault <span class="hlt">system</span> (PFS) near Los Alamos provide evidence for multiple surface-rupture events during the late Pleistocene and Holocene. Near Los Alamos, the Pajarito fault (PAF) exhibits an east-facing scarp up to 120 m high that has had at least four surface-rupture events in the past few hundred thousand years. Four trenches across the base of the highest, easternmost fault scarp show that the most-recent rupture occurred prior to about 9 ka, and possible prior to deposition of the 100- to 150-ka El Cajete Pumice. The long-term (post-1.1 Ma) slip rate on the PAF is about 0.1 mm/yr. The down-to-the-west Rendija Canyon (RCF) and Guaje Mountain (GMF) faults both have had at least two surface ruptures since the middle Pleistocene, including most-recent events at about 7.4 ka along the RCF and about 4 to 6 ka along the GMF. Slickensides and other indirect evidence suggest right-oblique normal slip on the RCF and GMF. Long-term (post-1.1 Ma) slip rates on these two faults are approximately an order of magnitude less than that on the PAF. Based on the observed spatial and temporal variations in activity, the subparallel PAF, RCF, and GMF apparently act as independent seismic sources, although they are located only about 1 to 3 km apart. Nevertheless, the average recurrence interval for faults within the PFS is probably comparable to intervals of 10[sup 4] yr estimated along the eastern <span class="hlt">rift</span> margin near Taos.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRB..119.8267H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRB..119.8267H"><span>Seismicity and subsidence following the 2011 Nabro eruption, Eritrea: Insights into the plumbing <span class="hlt">system</span> of an off-<span class="hlt">rift</span> volcano</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hamlyn, Joanna E.; Keir, Derek; Wright, Tim J.; Neuberg, Jürgen W.; Goitom, Berhe; Hammond, James O. S.; Pagli, Carolina; Oppenheimer, Clive; Kendall, J.-Michael; Grandin, Raphaël.</p> <p>2014-11-01</p> <p>Nabro volcano, situated to the east of the Afar <span class="hlt">Rift</span> Zone, erupted on 12 June 2011. Eruptions at such off-<span class="hlt">rift</span> volcanoes are infrequent, and consequently, the plumbing <span class="hlt">systems</span> are poorly understood. We present posteruption Synthetic Aperture Radar (SAR) images from the TerraSAR-X satellite and posteruption continuous seismic activity from a local seismic array. Interferometric analysis of SAR data, reveals a circular, 12 km wide, signal subsiding at ˜200 mm/yr. We inverted for the best fit Mogi source finding a 4 ± 1 × 107 m3/yr volume decrease at 7 ± 1 km depth. Between 31 August and 7 October 2011, we located 658 and relocated 456 earthquakes with local magnitudes between -0.4 and 4.5. Seismicity beneath the SE edge of Nabro at 11 km depth is likely associated with high strain rates from deep magma flow into the modeled reservoir. This suggests that magma is supplied through a narrow conduit and then stored at ˜7 km depth. We interpret seismicity at 4-6 km depth as brittle fracturing above the inferred magma reservoir. Focal mechanisms delineate a thrust fault striking NE-SW and dipping 45° to the SE across the caldera floor. We propose that the crustal response is to slip on this fault which crosscuts the caldera rather than to deform on ring faults. The NE-SW fault plane is not associated with measurable surface deformation, indicating that it does not contribute much to the caldera deformation. We show that subsidence of the caldera is controlled by magma chamber processes rather than fault slip.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002SedG..147...13O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002SedG..147...13O"><span>The 1.1-Ga Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span>, central North America: sedimentology of two deep boreholes, Lake Superior region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ojakangas, Richard W.; Dickas, Albert B.</p> <p>2002-03-01</p> <p>The Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span> (MRS) of central North America is a 1.1-Ga, 2500-km long structural feature that has been interpreted as a triple-junction <span class="hlt">rift</span> developed over a mantle plume. As much as 20 km of subaerial lava flows, mainly flood basalts, are overlain by as much as 10 km of sedimentary rocks that are mostly continental fluvial red beds. This rock sequence, known as the Keweenawan Supergroup, has been penetrated by a few deep boreholes in the search for petroleum. In this paper, two deep boreholes in the Upper Peninsula of Michigan are described in detail for the first time. Both the Amoco Production #1-29R test, herein referred to as the St. Amour well, and the nearby Hickey Creek well drilled by Cleveland Cliffs Mining Services, were 100% cored. The former is 7238 ft (2410 m) deep and the latter is 5345 ft (1780 m) deep. The entirety of the stratigraphic succession of the Hickey Creek core correlates very well with the upper portion of the St. Amour core, as determined by core description and point-counting of 43 thin sections selected out of 100 studied thin sections. Two Lower Paleozoic units and two Keweenawan red bed units—the Jacobsville Sandstone and the underlying Freda Sandstone—are described. The Jacobsville is largely a feldspatholithic sandstone and the Freda is largely a lithofeldspathic sandstone. Below the Freda, the remaining footage of the St. Amour core consists of a thick quartzose sandstone unit that overlies a heterogenous unit of intercalated red bed units of conglomerate, sandstone, siltstone, and shale; black shale; individual basalt flows; and a basal ignimbritic rhyolite. This lower portion of the St. Amour core presents an enigma, as it correlates very poorly with other key boreholes located to the west and southwest. While a black shale sequence is similar to the petroleum-bearing Nonesuch Formation farther west, there is no conglomerate unit to correlate with the Copper Harbor Conglomerate. Other key boreholes are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70015106','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70015106"><span>Mechanical response of the south flank of kilauea volcano, hawaii, to intrusive events along the <span class="hlt">rift</span> <span class="hlt">systems</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Dvorak, J.J.; Okamura, A.T.; English, T.T.; Koyanagi, R.Y.; Nakata, J.S.; Sako, M.K.; Tanigawa, W.T.; Yamashita, K.M.</p> <p>1986-01-01</p> <p>Increased earthquake activity and compression of the south flank of Kilauea volcano, Hawaii, have been recognized by previous investigators to accompany <span class="hlt">rift</span> intrusions. We further detail the temporal and spatial changes in earthquake rates and ground strain along the south flank induced by six major <span class="hlt">rift</span> intrusions which occurred between December 1971 and January 1981. The seismic response of the south flank to individual <span class="hlt">rift</span> intrusions is immediate; the increased rate of earthquake activity lasts from 1 to 4 weeks. Horizontal strain measurements indicate that compression of the south flank usually accompanies <span class="hlt">rift</span> intrusions and eruptions. Emplacement of an intrusion at a depth greater than about 4 km, such as the June 1982 southwest <span class="hlt">rift</span> intrusion, however, results in a slight extension of the subaerial portion of the south flank. Horizontal strain measurements along the south flank are used to locate the January 1983 east-<span class="hlt">rift</span> intrusion, which resulted in eruptive activity. The intrusion is modeled as a vertical rectangular sheet with constant displacement perpendicular to the plane of the sheet. This model suggests that the intrusive body that compressed the south flank in January 1983 extended from the surface to about 2.4 km depth, and was aligned along a strike of N66??E. The intrusion is approximately 11 km in length, extended beyond the January 1983 eruptive fissures, which are 8 km in length and is contained within the 14-km-long region of shallow <span class="hlt">rift</span> earthquakes. ?? 1986.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MarGR..36..263K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MarGR..36..263K"><span><span class="hlt">Rift</span> processes and crustal structure of the Amundsen Sea Embayment, West Antarctica, from 3D potential field modelling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kalberg, Thomas; Gohl, Karsten; Eagles, Graeme; Spiegel, Cornelia</p> <p>2015-12-01</p> <p>The Amundsen Sea Embayment of West Antarctica is of particular interest as it provides critical geological boundary conditions in better understanding the dynamic behavior of the West Antarctic Ice Sheet, which is undergoing rapid ice loss in the Amundsen Sea sector. One of the highly debated hypothesis is whether this region has been affected by the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span>, which is one of the largest in the world and the dominating tectonic feature in West Antarctica. Previous geophysical studies suggested an eastward continuation of this <span class="hlt">rift</span> <span class="hlt">system</span> into the Amundsen Sea Embayment. This geophysical study of the Amundsen Sea Embayment presents a compilation of data collected during two RV Polarstern expeditions in the Amundsen Sea Embayment of West Antarctica in 2006 and 2010. Bathymetry and satellite-derived gravity data of the Amundsen Sea Embayment complete the dataset. Our 3-D gravity and magnetic models of the lithospheric architecture and development of this Pacific margin improve previous interpretations from 2-D models of the region. The crust-mantle boundary beneath the continental rise and shelf is between 14 and 29 km deep. The imaged basement structure can be related to <span class="hlt">rift</span> basins within the Amundsen Sea Embayment, some of which can be interpreted as products of the Cretaceous <span class="hlt">rift</span> and break-up phase and some as products of later propagation of the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> into the region. An estimate of the flexural rigidity of the lithosphere reveals a thin elastic thickness in the eastern embayment which increases towards the west. The results are comparable to estimates in other <span class="hlt">rift</span> <span class="hlt">systems</span> such as the Basin and Range province or the East African <span class="hlt">Rift</span>. Based on these results, we infer an arm of the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> is superposed on a distributed Cretaceous <span class="hlt">rift</span> province in the Amundsen Sea Embayment. <span class="hlt">Finally</span>, the embayment was affected by magmatism from discrete sources along the Pacific margin of West Antarctica in the Cenozoic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=241528&keyword=radium&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=78772845&CFTOKEN=60519519','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=241528&keyword=radium&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=78772845&CFTOKEN=60519519"><span><span class="hlt">Final</span> Barrier: Small <span class="hlt">System</span> Compliance</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>This presentation will discuss the use of point-of-use (POU) technology for small drinking water <span class="hlt">systems</span>. Information will be provided on the USEPA regulations that allow the use of POU for compliance and the technologies that are listed as SSCT for radium and arsenic. Listing o...</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5657215','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5657215"><span>Evidence of rapid Cenozoic uplift of the shoulder escarpment of the Cenozoic West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span> and a speculation on possible climate forcing</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Behrendt, J.C. ); Cooper, A. )</p> <p>1991-04-01</p> <p>The Cenzoic West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span>, characterized by Cenozoic bimodal alkalic volcanic rocks, extends over a largely ice-covered area, from the Ross Sea nearly to the Bellingshausen Sea. It is bounded on one side by a spectacular 4-to 5-km-high <span class="hlt">rift</span>-shoulder scarp (maximum bedrock relief 5 to 7 km) from northern Victoria Land-Queen Maud Mountains to the Ellsworth-Whitmore-Horlick Mountains. Jurassic tholeiites crop out with the late Cenozoic volcanic rocks along the section of the Transantarctic Mountains from northern Victoria Land to the Horlick Mountains. The Cenozoic <span class="hlt">rift</span> shoulder diverges here from the Jurassic tholeiite trend, and the tholeiites are exposed discontinuously along the lower elevation (1-2 km) section of the Transantarctic Mountains to the Weddell Sea. Various lines of evidence, no one of which is independently conclusive, lead the authors (as others have also suggested) to interpret the following. The Transantarctic Mountains part of the <span class="hlt">rift</span> shoulder (and probably the entire shoulder) has been rising since about 60 Ma, at episodic rates of {approximately}1 km/m.y., most recently since mid-Pliocene time, rather than continuously at the mean rate of 100m/m.y. Uplift rates vary along the scarp, which is cut by transverse faults. The authors speculate that this uplift may have climatically forced the advance of the Antarctic ice sheet since the most recent warm period. They suggest a possible synergistic relation between episodic tectonism, mountain uplift, and volcanism in the Cenozoic West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span> and waxing and waning of the Antarctic ice sheet beginning about earliest Oligocene time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JAfES..48..125K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JAfES..48..125K"><span>Early structural development of the Okavango <span class="hlt">rift</span> zone, NW Botswana</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kinabo, B. D.; Atekwana, E. A.; Hogan, J. P.; Modisi, M. P.; Wheaton, D. D.; Kampunzu, A. B.</p> <p>2007-06-01</p> <p>Aeromagnetic and gravity data collected across the Okavango <span class="hlt">rift</span> zone, northwest Botswana are used to map the distribution of faults, provide insights into the two-dimensional shallow subsurface geometry of the <span class="hlt">rift</span>, and evaluate models for basin formation as well as the role of pre-existing basement fabric on the development of this nascent continental <span class="hlt">rift</span>. The structural fabric (fold axes and foliation) of the Proterozoic basement terrane is clearly imaged on both gravity and magnetic maps. The strike of <span class="hlt">rift</span>-related faults (030-050° in the north and 060-070° in the south) parallels fold axes and the prominent foliation directions of the basement rocks. These pre-existing fabrics and structures represent a significant strength anisotropy that controlled the orientation of younger brittle faults within the stress regime present during initiation of this <span class="hlt">rift</span>. Northwest dipping faults consistently exhibit greater displacements than southeast dipping faults, suggesting a developing half-graben geometry for this <span class="hlt">rift</span> zone. However, the absence of fully developed half-grabens along this <span class="hlt">rift</span> zone suggests that the border fault <span class="hlt">system</span> is not fully developed consistent with the infancy of <span class="hlt">rifting</span>. Three en-echelon northeast trending depocenters coincide with structural grabens that define the Okavango <span class="hlt">rift</span> zone. Along the southeastern boundary of the <span class="hlt">rift</span>, developing border faults define a 50 km wide zone of subsidence within a larger 150 km wide zone of extension forming a <span class="hlt">rift-in-rift</span> structure. We infer from this observation that the localization of strain resulting from extension is occurring mostly along the southeastern boundary where the border fault <span class="hlt">system</span> is being initiated, underscoring the important role of border faults in accommodating strain even during this early stage of <span class="hlt">rift</span> development. We conclude that incipient <span class="hlt">rift</span> zones may provide critical insights into the development of <span class="hlt">rift</span> basins during the earliest stages of continental <span class="hlt">rifting</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4003290','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4003290"><span>Evidence of <span class="hlt">rift</span> valley fever seroprevalence in the Sahrawi semi-nomadic pastoralist <span class="hlt">system</span>, Western Sahara</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2014-01-01</p> <p>Background The increasing global importance of <span class="hlt">Rift</span> Valley fever (RVF) is clearly demonstrated by its geographical expansion. The presence of a wide range of host and vector species, and the epidemiological characteristics of RVF, have led to concerns that epidemics will continue to occur in previously unaffected regions of Africa. The proximity of the Sahrawi territories of Western Sahara to endemic countries, such as Mauritania, Senegal, and Mali with periodic isolation of virus and serological evidence of RVF, and the intensive livestock trade in the region results in a serious risk of RVF spread in the Sahrawi territories, and potentially from there to the Maghreb and beyond. A sero-epidemiological survey was conducted in the Saharawi territories between March and April 2008 to investigate the possible presence of the RVF virus (RVFV) and associated risk factors. A two-stage cluster sampling design was used, incorporating 23 sampling sites. Results A total of 982 serum samples was collected from 461 sheep, 463 goats and 58 camels. Eleven samples (0.97%) tested positive for IgG against the RVFV. There were clusters of high seroprevalence located mostly in the Tifariti (7.69%) and Mehaires (7.14%) regions, with the Tifariti event having been found in one single flock (4/26 positive animals). Goats and older animals were at a significantly increased risk being seropositive (p = 0.007 and p = 0.007, respectively). Conclusion The results suggest potential RVF activity in the study area, where intense livestock movement and trade with neighbouring countries might be considered as a primary determinant in the spread of the disease. The importance of a continuous field investigation is reinforced, in light of the risk of RVF expansion to historically unaffected regions of Africa. PMID:24758592</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T13C4665S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T13C4665S"><span>Earthquake Rupture Forecast of M>= 6 for the Corinth <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scotti, O.; Boiselet, A.; Lyon-Caen, H.; Albini, P.; Bernard, P.; Briole, P.; Ford, M.; Lambotte, S.; Matrullo, E.; Rovida, A.; Satriano, C.</p> <p>2014-12-01</p> <p>Fourteen years of multidisciplinary observations and data collection in the Western Corinth <span class="hlt">Rift</span> (WCR) near-fault observatory have been recently synthesized (Boiselet, Ph.D. 2014) for the purpose of providing earthquake rupture forecasts (ERF) of M>=6 in WCR. The main contribution of this work consisted in paving the road towards the development of a "community-based" fault model reflecting the level of knowledge gathered thus far by the WCR working group. The most relevant available data used for this exercise are: - onshore/offshore fault traces, based on geological and high-resolution seismics, revealing a complex network of E-W striking, ~10 km long fault segments; microseismicity recorded by a dense network ( > 60000 events; 1.5<Mw<4.5), delineating steep and low-angle (blind) active fault geometries between 4 and ~10 km depth; GPS velocity vectors, indicating that most of the N-S extension rate (16 mm/y) is limited to the width of the WCR; recent historical seismicity investigations, that have led to important reassessments of magnitudes and locations of M>=5 19th century events and a few paleoseismological investigations, allowing to consider time-dependent ERF. B-value estimates are found to be catalogue-dependent (WCR, homogenized NOA+Thessaloniki, SHARE), which may call for a potential break in scaling relationship. Furthermore, observed discrepancies between seismicity rates assumed for the modeled faults and those expected from GPS deformation rates call for the presence of aseismic deformation. Uncertainty in the ERF resulting from the lack of precise knowledge concerning both, fault geometries and seismic slip rates, is quantified through a logic tree exploration. Median and precentile predictions are then compared to ERF assuming a uniform seismicity rate in the WCR region. The issues raised by this work will be discussed in the light of seismic hazard assessment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Tecto..35.2863S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Tecto..35.2863S"><span>Thermochronometric evidence for diffuse extension and two-phase <span class="hlt">rifting</span> within the Central Arabian Margin of the Red Sea <span class="hlt">Rift</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Szymanski, E.; Stockli, D. F.; Johnson, P. R.; Hager, C.</p> <p>2016-12-01</p> <p>Numerical time-temperature models derived from a 2-D network of apatite and zircon (U-Th)/He ages reveal a three-stage thermotectonic history for the central Arabian <span class="hlt">rift</span> flank (CARF) of the Red Sea <span class="hlt">Rift</span> (RSR) <span class="hlt">system</span>. The pre-<span class="hlt">rift</span> Arabian-Nubian Shield existed as part of a passive Paleo-Tethyan margin until a widespread tectonic event at 350 Ma exhumed the proto-CARF to mid-to-upper crustal structural levels. After remaining thermally stable through the Mesozoic, the first phase of RSR extension began with a distinct <span class="hlt">rift</span> pulse at 23 Ma when fault blocks across a 150 km wide area were exhumed along a diffuse set of <span class="hlt">rift</span>-parallel faults from an average pre-<span class="hlt">rift</span> flank depth of 1.7 ± 0.8 km. This <span class="hlt">rift</span> onset age is mirrored in thermochronometric and sequence stratigraphic analyses elsewhere along the Red Sea Nubian and Arabian margins, confirming that <span class="hlt">rifting</span> occurred concomitantly along the full Red Sea-Gulf of Suez <span class="hlt">rift</span> <span class="hlt">system</span>. Diffuse lithospheric extension lasted for 8 Myr before a second <span class="hlt">rift</span> pulse at 15 Ma, coincident with regional stress realignment, transferred active faulting basinward toward the modern RSR axial trough. CARF time-temperature models indicate that the prevalent <span class="hlt">rift</span> style during both RSR extensional phases was one of localized, structurally controlled block faulting and contemporaneous dike injection, not wholesale <span class="hlt">rift</span> flank uplift.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6500532','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6500532"><span>Lunar power <span class="hlt">systems</span>. <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1986-12-01</p> <p>The findings of a study on the feasibility of several methods of providing electrical power for a permanently manned lunar base are provided. Two fundamentally different methods for lunar electrical power generation are considered. One is the use of a small nuclear reactor and the other is the conversion of solar energy to electricity. The baseline goal was to initially provide 300 kW of power with growth capability to one megawatt and eventually to 10 megawatts. A detailed, day by day scenario for the establishment, build-up, and operational activity of the lunar base is presented. Also presented is a conceptual approach to a supporting transportation <span class="hlt">system</span> which identifies the number, type, and deployment of transportation vehicles required to support the base. An approach to the use of solar cells in the lunar environment was developed. There are a number of heat engines which are applicable to solar/electric conversions, and these are examined. Several approaches to energy storage which were used by the electric power utilities were examined and those which could be used at a lunar base were identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.2542G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.2542G"><span>Application of P- and S-receiver functions to investigate crustal and upper mantle structures beneath the Albertine branch of the East African <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gummert, Michael; Lindenfeld, Michael; Wölbern, Ingo; Rümpker, Georg; Kasereka, Celestin; Batte, Arthur</p> <p>2014-05-01</p> <p>The Rwenzori region at the border between Uganda and the Democratic Republic of Congo is part of the western (Albertine) branch of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS). The region is characterized by a horst structure, the Rwenzori Mountains, reaching elevations of more than 5 km and covering an area of about 120 km by 50 km. The unusual location of the mountain range, between two segments of the Albertine <span class="hlt">rift</span>, suggests complex structures of the crust and the upper mantle below. In our study, we employ P- and S-receiver functions in order to investigate the corresponding discontinuities of the lithosphere-asthenosphere <span class="hlt">system</span>. The analyses are based on recordings from a dense network of 33 seismic broadband stations operating in the region for a period of nearly two years, from September 2009 until August 2011. The crustal thickness is analysed by using P-receiver functions and the grid search method of Zhu & Kanamori (2000) which involves the stacking of amplitudes of direct converted (Ps) and multiple phases (PpPs and PpSs) originating from the Moho. The method of S-receiver functions is more effective in analysing deeper discontinuities of the upper mantle, such as the lithosphere-asthenosphere boundary (LAB). The latter method also has the advantage that the interfering influence of multiple phases from shallower discontinuities is avoided. To simplify the analysis of the S-receiver functions, we use an automatic procedure to determine incidence angles used in the rotation from the ZNE <span class="hlt">system</span> to the ray-centered LQT <span class="hlt">system</span>. We apply this approach to confirm and significantly extend results from the study of Wölbern et al. (2012), which provided evidence for an intra-lithospheric discontinuity at depths between 54 km and 104 km and the LAB between 135 km and 210 km. Our results provide evidence for significant variations of crustal thickness beneath the region. The Moho depth varies between 20 km beneath the <span class="hlt">rift</span> valley and 39 km beneath the adjacent <span class="hlt">rift</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5732012','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5732012"><span><span class="hlt">Final</span> focus <span class="hlt">systems</span> for linear colliders</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Erickson, R.A.</p> <p>1987-11-01</p> <p>The <span class="hlt">final</span> focus <span class="hlt">system</span> of a linear collider must perform two primary functions, it must focus the two opposing beams so that their transverse dimensions at the interaction point are small enough to yield acceptable luminosity, and it must steer the beams together to maintain collisions. In addition, the <span class="hlt">final</span> focus <span class="hlt">system</span> must transport the outgoing beams to a location where they can be recycled or safely dumped. Elementary optical considerations for linear collider <span class="hlt">final</span> focus <span class="hlt">systems</span> are discussed, followed by chromatic aberrations. The design of the <span class="hlt">final</span> focus <span class="hlt">system</span> of the SLAC Linear Collider (SLC) is described. Tuning and diagnostics and steering to collision are discussed. Most of the examples illustrating the concepts covered are drawn from the SLC, but the principles and conclusions are said to be generally applicable to other linear collider designs as well. 26 refs., 17 figs. (LEW)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1713633R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1713633R"><span>Receiver function imaging of the lithosphere-asthenosphere boundary and melt beneath the Afar <span class="hlt">Rift</span> in comparison to other <span class="hlt">systems</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rychert, Catherine A.; Harmon, Nicholas</p> <p>2015-04-01</p> <p>Heating, melting, and stretching destroy continents at volcanic <span class="hlt">rifts</span>. Mantle plumes are often invoked to thermally weaken the continental lithosphere and accommodate <span class="hlt">rifting</span> through the influx of magma. However the relative effects of mechanical stretching vs. melt infiltration and weakening are not well quantified during the evolution of <span class="hlt">rifting</span>. S-to-p (Sp) imaging beneath the Afar <span class="hlt">Rift</span> provides additional constraints. We use two methodologies to investigate structure and locate robust features: 1) binning by conversion point and then simultaneous deconvolution in the frequency domain, and 2) extended multitaper followed by migration and stacking. We image a lithosphere-asthenosphere boundary at ~75 km beneath the flank of the Afar <span class="hlt">Rift</span> vs. its complete absence beneath the <span class="hlt">rift</span>. Instead, a strong velocity increase with depth at ~75 km depth is imaged. Beneath the <span class="hlt">rift</span> axis waveform modeling suggests the lack of a mantle lithosphere with a velocity increase at ~75 km depth. Geodynamic models that include high melt retention and suppress thermal convection easily match the required velocity-depth profile, the velocity increase arising from a drop in melt percentage at the onset of decompression melting. Whereas, models with conservative melt retention that include thermal buoyancy effects cannot reproduce the strong velocity increase. The shallow depth of the onset of melting is consistent with a mantle potential temperature = 1350 - 1400°C, i.e., typical for adiabatic decompression melting. Trace element signatures and geochemical modeling have been used to argue for a thick lithosphere beneath the <span class="hlt">rift</span> and slightly higher mantle potential temperatures ~1450°C, although overall, given modeling assumptions, the results are not in disagreement. Therefore, although a plume initially destroyed the mantle lithosphere, its influence directly beneath Afar today is not strong. Volcanism continues via adiabatic decompression melting assisted by strong melt buoyancy</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930069932&hterms=ruppel&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Druppel','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930069932&hterms=ruppel&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Druppel"><span>Implications of new gravity data for Baikal <span class="hlt">Rift</span> zone structure</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ruppel, C.; Kogan, M. G.; Mcnutt, M. K.</p> <p>1993-01-01</p> <p>Newly available, 2D Bouguer gravity anomaly data from the Baikal <span class="hlt">Rift</span> zone, Siberia, indicate that this discrete, intracontinental <span class="hlt">rift</span> <span class="hlt">system</span> is regionally compensated by an elastic plate about 50 km thick. However, spectral and spatial domain analyses and isostatic anomaly calculations show that simple elastic plate theory does not offer an adequate explanation for compensation in the <span class="hlt">rift</span> zone, probably because of significant lateral variations in plate strength and the presence of subsurface loads. Our results and other geophysical observations support the interpretation that the Baikal <span class="hlt">Rift</span> zone is colder than either the East African or Rio Grande <span class="hlt">rift</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T43F2745S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T43F2745S"><span>Minimal Role of Basal Shear Tractions in Driving Nubia-Somalia Divergence Across the East African <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stamps, D. S.; Calais, E.; Iaffaldano, G.; Flesch, L. M.</p> <p>2012-12-01</p> <p>The Nubian and Somalian plates actively diverge along the topographically high, ~5000 km long East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS). As no major subduction zones bound Africa, one can assume that the forces driving the Nubia-Somalia plate <span class="hlt">system</span> result primarily from mantle buoyancies and lateral variation in lithospheric gravitational potential energy. Images from seismic tomography and convection models suggest active mantle flow beneath Africa. However, the contribution from large-scale convection to the force balance driving plate divergence across the EARS remains in question. In this work we investigate the impact of mantle shear tractions on the dynamics of Nubia-Somalia divergence across the EARS. We compare surface motions inferred from GPS observations with strain rates and velocities predicted from dynamic models where basal shear stresses are (1) derived from forward mantle circulation models and (2) inferred from stress field boundary conditions that balance buoyancy forces in the African lithosphere. Upper mantle anisotropy derived from seismic observations beneath Africa provide independent constraints for the latter. Preliminary results suggest that basal shear tractions play a minor role in the dynamics of Nubia-Somalia divergence along the EARS. This result implies mantle-lithosphere decoupling, possibly promoted by a low viscosity asthenosphere. We corroborate the robustness of our results with estimates of upper mantle viscosity based on local upper mantle temperature estimates and rheological parameters obtained from laboratory experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T11C2906Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T11C2906Z"><span>Crustal Structure in the area of the North American Mid-Continent <span class="hlt">Rift</span> <span class="hlt">System</span> from P-wave Receiver Functions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, H.; van der Lee, S.; Wolin, E.; Bollmann, T. A.; Revenaugh, J.; Wiens, D. A.; Wysession, M. E.; Aleqabi, G. I.; Frederiksen, A. W.; Darbyshire, F. A.; Stein, S. A.; Jurdy, D. M.</p> <p>2015-12-01</p> <p>The Mid-continent Geophysical Anomaly (MGA) represents the largest gravity anomaly in the North American continental interior, its strongest portion stretching from Iowa to Lake Superior, and is the direct result of 1.1 Ga deposition and uplift of volcanic rocks in the Mid-continent <span class="hlt">Rift</span> <span class="hlt">System</span> (MRS). The Superior Province <span class="hlt">Rifting</span> Earthscope Experiment (SPREE) collected broadband seismic data around this prominent portion of the MGA for 2.5 years from 82 seismic stations, simultaneously with about 30 Transportable Array (TA) stations in the region. To image crustal structure around the MGA, we analyzed the P-wave trains of 119 teleseismic earthquakes at these stations using the time-domain iterative-deconvolution method of Ligorria and Ammon (1999), the waveform-fitting method of Van der Meijde et al. (2003), and the H-κ stacking method of Zhu and
Kanamori (2000). Our aim was to resolve intra-crustal layering and Moho characteristics. Despite considerable noise related to station installation constraints, we find that outside of the MGA, the Moho is sharp and relatively flat, both beneath the Archean Superior Province as well as beneath the Proterozoic terranes to its south. This Moho produces consistent P to S converted phases in the analyzed receiver functions. Receiver functions show much more complexity along the MGA, where P to S converted phases from the Moho are much weaker and more variable with azimuth and epicentral distance. Similar results have been found in Iowa by French et al. (2009). For many stations along the MGA, multiple weak S phases arrive around the time expected for the Moho-converted phase. In addition, strong P-to-S converted phases are observed from the base of shallow sedimentary layers. The base of the sedimentary layer is fairly shallow outside of the MGA, thickens near the flanks where gravity anomalies are low and shallows again in the center where the gravity peaks. We conclude that the Moho is not a strong feature of the MRS</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.T13F..08W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.T13F..08W"><span>The case for nearly continuous extension of the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span>, 105-25 Ma (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilson, D. S.; Luyendyk, B. P.</p> <p>2010-12-01</p> <p>It is a common perception that extension in the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> (WARS) was a two-phase process, with a Cretaceous phase ending when the Campbell Plateau <span class="hlt">rifted</span> from West Antarctica (~80 Ma), and a mid-Cenozoic phase synchronous with sea floor spreading in the Adare trough (~45-25 Ma). Several lines of evidence indicate that significant extension probably occurred in the intervening 80-45 Ma interval. The strongest evidence comes from subsidence rates on the Central High and Coulman High structures in the central-western Ross Sea, where DSDP Site 270 and other areas with shallow basement have subsided 1 km or more since Oligocene time. With sediment load, these subsidence rates are reasonable for thermal subsidence resulting from extension with a stretching factor of about 2.0-2.5 at about 50-70 Ma, but are hard to reconcile with an extension age around 90 Ma. The seismic velocity structure of the WARS inferred from global surface-wave dispersion is similar to that of oceanic lithosphere of age 40-60 Ma [Ritzwoller et al., 2001 JGR]. Geometric relations of sea floor between Adare Trough and Iselen Bank, northwest Ross Sea, suggest sea floor spreading of about 130 km during early Cenozoic, before the Adare Trough spreading episode started. Numerous cooling ages in the Transantarctic Mountains in the range of 55-45 Ma [Fitzgerald, 1992 Tectonics; Miller et al., 2010 Tectonics] support the interpretation of significant extension prior to 45 Ma. Present crustal thickness of about 22 km near DSDP Site 270 [Trey et al., 1999 Tectonophysics] suggests a pre-extension crustal thickness exceeding 50 km. A simple overall interpretation follows that the WARS has a tectonic history similar to the Basin and Range of western North America: a thick-crust orogenic highland extended for many tens of million years. The main difference between the WARS and the Basin and Range is the post-tectonic cooling and subsidence in the WARS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5237275','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5237275"><span>Off-axis volcanism in the Gregory <span class="hlt">rift</span>, east Africa: implications for models of continental <span class="hlt">rifting</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bosworth, W.</p> <p>1987-05-01</p> <p>The largest volcanic centers of the Gregory <span class="hlt">rift</span> occur in two belts located 100 to 150 km east and west of the axis of the <span class="hlt">rift</span> valley. These off-axis volcanic belts include the highest peaks on the continent of Africa and are interpreted to lie above the intersection of low-angle detachment <span class="hlt">systems</span> with the base of a regionally thinned lithosphere. These detachment <span class="hlt">systems</span> are manifested at the surface as a series of breakaway zones and regional bounding faults that produce subbasins with half-graben form. The asymmetry of subbasins alternates along the <span class="hlt">rift</span> axis, indicating that the polarity of the underlying active detachment <span class="hlt">systems</span> also reverses. The detachments are separated laterally by regional oblique-slip accommodation zones typified by wrench-style tectonism. Off-axis from the <span class="hlt">rift</span>, the detachments are inferred to merge along strike as they cut to the base of the lithosphere. This results in irregular but persistent paired zones of volcanism and lithospheric thinning off-axis from the <span class="hlt">rift</span> proper. The development of major volcanic cones such as Mount Kilimanjaro may be controlled by the interaction of leaky accommodation zones with the regions of structurally thinned lithosphere. The central Kenya hot spot has produced the anomalous quantities of volcanic material that fills the Gregory <span class="hlt">rift</span> and probably enhances the off-axis volcanism but does not directly control its location. The model proposed here for tectonic controls of volcanism in the Gregory <span class="hlt">rift</span> may be applicable to Phanerozoic continental <span class="hlt">rifts</span> in general.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.T31D0486B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.T31D0486B"><span>Thermochronological investigation of the timing of <span class="hlt">rifting</span> and <span class="hlt">rift</span> segmentation in the Gulf of Suez, Egypt</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bosworth, W.; Stockli, D. F.</p> <p>2006-12-01</p> <p>The Tertiary Gulf of Suez <span class="hlt">rift</span> <span class="hlt">system</span> is one of the best-studied continental <span class="hlt">rift</span> <span class="hlt">systems</span> and has inspired many fundamental geodynamic models for continental <span class="hlt">rifting</span>. However, our limited knowledge of how extensional strain is spatially and temporally distributed has made it difficult to adequately evaluate models for the dynamic evolution of this <span class="hlt">rift</span>. A critical aspect of constraining the evolution of <span class="hlt">rifting</span> and <span class="hlt">rift</span> segmentation in the Gulf of Suez involves acquiring reliable geochronological constraints on extensional faulting. This study has commenced a systematic investigation of the timing and spatial distribution of <span class="hlt">rifting</span>, lateral <span class="hlt">rift</span> segmentation, and <span class="hlt">rift</span> localization within the Gulf of Suez, Egypt, employing apatite and zircon (U-Th)/He thermochronometry. (U-Th)/He thermochronometric analysis of sample transects from exhumed fault blocks within the <span class="hlt">rift</span> integrated with structural data will allow us to directly determine the timing, distribution, and magnitude of extension. The onset of major <span class="hlt">rifting</span> (~24-19 Ma) in the Gulf of Suez was marked by the development of crustal domino-style tilt blocks and syn-<span class="hlt">rift</span> deposition of the late Oligocene non-marine Abu Zenima Fm and non-marine to restricted marine Nukhul Fm. Development of the Gulf of Aqaba-Dead Sea transform cut off the <span class="hlt">rift</span> from the Red Sea <span class="hlt">rift</span> at an early extensional stage. Apatite (AHe) and zircon (ZHe) (U- Th)/He data were collected from basement and pre-<span class="hlt">rift</span> sedimentary sample transects from the central and southern Sinai Peninsula portion and the Gebel El Zeit area in the southern Gulf of Suez as well as from basement samples from selected drill cores off Gebel El Zeit. Preliminary data exhibit partially reset ages trending as old as ~70 Ma (AHe) and ~450 Ma (ZHe) from shallower structural levels (Proterozoic basement and Phanerozoic cover sequence). Structurally deeper samples yield abundant AHe ages of ~22-24 Ma, indicative of rapid cooling and exhumation during the early Miocene. More</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27295732','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27295732"><span>Comprehensive Child Welfare Information <span class="hlt">System</span>. <span class="hlt">Final</span> rule.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p></p> <p>2016-06-02</p> <p>This <span class="hlt">final</span> rule replaces the Statewide and Tribal Automated Child Welfare Information <span class="hlt">Systems</span> (S/TACWIS) rule with the Comprehensive Child Welfare Information <span class="hlt">System</span> (CCWIS) rule. The rule also makes conforming amendments in rules in related requirements. This rule will assist title IV-E agencies in developing information management <span class="hlt">systems</span> that leverage new innovations and technology in order to better serve children and families. More specifically, this <span class="hlt">final</span> rule supports the use of cost-effective, innovative technologies to automate the collection of high-quality case management data and to promote its analysis, distribution, and use by workers, supervisors, administrators, researchers, and policy makers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/784986','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/784986"><span>Tunability of the NLC <span class="hlt">Final</span> Focus <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Seryi, Andrei</p> <p>2001-07-23</p> <p>The performance of the new NLC <span class="hlt">Final</span> Focus <span class="hlt">system</span> has been investigated as a function of the incoming beam characteristics, such as energy, emittances, energy spread. A preliminary study of the tolerances and the tunability of the <span class="hlt">system</span> is presented in this paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2007/1047/srp/srp108/of2007-1047srp108.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2007/1047/srp/srp108/of2007-1047srp108.pdf"><span>Structure of the central Terror <span class="hlt">Rift</span>, western Ross Sea, Antarctica</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hall, Jerome; Wilson, Terry; Henrys, Stuart</p> <p>2007-01-01</p> <p>The Terror <span class="hlt">Rift</span> is a zone of post-middle Miocene faulting and volcanism along the western margin of the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span>. A new seismic data set from NSF geophysical cruise NBP04-01, integrated with the previous dataset to provide higher spatial resolution, has been interpreted in this study in order to improve understanding of the architecture and history of the Terror <span class="hlt">Rift</span>. The Terror <span class="hlt">Rift</span> contains two components, a structurally-controlled rollover anticlinal arch intruded by younger volcanic bodies and an associated synclinal basin. Offsets and trend changes in fault patterns have been identified, coincident with shifts in the location of depocenters that define <span class="hlt">rift</span> sub-basins, indicating that the Terror <span class="hlt">Rift</span> is segmented by transverse structures. Multiple phases of faulting all post-date 17 Ma, including faults cutting the seafloor surface, indicating Neogene <span class="hlt">rifting</span> and possible modern activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.8403S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.8403S"><span>Parameters influencing the location and characteristics of volcanic eruptions in a youthful extensional setting: Insights from the Virunga Volcanic Province, in the Western Branch of the East African <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smets, Benoît; d'Oreye, Nicolas; Kervyn, Matthieu; Kervyn, François</p> <p>2016-04-01</p> <p>The East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS) is often mentioned as the modern archetype for <span class="hlt">rifting</span> and continental break-up (Calais et al., 2006, GSL Special Publication 259), showing the complex interaction between <span class="hlt">rift</span> faults, magmatism and pre-existing structures of the basement. Volcanism in the EARS is characterized by very active volcanoes, several of them being among the most active on Earth (Wright et al., 2015, GRL 42). Such intense volcanic activity provides useful information to study the relationship between <span class="hlt">rifting</span>, magmatism and volcanism. This is the case of the Virunga Volcanic Province (VVP) located in the central part of the Western Branch of the EARS, which hosts two of the most active African volcanoes, namely Nyiragongo and Nyamulagira. Despite the intense eruptive activity in the VVP, the spatial distribution of volcanism and its relationship with the extensional setting remain little known. Here we present a study of the interaction between tectonics, magmatism and volcanism at the scale of the Kivu <span class="hlt">rift</span> section, where the VVP is located, and at the scale of a volcano, by studying the dense historical eruptive activity of Nyamulagira. Both the complex Precambrian basement and magmatism appear to contribute to the development of the Kivu <span class="hlt">rift</span>. The presence of transfer zones north and south of the Lake Kivu <span class="hlt">rift</span> basin favoured the development of volcanic provinces at these locations. <span class="hlt">Rift</span> faults, including reactivated Precambrian structures influenced the location of volcanism within the volcanic provinces and the <span class="hlt">rift</span> basin. At a more local scale, the historical eruptive activity of Nyamulagira highlights that, once a composite volcano developed, the gravitational stress field induced by edifice loading becomes the main parameter that influence the location, duration and lava volume of eruptions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007PhDT.......218K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007PhDT.......218K"><span>Incipient continental <span class="hlt">rifting</span>: Insights from the Okavango <span class="hlt">Rift</span> Zone, northwestern Botswana</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kinabo, Baraka Damas</p> <p></p> <p>In this dissertation aeromagnetic, gravity, and Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) data from the Okavango <span class="hlt">Rift</span> Zone in northwest Botswana are used to map the distribution of <span class="hlt">rift</span> and basement structures. The distribution of these structures provide useful insights into the early stages of continental <span class="hlt">rifting</span>. The objectives of this study are (1) assessing the role of pre-existing structures on <span class="hlt">rift</span> basin development, (2) characterizing the geometry of the nascent <span class="hlt">rift</span> basins, (3) documenting fault growth and propagation patterns, and (4) investigating the border fault development. Potential field data especially aeromagnetic data are used to map out structures in the sediment covered basement, whereas SRTM DEM data express the surface morphology of the structures. The azimuth of <span class="hlt">rift</span> faults parallel the orientation of the fold axes and the prominent foliation directions of the basement rocks. This indicates that pre-existing structures in the basement influenced the development of the <span class="hlt">rift</span> structures. NE dipping faults consistently exhibit greater displacements than SE dipping faults, suggesting a developing half-graben geometry. Individual faults grow by along axis linkage of small segments that develop from soft linkage (under lapping to overlapping segments) to hard linkage (hooking, fused segments). Major <span class="hlt">rifts</span> faults are also linking through transfer zones by the process of "fault piracy" to establish an immature border fault <span class="hlt">system</span>. The relationships between scam heights and vertical throws reveal that the young and active faults are located outside the <span class="hlt">rift</span> while the faults with no recent activities are in the middle suggesting that the <span class="hlt">rift</span> is also growing in width. This study demonstrates the utility of potential field data and SRTM DEM to provide a 3-D view of incipient continental <span class="hlt">rifting</span> processes such as fault growth and propagation.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.206.1382K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.206.1382K"><span>Crustal structure and kinematics of the TAMMAR propagating <span class="hlt">rift</span> <span class="hlt">system</span> on the Mid-Atlantic Ridge from seismic refraction and satellite altimetry gravity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kahle, Richard L.; Tilmann, Frederik; Grevemeyer, Ingo</p> <p>2016-08-01</p> <p>The TAMMAR segment of the Mid-Atlantic Ridge forms a classic propagating <span class="hlt">system</span> centred about two degrees south of the Kane Fracture Zone. The segment is propagating to the south at a rate of 14 mm yr-1, 15 per cent faster than the half-spreading rate. Here, we use seismic refraction data across the propagating <span class="hlt">rift</span>, sheared zone and failed <span class="hlt">rift</span> to investigate the crustal structure of the <span class="hlt">system</span>. Inversion of the seismic data agrees remarkably well with crustal thicknesses determined from gravity modelling. We show that the crust is thickened beneath the highly magmatic propagating <span class="hlt">rift</span>, reaching a maximum thickness of almost 8 km along the seismic line and an inferred (from gravity) thickness of about 9 km at its centre. In contrast, the crust in the sheared zone is mostly 4.5-6.5 km thick, averaging over 1 km thinner than normal oceanic crust, and reaching a minimum thickness of only 3.5 km in its NW corner. Along the seismic line, it reaches a minimum thickness of under 5 km. The PmP reflection beneath the sheared zone and failed <span class="hlt">rift</span> is very weak or absent, suggesting serpentinisation beneath the Moho, and thus effective transport of water through the sheared zone crust. We ascribe this increased porosity in the sheared zone to extensive fracturing and faulting during deformation. We show that a bookshelf-faulting kinematic model predicts significantly more crustal thinning than is observed, suggesting that an additional mechanism of deformation is required. We therefore propose that deformation is partitioned between bookshelf faulting and simple shear, with no more than 60 per cent taken up by bookshelf faulting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT........48Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT........48Y"><span>Seismological investigation of the Okavango <span class="hlt">Rift</span>, Botswana</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Youqiang</p> <p></p> <p>The mechanisms of <span class="hlt">rifting</span> have been intensively investigated using geological and geophysical techniques beneath mature <span class="hlt">rift</span> zones. However, current understanding on the earliest stages of <span class="hlt">rifting</span> is seriously limited. Here we employ recently archived data from 17 broadband seismic stations traversing northern Botswana to conduct the first shear wave splitting and mantle transition zone (MTZ) studies within the Okavango <span class="hlt">Rift</span> Zone (ORZ). The ORZ is an incipient continental <span class="hlt">rift</span> situated at the terminal of the southwestern branch of the East African <span class="hlt">Rift</span> <span class="hlt">System</span>. The resulting normal MTZ thickness and consistently <span class="hlt">rift</span>-parallel fast polarizations imply an absence of significant thermal anomalies in the upper mantle, ruling out the role of mantle plumes in the initiation of the ORZ. The observed anisotropy beneath the ORZ and adjacent areas is mainly attributed to the relative movement between the lithosphere and asthenosphere with regional contributions from fabrics in the lithosphere and flow deflection by the bottom of the lithosphere. Our observations imply that the initiation and development of the ORZ can be initiated following a passive mode from the consequences of relative movements between the South African block and the rest of the African plate along a zone of lithospheric weakness between the Congo and Kalahari cratons. In addition, an approach was developed to effectively remove the near surface reverberations in the resulting receiver functions, decipher the P-to-S converted phases associated with the Moho discontinuity, and thus resolve sub-sediment crustal structure beneath stations sitting on a low-velocity sedimentary layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5840034','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5840034"><span>Cenozoic <span class="hlt">rift</span> tectonics of the Japan Sea</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kimura, K.</p> <p>1988-08-01</p> <p>The Japan Sea is one of the back-arc basins in trench-arc <span class="hlt">systems</span> bordering the western Pacific. Recent paleomagnetic works suggest the Japan Sea opened during early to middle Miocene. Radiometric and microfossil ages of the Cenozoic onland sequences in the Japanese Islands elucidate the <span class="hlt">rift</span> tectonics of the Japan Sea. The <span class="hlt">rifting</span> history is summarized as follows: nonmarine volcanic formations of prerift stage before 50 Ma, <span class="hlt">rift</span>-onset unconformity at 40 Ma, nonmarine volcanic formations of synrift stage 20-33 Ma, breakup unconformity 19 Ma showing the opening of the Japan Sea, marine volcanic and sedimentary formations of synrift stage 14.5-18 Ma, beginning of regional subsidence 14.5 Ma corresponding to the end of the Japan Sea opening, marine sedimentary formations of postdrift stage after 14.5 Ma. <span class="hlt">Rifting</span> is not limited to the synrift stage but is continued to the syndrift stage. <span class="hlt">Rifting</span> led to a horst-and-graben structure. Thus, the Cenozoic onland sequences in the Japanese Islands are suited for a study of <span class="hlt">rift</span> tectonics because the sequences were subaerially exposed by the late Miocene-Holocene island-arc tectonics. <span class="hlt">Rift</span> tectonics cannot be studied as easily in most Atlantic-type passive margins.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JGRE..112.9007F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JGRE..112.9007F"><span>Oblique <span class="hlt">rifting</span> at Tempe Fossae, Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fernández, Carlos; Anguita, Francisco</p> <p>2007-09-01</p> <p>This work shows the results of a structural study of the faults observed at the Tempe <span class="hlt">Rift</span> (northeastern Tharsis region), Mars. A new, detailed map of faults and fault <span class="hlt">systems</span> was used to geometrically characterize the fracture architecture of the Tempe <span class="hlt">Rift</span> and to measure fault length, displacement, and spacing data, to analyze the spatial distribution of fault centroids, and to investigate the fractal nature of fault trace maps. A comparison with analog models and the use of conventional techniques of fault population analysis show that the Tempe <span class="hlt">Rift</span> was most probably generated under sinistral oblique-<span class="hlt">rifting</span> processes, which highlights the importance of the presence of inherited fractures in the tectonic evolution of the Noachian crust. The angle between the extension direction and the <span class="hlt">rift</span> axis varies along the Tempe <span class="hlt">Rift</span>, ranging from 50°-60° at its central southern part to 66°-88° to the southwest. Fault scaling relationships are similar to those found at mid-ocean ridges on Earth with exponential fault length-frequency distributions. Localized, inhomogeneous deformation generated weakly interacting faults, spanning the entire thickness of the mechanical layer. This thickness decreased from southwest to northeast along the <span class="hlt">rift</span>, along with distance from the central part of the Tharsis dome.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=314037','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=314037"><span><span class="hlt">Rift</span> Valley Fever Virus</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p><span class="hlt">Rift</span> Valley fever virus (RVFV) is a mosquito-transmitted virus or arbovirus that is endemic in sub-Saharan Africa. In the last decade, <span class="hlt">Rift</span> Valley fever (RVF) outbreaks have resulted in loss of human and animal life, as well as had significant economic impact. The disease in livestock is primarily a...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T13A2514Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T13A2514Q"><span>Understanding the thermal and tectonic evolution of Marie Byrd Land from a reanalysis of airborne geophysical data in the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Quartini, E.; Powell, E. M.; Richter, T.; Damiani, T.; Burris, S. G.; Young, D. A.; Blankenship, D. D.</p> <p>2013-12-01</p> <p>The West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> (WARS) is a region characterized by a significant topographic range, a complex tectonic history, and active subglacial volcanism. Those elements exert a large influence on the stability of the West Antarctic Ice Sheet, which flows within the cradle-shaped <span class="hlt">rift</span> <span class="hlt">system</span> and is currently grounded well below sea level. This potentially unstable configuration is the motivation for gaining a better understanding of the ice sheet boundary conditions dictated by <span class="hlt">rift</span> evolution and how they impact the ice flow. In this study we focus on characterizing the distribution of and transition between sedimentary basins and inferred geothermal heat flux from the flanks to the floor of the <span class="hlt">rift</span> <span class="hlt">system</span>. We do so through analysis of gravity data both for sources within the deep lithosphere and near surface targets in the crust. A compilation of gravity datasets over West and Central Antarctica and the analysis thereof is presented. In particular we use gravity data collected during several airborne geophysical surveys: CASERTZ (1994-1997), SOAR/WMB (1997-1998), AGASEA (2004-2005), ICEBRIDGE (2008-2011), and GIMBLE (2012-2013). New processing and data reduction methodologies are applied to the older gravity surveys to improve the high frequency signal content and to make these surveys compatible with modern works (i.e. AGASEA, ICEBRIDGE, GIMBLE). The high frequency signal provides better resolution of small-scale features within survey blocks but long-wavelength integrity is retained by registering the airborne free-air disturbance within those blocks to the gravity disturbance derived from the GOCE global satellite gravity field. This allows for consistent long wavelength interpretation across the merged surveys and provides improved gravity analysis of the deep lithosphere while retaining the capacity to study smaller scale features. A crustal model for the area is produced using the Bouguer anomaly and spectral analyses of the Bouguer anomaly and free</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T33B4659B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T33B4659B"><span>The Role of <span class="hlt">Rift</span> Obliquity During Pangea Fragmentation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brune, S.; Butterworth, N. P.; Williams, S.; Müller, D.</p> <p>2014-12-01</p> <p>Does supercontinent break-up follow specific laws? What parameters control the success and the failure of <span class="hlt">rift</span> <span class="hlt">systems</span>? Recent analytical and geodynamic modeling suggests that oblique <span class="hlt">rifting</span> is energetically preferred over orthogonal <span class="hlt">rifting</span>. This implies that during <span class="hlt">rift</span> competition, highly oblique branches proceed to break-up while less oblique ones become inactive. These models predict that the relative motion of Earth's continents during supercontinent break-up is affected by the orientation and shape of individual <span class="hlt">rift</span> <span class="hlt">systems</span>. Here, we test this hypothesis based on latest plate tectonic reconstructions. Using PyGPlates, a recently developed Python library that allows script-based access to the plate reconstruction software GPlates, we quantify <span class="hlt">rift</span> obliquity, extension velocity and their temporal evolution for continent-scale <span class="hlt">rift</span> <span class="hlt">systems</span> of the past 200 Myr. Indeed we find that many <span class="hlt">rift</span> <span class="hlt">systems</span> contributing to Pangea fragmentation involved strong <span class="hlt">rift</span> obliquity. East and West Gondwana for instance split along the East African coast with a mean obliquity of 55° (measured as the angle between local <span class="hlt">rift</span> trend normal and extension direction). While formation of the central and southern South Atlantic segment involved a low obliquity of 10°, the Equatorial Atlantic opened under a high angle of 60°. <span class="hlt">Rifting</span> between Australia and Antarctica involved two stages with 25° prior to 100 Ma followed by 50° obliquity and distinct increase of extension velocity. Analyzing the entire passive margin <span class="hlt">system</span> that formed during Pangea breakup, we find a mean obliquity of 40°, with a standard deviation of 20°. Hence 50% of these margins formed with an angle of 40° or more. Considering that many conceptual models of <span class="hlt">rifting</span> and passive margin formation assume 2D deformation, our study quantifies the degree to which such 2D models are globally applicable, and highlights the importance of 3D models where oblique <span class="hlt">rifting</span> is the dominant mode of deformation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25517098','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25517098"><span>Segmented lateral dyke growth in a <span class="hlt">rifting</span> event at Bárðarbunga volcanic <span class="hlt">system</span>, Iceland.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sigmundsson, Freysteinn; Hooper, Andrew; Hreinsdóttir, Sigrún; Vogfjörd, Kristín S; Ófeigsson, Benedikt G; Heimisson, Elías Rafn; Dumont, Stéphanie; Parks, Michelle; Spaans, Karsten; Gudmundsson, Gunnar B; Drouin, Vincent; Árnadóttir, Thóra; Jónsdóttir, Kristín; Gudmundsson, Magnús T; Högnadóttir, Thórdís; Fridriksdóttir, Hildur María; Hensch, Martin; Einarsson, Páll; Magnússon, Eyjólfur; Samsonov, Sergey; Brandsdóttir, Bryndís; White, Robert S; Ágústsdóttir, Thorbjörg; Greenfield, Tim; Green, Robert G; Hjartardóttir, Ásta Rut; Pedersen, Rikke; Bennett, Richard A; Geirsson, Halldór; La Femina, Peter C; Björnsson, Helgi; Pálsson, Finnur; Sturkell, Erik; Bean, Christopher J; Möllhoff, Martin; Braiden, Aoife K; Eibl, Eva P S</p> <p>2015-01-08</p> <p>Crust at many divergent plate boundaries forms primarily by the injection of vertical sheet-like dykes, some tens of kilometres long. Previous models of <span class="hlt">rifting</span> events indicate either lateral dyke growth away from a feeding source, with propagation rates decreasing as the dyke lengthens, or magma flowing vertically into dykes from an underlying source, with the role of topography on the evolution of lateral dykes not clear. Here we show how a recent segmented dyke intrusion in the Bárðarbunga volcanic <span class="hlt">system</span> grew laterally for more than 45 kilometres at a variable rate, with topography influencing the direction of propagation. Barriers at the ends of each segment were overcome by the build-up of pressure in the dyke end; then a new segment formed and dyke lengthening temporarily peaked. The dyke evolution, which occurred primarily over 14 days, was revealed by propagating seismicity, ground deformation mapped by Global Positioning <span class="hlt">System</span> (GPS), interferometric analysis of satellite radar images (InSAR), and graben formation. The strike of the dyke segments varies from an initially radial direction away from the Bárðarbunga caldera, towards alignment with that expected from regional stress at the distal end. A model minimizing the combined strain and gravitational potential energy explains the propagation path. Dyke opening and seismicity focused at the most distal segment at any given time, and were simultaneous with magma source deflation and slow collapse at the Bárðarbunga caldera, accompanied by a series of magnitude M > 5 earthquakes. Dyke growth was slowed down by an effusive fissure eruption near the end of the dyke. Lateral dyke growth with segment barrier breaking by pressure build-up in the dyke distal end explains how focused upwelling of magma under central volcanoes is effectively redistributed over long distances to create new upper crust at divergent plate boundaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Natur.517..191S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Natur.517..191S"><span>Segmented lateral dyke growth in a <span class="hlt">rifting</span> event at Bárðarbunga volcanic <span class="hlt">system</span>, Iceland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sigmundsson, Freysteinn; Hooper, Andrew; Hreinsdóttir, Sigrún; Vogfjörd, Kristín S.; Ófeigsson, Benedikt G.; Heimisson, Elías Rafn; Dumont, Stéphanie; Parks, Michelle; Spaans, Karsten; Gudmundsson, Gunnar B.; Drouin, Vincent; Árnadóttir, Thóra; Jónsdóttir, Kristín; Gudmundsson, Magnús T.; Högnadóttir, Thórdís; Fridriksdóttir, Hildur María; Hensch, Martin; Einarsson, Páll; Magnússon, Eyjólfur; Samsonov, Sergey; Brandsdóttir, Bryndís; White, Robert S.; Ágústsdóttir, Thorbjörg; Greenfield, Tim; Green, Robert G.; Hjartardóttir, Ásta Rut; Pedersen, Rikke; Bennett, Richard A.; Geirsson, Halldór; La Femina, Peter C.; Björnsson, Helgi; Pálsson, Finnur; Sturkell, Erik; Bean, Christopher J.; Möllhoff, Martin; Braiden, Aoife K.; Eibl, Eva P. S.</p> <p>2015-01-01</p> <p>Crust at many divergent plate boundaries forms primarily by the injection of vertical sheet-like dykes, some tens of kilometres long. Previous models of <span class="hlt">rifting</span> events indicate either lateral dyke growth away from a feeding source, with propagation rates decreasing as the dyke lengthens, or magma flowing vertically into dykes from an underlying source, with the role of topography on the evolution of lateral dykes not clear. Here we show how a recent segmented dyke intrusion in the Bárðarbunga volcanic <span class="hlt">system</span> grew laterally for more than 45 kilometres at a variable rate, with topography influencing the direction of propagation. Barriers at the ends of each segment were overcome by the build-up of pressure in the dyke end; then a new segment formed and dyke lengthening temporarily peaked. The dyke evolution, which occurred primarily over 14 days, was revealed by propagating seismicity, ground deformation mapped by Global Positioning <span class="hlt">System</span> (GPS), interferometric analysis of satellite radar images (InSAR), and graben formation. The strike of the dyke segments varies from an initially radial direction away from the Bárðarbunga caldera, towards alignment with that expected from regional stress at the distal end. A model minimizing the combined strain and gravitational potential energy explains the propagation path. Dyke opening and seismicity focused at the most distal segment at any given time, and were simultaneous with magma source deflation and slow collapse at the Bárðarbunga caldera, accompanied by a series of magnitude M > 5 earthquakes. Dyke growth was slowed down by an effusive fissure eruption near the end of the dyke. Lateral dyke growth with segment barrier breaking by pressure build-up in the dyke distal end explains how focused upwelling of magma under central volcanoes is effectively redistributed over long distances to create new upper crust at divergent plate boundaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1710322S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1710322S"><span>Segmented lateral dyke growth in a <span class="hlt">rifting</span> event at Bárðarbunga volcanic <span class="hlt">system</span>, Iceland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sigmundsson, Freysteinn; Hooper, Andrew; Hreinsdóttir, Sigrún; Vogfjörd, Kristín S.; Ófeigsson, Benedikt; Rafn Heimisson, Elías; Dumont, Stéphanie; Parks, Michelle; Spaans, Karsten; Guðmundsson, Gunnar B.; Drouin, Vincent; Árnadóttir, Thóra; Jónsdóttir, Kristín; Gudmundsson, Magnús T.; Samsonov, Sergey; Brandsdóttir, Bryndís; White, Robert; Ágústsdóttir, Thorbjörg; Björnsson, Helgi; Bean, Christopher J.</p> <p>2015-04-01</p> <p>Crust at many divergent plate boundaries forms primarily by the injection of vertical sheet-like dykes, some tens of km long. Previous models of <span class="hlt">rifting</span> events indicate either a lateral dyke growth away from a feeding source, with propagation rates decreasing as the dyke lengthens, or magma flowing vertically into dykes from an underlying source, with the role of topography on the evolution of lateral dykes not clear. We show how a recent segmented dyke intrusion in the Bárðarbunga volcanic <span class="hlt">system</span>, grew laterally for over 45 km at a variable rate, with an influence of topography on the direction of propagation. Barriers at the ends of each segment were overcome by the build-up of pressure in the dyke end; then a new segment formed and dyke lengthening temporarily peaked. The dyke evolution, which occurred over 14 days, was revealed by propagating seismicity, ground deformation mapped by Global Positioning <span class="hlt">System</span> (GPS), interferometric analysis of satellite radar images (InSAR), and graben formation. The strike of the dyke segments varies from an initially radial direction away from the Bárðarbunga caldera, towards alignment with that expected from regional stress at the distal end. A model minimizing the combined strain and gravitational potential energy explains the propagation path. Dyke opening and seismicity focused at the most distal segment at any given time, and were simultaneous with a magma source deflation and slow collapse at the Bárðarbunga caldera, accompanied by a series of M>5 earthquakes. The dyke growth was slowed down by an effusive fissure eruption near the end of the dyke. Lateral dyke growth with segment barrier breaking by pressure build-up in the dyke distal end explains how focused upwelling of magma under central volcanoes is effectively redistributed over long distances to create new upper crust at divergent plate boundaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T53C..05B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T53C..05B"><span>How Mountains Become <span class="hlt">Rifts</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buiter, S. J.; Tetreault, J. L.</p> <p>2015-12-01</p> <p><span class="hlt">Rifting</span> often initiates on former continental collision zones. For example, the present-day passive margins of the Atlantic and Indian Oceans formed after continental break-up occurred on relatively young and very old sutures, such as Morocco-Nova Scotia and East Antarctica-Australia, respectively. <span class="hlt">Rifts</span> may localize on former collision zones for several reasons: orogens are thermally weak because of the increase in heat producing elements in their thicker crustal root, the inherited thrust faults form large-scale heterogeneities, and in the case of young sutures, extensional collapse of the orogen may help initiate <span class="hlt">rifting</span>. We highlight the impact of collision zone inheritance on continental extension and <span class="hlt">rifted</span> margin architecture using numerical experiments. We first explicitly prescribe collisional structures in the initial setup, such as increased crustal thickness and inherited thrust faults. Varying the prescribed structures results in different <span class="hlt">rift</span> to break-up durations and margin widths. Our second series of experiments creates a collision zone through subduction and closure of an ocean. We confirm that post-collisional collapse is not a sufficient trigger for continental <span class="hlt">rifting</span> and that a change in regional plate motions is required. When extension occurs, the weak former subduction interface and the elevated temperatures in the crustal nappe stack work in tandem as the main deformation localizers for continental <span class="hlt">rifting</span>. Our experiments show that different approaches of initiating a continental <span class="hlt">rift</span> result in different dynamics of the crust and mantle, thereby impacting <span class="hlt">rift</span> geometry, <span class="hlt">rift</span> to break-up duration, and exhumation of subduction-related sediments and oceanic crust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1039656','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1039656"><span><span class="hlt">Final</span> Report Computational Analysis of Dynamical <span class="hlt">Systems</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Guckenheimer, John</p> <p>2012-05-08</p> <p>This is the <span class="hlt">final</span> report for DOE Grant DE-FG02-93ER25164, initiated in 1993. This grant supported research of John Guckenheimer on computational analysis of dynamical <span class="hlt">systems</span>. During that period, seventeen individuals received PhD degrees under the supervision of Guckenheimer and over fifty publications related to the grant were produced. This document contains copies of these publications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMGP11A0732K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMGP11A0732K"><span>Paleomagnetism and paleointensity of Mid-Continental <span class="hlt">Rift</span> <span class="hlt">System</span> basalts at Silver Mountain and Sturgeon River Falls (Upper Michigan)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kulakov, E.; Piispa, E. J.; Laird, M. S.; Smirnov, A. V.; Diehl, J. F.</p> <p>2009-12-01</p> <p>Paleomagnetic and paleointensity data from Precambrian rocks are of great importance for understanding the early geodynamo and tectonic evolution of the Earth. We will present results from a rock magnetic and paleomagnetic investigation of basaltic lava flow sequences at Silver Mountain and Sturgeon River Falls in Upper Michigan. While the Silver Mountain and Sturgeon River Falls lava flows have not been radiometrically dated, these rocks have been assigned to the Siemens Creek Volcanics, the lowermost member of ~1.1 Ga Powder Mill Group (PMG). The PMG represents one of the oldest volcanic units associated with the Mid-Continental <span class="hlt">Rift</span> <span class="hlt">System</span> (MCRS). We sampled 13 lava flows from the Silver Mountain and two lava flows from the Sturgeon River Falls exposures (a minimum of 15 cores per flow were taken). Paleomagnetic directions were determined from detailed thermal and/or alternating field demagnetization preceded by an initial low-temperature (liquid nitrogen) demagnetization. Most specimens revealed a single- or a two-component remanent magnetization. At both locations, the characteristic remanent magnetization (ChRM) has a reversed direction with very steep inclination similar to that found in other rocks representing the early stages of MCRS. Our magnetic hysteresis measurements, unblocking temperature spectra, and scanning electron microscopy analyses suggest low-Ti, pseudosingle-domain titanomagnetite as the principal magnetic carrier in these rocks. For paleointensity determinations, we applied the multispecimen parallel differential pTRM method. These data add to the Precambrian paleointensity database which otherwise remains limited because of alteration and other factors hampering the applicability of conventional Thellier double-heating method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21080318','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21080318"><span>TerraSAR-X high-resolution radar remote sensing: an operational warning <span class="hlt">system</span> for <span class="hlt">Rift</span> Valley fever risk.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vignolles, Cécile; Tourre, Yves M; Mora, Oscar; Imanache, Laurent; Lafaye, Murielle</p> <p>2010-11-01</p> <p>In the vicinity of the Barkedji village (in the Ferlo region of Senegal), the abundance and aggressiveness of the vector mosquitoes for <span class="hlt">Rift</span> Valley fever (RVF) are strongly linked to rainfall events and associated ponds dynamics. Initially, these results were obtained from spectral analysis of high-resolution (~10 m) Spot-5 images, but, as a part of the French AdaptFVR project, identification of the free water dynamics within ponds was made with the new high-resolution (down to 3-meter pixels), Synthetic Aperture Radar satellite (TerraSAR-X) produced by Infoterra GmbH, Friedrichshafen/Potsdam, Germany. During summer 2008, within a 30 x 50 km radar image, it was found that identified free water fell well within the footprints of ponds localized by optical data (i.e. Spot-5 images), which increased the confidence in this new and complementary remote sensing technique. Moreover, by using near real-time rainfall data from the Tropical Rainfall Measuring Mission (TRMM), NASA/JAXA joint mission, the filling-up and flushing-out rates of the ponds can be accurately determined. The latter allows for a precise, spatio-temporal mapping of the zones potentially occupied by mosquitoes capable of revealing the variability of pond surfaces. The risk for RVF infection of gathered bovines and small ruminants (~1 park/km(2)) can thus be assessed. This new operational approach (which is independent of weather conditions) is an important development in the mapping of risk components (i.e. hazards plus vulnerability) related to RVF transmission during the summer monsoon, thus contributing to a RVF early warning <span class="hlt">system</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.T22B..04M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.T22B..04M"><span>From hyper-extended <span class="hlt">rifts</span> to orogens: the example of the Mauléon <span class="hlt">rift</span> basin in the Western Pyrenees (SW France)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Masini, E.; Manatschal, G.; Tugend, J.</p> <p>2011-12-01</p> <p>An integral part of plate tectonic theory is that the fate of <span class="hlt">rifted</span> margins is to be accreted into mountain belts. Thus, <span class="hlt">rift</span>-related inheritance is an essential parameter controlling the evolution and architecture of collisional orogens. Although this link is well accepted, <span class="hlt">rift</span> inheritance is often ignored. The Pyrenees, located along the Iberian and European plate boundary, can be considered as one of the best places to study the reactivation of former <span class="hlt">rift</span> structures. In this orogen the Late Cretaceous and Tertiary convergence overprints a Late Jurassic to Lower Cretaceous complex intracontinental <span class="hlt">rift</span> <span class="hlt">system</span> related to the opening of the North Atlantic. During the <span class="hlt">rifting</span>, several strongly subsiding basins developed in the axis of the Pyrenees showing evidence of extreme crustal extension and even locale mantle exhumation to the seafloor. Although the exact age and kinematics of <span class="hlt">rifting</span> is still debated, these structures have an important impact in the subsequent orogenic overprint. In our presentation we discuss the example of the Mauléon basin, which escaped from the most pervasive deformations because of its specific location at the interface between the western termination of the chain and the Bay of Biscay oceanic realm. Detailed mapping combined with seismic reflection, gravity data and industry wells enabled to determine the 3D <span class="hlt">rift</span> architecture of the Mauléon basin. Two major diachronous detachment <span class="hlt">systems</span> can be mapped and followed through space. The Southern Mauléon Detachment (SMD) develops first, starts to thin the crust and floors the Southern Mauléon sub-Basin (SMB). The second, the Northern Mauléon Detachment (SMD) is younger and controls the <span class="hlt">final</span> crustal thinning and mantle exhumation to the north. Both constitute the whole Mauléon basin. Like at the scale of the overall Pyrenees, the reactivation of the Mauléon Basin increases progressively from west to east, which enables to document the progressive reactivation of an aborted hyper</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://gcsproceedings.sepmonline.org/content/gcs034/1/SEC27.abstract','USGSPUBS'); return false;" href="http://gcsproceedings.sepmonline.org/content/gcs034/1/SEC27.abstract"><span>Late Jurassic – early Cretaceous inversion of <span class="hlt">rift</span> structures, and linkage of petroleum <span class="hlt">system</span> elements across post-<span class="hlt">rift</span> unconformity, U.S. Chukchi Shelf, arctic Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Houseknecht, David W.; Connors, Christopher D.</p> <p>2015-01-01</p> <p>Oil-prone source rocks, reservoir-quality sandstone, migration pathways, and structural closure are linked intimately across the Jurassic unconformity, which reflects inversion. Thus, all these key petroleum <span class="hlt">systems</span> elements were in place when Triassic source rocks entered the oil generation window during Cretaceous–Cenozoic stratigraphic burial.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008Tecto..27.3013K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008Tecto..27.3013K"><span>Fault growth and propagation during incipient continental <span class="hlt">rifting</span>: Insights from a combined aeromagnetic and Shuttle Radar Topography Mission digital elevation model investigation of the Okavango <span class="hlt">Rift</span> Zone, northwest Botswana</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kinabo, B. D.; Hogan, J. P.; Atekwana, E. A.; Abdelsalam, M. G.; Modisi, M. P.</p> <p>2008-06-01</p> <p>Digital Elevation Models (DEM) extracted from the Shuttle Radar Topography Mission (SRTM) data and high-resolution aeromagnetic data are used to characterize the growth and propagation of faults associated with the early stages of continental extension in the Okavango <span class="hlt">Rift</span> Zone (ORZ), northwest Botswana. Significant differences in the height of fault scarps and the throws across the faults in the basement indicate extended fault histories accompanied by sediment accumulation within the <span class="hlt">rift</span> graben. Faults in the center of the <span class="hlt">rift</span> either lack topographic expressions or are interpreted to have become inactive, or have large throws and small scarp heights indicating waning activity. Faults on the outer margins of the <span class="hlt">rift</span> exhibit either (1) large throws or significant scarp heights and are considered older and active or (2) throws and scarp heights that are in closer agreement and are considered young and active. Fault linkages between major fault <span class="hlt">systems</span> through a process of "fault piracy" have combined to establish an immature border fault for the ORZ. Thus, in addition to growing in length (by along-axis linkage of segments), the <span class="hlt">rift</span> is also growing in width (by transferring motion to younger faults along the outer margins while abandoning older faults in the middle). <span class="hlt">Finally</span>, utilization of preexisting zones of weakness allowed the development of very long faults (>100 km) at a very early stage of continental <span class="hlt">rifting</span>, explaining the apparent paradox between the fault length versus throw for this young <span class="hlt">rift</span>. This study clearly demonstrates that the integration of the SRTM DEM and aeromagnetic data provides a 3-D view of the faults and fault <span class="hlt">systems</span>, providing new insight into fault growth and propagation during the nascent stages of continental <span class="hlt">rifting</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6747539','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6747539"><span>Volcanism at <span class="hlt">rifts</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>White, R.S.; McKenzie, D.P.</p> <p>1989-07-01</p> <p>The earth's outer shell <span class="hlt">rifts</span> continuously, stretching and splitting both on the ocean's floor and on continents. Every 30 million years or so the <span class="hlt">rifting</span> becomes cataclysmic, releasing continent-size floods of magma. This paper explains that the same mechanism is at work in both cases, the difference being in the slightly hotter temperature of the parent mantle for spectacular volcanic outbursts. Two kinds of evidence are described: quantitative descriptions of rock melting and a wide range of observations made on the <span class="hlt">rifted</span> edges of continents and in the oceans that have opened between them.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.8501G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.8501G"><span>Tectono-Sedimentary Analysis of <span class="hlt">Rift</span> Basins: Insights from the Corinth <span class="hlt">Rift</span>, Greece</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gawthorpe, Robert; Ford, Mary</p> <p>2015-04-01</p> <p>Existing models for the tectono-sedimentary evolution of <span class="hlt">rift</span> basins are strongly linked the growth and linkage of normal fault segments and localization of fault activity. Early stages of faulting (<span class="hlt">rift</span> initiation phase) are characterized by distributed, short, low displacement fault segments, subdued fault-related topography and small depocentres within which sedimentation keeps pace with subsidence. Following linkage and displacement localization (<span class="hlt">rift</span> climax phase), deformation if focused onto major, crustal-scale fault zones with kilometre-scale displacement. These major faults generate pronounced tilted fault-block topography, with subsidence rates that outpace sedimentation causing a pronounced change to deep-water deposition. Such models have been successful in helping to understand the gross structural and sedimentary evolution of <span class="hlt">rift</span> basins, but recent work has suggested that pre-existing structures, normal fault interaction with pre-<span class="hlt">rift</span> salt and antecedent drainage <span class="hlt">systems</span> significantly alter this initiation-to-climax perspective of <span class="hlt">rift</span> basin development. The E-W-striking, Pliocene-Pleistocene Corinth <span class="hlt">rift</span>, central Greece, is an excellent natural laboratory for studying the tectono-sedimentary evolution of <span class="hlt">rift</span> basins due to its young age, excellent onshore exposure of syn-<span class="hlt">rift</span> structure and stratigraphy and extensive offshore seismic data. The <span class="hlt">rift</span> cuts across the NW-SE-striking Hellenide mountain belt and has migrated northward and westward during its evolution. The Hellenide mountain belt significantly influences topography and drainage in the west of the <span class="hlt">rift</span>. High topography and large antecedent drainage <span class="hlt">systems</span>, focused along palaeovalleys, provided high sediment flux to NE-flowing alluvial <span class="hlt">systems</span> that overfilled early-<span class="hlt">rift</span> depocentres. Further east, away from the main antecedent drainage networks, contemporaneous deposits comprise deep-lacustrine turbidite channel and lobe complexes and basinal marls. Thus the stratigraphic expression within</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1023141','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1023141"><span>DCE Bio Detection <span class="hlt">System</span> <span class="hlt">Final</span> Report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lind, Michael A.; Batishko, Charles R.; Morgen, Gerald P.; Owsley, Stanley L.; Dunham, Glen C.; Warner, Marvin G.; Willett, Jesse A.</p> <p>2007-12-01</p> <p>The DCE (DNA Capture Element) Bio-Detection <span class="hlt">System</span> (Biohound) was conceived, designed, built and tested by PNNL under a MIPR for the US Air Force under the technical direction of Dr. Johnathan Kiel and his team at Brooks City Base in San Antonio Texas. The project was directed toward building a measurement device to take advantage of a unique aptamer based assay developed by the Air Force for detecting biological agents. The assay uses narrow band quantum dots fluorophores, high efficiency fluorescence quenchers, magnetic micro-beads beads and selected aptamers to perform high specificity, high sensitivity detection of targeted biological materials in minutes. This <span class="hlt">final</span> report summarizes and documents the <span class="hlt">final</span> configuration of the <span class="hlt">system</span> delivered to the Air Force in December 2008</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1984E%26PSL..67..219F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1984E%26PSL..67..219F"><span>How many <span class="hlt">rifts</span> are there in West Africa?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Freeth, S. J.</p> <p>1984-02-01</p> <p>The West African <span class="hlt">Rift</span> <span class="hlt">System</span> has, for the last ten years, been thought to consist of five interconnected <span class="hlt">rifts</span> extending from the Gulf of Guinea deep into the heart of Africa. Careful re-examination of the geophysical evidence makes it quite clear that there are only three interconnected <span class="hlt">rifts</span> in West Africa; the Lower Benue <span class="hlt">Rift</span> which extends to the northeast from the Gulf of Guinea to a triple junction near Chum, and the Gongola and Yola <span class="hlt">Rifts</span> which extend to the north and east, respectively, from the Chum triple junction. These three <span class="hlt">rifts</span> opened during the earlier part of the Mesozoic and were subsequently filled with Cretaceous sediments. The evidence for two further <span class="hlt">rifts</span>, the Ati <span class="hlt">Rift</span> and the Fort Archambault <span class="hlt">Rift</span> which were thought to extend to the northeast and southeast, respectively, from a triple junction at the eastern end of the Yola <span class="hlt">Rift</span>, does not stand up to re-examination. The "Ati <span class="hlt">Rift</span>" was thought to follow a major linear positive gravity anomaly which had been mapped beneath the Quaternary sediments of the Chad Basin. The main gravity anomaly is separated from the Yola <span class="hlt">Rift</span> by over 300 km and is probably due to a linear body of basic volcanic or volcano-clastic rocks associated with a suture of Pan-African age. Within the gap, between the main anomaly and the Yola <span class="hlt">Rift</span>, there are three localised positive anomalies which relate to a gabbro of Precambrian age, a band of dense meta-sediments within the Basement Complex and an acid igneous complex of Palaeogene age. The anomaly as a whole is therefore a sequence of unrelated anomalies, none of which are due to features of Mesozoic age. The "Fort Archambault <span class="hlt">Rift</span>" was thought to follow a major linear negative gravity anomaly which has been mapped beneath the Quaternary sediments of the Chad Basin. To a large extent the negative anomaly overlies the fosse de Baké-Birao (Baké-Birao Basin) which is itself part of a far larger structure that extends, parallel to the southern margin of the West African</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.T53A1586P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.T53A1586P"><span>How is continental break-up recorded in magma-poor <span class="hlt">rifted</span> margins?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Peron-Pinvidic, G.; Manatschal, G.; Minshull, T.; Sawyer, D.</p> <p>2006-12-01</p> <p>In classical models of continental break-up, <span class="hlt">rifting</span> is immediately followed by seafloor spreading, which implies that break-up can be identified as a specific spatial and temporal boundary. However, this simple concept is not supported by observations at <span class="hlt">rifted</span> margins. The classical indicators for determining break-up (break-up unconformity, magnetic anomalies, distribution of high-angle faults and sedimentary wedges) may no longer be relied upon to identify unambiguously the location and age of break-up. We studied the spatial and temporal evolution of the deep Iberia-Newfoundland margins, which are the type examples of magma-poor <span class="hlt">rifted</span> margins. Our study was based on borehole data and on a mapping of the sedimentary and basement architecture in 3D on seismic reflection profiles. Our results allow us to describe the tectono-sedimentary and morpho-tectonic evolution of <span class="hlt">final</span> <span class="hlt">rifting</span> and show that continental break-up is complex. In the Iberia-Newfoundland <span class="hlt">rift</span> <span class="hlt">system</span>, the tectono-sedimentary evolution of <span class="hlt">final</span> <span class="hlt">rifting</span> can be reconstructed back to 145Ma, when the crust was already thinned to less than 10km. Two major deformation phases have been identified: a first, Tithonian to Barremian in age (145-128Ma) and a second, dated as latest Aptian (112Ma). The Tithonian-Barremian phase is characterized by a migration of the tectonic activity oceanwards and a change of the deformation mechanisms from south to north, from zones of mantle exhumed via downward concave faults to classical half-grabens formed by the normal tilting of thinned continental blocks along upward concave faults. This phase terminates with the formation of the first unequivocal magnetic anomaly (M3 128Ma) and the accretion of more than 170km of crust, at rates of about 1cm/yr, that is neither oceanic nor continental, commonly referred to as Zone of Exhumed Continental Mantle (ZECM). The late-Aptian phase is associated with a major tectono-magmatic event and is responsible for the observed basement</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005GeoJI.161..707S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005GeoJI.161..707S"><span>An updated global earthquake catalogue for stable continental regions: reassessing the correlation with ancient <span class="hlt">rifts</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schulte, Saskia M.; Mooney, Walter D.</p> <p>2005-06-01</p> <p>We present an updated global earthquake catalogue for stable continental regions (SCRs; i.e. intraplate earthquakes) that is available on the Internet. Our database contains information on location, magnitude, seismic moment and focal mechanisms for over 1300 M (moment magnitude) >= 4.5 historic and instrumentally recorded crustal events. Using this updated earthquake database in combination with a recently published global catalogue of <span class="hlt">rifts</span>, we assess the correlation of intraplate seismicity with ancient <span class="hlt">rifts</span> on a global scale. Each tectonic event is put into one of five categories based on location: (i) interior <span class="hlt">rifts</span>/taphrogens, (ii) <span class="hlt">rifted</span> continental margins, (iii) non-<span class="hlt">rifted</span> crust, (iv) possible interior <span class="hlt">rifts</span> and (v) possible <span class="hlt">rifted</span> margins. We find that approximately 27 per cent of all events are classified as interior <span class="hlt">rifts</span> (i), 25 per cent are <span class="hlt">rifted</span> continental margins (ii), 36 per cent are within non-<span class="hlt">rifted</span> crust (iii) and 12 per cent (iv and v) remain uncertain. Thus, over half (52 per cent) of all events are associated with <span class="hlt">rifted</span> crust, although within the continental interiors (i.e. away from continental margins), non-<span class="hlt">rifted</span> crust has experienced more earthquakes than interior <span class="hlt">rifts</span>. No major change in distribution is found if only large (M>= 6.0) earthquakes are considered. The largest events (M>= 7.0) however, have occurred predominantly within <span class="hlt">rifts</span> (50 per cent) and continental margins (43 per cent). Intraplate seismicity is not distributed evenly. Instead several zones of concentrated seismicity seem to exist. This is especially true for interior <span class="hlt">rifts</span>/taphrogens, where a total of only 12 regions are responsible for 74 per cent of all events and as much as 98 per cent of all seismic moment released in that category. Of the four <span class="hlt">rifts</span>/taphrogens that have experienced the largest earthquakes, seismicity within the Kutch <span class="hlt">rift</span>, India, and the East China <span class="hlt">rift</span> <span class="hlt">system</span>, may be controlled by diffuse plate boundary deformation more than by the presence</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70029536','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70029536"><span>An updated global earthquake catalogue for stable continental regions: Reassessing the correlation with ancient <span class="hlt">rifts</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Schulte, S.M.; Mooney, W.D.</p> <p>2005-01-01</p> <p>We present an updated global earthquake catalogue for stable continental regions (SCRs; i.e. intraplate earthquakes) that is available on the Internet. Our database contains information on location, magnitude, seismic moment and focal mechanisms for over 1300 M (moment magnitude) ??? 4.5 historic and instrumentally recorded crustal events. Using this updated earthquake database in combination with a recently published global catalogue of <span class="hlt">rifts</span>, we assess the correlation of intraplate seismicity with ancient <span class="hlt">rifts</span> on a global scale. Each tectonic event is put into one of five categories based on location: (i) interior <span class="hlt">rifts</span>/taphrogens, (ii) <span class="hlt">rifted</span> continental margins, (iii) non-<span class="hlt">rifted</span> crust, (iv) possible interior <span class="hlt">rifts</span> and (v) possible <span class="hlt">rifted</span> margins. We find that approximately 27 per cent of all events are classified as interior <span class="hlt">rifts</span> (i), 25 per cent are <span class="hlt">rifted</span> continental margins (ii), 36 per cent are within non-<span class="hlt">rifted</span> crust (iii) and 12 per cent (iv and v) remain uncertain. Thus, over half (52 per cent) of all events are associated with <span class="hlt">rifted</span> crust, although within the continental interiors (i.e. away from continental margins), non-<span class="hlt">rifted</span> crust has experienced more earthquakes than interior <span class="hlt">rifts</span>. No major change in distribution is found if only large (M ??? 6.0) earthquakes are considered. The largest events (M ??? 7.0) however, have occurred predominantly within <span class="hlt">rifts</span> (50 per cent) and continental margins (43 per cent). Intraplate seismicity is not distributed evenly. Instead several zones of concentrated seismicity seem to exist. This is especially true for interior <span class="hlt">rifts</span>/taphrogens, where a total of only 12 regions are responsible for 74 per cent of all events and as much as 98 per cent of all seismic moment released in that category. Of the four <span class="hlt">rifts</span>/taphrogens that have experienced the largest earthquakes, seismicity within the Kutch <span class="hlt">rift</span>, India, and the East China <span class="hlt">rift</span> <span class="hlt">system</span>, may be controlled by diffuse plate boundary deformation more than by the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5788199','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5788199"><span>Evaluation of geothermal potential of Rio Grande <span class="hlt">rift</span> and Basin and Range province, New Mexico. <span class="hlt">Final</span> technical report, January 1, 1977-May 31, 1978</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Callender, J.F.</p> <p>1985-04-01</p> <p>A study was made of the geological, geochemical and geophysical characteristics of potential geothermal areas in the Rio Grande <span class="hlt">rift</span> and Basin and Range province of New Mexico. Both regional and site-specific information is presented. Data was collected by: (1) reconnaissance and detailed geologic mapping, emphasizing Neogene stratigraphy and structure; (2) petrologic studies of Neogene igneous rocks; (3) radiometric age-dating; (4) geochemical surveying, including regional and site-specific water chemistry, stable isotopic analyses of thermal waters, whole-rock and mineral isotopic studies, and whole-rock chemical analyses; and (5) detailed geophysical surveys, using electrical, gravity and magnetic techniques, with electrical resistivity playing a major role. Regional geochemical water studies were conducted for the whole state. Integrated site-specific studies included the Animas Valley, Las Cruces area (Radium Springs and Las Alturas Estates), Truth or Consequences region, the Albuquerque basin, the San Ysidro area, and the Abiquiu-Ojo Caliente region. The Animas Valley and Las Cruces areas have the most significant geothermal potential of the areas studied. The Truth or Consequences and Albuquerque areas need further study. The San Ysidro and Abiquiu-Ojo Caliente regions have less significant geothermal potential. 78 figs., 16 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012Litho.152...84W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012Litho.152...84W"><span>Open <span class="hlt">System</span> evolution of peralkaline trachyte and phonolite from the Suswa volcano, Kenya <span class="hlt">rift</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>White, John Charles; Espejel-García, Vanessa V.; Anthony, Elizabeth Y.; Omenda, Peter</p> <p>2012-11-01</p> <p>Suswa is the southernmost volcanic center in the Central Kenya Peralkaline Province (CKPP) and represents the only salic center to have erupted significant volumes of peralkaline silica-undersaturated lavas and tuffs (trachyte, nepheline trachyte and phonolite). The eruptive products of Suswa can be clearly divided into two series, which correspond closely to the volcano's eruptive history. The earlier series (C1) includes lavas and tuffs that built the initial shield volcano (pre-caldera, unit S1) and erupted during the first caldera collapse (syn-caldera, units S2-S5); these rocks are dominated by peralkaline, silica-saturated to mildly under-saturated trachyte. The later series (C2) includes lavas and tuffs that erupted within the caldera structure following the initial collapse (post-caldera, units S6-S7) and during the creation of a second smaller, nested caldera and central "island block" (ring trench group, RTG, unit S8); these rocks are dominated by peralkaline phonolite. In this study, we combine mineralogical evidence with the results of major-element, trace-element, and thermodynamic modelling to propose a complex model for the origin of the Suswa volcano. From these results we conclude that C1 is the result of protracted fractional crystallization of a fairly "dry" alkali basalt (< 1 wt.% H2O) under relatively high pressure (400 MPa) and low oxygen fugacity (FMQ to FMQ-1). Although C1 appears to be primarily the result of closed <span class="hlt">system</span> processes, a variety of open <span class="hlt">system</span> processes are responsible for C2. We propose that crystallization of C1 trachyte resulted in the formation of a syenitic residue, which was assimilated (Ma/Mc = 0.1) during a later stage of recharge and differentiation of alkali basalt to produce post-caldera ne-trachyte. Post-caldera (S6-7) phonolites were in turn the result of fractional crystallization of this ne-trachyte. RTG phonolites, however, are the result of feldspar resorption prompted perhaps by magma recharge as evidenced</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....10300H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....10300H"><span>The Thaumasia "<span class="hlt">rift</span>", Mars - is it a <span class="hlt">rift</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hauber, E.; Kronberg, P.</p> <p>2003-04-01</p> <p>We describe the morphology of a large and complex graben structure in western Thaumasia which was often ascribed to <span class="hlt">rifting</span> by previous authors (the Thaumasia "<span class="hlt">rift</span>" or TR). We consider possible fault geometries, determine extension, and discuss shortly possible models for its origin. The TR is characterized by a strong (half)graben asymmetry. The master fault <span class="hlt">system</span> changes from the western border in the northern part to the eastern border in the southern part (at ˜21^oS). Several profiles across the TR display features that might indicate a listric master fault, including an overall halfgraben geometry, tilted blocks, and a curvature of the hanging wall which is characteristic of a rollover. For a listric fault, the depth D to a detachment can be determined from the surficial fault dip (α), the tilt of the graben floor (θ), and the vertical offset (d). We measure a scarp height d of ˜2000 m and floor tilts θ between 0.9^o and 2.7^o. For α = 60^o, we obtain values of D between ˜33 km and ˜67 km (θ = 2.0^o and 1.0^o). Interestingly, these values correspond very well with recent estimations of the thickness of the elastic lithosphere T_e in S-Tharsis, as given by Zuber et al. (2000): Valles Marineris ˜60 km, Solis Planum ˜35 km. A listric W-dipping master fault in the middle and southern part of the TR might indicate gravitational gliding of an unstable part of the outward verging fold-and-thrust plateau margin towards W, i.e., toward the foreland of Thaumasia. However, slip along planar faults can also produce tilted graben floors and hanging wall flexure, so the observed morphology does not allow any firm statement about the fault geometry. Extension (assuming planar fault planes) was determined using the vertical displacement at faults. In the N, most of the extension occurred along a few major faults. In the S, it has been distributed among many smaller faults. Extension is 0.5 to 4.5 km (strain 1 to 3%). This is much less than 10 km, as previously</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T43A4678A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T43A4678A"><span>Radial Anisotropy beneath the Main Ethiopian <span class="hlt">Rift</span> and Afar Depression</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Accardo, N. J.; Gaherty, J. B.; Jin, G.; Shillington, D. J.</p> <p>2014-12-01</p> <p>The Main Ethiopian <span class="hlt">Rift</span> (MER) and Afar uniquely capture the <span class="hlt">final</span> stages of transition from continental <span class="hlt">rifting</span> in the broader East African <span class="hlt">Rift</span> <span class="hlt">System</span> to incipient seafloor spreading above a mantle hotspot. Studies of the region increasingly point to magmatism as a controlling factor on continental extension. However, the character and depth extent of these melt products remain contentious. Radial anisotropy derived from surface waves provides a unique diagnostic constraint on the presence of oriented melt pockets versus broader oriented anisotropic fabrics. This study investigates the thermal and radially anisotropic structure beneath the broader MER and Afar to resolve the magmatic character of the region and ultimately to understand the role of magmatism in present day <span class="hlt">rift</span> development. We utilize 104 stations from 4 collocated arrays in the MER/Afar region to constrain radial anisotropy within the upper mantle via the inversion of Love- and Rayleigh-wave observations between 25 and 100 s period. We employ a multi-channel cross-correlation algorithm to obtain inter-station phase and amplitude information. The multi-channel phase observations are inverted for dynamic phase velocity across the array, which are then corrected for focusing and multipathing using the amplitude observations via Helmholtz tomography. We jointly invert Love- and Rayleigh-wave structural phase velocity measurements employing crustal constraints from co-located active source experiments to obtain estimates of Vsv and Vsh between 50 - 170 km depth. Preliminary results readily reveal the distinct shear velocity structure beneath the MER and Afar. Within the MER, shear velocity structure suggests pronounced low velocities accompanied by strong anisotropy between 80 - 140 km depth beneath the western Ethiopian plateau and <span class="hlt">rift</span> valley. Within Afar, shear velocity structure is more varied with the slowest velocities found at shallow depths (less than 70 km depth), accompanied by weak</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011Tecto..30.1002D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011Tecto..30.1002D"><span>Young <span class="hlt">rift</span> kinematics in the Tadjoura <span class="hlt">rift</span>, western Gulf of Aden, Republic of Djibouti</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Daoud, Mohamed A.; Le Gall, Bernard; Maury, René C.; Rolet, JoëL.; Huchon, Philippe; Guillou, Hervé</p> <p>2011-02-01</p> <p>The Tadjoura <span class="hlt">rift</span> forms the westernmost edge of the westerly propagating Sheba ridge, between Arabia and Somalia, as it enters into the Afar depression. From structural and remote sensing data sets, the Tadjoura <span class="hlt">rift</span> is interpreted as an asymmetrical south facing half-graben, about 40 km wide, dominated by a large boundary fault zone to the north. It is partially filled up by the 1-3 Myr old Gulf Basalts which onlapped the older Somali Basalts along its shallower southern flexural margin. The major and trace element analysis of 78 young onshore lavas allows us to distinguish and map four distinct basaltic types, namely the Gulf, Somali, Goumarre, and Hayyabley Basalts. These results, together with radiometric age data, lead us to propose a revised volcano-stratigraphic sketch of the two exposed Tadjoura <span class="hlt">rift</span> margins and to discriminate and date several distinct fault networks of this oblique <span class="hlt">rift</span>. Morphological and statistical analyses of onshore extensional fault populations show marked changes in structural styles along-strike, in a direction parallel to the <span class="hlt">rift</span> axis. These major fault disturbances are assigned to the arrest of axial fault tip propagation against preexisting discontinuities in the NS-oriented Arta transverse zone. According to our model, the sinistral jump of <span class="hlt">rifting</span> into the Asal-Ghoubbet <span class="hlt">rift</span> segment results from structural inheritance, in contrast with the en échelon or transform mechanism of propagation that prevailed along the entire length of the Gulf of Aden extensional <span class="hlt">system</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986Tecto...5..279S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986Tecto...5..279S"><span>Continental <span class="hlt">Rifting</span> and Transform Faulting Along the Jurassic Transantarctic <span class="hlt">Rift</span>, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmidt, Dwight L.; Rowley, Peter D.</p> <p>1986-04-01</p> <p>The Transantarctic <span class="hlt">rift</span>, an extensional continental <span class="hlt">rift</span> valley, formed between East and West Antarctica during latest Early and Middle Jurassic time and is represented today by the high Transantarctic Mountains, which contain large volumes of continental flood basalt, diabase, and gabbro. Transantarctic <span class="hlt">rifting</span> marked the beginning of the breakup of Gondwanaland; it was contiguous and synchronous with continental <span class="hlt">rifting</span> between East Antarctica-India and Africa as represented by the continental basalt and diabase of Queen Maud Land and the Karroo of southern Africa. During Late Jurassic time, about 150 Ma or slightly earlier, East and West Gondwanaland separated and new oceanic crust of the earliest Indian Ocean formed between East Antarctica-India and Africa. If, as assumed, West Antarctica and South America remained fixed through a tip-to-tip join between the Antarctic Peninsula and Tierra del Fuego, then this seafloor spreading required major right-lateral transform faulting of 500 to 1000 km on the Transantarctic <span class="hlt">rift</span> <span class="hlt">system</span> between East and West Antarctica. The Transantarctic Mountains were elevated at about the same time in Late Jurassic; such uplifts are characteristic of active <span class="hlt">rift</span> margins worldwide. During Cenozoic time, extensional block faulting, independent of the Jurassic <span class="hlt">rifting</span>, further disrupted large areas of West Antarctica. During the same time, the Transantarctic Mountains were further uplifted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T51G3009F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T51G3009F"><span>Mapping Extensional Structures in the Makgadikgadi Pans, Botswana with remote sensing and aeromagnetic data: Implication for the continuation of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> in southern Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fetkovich, E. J.; Atekwana, E. A.; Abdelsalam, M. G.; Atekwana, E. A.; Katumwehe, A. B.</p> <p>2015-12-01</p> <p>We used Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) and aeromagnetic data to map extensional structures in the Makgadikgadi Pans in northeastern Botswana. These pans are a major morphological feature in Southern Africa characterized by the presence of low lying and flat topography with the highest elevation of 945 m. This topography was a result of multiple filling and desiccation of paleo-lakes that accompanied alternation of wetter and dryer climate during the Late Quaternary period. The objective of our study was to map the extent and distribution of normal faults using their morphological expression and magnetic signature, and examine their relationship with paleo-shorelines of the pans. We: (1) Created a hill shade relief map from the SRTM DEM; (2) Extracted regional NW-SE trending topographic profiles across the pans; (3) Constructed displacement profiles for major normal faults; and (4) Created tilt derivative images from the aeromagnetic data. We found that: (1) The northeastern part of the pan is dissected by three morphologically-defined NE-trending normal faults. The along strike continuity of these faults is in the range of 75 and 170 km and they are spaced at ~30 km apart from each other. (2) The topographic profiles suggest that the exposed minimum vertical displacement (EMVD), defined by poorly developed escarpments, is in the range of 0 m and 49 m. (3) The displacement profiles of the faults is characterized by maximum EMVD in the middle of the faults and that it decays towards the fault tips. These faults are also apparent in the aeromagnetic maps where they seem to displace E-W trending Karoo-age dikes. (4) At least the outer paleo-shoreline of the pans is modified by the NE-trending faults. This suggests that the faults are younger than the paleo-shorelines, which is suggested to have been developed between 500 and 100 ka. Traditionally, the southwestern extension of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> has been assigned to the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GGG....16.4344A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GGG....16.4344A"><span>Submarine and subaerial lavas in the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span>: Temporal record of shifting magma source components from the lithosphere and asthenosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aviado, Kimberly B.; Rilling-Hall, Sarah; Bryce, Julia G.; Mukasa, Samuel B.</p> <p>2015-12-01</p> <p>The petrogenesis of Cenozoic alkaline magmas in the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> (WARS) remains controversial, with competing models highlighting the roles of decompression melting due to passive <span class="hlt">rifting</span>, active plume upwelling in the asthenosphere, and flux melting of a lithospheric mantle metasomatized by subduction. In this study, seamounts sampled in the Terror <span class="hlt">Rift</span> region of the Ross Sea provide the first geochemical information from submarine lavas in the Ross Embayment in order to evaluate melting models. Together with subaerial samples from Franklin Island, Beaufort Island, and Mt. Melbourne in Northern Victoria Land (NVL), these Ross Sea lavas exhibit ocean island basalt (OIB)-like trace element signatures and isotopic affinities for the C or FOZO mantle endmember. Major-oxide compositions are consistent with the presence of multiple recycled lithologies in the mantle source region(s), including pyroxenite and volatile-rich lithologies such as amphibole-bearing, metasomatized peridotite. We interpret these observations as evidence that ongoing tectonomagmatic activity in the WARS is facilitated by melting of subduction-modified mantle generated during 550-100 Ma subduction along the paleo-Pacific margin of Gondwana. Following ingrowth of radiogenic daughter isotopes in high-µ (U/Pb) domains, Cenozoic extension triggered decompression melting of easily fusible, hydrated metasomes. This multistage magma generation model attempts to reconcile geochemical observations with increasing geophysical evidence that the broad seismic low-velocity anomaly imaged beneath West Antarctica and most of the Southern Ocean may be in part a compositional structure inherited from previous active margin tectonics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/376373','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/376373"><span>Facilities management <span class="hlt">system</span> (FMS). <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p></p> <p>1992-04-01</p> <p>The remainder of this report provides a detailed, <span class="hlt">final</span> status of Andersen Consulting`s participation in the FMS <span class="hlt">systems</span> implementation project and offers suggestions for continued FMS improvements. The report presents the following topics of discussion: (1) Summary and Status of Work (2) Recommendations for Continued Success (3) Contract Deliverables and Client Satisfaction The Summary and Status of Work section presents a detailed, <span class="hlt">final</span> status of the FMS project at the termination of Andersen`s full-time participation. This section discusses the status of each FMS sub-<span class="hlt">system</span> and of the Andersen major project deliverables. The Recommendations section offers suggestions for continued FMS success. The topics discussed include recommendations for each of the following areas: (1) End User and Business Operations (2) AISD; Development and Computer Operations (3) Software (4) Technical Platform (5) Control Procedures The Contract Deliverables and Client Satisfaction section discusses feedback received from Johnson Controls management and FMS <span class="hlt">system</span> users. The report also addresses Andersen`s observations from the feedback.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/376401','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/376401"><span>Facilities management <span class="hlt">system</span> (FMS). <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p></p> <p>1992-04-01</p> <p>This report provides a detailed, <span class="hlt">final</span> status of Andersen Consulting`s participation in the Facilities Management <span class="hlt">System</span> (FMS) implementation project under contract with Los Alamos National Laboratory (LANL) and offers suggestions for continued FMS improvements. The report presents the following topics of discussion: (1) summary and status of work (2) recommendations for continued success (3) contract deliverables and client satisfaction. The Summary and Status of Work section presents a detailed, <span class="hlt">final</span> status of the FMS project at the termination of Andersen`s full-time participation. This section discusses the status of each FMS sub-<span class="hlt">system</span> and of the Andersen major project deliverables. The Recommendations section offers suggestions for continued FMS success. The topics discussed include recommendations for each of the following areas: (1) End User and Business Operations; (2) AISD; Development and Computer Operations; (3) Software; (4) Technical Platform; and (5) Control Procedures The Contract Deliverables and Client Satisfaction section discusses feedback received from Johnson Controls management and FMS <span class="hlt">system</span> users. The report also addresses Andersen`s observations from the feedback.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992CoMP..111...24Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992CoMP..111...24Z"><span>Four- and five-phase peridotites from a continental <span class="hlt">rift</span> <span class="hlt">system</span>: evidence for upper mantle uplift and cooling at the Ross Sea margin (Antarctica)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zipfel, J.; Wörner, G.</p> <p>1992-06-01</p> <p>Upper mantle plagioclase+spinel- and spinel-peridotite xenoliths occur in basanitic and tephritic lavas of the 2.7 my to Recent Mt. Melbourne Volcanic Field (Antarctica). This field belongs to the Cenozoic McMurdo volcanic group which is located between the deep western trough of the Ross Sea <span class="hlt">rift</span> <span class="hlt">system</span> and the uplifted <span class="hlt">rift</span> shoulder of the Transantarctic Mountains. Our samples cover the transition zone between <span class="hlt">rift</span> and shoulder. We examined texture and composition of plagioclase+spinel and normal spinel peridotites and determined temperatures and pressures of formation using the internally consistent Ca-ol/cpx and 2px-thermobarometer of Köhler and Brey (1990) and Brey and Köhler (1990). Distinct calcium distribution patterns in olivines correspond to three different petrographic textures: type ELZ have equigranular textures, and low calcium concentrations of 60 ppm in the olivine cores which are strongly zoned to 200 ppm in their rims. Type PLH are protogranular to porphyroclastic and have low and homogeneous calcium contents in the range of 120 to 200 ppm. Type EHH peridotites are equigranular and have olivines with high and homogeneous calcium values of 467 485 ppm. The application of the 2 px-thermometer give rim temperatures of 800 to 860 °C for Type ELZ, 900 to 1080 °C for type PLH and 1030 to 1050 °C for type EHH. Pressures of 13 to 17 kb calculated with the Ca-ol/epx-barometer for EHH peridotites are consistent with the Ross <span class="hlt">Rift</span> geotherm. For the other two types, this barometer yields unreasonable high pressures exceeding 30 kb for both, plagioclase-bearing and ‘normal’ spinel-peridotites. This indicates disequilibrium and continued calcium-loss from the olivines during cooling below the closure temperature for the 2 px-thermometer. Inversion of the Ca-in-olivine-barometer into a thermometer and application to core compositions of ELZ olivines (60 ppm) suggests that cooling occurred to temperatures of ca. 580 °C. Based on petrographical and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Litho.212...16T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Litho.212...16T"><span>Petrogenesis of the Ni-Cu-PGE sulfide-bearing Tamarack Intrusive Complex, Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span>, Minnesota</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Taranovic, Valentina; Ripley, Edward M.; Li, Chusi; Rossell, Dean</p> <p>2015-01-01</p> <p>The Tamarack Intrusive Complex (TIC, 1105.6 ± 1.2 Ma) in NE Minnesota, was emplaced during the early stages of the development of the Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span> (MRS, "Early Stage": 1110-1106 Ma). Country rocks of the TIC are those of the Paleoproterozoic Thomson Formation, part of the Animikie Group including sulfide-bearing metasedimentary black shale. The magmatic <span class="hlt">system</span> is composed of at least two principal mafic-ultramafic intrusive sequences: the sulfide-barren Bowl Intrusion in the south and the "dike" area intrusions in the north which host Ni-Cu-Platinum Group Elements (PGE) mineralization with up to 2.33% Ni, 1.24% Cu, 0.34 g/t Pt, 0.23 g/t Pd and 0.18 g/t Au. Two distinct intrusive units in the "dike" area are the CGO (coarse-grained olivine-bearing) Intrusion, a sub-vertical dike-like body, and the overlying sub-horizontal FGO (fine-grained olivine-bearing) Intrusion. Both intrusions comprise peridotite, feldspathic peridotite, feldspathic pyroxenite, melatroctolite and melagabbro. Massive sulfides are volumetrically minor and mainly occur as lenses emplaced into the country rocks associated with both intrusions. Semi-massive (net-textured) sulfides are distributed at the core of the CGO Intrusion, surrounded by a halo of the disseminated sulfides. Disseminated sulfides also occur in lenses along the base of the FGO Intrusion. Olivine compositions in the CGO Intrusion are between Fo89 and Fo82 and in the FGO Intrusion from Fo84 to Fo82. TIC intrusions have more primitive olivine compositions than that of olivine in the sheet-like intrusions in the Duluth Complex (below Fo70), as well as olivine from the smaller, conduit-related, Eagle and East Eagle Intrusions in Northern Michigan (Fo86 to Fo75). The FeO/MgO ratios of the CGO and FGO Intrusion parental magmas, inferred from olivine compositions, are similar to those of picritic basalts erupted during the early stages of the MRS formation. Trace element ratios differ slightly from other intrusions in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T43G..07M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T43G..07M"><span><span class="hlt">Rift</span> inheritance in orogenes: a case study from the Western Pyrenees</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Masini, E.; Manatschal, G.; Tugend, J.; Kusznir, N. J.; Flament, J.</p> <p>2012-12-01</p> <p> detachment <span class="hlt">system</span> separates the stable Iberian continental crust to the south from the hyper-extended domain to the north defining a crustal neck. The second detachment <span class="hlt">system</span>, further to the north, exhumed mid-crustal and mantle material to the seafloor front of the upper plate. Both <span class="hlt">systems</span> are overlain by supra-detachment basins. By comparison of cross-basin dip sections, the west to east gradation from weakly to strongly reactivated sections, reactivation modalities through the <span class="hlt">rifted</span> domain can be described. We show that most of the convergence is accommodated by the inversion of the two <span class="hlt">rift</span> structures of the lower plate in two stages: 1) An early under-thrusting of the northern hyper-extended domain beneath Europe along the northern detachment <span class="hlt">system</span>. Sediments were wedged, folded and thrust both north- and southward (thin-skin); 2) the northern structure locks and implies the southward migration of shortening. The southern crustal neck is reactivated leading to frontal nappe-stacking forming the Pyrenean high chain (thick-skin). Using the Rifter® kinematic modeller, we show that this evolution can be computed through isostatically equilibrated crustal sections. These results suggest that the Pyrenees can serve as an example of how a complex <span class="hlt">rift</span> architecture strongly controls the style and the timing of orogeny to <span class="hlt">finally</span> impacts the architecture of collisional orogenes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.T11B1865F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.T11B1865F"><span>Low-Temperature Constraints on the Evolution of Metamorphic Core Complexes of the Woodlark <span class="hlt">Rift</span> <span class="hlt">System</span>, Southeastern Papua New Guinea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fitzgerald, P. G.; Baldwin, S. L.; Miller, S. R.; Perry, S. E.; Webb, L. E.; Little, T. A.</p> <p>2008-12-01</p> <p>Subduction of the Woodlark microplate at the New Britain trench is driving seafloor spreading in the Woodlark Basin and, to the west of the basin, extension of continental crust in the Woodlark <span class="hlt">rift</span>. Seafloor spreading in the Woodlark Basin initiated in the east by ~6 Ma, after which it has propagated westward. To the west, in the Woodlark <span class="hlt">rift</span>, one of the most rapidly extending places on earth, exhumation has been locally both profound and rapid (cm/yr rates). In the NW part of the D'Entrecasteaux Islands, HP and UHP rocks have been unroofed from depths ≥90 km in the last 2-8 Ma. As part of a multidisciplinary study to understand the tectonic evolution of this region and to constrain how <span class="hlt">rifting</span> is exhuming the world's youngest HP/UHP rocks, low temperature thermochronology is being applied to the metamorphic core complexes of the D'Entrecasteaux Islands, as well as to continental fragments along the <span class="hlt">rifted</span> conjugate margins of the oceanic Woodlark Basin farther to the east. Within the Woodlark Basin and Woodlark <span class="hlt">rift</span>, apatite fission track (AFT) ages generally decrease from east to west, from ~7.5 Ma in the lower plate of the Misima metamorphic core complex, to ~3 Ma at Moresby Seamount, to between ca. 1.5 and 0.5 Ma in the D'Entrecasteaux Islands. Precision of AFT ages is poor because of low [U] and hence very few tracks are present. There is considerable variation amongst apatite (U-Th)/He (AHe) single-grain ages but not with respect to [eU], indicating that the radiation damage trapping model is likely not responsible for the observed single grain age distribution. Because of the extremely rapid cooling, anomalous older apparent AHe ages are likely due to external 4He implantation from adjacent minerals. We report ranges of minimum AHe ages as these have been shown to be reliably closer to actual AHe ages. AHe single grain ages decrease from east to west, from 3-6 Ma at Misima Island, although AHe ages may be younger on the western end of the island, to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24066364','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24066364"><span>Unique device identification <span class="hlt">system</span>. <span class="hlt">Final</span> rule.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p></p> <p>2013-09-24</p> <p>The Food and Drug Administration (FDA) is issuing a <span class="hlt">final</span> rule to establish a <span class="hlt">system</span> to adequately identify devices through distribution and use. This rule requires the label of medical devices to include a unique device identifier (UDI), except where the rule provides for an exception or alternative placement. The labeler must submit product information concerning devices to FDA's Global Unique Device Identification Database (GUDID), unless subject to an exception or alternative. The <span class="hlt">system</span> established by this rule requires the label and device package of each medical device to include a UDI and requires that each UDI be provided in a plain-text version and in a form that uses automatic identification and data capture (AIDC) technology. The UDI will be required to be directly marked on the device itself if the device is intended to be used more than once and intended to be reprocessed before each use.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6919502','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6919502"><span>Jade data transcription <span class="hlt">system</span> <span class="hlt">final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Eaton, R.; Iskra, M.; McLean, J. . Advanced Technology Div.)</p> <p>1990-07-25</p> <p>The OWL sensor, which is used in conjunction with the Jade program, generates a tremendous volume of data during normal field operations. Historically, the dissemination of this data to analysts has been slowed by difficulties in transcribing to a widely readable media and format. TRW, under contract from Lawrence Livermore National Laboratory, was tasked by Defense Advanced Research Projects Agency (DARPA) with finding an improved method of transcribing the Jade experimental data. During the period of performance on this contract TRW helped to guide the development and operation of an improved transcription <span class="hlt">system</span>. This <span class="hlt">final</span> report summarizes the work performed, and provides a written record of information which may be helpful to future users of the newly developed data transcription <span class="hlt">system</span>. 4 figs.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140000469','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140000469"><span><span class="hlt">Final</span> Report - Regulatory Considerations for Adaptive <span class="hlt">Systems</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilkinson, Chris; Lynch, Jonathan; Bharadwaj, Raj</p> <p>2013-01-01</p> <p>This report documents the findings of a preliminary research study into new approaches to the software design assurance of adaptive <span class="hlt">systems</span>. We suggest a methodology to overcome the software validation and verification difficulties posed by the underlying assumption of non-adaptive software in the requirementsbased- testing verification methods in RTCA/DO-178B and C. An analysis of the relevant RTCA/DO-178B and C objectives is presented showing the reasons for the difficulties that arise in showing satisfaction of the objectives and suggested additional means by which they could be satisfied. We suggest that the software design assurance problem for adaptive <span class="hlt">systems</span> is principally one of developing correct and complete high level requirements and <span class="hlt">system</span> level constraints that define the necessary <span class="hlt">system</span> functional and safety properties to assure the safe use of adaptive <span class="hlt">systems</span>. We show how analytical techniques such as model based design, mathematical modeling and formal or formal-like methods can be used to both validate the high level functional and safety requirements, establish necessary constraints and provide the verification evidence for the satisfaction of requirements and constraints that supplements conventional testing. <span class="hlt">Finally</span> the report identifies the follow-on research topics needed to implement this methodology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996E%26PSL.144..505S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996E%26PSL.144..505S"><span>Helium isotope ratios in Ethiopian <span class="hlt">Rift</span> basalts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scarsi, P.; Craig, H.</p> <p>1996-11-01</p> <p>Helium isotope ratios were measured in olivine and pyroxene phenocrysts from basalts of the Ethiopian <span class="hlt">Rift</span> Valley and Afar Depression between 6° and 15°N and 37° and 43°E. 3He/4He ratios range from 6 to 17 times the atmospheric value (RA = 1.4 × 10-6), that is, from ratios less than typical MORB (depleted mantle) helium (R/RA= 8 ± 1) to ratios similar to high-3He hotspots and to the Yellowstone hotspot (R/RA= 16.5). The high 3He/4He ratios occur all along the Ethiopian <span class="hlt">Rift</span> and well up into the Afar Depression, with a maximum value of 17.0 RA at 8°N in the <span class="hlt">Rift</span> Axis and a high value of 14.2 RA in the central Tat'Ali sector of the Afar Depression. The ratios decrease to MORB-like values near the edge of the Red Sea, and to sub-MORB ratios (5-6 RA) at the northern end of the <span class="hlt">Rift</span> (Zula Peninsula) and at the southern end, at lakes Abaya and Chamo. The Ethiopian <span class="hlt">Rift</span> provides the only continental hotspot terrain in which helium isotope ratios can be compared in detail between volcanic lavas and associated geothermal and volcanic gases, a primary motivation for this work. Comparison with our previously measured ratios in fluids and gases (range 2-15 RA) shows excellent agreement in the areas sampled for both lavas and fluids, and indicates that high-temperature volcanic fluids can be used for establishing helium isotope signatures in such terrains. The high-3He values in both fluids and basalts show that a Primitive Mantle (PM) component is required and that a Lower Mantle High-3He plume is strongly involved as a driving force in the <span class="hlt">rifting</span> process of the East African <span class="hlt">Rift</span> <span class="hlt">System</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1715136M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1715136M"><span>Volcanic field elongation, vent distribution and tectonic evolution of continental <span class="hlt">rift</span>: The Main Ethiopian <span class="hlt">Rift</span> example</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mazzarini, Francesco; Le Corvec, Nicolas; Isola, Ilaria; Favalli, Massimiliano</p> <p>2015-04-01</p> <p>Magmatism and faulting operate in continental <span class="hlt">rifts</span> and interact at a variety of scales, however their relationship is complex. The African <span class="hlt">rift</span>, being the best example for both active continental <span class="hlt">rifting</span> and magmatism, provides the ideal location to study the interplay between the two mechanisms. The Main Ethiopian <span class="hlt">Rift</span> (MER), which connects the Afar depression in the north with the Turkana depression and Kenya <span class="hlt">Rift</span> to the south, consists of two distinct <span class="hlt">systems</span> of normal faults and its floor is scattered with volcanic fields formed by tens to several hundreds monogenetic, generally basaltic, small volcanoes and composite volcanoes and small calderas. The distribution of vents defines the overall shape of the volcanic field. Previous work has shown that the distribution of volcanic vents and the shape of a field are linked to its tectonic environment and its magmatic <span class="hlt">system</span>. In order to distinguish the impact of each mechanism, we analyzed four volcanic fields located at the boundary between the central and northern MER, three of them (Debre Zeyit, Wonji and Kone) grew in the <span class="hlt">rift</span> valley and one (Akaki) on the western <span class="hlt">rift</span> shoulder. The elongation and shape of the fields were analyzed based on their vent distribution using the Principal Component Analysis (PCA), the Vent-to-Vent Distance (VVD), and the two dimensional symmetric Gaussian kernel density estimate methods. We extracted from these methods several parameters characterizing the spatial distribution of points (e.g., eccentricity (e), eigenvector index (evi), angular dispersion (Da)). These parameters allow to define at least three types of shape for volcanic fields: strong elongate (line and ellipse), bimodal/medium elongate (ellipse) and dispersed (circle) shapes. Applied to the natural example, these methods well differentiate each volcanic field. For example, the elongation of the field increases from shoulder to <span class="hlt">rift</span> axis inversely to the angular dispersion. In addition, the results show that none of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1343975','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1343975"><span><span class="hlt">Final</span> Report: Hydrogen Storage <span class="hlt">System</span> Cost Analysis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>James, Brian David; Houchins, Cassidy; Huya-Kouadio, Jennie Moton; DeSantis, Daniel A.</p> <p>2016-09-30</p> <p>The Fuel Cell Technologies Office (FCTO) has identified hydrogen storage as a key enabling technology for advancing hydrogen and fuel cell power technologies in transportation, stationary, and portable applications. Consequently, FCTO has established targets to chart the progress of developing and demonstrating viable hydrogen storage technologies for transportation and stationary applications. This cost assessment project supports the overall FCTO goals by identifying the current technology <span class="hlt">system</span> components, performance levels, and manufacturing/assembly techniques most likely to lead to the lowest <span class="hlt">system</span> storage cost. Furthermore, the project forecasts the cost of these <span class="hlt">systems</span> at a variety of annual manufacturing rates to allow comparison to the overall 2017 and “Ultimate” DOE cost targets. The cost breakdown of the <span class="hlt">system</span> components and manufacturing steps can then be used to guide future research and development (R&D) decisions. The project was led by Strategic Analysis Inc. (SA) and aided by Rajesh Ahluwalia and Thanh Hua from Argonne National Laboratory (ANL) and Lin Simpson at the National Renewable Energy Laboratory (NREL). Since SA coordinated the project activities of all three organizations, this report includes a technical description of all project activity. This report represents a summary of contract activities and findings under SA’s five year contract to the US Department of Energy (Award No. DE-EE0005253) and constitutes the “<span class="hlt">Final</span> Scientific Report” deliverable. Project publications and presentations are listed in the Appendix.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9906E..67N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9906E..67N"><span>LSST secondary mirror <span class="hlt">system</span> <span class="hlt">final</span> design</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Neill, Douglas R.; Bogan, Gregory; Zajac, Dale; Araujo, Constanza; Gressler, William J.; DeVries, Joe; Hileman, Edward A.; Lotz, Paul J.; Mills, Dave; Thomas, Sandrine; Sebring, Thomas A.; Sebag, Jacques; Warner, Mike; Wiecha, Oliver</p> <p>2016-07-01</p> <p>The Large Synoptic Survey Telescope (LSST) has a 10 degrees square field of view which is achieved through a 3 mirror optical <span class="hlt">system</span> comprised of an 8.4 meter primary, 3.5 meter secondary (M2) and a 5 meter tertiary mirror. The M2 is a 100mm thick meniscus convex asphere. The mirror surface is actively controlled by 72 axial electromechanical actuators (axial actuators). Transverse support is provided by 6 active tangential electromechanical actuators (tangent links). The <span class="hlt">final</span> design has been completed by Harris Corporation. They are also providing the fabrication, integration and testing of the mirror cell assembly, as well as the figuring of the mirror. The <span class="hlt">final</span> optical surface will be produced by ion figuring. All the actuators will experience 1 year of simulated life testing to ensure that they can withstand the rigorous demands produced by the LSST survey mission. Harris Corporation is providing optical surface metrology to demonstrate both the quality of the optical surface and the correctablility produced by the axial actuators.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70178112','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70178112"><span>Making it and breaking it in the Midwest: Continental assembly and <span class="hlt">rifting</span> from modeling of EarthScope magnetotelluric data</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bedrosian, Paul A.</p> <p>2016-01-01</p> <p>A three-dimensional lithospheric-scale resistivity model of the North American mid-continent has been estimated based upon EarthScope magnetotelluric data. Details of the resistivity model are discussed in relation to lithospheric sutures, defined primarily from aeromagnetic and geochronologic data, which record the southward growth of the Laurentian margin in the Proterozoic. The resistivity signature of the 1.1 Ga Mid-continent <span class="hlt">Rift</span> <span class="hlt">System</span> is examined in detail, in particular as relates to <span class="hlt">rift</span> geometry, extent, and segmentation. An unrecognized expanse of (concealed) Proterozoic deltaic deposits in Kansas is identified and speculated to result from axial drainage along the southwest <span class="hlt">rift</span> arm akin to the Rio Grande delta which drains multiple <span class="hlt">rift</span> basins. A prominent conductor traces out Cambrian <span class="hlt">rifting</span> in Arkansas, Missouri, Tennessee, and Kentucky; this linear conductor has not been imaged before and suggests that the Cambrian <span class="hlt">rift</span> <span class="hlt">system</span> may have been more extensive than previously thought. The highest conductivity within the mid-continent is imaged in Minnesota, Michigan, and Wisconsin where it is coincident with Paleoproterozoic metasedimentary rocks. The high conductivity is attributed to metallic sulfides, and in some cases, graphite. The former is a potential source of sulfur for multiple mineral deposits types, occurrences of which are found throughout the region. <span class="hlt">Finally</span>, the imprint left within the mantle following the 1.1 Ga <span class="hlt">rifting</span> event is examined. Variations in lithospheric mantle conductivity are observed and are interpreted to reflect variations in water content (depleted versus metasomatized mantle) imprinted upon the mantle by the Keweenawan mantle plume.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2764559','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2764559"><span><span class="hlt">Rift</span> Valley fever vaccines</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ikegami, Tetsuro; Makino, Shinji</p> <p>2009-01-01</p> <p><span class="hlt">Rift</span> Valley fever virus (RVFV), which belongs to the genus Phlebovirus, family Bunyaviridae, is a negative-stranded RNA virus carrying a tripartite RNA genome. RVFV is transmitted by mosquitoes and causes large outbreaks among ruminants and humans in Africa and the Arabian Peninsula. Human patients develop an acute febrile illness, followed by a fatal hemorrhagic fever, encephalitis or ocular diseases, whereas ruminants experience abortions during outbreak. Effective vaccination of both humans and ruminants is the best approach to control <span class="hlt">Rift</span> Valley fever. This article summarizes the development of inactivated RVFV vaccine, live attenuated vaccine, and other new generation vaccines. PMID:19837291</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/316236','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/316236"><span>Geochemistry of hypabyssal rocks of the Midcontinent <span class="hlt">Rift</span> <span class="hlt">system</span> in Minnesota, and implications for a Keweenawan magmatic ``family tree``</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jerde, E.A.</p> <p>1998-11-01</p> <p>The hypabyssal rocks associated with the Keweenawan (1.1 Ga) Midcontinent <span class="hlt">Rift</span> along the Minnesota shore of Lake Superior are a distinct suite within the rock associations of this region. These rocks are found predominantly as ophitic diabase dikes and sills of various sizes, ranging from a few meters to several hundred meters across. Chilled margins were sampled and analyzed by neutron activation analysis and microprobe fused-bead techniques for bulk chemistry. Mineral compositions were obtained by electron microprobe. Variations in composition were found that are consistent with fractionation. Major-element modeling of fractionation indicates that the majority of the hypabyssal rocks formed at moderate pressures ({approximately}6 kbar), although a number show evidence of fractionation at near-surface levels, and some deeper ({approximately}10 kbar). Resorption features seen in plagioclase phenocrysts are evidence for magmatic evolution at varying levels in the crust. It is possible to relate the varied hypabyssal rocks to a single primary parent through polybaric fractionation. This parent is a high-Al primitive olivine tholeiite--a magma composition common among the volcanic rocks associated with the Midcontinent <span class="hlt">Rift</span>. Trace-element modeling with this same parent composition yields results consistent with the formation of some hypabyssal rocks as products of a periodically tapped and replenished, constantly fractionating magma chamber, which can decouple the behavior of major and trace elements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140006387','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140006387"><span>Multi-Point Combustion <span class="hlt">System</span>: <span class="hlt">Final</span> Report</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goeke, Jerry; Pack, Spencer; Zink, Gregory; Ryon, Jason</p> <p>2014-01-01</p> <p>A low-NOx emission combustor concept has been developed for NASA's Environmentally Responsible Aircraft (ERA) program to meet N+2 emissions goals for a 70,000 lb thrust engine application. These goals include 75 percent reduction of LTO NOx from CAEP6 standards without increasing CO, UHC, or smoke from that of current state of the art. An additional key factor in this work is to improve lean combustion stability over that of previous work performed on similar technology in the early 2000s. The purpose of this paper is to present the <span class="hlt">final</span> report for the NASA contract. This work included the design, analysis, and test of a multi-point combustion <span class="hlt">system</span>. All design work was based on the results of Computational Fluid Dynamics modeling with the end results tested on a medium pressure combustion rig at the UC and a medium pressure combustion rig at GRC. The theories behind the designs, results of analysis, and experimental test data will be discussed in this report. The combustion <span class="hlt">system</span> consists of five radially staged rows of injectors, where ten small scale injectors are used in place of a single traditional nozzle. Major accomplishments of the current work include the design of a Multipoint Lean Direct Injection (MLDI) array and associated air blast and pilot fuel injectors, which is expected to meet or exceed the goal of a 75 percent reduction in LTO NOx from CAEP6 standards. This design incorporates a reduced number of injectors over previous multipoint designs, simplified and lightweight components, and a very compact combustor section. Additional outcomes of the program are validation that the design of these combustion <span class="hlt">systems</span> can be aided by the use of Computational Fluid Dynamics to predict and reduce emissions. Furthermore, the staging of fuel through the individually controlled radially staged injector rows successfully demonstrated improved low power operability as well as improvements in emissions over previous multipoint designs. Additional comparison</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.7480N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.7480N"><span>InSAR and GPS measurements along the Kivu segment of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> during the 2011-2012 Nyamulagira volcanic eruption.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nobile, Adriano; Geirsson, Halldor; Smets, Benoît; d'Oreye, Nicolas; Kervyn, François</p> <p>2016-04-01</p> <p>Along the East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS), magma intrusions represent a major component in continental <span class="hlt">rifting</span>. When these intrusions reach the surface, they cause volcanic eruptions. This is the case of the last flank eruption of Nyamulagira, which occurred from November 6 2011 to April 2012. Nyamulagira is an active shield volcano with a central caldera, located in the eastern part of the Democratic Republic of Congo, along the Kivu segment of the East African <span class="hlt">Rift</span> <span class="hlt">System</span>. From 1948 to 2012, Nyamulagira mostly showed a particular eruptive cycle with 1) classical short-lived (i.e., 20-30 days) flank eruptions, sometimes accompanied with intracrateral activity, which occurred every 1-4 years on average, and 2) less frequent long-lived (i.e., several months) eruptions usually emitting larger volumes of lava that take place at larger distance (>8 km) from the central caldera. The 2011-2012 Nyamulagira eruption is of that second type. Here we used InSAR data from different satellite (Envisat, Cosmo SkyMed, TerraSAR-X and RADARSAT) to measure pre-, co and post-eruptive ground displacement associated with the Nyamulagira 2011-2012 eruption. Results suggest that a magma intrusion preceded by two days the eruption. This intrusion corresponded to the migration of magma from a shallow reservoir (~3km) below the caldera to the two eruptive fissures located ~11 km ENE of the central edifice. Available seismic data are in agreement with InSAR results showing increased seismic activity since November 4 2011, with long- and short-period earthquakes swarms. Using analytical models we invert the measured ground displacements during the first co-eruptive month to evaluate the deformation source parameters and the mechanism of magma emplacement for this eruption. GPS data from permanent stations in the KivuGNet network are used to constrain the temporal evolution of the eruption and evaluate far-field deformation, while the InSAR data is more sensitive to the near-field deformation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5067589','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5067589"><span>Depositional <span class="hlt">systems</span> in the lower Cretaceous Morro Do Chaves and Coqueiro Seco formations, and their relationship to petroleum accumulations, middle <span class="hlt">rift</span> sequence, Sergipe-Alagoas Basin, Brazil</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>de Figueiredo, A.M.F.</p> <p>1981-01-01</p> <p>In the Sergipe-Alagoas Basin, northeast coast of Brazil, the Lower Cretaceous lacustrine, middle <span class="hlt">rift</span> sequence is composed of the Morro do Chaves and Coqueiro Seco Formations. Subsurface analysis permitted recognition and mapping of four principal types of depositional environments: Morro do Chaves carbonate platform, and Coqueiro Seco fluvial-deltaic, fan delta, and slope <span class="hlt">systems</span>. Morro do Chaves lacustrine carbonate sediments were deposited in positive areas flanking the principal point sources (rivers), and are composed of high energy limestones. Contemporaneous deep-water euxinic and bituminous lacustrine shales were deposited under starved basin conditions. Sublacustrine canyon excavation attested to the presence of a destructional slope episode. Coqueiro Seco fluvial-deltaic and fan delta facies display high sand/shale ratios and blocky to massive E-log patterns; slope facies display serrate to digitate E-log patterns and is less sandy. Delta plain channel-fill facies and coarse-grained meanderbelt fluvial facies are dominant in fluvial-deltaic <span class="hlt">systems</span> of the Alagoas Sub-basin; and proximal to medial conglomerates and coarse conglomeratic sandstones are dominant facies in fan delta <span class="hlt">systems</span> of the Rio Sao Francisco Sub-basin. Slope facies are composed of sublacustrine fans formed by fine- to medium-grained sandstones enveloped by subbituminous shales, and lacustrine limestones. Coqueiro Seco coarse clastic <span class="hlt">systems</span> prograded across the basin and buried Morro do Chaves carbonate platforms in response to cyclic tectonic pulses related to <span class="hlt">rift</span> development. Evaluation of petroleum occurrences in relationship to defined depositional <span class="hlt">systems</span> permitted recognition of several types of plays characterized by unique structural and stratigraphic relationships exhibited by reservoirs, source beds and structure. The Coqueiro Seco slope play, formed by updip pinchout of turbidite fans, is judged the most promising in the sequence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.8575B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.8575B"><span>Structural inheritance, segmentation, and <span class="hlt">rift</span> localization in the Gulf of Aden oblique <span class="hlt">rift</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bellahsen, Nicolas; Leroy, Sylvie; Autin, Julia; d'Acremont, Elia; Razin, Philippe; Husson, Laurent; Pik, Raphael; Watremez, Louise; Baurion, Celine; Beslier, Marie-Odile; Khanbari, Khaled; Ahmed, Abdulhakim</p> <p>2013-04-01</p> <p> well as third order ones that initiated after the onset of oceanic spreading). In the East, the second and third order segmentation is less pronounced as both the OCT and ridge segments are sub-perpendicular to the divergence. During post-<span class="hlt">rift</span> times, plate reorganization led to oceanic propagator development and second/third transform F.Z. migration along with deformation and vertical movements and normal displacement along the first order transform F.Z. <span class="hlt">Finally</span>, during Quaternary times, the evolving boundary conditions of the Arabian plate probably also induced vertical movements along the margins.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.430....1Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.430....1Y"><span>Seismic anisotropy beneath the incipient Okavango <span class="hlt">rift</span>: Implications for <span class="hlt">rifting</span> initiation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Youqiang; Gao, Stephen S.; Moidaki, Moikwathai; Reed, Cory A.; Liu, Kelly H.</p> <p>2015-11-01</p> <p>This study represents the first shear-wave splitting investigation of the Okavango <span class="hlt">rift</span> zone (ORZ), an incipient continental <span class="hlt">rift</span> belonging to the East African <span class="hlt">rift</span> <span class="hlt">system</span> in northern Botswana. Analysis of broadband seismic data recorded along a 750 km long profile of 22 stations traversing the ORZ and adjacent Congo and Kalahari cratons and several Precambrian orogenic zones reveals dominantly NE-SW fast orientations, which are parallel to both the absolute plate motion direction (based on the NNR-NUVEL-1A model) and the trend of most tectonic boundaries, including that of the ORZ. Spatial coherence analysis of the splitting parameters and correspondence between the observed fast orientations and the trend of tectonic features indicate that the main source of observed anisotropy is most likely in the upper asthenosphere, probably due to simple shear associated with the relative movement of the lithosphere against the asthenosphere. The presence of consistently <span class="hlt">rift</span>-parallel fast orientations and normal splitting times in the ORZ and most parts of southern Africa implies that neither an upper mantle plume nor small-scale convection is the dominant source for <span class="hlt">rift</span> initiation and development. The first shear-wave splitting measurements in the vicinity of the ORZ favor a model in which continental <span class="hlt">rifting</span> develops in response to intra-plate relative movement of continental blocks along zones of weakness produced by ancient tectonic events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=North+AND+American+AND+plate&id=EJ394260','ERIC'); return false;" href="http://eric.ed.gov/?q=North+AND+American+AND+plate&id=EJ394260"><span>Volcanism at <span class="hlt">Rifts</span>.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>White, Robert S.; McKenzie, Dan P.</p> <p>1989-01-01</p> <p>Investigates the nature of catastrophic volcanism and the <span class="hlt">rifting</span> process. Describes two kinds of evidence: quantitative descriptions of rock melting and a wide range of observations. Discusses examples of continent growth in the North Atlantic, India and the Seychelles islands, and the South Atlantic. (YP)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19810063492&hterms=continental+divide&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dcontinental%2Bdivide','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19810063492&hterms=continental+divide&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dcontinental%2Bdivide"><span>Continental <span class="hlt">rifting</span> - Progress and outlook</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baker, B. H.; Morgan, P.</p> <p>1981-01-01</p> <p>It is noted that in spite of the flood of new data on continental <span class="hlt">rifts</span> in the last 15 years, there is little consensus about the basic mechanisms and causes of <span class="hlt">rifting</span>. The remarkable similarities in <span class="hlt">rift</span> cross sections (shown in a figure), are considered to suggest that the anomalous lithospheric structure of <span class="hlt">rifts</span> is more dependent on lithosphere properties than the mode of <span class="hlt">rifting</span>. It is thought that there is a spectrum of <span class="hlt">rifting</span> processes for which two fundamental mechanisms can be postulated: an active mechanism, whereby thermal energy is transmitted into the lithosphere from the underlying asthenosphere, and a passive mechanism by which mechanical energy is transmitted laterally through the lithosphere as a consequence of plate interactions at a distance. In order to permit the concept of the two fundamentally different mechanisms to be tested, a tentative classification is proposed that divides <span class="hlt">rifts</span> into two basic categories: active <span class="hlt">rifting</span> and passive <span class="hlt">rifting</span>. Here, the magnitude of active <span class="hlt">rifting</span> will depend on the rate at which lithosphere moves over the thermal source, with <span class="hlt">rifts</span> being restricted to stationary or slow-moving plates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5454347','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5454347"><span>Continental <span class="hlt">rifting</span> - Progress and outlook</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Baker, B.H.; Morgan, P.</p> <p>1981-07-21</p> <p>It is noted that in spite of the flood of new data on continental <span class="hlt">rifts</span> in the last 15 years, there is little consensus about the basic mechanisms and causes of <span class="hlt">rifting</span>. The remarkable similarities in <span class="hlt">rift</span> cross sections (shown in a figure), are considered to suggest that the anomalous lithospheric structure of <span class="hlt">rifts</span> is more dependent on lithosphere properties than the mode of <span class="hlt">rifting</span>. It is thought that there is a spectrum of <span class="hlt">rifting</span> processes for which two fundamental mechanisms can be postulated: an active mechanism, whereby thermal energy is transmitted into the lithosphere from the underlying asthenosphere, and a passive mechanism by which mechanical energy is transmitted laterally through the lithosphere as a consequence of plate interactions at a distance. In order to permit the concept of the two fundamentally different mechanisms to be tested, a tentative classification is proposed that divides <span class="hlt">rifts</span> into two basic categories: active <span class="hlt">rifting</span> and passive <span class="hlt">rifting</span>. Here, the magnitude of active <span class="hlt">rifting</span> will depend on the rate at which lithosphere moves over the thermal source, with <span class="hlt">rifts</span> being restricted to stationary or slow-moving plates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012DPS....4450508A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012DPS....4450508A"><span><span class="hlt">Final</span> Origin of the Saturn <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Asphaug, Erik; Reufer, A.</p> <p>2012-10-01</p> <p>Saturn’s middle-sized moons (MSMs) are of diverse geology and composition, totaling 4.4% of the <span class="hlt">system</span> mass. The rest is Titan, with more mass per planet than Jupiter’s satellites combined. Jupiter has four large satellites with 99.998% of the <span class="hlt">system</span> mass, and no MSMs. Models to explain the discrepancy exist (e.g. Canup 2010; Mosqueira et al. 2010; Charnoz et al. 2011) but have important challenges. We introduce a new hypothesis, in which Saturn starts with a comparable family of major satellites (Ogihara and Ida 2012). These satellites underwent a <span class="hlt">final</span> sequence of mergers, each occurring at a certain distance from Saturn. Hydrocode simulations show that galilean satellite mergers can liberate ice-rich spiral arms, mostly from the outer layers of the smaller of the accreting pair. These arms gravitate into clumps 100-1000 km diameter that resemble Saturn’s MSMs in diverse composition and other major aspects. Accordingly, a sequence of mergers (ultimately forming Titan) could leave behind populations of MSMs at a couple of formative distances, explaining their wide distribution in semimajor axis. However, MSMs on orbits that cross that of the merged body are rapidly accumulated unless scattered by resonant interactions, or circularized by mutual collisions, or both. Scattering is likely for the first mergers that take place in the presence of other resonant major satellites. Lastly, we consider that the remarkable geophysical and dynamical vigor of Titan and the MSMs might be explained if the proposed sequence of mergers happened late, triggered by impulsive giant planet migration (Morbidelli et al. 2009). The dynamical scenario requires detailed study, and we focus on analysis of the binary collisions. By analysis of the hydrocode models, we relate the provenance of the MSMs to their geophysical aspects (Thomas et al. 2010), and consider the geophysical, thermal and dynamical implications of this hypothesis for Titan’s origin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1815100P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1815100P"><span>A numerical modelling approach to investigate the surface processes response to normal fault growth in multi-<span class="hlt">rift</span> settings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pechlivanidou, Sofia; Cowie, Patience; Finch, Emma; Gawthorpe, Robert; Attal, Mikael</p> <p>2016-04-01</p> <p>This study uses a numerical modelling approach to explore structural controls on erosional/depositional <span class="hlt">systems</span> within <span class="hlt">rifts</span> that are characterized by complex multiphase extensional histories. Multiphase-<span class="hlt">rift</span> related topography is generated by a 3D discrete element model (Finch et al., Basin Res., 2004) of normal fault growth and is used to drive the landscape evolution model CHILD (Tucker et al., Comput. Geosci., 2001). Fault populations develop spontaneously in the discrete element model and grow by both tip propagation and segment linkage. We conduct a series of experiments to simulate the evolution of the landscape (55x40 km) produced by two extensional phases that differ in the direction and in the amount of extension. In order to isolate the effects of fault propagation on the drainage network development, we conduct experiments where uplift/subsidence rates vary both in space and time as the fault array evolves and compare these results with experiments using a fixed fault array geometry with uplift rate/subsidence rates that vary only spatially. In many cases, areas of sediment deposition become uplifted and vise-versa due to complex elevation changes with respect to sea level as the fault array develops. These changes from subaerial (erosional) to submarine (depositional) processes have implications for sediment volumes and sediment caliber as well as for the sediment routing <span class="hlt">systems</span> across the <span class="hlt">rift</span>. We also explore the consequences of changing the angle between the two phases of extension on the depositional <span class="hlt">systems</span> and we make a comparison with single-phase <span class="hlt">rift</span> <span class="hlt">systems</span>. <span class="hlt">Finally</span>, we discuss the controls of different erodibilities on sediment supply and detachment-limited versus transport-limited end-member models for river erosion. Our results provide insights into the nature and distribution of sediment source areas and the sediment routing in <span class="hlt">rift</span> <span class="hlt">systems</span> where pre-existing <span class="hlt">rift</span> topography and normal fault growth exert a fundamental control on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.4444B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.4444B"><span>Fault Orientations at Obliquely <span class="hlt">Rifted</span> Margins: Where? When? Why?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brune, Sascha</p> <p>2015-04-01</p> <p> setup is very simple (horizontally layered, no inherited faults, constant extension velocity and direction), its evolution exhibits a variety of fault orientations that are solely caused by the three-dimensionality of oblique <span class="hlt">rift</span> <span class="hlt">systems</span>. Allowing new insights on fault patterns of the proximal and distal margins, the model shows that individual fault populations are activated in a characteristic multi-phase evolution driven by lateral density variations of the evolving <span class="hlt">rift</span> <span class="hlt">system</span>. Moreover, the model depicts strain partitioning between <span class="hlt">rift</span>-parallel and <span class="hlt">rift</span>-perpendicular far-field velocity components that are accommodated by strike-slip faults in the <span class="hlt">rift</span> centre and normal faults at the <span class="hlt">rift</span> sides, respectively. Oblique extensional <span class="hlt">systems</span> worldwide differ in many aspects and clearly one suit of models cannot explain all <span class="hlt">rifted</span> margin structures at the same time. However, the distinct pattern of fault populations discussed in this study and their sequence of activity compares very well to previous studies of the Gulf of Aden and holds implications for many other <span class="hlt">rifted</span> margins worldwide. Note that in nature, the resulting stress and fault pattern will also be affected by inherited heterogeneities, surface processes, as well as melting and dyke dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.2376L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.2376L"><span>New insights into continental <span class="hlt">rifting</span> from a damage rheology modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lyakhovsky, Vladimir; Segev, Amit; Weinberger, Ram; Schattner, Uri</p> <p>2010-05-01</p> <p>Previous studies have discussed how tectonic processes could produce relative tension to initiate and propagate <span class="hlt">rift</span> zones and estimated the magnitude of the <span class="hlt">rift</span>-driving forces. Both analytic and semi-analytic models as well as numerical simulations assume that the tectonic force required to initiate <span class="hlt">rifting</span> is available. However, Buck (2004, 2006) estimated the minimum tectonic force to allow passive <span class="hlt">rifting</span> and concluded that the available forces are probably not large enough for <span class="hlt">rifting</span> of thick and strong lithosphere in the absence of basaltic magmatism (the "Tectonic Force" Paradox). The integral of the yielding stress needed for <span class="hlt">rifting</span> over the thickness of the normal or thicker continental lithosphere are well above the available tectonic forces and tectonic <span class="hlt">rifting</span> cannot happen (Buck, 2006). This conclusion is based on the assumption that the tectonic stress has to overcome simultaneously the yielding stress over the whole lithosphere thickness and ignore gradual weakening of the brittle rocks under long-term loading. In this study we demonstrate that the <span class="hlt">rifting</span> process under moderate tectonic stretching is feasible due to gradual weakening and "long-term memory" of the heavily fractured brittle rocks, which makes it significantly weaker than the surrounding intact rock. This process provides a possible solution for the tectonic force paradox. We address these questions utilizing 3-D lithosphere-scale numerical simulations of the plate motion and faulting process base on the damage mechanics. The 3-D modeled volume consists of three main lithospheric layers: an upper layer of weak sediments, middle layer of crystalline crust and lower layer of the lithosphere mantle. Results of the modeling demonstrate gradual formation of the <span class="hlt">rift</span> zone in the continental lithosphere with the flat layered structure. Successive formation of the <span class="hlt">rift</span> <span class="hlt">system</span> and associated seismicity pattern strongly depend not only on the applied tectonic force, but also on the healing</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813335R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813335R"><span>The <span class="hlt">rift</span> to drift evolution of the South China Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ranero, Cesar R.; Cameselle, Alejandra; Franke, Dieter; Barckhausen, Udo</p> <p>2016-04-01</p> <p>Re-processing with modern algorithms of multichannel seismic reflection records from the South China Sea provide novel images on the crustal structure of the continental margin and its boundary zone with the oceanic crust (COB). The selected re-processed seismic lines strike perpendicular to the margins' trend and cross the entire basin, providing complementary images of conjugated <span class="hlt">rift</span> segments of the NW, SW, and E sub-basins. Re-processed sections image the post-<span class="hlt">rift</span> and syn-<span class="hlt">rift</span> sediment, and fault-bounded basement blocks, often also intra-crustal fault reflections that together provide detailed information of the tectonic structural style during <span class="hlt">rifting</span>. Further, the largest imaging improvement has been obtained in the delineation of -very often- clear fairly continuous reflections from the crust-mantle boundary across the continental margin into the oceanic crust. The images show how crustal thickness and structure change in parallel to changes in the tectonic style of the deformation during the evolution of the <span class="hlt">rift</span>. The interpreted COB occurs in regions where the tectonic style displays the most noticeable changes from segments where extension is dominated by normal faulting to segments where faulting is comparatively minor and the crust shows fairly gentle lateral thickness variations; these latter segments are interpreted as oceanic crust. The identification of the continental and oceanic tectonic domains permits to study the along-strike evolution in <span class="hlt">rifting</span> processes and <span class="hlt">rift</span> segmentation. Also, the comparison of the tectonic structure of the conjugated flanks of the continental <span class="hlt">rift</span> across the ocean basins is used to understand the last stages of <span class="hlt">rifting</span> and the relative importance of tectonic extension and magmatism in <span class="hlt">final</span> break up and spreading initiation. Although there is ample evidence of important volcanism in the images, with some spectacular large conical volcanoes formed over continental crust and numerous sill-like reflections in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.T43A1976M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.T43A1976M"><span>Forensic investigation of <span class="hlt">rift</span>-to-drift transitions and volcanic <span class="hlt">rifted</span> margins birth</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meyer, R.; Hertogen, J.</p> <p>2008-12-01</p> <p>Volcanic <span class="hlt">rifted</span> margins (VRM) reflect excess magmatism generated during the <span class="hlt">rift</span>-to-drift transition of a continental <span class="hlt">rift</span> <span class="hlt">system</span> evolving into a Mid-Ocean Ridge (MOR). As a result many VRM (e.g. NAIP and CAMP) are recognized as Large Igneous Provinces (LIP). The prominent structural characteristics of VRM are Continental Flood Basalts, High-Velocity Lower Crustal bodies (HVLC) and Seaward Dipping Reflector Sequences (SDRS). However, the causes of these anomalously high eruption rates and magma volumes are presently poorly understood. Controversial issue opinions are based on two competing hypotheses: 1) Mantle plume related mechanisms where the excess magmatism results from elevated mantle temperatures; and 2) <span class="hlt">Rift</span> induced small scale convection processes causing temperature anomalies and enhancing the mantle rock flux through the melt window. Largely because of difficulties to sample oceanic basement at VRM -due to thick sediment covers- the composition of <span class="hlt">rift</span>-to-drift transition magmas is generally poorly constrained. We reviewed the geodynamic histories and magma compositions from well known VRM (e.g. NE Australia, E USA, Madagascar) and compared these data with own geochemical data from different NE Atlantic tectono-magmatic VRM zones. These comparisons point to a consistent, general VRM formation model. This model has to explain the primary observation, that geological long periods of extension have been reported -in all investigated VRM areas- prior to the breakup. Extensional far field stress looks to be the main geodynamic cause for continental breakup. Small scale convection during the late phase of a continental <span class="hlt">rift</span> <span class="hlt">system</span> is probably the key process generating excess magmatism in LIP related to <span class="hlt">rift</span>-to-drift transitions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.G34A..07P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.G34A..07P"><span>Inter-<span class="hlt">rifting</span> Deformation in an Extensional <span class="hlt">Rift</span> Segment; the Northern Volcanic Zone, Iceland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pedersen, R.; Masterlark, T.; Sigmundsson, F.; Arnadottir, T.; Feigl, K. L.</p> <p>2006-12-01</p> <p>The Northern Volcanic Zone (NVZ) in Iceland is an extensional <span class="hlt">rift</span> segment, forming a sub-aerial exposure of a part of the Mid-Atlantic ridge. The NVZ is bounded to the south by the Icelandic mantle plume, currently beneath the Vatnajökull ice cap, and to the north by the Tjörnes Fracture zone, a transform zone connecting the offset on- and offshore <span class="hlt">rift</span> segments of the Mid-Atlantic ridge. Based on geologic and tectonic mapping, the NVZ has been divided into five partly overlapping en-echelon fissure swarms, each with a central main volcanic production area. The two fissure swarms with known activity in historic time are, based on geodetic and seismic data, interpreted to have associated shallow crustal magma chambers. These central volcanoes are furthermore the only with caldera collapses associated, reflecting on the maturity of the <span class="hlt">systems</span>. A series of newly formed InSAR images of the NVZ, spanning the interval from 1993-2006, have been formed, revealing a complex interplay of several tectonic and magmatic processes. Deformation from two subsiding shallow sources appear at the sites of the known crustal magma chambers. Furthermore, subsidence is occurring at varying degrees within the associated relatively narrow fissure swarms (15-20 km). However, the horizontal plate spreading signal is not confined to the fissure <span class="hlt">systems</span>, and appears to be distributed over a much wider zone (about 100 km). This wide zone of horizontal spreading has previously been measured with campaign GPS surveys. A broad area of uplift situated about 18 km to the north of one of the subsidence centres (Krafla) suggests a deep seated pressurization source near the crust mantle boundary. Movements on previously unrecognized faults are apparent in the data, correlating well with the location of earthquake epicentres from minor seismic activity. <span class="hlt">Finally</span>, utilization of geothermal resources in the Krafla area affects the deformation fields created by magmatic and tectonic processes, further</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JSAES..29..306N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JSAES..29..306N"><span>Detrital zircon analysis from the Neoproterozoic-Cambrian sedimentary cover (Cuyania terrane), Sierra de Pie de Palo, Argentina: Evidence of a <span class="hlt">rift</span> and passive margin <span class="hlt">system</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Naipauer, M.; Vujovich, G. I.; Cingolani, C. A.; McClelland, W. C.</p> <p>2010-03-01</p> <p>Metamorphic basement and its Neoproterozoic to Cambrian cover exposed in the Sierra de Pie de Palo, a basement block of the Sierras Pampeanas in Argentina, lie within the Cuyania terrane. Detrital zircon analysis of the cover sequence which includes, in ascending order, the El Quemado, La Paz, El Desecho, and Angacos Formations of the Caucete Group indicate a Laurentian origin for the Cuyania terrane. The lower section represented by the El Quemado and La Paz Formations is interpreted as having an igneous source related to a <span class="hlt">rift</span> setting similar to that envisioned for the southern and eastern margins of Laurentia at approximately 550 Ma. The younger strata of the El Desecho Formation are correlative with the Cerro Totora Formation of the Precordillera, and both are products of <span class="hlt">rift</span> sedimentation. <span class="hlt">Finally</span>, the Angacos Formation and the correlative La Laja Formation of the Precordillera were deposited on the passive margin developed on the Cuyania terrane. The maximum depositional ages for the Caucete Group include ca. 550 Ma for the El Quemado Formation and ca. 531 Ma for the El Desecho Formation. Four different sediment sources areas were interpreted in the provenance analysis. The main source is crystalline basement dominated by early Mesoproterozoic igneous rocks related to the Granite-Rhyolite province of central and eastern Laurentia. Possible source areas for 1600 Ma metamorphic detrital zircons of the Caucete Group include the Yavapai-Mazatzal province ( ca. 1800-1600 Ma) of south-central to southwestern Laurentia. Younger Mesoproterozoic zircon is likely derived from Grenville-age medium- to high-grade metamorphic rocks and subordinate igneous rocks that form the basement of Cuyania as well as the southern Grenville province of Laurentia itself. <span class="hlt">Finally</span>, Neoproterozoic igneous zircon in the Caucete Group records different magmatic pulses along the southern Laurentian margin during opening of Iapetus and break-up of Rodinia. Northwestern Cuyania terrane</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1989GMS....51...93E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1989GMS....51...93E"><span>The GLIMPCE seismic experiment: Onshore refraction and wide-angle reflection observations from a fan line over the Lake Superior Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Epili, Duryodhan; Mereu, Robert F.</p> <p></p> <p>The 1986 GLIMPCE experiment (Great Lakes International Multidisciplinary Program for Crustal Evolution) was a combined on-ship seismic reflection and onshore seismic refraction experiment designed to determine the structure of the crust beneath the Great Lakes. The main tectonic targets of interest were the Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span>, the Grenville Front, the Penokean and Huronian Fold Belts and the Michipicoten Greenstone Belt. The source of the seismic energy came from a large air gun array fired at closely spaced intervals (50-350 m) over several long lines (150-350 km) crossing the lakes. Major participants of this experiment were the Geological Survey of Canada, the United States Geological Survey and a number of universities and research institutes on both sides of the border. The University of Western Ontario (UWO) collected data at five separate land stations using portable seismic refraction instruments. In this paper we present the results of a fan profile which was recorded from a UWO station on Michipicoten Island for the N-S line A which crossed the axis of the Lake Superior Synclinal Basin. The azimuth and distance ranges for this profile were 237 to 321 degrees and 120 to 170 km respectively. Detailed observations of the record sections show that p. is not a simple arrival but forms a rather complex pattern of irregular multiple arrivals. The wide-angle PmP reflection signals from the Moho are strong and well obilerved only for the shots fired near the ends of the line. The signals from the middle of the profile arrive relatively late and form very weak complex wave trains. These results indicate that the Moho in that area is probably greatly disrupted and gives added support to the <span class="hlt">rift</span> theory for the structure under the lake. The observations also support the results of earlier crustal studies of Lake Superior which showed that the crust under the eastern part of the lake was exceedingly thick.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24589097','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24589097"><span>A geographical information <span class="hlt">system</span>-based multicriteria evaluation to map areas at risk for <span class="hlt">Rift</span> Valley fever vector-borne transmission in Italy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tran, A; Ippoliti, C; Balenghien, T; Conte, A; Gely, M; Calistri, P; Goffredo, M; Baldet, T; Chevalier, V</p> <p>2013-11-01</p> <p><span class="hlt">Rift</span> Valley fever (RVF) is a severe mosquito-borne disease that is caused by a Phlebovirus (Bunyaviridae) and affects domestic ruminants and humans. Recently, its distribution widened, threatening Europe. The probability of the introduction and large-scale spread of <span class="hlt">Rift</span> Valley fever virus (RVFV) in Europe is low, but localized RVF outbreaks may occur in areas where populations of ruminants and potential vectors are present. In this study, we assumed the introduction of the virus into Italy and focused on the risk of vector-borne transmission of RVFV to three main European potential hosts (cattle, sheep and goats). Five main potential mosquito vectors belonging to the Culex and Aedes genera that are present in Italy were identified in a literature review. We first modelled the geographical distribution of these five species based on expert knowledge and using land cover as a proxy of mosquito presence. The mosquito distribution maps were compared with field mosquito collections from Italy to validate the model. Next, the risk of RVFV transmission was modelled using a multicriteria evaluation (MCE) approach, integrating expert knowledge and the results of a literature review on host sensitivity and vector competence, feeding behaviour and abundance. A sensitivity analysis was performed to assess the robustness of the results with respect to expert choices. The resulting maps include (i) five maps of the vector distribution, (ii) a map of suitable areas for vector-borne transmission of RVFV and (iii) a map of the risk of RVFV vector-borne transmission to sensitive hosts given a viral introduction. Good agreement was found between the modelled presence probability and the observed presence or absence of each vector species. The resulting RVF risk map highlighted strong spatial heterogeneity and could be used to target surveillance. In conclusion, the geographical information <span class="hlt">system</span> (GIS)-based MCE served as a valuable framework and a flexible tool for mapping the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Tectp.583...88L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Tectp.583...88L"><span>Geophysical evidence of Cretaceous volcanics in Logone Birni Basin (Northern Cameroon), Central Africa, and consequences for the West and Central African <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Loule, Jean-Pierre; Pospisil, Lubomil</p> <p>2013-01-01</p> <p>Detailed analyses and interpretation realized by combining existing 2D reflection seismic and Gravity/Magnetic data of the Logone Birni Basin (LBB) in the West and Central African <span class="hlt">Rift</span> <span class="hlt">System</span> (WCAS) have revealed the distribution of the main buried volcanic bodies as well as their relationships with the structural and tectonic evolution of this basin. The volcanic activity in the LBB is restricted to the Cretaceous period. Three main volcanic episodes are identified and are associated to the Neocomian, Late Albian and Cenomanian-Turonian <span class="hlt">rifting</span> phases respectively. The volcanic bodies within the Lower Cretaceous are either lying directly on basement or are mainly interbedded with the contemporaneous sediments whereas the Upper Cretaceous bodies are morphologically expressed in the forms of dykes and sills. The volcanic activity was more intense in the western region of the central LBB (Zina sub-basin) along the Cameroon-Nigeria border whereas it was scanty and scattered in the other parts of the basin. The main volcanic dykes are found on the flanks of the major faults bounding basement horsts or in crestal positions in association with syndepositional faults. Although WCAS is associated with large amount of crustal extension and minor volcanism, the intense volcanic activity observed in LBB during the Cretaceous suggests that the intrusive zone during this period was confined to the basement beneath the study area flanked respectively to the north, south and southwest by the Lake Chad, Poli and Chum triple junctions. Tensional stresses generated by this localized domal uplift accounts for most of the observed tectonic structures where major faults transected the entire lithosphere, thus providing conduits for magma migration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23163047','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23163047"><span>[<span class="hlt">Rift</span> valley fever].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Markin, V A; Pantiukhov, V B; Markov, V I; Bondarev, V P</p> <p>2012-01-01</p> <p>In the last quarter of century virus of <span class="hlt">Rift</span> valley fever (RVF) sharply extended its distribution by moving from Africa to Asia and evolving from low- to high pathogenic for humans causing severe hemorrhagic disease, practically equaling in this respect with some members ofa group of extremely dangerous pathogens. Morbidity and epidemics of RVF are analyzed. Evolution of epidemic development of the infection is examined. Necessity of development of means and methods for diagnostics, prophylaxis and therapy of RVF is underlined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70017177','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70017177"><span>Depositional and tectonic framework of the <span class="hlt">rift</span> basins of Lake Baikal from multichannel seismic data</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hutchinson, D.R.; Golmshtok, A.J.; Zonenshain, L.P.; Moore, T.C.; Scholz, C.A.; Klitgord, Kim D.</p> <p>1992-01-01</p> <p>Recent multichannel seismic reflection data from Lake Baikal, located in a large, active, continental <span class="hlt">rift</span> in central Asia, image three major stratigraphic units totalling 3.5 to 7.5 km thick in four subbasins. A major change in <span class="hlt">rift</span> deposition and faulting between the oldest and middle-<span class="hlt">rift</span> units probably corresponds to the change from slow to fast <span class="hlt">rifting</span>. A brief comparison of the basins of Lake Baikal with those of the East African <span class="hlt">rift</span> <span class="hlt">system</span> highlights differences in structural style that can be explained by differences in age and evolution of the surrounding basement rocks. -from Authors</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850029005&hterms=DALI&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DDALI','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850029005&hterms=DALI&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DDALI"><span>Venus - Volcanism and <span class="hlt">rift</span> formation in Beta Regio</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Campbell, D. B.; Harmon, J. K.; Hine, A. A.; Head, J. W.</p> <p>1984-01-01</p> <p>A new high-resolution radar image of Beta Regio, a Venus highland area, confirms the presence of a major tectonic <span class="hlt">rift</span> <span class="hlt">system</span> and associated volcanic activity. The lack of identifiable impact craters, together with the apparent superposition of the Theia Mons volcanic structure on the <span class="hlt">rift</span> <span class="hlt">system</span>, suggest that at least some of the volcanic activity occurred in relatively recent geologic time. The presence of topographically similar highland areas elsewhere on Venus (Aphrodite Terra, Dali Chasma, and Diana Chasma) suggests that <span class="hlt">rifting</span> and volcanism are significant processes on Venus.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.2456F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.2456F"><span>At the tip of a propagating <span class="hlt">rift</span> - The offshore East African <span class="hlt">Rift</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Franke, Dieter; Jokat, Wilfried; Ladage, Stefan; Stollhofen, Harald; Klimke, Jennifer; Lutz, Ruediger; Mahanjane, Stefane; Ehrhardt, Axel; Schreckenberger, Bernd</p> <p>2016-04-01</p> <p>Numerous studies have addressed various aspects of the East African <span class="hlt">Rift</span> <span class="hlt">system</span> (EARS) but surprisingly few the offshore continuation of the south-eastern branch of the <span class="hlt">rift</span> into the Mozambique Channel. Here, we present new evidence for neotectonic deformation derived from modern seismic reflection data and supported by additional geophysical data. The Kerimbas Graben offshore northern Mozambique is the most prominent manifestation of sub-recent extensional deformation. The seismic reflection data reveals that recent normal faulting often utilizes preexisting, deeply buried half-graben structures which likely are related to the formation of the Somali Basin. The ~30 km wide and ~150 km long symmetric graben is in a stage where the linkage of scattered normal faults already did happen, resulting in increased displacement and accommodation of most of the extension across the basin. However, deep earthquakes below the <span class="hlt">rift</span> indicate a strong and still preserved lithospheric mantle. Extension is becoming diffuse where an onshore suture, subdividing the northern from the southern metamorphic basement onshore Mozambique, is closest to the offshore <span class="hlt">rift</span>. It appears likely that this suture is the origin for the variation in <span class="hlt">rifting</span> style, indicating that mantle fabric resulting from a Cambrian collision has been preserved as mechanical anisotropy of the lithospheric mantle. Further south the <span class="hlt">rift</span> focuses in an about 30 km wide half-graben. An important finding is that the entire offshore branch of the EARS lacks significant volcanism. Along the offshore EARS there are only negligible indications for recent volcanism in the reflection seismic data such as sills and dikes. Apparently the "Comoros mantle plume" (French and Romanowicz, 2015) has a very minor influence on the progressive extensional deformation along the northern Mozambique continental margin, leading eventually to breakup sometimes in the future. Combining structural with earthquake data reveals that the magma</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..4312423S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..4312423S"><span>New insights into magma plumbing along <span class="hlt">rift</span> <span class="hlt">systems</span> from detailed observations of eruptive behavior at Axial volcano</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sigmundsson, Freysteinn</p> <p>2016-12-01</p> <p>The magma reservoir in geophysical volcano plumbing models is often modeled as a simple geometric volume, filled with magma of uniform properties. However, the constraints on reservoir size and magma properties in volcano roots are typically indirect and poor. Axial Seamount, a volcano at a depth of about 1500 m on the Juan de Fuca mid-oceanic ridge in the Pacific Ocean, has both high-resolution seismic images of its subsurface magma and detailed results from monitoring of its most recent eruption and associated seismicity and ground deformation. The 2015 eruption at Axial Seamount is the best monitored submarine eruption so far because of observations made possible by the Ocean Observatories Initiative, and seismic imaging of magma at this volcano is better than in most other environments because of advanced analysis of extensive seismic reflection profiling at sea and the relatively simple volcano structure. This allows new understanding compared to findings from earlier observations from monitored <span class="hlt">rifting</span> episodes on land. Geophysical magma plumbing models, in general, may need to allow for more complexities, namely, spatial heterogeneities in magma composition, melt content, and location of major volume changes within a single magma dominated crustal volume during eruptions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/7141016','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/7141016"><span>The Midcontinent <span class="hlt">Rift</span> and Grenville connection</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cambray, F.W.; Fujita, K. . Dept. of Geological Sciences)</p> <p>1994-04-01</p> <p>The Mid-Proterozoic, Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span> (MRS) is delineated by an inverted U shaped gravity and magnetic anomaly. It terminates in southeast Michigan but a less continuous series of anomalies and sediments, the Eastcontinent <span class="hlt">Rift</span> occur on a north-south line through Ohio and Kentucky. The geometry allows for a north-south opening, the Lake Superior section being orthogonal to opening, the western arm transtensional and the north-south trending eastern arm a transform boundary offset by pull-apart basins. The opening and closing of the <span class="hlt">rift</span> overlaps in time with the Grenville Orogeny. Grenville age rocks can also be found in the Llano uplift of Texas. The authors propose a model to explain the temporal and geographic association of the opening and closing of the MRS with the Grenville Orogeny that involves irregular suturing between two continental masses. Initiation of Grenville suturing, associated with south dipping subduction, in the northeast and in the Llano area of Texas would leave portion of unclosed ocean in between. Tensional stresses in the continental crust adjacent to the oceanic remnant could lead to its fragmentation and the formation of the MRS. The remaining oceanic lithosphere would eventually subduct, limiting the opening of the MRS. Continued convergence of the plates would induce compressional stresses thus accounting for the deformation of the MRS. An analogy is made with more recent opening of the Red Sea, Gulf of Aden <span class="hlt">Rift</span> <span class="hlt">System</span> in association with irregular collision along the Zagros-Bitlis Sutures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Tecto..34.2399L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Tecto..34.2399L"><span>Hierarchical segmentation of the Malawi <span class="hlt">Rift</span>: The influence of inherited lithospheric heterogeneity and kinematics in the evolution of continental <span class="hlt">rifts</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Laó-Dávila, Daniel A.; Al-Salmi, Haifa S.; Abdelsalam, Mohamed G.; Atekwana, Estella A.</p> <p>2015-12-01</p> <p>We used detailed analysis of Shuttle Radar Topography Mission-digital elevation model and observations from aeromagnetic data to examine the influence of inherited lithospheric heterogeneity and kinematics in the segmentation of largely amagmatic continental <span class="hlt">rifts</span>. We focused on the Cenozoic Malawi <span class="hlt">Rift</span>, which represents the southern extension of the Western Branch of the East African <span class="hlt">Rift</span> <span class="hlt">System</span>. This north trending <span class="hlt">rift</span> traverses Precambrian and Paleozoic-Mesozoic structures of different orientations. We found that the <span class="hlt">rift</span> can be hierarchically divided into first-order and second-order segments. In the first-order segmentation, we divided the <span class="hlt">rift</span> into Northern, Central, and Southern sections. In its Northern Section, the <span class="hlt">rift</span> follows Paleoproterozoic and Neoproterozoic terrains with structural grain that favored the localization of extension within well-developed border faults. The Central Section occurs within Mesoproterozoic-Neoproterozoic terrain with regional structures oblique to the <span class="hlt">rift</span> extent. We propose that the lack of inherited lithospheric heterogeneity favoring extension localization resulted in the development of the <span class="hlt">rift</span> in this section as a shallow graben with undeveloped border faults. In the Southern Section, Mesoproterozoic-Neoproterozoic rocks were reactivated and developed the border faults. In the second-order segmentation, only observed in the Northern Section, we divided the section into five segments that approximate four half-grabens/asymmetrical grabens with alternating polarities. The change of polarity coincides with flip-over full-grabens occurring within overlap zones associated with ~150 km long alternating border faults segments. The inherited lithospheric heterogeneity played the major role in facilitating the segmentation of the Malawi <span class="hlt">Rift</span> during its opening resulting from extension.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUSM.T43B..07A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUSM.T43B..07A"><span>Structural Evolution of the Incipient Okavango <span class="hlt">Rift</span> Zone, NW Botswana</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Atekwana, E. A.; Kinabo, B. D.; Modisi, M. P.; Hogan, J. P.; Wheaton, D. D.</p> <p>2005-05-01</p> <p>Studies of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS) and other continental <span class="hlt">rifts</span> have significantly improved our understanding of <span class="hlt">rifting</span> processes; however, we particularly lack studies of the embryonic stages of <span class="hlt">rift</span> creation. The Okavango <span class="hlt">Rift</span> Zone (ORZ), NW Botswana is one of few places worldwide where one can study the early stages of continental extension prior to the accumulation of significant amounts of sediments, volcanism, and multiphase deformation that obscure the investigation of these early time processes in more evolved continental <span class="hlt">rift</span> zones. In this study, gravity and aeromagnetic data have been used to examine the initiation and development of the nascent ORZ. The Okavango basin in NW Botswana is located at the southern tip of the southwestern branch of the EARS. The <span class="hlt">rift</span> is hosted within the Proterozoic fold and thrust belt of the Ghanzi-Chobe formation. Our objectives include (1) assessing the role of pre-existing structures on the development of <span class="hlt">rift</span> faults and basin architecture, (2) Examining fault linkage patterns and boarder fault development, and (3) determining the shallow subsurface basin geometry. Aeromagnetic data from the ORZ suggest two main structural trends: 1) northeast-southwest (030- 070o) and 2) northwest - southeast (290 - 320o). The 030- 070o structures occur within the <span class="hlt">rift</span> zone and throughout the surrounding basement. They form the main bounding fault <span class="hlt">system</span> of this incipient <span class="hlt">rift</span>. The NE - SW orientations of <span class="hlt">rift</span> faults mirror the fold axes and foliation of the basement rocks, suggesting that the basement fabric played an important role in localizing the development of faults within the stress regime present during the initiation of this <span class="hlt">rift</span>. Additionally, the greatest throw (~400- ~700 m) occurs along the Kunyere (NW dipping) and Tsau faults (SE dipping), defining a full graben as observed on gravity models. This differs from the half-graben model typical of most continental <span class="hlt">rift</span> zones. Thus, it appears the basin geometry was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....8758V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....8758V"><span>Neotectonics along the Turkana <span class="hlt">Rift</span> (North Kenya) from river network analysis, remote sensing and reflection seismic data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vetel, W.; Le Gall, B.; Tiercelin, J.-J.</p> <p>2003-04-01</p> <p>The NS-trending Turkana <span class="hlt">Rift</span> (North Kenya) cuts through a N140^oE transverse depressed zone between the Kenyan and Ethiopian domes. It forms a 200 km-long <span class="hlt">rift</span> segment of the East African <span class="hlt">Rift</span> <span class="hlt">System</span>, centered on the Turkana Lake. In this region, widespread <span class="hlt">rifting</span> occurred during the Oligocene to Mio-Pliocene and opened large NS-trending hemigrabens imaged by seismics to the West of the Turkana Lake. Because the Turkana <span class="hlt">rifted</span> zone is a low and poorly contrasted topographic area, it is difficult to draw the trace of the active <span class="hlt">rift</span>, in contrast with 1) the narrow (20 km-wide) N10^o-trending axial trough forming the Suguta valley to the South, and 2) the Chew Bahir faulted basin to the North. Despite a semi-arid climate, the Turkana area shows a dense and widely-distributed river drainage network dominated by the Turkwell, Kerio and Omo first-order rivers. The entire stream pattern has been extracted from Landsat satellite images and then analyzed in terms of drainage anomalies. Major anomalies have been recognized at various scales and assigned to active tectonics. The direct correlation between surface data and the deep structures imaged on seismics allows to precise the inherited (Oligo-Miocene) or newly-formed origin of the active deformation. Evidence for neotectonics are observed along 1) a large-scale transverse (EW) fault rooting at depth along a steep basement discontinuity (Turkwell), 2) a <span class="hlt">rift</span>-parallel (NS) fault zone probably emplaced during Plio-Pleistocene and actually bounding the Napedet volcanic plateau to the West, and 3) over a round-shaped uplifted zone caused by inversion tectonics (Kalabata). Structural interpretation of offshore high-resolution seismics from Lake Turkana illustrates the existence of recent deformation and also helps complete the overall neotectonic framework of the Turkana <span class="hlt">rift</span> zone. <span class="hlt">Finally</span>, this study leads us to regard the Turkana area as a broad (ca. 100 km wide) zone of diffuse extension where active deformation is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.T23F..06D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.T23F..06D"><span>Amagmatic Accretionary Segments, Ultraslow Spreading and Non-Volcanic <span class="hlt">Rifted</span> Margins (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dick, H. J.; Snow, J. E.</p> <p>2009-12-01</p> <p>The evolution of non-volcanic <span class="hlt">rifted</span> margins is key to understanding continental breakup and the early evolution of some of the world’s most productive hydrocarbon basins. However, the early stages of such <span class="hlt">rifting</span> are constrained by limited observations on ancient heavily sedimented margins such as Newfoundland and Iberia. Ultraslow spreading ridges, however, provide a modern analogue for early continental <span class="hlt">rifting</span>. Ultraslow spreading ridges (<20 mm/yr) comprise ~30% of the global ridge <span class="hlt">system</span> (e.g. Gakkel, Southwest Indian, Terceira, and Knipovitch Ridges). They have unique tectonics with widely spaced volcanic segments and amagmatic accretionary ridge segments. The volcanic segments, though far from hot spots, include some of the largest axial volcanoes on the global ridge <span class="hlt">system</span>, and have, unusual magma chemistry, often showing local isotopic and incompatible element enrichment unrelated to mantle hot spots. The transition from slow to ultraslow tectonics and spreading is not uniquely defined by spreading rate, and may also be moderated by magma supply and mantle temperature. Amagmatic accretionary segments are the 4th class of plate boundary structure, and, we believe, the defining tectonic feature of early continental breakup. They form at effective spreading rates <12 mm/yr, assume any orientation to spreading, and replace transform faults and magmatic segments. At amagmatic segments the earth splits apart with the mantle emplaced directly to the seafloor, and great slabs of peridotite are uplifted to form the <span class="hlt">rift</span> mountains. A thick conductive lid suppresses mantle melting, and magmatic segments form only at widely spaced intervals, with only scattered volcanics in between. Amagmatic segments link with the magmatic segments forming curvilinear plate boundaries, rather than the step-like morphology found at faster spreading ridges. These are all key features of non-volcanic <span class="hlt">rifted</span> margins; explaining, for example, the presence of mantle peridotites emplaced</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/114028','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/114028"><span>LANL environmental restoration site ranking <span class="hlt">system</span>: <span class="hlt">System</span> description. <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Merkhofer, L.; Kann, A.; Voth, M.</p> <p>1992-10-13</p> <p>The basic structure of the LANL Environmental Restoration (ER) Site Ranking <span class="hlt">System</span> and its use are described in this document. A related document, Instructions for Generating Inputs for the LANL ER Site Ranking <span class="hlt">System</span>, contains detailed descriptions of the methods by which necessary inputs for the <span class="hlt">system</span> will be generated. LANL has long recognized the need to provide a consistent basis for comparing the risks and other adverse consequences associated with the various waste problems at the Lab. The LANL ER Site Ranking <span class="hlt">System</span> is being developed to help address this need. The specific purpose of the <span class="hlt">system</span> is to help improve, defend, and explain prioritization decisions at the Potential Release Site (PRS) and Operable Unit (OU) level. The precise relationship of the Site Ranking <span class="hlt">System</span> to the planning and overall budget processes is yet to be determined, as the <span class="hlt">system</span> is still evolving. Generally speaking, the Site Ranking <span class="hlt">System</span> will be used as a decision aid. That is, the <span class="hlt">system</span> will be used to aid in the planning and budgetary decision-making process. It will never be used alone to make decisions. Like all models, the <span class="hlt">system</span> can provide only a partial and approximate accounting of the factors important to budget and planning decisions. Decision makers at LANL will have to consider factors outside of the formal <span class="hlt">system</span> when making <span class="hlt">final</span> choices. Some of these other factors are regulatory requirements, DOE policy, and public concern. The main value of the site ranking <span class="hlt">system</span>, therefore, is not the precise numbers it generates, but rather the general insights it provides.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/754794','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/754794"><span>Liquid waste treatment <span class="hlt">system</span>. <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Baker, M.N.; Houston, H.M.</p> <p>1999-06-01</p> <p>Pretreatment of high-level liquid radioactive waste (HLW) at the West Valley Demonstration Project (WVDP) involved three distinct processing operations: decontamination of liquid HLW in the Supernatant Treatment <span class="hlt">System</span> (STS); volume reduction of decontaminated liquid in the Liquid Waste Treatment <span class="hlt">System</span> (LWTS); and encapsulation of resulting concentrates into an approved cement waste form in the Cement Solidification <span class="hlt">System</span> (CSS). Together, these <span class="hlt">systems</span> and operations made up the Integrated Radwaste Treatment <span class="hlt">System</span> (IRTS).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70155923','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70155923"><span>Examination of the Reelfoot <span class="hlt">Rift</span> Petroleum <span class="hlt">System</span>, south-central United States, and the elements that remain for potential exploration and development</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Coleman, James; Pratt, Thomas L.</p> <p>2016-01-01</p> <p>No production has been established in the Reel-foot <span class="hlt">rift</span>. However, at least nine of 22 exploratory wells have reported petroleum shows, mainly gas shows with some asphalt or solid hydrocarbon residue. Regional seismic profiling shows the presence of two large inversion structures (Blytheville arch and Pascola arch). The Blytheville arch is marked by a core of structurally thickened Elvins Shale, whereas the Pascola arch reflects the structural uplift of a portion of the entire <span class="hlt">rift</span> basin. Structural uplift and faulting within the Reelfoot <span class="hlt">rift</span> since the late Paleozoic appear to have disrupted older conventional hydrocarbon traps and likely spilled any potential conventional petroleum accumulations. The remaining potential resources within the Reelfoot <span class="hlt">rift</span> are likely shale gas accumulations within the Elvins Shale; however, reservoir continuity and porosity as well as pervasive faulting appear to be significant future challenges for explorers and drillers.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814821C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814821C"><span>The <span class="hlt">rift</span> architecture and extensional tectonics of the South China Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cameselle, Alejandra L.; Ranero, César R.; Barckhausen, Udo; Franke, Dieter</p> <p>2016-04-01</p> <p>Non-volcanic <span class="hlt">rifted</span> continental margins are classically described as the product of lithospheric stretching and breakup leading to mantle exhumation, and subsequent seafloor spreading. However, recent studies question this model and indicate a wider range of structural evolutions, that challenge the existing model (e.g. Australia-Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> (Direen et al. 2007, 2011); the Tyrrhenian basin (Prada et al., 2014) or the South China Sea (Cameselle et al. 2015)). <span class="hlt">Rifting</span> in the South China Sea developed from a series of extensional events, from early Eocene to Late Oligocene, resulting in a V-shape oceanic basin affected by the occurrence of several spreading centers, ridges, transform faults and post-spreading volcanism. In recent years, this marginal basin - the largest in East Asia - has increasingly become one of the key sites for the study of <span class="hlt">rifting</span> and continental break-up. Its relative small size - compared to many classic, Atlantic-type continental margin settings - allows to easily match conjugated <span class="hlt">rifted</span> margins and its relative youth promotes the preservation of its original nature. To examine the <span class="hlt">rifting</span> evolution of the South China Sea, we have reprocessed with modern algorithms multichannel seismic profiles acquired during Sonne49 and BGR84 cruises across the three major subbasins: NW, SW and East subbasins. State-of-the-art of processing techniques have been used to increase the signal to noise ratio, including Tau-P and Wiener predictive deconvolution, multiple attenuation by both radon filtering and wave-equation-based surface-related multiple elimination (SRME) and time migration. To complement seismic interpretation, available vintage multichannel seismic data have been reprocessed with a post-stack flow, including Wiener deconvolution, FK-filtering, space and time variant band-pass filter and time migration. The improving quality of the seismic images shows a range of features including post-<span class="hlt">rift</span> and syn-<span class="hlt">rift</span> sediments, the structure of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811820Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811820Y"><span>Evolutionary model of the oblique <span class="hlt">rift</span> basins- Central African <span class="hlt">Rifts</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Kenn-Ming; Cheng, I.-Wen; Wu, Jong-Chang</p> <p>2016-04-01</p> <p>The geometry of oblique-<span class="hlt">rifting</span> basin is strongly related with the angle (α) between the trend of <span class="hlt">rift</span> and that of regional major extensional stress. The main purpose of this study is to investigate characteristics of geometry and kinematics of structure and tectono-stratigraphy during basin evolution of Central African <span class="hlt">Rifts</span> (CAS). In this study, we simulated the formation of oblique-<span class="hlt">rifting</span> basin with Particle Flow Code 3-Dimensions-(PFC 3D) and compared the simulation results with the tectonic settings of a series of basin in CAS. CAS started to develop in Early Cretaceous (130Ma) and lasted until the Late Cretaceous (85Ma-80Ma). The following collision between the African and Eurasian plates imposed compressional stress on CAS and folded the strata in the <span class="hlt">rift</span> basins. Although the characteristics of <span class="hlt">rift</span> basin formation remain controversial, palinspastic sections constructed in this study show that, in the Early Cretaceous, the <span class="hlt">rift</span> basins are mainly characterized by normal faults and half-grabens. In the Late Cretaceous, the morphology of the <span class="hlt">rift</span> basins was altered by large-scaled tectonic compression with the active Borogop Fault of regional scale. Also, en echelon trend of normal faults in the basins were measured and the angles between the trend with that of the <span class="hlt">rift</span> axes of each basin were demonstrated, indicating that the development of CAS was affected by the regional extensional stress with a dextral component during the <span class="hlt">rifting</span> process and, therefore, the <span class="hlt">rift</span> basins were formed by oblique-<span class="hlt">rifting</span>. In this study, we simulated the oblique-<span class="hlt">rifting</span> basin model of various α with Particle Flow Code 3-Dimensions-(PFC 3D). The main theory of PFC 3D is based on the Discrete Element Method (DEM), in which parameters are applied to every particle in the models. We applied forces acting on both sides of <span class="hlt">rift</span> axis, which α are 45°, 60°, 75° and 90° respectively, to simulate basin formation under oblique-<span class="hlt">rifting</span> process. The study results of simulation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Tectp.693..239Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Tectp.693..239Z"><span>Insights into the effects of oblique extension on continental <span class="hlt">rift</span> interaction from 3D analogue and numerical models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zwaan, Frank; Schreurs, Guido; Naliboff, John; Buiter, Susanne J. H.</p> <p>2016-12-01</p> <p>Continental <span class="hlt">rifts</span> often develop from linkage of distinct <span class="hlt">rift</span> segments under varying degrees of extension obliquity. These <span class="hlt">rift</span> segments arise from <span class="hlt">rift</span> initiation at non-aligned crustal heterogeneities and need to interact to develop a full-scale <span class="hlt">rift</span> <span class="hlt">system</span>. Here, we test the effects of 1) oblique extension and 2) initial heterogeneity (seed) offset on continental <span class="hlt">rift</span> interaction with the use of an improved analogue model set-up. X-ray computer tomography (CT) techniques are used to analyse the 3D models through time and the results are compared with additional numerical models and natural examples. The experimental results reveal that increasing extension obliquity strongly changes <span class="hlt">rift</span> segment structures from wide <span class="hlt">rifts</span> in orthogonal settings to narrower <span class="hlt">rifts</span> with oblique internal structures under oblique extension conditions to narrow strike-slip dominated <span class="hlt">systems</span> towards the strike-slip domain. We also find that both decreasing seed offset and increasing extension obliquity promote hard linkage of <span class="hlt">rift</span> segments through the formation of continuous <span class="hlt">rift</span> boundary faults at the surface. (Initial) soft linkage through the formation of relay ramps is more likely when seed offset increases or extension is more orthogonal. Rather than linking at depth, the <span class="hlt">rift</span> boundary faults curve around each other at depth and merge towards the surface to form a continuous trough. Orthogonal extension promotes the formation of intra-<span class="hlt">rift</span> horsts, which may provide hydrocarbon traps in nature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Tecto..33..485P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Tecto..33..485P"><span>Evolution, distribution, and characteristics of <span class="hlt">rifting</span> in southern Ethiopia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Philippon, Melody; Corti, Giacomo; Sani, Federico; Bonini, Marco; Balestrieri, Maria-Laura; Molin, Paola; Willingshofer, Ernst; Sokoutis, Dimitrios; Cloetingh, Sierd</p> <p>2014-04-01</p> <p>Southern Ethiopia is a key region to understand the evolution of the East African <span class="hlt">rift</span> <span class="hlt">system</span>, since it is the area of interaction between the main Ethiopian <span class="hlt">rift</span> (MER) and the Kenyan <span class="hlt">rift</span>. However, geological data constraining <span class="hlt">rift</span> evolution in this remote area are still relatively sparse. In this study the timing, distribution, and style of <span class="hlt">rifting</span> in southern Ethiopia are constrained by new structural, geochronological, and geomorphological data. The border faults in the area are roughly parallel to preexisting basement fabrics and are progressively more oblique with respect to the regional Nubia-Somalia motion proceeding southward. Kinematic indicators along these faults are mainly dip slip, pointing to a progressive rotation of the computed direction of extension toward the south. Radiocarbon data indicate post 30 ka faulting at both western and eastern margins of the MER with limited axial deformation. Similarly, geomorphological data suggest recent fault activity along the western margins of the basins composing the Gofa Province and in the Chew Bahir basin. This supports that interaction between the MER and the Kenyan <span class="hlt">rift</span> in southern Ethiopia occurs in a 200 km wide zone of ongoing deformation. Fault-related exhumation at ~10-12 Ma in the Gofa Province, as constrained by new apatite fission track data, occurred later than the ~20 Ma basement exhumation of the Chew Bahir basin, thus pointing to a northward propagation of the Kenyan <span class="hlt">rift</span>-related extension in the area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED506081.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED506081.pdf"><span><span class="hlt">Final</span> Paper DAT Cognitive Art Therapy <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Jacobson, Eric</p> <p>2009-01-01</p> <p>Del Giacco Art Therapy is a cognitive art therapy process that focuses on stimulating the mental sensory <span class="hlt">systems</span> and working to stabilize the nervous <span class="hlt">system</span> and create new neural connections in the brain. This <span class="hlt">system</span> was created by Maureen Del Giacco, Phd. after recovering from her own traumatic brain injury and is based on extensive research of…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=mois&pg=4&id=ED194687','ERIC'); return false;" href="http://eric.ed.gov/?q=mois&pg=4&id=ED194687"><span>Michigan Occupational Information <span class="hlt">System</span> <span class="hlt">Final</span> Evaluation Report.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Gordon, Eric M.; And Others</p> <p></p> <p>An evaluation of the Michigan Occupational Information <span class="hlt">System</span> (MOIS) was conducted. (The MOIS is a <span class="hlt">system</span> designed to provide reliable and current career information organized in a readily accessible <span class="hlt">system</span> for individuals involved in career exploration and decision making.) Three types of survey instruments (site, staff, and client surveys) were…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED247898.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED247898.pdf"><span>Selection of Microcomputer <span class="hlt">Systems</span>. <span class="hlt">Final</span> Report.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Barkley, John; And Others</p> <p></p> <p>Intended to provide assistance to non-technical end-users in evaluating the applicability of microcomputer-based <span class="hlt">systems</span> to their needs and in choosing appropriate <span class="hlt">systems</span>, this document recommends first identifying requirements and then identifying and evaluating alternative sources for application software, <span class="hlt">system</span> software and hardware, and…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/841361','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/841361"><span>Manzanita Hybrid Power <span class="hlt">system</span> Project <span class="hlt">Final</span> Report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Trisha Frank</p> <p>2005-03-31</p> <p>The Manzanita Indian Reservation is located in southeastern San Diego County, California. The Tribe has long recognized that the Reservation has an abundant wind resource that could be commercially utilized to its benefit, and in 1995 the Tribe established the Manzanita Renewable Energy Office. Through the U.S. Department of Energy's Tribal Energy Program the Band received funds to install a hybrid renewable power <span class="hlt">system</span> to provide electricity to one of the tribal community buildings, the Manzanita Activities Center (MAC building). The project began September 30, 1999 and was completed March 31, 2005. The <span class="hlt">system</span> was designed and the equipment supplied by Northern Power <span class="hlt">Systems</span>, Inc, an engineering company with expertise in renewable hybrid <span class="hlt">system</span> design and development. Personnel of the National Renewable Energy Laboratory provided technical assistance in <span class="hlt">system</span> design, and continued to provide technical assistance in <span class="hlt">system</span> monitoring. The grid-connected renewable hybrid wind/photovoltaic <span class="hlt">system</span> provides a demonstration of a solar/wind energy hybrid power-generating project on Manzanita Tribal land. During the <span class="hlt">system</span> design phase, the National Renewable Energy Lab estimated that the wind turbine is expected to produce 10,000-kilowatt hours per year and the solar array 2,000-kilowatt hours per year. The hybrid <span class="hlt">system</span> was designed to provide approximately 80 percent of the electricity used annually in the MAC building. The project proposed to demonstrate that this kind of a <span class="hlt">system</span> design would provide highly reliable renewable power for community uses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790017332','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790017332"><span>Solar heating <span class="hlt">system</span> <span class="hlt">final</span> design package</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1979-01-01</p> <p>The <span class="hlt">system</span> is composed of a warm air collector, a logic control unit and a universal switching and transport unit. The collector was originally conceived and designed as an integrated roof/wall <span class="hlt">system</span> and therefore provides a dual function in the structure. The collector serves both as a solar energy conversion <span class="hlt">system</span> and as a structural weather resistant skin. The control unit provides totally automatic control over the operation of the <span class="hlt">system</span>. It receives input data from sensor probes in collectors, storage and living space. The logic was designed so as to make maximum use of solar energy and minimize use of conventional energy. The transport and switching unit is a high-efficiency air-handling <span class="hlt">system</span> equipped with gear motor valves that respond to outputs from the control <span class="hlt">system</span>. The fan unit was designed for maximum durability and efficiency in operation, and has permanently lubricated ball bearings and excellent air-handling efficiency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED109375.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED109375.pdf"><span>Developing a Career Information <span class="hlt">System</span>: <span class="hlt">Final</span> Report.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>McKinlay, Bruce</p> <p></p> <p>The report reviews three years of progress toward implementing the Career Information <span class="hlt">System</span> (CIS), a statewide interagency consortium that provides current labor market and educational information in usable forms to students and clients and assists in the integration of such information into schools and social agencies in Oregon. The <span class="hlt">system</span>'s…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED272155.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED272155.pdf"><span>Instructional Support Software <span class="hlt">System</span>. <span class="hlt">Final</span> Report.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>McDonnell Douglas Astronautics Co. - East, St. Louis, MO.</p> <p></p> <p>This report describes the development of the Instructional Support <span class="hlt">System</span> (ISS), a large-scale, computer-based training <span class="hlt">system</span> that supports both computer-assisted instruction and computer-managed instruction. Written in the Ada programming language, the ISS software package is designed to be machine independent. It is also grouped into functional…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910056245&hterms=The_Gulf_of_California&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DThe_Gulf_of_California','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910056245&hterms=The_Gulf_of_California&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DThe_Gulf_of_California"><span>Age constraints for the present fault configuration in the Imperial Valley, California - Evidence for northwestward propagation of the Gulf of California <span class="hlt">rift</span> <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Larsen, Shawn; Reilinger, Robert</p> <p>1991-01-01</p> <p>Releveling and other geophysical data for the Imperial Valley of southern California suggest the northern section of the Imperial-Brawley fault <span class="hlt">system</span>, which includes the Mesquite Basin and Brawley Seismic Zone, is much younger than the 4 to 5 million year age of the valley itself. A minimum age of 3000 years is calculated for the northern segment of the Imperial fault from correlations between surface topography and geodetically observed seismic/interseismic vertical movements. Calculations of a maximum age of 80,000 years is based upon displacements in the crystalline basement along the Imperial fault, inferred from seismic refraction surveys. This young age supports recent interpretations of heat flow measurements, which also suggest that the current patterns of seismicity and faults in the Imperial Valley are not long lived. The current fault geometry and basement morphology suggest northwestward growth of the Imperial fault and migration of the Brawley Seismic Zone. It is suggested that this migration is a manifestation of the propagation of the Gulf of California <span class="hlt">rift</span> <span class="hlt">system</span> into the North American continent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810436S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810436S"><span>Exploiting the outcome of FUTUREVOLC: The 2014-2015 <span class="hlt">rifting</span> event, effusive eruption and gradual caldera collapse at Bardarbunga volcanic <span class="hlt">system</span>, Iceland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sigmundsson, Freysteinn; Vogfjord, Kristin S.; Gudmundson, Magnus T.; Ofeigsson, Benedikt G.; Dumont, Stéphanie; Parks, Michelle; Jonsdottir, Kristin; Hooper, Andrew; Hreinsdottir, Sigrun; Rafn Heimisson, Elias; White, Robert; Agustsdottir, Thorbjorg; Bean, Chris; Loughlin, Susan C.; Petur Heidarsson, Einar; Barsotti, Sara; Roberts, Matthew; Ripepe, Maurizio; Ilyinskaya, Evgenia; Consortium, Futurevolc</p> <p>2016-04-01</p> <p>Activity in the Bardarbunga volcanic <span class="hlt">system</span> in Iceland 2014-2015 included major lava eruption (~1.5 km3) and gradual caldera collapse (~66 m), connected by a 50-km-long laterally injected dyke that formed mostly over 2-4 weeks after onset of activity on 16 August 2014. This <span class="hlt">rifting</span> event is the main magmatic activity studied by the FUTUREVOLC project, a 3.5 year, 26-partner project funded by FP7 Environment Programme of the European Commission, addressing topic "Long-term monitoring experiment in geologically active regions of Europe prone to natural hazards: the Supersite concept. The project end is 31 March 2016 and it had aims to (i) establish an innovative volcano monitoring <span class="hlt">system</span> and strategy, (ii) develop new methods for near real-time integration of multi-parametric datasets, (iii) apply a seamless transdisciplinary approach to further scientific understanding of magmatic processes, and (iv) to improve delivery, quality and timeliness of transdisciplinary information from monitoring scientists to civil protection. A review will be presented on how FUTUREVOLC has contributed to the response and study of the Bardarbunga activity and other events in Iceland during the project period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900012177','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900012177"><span>Age constraints for the present fault configuration in the Imperial Valley, California: Evidence for northwestward propagation of the Gulf of California <span class="hlt">rift</span> <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Larsen, Shawn; Reilinger, Robert</p> <p>1990-01-01</p> <p>Releveling and other geophysical data for the Imperial Valley of southern California suggest the northern section of the Imperial-Brawley fault <span class="hlt">system</span>, which includes the Mesquite Basin and Brawley Seismic Zone, is much younger than the 4 to 5 million year age of the valley itself. A minimum age of 3000 years is calculated for the northern segment of the Imperial fault from correlations between surface topography and geodetically observed seismic/interseismic vertical movements. Calculations of a maximum age of 80,000 years is based upon displacements in the crystalline basement along the Imperial fault, inferred from seismic refraction surveys. This young age supports recent interpretations of heat flow measurements, which also suggest that the current patterns of seismicity and faults in the Imperial Valley are not long lived. The current fault geometry and basement morphology suggest northwestward growth of the Imperial fault and migration of the Brawley Seismic Zone. It is suggested that this migration is a manifestation of the propagation of the Gulf of California <span class="hlt">rift</span> <span class="hlt">system</span> into the North American continent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/663257','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/663257"><span>Proximity sensor <span class="hlt">system</span> development. CRADA <span class="hlt">final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Haley, D.C.; Pigoski, T.M.</p> <p>1998-01-01</p> <p>Lockheed Martin Energy Research Corporation (LMERC) and Merritt <span class="hlt">Systems</span>, Inc. (MSI) entered into a Cooperative Research and Development Agreement (CRADA) for the development and demonstration of a compact, modular proximity sensing <span class="hlt">system</span> suitable for application to a wide class of manipulator <span class="hlt">systems</span> operated in support of environmental restoration and waste management activities. In teleoperated modes, proximity sensing provides the manipulator operator continuous information regarding the proximity of the manipulator to objects in the workspace. In teleoperated and robotic modes, proximity sensing provides added safety through the implementation of active whole arm collision avoidance capabilities. Oak Ridge National Laboratory (ORNL), managed by LMERC for the United States Department of Energy (DOE), has developed an application specific integrated circuit (ASIC) design for the electronics required to support a modular whole arm proximity sensing <span class="hlt">system</span> based on the use of capacitive sensors developed at Sandia National Laboratories. The use of ASIC technology greatly reduces the size of the electronics required to support the selected sensor types allowing deployment of many small sensor nodes over a large area of the manipulator surface to provide maximum sensor coverage. The ASIC design also provides a communication interface to support sensor commands from and sensor data transmission to a distributed processing <span class="hlt">system</span> which allows modular implementation and operation of the sensor <span class="hlt">system</span>. MSI is a commercial small business specializing in proximity sensing <span class="hlt">systems</span> based upon infrared and acoustic sensors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940007574&hterms=fallout&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dfallout','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940007574&hterms=fallout&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dfallout"><span>Estimation of age of Dali-Ganis <span class="hlt">rifting</span> and associated volcanic activity, Venus</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Basilevsky, A. T.</p> <p>1993-01-01</p> <p>This paper deals with the estimation of age for the Dali and Ganis Chasma <span class="hlt">rift</span> zones and their associated volcanism based on photogeologic analysis of stratigraphic relations of <span class="hlt">rift</span>-associated features with impact craters which have associated features indicative of their age. The features are radar-dark and parabolic, and they are believed to be mantles of debris derived from fallout of the craters' ejecta. They are thought to be among the youngest features on the Venusian surface, so their 'parent' craters must also be very young, evidently among the youngest 10 percent of Venus' crater population. Dali Chasma and Ganis Chasma are a part of a <span class="hlt">system</span> of <span class="hlt">rift</span> zones contained within eastern Aphrodite and Atla Regio which is a significant component of Venus tectonics. The <span class="hlt">rifts</span> of this <span class="hlt">system</span> are fracture belts which dissect typical Venusian plains with rare islands of tessera terrain. The <span class="hlt">rift</span> zone <span class="hlt">system</span> consists of several segments following each other (Diane, Dali, Ganis) and forming the major <span class="hlt">rift</span> zone line, about 10,000 km long, which has junctions with several other <span class="hlt">rift</span> zones, including Parga Chasma <span class="hlt">Rift</span>. The junctions are usually locations of <span class="hlt">rift</span>-associated volcanism in the form of volcanic edifices (Maat and Ozza Montes) or plain-forming flows flooding some areas within the <span class="hlt">rift</span> zones and the adjacent plains.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012GGG....13.1012L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012GGG....13.1012L"><span>Deformation and seismicity associated with continental <span class="hlt">rift</span> zones propagating toward continental margins</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lyakhovsky, V.; Segev, A.; Schattner, U.; Weinberger, R.</p> <p>2012-01-01</p> <p>We study the propagation of a continental <span class="hlt">rift</span> and its interaction with a continental margin utilizing a 3-D lithospheric model with a seismogenic crust governed by a damage rheology. A long-standing problem in <span class="hlt">rift</span>-mechanics, known as thetectonic force paradox, is that the magnitude of the tectonic forces required for <span class="hlt">rifting</span> are not large enough in the absence of basaltic magmatism. Our modeling results demonstrate that under moderate <span class="hlt">rift</span>-driving tectonic forces the <span class="hlt">rift</span> propagation is feasible even in the absence of magmatism. This is due to gradual weakening and "long-term memory" of fractured rocks that lead to a significantly lower yielding stress than that of the surrounding intact rocks. We show that the style, rate and the associated seismicity pattern of the <span class="hlt">rift</span> zone formation in the continental lithosphere depend not only on the applied tectonic forces, but also on the rate of healing. Accounting for the memory effect provides a feasible solution for thetectonic force paradox. Our modeling results also demonstrate how the lithosphere structure affects the geometry of the propagating <span class="hlt">rift</span> <span class="hlt">system</span> toward a continental margin. Thinning of the crystalline crust leads to a decrease in the propagation rate and possibly to <span class="hlt">rift</span> termination across the margin. In such a case, a new fault <span class="hlt">system</span> is created perpendicular to the direction of the <span class="hlt">rift</span> propagation. These results reveal that the local lithosphere structure is one of the key factors controlling the geometry of the evolving <span class="hlt">rift</span> <span class="hlt">system</span> and seismicity pattern.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6763519','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6763519"><span>Water-storage-tube <span class="hlt">systems</span>. <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hemker, P.</p> <p>1981-12-24</p> <p>Passive solar collection/storage/distribution <span class="hlt">systems</span> were surveyed, designed, fabricated, and mechanically and thermally tested. The types studied were clear and opaque fiberglass tubes, metal tubes with plastic liners, and thermosyphoning tubes. (MHR)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1342493','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1342493"><span>PV <span class="hlt">Systems</span> Reliability <span class="hlt">Final</span> Technical Report.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lavrova, Olga; Flicker, Jack David; Johnson, Jay; Armijo, Kenneth Miguel; Gonzalez, Sigifredo; Schindelholz, Eric John; Sorensen, Neil R.; Yang, Benjamin Bing-Yeh</p> <p>2015-12-01</p> <p>The continued exponential growth of photovoltaic technologies paves a path to a solar-powered world, but requires continued progress toward low-cost, high-reliability, high-performance photovoltaic (PV) <span class="hlt">systems</span>. High reliability is an essential element in achieving low-cost solar electricity by reducing operation and maintenance (O&M) costs and extending <span class="hlt">system</span> lifetime and availability, but these attributes are difficult to verify at the time of installation. Utilities, financiers, homeowners, and planners are demanding this information in order to evaluate their financial risk as a prerequisite to large investments. Reliability research and development (R&D) is needed to build market confidence by improving product reliability and by improving predictions of <span class="hlt">system</span> availability, O&M cost, and lifetime. This project is focused on understanding, predicting, and improving the reliability of PV <span class="hlt">systems</span>. The two areas being pursued include PV arc-fault and ground fault issues, and inverter reliability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/972164','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/972164"><span>Analysis of Hybrid Hydrogen <span class="hlt">Systems</span>: <span class="hlt">Final</span> Report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dean, J.; Braun, R.; Munoz, D.; Penev, M.; Kinchin, C.</p> <p>2010-01-01</p> <p>Report on biomass pathways for hydrogen production and how they can be hybridized to support renewable electricity generation. Two hybrid <span class="hlt">systems</span> were studied in detail for process feasibility and economic performance. The best-performing <span class="hlt">system</span> was estimated to produce hydrogen at costs ($1.67/kg) within Department of Energy targets ($2.10/kg) for central biomass-derived hydrogen production while also providing value-added energy services to the electric grid.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T31B2875S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T31B2875S"><span>Concentration of strain in a marginal <span class="hlt">rift</span> zone of the Japan backarc during post-<span class="hlt">rift</span> compression</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sato, H.; Ishiyama, T.; Kato, N.; Abe, S.; Shiraishi, K.; Inaba, M.; Kurashimo, E.; Iwasaki, T.; Van Horne, A.; No, T.; Sato, T.; Kodaira, S.; Matsubara, M.; Takeda, T.; Abe, S.; Kodaira, C.</p> <p>2015-12-01</p> <p>Late Cenozoic deformation zones in Japan may be divided into two types: (1) arc-arc collision zones like those of Izu and the Hokkaido axial zone, and (2) reactivated back-arc marginal <span class="hlt">rift</span> (BMR) <span class="hlt">systems</span>. A BMR develops during a secondary <span class="hlt">rifting</span> event that follows the opening of a back-arc basin. It forms close to the volcanic front and distant from the spreading center of the basin. In Japan, a BMR <span class="hlt">system</span> developed along the Sea of Japan coast following the opening of the Japan Sea. The BMR appears to be the weakest, most deformable part of the arc back-arc <span class="hlt">system</span>. When active <span class="hlt">rifting</span> in the marginal basins ended, thermal subsidence, and then mechanical subsidence related to the onset of a compressional stress regime, allowed deposition of up to 5 km of post-<span class="hlt">rift</span>, deep-marine to fluvial sedimentation. Continued compression produced fault-related folds in the post-<span class="hlt">rift</span> sediments, in thin-skin style deformation. Shortening reached a maximum in the BMR <span class="hlt">system</span> compared to other parts of the back-arc, suggesting that it is the weakest part of the entire <span class="hlt">system</span>. We examined the structure of the BMR <span class="hlt">system</span> using active source seismic investigation and earthquake tomography. The velocity structure beneath the marginal <span class="hlt">rift</span> basin shows higher P-wave velocity in the upper mantle/lower crust which suggests significant mafic intrusion and thinning of the upper continental crust. The syn-<span class="hlt">rift</span> mafic intrusive forms a convex shape, and the boundary between the pre-<span class="hlt">rift</span> crust and the mafic intrusive dips outward. In the post-<span class="hlt">rift</span> compressional stress regime, the boundary of the mafic body reactivated as a reverse fault, forming a large-scale wedge thrust and causing further subsidence of the <span class="hlt">rift</span> basin. The driver of the intense shortening event along the Sea of Japan coast in SW Japan was the arrival of a buoyant young (15 Ma) Shikoku basin at the Nankai Trough. Subduction stalled and the backarc was compressed. As the buoyant basin cooled, subduction resumed, and the rate of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1612168L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1612168L"><span>Stable isotope-based Plio-Pleistocene ecosystem reconstruction of some of the earliest hominid fossil sites in the East African <span class="hlt">Rift</span> <span class="hlt">System</span> (Chiwondo Beds, N Malawi)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lüdecke, Tina; Thiemeyer, Heinrich; Schrenk, Friedemann; Mulch, Andreas</p> <p>2014-05-01</p> <p>The isotope geochemistry of pedogenic carbonate and fossil herbivore enamel is a powerful tool to reconstruct paleoenvironmental conditions in particular when climate change plays a key role in the evolution of ecosystems. Here, we present the first Plio-Pleistocene long-term carbon (δ13C), oxygen (δ18O) and clumped isotope (Δ47) records from pedogenic carbonate and herbivore teeth in the Malawi <span class="hlt">Rift</span>. These data represent an important southern hemisphere record in the East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS), a key region for reconstructing vegetation patterns in today's Zambezian Savanna and correlation with data on the evolution and migration of early hominids across the Inter-Tropical Convergence Zone. As our study site is situated between the well-known hominid-bearing sites of eastern and southern Africa in the Somali-Masai Endemic Zone and Highveld Grassland it fills an important geographical gap for early hominid research. 5.0 to 0.6 Ma fluviatile and lacustrine deposits of the Chiwondo Beds (NE shore of Lake Malawi) comprise abundant pedogenic carbonate and remains of a diverse fauna dominated by large terrestrial mammals. These sediments are also home to two hominid fossil remains, a mandible of Homo rudolfensis and a maxillary fragment of Paranthropus boisei, both dated around 2.4 Ma. The Chiwondo Beds therefore document early co-existence of these two species. We evaluate δ13C data from fossil enamel of different suid, bovid, and equid species and contrast these with δ13C and δ18O values of pedogenic carbonate. We complement the latter with clumped isotope soil temperature data. Results of almost 800 pedogenic carbonate samples from over 20 sections consistently average δ13C = -8.5 ‰ over the past 5 Ma with no significant short-term δ13C excursions or long-term trends. The data from molar tooth enamel of nine individual suids of the genera Metridiochoerus, Notochoerus and Nyanzachoerus support these findings with average δ13C = -10.0 ‰. The absence</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMDI24A..04H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMDI24A..04H"><span>Mapping Mantle Mixing and the Extent of Superplume Influence Using He-Ne-Ar-CO2-N2 Isotopes: The Case of the East Africa <span class="hlt">Rift</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hilton, D. R.; Halldorsson, S. A.; Scarsi, P.; Castillo, P.; Abebe, T.; Kulongoski, J. T.</p> <p>2014-12-01</p> <p>Earth's mantle possesses distinct and variable volatile characteristics as sampled by magmatic activity in different tectonic environments. In general, trace element depleted mid-ocean ridge basalts, with low Sr and Pb isotope values (but high ɛNd and ɛHf), release mantle-derived noble gases characterised by 3He/4He ~8 ± 1RA, (21Ne/22Ne)ex ~0.06 and 40Ar/36Ar ≥ 10,000 with CO2 and N2 having δ13C~-5‰ and δ15N ~-5‰, respectively. In contrast, enriched intraplate lavas possess higher 3He/4He (up to 50RA), lower (21Ne/22Ne)ex ~0.035 and 40Ar/36Ar ≤ 10,000 with generally higher but variable δ13C and δ15N. These isotopic attributes of mantle-derived volatiles can be exploited to map the extent, and mixing characteristics, of enriched (plume) mantle with depleted asthenospheric mantle ± the effects of over-riding lithosphere and/or crust. The East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS) is superimposed upon two massive plateaux - the Ethiopia and Kenya domes - regarded as geophysical manifestations of a superplume source, a huge thermochemical anomaly originated at the core-mantle boundary and providing dynamic support for the plateaux. We present new volatile isotopic and relative abundance data (on the same samples) for geothermal fluids (He-CO2-N2), lavas (He-Ne-Ar) and xenoliths (He-Ne-Ar-CO2-N2) which provide an unprecedented overview of the distribution of mantle volatiles of the Ethiopia Dome, from the Red Sea via the Afar region and Main Ethiopian <span class="hlt">Rift</span> (MER) to the Turkana Depression. Notably, peaks in geothermal fluid 3He/4He (16RA) and δ15N (+6.5‰) are coincident within the MER but the maximum δ13C (-0.78‰) lies ~100 km to the south. Highs in 3He/4He (14RA), δ13C (~-1‰) and δ15N (+3.4‰) for mafic crystals occur in the Afar region ~ 500km to the north. We assess the significance of the off-set in these volatile isotope signals, for sampling volatile heterogeneity in the plume source and/or the relative sensitivity of different volatiles to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70034427','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70034427"><span>Low lower crustal velocity across Ethiopia: Is the Main Ethiopian <span class="hlt">Rift</span> a narrow <span class="hlt">rift</span> in a hot craton?</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Keranen, K.M.; Klemperer, S.L.; Julia, J.; Lawrence, J. F.; Nyblade, A.A.</p> <p>2009-01-01</p> <p>[1] The Main Ethiopian <span class="hlt">Rift</span> (MER) is a classic narrow <span class="hlt">rift</span> that developed in hot, weak lithosphere, not in the initially cold, thick, and strong lithosphere that would be predicted by common models of <span class="hlt">rift</span> mode formation. Our new 1-D seismic velocity profiles from Rayleigh wave/receiver function joint inversion across the MER and the Ethiopian Plateau indicate that hot lower crust and upper mantle are present throughout the broad region affected by Oligocene flood basalt volcanism, including both the present <span class="hlt">rift</span> and the adjacent Ethiopian Plateau hundreds of kilometers from the <span class="hlt">rift</span> valley. The region of hot lithosphere closely corresponds to the region of flood basalt volcanism, and we interpret that the volcanism and thermal perturbation were jointly caused by impingement of the Afar plume head. Across the affected region, Vs is 3.6-3.8 km/s in the lowermost crust and ???4.3 km/s in the uppermost mantle, both ??0.3 km/s lower than in the eastern and western branches of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> to the south. We interpret the low Vs in the lower crust and upper mantle as indicative of hot lithosphere with partial melt. Our results lead to a hybrid <span class="hlt">rift</span> mode, in which the brittle upper crust has developed as a narrow <span class="hlt">rift</span> along the Neoproterozoic suture between East and West Gondwana, while at depth lithospheric deformation is distributed over the broad region (??400 km wide) thermally perturbed by the broad thermal upwelling associated with the Afar plume head. Development of both the East African <span class="hlt">Rift</span> <span class="hlt">System</span> to the south (in cold, strong lithosphere) and the MER to the north (in hot, weak lithosphere) as narrow <span class="hlt">rifts</span>, despite their vastly different initial thermal states and depth-integrated lithospheric strength, indicates that common models of <span class="hlt">rift</span> mode formation that focus only on temperature, thickness, and vertical strength profiles do not apply to these classic continental <span class="hlt">rifts</span>. Instead, inherited structure and associated lithospheric weaknesses are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1011381','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1011381"><span><span class="hlt">Final</span> Report Advanced Quasioptical Launcher <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jeffrey Neilson</p> <p>2010-04-30</p> <p>This program developed an analytical design tool for designing antenna and mirror <span class="hlt">systems</span> to convert whispering gallery RF modes to Gaussian or HE11 modes. Whispering gallery modes are generated by gyrotrons used for electron cyclotron heating of fusion plasmas in tokamaks. These modes cannot be easily transmitted and must be converted to free space or waveguide modes compatible with transmission line <span class="hlt">systems</span>.This program improved the capability of SURF3D/LOT, which was initially developed in a previous SBIR program. This suite of codes revolutionized quasi-optical launcher design, and this code, or equivalent codes, are now used worldwide. This program added functionality to SURF3D/LOT to allow creating of more compact launcher and mirror <span class="hlt">systems</span> and provide direct coupling to corrugated waveguide within the vacuum envelope of the gyrotron. Analysis was also extended to include full-wave analysis of mirror transmission line <span class="hlt">systems</span>. The code includes a graphical user interface and is available for advanced design of launcher <span class="hlt">systems</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10141858','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10141858"><span>National Geoscience Data Repository <span class="hlt">System</span>. <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schiffries, C.M.; Milling, M.E.</p> <p>1994-03-01</p> <p>The American Geological Institute (AGI) has completed the first phase of a study to assess the feasibility of establishing a National Geoscience Data Repository <span class="hlt">System</span> to capture and preserve valuable geoscientific data. The study was initiated in response to the fact that billions of dollars worth of domestic geological and geophysical data are in jeopardy of being irrevocably lost or destroyed as a consequence of the ongoing downsizing of the US energy and minerals industry. This report focuses on two major issues. First, it documents the types and quantity of data available for contribution to a National Geoscience Data Repository <span class="hlt">System</span>. Second, it documents the data needs and priorities of potential users of the <span class="hlt">system</span>. A National Geoscience Data Repository <span class="hlt">System</span> would serve as an important and valuable source of information for the entire geoscience community for a variety of applications, including environmental protection, water resource management, global change studies, and basic and applied research. The repository <span class="hlt">system</span> would also contain critical data that would enable domestic energy and minerals companies to expand their exploration and production programs in the United States for improved recovery of domestic oil, gas, and mineral resources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/207362','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/207362"><span>Sequencing Information Management <span class="hlt">System</span> (SIMS). <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fields, C.</p> <p>1996-02-15</p> <p>A feasibility study to develop a requirements analysis and functional specification for a data management <span class="hlt">system</span> for large-scale DNA sequencing laboratories resulted in a functional specification for a Sequencing Information Management <span class="hlt">System</span> (SIMS). This document reports the results of this feasibility study, and includes a functional specification for a SIMS relational schema. The SIMS is an integrated information management <span class="hlt">system</span> that supports data acquisition, management, analysis, and distribution for DNA sequencing laboratories. The SIMS provides ad hoc query access to information on the sequencing process and its results, and partially automates the transfer of data between laboratory instruments, analysis programs, technical personnel, and managers. The SIMS user interfaces are designed for use by laboratory technicians, laboratory managers, and scientists. The SIMS is designed to run in a heterogeneous, multiplatform environment in a client/server mode. The SIMS communicates with external computational and data resources via the internet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/918761','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/918761"><span>Autonomous microexplosives subsurface tracing <span class="hlt">system</span> <span class="hlt">final</span> report.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Engler, Bruce Phillip; Nogan, John; Melof, Brian Matthew; Uhl, James Eugene; Dulleck, George R., Jr.; Ingram, Brian V.; Grubelich, Mark Charles; Rivas, Raul R.; Cooper, Paul W.; Warpinski, Norman Raymond; Kravitz, Stanley H.</p> <p>2004-04-01</p> <p>The objective of the autonomous micro-explosive subsurface tracing <span class="hlt">system</span> is to image the location and geometry of hydraulically induced fractures in subsurface petroleum reservoirs. This <span class="hlt">system</span> is based on the insertion of a swarm of autonomous micro-explosive packages during the fracturing process, with subsequent triggering of the energetic material to create an array of micro-seismic sources that can be detected and analyzed using existing seismic receiver arrays and analysis software. The project included investigations of energetic mixtures, triggering <span class="hlt">systems</span>, package size and shape, and seismic output. Given the current absence of any technology capable of such high resolution mapping of subsurface structures, this technology has the potential for major impact on petroleum industry, which spends approximately $1 billion dollar per year on hydraulic fracturing operations in the United States alone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5719436','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5719436"><span>New passive solar cooking <span class="hlt">system</span>. <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schlussler, L.</p> <p>1981-11-01</p> <p>The development of a solar cooking <span class="hlt">system</span> which uses a phase change process to passively transfer heat from a collector to a cooker is presented. In the design of this cooking <span class="hlt">system</span> steam is produced in the collector and then is used as the heat transfer fluid in the cooker. The most efficient use of the <span class="hlt">system</span> is to heat food directly by condensing the steam onto the food, whereas a heat exchanger is necessary to heat an oven or a frying pan. A pressure cooker was successfully built and tested using the steam from the collector. Brief discussions on the collector design and performance, and heat storage phase change materials are provided. (BCS)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ESS.....350205G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ESS.....350205G"><span>The <span class="hlt">final</span> fate of planetary <span class="hlt">systems</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gaensicke, Boris</p> <p>2015-12-01</p> <p>The discovery of the first extra-solar planet around a main-sequence star in 1995 has changed the way we think about the Universe: our solar <span class="hlt">system</span> is not unique. Twenty years later, we know that planetary <span class="hlt">systems</span> are ubiquitous, orbit stars spanning a wide range in mass, and form in an astonishing variety of architectures. Yet, one fascinating aspect of planetary <span class="hlt">systems</span> has received relatively little attention so far: their ultimate fate.Most planet hosts will eventually evolve into white dwarfs, Earth-sized stellar embers, and the outer parts of their planetary <span class="hlt">systems</span> (in the solar <span class="hlt">system</span>, Mars and beyond) can survive largely intact for billions of years. While scattered and tidally disrupted planetesimals are directly detected at a small number of white dwarfs in the form infrared excess, the most powerful probe for detecting evolved planetary <span class="hlt">systems</span> is metal pollution of the otherwise pristine H/He atmospheres.I will present the results of a multi-cycle HST survey that has obtained COS observations of 136 white dwarfs. These ultraviolet spectra are exquisitely sensitive to the presence of metals contaminating the white atmosphere. Our sophisticated model atmosphere analysis demonstrates that at least 27% of all targets are currently accreting planetary debris, and an additional 29% have very likely done so in the past. These numbers suggest that planet formation around A-stars (the dominant progenitors of today's white dwarf population) is similarly efficient as around FGK stars.In addition to post-main sequence planetary <span class="hlt">system</span> demographics, spectroscopy of the debris-polluted white dwarf atmospheres provides a direct window into the bulk composition of exo-planetesimals, analogous to the way we use of meteorites to determine solar-<span class="hlt">system</span> abundances. Our ultraviolet spectroscopy is particularly sensitive to the detection of Si, a dominant rock-forming species, and we identify up to ten additional volatile and refractory elements in the most strongly</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED060919.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED060919.pdf"><span>DISCUS Interactive <span class="hlt">System</span> Users' Manual. <span class="hlt">Final</span> Report.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Silver, Steven S.; Meredith, Joseph C.</p> <p></p> <p>The results of the second 18 months (December 15, 1968-June 30, 1970) of effort toward developing an Information Processing Laboratory for research and education in library science is reported in six volumes. This volume contains: the basic on-line interchange, DISCUS operations, programming in DISCUS, concise DISCUS specifications, <span class="hlt">system</span> author…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/290910','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/290910"><span>Hydrogen energy <span class="hlt">systems</span> studies. <span class="hlt">Final</span> technical report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ogden, J.M.; Kreutz, T.; Kartha, S.; Iwan, L.</p> <p>1996-08-13</p> <p>The results of previous studies suggest that the use of hydrogen from natural gas might be an important first step toward a hydrogen economy based on renewables. Because of infrastructure considerations (the difficulty and cost of storing, transmitting and distributing hydrogen), hydrogen produced from natural gas at the end-user`s site could be a key feature in the early development of hydrogen energy <span class="hlt">systems</span>. In the first chapter of this report, the authors assess the technical and economic prospects for small scale technologies for producing hydrogen from natural gas (steam reformers, autothermal reformers and partial oxidation <span class="hlt">systems</span>), addressing the following questions: (1) What are the performance, cost and emissions of small scale steam reformer technology now on the market? How does this compare to partial oxidation and autothermal <span class="hlt">systems</span>? (2) How do the performance and cost of reformer technologies depend on scale? What critical technologies limit cost and performance of small scale hydrogen production <span class="hlt">systems</span>? What are the prospects for potential cost reductions and performance improvements as these technologies advance? (3) How would reductions in the reformer capital cost impact the delivered cost of hydrogen transportation fuel? In the second chapter of this report the authors estimate the potential demand for hydrogen transportation fuel in Southern California.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70024528','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70024528"><span>Crustal structure of central Lake Baikal: Insights into intracontinental <span class="hlt">rifting</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>ten Brink, U.S.; Taylor, M.H.</p> <p>2002-01-01</p> <p>The Cenozoic <span class="hlt">rift</span> <span class="hlt">system</span> of Baikal, located in the interior of the largest continental mass on Earth, is thought to represent a potential analog of the early stage of breakup of supercontinents. We present a detailed P wave velocity structure of the crust and sediments beneath the Central Basin, the deepest basin in the Baikal <span class="hlt">rift</span> <span class="hlt">system</span>. The structure is characterized by a Moho depth of 39-42.5 km; an 8-km-thick, laterally continuous high-velocity (7.05-7.4 km/s) lower crust, normal upper mantle velocity (8 km/s), a sedimentary section reaching maximum depths of 9 km, and a gradual increase of sediment velocity with depth. We interpret the high-velocity lower crust to be part of the Siberian Platform that was not thinned or altered significantly during <span class="hlt">rifting</span>. In comparison to published results from the Siberian Platform, Moho under the basin is elevated by <3 km. On the basis of these results we propose that the basin was formed by upper crustal extension, possibly reactivating structures in an ancient fold-and-thrust belt. The extent and location of upper mantle extension are not revealed by our data, and it may be offset from the <span class="hlt">rift</span>. We believe that the Baikal <span class="hlt">rift</span> structure is similar in many respects to the Mesozoic Atlantic <span class="hlt">rift</span> <span class="hlt">system</span>, the precursor to the formation of the North Atlantic Ocean. We also propose that the Central Baikal <span class="hlt">rift</span> evolved by episodic fault propagation and basin enlargement, rather than by two-stage <span class="hlt">rift</span> evolution as is commonly assumed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.4428B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.4428B"><span>Next-generation Geotectonic Data Analysis: Using pyGPlates to quantify <span class="hlt">Rift</span> Obliquity during Supercontinent Dispersal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Butterworth, Nathaniel; Brune, Sascha; Williams, Simon; Müller, Dietmar</p> <p>2015-04-01</p> <p>Fragmentation of a supercontinent by <span class="hlt">rifting</span> is an integral part of plate tectonics, yet the dynamics that govern the success or failure of individual <span class="hlt">rift</span> <span class="hlt">systems</span> are still unclear. Recently, analytical and thermo-mechanical modelling has suggested that obliquely activated <span class="hlt">rifts</span> are mechanically favoured over orthogonal <span class="hlt">rift</span> <span class="hlt">systems</span>. Hence, where two <span class="hlt">rift</span> zones compete, the more oblique <span class="hlt">rift</span> proceeds to break-up while the less oblique one stalls and becomes an aulacogen. This implies that the orientation and shape of individual <span class="hlt">rift</span> <span class="hlt">systems</span> affects the relative motion of Earth's continents during supercontinent break-up. We test this hypothesis using the latest global plate tectonic reconstructions for the past 200 million years. The analysis is performed using pyGPlates, a recently developed Python library that allows script-based access to the plate reconstruction software GPlates. We quantify <span class="hlt">rift</span> obliquity, extension velocity and their temporal evolution for all small-scale <span class="hlt">rift</span> segments that constituted a major <span class="hlt">rift</span> <span class="hlt">system</span> during the last 200 million years. Boundaries between continental and oceanic crust (COBs) mark the end of <span class="hlt">rifting</span> and the beginning of sea floor spreading, which is why we use a global set of updated COBs in order to pinpoint continental break-up and as a proxy for the local trend of former <span class="hlt">rift</span> <span class="hlt">systems</span>. Analysing the entire length of all <span class="hlt">rift</span> <span class="hlt">systems</span> during the last 200 My, we find a mean obliquity of ~40° (measured as the angle between extension direction and local <span class="hlt">rift</span> trend normal), with a standard deviation of 25°. More than 75% of all <span class="hlt">rift</span> segments exceeded an obliquity of 20° highlighting the fact that oblique <span class="hlt">rifting</span> is the rule, not the exception. More specifically, East and West Gondwana split along the East African coast with a mean obliquity of 45°. While <span class="hlt">rifting</span> of the central and southern South Atlantic segment involved a low obliquity of 10°, the Equatorial Atlantic opened under a high angle of 60°. The separation of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1980JGR....85.3647H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1980JGR....85.3647H"><span>Propagating <span class="hlt">rifts</span> on midocean ridges</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hey, Richard; Duennebier, Frederick K.; Morgan, W. Jason</p> <p>1980-07-01</p> <p>Spreading center jumps identified west of the Galapagos Islands near 95°W occur in a pattern consistent with the propagating <span class="hlt">rift</span> hypothesis. A new <span class="hlt">rift</span> is gradually breaking through the Cocos plate. Each successive jump is slightly longer than the preceding jump. The new spreading center grows at a new azimuth toward the west as the old one dies. The jumps are a manifestation of <span class="hlt">rift</span> propagation. We extend the analysis of propagating <span class="hlt">rifts</span> to the case of continuous propagation and predict patterns of magnetic anomalies and bathymetry consistent with the observed patterns. In particular, we correctly predict the trends of fossil spreading centers and V patterns of magnetic anomaly offsets required by the propagating <span class="hlt">rift</span> hypothesis. Similar V patterns have been observed on many other spreading centers and have been interpreted in various ways. The propagating <span class="hlt">rift</span> hypothesis appears to offer a simple explanation, consistent with rigid plate tectonics, for each of these patterns. This hypothesis may also have important implications for continental <span class="hlt">rifting</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1035012','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1035012"><span>FY07 <span class="hlt">Final</span> Report for Calibration <span class="hlt">Systems</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Myers, Tanya L.; Broocks, Bryan T.; Cannon, Bret D.; Ho, Nicolas</p> <p>2007-12-01</p> <p>Remote infrared (IR) sensing provides a valuable method for detection and identification of materials associated with nuclear proliferation. Current challenges for remote sensors include minimizing the size, mass, and power requirements for cheaper, smaller, and more deployable instruments without affecting the measurement performance. One area that is often overlooked is sensor calibration design that is optimized to minimize the cost, size, weight, and power of the payload. Yet, an on-board calibration <span class="hlt">system</span> is essential to account for changes in the detector response once the instrument has been removed from the laboratory. The Calibration <span class="hlt">Systems</span> project at Pacific Northwest National Laboratory (PNNL) is aimed towards developing and demonstrating compact quantum cascade (QC) laser-based calibration <span class="hlt">systems</span> for infrared sensor <span class="hlt">systems</span> in order to provide both a spectral and radiometric calibration while minimizing the impact on the instrument payload. In FY05, PNNL demonstrated a multi-level radiance scheme that provides six radiance levels for an enhanced linearity check compared to the currently accepted two-point scheme. PNNL began testing the repeatability of this scheme using a cryogenically cooled, single-mode quantum cascade laser (QCL). A cyclic variation in the power was observed that was attributed to the thermal cycling of the laser's dewar. In FY06, PNNL continued testing this scheme and installed an auxiliary liquid nitrogen reservoir to limit the thermal cycling effects. Although better repeatability was achieved over a longer time period, power fluctuations were still observed due to the thermal cycling. Due to the limitations with the cryogenic <span class="hlt">system</span>, PNNL began testing Fabry-Perot QCLs that operate continuous-wave (cw) or quasi-cw at room temperature (RT) in FY06. PNNL demonstrated a multi-level scheme that provides five radiance levels in 105 seconds with excellent repeatability. We have continued testing this repeatability in FY07. A burn</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/836268','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/836268"><span><span class="hlt">Final</span> Report of Strongly Interacting Fermion <span class="hlt">Systems</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wilkins, J. W.</p> <p>2001-06-25</p> <p>There has been significant progress in three broad areas: (A) Optical properties, (B) Large-scale computations, and (C) Many-body <span class="hlt">systems</span>. In this summary the emphasis is primarily on those papers that point to the research plans. At the same time, some important analytic work is not neglected, some of it even appearing in the description of large-scale Computations. Indeed one of the aims of such computations is to give new insights which lead to development of models capable of simple analytic or nearly analytic analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/993365','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/993365"><span>FY2008 Calibration <span class="hlt">Systems</span> <span class="hlt">Final</span> Report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cannon, Bret D.; Myers, Tanya L.; Broocks, Bryan T.</p> <p>2009-01-01</p> <p>The Calibrations project has been exploring alternative technologies for calibration of passive sensors in the infrared (IR) spectral region. In particular, we have investigated using quantum cascade lasers (QCLs) because these devices offer several advantages over conventional blackbodies such as reductions in size and weight while providing a spectral source in the IR with high output power. These devices can provide a rapid, multi-level radiance scheme to fit any nonlinear behavior as well as a spectral calibration that includes the fore-optics, which is currently not available for on-board calibration <span class="hlt">systems</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6418113','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6418113"><span>Revised Hazard Ranking <span class="hlt">System</span> (HRS): <span class="hlt">Final</span> rule</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1990-11-09</p> <p>The U.S. Environmental Protection Agency (EPA) has revised the Hazard Ranking <span class="hlt">System</span> (HRS) in response to the Superfund Amendments and Reauthorization Act of 1986 (SARA). The HRS is the scoring <span class="hlt">system</span> EPA uses to assess the relative threat associated with the release or potential release of hazardous substances from a waste site. The HRS score is the primary criterion EPA uses to determine whether a site should be placed on the National Priorities List (NPL). The NPL identifies sites that warrant further investigation to determine if they pose risks to public health or the environment. Sites on the NPL are eligible for long-term remedial action financed under the Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA), as amended by SARA. The revised HRS retains the same cutoff score and basic approach as the original HRS, while incorporating SARA requirements as well as improvements identified as necessary by EPA and the public. The revised HRS retains the ground water, surface water, and air pathways drops the direct contact and fire/explosion pathways, and adds a forth pathway, soil exposure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/192410','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/192410"><span>Imaging <span class="hlt">systems</span> for biomedical applications. <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Radparvar, M.</p> <p>1995-06-06</p> <p>Many of the activities of the human body manifest themselves by the presence of a very weak magnetic field outside the body, a field that is so weak that an ultra-sensitive magnetic sensor is needed for specific biomagnetic measurements. Superconducting QUantum Interference Devices (SQUIDs) are extremely sensitive detectors of magnetic flux and have been used extensively to detect the human magnetocardiogram, and magnetoencephalogram. and other biomagnetic signals. In order to utilize a SQUID as a magnetometer, its transfer characteristics should be linearized. This linearization requires extensive peripheral electronics, thus limiting the number of SQUID magnetometer channels in a practical <span class="hlt">system</span>. The proposed digital SQUID integrates the processing circuitry on the same cryogenic chip as the SQUID magnetometer and eliminates the sophisticated peripheral electronics. Such a <span class="hlt">system</span> is compact and cost effective, and requires minimal support electronics. Under a DOE-sponsored SBIR program, we designed, simulated, laid out, fabricated, evaluated, and demonstrated a digital SQUID magnetometer. This report summarizes the accomplishments under this program and clearly demonstrates that all of the tasks proposed in the phase II application were successfully completed with confirmed experimental results.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/665884','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/665884"><span>Geophysical tomography imaging <span class="hlt">system</span>. <span class="hlt">Final</span> CRADA report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Norton, S.J.; Won, I.J.</p> <p>1998-05-20</p> <p>The Cooperative Research and Development Agreement (CRADA) between Lockheed Martin Energy <span class="hlt">Systems</span>, Inc., and Geophex, Ltd., was established to investigate high-resolution, shallow acoustic imaging of the subsurface. The primary objectives of the CRADA were accomplished, including the evaluation of a new tomographic imaging algorithm and the testing and comparison of two different acoustic sources, the hammer/plate source and an electromagnetic vibratory source. The imaging <span class="hlt">system</span> was composed essentially of a linear array of geophones, a digital seismograph, and imaging software installed on a personal computer. Imaging was most successful using the hammer source, which was found to be less susceptible to ground roll (surface wave) interference. It is conjectured that the vibratory source will perform better for deeper targets for which ground roll is less troublesome. Potential applications of shallow acoustic imaging are numerous, including the detection and characterization of buried solid waste, unexploded ordnance, and clandestine man-made underground structures associated with treaty verification (e.g., tunnels, underground storage facilities, hidden bunkers).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70044480','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70044480"><span>A model for Iapetan <span class="hlt">rifting</span> of Laurentia based on Neoproterozoic dikes and related rocks</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Burton, William C.; Southworth, Scott</p> <p>2010-01-01</p> <p>Geologic evidence of the Neoproterozoic <span class="hlt">rifting</span> of Laurentia during breakup of Rodinia is recorded in basement massifs of the cratonic margin by dike swarms, volcanic and plutonic rocks, and <span class="hlt">rift</span>-related clastic sedimentary sequences. The spatial and temporal distribution of these geologic features varies both within and between the massifs but preserves evidence concerning the timing and nature of <span class="hlt">rifting</span>. The most salient features include: (1) a <span class="hlt">rift</span>-related magmatic event recorded in the French Broad massif and the southern and central Shenandoah massif that is distinctly older than that recorded in the northern Shenandoah massif and northward; (2) felsic volcanic centers at the north ends of both French Broad and Shenandoah massifs accompanied by dike swarms; (3) differences in volume between massifs of cover-sequence volcanic rocks and <span class="hlt">rift</span>-related clastic rocks; and (4) WNW orientation of the Grenville dike swarm in contrast to the predominately NE orientation of other Neoproterozoic dikes. Previously proposed <span class="hlt">rifting</span> mechanisms to explain these features include <span class="hlt">rift</span>-transform and plume–triple-junction <span class="hlt">systems</span>. The <span class="hlt">rift</span>-transform <span class="hlt">system</span> best explains features 1, 2, and 3, listed here, and we propose that it represents the dominant <span class="hlt">rifting</span> mechanism for most of the Laurentian margin. To explain feature 4, as well as magmatic ages and geochemical trends in the Northern Appalachians, we propose that a plume–triple-junction <span class="hlt">system</span> evolved into the <span class="hlt">rift</span>-transform <span class="hlt">system</span>. A ca. 600 Ma mantle plume centered east of the Sutton Mountains generated the radial dike swarm of the Adirondack massif and the Grenville dike swarm, and a collocated triple junction generated the northern part of the <span class="hlt">rift</span>-transform <span class="hlt">system</span>. An eastern branch of this <span class="hlt">system</span> produced the Long Range dike swarm in Newfoundland, and a subsequent western branch produced the ca. 554 Ma Tibbit Hill volcanics and the ca. 550 Ma <span class="hlt">rift</span>-related magmatism of Newfoundland.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1134810','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1134810"><span>Physics of Correlated <span class="hlt">Systems</span>, <span class="hlt">Final</span> Project Report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Greene, Chris H.</p> <p>2014-06-25</p> <p>The funding of this DOE project has enabled the P.I. and his collaborators to tackle a number of problems involving nonperturbatively coupled atomic <span class="hlt">systems</span>, including their interactions with each other and/or with an external electromagnetic field of the type provided by either a continuous-wave or a femtosecond short-pulse laser. The progress includes a new, deeper understanding of an old and famous theory of autoionization lineshapes, developed initially by Ugo Fano in 1935 and later extended in a highly cited 1961 article; the new result specifically is that in a collaboration with the Heidelberg group we have been able to demonstrate an unexpectedly simple behavior in the time domain that is relevant for modern short-pulse lasers. This study also demonstrates a way to modify and even control the lineshapes of unstable atomic and molecular energy levels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1211538G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1211538G"><span><span class="hlt">Rifts</span> in the tectonic structure of East Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Golynsky, Dmitry; Golynsky, Alexander</p> <p>2010-05-01</p> <p>It was established that riftogenic and/or large linear tectonic structures in East Antarctica are distributed with a steady regularity with average distance between them about 650 km. All these structures (13) represent objects of undoubted scientific and practical interest and might be considered as immediate objects for conducting integrated geological and geophysical investigations. Analysis and generalization of the RADARSAT satellite <span class="hlt">system</span> imagery and radio-echosounding survey data collected in the eastern part of Princess Elizabeth Land allow us to distinguish spatial boundaries of previously unknown continental <span class="hlt">rift</span> <span class="hlt">system</span> that was proposed to name Gaussberg (Golynsky & Golynsky, 2007). The <span class="hlt">rift</span> is about 500 km long, and taking into consideration its western continuation in the form of short (fragmented) faults, may exceed 700 km. The elevation difference between depressions and horsts reaches 3 km. The <span class="hlt">rift</span> structure consists of two sub-parallel depressions separated by segmented horst-like rises (escarpments). Deep depressions within the <span class="hlt">rift</span> reach more than 800 m bsl near the West Ice Shelf and within the central graben occupied by the Phillipi Glacier. The width of the Gaussberg <span class="hlt">Rift</span> <span class="hlt">system</span> varies from 60 km in the south-western area to 150 km near the West Ice Shelf. The Gaussberg <span class="hlt">rift</span> is considered as a part of the Lambert <span class="hlt">rift</span> <span class="hlt">system</span>, which has a complicated structure clearly recognized over both the continent and also its margin. The Gaussberg <span class="hlt">rift</span> probably exploited a weak zone between the Proterozoic mobile belt and the Archaean Vestfold-Rauer cratonic block. Supposedly it initiated at the turn of Jurassic and Permian epoch or a little bit earlier as in case of the Lambert <span class="hlt">rift</span> where the Permian graben formation with coal-bearing deposits predetermined the subsequent development of submeridional <span class="hlt">rift</span> zone. The Gaussberg and also the Scott <span class="hlt">rift</span> developed in the Queen Marie Land, may be considered as continuations of the Mahanadi Valley <span class="hlt">rift</span> and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFM.T51B0871B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFM.T51B0871B"><span>Regional Hydrothermal Cooling During the Initiation of Continental <span class="hlt">Rifting</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buck, W. R.</p> <p>2001-12-01</p> <p>Thermochronologic data from the uplifted flanks of the Red Sea clearly indicate at least two distinct phases of regional cooling: the first at about 32 Ma and the second at about 21 Ma according to Omar and Steckler (1995). The latter phase correlates well with the rapid subsidence in the <span class="hlt">rift</span> and uplift of the flanks. Thus this cooling data is generally interpreted to result from tectonic denudation. The earlier cooling is more problematic, since sediments of the same age are not clearly identified in <span class="hlt">rift</span> basins. A different explanation for the early cooling episode is suggested by numerical models of lithospheric stretching. Those models show that <span class="hlt">rift</span> initiation can result in a very broad region of lithospheric downbending. This bending produces small magnitude (several percent) surface extension of the sides of the <span class="hlt">rift</span>. Eventually, these <span class="hlt">rift</span> flanks are bent in the opposite sense and uplifted. The earlier phase of extensional strain may create a <span class="hlt">system</span> of cracks and faults of sufficient permeability to allow significant water circulation. Hydrothermal flow could produce cooling of rocks as deep as 5-10 km. The cooling would be recorded in low-temperature thermochrologic <span class="hlt">systems</span> such as apatite fission tracks. Model thermal histories for different <span class="hlt">rift</span> and hydrothermal flow histories are compared to fission track data from the Red Sea region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26601442','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26601442"><span><span class="hlt">Rift</span> Valley fever.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Paweska, J T</p> <p>2015-08-01</p> <p><span class="hlt">Rift</span> Valley fever (RVF) is a mosquito-borne zoonotic viral disease affecting domestic and wild ruminants, camels and humans. The causative agent of RVF, the RVF virus (RVFV), has the capacity to cause large and severe outbreaks in animal and human populations and to cross significant natural geographic barriers. <span class="hlt">Rift</span> Valley fever is usually inapparent in non-pregnant adult animals, but pregnant animals and newborns can be severely affected; outbreaks are characterised by a sudden onset of abortions and high neonatal mortality. The majority of human infections are subclinical or associated with moderate to severe, non-fatal, febrile illness, but some patients may develop a haemorrhagic syndrome and/or ocular and neurological lesions. In both animals and humans, the primary site of RVFV replication and tissue pathology is the liver. Outbreaks of RVF are associated with persistent high rainfalls leading to massive flooding and the emergence of large numbers of competent mosquito vectors that transmit the virus to a wide range of susceptible vertebrate species. Outbreaks of RVF have devastating economic effects on countries for which animal trade constitutes the main source of national revenue. The propensity of the virus to spread into new territories and re-emerge in traditionally endemic regions, where it causes large outbreaks in human and animal populations, presents a formidable challenge for public and veterinary health authorities. The presence of competent mosquito vectors in RVF-free countries, the wide range of mammals susceptible to the virus, altering land use, the global changes in climate, and increased animal trade and travel are some of the factors which might contribute to international spread of RVF.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SolED...6.2885D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SolED...6.2885D"><span>Fault evolution in the Potiguar <span class="hlt">rift</span> termination, Equatorial margin of Brazil</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Castro, D. L.; Bezerra, F. H. R.</p> <p>2014-10-01</p> <p>The transform shearing between South American and African plates in the Cretaceous generated a series of sedimentary basins on both plate margins. In this study, we use gravity, aeromagnetic, and resistivity surveys to identify fault architecture and to analyse the evolution of the eastern Equatorial margin of Brazil. Our study area is the southern onshore termination of the Potiguar <span class="hlt">rift</span>, which is an aborted NE-trending <span class="hlt">rift</span> arm developed during the breakup of Pangea. The Potiguar <span class="hlt">rift</span> is a Neocomian structure located in the intersection of the Equatorial and western South Atlantic and is composed of a series of NE-trending horsts and grabens. This study reveals new grabens in the Potiguar <span class="hlt">rift</span> and indicates that stretching in the southern <span class="hlt">rift</span> termination created a WNW-trending, 10 km wide and ~40 km long right-lateral strike-slip fault zone. This zone encompasses at least eight depocenters, which are bounded by a left-stepping, en-echelon <span class="hlt">system</span> of NW- to EW-striking normal faults. These depocenters form grabens up to 1200 m deep with a rhomb-shaped geometry, which are filled with <span class="hlt">rift</span> sedimentary units and capped by post-<span class="hlt">rift</span> sedimentary sequences. The evolution of the <span class="hlt">rift</span> termination is consistent with the right-lateral shearing of the Equatorial margin in the Cretaceous and occurs not only at the <span class="hlt">rift</span> termination, but also as isolated structures away from the main <span class="hlt">rift</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/578546','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/578546"><span>Buried waste containment <span class="hlt">system</span> materials. <span class="hlt">Final</span> Report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Weidner, J.R.; Shaw, P.G.</p> <p>1997-10-01</p> <p>This report describes the results of a test program to validate the application of a latex-modified cement formulation for use with the Buried Waste Containment <span class="hlt">System</span> (BWCS) process during a proof of principle (POP) demonstration. The test program included three objectives. One objective was to validate the barrier material mix formulation to be used with the BWCS equipment. A basic mix formula for initial trials was supplied by the cement and latex vendors. The suitability of the material for BWCS application was verified by laboratory testing at the Idaho National Engineering and Environmental Laboratory (INEEL). A second objective was to determine if the POP BWCS material emplacement process adversely affected the barrier material properties. This objective was met by measuring and comparing properties of material prepared in the INEEL Materials Testing Laboratory (MTL) with identical properties of material produced by the BWCS field tests. These measurements included hydraulic conductivity to determine if the material met the US Environmental Protection Agency (EPA) requirements for barriers used for hazardous waste sites, petrographic analysis to allow an assessment of barrier material separation and segregation during emplacement, and a set of mechanical property tests typical of concrete characterization. The third objective was to measure the hydraulic properties of barrier material containing a stop-start joint to determine if such a feature would meet the EPA requirements for hazardous waste site barriers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008cosp...37..636D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008cosp...37..636D"><span>Using of Remote Sensing Techniques for Monitoring the Earthquakes Activities Along the Northern Part of the Syrian <span class="hlt">Rift</span> <span class="hlt">System</span> (LEFT-LATERAL),SYRIA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dalati, Moutaz</p> <p></p> <p>Earthquake mitigation can be achieved with a better knowledge of a region's infra-and substructures. High resolution Remote Sensing data can play a significant role to implement Geological mapping and it is essential to learn about the tectonic setting of a region. It is an effective method to identify active faults from different sources of Remote Sensing and compare the capability of some satellite sensors in active faults survey. In this paper, it was discussed a few digital image processing approaches to be used for enhancement and feature extraction related to faults. Those methods include band ratio, filtering and texture statistics . The experimental results show that multi-spectral images have great potentials in large scale active faults investigation. It has also got satisfied results when deal with invisible faults. Active Faults have distinct features in satellite images. Usually, there are obvious straight lines, circular structures and other distinct patterns along the faults locations. Remotely Sensed imagery Landsat ETM and SPOT XS /PAN are often used in active faults mapping. Moderate and high resolution satellite images are the best choice, because in low resolution images, the faults features may not be visible in most cases. The area under study is located Northwest of Syria that is part of one of the very active deformation belt on the Earth today. This area and the western part of Syria are located along the great <span class="hlt">rift</span> <span class="hlt">system</span> (Left-Lateral or African- Syrian <span class="hlt">Rift</span> <span class="hlt">System</span>). Those areas are tectonically active and caused a lot of seismically events. The AL-Ghab graben complex is situated within this wide area of Cenozoic deformation. The <span class="hlt">system</span> formed, initially, as a result of the break up of the Arabian plate from the African plate. This action indicates that these sites are active and in a continual movement. In addition to that, the statistic analysis of Thematic Mapper data and the features from a digital elevation model ( DEM )produced from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711846S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711846S"><span>Contribution of the FUTUREVOLC project to the study of segmented lateral dyke growth in the 2014 <span class="hlt">rifting</span> event at Bárðarbunga volcanic <span class="hlt">system</span>, Iceland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sigmundsson, Freysteinn; Hooper, Andrew; Hreinsdóttir, Sigrún; Vogfjörd, Kristín S.; Ófeigsson, Benedikt; Rafn Heimisson, Elías; Dumont, Stéphanie; Parks, Michelle; Spaans, Karsten; Guðmundsson, Gunnar B.; Drouin, Vincent; Árnadóttir, Thóra; Jónsdóttir, Kristín; Gudmundsson, Magnús T.; Samsonov, Sergey; Brandsdóttir, Bryndís; White, Robert S.; Ágústsdóttir, Thorbjörg; Björnsson, Helgi; Bean, Christopher J.</p> <p>2015-04-01</p> <p>The FUTUREVOLC project (a 26-partner project funded by FP7 Environment Programme of the European Commission, addressing topic "Long-term monitoring experiment in geologically active regions of Europe prone to natural hazards: the Supersite concept) set aims to (i) establish an innovative volcano monitoring <span class="hlt">system</span> and strategy, (ii) develop new methods for near real-time integration of multi-parametric datasets, (iii) apply a seamless transdisciplinary approach to further scientific understanding of magmatic processes, and (iv) to improve delivery, quality and timeliness of transdisciplinary information from monitoring scientists to civil protection. The project duration is 1 October 2012 - 31 March 2016. Unrest and volcanic activity since August 2014 at one of the focus areas of the project in Iceland, at the Bárðarbunga volcanic <span class="hlt">system</span>, near the middle of the project duration, has offered unique opportunities for this project. On 16 August 2014 an intense seismic swarm started in Bárðarbunga, the beginning of a major volcano-tectonic <span class="hlt">rifting</span> event forming over 45 km long dyke extending from the caldera to Holuhraun lava field outside the northern margin of Vatnajökull. A large basaltic, effusive fissure eruption began in Holuhraun on 31 August which had by January formed a lava field with a volume in excess of one cubic kilometre. We document how the FUTUREVOLC project has contributed to the study and response to the subsurface dyke formation, through increased seismic and geodetic coverage and joint interpreation of the data. The dyke intrusion in the Bárðarbunga volcanic <span class="hlt">system</span>, grew laterally for over 45 km at a variable rate, with an influence of topography on the direction of propagation. Barriers at the ends of each segment were overcome by the build-up of pressure in the dyke end; then a new segment formed and dyke lengthening temporarily peaked. The dyke evolution, which occurred over 14 days, was revealed by propagating seismicity, ground</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.3548I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.3548I"><span>Recent geodynamics and evolution of the Moma <span class="hlt">rift</span>, Northeast Asia.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Imaev, V. S.; Imaeva, L. P.; Kozmin, B. M.; Fujita, K. S.; Mackey, K. G.</p> <p>2009-04-01</p> <p>The Cenozoic Moma <span class="hlt">rift</span> <span class="hlt">system</span> is a major tectonic feature in northeast Russia. It is composed of a series of basins (Selennyakh, Kyrin,Lower Moma,Upper Moma,etc.) filled with up to one km thick and bounded by the Chersky Range (up to 3100 m high) on the southwest and the Moma Range (up to 2400 m high) on the northeast. Northeast of the Moma Range is the Indigirka-Zyryanka foreland basin, composed of thick, up to 2.5 km, Eocene, Oligocene, and Miocene coal-bearing sequences, while on the southwestern side of the Chersky Range there are a number of piedmont basins (Tuostakh, Upper Adycha, Derbeke, etc.) containing up to several hundred meters of Miocene and Oligocene coal-bearing deposits. Despite considerable study over the past half-century, there is considerable debate over the origin, present-day tectonics, and evolution of the Moma <span class="hlt">rift</span> <span class="hlt">system</span>. The Cenozoic deposits of the basins generally become younger from northwest to southeast with the exception of the Seimchan-Buyunda basin. In the northeast, fan-shaped coal-bearing basins (e.g., Nenneli, Olzhoi, Selennyakh, Uyandina, Tommot, and others) are filled with Miocene to Pliocene deposits, while basins in the southeast (e.g., Taskan) are filled with Neogene sediments. The Seimchan-Buyunda basin, however, has sediments of Oligocene age. The Moma <span class="hlt">rift</span> <span class="hlt">system</span> is reflected a major step in the gravity field, presumably separating denser rocks of the Kolyma-Omolon superterrain from somewhat less dense rocks of the Verkhoyansk fold belt (margin of the North Asian Craton). Analysis of travel-times of Pn and Pg waves from local earthquakes indicates an area of thinned crust (30-35 km) southwest of the Moma <span class="hlt">rift</span> <span class="hlt">system</span>, extending as a "tongue" from the Lena River delta and the Laptev Sea to the upper part of the Kolyma River, as compared to 40-45 km in the surrounding areas. This region of thinned crust also coincides with a region of high heat flow values measured in boreholes of the Chersky Range (up to 88 mW/m2). Hot</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5862861','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5862861"><span>Sedimentary deposits in response to <span class="hlt">rift</span> geometry in Malawi, Africa</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bishop, M.G. )</p> <p>1991-03-01</p> <p>Sedimentary deposits of the Malawi continental <span class="hlt">rift</span> basin are a direct result of topography and tectonics unique to <span class="hlt">rift</span> structure. Recent models describe <span class="hlt">rifts</span> as asymmetric half-graben connected in series by transfer of accommodation zones. Half-graben consist of roughly parallel, tilted fault blocks stepping up from the bounding fault zone where maximum subsidence occurs. The <span class="hlt">rift</span> becomes a local baselevel and depocenter as regional drainage is shed away by the <span class="hlt">rift</span> shoulders. Most of the sediments are derived locally due to internal drainage of connected basins, individual basins, and individual fault blocks. The patterns of sedimentation and facies associations depend on structural position at both fault block and half-graben scales. Drainage is directed and dammed by tilted fault blocks. Forward-tilted fault blocks form basinward-thickening sediment wedges filled with facies of axial fluvial <span class="hlt">systems</span>, alluvial fault-scarp fans, and ponded swamp and lake deposits. These deposits are asymmetrically shifted toward the controlling fault and onlap the upthrown side of the block, ordinarily the site of erosion or nondeposition. Rivers entering the lake on back tilted fault blocks form large deltas resulting in basinward fining and thinning sediment wedges. Lacustrine, nearshore, shoreline, and lake shore plain deposits over multiple fault blocks record lake levels, water chemistry, and tectonic episodes. Tectonic movement periodically changes the basin depth, configuration, and baselevel. This movement results in widespread unconformities deposition and reworking of sediments within the <span class="hlt">rift</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFM.S11D..12B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFM.S11D..12B"><span>P Wave Velocity Structure Beneath the Baikal <span class="hlt">Rift</span> Axis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brazier, R. A.; Nyblade, A. A.; Boman, E. C.</p> <p>2001-12-01</p> <p>Over 100 p wave travel times from the 1500 km en echelon Baikal <span class="hlt">Rift</span> <span class="hlt">system</span> are used in this study.The events range 3 to 13 degrees from Talaya, Russia (TLY) along the axis of southwest northeast trending <span class="hlt">rift</span> in East Siberia. A Herglotz Wiechert inversion of these events resolved a crust of 6.4 km/s and a gradient in the mantle starting at 35 km depth and 7.7 km/s down to 200 km depth and 8.2 km/s. This is compatible with Gao et al,1994 cross sectional structure which cuts the <span class="hlt">rift</span> at about 400km from TLY. The Baikal <span class="hlt">Rift</span> hosts the deepest lake and is the most seismically active <span class="hlt">rift</span> in the world. It is one of the few continental <span class="hlt">rifts</span>, it separates the Siberian craton and the Syan-Baikal mobile fold belt. Two events, the March 21 1999 magnitude 5.7 earthquake 638 km from TLY and the November 13th 1995 magnitude 5.9 earthquake 863 km from TLY were modeled for there PnL wave structure using the discrete wavenumber method and the Harvard CMT solutions with adjusted depths from p-pP times. The PnL signals match well. A genetic algorithm will used to perturb the velocity structure and compare to a selection of the events between 3 and 13 degrees many will require moment tensor solutions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T53C2732T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T53C2732T"><span>Control of initial heterogeneities and boundary conditions on the deformation partitioning of continental <span class="hlt">rift</span>: a comparison between Rio Grande <span class="hlt">Rift</span> and Main Ethiopian <span class="hlt">Rift</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thieulot, C.; Philippon, M.; Sokoutis, D.; Van Wijk, J. W.; Willingshofer, E.; Cloetingh, S.</p> <p>2012-12-01</p> <p>Understanding how initial heterogeneities and boundary conditions control the development of fault network and the deformation partitioning mechanisms in <span class="hlt">rifts</span> that affect continental crust still remains a challenge. Among the active continental <span class="hlt">rifts</span> affecting the Earth lithosphere, the Main Ethiopian <span class="hlt">Rift</span> (MER) and the Rio Grande <span class="hlt">Rift</span> (RGR) appear to be ideal natural laboratories to investigate this issues as they share structural characteristics but develop under different geological settings. From a structural point of view both <span class="hlt">rifts</span> show the same length (~1000km), width (50 to 70 km) and asymmetry. The MER is the NE-SW trending plate boundary between the Nubian and Somalian plates that has been developing for the past 11 Ma above a paleo-proterozoic lithospheric-scale weak zone re-heated by the Afar hotspot, whereas the RGR is the eastern "boundary" of the basin & range <span class="hlt">system</span> that has been developing for the past 30 Ma in the frame of a westward retreating Farallon subduction zone. However, the RGR shows evidence of low angle normal faulting whereas the MER shows steeply dipping normal faults and conversely the MER shows a larger volume of erupted lavas than the RGR. Combined with a structural analysis of both <span class="hlt">rifts</span>, we present here a series of preliminary numerical models that allows for a better understanding of the influence of initial heterogeneities such as 1) the state of the crust (craton versus crust affected by "wide <span class="hlt">rift</span>" type extension); 2) the presence of a crustal-scale to lithospheric-scale weak zone, 3) the effect of the orientation of these weak zones & 4) the effects of the presence of magma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMDI11B2583N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMDI11B2583N"><span>Mid-lithospheric Discontinuity Beneath the Malawi <span class="hlt">Rift</span>, Deduced from Gravity Studies and its Relation to the <span class="hlt">Rifting</span> Process.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Njinju, E. A.; Atekwana, E. A.; Mickus, K. L.; Abdelsalam, M. G.; Atekwana, E. A.; Laó-Dávila, D. A.</p> <p>2015-12-01</p> <p>The World Gravity Map satellite gravity data were used to investigate the lithospheric structure beneath the Cenozoic-age Malawi <span class="hlt">Rift</span> which forms the southern extension of the Western Branch of the East African <span class="hlt">Rift</span> <span class="hlt">System</span>. An analysis of the data using two-dimensional (2D) power spectrum methods indicates the two distinctive discontinuities at depths of 31‒44 km and 64‒124 km as defined by the two steepest slopes of the power spectrum curves. The shallower discontinuity corresponds to the crust-mantle boundary (Moho) and compares well with Moho depth determined from passive seismic studies. To understand the source of the deeper discontinuity, we applied the 2D power spectrum analysis to other <span class="hlt">rift</span> segments of the Western Branch as well as regions with stable continental lithospheres where the lithospheric structure is well constrained through passive seismic studies. We found that the deeper discontinuity corresponds to a mid-lithospheric discontinuity (MLD), which is known to exist globally at depths between 60‒150 km and as determined by passive seismic studies. Our results show that beneath the Malawi <span class="hlt">Rift</span>, there is no pattern of N-S elongated crustal thinning following the surface expression of the Malawi <span class="hlt">Rift</span>. With the exception of a north-central region of crustal thinning (< 35 km), most of the southern part of the <span class="hlt">rift</span> is underlain by thick crust (~40‒44 km). Different from the Moho, the MLD is shallower beneath the axis of the Malawi <span class="hlt">Rift</span> forming a N-S trending zone with depths of 64‒80 km, showing a broad and gentle topography. We interpret the MLD as representing a sharp density contrast resulting from metasomatized lithosphere due to lateral migration along mobile belts of hot mantle melt or fluids from a distant plume and not from an ascending asthenosphere. These fluids weaken the lithosphere enhancing <span class="hlt">rift</span> nucleation. The availability of satellite gravity worldwide makes gravity a promising technique for determining the MLD globally.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860021678','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860021678"><span>On the differences in continental <span class="hlt">rifting</span> at the Earth, Mars and Venus</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nikishin, A. M.; Milanovsky, E. E.</p> <p>1985-01-01</p> <p>During the process of continental <span class="hlt">rifting</span> on Earth, the lower ductile crust stretches, forming a neck, while the upper brittle crust is broken in blocks by faults, and the blocks sink down the thinned lower crust; if the stretching continues, the neck may break and a newly originated oceanic crust is formed at this place. The <span class="hlt">rift</span> <span class="hlt">system</span> structure depends on the depth of the boundary surface between the brittle crust and the ductile crust, the litospheric thickness, the tension value, etc.. The rigid brittle <span class="hlt">rifting</span> when narrow necks form in the lower crust is characteristic of the contemporary Earth; on Mars the brittle <span class="hlt">rifting</span> with large subsidence was characteristic of the Tharsis upland formation epoch. The ductile <span class="hlt">rifting</span> is typical of the Venus. The differences in rheologic features of the lithospheres of different planets causes the variation in types of <span class="hlt">rifting</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27402440','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27402440"><span>Arabidopsis thaliana plants expressing <span class="hlt">Rift</span> Valley fever virus antigens: Mice exhibit <span class="hlt">systemic</span> immune responses as the result of oral administration of the transgenic plants.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kalbina, Irina; Lagerqvist, Nina; Moiane, Bélisario; Ahlm, Clas; Andersson, Sören; Strid, Åke; Falk, Kerstin I</p> <p>2016-11-01</p> <p>The zoonotic <span class="hlt">Rift</span> Valley fever virus affects livestock and humans in Africa and on the Arabian Peninsula. The economic impact of this pathogen due to livestock losses, as well as its relevance to public health, underscores the importance of developing effective and easily distributed vaccines. Vaccines that can be delivered orally are of particular interest. Here, we report the expression in transformed plants (Arabidopsis thaliana) of <span class="hlt">Rift</span> Valley fever virus antigens. The antigens used in this study were the N protein and a deletion mutant of the Gn glycoprotein. Transformed lines were analysed for specific mRNA and protein content by RT-PCR and Western blotting, respectively. Furthermore, the plant-expressed antigens were evaluated for their immunogenicity in mice fed the transgenic plants. After oral intake of fresh transgenic plant material, a proportion of the mice elicited specific IgG antibody responses, as compared to the control animals that were fed wild-type plants and of which none sero-converted. Thus, we show that transgenic plants can be readily used to express and produce <span class="hlt">Rift</span> Valley Fever virus proteins, and that the plants are immunogenic when given orally to mice. These are promising findings and provide a basis for further studies on edible plant vaccines against the <span class="hlt">Rift</span> Valley fever virus.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=289622','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=289622"><span>Common host-derived chemicals increase catches of disease-transmitting mosquitoes and can improve early warning <span class="hlt">systems</span> for <span class="hlt">rift</span> valley fever virus</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p><span class="hlt">Rift</span> Valley fever (RVF), a mosquito-borne zoonosis, is a major public health problem in sub-Saharan Africa. The emergence and re-emergence of the disease in the last 20 years especially in East Africa, poses a looming health threat which is likely to spread to beyond Africa. This threat is exacerbat...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.5624T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.5624T"><span>The deep structure of Alpine-type orogens: how important is <span class="hlt">rift</span>-inheritance?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tugend, Julie; Manatschal, Gianreto; Mohn, Geoffroy</p> <p>2016-04-01</p> <p>Collisional belts are commonly thought to result from the closure of oceanic basins and subsequent inversion of former <span class="hlt">rifted</span> margins. The formation and evolution of collisional belts should therefore be closely interlinked with the initial architecture of former <span class="hlt">rifted</span> margins. Reflection and refraction seismic data from present-day magma-poor <span class="hlt">rifted</span> margins show the omnipresence of hyperextended domains (severely thinned continental crust (<10 km) and/or exhumed serpentinized mantle with minor magmatic additions) between unequivocal continental and oceanic domains. Integrating these new observations and exploring their impact on mountain building processes may result in alternative interpretations of the lithospheric structure of collisional orogens. We focus on the Pyrenees and Western to Central Alps, respectively resulting from the inversion of a Late Jurassic to Mid Cretaceous and an Early to Mid Jurassic <span class="hlt">rift</span> <span class="hlt">system</span> eventually floored by hyperextended crust, exhumed mantle or proto-oceanic crust. The <span class="hlt">rift</span>-related pre-collisional architecture of the Pyrenees shows many similarities with that proposed for the Alps; although the width of the hyperextended and in particular of the proto-oceanic domains is little constrained. Contrasting with the Pyrenees, remnants of these domains are largely affected by orogeny-related deformation and show a HP-LT to HT-MP metamorphic overprint in the Alps. Nevertheless, in spite of the occurrence of these highly deformed and metamorphosed rocks constituting the internal parts of the Alps, the overall crustal and lithospheric structure looks surprisingly comparable. High resolution tomographic images across both orogens unravel the occurrence of a velocity anomaly dipping underneath the internal domains and progressively attenuated at depth that we interpret as former hyperextended domains subducted/underthrusted during collision. This interpretation contrasts with the classical assumption that the subducted material is made of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1815572M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1815572M"><span>Magmatic cycles pace tectonic and morphological expression of <span class="hlt">rifting</span> (Afar depression, Ethiopia)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Medynski, Sarah; Pik, Raphael; Burnard, Peter; Blard, Pierre-Henri</p> <p>2016-04-01</p> <p>Dyking and faulting at mid-oceanic ridges are concentrated in narrow axial volcanic zones due to focussing of both melt distribution and tectonic strain along the plate boundary. Due to the predominantly submarine location of oceanic ridges, the interplay between these processes remain poorly constrained in time and space. In this study, we use the Dabbahu-Manda Hararo (DMH) magmatic <span class="hlt">rift</span> segment (MRS) (Afar, Ethiopia) to answers the long debated chicken-egg question about magmatic and tectonic processes in extensive context: which on comes first, and how those two processes interplay to <span class="hlt">finally</span> form oceanic ridges? The DMH MRS is an oceanic ridge analogue and here we present quantitative slip rates on major and minor normal fault scarps for the past 40 kyr in the vicinity of a recent (September 2005) dike intrusion. Our data show that the long-term-vertical slip rates of faults that ruptured in 2005 are too low to explain the present <span class="hlt">rift</span> topography and that the 2005 strain distribution is not the main stress accommodating mechanism in the DMH segment. Instead, we show that the axial valley topography is created by enhanced slip rates which occur only when the amount of magma available in magma reservoirs is limited, thus preventing dykes from reaching the surface. Our results suggest that development of the axial valley topography is regulated by the magma reservoir lifetime and, thus, to the magmatic cycles of replenishment/differentiation (< 100 ky). This implies that in the DMH <span class="hlt">rift</span> <span class="hlt">system</span> (with a magma supply typical of an intermediate spreading centre), significant topography of the axial <span class="hlt">rift</span> valley is transient, and is expressed only when magma available in the reservoirs decreases. The absence of tilting on the <span class="hlt">rift</span> margins over the last 200 kyr also suggests that amagmatic accommodation of extension is not required over this time period. Extension instead is accommodated by dykes injected laterally from multiple ephemeral reservoirs located along the DMH</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MinDe..51..937T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MinDe..51..937T"><span>Chalcophile element (Ni, Cu, PGE, and Au) variations in the Tamarack magmatic sulfide deposit in the Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span>: implications for dynamic ore-forming processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Taranovic, Valentina; Ripley, Edward M.; Li, Chusi; Rossell, Dean</p> <p>2016-10-01</p> <p>The Tamarack magmatic sulfide deposit is hosted by the Tamarack Intrusive Complex (1105.6 ± 1.2 Ma) in the Midcontinent <span class="hlt">Rift</span> <span class="hlt">System</span>. The most important sulfide mineralization in the Complex occurs in the northern part, which consists of two separate intrusive units: an early funnel-shaped layered peridotite body containing relatively fine-grained olivine (referred to as the FGO Intrusion) at the top, and a late gabbro-troctolite-peridotite dike-like body containing relatively coarse-grained olivine (referred to as the CGO Intrusion) at the bottom. Disseminated, net-textured, and massive sulfides occur in the base of the FGO Intrusion as well as in the upper part of the CGO Intrusion. The widest part of the CGO Intrusion also hosts a large semi-massive (net-textured) sulfide ore body locally surrounded by disseminated sulfide mineralization. Small massive sulfide veins occur in the footwall of the FGO Intrusion and in the wall rocks of the CGO dike. The sulfide mineralization is predominantly composed of pyrrhotite, pentlandite, and chalcopyrite, plus minor magnetite. Pyrrhotite containing the highest Ni and Co contents occurs in the FGO disseminated sulfides and in the CGO semi-massive sulfide ores, respectively. The most important platinum-group minerals associated with the base metal sulfides are sperrylite (PtAs2), sudburyite (PdSb), and michenerite (PdBiTe). Nickel shows a strong positive correlation with S in all types of sulfide mineralization, and Cu shows a strong positive correlation with S in the disseminated sulfide mineralization. At a given S content, the concentrations of Pt, Pd, and Au in the CGO disseminated sulfides are significantly higher than those in the FGO disseminated sulfides. The semi-massive sulfide ores are characterized by significantly higher IPGE (Ir, Os, Ru, and Rh) concentrations than most of the massive sulfide ores. With few exceptions, all of the various textural types of sulfide mineralization collectively show a good positive</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.9156M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.9156M"><span>Structural and stratigraphic evolution of the Iberia and Newfoundland hyper-extended <span class="hlt">rifted</span> margins: A quantitative modeling approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mohn, Geoffroy; Karner, Garry; Manatschal, Gianreto; Johnson, Christopher</p> <p>2014-05-01</p> <p><span class="hlt">Rifted</span> margins develop through polyphased extensional events leading eventually to break-up. Of particular interests are the stratigraphic and subsidence evolutions of these polyphased <span class="hlt">rift</span> events. In this contribution, we investigate the spatial and temporal evolution of the Iberia-Newfoundland <span class="hlt">rift</span> <span class="hlt">system</span> from the Permian, post-orogenic development of European crust to early Cretaceous break-up on the continental lithosphere between Iberia and Newfoundland. Based on seismic reflection and refraction and ODP drill data combined with a kinematic and flexural model for the deformation of the lithosphere, we explore the general tectono-stratigraphic evolution of Iberia-Newfoundland <span class="hlt">rift</span> <span class="hlt">system</span> and its relationship to repeated lithospheric thinning events. Our results emphasize the kinematic and isostatic interactions engendered by the distinct distribution, amplitude and depth-partitioning of extensional events that allowed the formation of the Iberia-Newfoundland <span class="hlt">rift</span> <span class="hlt">system</span>. The initial stratigraphic record is controlled by Permian, post-orogenic topographic erosion, lithospheric thinning, and its subsequent thermal re-equilibration that lead to a regional subsidence characterized by non-marine to marine sedimentation. During late Triassic and early Jurassic time, extensional deformation was characterized by broadly-distributed depth uniform thinning related to minor thinning of the crust. From the Late Jurassic onward, extensional deformation was progressively localized and associated with depth-dependent thinning that <span class="hlt">finally</span> lead to the formation of hyper-extended domains pre-dating the Late Aptian/Early Albian break-up of the Iberia-Newfoundland continental lithosphere. In particular, extension was diachronous, propagating in severity from south to north - while the southern Iberian margin was undergoing significant thinning in the Tithonian-early Berriasian, the northern margin (i.e., Galicia Bank) had yet to start <span class="hlt">rifting</span>. Break-up is likewise diachronous</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6832285','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6832285"><span>Solar heating <span class="hlt">system</span> installed at Troy, Ohio. <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p></p> <p>1980-09-01</p> <p>This document is the <span class="hlt">Final</span> Report of the Solar Energy <span class="hlt">System</span> located at Troy-Miami County Public Library, Troy, Ohio. The completed <span class="hlt">system</span> is composed of tree basic subsystems: the collector <span class="hlt">system</span> consisting of 3264 square feet of Owens Illinois evacuated glass tube collectors; the storage <span class="hlt">system</span> which includes a 5000-gallon insulated steel tank; and the distribution and control <span class="hlt">system</span> which includes piping, pumping and control logic for the efficient and safe operation of the entire <span class="hlt">system</span>. This solar heating <span class="hlt">system</span> was installed in an existing facility and is, therefore, a retrofit <span class="hlt">system</span>. This report includes extracts from the site files, specifications, drawings, installation, operation and maintenance instructions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GGG....16.2949C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GGG....16.2949C"><span>Multiple mantle upwellings in the transition zone beneath the northern East-African <span class="hlt">Rift</span> <span class="hlt">system</span> from relative P-wave travel-time tomography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Civiero, Chiara; Hammond, James O. S.; Goes, Saskia; Fishwick, Stewart; Ahmed, Abdulhakim; Ayele, Atalay; Doubre, Cecile; Goitom, Berhe; Keir, Derek; Kendall, J.-Michael; Leroy, Sylvie; Ogubazghi, Ghebrebrhan; Rümpker, Georg; Stuart, Graham W.</p> <p>2015-09-01</p> <p>Mantle plumes and consequent plate extension have been invoked as the likely cause of East African <span class="hlt">Rift</span> volcanism. However, the nature of mantle upwelling is debated, with proposed configurations ranging from a single broad plume connected to the large low-shear-velocity province beneath Southern Africa, the so-called African Superplume, to multiple lower-mantle sources along the <span class="hlt">rift</span>. We present a new P-wave travel-time tomography model below the northern East-African, Red Sea, and Gulf of Aden <span class="hlt">rifts</span> and surrounding areas. Data are from stations that span an area from Madagascar to Saudi Arabia. The aperture of the integrated data set allows us to image structures of ˜100 km length-scale down to depths of 700-800 km beneath the study region. Our images provide evidence of two clusters of low-velocity structures consisting of features with diameter of 100-200 km that extend through the transition zone, the first beneath Afar and a second just west of the Main Ethiopian <span class="hlt">Rift</span>, a region with off-<span class="hlt">rift</span> volcanism. Considering seismic sensitivity to temperature, we interpret these features as upwellings with excess temperatures of 100 ± 50 K. The scale of the upwellings is smaller than expected for lower mantle plume sources. This, together with the change in pattern of the low-velocity anomalies across the base of the transition zone, suggests that ponding or flow of deep-plume material below the transition zone may be spawning these upper mantle upwellings. This article was corrected on 28 SEP 2015. See the end of the full text for details.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160005862','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160005862"><span>Diverse Eruptions at Approximately 2,200 Years B.P. on the Great <span class="hlt">Rift</span>, Idaho: Inferences for Magma Dynamics Along Volcanic <span class="hlt">Rift</span> Zones</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hughes, S. S.; Nawotniak, S. E. Kobs; Borg, C.; Mallonee, H. C.; Purcell, S.; Neish, C.; Garry, W. B.; Haberle, C. W.; Lim, D. S. S.; Heldmann, J. L.</p> <p>2016-01-01</p> <p>Compositionally and morphologically diverse lava flows erupted on the Great <span class="hlt">Rift</span> of Idaho approximately 2.2 ka (kilo-annum, 1000 years ago) during a volcanic "flare-up" of activity following an approximately 2 ky (kiloyear, 1000 years) hiatus in eruptions. Volcanism at Craters of the Moon (COTM), Wapi and Kings Bowl lava fields around this time included primitive and evolved compositions, separated over 75 kilometers along the approximately 85 kilometers-long <span class="hlt">rift</span>, with striking variability in lava flow emplacement mechanisms and surface morphologies. Although the temporal associations may be coincidental, the <span class="hlt">system</span> provides a planetary analog to better understand magma dynamics along <span class="hlt">rift</span> <span class="hlt">systems</span>, including that associated with lunar floor-fractured craters. This study aims to help bridge the knowledge gap between ancient <span class="hlt">rift</span> volcanism evident on the Moon and other terrestrial planets, and active <span class="hlt">rift</span> volcanism, e.g., at Hawai'i and Iceland.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21295425','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21295425"><span>[<span class="hlt">Rift</span> Valley fever].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pépin, M</p> <p>2011-06-01</p> <p><span class="hlt">Rift</span> Valley Fever (RVF) is a zoonotic arbovirosis. Among animals, it mainly affects ruminants, causing abortions in gravid females and mortality among young animals. In humans, RVF virus infection is usually asymptomatic or characterized by a moderate fever. However, in 1 to 3% of cases, more severe forms of the disease (hepatitis, encephalitis, retinitis, hemorrhagic fever) can lead to the death of infected individuals or to major sequels. The RVF virus (Bunyaviridae, genus Phlebovirus) was identified for the first time in the 1930s in Kenya. It then spread over almost all African countries, sometimes causing major epizootics/epidemics. In 2000, the virus was carried out of Africa, in the Middle East Arabian Peninsula. In 2007-2008, Eastern-African countries, including Madagascar, reported significant episodes of RVF virus, this was also the case for the Comoros archipelago and the French island of Mayotte. This ability to spread associated with many vectors, including in Europe, and high viral loads in infected animals led the health authorities worldwide to warn about the potential emergence of RVF virus in areas with a temperate climate. The awareness has increased in recent years with climate changes, which may possibly modify the vector distribution and competence, and prompted many RVF virus-free countries to better prepare for a potential implantation of RVF.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=214205','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=214205"><span>GIS Early-Warning <span class="hlt">System</span> for Vectors of <span class="hlt">Rift</span> Valley Fever: Anomaly Analysis of Climate-Population Associations</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>A critical component of predicting the risk of transmission of mosquito-borne viruses is knowing the status of vector populations. Mosquito control agencies have good <span class="hlt">systems</span> for measuring mosquito populations at county or district levels, but these data are not synthesized to regional or national ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMOS21C1526C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMOS21C1526C"><span>Investigation of Icelandic <span class="hlt">rift</span> zones reveals systematic changes in hydrothermal outflow in concert with seismic and magmatic events: Implications for investigation of Mid-Ocean Ridge hydrothermal <span class="hlt">systems</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Curewitz, D.; Karson, J. A.</p> <p>2010-12-01</p> <p>Co-registration of several generations of geological data was carried out for hydrothermal fields along active <span class="hlt">rift</span> zones of the Iceland plate boundary zone. Significant short- and long-term changes in vent locations, flow rates and styles, and fluid characteristics over short periods take place in concert with recorded earthquakes, dike intrusions, and fissure eruptions. Higher resolution, more detailed analysis of the Icelandic hydrothermal sites will inform investigation of similar data from mid-ocean ridge hydrothermal <span class="hlt">systems</span> along the RIDGE 2000 focus sites. Initial results from the Hengill and Krafla geothermal areas covering a time-span of nearly 40 years at ~10 year intervals reveal limited changes in the surface expression of fault populations, with the exception of local fault and fracture <span class="hlt">systems</span>. The location and population density of individual vents and groups of vents underwent significant changes over the same time period, with either vents shifting location, or new vents opening and old vents closing. Registration of changes in vent fluid temperatures, vent field ground temperatures, fluid flow rates, and vent eruptive styles reveal changes in hydrothermal flow systematics in concert with the observed changes in vent location and vent population density. Significant local seismic and volcanological events (earthquakes, earthquake swarms, dike intrusions, eruptions, inflation/deflation) that are potential triggers for the observed changes take place in intervening years between production of successive maps. Changes in modeled stress intensities and local fracture/fault density and geometry associated with these tectono-magmatic events correspond well to inferred locations of increased or decreased shallow permeability thought to control hydrothermal outflow behavior. Recent seismic events are strongly linked to well-mapped changes in fracture/fault population and hydrothermal flow behavior in the Hveragerdi region, near Hengill, and provide higher</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1987Tectp.133..257W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1987Tectp.133..257W"><span>The Fenwei <span class="hlt">rift</span> and its recent periodic activity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Jing-Ming</p> <p>1987-02-01</p> <p>The Fenwei <span class="hlt">rift</span> on the southern sector of the Jin—Shaan <span class="hlt">rift</span> <span class="hlt">system</span> of China is marked by a crescent-shaped valley 600 km in length and 30-90 km in width depressed up to 10 km and filled with about 7000 m of Cenozoic deposits, bounded on both northern and southern sides by majestic mountain ranges. The geometry of the <span class="hlt">rift</span> valley is characterized by six branch depressions and five intervening swells extending east-northeastward in a dextral en-echelon pattern and bounded on both sides by abrupt topographic slopes reflecting the underlying faults. These are typically a <span class="hlt">system</span> of growth faults having downthrows ranging from 800 m to 10 km and dipping toward the centre of the valley forming an asymmetric graben structure. The geometry, kinematics and evolution of these faults have had controlling influences on the neotectonic movement of the <span class="hlt">rift</span> and its recent periodic activity as the present overall form of the <span class="hlt">rift</span> valley. Estimates of the amount of extension across the <span class="hlt">rift</span> for various recent geological periods were obtained from calculations made on the fault separation of corresponding stratigraphie horizons. The total amount of extension in response to tensile stresses, acting in a direction varying from 25° NW on the west to 70° NW on the northeast is estimated to be 9065 m, since the beginning of the <span class="hlt">rift</span> formation in the Eocene whereas the rate of extension in the Recent is 4.5 mm/yr and in modern times it is 8-24 mm/yr. The amount of left-lateral displacement across the <span class="hlt">rift</span> during various stages of its development was also calculated from the observed effects of strike-slip movement on the drainage <span class="hlt">system</span>. The left-lateral offset since the mid-Pleistocene is approximately 7170 m and the offset rate in modern times is 6 mm/yr. These estimates suggest that the Fenwei <span class="hlt">rift</span> has been a place of intense neotectonic activity. Details of more recent activity of the <span class="hlt">rift</span> were investigated in terms of the various <span class="hlt">rift</span>-related phenomena such as seismic events</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986E%26PSL..77..176M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986E%26PSL..77..176M"><span>The geometry of propagating <span class="hlt">rifts</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McKenzie, Dan</p> <p>1986-03-01</p> <p>The kinematics of two different processes are investigated, both of which have been described as <span class="hlt">rift</span> propagation. Courtillot uses this term to describe the change from distributed to localised extension which occurs during the early development of an ocean basin. The term localisation is instead used here to describe this process, to distinguish it from Hey's type of propagation. Localisation generally leads to rotation of the direction of magnetisation. To Hey propagation means the extension of a <span class="hlt">rift</span> into the undeformed plate beyond a transform fault. Detail surveys of the Galapagos <span class="hlt">rift</span> have shown that the propagating and failing <span class="hlt">rifts</span> are not connected by a single transform fault, but by a zone which is undergoing shear. The principal deformation is simple shear, and the kinematics of this deformation are investigated in some detail. The strike of most of the lineations observed in the area can be produced by such deformation. The mode of extension on the propagating <span class="hlt">rift</span> appears to be localised for some periods but to be distributed for others. Neither simple kinematic arguments nor stretching of the lithosphere with conservation of crust can account for the observed variations in water depth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70134359','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70134359"><span><span class="hlt">Rift</span> flank segmentation, basin initiation and propagation: a neotectonic example from Lake Baikal</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Agar, S.M.; Klitgord, Kim D.</p> <p>1995-01-01</p> <p>New surficial data (field, Landsat TM and topography) define morpho-tectonic domains and <span class="hlt">rift</span> flank segmentation in the Ol'khon region of the Central Baikal <span class="hlt">rift</span>. Deformation, drainage and depositional patterns indicate a change in the locus of active extension that may relate to a recent (<l Ma) change in the kinematics of the Siberian plate boundary. The westwards migration of the border fault location has broadened the <span class="hlt">rift</span> with concomitant shifts in depocentres. Within the hanging wall of the new western border fault, distinct segments control the location of drainage paths and syn-<span class="hlt">rift</span> deposits. Morphology, sediment thicknesses and fault scarp amplitude indicate that a segmented <span class="hlt">rift</span> flank graben has propagated southwards along the <span class="hlt">rift</span> flank and is still actively fragmenting. These surficial data are used to constrain a model for the time-dependent topographic variations during progressive subsidence along a <span class="hlt">rift</span> flank, involving the transfer of footwall units to hanging-wall domains. Rapid changes in border fault footwall relief in this model are associated with change in the active border fault location with widespread mass-wasting. The model shows that time-dependent histories need to be integrated with flexural uplift models for active normal faults. The active, syn-<span class="hlt">rift</span> depositional <span class="hlt">systems</span> of the Ol'khon region provide a valuable analogue for the early evolution of continental margins and the structural controls on syn-<span class="hlt">rift</span> hydrocarbon sources and reservoirs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T51G3008G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T51G3008G"><span>Seismological Investigations of Crustal and Mantle Structures Beneath the Incipient Okavango <span class="hlt">Rift</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gao, S. S.; Yu, Y.; Liu, K. H.; Reed, C. A.; Moidaki, M.; Mickus, K. L.; Atekwana, E. A.</p> <p>2015-12-01</p> <p><span class="hlt">Rifting</span> plays a significant role in the evolution of sedimentary basins. However, our current understandings on <span class="hlt">rifting</span> mechanisms are mostly based on studies of mature <span class="hlt">rifts</span>. Here we report results from the first teleseismic investigations of the incipient Okavango <span class="hlt">rift</span> zone (ORZ), which is located at the southwestern terminal of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> in northern Botswana. Data used in the study were recorded by the 17 broadband seismic stations deployed along a NW-SE profile traversing the ORZ with a recording duration of 2 years starting in the summer of 2012. Receiver function and shear wave splitting techniques have been employed to explore upper mantle thermal anomalies and anisotropy. The resulting dominantly absolute plate motion-parallel fast polarization orientations and normal mantle transition zone thickness ruled out the possible existence of one or more mantle plumes in the upper mantle or mantle transition zone beneath the ORZ. The Moho beneath the Okavango <span class="hlt">rift</span> zone is uplifted by 4-5 km and is symmetric with regard to the <span class="hlt">rift</span> axis, favoring a pure shear model of early-stage continental extension. The observations favor a passive model for <span class="hlt">rift</span> initiation in which <span class="hlt">rifts</span> develop inside ancient orogenic zones as the result of relative movements between Archean cratonic blocks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/799225','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/799225"><span>Field Studies of Geothermal Reservoirs Rio Grande <span class="hlt">Rift</span>, New Mexico</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>James C Witcher</p> <p>2002-07-30</p> <p>The Rio Grande <span class="hlt">rift</span> provides an excellent field laboratory to study the nature of geothermal <span class="hlt">systems</span> in an extensional environment. Much of the geologic complexity that is found in the Basin and Range is absent because the <span class="hlt">rift</span> is located on cratonic crust with a thin and well-characterized Phanerozoic stratigraphy and tectonic history. On the other hand, the Neogene thermo-tectonic history of the <span class="hlt">rift</span> has many parallels with the Basin and Range to the west. The geology of the southern Rio Grande <span class="hlt">rift</span> is among the best characterized of any <span class="hlt">rift</span> <span class="hlt">system</span> in the world. Also, most geologic maps for the region are rather unique in that detailed analyses of Quaternary stratigraphic and surficial unit are added in concert with the details of bedrock geology. Pleistocene to Holocene entrenchment of the Rio Grande and tributaries unroofs the alteration signatures and permeability attributes of paleo outflow plumes and upflow zones, associated with present-day, but hidden or ''blind,'' hydrothermal <span class="hlt">systems</span> at Rincon and San Diego Mountain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790011284','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790011284"><span><span class="hlt">Final</span> <span class="hlt">system</span> instrumentation design package for Decade 80 solar house</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1978-01-01</p> <p>The <span class="hlt">final</span> configuration of the Decade 80 solar house to monitor and collect <span class="hlt">system</span> performance data is presented. A review demonstrated by actual operation that the <span class="hlt">system</span> and the data acquisition subsystem operated satisfactorily and installation of instrumentation was in accordance with the design. This design package is made up of (1) site and <span class="hlt">system</span> description, (2) operating and control modes, and (3) instrumentation program (including sensor schematic).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T51H..06F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T51H..06F"><span>The MOZART Project - MOZAmbique <span class="hlt">Rift</span> Tomography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fonseca, J. F.; Chamussa, J. R.; Domingues, A.; Helffrich, G. R.; Fishwick, S.; Ferreira, A. M.; Custodio, S.; Brisbourne, A. M.; Grobbelaar, M.</p> <p>2012-12-01</p> <p>Project MOZART (MOZAmbique <span class="hlt">Rift</span> Tomography) is an ongoing joint effort of Portuguese, Mozambican and British research groups to investigate the geological structure and current tectonic activity of the southernmost tip of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS) through the deployment of a network of 30 broad band seismic stations in Central and Southern Mozambique. In contrast with other stretches of the EARS to the North and with the Kapvaal craton to the West and South, the lithosphere of Mozambique was not previously studied with a dense seismographic deployment on account of past political instability, and many questions remain unanswered with respect to the location and characteristics of the EARS to the south of Tanzania. In recent years, space geodesy revealed the existence of three microplates in and off Mozambique - Victoria, Rovuma, Lwandle - whose borders provide a connection of the EARS to the South West Indian Ridge as required by plate tectonics. However, the picture is still coarse concerning the location of the <span class="hlt">rift</span> structures. The 2006 M7 Machaze earthquake in Central Mozambique highlighted the current tectonic activity of the region and added a further clue to the location of the continental <span class="hlt">rift</span>, prompting the MOZART deployment. Besides helping unravel the current tectonics, the project is expected to shed light on the poorly known Mesoproterozoic structure described by Arthur Holmes in 1951 as the Mozambique Belt, and on the mechanisms of transition from stable craton to <span class="hlt">rifted</span> continental crust, through the development of a tomographic model for the lithosphere. The MOZART network is distributed South of the Zambezi river at average inter-station spaces of the order of 100 km and includes four stations across the border in South Africa. Data exchange was agreed with AfricaArray. The deployment proceeded in two phases in March 2011, and November and December 2011. Decommissioning is foreseen for August 2013. We report preliminary results for this</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70020868','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70020868"><span>Comparative sequence stratigraphy of low-latitude versus high-latitude lacustrine <span class="hlt">rift</span> basins: Seismic data examples from the East African and Baikal <span class="hlt">rifts</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Scholz, C.A.; Moore, T.C.; Hutchinson, D.R.; Golmshtok, A. Ja; Klitgord, Kim D.; Kurotchkin, A.G.</p> <p>1998-01-01</p> <p>Lakes Baikal, Malawi and Tanganyika are the world's three largest <span class="hlt">rift</span> valley lakes and are the classic modem examples of lacustrine <span class="hlt">rift</span> basins. All the <span class="hlt">rift</span> lakes are segmented into half-graben basins, and seismic reflection datasets reveal how this segmentation controls the filling of the <span class="hlt">rift</span> basins through time. In the early stages of <span class="hlt">rifting</span>, basins are fed primarily by flexural margin and axial margin drainage <span class="hlt">systems</span>. At the climax of syn-<span class="hlt">rift</span> sedimentation, however, when the basins are deeply subsided, almost all the margins are walled off by <span class="hlt">rift</span> shoulder uplifts, and sediment flux into the basins is concentrated at accommodation zone and axial margin river deltas. Flexural margin unconformities are commonplace in the tropical lakes but less so in high-latitude Lake Baikal. Lake levels are extremely dynamic in the tropical lakes and in low-latitude <span class="hlt">systems</span> in general because of the predominance of evaporation in the hydrologic cycle in those <span class="hlt">systems</span>. Evaporation is minimized in relation to inflow in the high-latitude Lake Baikal and in most high-latitude <span class="hlt">systems</span>, and consequently, major sequence boundaries tend to be tectonically controlled in that type of <span class="hlt">system</span>. The acoustic stratigraphies of the tropical lakes are dominated by high-frequency and high-amplitude lake level shifts, whereas in high-latitude Lake Baikal, stratigraphic cycles are dominated by tectonism and sediment-supply variations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5465920','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5465920"><span>Thermal maturation and organic richness of potential petroleum source rocks in Proterozoic Rice Formation, North American Mid-Continent <span class="hlt">rift</span> <span class="hlt">system</span>, northeastern Kansas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Newell, K.D. ); Burruss, R.C.; Palacas, J.G. )</p> <p>1993-11-01</p> <p>A recent well in northeastern Kansas penetrated 296 ft (90.2 m) of dark gray siltstone in the Precambrian Mid-Continent <span class="hlt">rift</span> (Proterozoic Rice Formation). Correlations indicate this unit may be as thick as 600 ft (183 m) and is possibly time-equivalent to the Nonesuch Shale (Middle Proterozoic) in the Lake Superior region. The upper half of this unit qualifies as a lean source rock (averaging 0.66 wt.% TOC), and organic matter in it is in the transition stage between oil and wet gas generation. The presence of the gray siltstone in this well and similar lithologies in other wells is encouraging because it indicates the source rock deposition may be common along the Mid-Continent <span class="hlt">rift</span>, and that parts of the <span class="hlt">rift</span> may remain thermally within the oil and gas window. Microscopic examination of calcite veins penetrating the dark gray siltstone reveals numerous oil-filled and subordinate aqueous fluid inclusions. Homogenization temperatures indicate these rocks have been subjected to temperature of at least 110-115[degrees]C (230-239[degrees]F). Burial during the Phanerozoic is inadequate to account for the homogenization temperatures and thermal maturity of the Precambrian rocks. With the present geothermal gradient, at least 8250 ft (2.5 km) of burial is necessary, but lesser burial may be likely with probably higher geothermal gradients during <span class="hlt">rifting</span>. Fluorescence colors and gas chromatograms indicate compositions of oils in the fluid inclusions vary. However, oils in the fluid inclusions are markedly dissimilar to the nearest oils produced from Paleozoic rocks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70025197','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70025197"><span>Kilauea east <span class="hlt">rift</span> zone magmatism: An episode 54 perspective</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Thornber, C.R.; Heliker, C.; Sherrod, D.R.; Kauahikaua, J.P.; Miklius, Asta; Okubo, P.G.; Trusdell, F.A.; Budahn, J.R.; Ridley, W.I.; Meeker, G.P.</p> <p>2003-01-01</p> <p>On January 29 30, 1997, prolonged steady-state effusion of lava from Pu'u'O'o was briefly disrupted by shallow extension beneath Napau Crater, 1 4 km uprift of the active Kilauea vent. A 23-h-long eruption (episode 54) ensued from fissures that were overlapping or en echelon with eruptive fissures formed during episode 1 in 1983 and those of earlier <span class="hlt">rift</span> zone eruptions in 1963 and 1968. Combined geophysical and petrologic data for the 1994 1999 eruptive interval, including episode 54, reveal a variety of shallow magmatic conditions that persist in association with prolonged <span class="hlt">rift</span> zone eruption. Near-vent lava samples document a significant range in composition, temperature and crystallinity of pre-eruptive magma. As supported by phenocryst liquid relations and Kilauea mineral thermometers established herein, the <span class="hlt">rift</span> zone extension that led to episode 54 resulted in mixture of near-cotectic magma with discrete magma bodies cooled to ???1100??C. Mixing models indicate that magmas isolated beneath Napau Crater since 1963 and 1968 constituted 32 65% of the hybrid mixtures erupted during episode 54. Geophysical measurements support passive displacement of open-<span class="hlt">system</span> magma along the active east <span class="hlt">rift</span> conduit into closed-<span class="hlt">system</span> <span class="hlt">rift</span>-reservoirs along a shallow zone of extension. Geophysical and petrologic data for early episode 55 document the gradual flushing of episode 54 related magma during magmatic recharge of the edifice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007QSRv...26.1771H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007QSRv...26.1771H"><span>Anatomy of a river drainage reversal in the Neogene Kivu Nile <span class="hlt">Rift</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Holzförster, F.; Schmidt, U.</p> <p>2007-07-01</p> <p>The Neogene geological history of East Africa is characterised by the doming and extension in the course of development of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> with its eastern and western branches. In the centre of the Western <span class="hlt">Rift</span> Rise Rwanda is situated on Proterozoic basement rocks exposed in the strongly uplifted eastern <span class="hlt">rift</span> shoulder of the Kivu-Nile <span class="hlt">Rift</span> segment, where clastic sedimentation is largely restricted to the <span class="hlt">rift</span> axis itself. A small, volcanically and tectonically controlled depository in northwestern Rwanda preserved the only Neogene sediments known from the extremely uplifted <span class="hlt">rift</span> shoulder. Those (?)Pliocene to Pleistocene/Holocene fluvio-lacustrine muds and sands of the Palaeo-Nyabarongo River record the influence of Virunga volcanism on the major drainage reversal that affected East Africa in the Plio-/Pleistocene, when the originally <span class="hlt">rift</span>-parallel upper Nile drainage <span class="hlt">system</span> became diverted to the East in order to enter the Nile <span class="hlt">system</span> via Lake Victoria. Sedimentary facies development, heavy mineral distributions and palaeobiological controls, including hominid artefacts, signal a short time interval of <300-350 ka to complete this major event for the sediment supply <span class="hlt">system</span> of the Kivu-Nile <span class="hlt">Rift</span> segment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19810056997&hterms=Continental+Drift&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DContinental%2BDrift','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19810056997&hterms=Continental+Drift&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DContinental%2BDrift"><span>Continental <span class="hlt">rifting</span> and the origin of Beta Regio, Venus</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mcgill, G. E.; Steenstrup, S. J.; Barton, C.; Ford, P. G.</p> <p>1981-01-01</p> <p>Topographic maps based on Pioneer Venus altimetry suggest that Beta Regio, an elevated feature centered at 27 deg N, 282 deg E, is analogous to domes associated with continental <span class="hlt">rift</span> <span class="hlt">systems</span> on earth. This interpretation is consistent with the commonly quoted analogy between the East African <span class="hlt">rift</span> <span class="hlt">system</span> and the topography of the region from Beta Regio southward to Phoebe Regio. If Beta Regio is a dome, major structural uplift of the crust of Venus is implied, suggesting a more dynamic upper mantle than would be the case if Beta Regio were simply a large volcanic construct.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70074654','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70074654"><span>Seismicity within a propagating ice shelf <span class="hlt">rift</span>: the relationship between icequake locations and ice shelf structure</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Heeszel, David S.; Fricker, Helen A.; Bassis, Jeremy N.; O'Neel, Shad; Walter, Fabian</p> <p>2014-01-01</p> <p>Iceberg calving is a dominant mass loss mechanism for Antarctic ice shelves, second only to basal melting. An important known process involved in calving is the initiation and propagation of through-penetrating fractures called <span class="hlt">rifts</span>; however, the mechanisms controlling <span class="hlt">rift</span> propagation remain poorly understood. To investigate the mechanics of ice-shelf <span class="hlt">rifting</span>, we analyzed seismicity associated with a propagating <span class="hlt">rift</span> tip on the Amery Ice Shelf, using data collected during the Austral summers of 2004-2007. We investigated seismicity associated with fracture propagation using a suite of passive seismological techniques including icequake locations, back projection, and moment tensor inversion. We confirm previous results that show that seismicity is characterized by periods of relative quiescence punctuated by swarms of intense seismicity of one to three hours. However, even during periods of quiescence, we find significant seismic deformation around the <span class="hlt">rift</span> tip. Moment tensors, calculated for a subset of the largest icequakes (MW > -2.0) located near the <span class="hlt">rift</span> tip, show steeply dipping fault planes, horizontal or shallowly plunging stress orientations, and often have a significant volumetric component. They also reveal that much of the observed seismicity is limited to the upper 50 m of the ice shelf. This suggests a complex <span class="hlt">system</span> of deformation that involves the propagating <span class="hlt">rift</span>, the region behind the <span class="hlt">rift</span> tip, and a <span class="hlt">system</span> of <span class="hlt">rift</span>-transverse crevasses. Small-scale variations in the mechanical structure of the ice shelf, especially <span class="hlt">rift</span>-transverse crevasses and accreted marine ice, play an important role in modulating the rate and location of seismicity associated with propagating ice shelf <span class="hlt">rifts</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T51F2965S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T51F2965S"><span>Neogene Development of the Terror <span class="hlt">Rift</span>, western Ross Sea, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sauli, C.; Sorlien, C. C.; Busetti, M.; De Santis, L.; Wardell, N.; Henrys, S. A.; Geletti, R.; Wilson, T. J.; Luyendyk, B. P.</p> <p>2015-12-01</p> <p>Terror <span class="hlt">Rift</span> is a >300 km-long, 50-70 km-wide, 14 km-deep sedimentary basin at the edge of the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span>, adjacent to the Transantarctic Mountains. It is cut into the broader Victoria Land Basin (VLB). The VLB experienced 100 km of mid-Cenozoic extension associated with larger sea floor spreading farther north. The post-spreading (Neogene) development of Terror <span class="hlt">Rift</span> is not well understood, in part because of past use of different stratigraphic age models. We use the new Rossmap seismic stratigraphy correlated to Cape Roberts and Andrill cores in the west and to DSDP cores in the distant East. This stratigraphy, and new fault interpretations, was developed using different resolutions of seismic reflection data included those available from the Seismic Data Library <span class="hlt">System</span>. Depth conversion used a new 3D velocity model. A 29 Ma horizon is as deep as 8 km in the south, and a 19 Ma horizon is >5 km deep there and 4 km-deep 100 km farther north. There is a shallower northern part of Terror <span class="hlt">Rift</span> misaligned with the southern basin across a 50 km right double bend. It is bounded by steep N-S faults down-dropping towards the basin axis. Between Cape Roberts and Ross Island, the Oligocene section is also progressively-tilted. This Oligocene section is not imaged within northern Terror <span class="hlt">Rift</span>, but the simplest hypothesis is that some of the Terror <span class="hlt">Rift</span>-bounding faults were active at least during Oligocene through Quaternary time. Many faults are normal separation, but some are locally vertical or even reverse-separation in the upper couple of km. However, much of the vertical relief of the strata is due to progressive tilting (horizontal axis rotation) and not by shallow faulting. Along the trend of the basin, the relief alternates between tilting and faulting, with a tilting margin facing a faulted margin across the <span class="hlt">Rift</span>, forming asymmetric basins. Connecting faults across the basin form an accommodation zone similar to other oblique <span class="hlt">rifts</span>. The Neogene basin is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6286417','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6286417"><span>Beam dynamics in the SLC <span class="hlt">final</span> focus <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bambade, P.S.</p> <p>1987-06-01</p> <p>The SLC luminosity is reached by colliding beams focused to about 2 ..mu..m transverse sizes. The <span class="hlt">Final</span> Focus <span class="hlt">System</span> (FFS) must enable, beyond its basic optical design, the detection and correction of errors accumulated in the <span class="hlt">system</span>. In this paper, after summarizing the design, we review the sensitivity to such errors and the ability to correct them. The overall tuning strategy involves three phases: single beam spot minimization, steering the beams in collision and luminosity optimization with beam-beam effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.T41E1260D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.T41E1260D"><span>Seismological Constraints on the Magmato-tectonic Behavior of the Asal-Ghoubbet <span class="hlt">Rift</span> (Afar Depression, Republic of Djibouti) Since the Last 1978-<span class="hlt">Rifting</span> Episode</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Doubre, C.; Manighetti, I.; Bertil, D.; Dorbath, C.; Dorbath, L.; Jacques, E.</p> <p>2004-12-01</p> <p>The Asal-Ghoubbet <span class="hlt">rift</span> was the locus of a seismic and volcanic crisis in 1978 followed by 8 years of rapid opening (60 mm/yr) before returning to its long-term opening rate of 16 mm/yr. We analyze the space-time evolution of the seismicity that occurred in the <span class="hlt">rift</span> between 1979 and 2001. The data recorded by the Djibouti Observatory provide only hypocentral locations before 1995 and P and S-wave arrival times since 1996. Additional data acquired during a five months experiment in 2000-2001 allowed us to determine a 3D-velocity model of the <span class="hlt">rift</span>, used to precisely relocate post 1996 events. The 2545 small-magnitude earthquakes (Md ≤ 3.2) recorded in the <span class="hlt">rift</span> since the 1978 crisis provide a negligible contribution to the total extension across the <span class="hlt">rift</span>, which occurs essentially aseismically. The temporal evolution of the seismicity reveals two distinct phases consistent with those observed in the geodetic data. The post-crisis period (1979-1986) is characterized by large-magnitude earthquakes exclusively located below the northern <span class="hlt">rift</span> shoulder. These events are associated with the contraction of the side of the <span class="hlt">rift</span> resulting from the fast opening of the central dyke <span class="hlt">system</span>. The subsequent period (1987-2001) corresponding to normal opening rate across the <span class="hlt">rift</span> is characterized by a micro-seismicity essentially located below the major <span class="hlt">rift</span> caldera (Fieale). Most recorded events during this period concentrate within the <span class="hlt">rift</span> inner floor at the top of an aseismic, low velocity zone located below the Fiale caldera, which we interpret as hot material above the magma chamber. Outside from post-crisis periods, the seismicity tends to cluster in time in response to stress changes in the brittle layer induced by episodic magmatic movements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22094700','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22094700"><span>East Antarctic <span class="hlt">rifting</span> triggers uplift of the Gamburtsev Mountains.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ferraccioli, Fausto; Finn, Carol A; Jordan, Tom A; Bell, Robin E; Anderson, Lester M; Damaske, Detlef</p> <p>2011-11-16</p> <p>The Gamburtsev Subglacial Mountains are the least understood tectonic feature on Earth, because they are completely hidden beneath the East Antarctic Ice Sheet. Their high elevation and youthful Alpine topography, combined with their location on the East Antarctic craton, creates a paradox that has puzzled researchers since the mountains were discovered in 1958. The preservation of Alpine topography in the Gamburtsevs may reflect extremely low long-term erosion rates beneath the ice sheet, but the mountains' origin remains problematic. Here we present the first comprehensive view of the crustal architecture and uplift mechanisms for the Gamburtsevs, derived from radar, gravity and magnetic data. The geophysical data define a 2,500-km-long <span class="hlt">rift</span> <span class="hlt">system</span> in East Antarctica surrounding the Gamburtsevs, and a thick crustal root beneath the range. We propose that the root formed during the Proterozoic assembly of interior East Antarctica (possibly about 1 Gyr ago), was preserved as in some old orogens and was rejuvenated during much later Permian (roughly 250 Myr ago) and Cretaceous (roughly 100 Myr ago) <span class="hlt">rifting</span>. Much like East Africa, the interior of East Antarctica is a mosaic of Precambrian provinces affected by <span class="hlt">rifting</span> processes. Our models show that the combination of <span class="hlt">rift</span>-flank uplift, root buoyancy and the isostatic response to fluvial and glacial erosion explains the high elevation and relief of the Gamburtsevs. The evolution of the Gamburtsevs demonstrates that <span class="hlt">rifting</span> and preserved orogenic roots can produce broad regions of high topography in continental interiors without significantly modifying the underlying Precambrian lithosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6887650','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6887650"><span>Episodic <span class="hlt">rifting</span> and subsidence in the South China sea</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ru, K.; Pigott, J.D.</p> <p>1986-09-01</p> <p>The South China Sea experienced at least three stages of <span class="hlt">rifting</span> and two intervening stages of sea-floor spreading since the Early Cretaceous. Its evolution can be described by an episodic model of tectonism, one of thermal cooling and subsidence, pulsed by temporally and spatially confined heating events. Analysis of regional geologic and geophysical data suggests episodes of <span class="hlt">rifting</span> and associated thermal activities initiated during the Late Cretaceous, the late Eocene, and the late early Miocene. The <span class="hlt">rift</span> <span class="hlt">system</span> corresponding to the first episode trends northeast-southwest, whereas those of the second and third trend east-west. These two trends coincide with the orientations of the major tectonic lineations within the basin. Age estimates from heat-flow and bathymetric data suggest the oceanic crust in the Southwest subbasin is considerably older (55 Ma) than that in the Northwest (35-36 Ma) or East (32 Ma) subbasins. In terms of hydrocarbon potential, the episodes of <span class="hlt">rifting</span> and drifting would be conducive to the development of overprinted structures and the deposition of several discrete transgressive packages of source rocks and reservoirs, separated by widespread unconformities. The thermal maturity of sedimentary organic matter affected by episodic <span class="hlt">rifting</span> and subsidence may be greater than expected on a purely passive margin of equivalent age that had not experienced repeated heating. 21 figures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70016969','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70016969"><span>Speculations on the origin of the North American Midcontinent <span class="hlt">rift</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Cannon, W.F.; Hinze, W. J.</p> <p>1992-01-01</p> <p>The Midcontinent <span class="hlt">rift</span> is an example of lithospheric extension and flood basalt volcanism induced when a new mantle plume arrived near the base of the lithosphere. Very large volumes of basaltic magma were generated and partly erupted before substantial lithospheric extension began. Volcanism continued, along with extension and deep <span class="hlt">rift</span> subsidence, for the ensuing 15 m.y. Much of the basaltic magma, including some of the earliest flows, was formed by partial melting of isotopically primitive asthenosphere contained in the plume head. The intense but relatively short duration of <span class="hlt">rifting</span> and magmatism is a result of the dissipation of thermal and mechanical energy in the plume head. As the plume head spread beneath the lithosphere, it stretched the overlying lithosphere radially away from the Lake Superior region, the triple junction of the <span class="hlt">rift</span> <span class="hlt">system</span>, and partially melted to form the great volume of basalt and related intrusive rocks of the region. The plume arrived beneath a continent that was under compression as a result of the ongoing Grenville orogeny that affected a large region east of the <span class="hlt">rift</span>. That compression prevented full continental separation and eventually returned the region to compressional tectonics as the energy of the plume head waned. ?? 1992.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SedG..349...46W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SedG..349...46W"><span>Multiple provenance of <span class="hlt">rift</span> sediments in the composite basin-mountain <span class="hlt">system</span>: Constraints from detrital zircon U-Pb geochronology and heavy minerals of the early Eocene Jianghan Basin, central China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Lulu; Mei, Lianfu; Liu, Yunsheng; Luo, Jin; Min, Caizheng; Lu, Shengli; Li, Minghua; Guo, Libin</p> <p>2017-03-01</p> <p>Zircon U-Pb geochronology and heavy minerals are used in combination to provide valuable insights into the provenance of the early Eocene Jianghan Basin, central China. Five samples for zircon U-Pb dating and eighty-five samples for heavy mineral analysis were collected from drill cores or cuttings of the Xingouzui Formation. Most analyzed zircons are of magmatic origin, with oscillatory zoning. Detrital zircons from sample M96 located on eastern basin have two dominant age groups of 113-158 Ma and 400-500 Ma, and the other samples located on southern basin have three prominent age populations at 113-158 Ma, 400-500 Ma and 700-1000 Ma. Samples on different parts of the basin show distinct differences in heavy mineral compositions and they apparently divide into two groups according to the content of rutile (higher or lower than 4%). The spatial variations of zircon-tourmaline-rutile (ZTR) indices are marked by some noticeable increasing trends from basin margins to the inner part of the basin. Compared with the potential source areas, this study clarifies the multiple source characteristics of the Jianghan basin in the composite basin-mountain <span class="hlt">system</span>. The majority of clastic material was supplied from the north source area through <span class="hlt">rift</span>-trough sediment-transport pathways, and the eastern, southern and northwestern source areas also contributed detritus to the basin. This clastic material is broadly dispersed in the basin. The early Eocene paleogeography implies that <span class="hlt">rift</span> architecture and <span class="hlt">rifting</span> process had an important influence on sediment dispersal. This study shows that integrated zircon U-Pb geochronology and heavy mineral analysis is a useful and powerful method to identify sediment provenance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1817042C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1817042C"><span>Length variation of Gravity-Driven <span class="hlt">systems</span> in the Amazon River Mouth Basin: a history of carbonate-siliciclastic sedimentation and post-<span class="hlt">rift</span> subsidence</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cruz, Alberto; Gorini, Christian; Letouzey, Jean; Suc, Jean-Pierre; Reis, Tadeu; Silva, Cleverson; Le Bouteiller, Pauline; Granjeon, Didier; Haq, Bilal; Delprat-Jannaud, Florence</p> <p>2016-04-01</p> <p>This study address the post-<span class="hlt">rift</span> sedimentary record of the Amazon River Mouth Basin with a focus on gravity tectonics. We investigate shale detachment layers and the timing of different gravity deformation phases. Our study was based on more than 20,000 km of 2D multi-channel seismic data, 4,453 km2 of 3D multi-channel seismic data and 40 exploratory well data. A reliable age model was constructed based on biostratigraphic data. Five industry wells on the shelf/upper slope region and seven scientific wells drilled by DSDP and ODP in the distal Ceará Rise region were used for platform and deep environments correlations. This allowed us to calibrate the seismic lines and compare the sedimentation rates in different domains of the basin (e.g. shelf, slope, deep basin). In the Basin's shelf a widespread carbonate sequence dated as Late Paleocene grew up over a Latest Albian to Early Paleocene prograding clastic sequence. From the Eocene to the Late Miocene a mixed siliciclastic-carbonate aggrading megasequence developed. The first gravitational deformation event took place during the Eocene. The proximal limit (normal faults) of this this gravity-deformation <span class="hlt">system</span> occurs along the hinge line. The major and deeper detachment layer was identified within the previously deposed Late Cretaceous-Early Paleocene stratigraphic sequence (Cenomanian-Turonian deep shale source rock?). Further downslope, during the same period a stack of thrust sheets was created. In the central part of the Basin, a second gravitational deformation phase took place from Late Oligocene to early Late Miocene. During this period the basal detachment layer (Late Cretaceous?) was reactivated and the frontal thrust sheet created ridges and piggy-back basins. From the Late Miocene to present time, a major increase in the siliciclastic sedimentation rates was evidenced in the axis of the modern Amazon Delta. A huge aggrading-prograding mega-sequence forced the expansion of a third gravitational <span class="hlt">system</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70017946','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70017946"><span>Thermal budget of the lower east <span class="hlt">rift</span> zone, Kilauea Volcano</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Delaney, Paul T.; Duffield, Wendell A.; Sass, John H.; Kauahikaua, James P.; ,</p> <p>1993-01-01</p> <p>The lower east <span class="hlt">rift</span> zone of Kilauea has been the site of repeated fissure eruptions fed by dikes that traverse the depths of interest to geothermal explorations. We find that a hot-rock-and-magma <span class="hlt">system</span> of low permeability extending along the <span class="hlt">rift</span> zone at depths below about 4 km and replenished with magma at a rate that is small in comparison to the modern eruption rate Kilauea can supply heat to an overlying hydrothermal aquifer sufficient to maintain temperatures of about 250??C if the characteristic permeability to 4-km depth is about 10-15m2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6511K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6511K"><span>Along-axis transition between narrow and wide <span class="hlt">rifts</span>: Insights from 3D numerical experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koptev, Alexander; Calais, Eric; Burov, Evgueni; Leroy, Sylvie; Gerya, Taras</p> <p>2016-04-01</p> <p>Based on performed high-resolution rheologically consistent three-dimensional thermo-mechanical numerical models, we show that there is a significant difference in the influence of the rheological profile on <span class="hlt">rifting</span> style in the case of dominant active (plume-activated) <span class="hlt">rifting</span> compared to dominant passive (far-field tectonic stresses) <span class="hlt">rifting</span>. Narrow <span class="hlt">rifting</span>, conventionally attributed to cold strong lithosphere in passive <span class="hlt">rifting</span> mode, may develop in weak hot ultra-stretched lithosphere during active <span class="hlt">rifting</span>, after plume impingement on a tectonically pre-stressed lithosphere. In that case, initially ultra-wide small-amplitude <span class="hlt">rift</span> patterns focus, in a few Myr, in large-scale faults that form a narrow <span class="hlt">rift</span>. Also, wide <span class="hlt">rifting</span> may develop during ultra-slow spreading of strong lithosphere, and "switch" to the narrow <span class="hlt">rifting</span> upon plume impingement. For further understanding the mechanisms behind the interactions between the mantle plume and far-field stresses in case of realistic horizontally heterogeneous lithosphere, we have tested our models on the case of the central East African <span class="hlt">Rift</span> <span class="hlt">system</span> (EARS). The EARS south of the Ethiopian <span class="hlt">Rift</span> Valley bifurcates in two branches (eastern, magma-rich and western, magma-poor) surrounding the strong Tanzanian craton. Broad zones of low seismic velocity observed throughout the upper mantle beneath the central part of the EARS are consistent with the spreading of a deep mantle plume. The extensional features and topographic expression of the Eastern <span class="hlt">rift</span> varies significantly north-southward: in northern Kenya the area of deformation is very wide (some 150-250 km in E-W direction), to the south the <span class="hlt">rift</span> narrows to 60-70 km, yet further to the south this localized deformation widens again. Here we investigate this transition between localized and wide <span class="hlt">rifting</span> using thermo-mechanical numerical modeling that couples, in a dynamic sense, the rise of the upper mantle material with the deformation of the African lithosphere below the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1413065R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1413065R"><span><span class="hlt">Rifting</span> of the Tyrrhenian Basin, a complex interaction among faulting , magmatism and mantle exhumation.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ranero, C. R.; Sallarés, V.; Grevemeyer, I.; Zitellini, N.; Guzman, M.; Prada, M.; Moeller, S.; de Franco, R.; Medoc Cruise Party</p> <p>2012-04-01</p> <p>The Tyrrhenian basin has been created during the extension of continental lithosphere driven by the retreat of a Ionian slab across the mantle. The basin does not seem to be actively extending, but its preserved crustal structure provides information of the time evolution of the processes involved in <span class="hlt">rifting</span>. The basin <span class="hlt">rifted</span> from north to south, with <span class="hlt">rifting</span> stopping after progressively larger stretching factor towards the south. The northern region stopped opening after a relatively low extension factor. Towards the south extension increased up to full crustal separation that produced mantle exhumation. The <span class="hlt">final</span> structure displays two conjugate margins with asymmetric structures. Thus, the basin provides a natural laboratory to investigate a full <span class="hlt">rift</span> <span class="hlt">system</span>, that displays variable amounts of extension. We present observations from a two-ship seismic experiment that took place in spring 2010. The cruise took place on two legs. In the first leg, the Spanish R/V Sarmiento de Gamboa and the Italian R/V Urania collected five E-W trending wide-angle seismic (WAS) profiles across the entire basin using 17 Ocean Bottom Seismometers and 25 Ocean Bottom Hydrophones and a 4800 c.i. G-II gun array. The profiles were extended with land stations that recorded the marine shots. During a second leg the R/V Sarmiento de Gamboa collected 16 Multichannel Seismic Reflection (MCS) profiles using a 3.75 km-long streamer and a 3000 c.i. G-II gun array. MCS profiles were acquired coincident with the WAS profiles, and a number of additional lines concentrated in the central region of the basin where mantle exhumation took place. The seismic profiles were located to cover regions of the basin that displays different amount of extension, and the coincident wide-angle and MCS transects cross the entire basin to image the two conjugate margins. In this presentation we compare observations from different transects mapping the structures produced at different extension factors. A comparison</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/663481','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/663481"><span>Simulated coal gas MCFC power plant <span class="hlt">system</span> verification. <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p></p> <p>1998-07-30</p> <p>The objective of the main project is to identify the current developmental status of MCFC <span class="hlt">systems</span> and address those technical issues that need to be resolved to move the technology from its current status to the demonstration stage in the shortest possible time. The specific objectives are separated into five major tasks as follows: Stack research; Power plant development; Test facilities development; Manufacturing facilities development; and Commercialization. This <span class="hlt">Final</span> Report discusses the M-C power Corporation effort which is part of a general program for the development of commercial MCFC <span class="hlt">systems</span>. This <span class="hlt">final</span> report covers the entire subject of the Unocal 250-cell stack. Certain project activities have been funded by organizations other than DOE and are included in this report to provide a comprehensive overview of the work accomplished.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004EOSTr..85..273W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004EOSTr..85..273W"><span>Geoscience Methods Lead to Paleo-anthropological Discoveries in Afar <span class="hlt">Rift</span>, Ethiopia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>WoldeGabriel, Giday; Renne, Paul R.; Hart, William K.; Ambrose, Stanley; Asfaw, Berhane; White, Tim D.</p> <p>2004-07-01</p> <p>With few exceptions, most of the hominid evolutionary record in Africa is closely associated with the East African <span class="hlt">Rift</span> <span class="hlt">System</span>. The exceptions are the South African and Chadian hominids collected from the southern and west-central parts of the continent, respectively. The Middle Awash region stands alone as the most prolific paleoanthropological area ever discovered (Figure 1). Its paleontological record has yielded over 13,000 vertebrate fossils, including several hominid taxa, ranging in age from 5.8 Ma to the present. The uniqueness of the Middle Awash hominid sites lies in their occurrence within long, > 6 Ma volcanic and sedimentary stratigraphic records. The Middle Awash region has yielded the longest hominid record yet available. The region is characterized by distinct geologic features related to a volcanic and tectonic transition zone between the continental Main Ethiopian and the proto-oceanic Afar <span class="hlt">Rifts</span>. The <span class="hlt">rift</span> floor is wider-200 km-than other parts of the East African <span class="hlt">Rift</span> (Figure 1). Moreover, its Quaternary axial <span class="hlt">rift</span> zone is wide and asymetrically located close to the western margin. The fossil assemblages and the lithostratigraphic records suggest that volcanic and tectonic activities within the broad <span class="hlt">rift</span> floor and the adjacent <span class="hlt">rift</span> margins were intense and episodic during the late Neogene <span class="hlt">rift</span> evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004EOSTr..85..500A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004EOSTr..85..500A"><span>The life cycle of continental <span class="hlt">rifting</span> as a focus for U.S.-African scientific collaboration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abdelsalam, Mohamed G.; Atekwana, Estella A.; Keller, G. Randy; Klemperer, Simon L.</p> <p>2004-11-01</p> <p>The East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS) provides the unique opportunity found nowhere else on Earth, to investigate extensional processes from incipient <span class="hlt">rifting</span> in the Okavango Delta, Botswana, to continental breakup and creation of proto-oceanic basins 3000 km to the north in the Afar Depression in Ethiopia, Eritrea, and Djibouti.The study of continental <span class="hlt">rifts</span> is of great interest because they represent the initial stages of continental breakup and passive margin development, they are sites for large-scale sediment accumulation, and their geomorphology may have controlled human evolution in the past and localizes geologic hazards in the present. But there is little research that provides insights into the linkage between broad geodynamic processes and the life cycle of continental <span class="hlt">rifts</span>: We do not know why some <span class="hlt">rifts</span> evolve into mid-ocean ridges whereas others abort their evolution to become aulacogens. Numerous studies of the EARS and other continental <span class="hlt">rifts</span> have significantly increased our understanding of <span class="hlt">rifting</span> processes, but we particularly lack studies of the embryonic stages of <span class="hlt">rift</span> creation and the last stages of extension when continental breakup occurs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060010177','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060010177"><span>Joint Technical Architecture for Robotic <span class="hlt">Systems</span> (JTARS)-<span class="hlt">Final</span> Report</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bradley, Arthur T.; Holloway, Sidney E., III</p> <p>2006-01-01</p> <p>This document represents the <span class="hlt">final</span> report for the Joint Technical Architecture for Robotic <span class="hlt">Systems</span> (JTARS) project, funded by the Office of Exploration as part of the Intramural Call for Proposals of 2005. The project was prematurely terminated, without review, as part of an agency-wide realignment towards the development of a Crew Exploration Vehicle (CEV) and meeting the near-term goals of lunar exploration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA040119','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA040119"><span>Computer-Aided <span class="hlt">Final</span> Design Cost Estimating <span class="hlt">System</span> Overview.</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1977-05-01</p> <p>laboratory _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ /1— COMPUTER-AIDED <span class="hlt">FINAL</span> DESIGN • COST ESTIMATING <span class="hlt">SYSTEM</span> OVERVIEW © by...PROJECT . TASKAAEA~~ WORK UNIT NUMBERSCONSTRUCTION ENGINEERING RESEARCH LABORATORY ~~~~~~~~~ .• . — P.O. Box 4005 ~~ 4A7627~ %T4fldt11 Champa ign , IL 61820...Construction Division (FA), U.S. Army Construction Engineering Re- search Laboratory (CERL), Champaign , IL. The Principal Investigator was Mr. Michael</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.3304H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.3304H"><span>Phanerozoic <span class="hlt">Rifting</span> Phases And Mineral Deposits</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hassaan, Mahmoud</p> <p>2016-04-01</p> <p> connected with NW,WNW and N-S faults genetically related to volcano-hydrothermal activity associated the Red Sea <span class="hlt">rifting</span>. At Sherm EL-Sheikh hydrothermal manganese deposit occurs in Oligocene clastics within fault zone. Four iron-manganese-barite mineralization in Esh-Elmellaha plateau are controlled by faults trending NW,NE and nearly E-W intersecting Miocene carbonate rocks. Barite exists disseminated in the ores and as a vein in NW fault. In Shalatee - Halaib district 24 manganese deposits and barite veins with sulphide patches occur within Miocene carbonates distributed along two NW fault planes,trending 240°and 310° and occur in granite and basalt . Uranium -lead-zinc sulfide mineralization occur in Late Proterozoic granite, Late Cretaceous sandstones, and chiefly in Miocene clastic-carbonate-evaporate rocks. The occurrences of uranium- lead-zinc and iron-manganese-barite mineralization have the characteristic features of hypogene cavity filling and replacement deposits correlated with Miocene- Recent Aden volcanic rocks <span class="hlt">rifting</span>. In western Saudi Arabia barite-lead-zinc mineralization occurs at Lat. 25° 45' and 25° 50'N hosted by Tertiary sediments in limestone nearby basaltic flows and NE-SW fault <span class="hlt">system</span>. The mineralized hot brines in the Red Sea deeps considered by the author a part of this province. The author considers the constant <span class="hlt">rifting</span> phases of Pangea and then progressive fragmentation of Western Gondwana during the Late Carboniferous-Lias, Late Jurassic-Early Aptian, Late Aptian - Albian and Late Eocene-Early Miocene and Oligocene-Miocene, responsible for formation of the mineral deposits constituting the M provinces. During these events, <span class="hlt">rifting</span>, magmatism and hydrothermal activities took place in different peri-continental margins.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/900856','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/900856"><span>LCLS XTOD Tunnel Vacuum Transport <span class="hlt">System</span> (XVTS) <span class="hlt">Final</span> Design Report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shen, S</p> <p>2006-10-16</p> <p>The design of the X-Ray Vacuum Transport <span class="hlt">System</span> (XVTS) for the Linac Coherent Light Source (LCLS) X-ray Transport, Optics and Diagnostics (XTOD) <span class="hlt">system</span> has been analyzed and configured by the Lawrence Livermore National Laboratory's New Technologies Engineering Division (NTED) as requested by the SLAC/LCLS program. A preliminary design review was held on 11/14/05 [1][2]. This FDR (<span class="hlt">Final</span> Design Report) presents <span class="hlt">system</span> configuration, detailed analyses and selection of the mechanical and electrical components for the XTOD tunnel section, as well as the response to all issues raised in the review committee report. Also included are the plans for procurement, mechanical integration, schedule and the cost estimates. It should be noticed that, after the XVTS PDR, LCLS management has decided to lower the number of beamlines from three to one, and shorten the tunnel length from 212 m to 184 m. [3][4] The <span class="hlt">final</span> design of XVTS <span class="hlt">system</span> is completed. The major subjects presented in this report are: (1) Design of the complete <span class="hlt">system</span>. (2) <span class="hlt">System</span> analysis results. (3) ES&H issues and plan. (4) Project cost estimates and schedule.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920068131&hterms=flywheel+energy+storage&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dflywheel%2Benergy%2Bstorage','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920068131&hterms=flywheel+energy+storage&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dflywheel%2Benergy%2Bstorage"><span><span class="hlt">Final</span> prototype of magnetically suspended flywheel energy storage <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anand, D. K.; Kirk, J. A.; Zmood, R. B.; Pang, D.; Lashley, C.</p> <p>1991-01-01</p> <p>A prototype of a 500 Wh magnetically suspended flywheel energy storage <span class="hlt">system</span> was designed, built, and tested. The authors present the work done and include the following: (1) a <span class="hlt">final</span> design of the magnetic bearing, control <span class="hlt">system</span>, and motor/generator, (2) construction of a prototype <span class="hlt">system</span> consisting of the magnetic bearing stack, flywheel, motor, container, and display module, and (3) experimental results for the magnetic bearings, motor, and the entire <span class="hlt">system</span>. The successful completion of the prototype <span class="hlt">system</span> has achieved: (1) manufacture of tight tolerance bearings, (2) stability and spin above the first critical frequency, (3) use of inside sensors to eliminate runout problems, and (4) integration of the motor and magnetic bearings.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JAfES.121..136H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JAfES.121..136H"><span><span class="hlt">Rift</span>-related active fault-<span class="hlt">system</span> and a direction of maximum horizontal stress in the Cairo-Suez district, northeastern Egypt: A new approach from EMR-Technique and Cerescope data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hagag, Wael; Obermeyer, Hennes</p> <p>2016-09-01</p> <p>An active fault <span class="hlt">system</span> has been detected along the Cairo-Suez district in northeastern Egypt, applying the EMR-Technique using Cerescope. The E-W (old Mediterranean) and NW-SE (Red Sea-Gulf of Suez) fault-trends are estimated to have ongoing activity. Horizontal EMR-measurements indicate a NW to NNW orientation as a maximum horizontal stress direction (σ1), whereas an E-W orientation to has a secondary tendency. A simplified stress map for the Cairo-Suez district is constructed from the horizontal stress data measured at about 20 locations within the district. The mapped stresses will contribute to the stress data of the Cairo-Suez region on the world stress map (WSM). The present study results indicate rejuvenation of the inherited Mesozoic E-W oriented and Oligocene-Miocene <span class="hlt">rift</span>-related NW-SE oriented faults. The transfer of <span class="hlt">rift</span>-related deformation from Red Sea-Gulf of Suez region, which is currently undergoing an extensional stress regime in NE to NNE direction, would explain a seismotectonic activity of the Cairo-Suez district. These results are consistent with a present day NNW oriented compressional stresses attributed to a convergence between the African and Eurasian plates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/878785','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/878785"><span>A Dynamic Alignment <span class="hlt">System</span> for the <span class="hlt">Final</span> Focus Test Beam</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ruland, R.E.; Bressler, V.E.; Fischer, G.; Plouffe, D.; /SLAC</p> <p>2005-08-16</p> <p>The <span class="hlt">Final</span> Focus Test Beam (FFTB) was conceived as a technological stepping stone on the way to the next linear collider. Nowhere is this more evident than with the alignment subsystems. Alignment tolerances for components prior to beam turn are almost an order of magnitude smaller than for previous projects at SLAC. Position monitoring <span class="hlt">systems</span> which operate independent of the beam are employed to monitor motions of the components locally and globally with unprecedented precision. An overview of the FFTB alignment <span class="hlt">system</span> is presented herein.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5705507','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5705507"><span><span class="hlt">Final</span> report for TMX-U <span class="hlt">systems</span> support</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1985-01-01</p> <p>This <span class="hlt">final</span> report is for the TMX-U RF <span class="hlt">systems</span> development subcontract with Lawrence Livermore National Laboratory (LLNL). This program was initiated on July 1, 1983 and extended through September 30, 1985. This program was concerned with the development of RF <span class="hlt">systems</span> to meet the objectives of the TMX-U mirror program at LLNL. To accomplish this the following areas were studied during the course of this contract: (1) Ion Cyclotron Heating, (2) Electron Cyclotron Heating, (3) Drift Pumping, (4) Plasma Modeling, (5) Neutral Beam Heating, and (6) Neutral Gas transport and fueling. The key results of these activities are reported.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SolE....6..185D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SolE....6..185D"><span>Fault evolution in the Potiguar <span class="hlt">rift</span> termination, equatorial margin of Brazil</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Castro, D. L.; Bezerra, F. H. R.</p> <p>2015-02-01</p> <p>The transform shearing between South American and African plates in the Cretaceous generated a series of sedimentary basins on both plate margins. In this study, we use gravity, aeromagnetic, and resistivity surveys to identify architecture of fault <span class="hlt">systems</span> and to analyze the evolution of the eastern equatorial margin of Brazil. Our study area is the southern onshore termination of the Potiguar <span class="hlt">rift</span>, which is an aborted NE-trending <span class="hlt">rift</span> arm developed during the breakup of Pangea. The basin is located along the NNE margin of South America that faces the main transform zone that separates the North and the South Atlantic. The Potiguar <span class="hlt">rift</span> is a Neocomian structure located at the intersection of the equatorial and western South Atlantic and is composed of a series of NE-trending horsts and grabens. This study reveals new grabens in the Potiguar <span class="hlt">rift</span> and indicates that stretching in the southern <span class="hlt">rift</span> termination created a WNW-trending, 10 km wide, and ~ 40 km long right-lateral strike-slip fault zone. This zone encompasses at least eight depocenters, which are bounded by a left-stepping, en echelon <span class="hlt">system</span> of NW-SE- to NS-striking normal faults. These depocenters form grabens up to 1200 m deep with a rhomb-shaped geometry, which are filled with <span class="hlt">rift</span> sedimentary units and capped by postrift sedimentary sequences. The evolution of the <span class="hlt">rift</span> termination is consistent with the right-lateral shearing of the equatorial margin in the Cretaceous and occurs not only at the <span class="hlt">rift</span> termination but also as isolated structures away from the main <span class="hlt">rift</span>. This study indicates that the strike-slip shearing between two plates propagated to the interior of one of these plates, where faults with similar orientation, kinematics, geometry, and timing of the major transform are observed. These faults also influence <span class="hlt">rift</span> geometry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatGe...9..145L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatGe...9..145L"><span>Massive and prolonged deep carbon emissions associated with continental <span class="hlt">rifting</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Hyunwoo; Muirhead, James D.; Fischer, Tobias P.; Ebinger, Cynthia J.; Kattenhorn, Simon A.; Sharp, Zachary D.; Kianji, Gladys</p> <p>2016-02-01</p> <p>Carbon from Earth’s interior is thought to be released to the atmosphere mostly via degassing of CO2 from active volcanoes. CO2 can also escape along faults away from active volcanic centres, but such tectonic degassing is poorly constrained. Here we use measurements of diffuse soil CO2, combined with carbon isotopic analyses to quantify the flux of CO2 through fault <span class="hlt">systems</span> away from active volcanoes in the East African <span class="hlt">Rift</span> <span class="hlt">system</span>. We find that about 4 Mt yr-1 of mantle-derived CO2 is released in the Magadi-Natron Basin, at the border between Kenya and Tanzania. Seismicity at depths of 15-30 km implies that extensional faults in this region may penetrate the lower crust. We therefore suggest that CO2 is transferred from upper-mantle or lower-crustal magma bodies along these deep faults. Extrapolation of our measurements to the entire Eastern <span class="hlt">rift</span> of the <span class="hlt">rift</span> <span class="hlt">system</span> implies a CO2 flux on the order of tens of megatonnes per year, comparable to emissions from the entire mid-ocean ridge <span class="hlt">system</span> of 53-97 Mt yr-1. We conclude that widespread continental <span class="hlt">rifting</span> and super-continent breakup could produce massive, long-term CO2 emissions and contribute to prolonged greenhouse conditions like those of the Cretaceous.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T53C..08B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T53C..08B"><span>­­Are current models for normal fault array evolution applicable to natural <span class="hlt">rifts</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bell, R. E.; Jackson, C. A. L.</p> <p>2015-12-01</p> <p>Conceptual models predicting the geometry and evolution of normal fault arrays are vital to assess <span class="hlt">rift</span> physiography, syn-<span class="hlt">rift</span> sediment dispersal and seismic hazard. Observations from data-rich <span class="hlt">rifts</span> and numerical and physical models underpin widely used fault array models predicting: i) during <span class="hlt">rift</span> initiation, arrays are defined by multiple, small, isolated faults; ii) as <span class="hlt">rifting</span> progresses, strain localises onto fewer larger structures; and iii) with continued strain, faulting migrates toward the <span class="hlt">rift</span> axis, resulting in <span class="hlt">rift</span> narrowing. Some <span class="hlt">rifts</span> display these characteristics whereas others do not. Here we present several case studies documenting fault migration patterns that do not fit this ideal. In this presentation we will begin by reviewing existing fault array models before presenting a series of case studies (including from the northern North Sea and the Gulf of Corinth), which document fault migration patterns that are not predicted by current fault evolution models. We show that strain migration onto a few, large faults is common in many <span class="hlt">rifts</span> but that, rather than localising onto these structures until the cessation of <span class="hlt">rifting</span>, strain may 'sweep' across the basin. Furthermore, crustal weaknesses developed in early tectonic events can cause faults during subsequent phases of extension to grow relatively quickly and accommodate the majority if not all of the <span class="hlt">rift</span>-related strain; in these cases, strain migration does not and need not occur. <span class="hlt">Finally</span>, in salt-influenced <span class="hlt">rifts</span>, strain localisation may not occur at all; rather, strain may become progressively more diffuse due to tilting of the basement and intrastratal salt décollements, thus leading to superimposition of thin-skinned, gravity-driven and thick-skinned, plate-driven, basement-involved extension. We call for the community to unite to develop the next-generation of normal fault array models that include complexities such as the thermal and rheological properties of the lithosphere, specific</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SoSyR..50..184G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SoSyR..50..184G"><span>Classification of the <span class="hlt">rift</span> zones of venus: <span class="hlt">Rift</span> valleys and graben belts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guseva, E. N.</p> <p>2016-05-01</p> <p>The spatial distribution of <span class="hlt">rift</span> zones of Venus, their topographic configuration, morphometric parameters, and the type of volcanism associating with <span class="hlt">rifts</span> were analyzed. This allowed the main characteristic features of <span class="hlt">rifts</span> to be revealed and two different types of <span class="hlt">rift</span>-forming structures, serving for classification of <span class="hlt">rift</span> zones as <span class="hlt">rift</span> valleys and graben belts, to be isolated. These structural types (facies) of <span class="hlt">rift</span> zones are differently expressed in the relief: <span class="hlt">rift</span> valleys are individual deep (several kilometers) W-shaped canyons, while graben belts are clusters of multiple V-shaped and rather shallow (hundreds of meters) depressions. Graben belts are longer and wider, as compared to <span class="hlt">rift</span> valleys. <span class="hlt">Rift</span> valleys are spatially associated with dome-shaped volcanic rises and large volcanos (concentrated volcanic sources), while graben belts do not exhibit such associations. Volcanic activity in the graben belts are presented by spacious lava fields with no apparent sources of volcanism. Graben belts and <span class="hlt">rift</span> valleys were formed during the Atlian Period of geologic history of Venus, and they characterized the tectonic style of the planet at the late stages of its geologic evolution. Formation of this or that structural facies of the <span class="hlt">rift</span> zones of Venus were probably governed by the thickness of the lithosphere, its rheological properties, and the development degree of the mantle diapirs associating with <span class="hlt">rift</span> zones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T21B2543M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T21B2543M"><span>The evolving contribution of border faults and intra-<span class="hlt">rift</span> faults in early-stage East African <span class="hlt">rifts</span>: insights from the Natron (Tanzania) and Magadi (Kenya) basins</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Muirhead, J.; Kattenhorn, S. A.; Dindi, E.; Gama, R.</p> <p>2013-12-01</p> <p>In the early stages of continental <span class="hlt">rifting</span>, East African <span class="hlt">Rift</span> (EAR) basins are conventionally depicted as asymmetric basins bounded on one side by a ~100 km-long border fault. As <span class="hlt">rifting</span> progresses, strain concentrates into the <span class="hlt">rift</span> center, producing intra-<span class="hlt">rift</span> faults. The timing and nature of the transition from border fault to intra-<span class="hlt">rift</span>-dominated strain accommodation is unclear. Our study focuses on this transitional phase of continental <span class="hlt">rifting</span> by exploring the spatial and temporal evolution of faulting in the Natron (border fault initiation at ~3 Ma) and Magadi (~7 Ma) basins of northern Tanzania and southern Kenya, respectively. We compare the morphologies and activity histories of faults in each basin using field observations and remote sensing in order to address the relative contributions of border faults and intra-<span class="hlt">rift</span> faults to crustal strain accommodation as <span class="hlt">rifting</span> progresses. The ~500 m-high border fault along the western margin of the Natron basin is steep compared to many border faults in the eastern branch of the EAR, indicating limited scarp degradation by mass wasting. Locally, the escarpment shows open fissures and young scarps 10s of meters high and a few kilometers long, implying ongoing border fault activity in this young <span class="hlt">rift</span>. However, intra-<span class="hlt">rift</span> faults within ~1 Ma lavas are greatly eroded and fresh scarps are typically absent, implying long recurrence intervals between slip events. <span class="hlt">Rift</span>-normal topographic profiles across the Natron basin show the lowest elevations in the lake-filled basin adjacent to the border fault, where a number of hydrothermal springs along the border fault <span class="hlt">system</span> expel water into the lake. In contrast to Natron, a ~1600 m high, densely vegetated, border fault escarpment along the western edge of the Magadi basin is highly degraded; we were unable to identify evidence of recent rupturing. <span class="hlt">Rift</span>-normal elevation profiles indicate the focus of strain has migrated away from the border fault into the <span class="hlt">rift</span> center, where</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRB..121.8068R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRB..121.8068R"><span>Passive <span class="hlt">rifting</span> of thick lithosphere in the southern East African <span class="hlt">Rift</span>: Evidence from mantle transition zone discontinuity topography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reed, Cory A.; Liu, Kelly H.; Chindandali, Patrick R. N.; Massingue, Belarmino; Mdala, Hassan; Mutamina, Daniel; Yu, Youqiang; Gao, Stephen S.</p> <p>2016-11-01</p> <p>To investigate the mechanisms for the initiation and early-stage evolution of the nonvolcanic southernmost segments of the East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS), we installed and operated 35 broadband seismic stations across the Malawi and Luangwa <span class="hlt">rift</span> zones over a 2 year period from mid-2012 to mid-2014. Stacking of over 1900 high-quality receiver functions provides the first regional-scale image of the 410 and 660 km seismic discontinuities bounding the mantle transition zone (MTZ) within the vicinity of the <span class="hlt">rift</span> zones. When a 1-D standard Earth model is used for time-depth conversion, a normal MTZ thickness of 250 km is found beneath most of the study area. In addition, the apparent depths of both discontinuities are shallower than normal with a maximum apparent uplift of 20 km, suggesting widespread upper mantle high-velocity anomalies. These findings suggest that it is unlikely for a low-velocity province to reside within the upper mantle or MTZ beneath the nonvolcanic southern EARS. They also support the existence of relatively thick and strong lithosphere corresponding to the widest section of the Malawi <span class="hlt">rift</span> zone, an observation that is consistent with strain localization models and fault polarity and geometry observations. We postulate that the Malawi <span class="hlt">rift</span> is driven primarily by passive extension within the lithosphere attributed to the divergent rotation of the Rovuma microplate relative to the Nubian plate, and that contributions of thermal upwelling from the lower mantle are insignificant in the initiation and early-stage development of <span class="hlt">rift</span> zones in southern Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10125834','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10125834"><span>Variable-Speed Wind <span class="hlt">System</span> Design : <span class="hlt">Final</span> Report.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lauw, Hinan K.; Weigand, Claus H.; Marckx, Dallas A.; Electronic Power Conditioning, Inc.</p> <p>1993-10-01</p> <p>Almost from the onset of the development of wind energy conversion <span class="hlt">systems</span> (WECS), it was known that variable-speed operation of the turbine would maximize energy capture. This study was commissioned to assess the cost, efficiency gain, reduction of the cost of energy (COE), and other operating implications of converting the existing hardware of a modern fixed-speed wind energy conversion <span class="hlt">system</span> to variable-speed operation. The purpose of this study was to develop a preliminary design for the hardware required to allow variable-speed operation using a doubly-fed generator with an existing fixed-speed wind turbine design. The turbine selected for this study is the AWT-26 designed and built by Advanced Wind Turbines Inc. of Redmond, Washington. The lowest projected COE using this variable-speed generation <span class="hlt">system</span> is projected to be $0.0499/kWh, compared to the lowest possible COE with fixed-speed generation which is projected to be $0.0546/kWh. This translates into a 8.6% reduction of the COE using this variable-speed generation option. The preliminary <span class="hlt">system</span> design has advanced to where the printed circuit boards can be physically laid out based on the schematics and the <span class="hlt">system</span> software can be written based on the control flow-charts. The core of hardware and software has been proven to be successful in earlier versions of VSG <span class="hlt">systems</span>. The body of this report presents the results of the VSWG <span class="hlt">system</span> development. Operation under normal and fault conditions is described in detail, the <span class="hlt">system</span> performance for variable-speed operation is estimated and compared to the original fixed-speed <span class="hlt">system</span> performance, and specifications for all <span class="hlt">system</span> components (generator, power electronic converter, and <span class="hlt">system</span> controller) are given. Costs for all components are estimated, and incremental <span class="hlt">system</span> cost is compared to incremental energy production. <span class="hlt">Finally</span>, operational features of the VSWG which are not available in the existing FSWG <span class="hlt">system</span> are outlined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010Tectp.488....7A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010Tectp.488....7A"><span>On the geodynamics of the Aegean <span class="hlt">rift</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Agostini, Samuele; Doglioni, Carlo; Innocenti, Fabrizio; Manetti, Piero; Tonarini, Sonia</p> <p>2010-06-01</p> <p>The Aegean <span class="hlt">rift</span> is considered to be either a classic backarc basin, or the result of the westward escape of Anatolia, or the effect of a gravitational collapse of an over-thickened lithosphere. Here these models are questioned. We alternatively present a number of geodynamic and magmatic constraints suggesting a simple model for the genesis of the extension as being related to the differential advancement of the upper lithosphere over a heterogeneous lower African plate. The Greek microplate overrides the Ionian oceanic segment of the African plate faster than the Anatolian microplate over the thicker Levantine more continental segment. This setting is evidenced by GPS-velocity gradient in the hangingwall of the Hellenic-Cyprus subduction <span class="hlt">system</span> and requires a zone of <span class="hlt">rifting</span> splitting the hangingwall into two microplates. This mechanism is unrelated to the replacement of retreated slab by the asthenosphere as typically occurs in the backarc of west-directed subduction zones. The supposed greater dehydration of the Ionian segment of the slab is providing a larger amount of fluids into the low velocity channel at the top of the asthenosphere, allowing a faster decoupling between the Greek microplate and the underlying mantle with respect to the Anatolian microplate. Slab ruptures associated with the differential retreat controlled by the inherited lithospheric heterogeneities in the lower plate and the proposed upwelling of the mantle suggested by global circulation models would explain the occurrence and coexistence of slab-related and slab-unrelated magmatism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T13A2975B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T13A2975B"><span><span class="hlt">Rift</span> strength controls rapid plate accelerations: A global analysis of Pangea fragmentation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brune, S.; Williams, S.; Butterworth, N. P.; Müller, D.</p> <p>2015-12-01</p> <p>Motions of Earth's plates are thought to be driven by slab pull, basal drag, and ridge push. Here we propose that plate motions during supercontinental fragmentation are decisively controlled by the non-linear decay of a resistive force: <span class="hlt">rift</span> strength. We use state-of-the-art global tectonic reconstructions and the new geotectonic analysis tool pyGPlates to analyze the transition from <span class="hlt">rifting</span> to sea-floor spreading of well-studied post-Pangea <span class="hlt">rift</span> <span class="hlt">systems</span> (Central Atlantic, South Atlantic, Iberia/Newfoundland, Australia/Antarctica, North Atlantic, South China Sea, Gulf of California). In all cases, continental extension starts with a slow phase (< 10 mm/yr, full extension velocity) followed by a rapid acceleration over periods of a few My that introduces a fast <span class="hlt">rift</span> phase (> 10 mm/yr). The transition from slow to fast extension takes place long before crustal break-up. In fact, we find that approximately half of the present day <span class="hlt">rifted</span> margin area was created during the slow, and the other half during the fast phase. We reproduce the transition from slow to fast <span class="hlt">rifting</span> using numerical forward models with force boundary conditions, such that <span class="hlt">rift</span> velocities are not imposed but instead evolve naturally in response to changing strength of the <span class="hlt">rift</span>. These models show that the two-phase velocity behavior during <span class="hlt">rifting</span> and the rapid speed-up are intrinsic features of continental rupture that can be robustly inferred for different crust and mantle rheologies.It has been proposed that abrupt plate accelerations can be caused by plume-lithosphere interaction, subduction initiation, and slab detachment. However, none of these mechanisms explains our result that plate speed-up systematically precedes continental break-up. We therefore propose dynamic <span class="hlt">rift</span> weakening as a new mechanism for rapid plate motion changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Tectp.607...98K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Tectp.607...98K"><span>The development of extension and magmatism in the Red Sea <span class="hlt">rift</span> of Afar</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Keir, Derek; Bastow, Ian D.; Pagli, Carolina; Chambers, Emma L.</p> <p>2013-11-01</p> <p>Despite the importance of continental breakup in plate tectonics, precisely how extensional processes such as brittle faulting, ductile plate stretching, and magma intrusion evolve in space and time during the development of new ocean basins remains poorly understood. The <span class="hlt">rifting</span> of Arabia from Africa in the Afar depression is an ideal natural laboratory to address this problem since the region exposes subaerially the tectonically active transition from continental <span class="hlt">rifting</span> to incipient seafloor spreading. We review recent constraints on along-axis variations in <span class="hlt">rift</span> morphology, crustal and mantle structure, the distribution and style of ongoing faulting, subsurface magmatism and surface volcanism in the Red Sea <span class="hlt">rift</span> of Afar to understand processes ultimately responsible for the formation of magmatic <span class="hlt">rifted</span> continental margins. Our synthesis shows that there is a fundamental change in <span class="hlt">rift</span> morphology from central Afar northward into the Danakil depression, spatially coincident with marked thinning of the crust, an increase in the volume of young basalt flows, and subsidence of the land towards and below sea-level. The variations can be attributed to a northward increase in proportion of extension by ductile plate stretching at the expense of magma intrusion. This is likely in response to a longer history of localised heating and weakening in a narrower <span class="hlt">rift</span>. Thus, although magma intrusion accommodates strain for a protracted period during <span class="hlt">rift</span> development, the <span class="hlt">final</span> stages of breakup are dominated by a phase of plate stretching with a shift from intrusive to extrusive magmatism. This late-stage pulse of decompression melting due to plate thinning may be responsible for the formation of seaward dipping reflector sequences of basalts and sediments, which are ubiquitous at magmatic <span class="hlt">rifted</span> margins worldwide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008GGG.....9.7024B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008GGG.....9.7024B"><span>Transform and <span class="hlt">rift</span> structure of Paleogene crust near Resolution Ridge, Tasman Sea, southwest New Zealand</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barker, Daniel H. N.; Wood, Ray; Sutherland, Rupert</p> <p>2008-07-01</p> <p>Multibeam bathymetry, seismic reflection, magnetic anomaly, and gravity anomaly data show that most of the Resolution Ridge <span class="hlt">System</span> is Tasman Sea oceanic crust, deformed by Eocene <span class="hlt">rift</span> faulting associated with the initiation of the modern Australia-Pacific plate boundary. Resolution Ridge, the most eastern ridge of the <span class="hlt">system</span>, is inferred to be continental crust that was plucked from the southwest corner of the Campbell Plateau during Eocene <span class="hlt">rift</span> propagation. <span class="hlt">Rift</span> propagation proceeded through sequential northward steps between weak points in the lithosphere: young fossil spreading centers, fracture zones, and the western margin of the continental Campbell Plateau. Fracture zones guided the large-scale geometry of the <span class="hlt">rift</span>, but there is not always a close surface correspondence between transform and <span class="hlt">rift</span> faults. This may be because transform faults were subvertical, whereas <span class="hlt">rift</span> faults evolved to be moderately dipping. The very good correspondence of fracture zones, <span class="hlt">rift</span> faults, and magnetic anomalies from the Resolution Ridge <span class="hlt">System</span> with their conjugates southwest of the Campbell Plateau allows precise prerift reconstruction of the Australia-Pacific plate boundary at a time (circa 48 Ma) of significant global plate reorganization and profound change in Pacific plate motion. This precise plate reconstruction better constrains plate motion chains that connect the Pacific and Indo-Atlantic hemispheres, thus contributing to debate of global scientific issues such as what caused the bend in the Emperor-Hawaii seamount chain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25636855','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25636855"><span>The accuracy of the Oculus <span class="hlt">Rift</span> virtual reality head-mounted display during cervical spine mobility measurement.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xu, Xu; Chen, Karen B; Lin, Jia-Hua; Radwin, Robert G</p> <p>2015-02-26</p> <p>An inertial sensor-embedded virtual reality (VR) head-mounted display, the Oculus <span class="hlt">Rift</span> (the <span class="hlt">Rift</span>), monitors head movement so the content displayed can be updated accordingly. While the <span class="hlt">Rift</span> may have potential use in cervical spine biomechanics studies, its accuracy in terms of cervical spine mobility measurement has not yet been validated. In the current study, a VR environment was designed to guide participants to perform prescribed neck movements. The cervical spine kinematics was measured by both the <span class="hlt">Rift</span> and a reference motion tracking <span class="hlt">system</span>. Comparison of the kinematics data between the <span class="hlt">Rift</span> and the tracking <span class="hlt">system</span> indicated that the <span class="hlt">Rift</span> can provide good estimates on full range of motion (from one side to the other side) during the performed task. Because of inertial sensor drifting, the unilateral range of motion (from one side to neutral posture) derived from the <span class="hlt">Rift</span> is more erroneous. The root-mean-square errors over a 1-min task were within 10° for each rotation axis. The error analysis further indicated that the inertial sensor drifted approximately 6° at the beginning of a trial during the initialization. This needs to be addressed when using the <span class="hlt">Rift</span> in order to more accurately measure cervical spine kinematics. It is suggested that the front cover of the <span class="hlt">Rift</span> should be aligned against a vertical plane during its initialization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.7374D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.7374D"><span>The 2003-2004 seismic swarm in the western Corinth <span class="hlt">rift</span>: Evidence for a multiscale pore pressure diffusion process along a permeable fault <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Duverger, Clara; Godano, Maxime; Bernard, Pascal; Lyon-Caen, Hélène; Lambotte, Sophie</p> <p>2015-09-01</p> <p>Microseismic multiplets occurring in the western Corinth <span class="hlt">rift</span>, Greece, during a large swarm are analyzed to retrieve their spatiotemporal characteristics. These multiplets activated small subfaults at depth (˜7 km), up to 1 km long, at the root of two parallel active normal faults. The swarm migrates westward nearly horizontally over 10 km at an average velocity of 50 m/d with a diffusivity of 0.5 m2 s-1. It successively activates the Aigion fault, a relay zone in its hanging wall, and the Fassouleika fault. Within each multiplet, hypocenters also migrate with diffusivities ranging from 0.001 to 0.4 m2 s-1. The largest internal diffusivities appear at the core of the layer defined by the clusters. These results are interpreted as a hydroshear process caused by pore pressure migration within permeable corridors resulting from the intersection of the major faults with a brittle geological layer inherited from the Hellenic nappe stack.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27437571','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27437571"><span>Abrupt plate accelerations shape <span class="hlt">rifted</span> continental margins.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brune, Sascha; Williams, Simon E; Butterworth, Nathaniel P; Müller, R Dietmar</p> <p>2016-08-11</p> <p><span class="hlt">Rifted</span> margins are formed by persistent stretching of continental lithosphere until breakup is achieved. It is well known that strain-rate-dependent processes control <span class="hlt">rift</span> evolution, yet quantified extension histories of Earth's major passive margins have become available only recently. Here we investigate <span class="hlt">rift</span> kinematics globally by applying a new geotectonic analysis technique to revised global plate reconstructions. We find that <span class="hlt">rifted</span> margins feature an initial, slow <span class="hlt">rift</span> phase (less than ten millimetres per year, full rate) and that an abrupt increase of plate divergence introduces a fast <span class="hlt">rift</span> phase. Plate acceleration takes place before continental rupture and considerable margin area is created during each phase. We reproduce the rapid transition from slow to fast extension using analytical and numerical modelling with constant force boundary conditions. The extension models suggest that the two-phase velocity behaviour is caused by a <span class="hlt">rift</span>-intrinsic strength--velocity feedback, which can be robustly inferred for diverse lithosphere configurations and rheologies. Our results explain differences between proximal and distal margin areas and demonstrate that abrupt plate acceleration during continental <span class="hlt">rifting</span> is controlled by the nonlinear decay of the resistive <span class="hlt">rift</span> strength force. This mechanism provides an explanation for several previously unexplained rapid absolute plate motion changes, offering new insights into the balance of plate driving forces through time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP31G..01C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP31G..01C"><span>A Review of New and Anticipated High-Resolution Paleoclimate Records from the East African <span class="hlt">Rift</span> <span class="hlt">System</span> and Their Implications for Hominin Evolution and Demography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cohen, A. S.</p> <p>2014-12-01</p> <p>Our understanding of Late Tertiary/Quaternary climate and environmental history in East Africa has, to date, largely been based on outcrop and marine drill core records. Although these records have proven extremely valuable both in reconstructing environmental change and placing human evolution in an environmental context, their quality is limited by resolution, continuity, uncertainties about superposition and outcrop weathering. To address this problem, long drill core records from extant ancient lakes and lake beds are being collected by several research groups. Long cores (up to 100s of m.) from basin depocenters in both the western and eastern <span class="hlt">rifts</span> are now available spanning nearly the entire latitudinal range of the East Africa <span class="hlt">Rift</span>. This network of core records, especially when coupled with outcrop data, is providing an opportunity to compare the nature of important global climate transitions (especially glacial/interglacial events and precessional cycles) across the continent, thereby documenting regional heterogeneity in African climate history. Understanding this heterogeneity is critical for realistically evaluating competing hypotheses of environmental forcing of human evolution, and especially ideas about the dispersal of anatomically modern humans out of Africa in the early Late Pleistocene. In particular, understanding the hydrological and paleoecological history of biogeographic corridors linking eastern Africa, the Nile River Valley and the Levant is likely to be vastly improved through comparative analysis of these new drill cores over the next few years. Because we do not a priori know the primary forcing factors affecting this environmental history, it will essential to develop the best possible age models, employing multiple and novel geochronometric tools to make these comparisons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T43E2717F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T43E2717F"><span>Low-temperature thermochronologic constraints on cooling and exhumation trends along conjugate margins, within core complexes and eclogite-bearing gneiss domes of the Woodlark <span class="hlt">rift</span> <span class="hlt">system</span> of eastern Papua New Guinea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fitzgerald, P. G.; Baldwin, S.; Bermudez, M. A.; Miller, S. R.; Webb, L. E.; Little, T.</p> <p>2012-12-01</p> <p>In eastern Papua New Guinea, active sea-floor spreading within the Woodlark Basin has been propagating westward since at least 6 Ma into heterogeneous crust of the Woodlark <span class="hlt">Rift</span>. The seafloor spreading <span class="hlt">system</span> divides the northern conjugate margin (Woodlark Rise) from the southern margin (Pocklington Rise). West of the seafloor spreading <span class="hlt">rift</span>-tip are high-standing extensional gneiss domes and core complexes of the D'Entrecasteaux Islands (DEI). Domes comprise amphibolite and eclogite-facies gneisses, and Pleistocene granitoid intrusions. Flanked by mylonitic shear zone carapaces and normal faults, the domes are juxtaposed against an upper plate that includes ultramafic rocks and gabbro, correlated with the Papuan ultramafic belt. Petrologic and structural evidence from the DEI has been interpreted as evidence for diapiric ascent of the largely felsic domes, with thermo-mechanical modeling proposing (U)HP exhumation in terms of diapiric flow aided by propagating extension, with feedback between the two. Core complexes lacking evidence for diapiric-aided exhumation include the Prevost Range (eastern Normanby Island), Dayman Dome (Papuan Peninsula), and Misima Island (southern conjugate margin). Thermochronology is being applied to understand the thermal and exhumation history, and hence help constrain mechanisms of (U)HP exhumation. AFT and AHe ages from samples near sea-level along conjugate margins and DEI range from ca. 12 Ma to <1 Ma, generally decreasing from east to west, although with some localized variation. Confined track length distributions (CTLD), obtained using 252Cf implantation, generally indicate rapid cooling (means ≥~14 μm), except on Goodenough Island, the western-most and highest-standing dome. On Goodenough Island, samples from the core zone have AFT ages from ~3 - <1 Ma with age decreasing with decreasing elevation. Core zone samples have mean track lengths (7-13 μm) and are positively skewed, whereas samples from shear zones are younger (<1</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.B51D0407C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.B51D0407C"><span>Comparing Carbonate-Depositing Hydrothermal <span class="hlt">Systems</span> Along the Mid-Atlantic Ridge at Lost City Hydrothermal Field and Along the Rio Grande <span class="hlt">rift</span> in the Southwestern US: Geochemistry, Geomicrobiology and Mineralogy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cron, B. R.; Crossey, L.; Hall, J.; Takacs-Vesbach, C.; Dahm, K.; Northup, D.; Karlstrom, K.</p> <p>2008-12-01</p> <p>Both continental and marine <span class="hlt">rift</span> settings are characterized by hydrothermal vents (smokers) that include important components of mantle-derived "endogenic" fluids. These fluids ascend along extensional faults and provide unique biologic settings. We hypothesize that deep crustal processes support near-surface metabolic strategies by delivering chemically reduced constituents to partially oxidized surface environments. Lost City hydrothermal field, a marine vent <span class="hlt">system</span> located 15 km west of the Mid-Atlantic ridge, exhibits a range of temperatures (40 to 75°C), pH (9-9.8), and mineral compositions (carbonate rather than sulfide-dominated) that were originally thought to be non-existent in marine vent <span class="hlt">systems</span>. Travertine depositing CO2 springs within the Rio Grande <span class="hlt">rift</span>, NM exhibit striking similarities in many respects to vents in Lost City. Previous research has already determined the importance of methanogenic and sulfur metabolizing microorganisms in carbonate structures at Lost City. Phylogenetic analysis of 16S rRNA genes from a terrestrial CO2 spring was performed. In addition, cells from bacteria and fungi were also cultured with oligotrophic media. Both archaeal phylotypes from the terrestrial spring grouped within Marine Group I of the Crenarchaeota, a clade dominated by sequences from hydrothermal marine vents, including some from Lost City. We will report comparative analyses of sequences from Lost City and both cultured and environmental clone libraries from the terrestrial spring using UniFrac. Geochemical modeling of data (water and gas chemistry from both locations) is used to rank the energy available for dozens of metabolic reactions. SEM and microprobe data are presented to compare mineral compositions. Our results will be discussed in respect to the tectonic setting, microbial community distributions, and the geochemical composition and textural properties of the carbonates that are precipitated in each of these <span class="hlt">systems</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.5444H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.5444H"><span><span class="hlt">Rift</span> flank uplift and thermal evolution of an intracratonic <span class="hlt">rift</span> basin (eastern Canada) determined by combined apatite and zircon (U-Th)/He thermochronology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hardie, Rebecca; Schneider, David; Metcalf, James; Flowers, Rebecca</p> <p>2015-04-01</p> <p>As a significant portion of the world's oil reserves are retrieved from <span class="hlt">rift</span> <span class="hlt">systems</span>, a better understanding of the timing of thermal evolution and burial history of these <span class="hlt">systems</span> will increase the potential for the discovery of hydrocarbon-bearing <span class="hlt">rifts</span>. The Ottawa Embayment of the St. Lawrence Platform of eastern Canada is a reactivated intracratonic <span class="hlt">rift</span> basin related to the opening of the Iapetus Ocean at ca. 620-570 Ma, followed by the formation of the well-developed continental passive margin. Siliciclastic sediments derived from the adjacent uplifted Neoproterozoic Grenville basement provide the basin fill material. Apatite and zircon (U-Th)/He thermochronology allows for low-temperature analysis across the exposed crystalline <span class="hlt">rift</span> flank into the synrift sedimentary sequence to resolve the unroofing, burial and subsidence history of the region. Samples were collected along a ~250 km NE-SW transect, oblique to the axis of the <span class="hlt">rift</span>, from Mont-Tremblant, Québec (~900 m) to the central axis of the Paleozoic <span class="hlt">rift</span> in the Southern Ontario Lowlands (~300 m). Targets included Neoproterozoic metamorphic rocks of the Grenville Province along the <span class="hlt">rift</span> flank and basinal Cambro-Ordovician Potsdam Group. Samples from the <span class="hlt">rift</span> flank yield zircon ages from ca. 650 Ma to ca. 560 Ma and apatite ages from ca. 290 Ma to ca. 190 Ma, with a weak positive correlation between age and grain size. Zircon ages demonstrate a strong negative correlation with radiation damage: as eU increases, age decreases. By incorporating (U-Th)/He ages with regional constraints in the thermal modelling program HeFTy, viable temperature time paths for the region can be determined. Through inverse and forward modeling, preliminary <span class="hlt">rift</span> flank (U-Th)/He ages correspond to post-Grenville cooling with <4 km of post-Carboniferous burial. The data define slow and long episodes of syn- to post-<span class="hlt">rift</span> cooling with rates between 0.4 and 0.1 °C/Ma. (U-Th)/He dating of samples along the full-length of the transect</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28029758','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28029758"><span>Adoption and Foster Care Analysis and Reporting <span class="hlt">System</span>. <span class="hlt">Final</span> rule.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p></p> <p>2016-12-14</p> <p>The Social Security Act (the Act) requires that ACF regulate a national data collection <span class="hlt">system</span> that provides comprehensive demographic and case-specific information on children who are in foster care and adopted. This <span class="hlt">final</span> rule replaces existing Adoption and Foster Care Analysis and Reporting <span class="hlt">System</span> (AFCARS) regulations and the appendices to require title IV-E agencies to collect and report data to ACF on children in out-of-home care, and who exit out-of-home care to adoption or legal guardianship, children in out-of-home care who are covered by the Indian Child Welfare Act, and children who are covered by a title IV-E adoption or guardianship assistance agreement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6390D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6390D"><span>Initiation and development of the Kivu <span class="hlt">rift</span> segment in Central Africa by reactivating un-favorably oriented structural weaknesses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Delvaux, Damien; Smets, Benoît</p> <p>2015-04-01</p> <p>The Kivu <span class="hlt">rift</span> region forms the central segment of the western branch of the East African <span class="hlt">rift</span> <span class="hlt">system</span>, between the northern termination of the Tanganyika <span class="hlt">rift</span> and the southern extension of the Edward-George <span class="hlt">rift</span>. Its structure and geological evolution has been revised in the light of a compilation of existing data on earthquake epicenters, focal depth, focal mechanisms, thermal springs and neotectonic faults. It has long been shown that the link between the Kivu <span class="hlt">rift</span> basin and the Northern termination of the Tanganyika <span class="hlt">rift</span> basin forms an accommodation zone in which the Rusizi tectonic depression occupies a central place (Ebinger, 1989). In addition, our compilation suggests that the NNE-trending Kivu <span class="hlt">rift</span> basin and the N-S northern half of the Tanganyika <span class="hlt">rift</span> basin initiated as separated, partly overlapping and differently oriented basins. The orientation and development of the Kivu <span class="hlt">rift</span> basin was controlled by an inferred Mid-Proterozoic crustal shear zone and a Pan-African reverse fault front. It was not optimally oriented with the general (first-order) stress field characterized by roughly E-W extension. In a later stage, the more optimally N-S oriented North Tanganyika basin progressed towards the North and connected to Kivu <span class="hlt">rift</span> in its middle in a region now occupied by the town of Bukavu. This accommodation zone is marked by Quaternary volcanism, warm thermal springs, frequent and relatively shallow seismicity. The southwestern part of the Kivu <span class="hlt">rift</span> became progressively abandoned but it is still seismically active and hosts a number of warm thermal springs. This particular architecture influences the present-day stress field. This work is a contribution to the Belgian GeoRisCA project. Ebinger, C.J. 1989. Geometric and kinematic development of border faults and accommodation zones, Kivu-Rusizi <span class="hlt">Rift</span>, Africa. Tectonics, 8, 117-133</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.4244Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.4244Z"><span>How oblique extension and structural inheritance control <span class="hlt">rift</span> segment linkage: Insights from 4D analogue models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zwaan, Frank; Schreurs, Guido</p> <p>2016-04-01</p> <p>INTRODUCTION During the early stages of <span class="hlt">rifting</span>, <span class="hlt">rift</span> segments may form along non-continuous and/or offset pre-existing weaknesses. It is important to understand how these initial <span class="hlt">rift</span> segments interact and connect to form a continuous <span class="hlt">rift</span> <span class="hlt">system</span>. A previous study of ours (Zwaan et al., in prep) investigated the influence of dextral oblique extension and <span class="hlt">rift</span> offset on <span class="hlt">rift</span> interaction. Here we elaborate upon our previous work by using analogue models to assess the added effects of 1) sinistral oblique extension as observed along the East African <span class="hlt">Rift</span> and 2) the geometry of linked and non-linked inherited structures. METHODS Our set-up involves a base of foam and plexiglass that forces distributed extension in the overlying model materials: a sand layer for the brittle upper crust and a viscous sand/silicone mixture for ductile lower crust. A mobile base plate allows lateral motion for oblique extension. We create inherited structures, along which <span class="hlt">rift</span> segments develop, with right-stepping offset lines of silicone (seeds) on top of the basal viscous layer. These seeds can be connected by an additional weak seed that represents a secondary inherited structural grain (model series 1) or disconnected and laterally discontinuous (over/underlap, model series 2). Selected models are run in an X-ray computer topographer (CT) to reveal the 3D evolution of internal structures with time that can be quantified with particle image velocitmetry (PIV) techniques. RESULTS Models in both series show that <span class="hlt">rift</span> segments initially form along the main seeds and then generally propagate approximately perpendicular to the extension direction: with orthogonal extension they propagate in a parallel fashion, dextral oblique extension causes them to grow towards each other and connect, while with sinistral oblique extension they grow away from each other. However, sinistral oblique extension can also promote <span class="hlt">rift</span> linkage through an oblique- or strike-slip zone oriented almost parallel to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/86606','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/86606"><span>Masirah Graben, Oman: A hidden Cretaceous <span class="hlt">rift</span> basin</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Beauchamp, W.H.; Ries, A.C.; Coward, M.P.</p> <p>1995-06-01</p> <p>Reflection seismic data, well data, geochemical data, and surface geology suggest that a Cretaceous <span class="hlt">rift</span> basin exists beneath the thrusted allochthonous sedimentary sequence of the Masirah graben, Oman. The Masirah graben is located east of the Huqf uplift, parallel to the southern coast of Oman. The eastern side of the northeast-trending Huqf anticlinorium is bounded by an extensional fault <span class="hlt">system</span> that is downthrown to the southeast, forming the western edge of the Masirah graben. This graben is limited to the east by a large wedge of sea floor sediments and oceanic crust, that is stacked as imbricate thrusts. These sediments/ophiolites were obducted onto the southern margin of the Arabian plate during the collision of the Indian/Afghan plates at the end of the Cretaceous. Most of the Masirah graben is covered by an allochthonous sedimentary sequence, which is complexly folded and deformed above a detachment. This complexly deformed sequence contrasts sharply with what is believed to be a <span class="hlt">rift</span> sequence below the ophiolites. The sedimentary sequence in the Masirah graben was stable until further <span class="hlt">rifting</span> of the Arabian Sea/Gulf of Aden in the late Tertiary, resulting in reactivation of earlier <span class="hlt">rift</span>-associated faults. Wells drilled in the Masirah graben in the south penetrated reservoir quality rocks in the Lower Cretaceous Natih and Shuaiba carbonates. Analyses of oil extracted from Infracambrian sedimentary rocks penetrated by these wells suggest an origin from a Mesozoic source rock.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2010/1083/p/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2010/1083/p/"><span>Seismicity of the Earth 1900-2013 East African <span class="hlt">Rift</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hayes, Gavin P.; Jones, Eric S.; Stadler, Timothy J.; Barnhart, William D.; McNamara, Daniel E.; Benz, Harley M.; Furlong, Kevin P.; Villaseñor, Antonio; Hayes, Gavin P.; Jones, Eric S.; Stadler, Timothy J.; Barnhart, William D.; McNamara, Daniel E.; Benz, Harley M.; Furlong, Kevin P.; Villaseñor, Antonio</p> <p>2014-01-01</p> <p><span class="hlt">Rifting</span> in East Africa is not all coeval; volcanism and faulting have been an ongoing phenomenon on the continent since the Eocene (~45 Ma). The <span class="hlt">rifting</span> began in northern East Africa, and led to the separation of the Nubia (Africa) and Arabia plates in the Red Sea and Gulf of Aden, and in the Lake Turkana area at the Kenya-Ethiopia border. A Paleogene mantle superplume beneath East Africa caused extension within the Nubia plate, as well as a first order topographic high known as the African superswell which now includes most of the eastern and southern sectors of the Nubia plate. Widespread volcanism erupted onto much of the rising plateau in Ethiopia during the Eocene-Oligocene (45–29 Ma), with chains of volcanoes forming along the <span class="hlt">rift</span> separating Africa and Arabia. Since the initiation of <span class="hlt">rifting</span> in northeastern Africa, the <span class="hlt">system</span> has propagated over 3,000 km to the south and southwest, and it experiences seismicity as a direct result of the extension and active magmatism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.T41A0378F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.T41A0378F"><span>Geological and Tectonic Evidence for the Formation and Extensional Collapse of the West Antarctic Plateau: Implications for the Formation of the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> and the Transantarctic Mountains</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fitzgerald, P. G.; Studinger, M.; Bialas, R. W.; Buck, W.</p> <p>2007-12-01</p> <p>The Transantarctic Mountains (TAM), the world's longest and highest non-contractional intracontinental mountain belt, define the western boundary of the West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span> (WARS). The WARS is a broad region of extended continental lithosphere, ca. 750-1000 km wide, lying dominantly below sea-level. A new model (Bialas et al., 2007), proposes that a region of thickened continental crust and high-standing topography, the "West Antarctic Plateau", underwent extensional collapse to leave a remnant edge representing the proto-TAM. Tectonic and paleogeographic reconstructions indicate the plateau formed inboard of a continental arc along the paleo- Pacific margin of Antarctica, active throughout the Paleozoic until the late Mesozoic. This high-standing region was responsible for confining sediments (Beacon Supergroup) to elongate basins along the length of the TAM. Much of the present region of the WARS has been correlated with the Lachlan Fold belt of southeastern Australia. This belt formed from the Ordovician to Carboniferous during back-arc basin formation associated with slab roll- back with short periods of compression. Convergence along the paleo-Pacific margin, perhaps enhanced by subduction of more buoyant oceanic lithosphere as the Phoenix-Pacific ridge was obliquely subducted, resulted in crustal thickening and formation of high-standing terrain (the plateau). Extensional collapse of the plateau most likely began in the Jurassic during initial <span class="hlt">rifting</span> between East and West Antarctica, but was mainly accomplished during distributed <span class="hlt">rifting</span> in the Cretaceous (ca. 105-85) following subduction of the Phoenix-Pacific ridge and prior to the separation of New Zealand from Marie Byrd Land. Continued formation of the TAM continued in the Cenozoic concomitant with extension in the WARS that was localized along its western margin adjacent to the TAM. Glacial erosion in the Oligocene and early-Miocene enhanced peak height in the TAM. In this presentation we</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGeo..102...24E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGeo..102...24E"><span>Modeling along-axis variations in fault architecture in the Main Ethiopian <span class="hlt">Rift</span>: Implications for Nubia-Somalia kinematics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Erbello, Asfaw; Corti, Giacomo; Agostini, Andrea; Sani, Federico; Kidane, Tesfaye; Buccianti, Antonella</p> <p>2016-12-01</p> <p>In this contribution, analogue modeling is used to provide new insights into the Nubia-Somalia kinematics responsible for development and evolution of the Main Ethiopian <span class="hlt">Rift</span> (MER), at the northern termination of the East African <span class="hlt">Rift</span> <span class="hlt">system</span>. In particular, we performed new crustal-scale, brittle models to analyze the along-strike variations in fault architecture in the MER and their relations with the <span class="hlt">rift</span> trend, plate motion and the resulting Miocene-recent kinematics of <span class="hlt">rifting</span>. The models reproduced the overall geometry of the ∼600 km-long MER with its along-strike variation in orientation to test different hypothesis proposed to explain <span class="hlt">rift</span> evolution. Analysis of model results in terms of statistics of fault length and orientation, as well as deformation architecture, and its comparison with the MER suggest that models of two-phase <span class="hlt">rifting</span> (with a first phase of NW-SE extension followed by E-W <span class="hlt">rifting</span>) or constant NW-SE extension, as well as models of constant ENE-WSW <span class="hlt">rifting</span> are not able to reproduce the fault architecture observed in nature. Model results suggest instead that the <span class="hlt">rift</span> has likely developed under a constant, post-11 Ma extension oriented roughly ESE-WNW (N97.5°E), consistent with recent plate kinematics models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C21B0743J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C21B0743J"><span><span class="hlt">Rifting</span> and Calving Event in 2015 at Pine Island Glacier, West Antarctica, Associated with Frontal and Basal processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jeong, S.; Howat, I. M.; Bassis, J. N.</p> <p>2015-12-01</p> <p>Calving is a process that glacier loses its mass by full-thickness penetration of crevasses (i.e. <span class="hlt">rifting</span>), followed by separation of iceberg from the terminus. Pine Island Glacier (PIG) in West Antarctica has undergone several major calving events including those in 2001, 2007 and 2013. All of them have started from <span class="hlt">rifting</span> at its shear margin, growing toward the center of the ice shelf, and <span class="hlt">finally</span> reaching the margin at the other end. However, recent observation of PIG from remote sensing data affirms unprecedented pattern of <span class="hlt">rifting</span>, that the <span class="hlt">rifts</span> start to grow at the center of the ice shelf and expanding to the each ends of the shear margin. Moreover, this evolution was accompanied with incessant disintegration of ice melange (mixture of small icebergs and sea ice) filling the shear margin around the terminus. We found from Landsat 8 images that those <span class="hlt">rifts</span> start from the troughs transverse to the ice shelf, which are surface features of basal crevasses (i.e. cracks at the bottom of ice shelf). We also analyzed velocity fields of PIG's flow and confirmed that its change is consistent with the <span class="hlt">rifting</span> and melange loss. We postulate this <span class="hlt">rifting</span> event attributes to the associated effects of reduced resistant force by melange disintegration, and expedited erosion of basal crevasses that causes the tensile stress to concentrate. As both of them are closely related to ocean forcing, we also hypothesize that warmer ocean current under the ice shelf has triggered this new mode of <span class="hlt">rifting</span> and calving event.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Tecto..34..464K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Tecto..34..464K"><span>The origin of along-<span class="hlt">rift</span> variations in faulting and magmatism in the Ethiopian <span class="hlt">Rift</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Keir, Derek; Bastow, Ian D.; Corti, Giacomo; Mazzarini, Francesco; Rooney, Tyrone O.</p> <p>2015-03-01</p> <p>The geological record at <span class="hlt">rifts</span> and margins worldwide often reveals considerable along-strike variations in volumes of extruded and intruded igneous rocks. These variations may be the result of asthenospheric heterogeneity, variations in rate, and timing of extension; alternatively, preexisting plate architecture and/or the evolving kinematics of extension during breakup may exert first-order control on magmatism. The Main Ethiopian <span class="hlt">Rift</span> (MER) in East Africa provides an excellent opportunity to address this dichotomy: it exposes, along strike, several sectors of asynchronous <span class="hlt">rift</span> development from continental <span class="hlt">rifting</span> in the south to incipient oceanic spreading in the north. Here we perform studies of volcanic cone density and <span class="hlt">rift</span> obliquity along strike in the MER. By synthesizing these new data in light of existing geophysical, geochemical, and petrological constraints on magma generation and emplacement, we are able to discriminate between tectonic and mantle geodynamic controls on the geological record of a newly forming magmatic <span class="hlt">rifted</span> margin. The timing of <span class="hlt">rift</span> sector development, the three-dimensional focusing of melt, and the ponding of plume material where the <span class="hlt">rift</span> dramatically narrows each influence igneous intrusion and volcanism along the MER. However, <span class="hlt">rifting</span> obliquity plays an important role in localizing intrusion into the crust beneath en echelon volcanic segments. Along-strike variations in volumes and types of igneous rocks found at <span class="hlt">rifted</span> margins thus likely carry information about the development of strain during <span class="hlt">rifting</span>, as well as the physical state of the convecting mantle at the time of breakup.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JAfES.100..203A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JAfES.100..203A"><span><span class="hlt">Rift</span> architecture and evolution: The Sirt Basin, Libya: The influence of basement fabrics and oblique tectonics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abdunaser, K. M.; McCaffrey, K. J. W.</p> <p>2014-12-01</p> <p>The Cretaceous-Tertiary northwest-trending Sirt Basin <span class="hlt">system</span>, Libya, is a <span class="hlt">rift</span>/sag basin formed on Pan-African to Paleozoic-aged basement of North Africa. In this study, we investigate the <span class="hlt">rift</span>-basin architecture and tectonic framework of the western Sirt Basin. Using remote sensed data, supported by borehole data from about 300 deep wells and surface geologic maps, we constructed geological cross sections and surface geology maps. Indication of the relative timing of structures and movement along faults has been determined where possible. Direction statistics for all the interpreted linear features acquired in the study area were calculated and given as a total distribution and then the totals are broken down by the major basin elements of the area. Hundreds of lineaments were recognized. Their lengths, range between a hundred meters up to hundreds of kilometers and the longest of the dominant trends are between N35W-N55W and between N55E-N65E which coincides with Sirt Basin structures. The produced rose diagrams reveal that the majority of the surface linear features in the region have four preferred orientations: N40-50W in the Zallah Trough, N45-55W in the Dur al Abd Trough, N35-55W in the Az Zahrah-Al Hufrah Platform, and in contrast in the Waddan Uplift a N55-65E trend. We recognize six lithostratigraphic sequences (phases) in the area's stratigraphic framework. A Pre-graben (Pre-<span class="hlt">rift</span>) initiation stage involved the Pre-Cretaceous sediments formed before the main Sirt Basin subsidence. Then followed a Cretaceous to Eocene graben-fill stage that can divided into four structurally-active and structurally-inactive periods, and <span class="hlt">finally</span> a terminal continental siliciclastics-rich package representing the post-<span class="hlt">rift</span> stage of the development in post-Eocene time. In general five major fault <span class="hlt">systems</span> dissect and divide the study area into geomorphological elevated blocks and depressions. Most of the oil fields present in the study area are associated with structural hinge</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/993614','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/993614"><span>Practical reliability and uncertainty quantification in complex <span class="hlt">systems</span> : <span class="hlt">final</span> report.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Grace, Matthew D.; Ringland, James T.; Marzouk, Youssef M.; Boggs, Paul T.; Zurn, Rena M.; Diegert, Kathleen V.; Pebay, Philippe Pierre; Red-Horse, John Robert</p> <p>2009-09-01</p> <p>The purpose of this project was to investigate the use of Bayesian methods for the estimation of the reliability of complex <span class="hlt">systems</span>. The goals were to find methods for dealing with continuous data, rather than simple pass/fail data; to avoid assumptions of specific probability distributions, especially Gaussian, or normal, distributions; to compute not only an estimate of the reliability of the <span class="hlt">system</span>, but also a measure of the confidence in that estimate; to develop procedures to address time-dependent or aging aspects in such <span class="hlt">systems</span>, and to use these models and results to derive optimal testing strategies. The <span class="hlt">system</span> is assumed to be a <span class="hlt">system</span> of <span class="hlt">systems</span>, i.e., a <span class="hlt">system</span> with discrete components that are themselves <span class="hlt">systems</span>. Furthermore, the <span class="hlt">system</span> is 'engineered' in the sense that each node is designed to do something and that we have a mathematical description of that process. In the time-dependent case, the assumption is that we have a general, nonlinear, time-dependent function describing the process. The major results of the project are described in this report. In summary, we developed a sophisticated mathematical framework based on modern probability theory and Bayesian analysis. This framework encompasses all aspects of epistemic uncertainty and easily incorporates steady-state and time-dependent <span class="hlt">systems</span>. Based on Markov chain, Monte Carlo methods, we devised a computational strategy for general probability density estimation in the steady-state case. This enabled us to compute a distribution of the reliability from which many questions, including confidence, could be addressed. We then extended this to the time domain and implemented procedures to estimate the reliability over time, including the use of the method to predict the reliability at a future time. <span class="hlt">Finally</span>, we used certain aspects of Bayesian decision analysis to create a novel method for determining an optimal testing strategy, e.g., we can estimate the 'best' location to take the next test to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3840870','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3840870"><span><span class="hlt">Rift</span> Valley Fever in Namibia, 2010</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Monaco, Federica; Pinoni, Chiara; Khaiseb, Siegfried; Calistri, Paolo; Molini, Umberto; Bishi, Alec; Conte, Annamaria; Scacchia, Massimo; Lelli, Rossella</p> <p>2013-01-01</p> <p>During May–July 2010 in Namibia, outbreaks of <span class="hlt">Rift</span> Valley fever were reported to the National Veterinary Service. Analysis of animal specimens confirmed virus circulation on 7 farms. Molecular characterization showed that all outbreaks were caused by a strain of <span class="hlt">Rift</span> Valley fever virus closely related to virus strains responsible for outbreaks in South Africa during 2009–2010. PMID:24274469</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6536182','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6536182"><span>Rio Grande <span class="hlt">rift</span>: problems and perspectives</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Baldridge, W.S.; Olsen, K.H.; Callender, J.F.</p> <p>1984-01-01</p> <p>Topics and ideas addressed include: (1) the regional extent of the Rio Grande <span class="hlt">rift</span>; (2) the structure of the crust and upper mantle; (3) whether the evidence for an axile dike in the lower crust is compelling; (4) the nature of faulting and extension in the crust; and (5) the structural and magmatic development of the <span class="hlt">rift</span>. 88 references, 5 figures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24447334','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24447334"><span><span class="hlt">Rift</span> Valley fever outbreak, southern Mauritania, 2012.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sow, Abdourahmane; Faye, Ousmane; Ba, Yamar; Ba, Hampathé; Diallo, Diawo; Faye, Oumar; Loucoubar, Cheikh; Boushab, Mohamed; Barry, Yahya; Diallo, Mawlouth; Sall, Amadou Alpha</p> <p>2014-02-01</p> <p>After a period of heavy rainfall, an outbreak of <span class="hlt">Rift</span> Valley fever occurred in southern Mauritania during September-November 2012. A total of 41 human cases were confirmed, including 13 deaths, and 12 <span class="hlt">Rift</span> Valley fever virus strains were isolated. Moudjeria and Temchecket Departments were the most affected areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24274469','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24274469"><span><span class="hlt">Rift</span> Valley fever in Namibia, 2010.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Monaco, Federica; Pinoni, Chiara; Cosseddu, Gian Mario; Khaiseb, Siegfried; Calistri, Paolo; Molini, Umberto; Bishi, Alec; Conte, Annamaria; Scacchia, Massimo; Lelli, Rossella</p> <p>2013-12-01</p> <p>During May-July 2010 in Namibia, outbreaks of <span class="hlt">Rift</span> Valley fever were reported to the National Veterinary Service. Analysis of animal specimens confirmed virus circulation on 7 farms. Molecular characterization showed that all outbreaks were caused by a strain of <span class="hlt">Rift</span> Valley fever virus closely related to virus strains responsible for outbreaks in South Africa during 2009-2010.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=315824','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=315824"><span>Detection and Response for <span class="hlt">Rift</span> Valley fever</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p><span class="hlt">Rift</span> Valley fever is a viral disease that impacts domestic livestock and humans in Africa and the Middle East, and poses a threat to military operations in these areas. We describe a <span class="hlt">Rift</span> Valley fever Risk Monitoring website, and its ability to predict risk of disease temporally and spatially. We al...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.V11F..01B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.V11F..01B"><span>From IGY to IPY: Volcanism Associated With the West Antarctic <span class="hlt">Rift</span> <span class="hlt">System</span> Interpreted From Geophysical Observations, and Possible Effects on the Stability of the West Antarctic Ice Sheet (WAIS).</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Behrendt, J. C.</p> <p>2008-12-01</p> <p>Observations from a few oversnow and airborne magnetic profiles acquired over the West Antarctic Ice Sheet (WAIS) during the International Geophysical Year (1957-58) indicated numerous high amplitude, shallow source, magnetic anomalies over a very extensive area of the presently known West Antarctic <span class="hlt">rift</span> <span class="hlt">system</span>. Aeromagnetic surveys over the WAIS in the early 1960s and later combined with radar ice sounding in 1978- 79 defined an area >500,000 km2; these anomalies range from 100->1000 nT as observed ~1 km over the 2-3 km thick moving ice. Behrendt et al, (1962, 1964, 1994, and 2005) and Jankowski et al. (1983) interpreted these anomalies as indicating "volcanic centers." Detailed aeromagnetic and radar ice sounding surveys since 1993 have shown that >80% of these anomaly sources have been modified by the moving ice into which they were injected requiring a younger age than the WAIS (~25 Ma). Behrendt et al., (1994; 2007) conservatively estimated >1 x 106 km3 volume of volcanic sources to account for the area of the "volcanic center" anomalies and suggested the presence of a large igneous province (LIP) if this volume was intruded within a time interval of 1-10 Ma. Active volcanism at a few widely spaced exposures of alkaline volcanic rocks associated with the West Antarctic <span class="hlt">rift</span>, which extend in age to ~34 Ma in the WAIS area, and interpreted active subglacial volcanism revealed by aerogeophysical data (Blankenship et al., 1993; and Corr and Vaughan, 2008) have raised the question of possible volcanic effects on the regime of the WAIS. Vogel and Tulaczyk (2006) argued that subglacial volcanism may play a "crucial roll" in WAIS stability, but LeMasurier (2008) has discounted this as unlikely. In my presentation I will review the geophysical evidence acquired from the IGY to the IPY, and conclude that whether unlikely or not, future effects on the stability of the WAIS should not be ignored.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016RScI...87kD433B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016RScI...87kD433B"><span><span class="hlt">Final</span> design of thermal diagnostic <span class="hlt">system</span> in SPIDER ion source</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brombin, M.; Dalla Palma, M.; Pasqualotto, R.; Pomaro, N.</p> <p>2016-11-01</p> <p>The prototype radio frequency source of the ITER heating neutral beams will be first tested in SPIDER test facility to optimize H- production, cesium dynamics, and overall plasma characteristics. Several diagnostics will allow to fully characterise the beam in terms of uniformity and divergence and the source, besides supporting a safe and controlled operation. In particular, thermal measurements will be used for beam monitoring and <span class="hlt">system</span> protection. SPIDER will be instrumented with mineral insulated cable thermocouples, both on the grids, on other components of the beam source, and on the rear side of the beam dump water cooled elements. This paper deals with the <span class="hlt">final</span> design and the technical specification of the thermal sensor diagnostic for SPIDER. In particular the layout of the diagnostic, together with the sensors distribution in the different components, the cables routing and the conditioning and acquisition cubicles are described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5278708','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5278708"><span>Urban Integrated Industrial Cogeneration <span class="hlt">Systems</span> Analysis. Phase II <span class="hlt">final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1984-01-01</p> <p>Through the Urban Integrated Industrial Cogeneration <span class="hlt">Systems</span> Analysis (UIICSA), the City of Chicago embarked upon an ambitious effort to identify the measure the overall industrial cogeneration market in the city and to evaluate in detail the most promising market opportunities. This report discusses the background of the work completed during Phase II of the UIICSA and presents the results of economic feasibility studies conducted for three potential cogeneration sites in Chicago. Phase II focused on the feasibility of cogeneration at the three most promising sites: the Stockyards and Calumet industrial areas, and the Ford City commercial/industrial complex. Each feasibility case study considered the energy load requirements of the existing facilities at the site and the potential for attracting and serving new growth in the area. Alternative fuels and technologies, and ownership and financing options were also incorporated into the case studies. <span class="hlt">Finally</span>, site specific considerations such as development incentives, zoning and building code restrictions and environmental requirements were investigated.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JPhCS.779a2011S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JPhCS.779a2011S"><span>Collectivity in small <span class="hlt">systems</span>: Initial correlations or <span class="hlt">final</span> state flow?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schenke, Björn</p> <p>2017-01-01</p> <p>I review recent progress in understanding correlation measurements in small collision <span class="hlt">systems</span>, such as proton+lead and proton+proton collisions at the Large Hadron Collider (LHC) and proton+gold, deuteron+gold, and 3He+gold collisions at the Relativistic Heavy Ion Collider (RHIC). I discuss two distinct theoretical approaches to describing the experimental data on multi-particle correlations. The first attributes the origin of the measured correlations to strong <span class="hlt">final</span> state interactions, often described by hydrodynamics, the second employs the color glass condensate effective theory and is able to reproduce many features of the data from initial state effects only. I discuss how to distinguish which of the two sources of correlations dominates the experimental observables, and give an outlook on how to make progress on the theory side.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26189218','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26189218"><span>Health Resources Priority and Allocations <span class="hlt">System</span> (HRPAS). Interim <span class="hlt">final</span> rule.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p></p> <p>2015-07-17</p> <p>This interim <span class="hlt">final</span> rule establishes standards and procedures by which the U.S. Department of Health and Human Services (HHS) may require that certain contracts or orders that promote the national defense be given priority over other contracts or orders. This rule also sets new standards and procedures by which HHS may allocate materials, services, and facilities to promote the national defense. This rule will implement HHS's administration of priorities and allocations actions, and establish the Health Resources Priorities and Allocation <span class="hlt">System</span> (HRPAS). The HRPAS will cover health resources pursuant to the authority under Section 101(c) of the Defense Production Act as delegated to HHS by Executive Order 13603. Priorities authorities (and other authorities delegated to the Secretary in E.O. 13603, but not covered by this regulation) may be re-delegated by the Secretary. The Secretary retains the authority for allocations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T53A4666G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T53A4666G"><span><span class="hlt">Rifting</span> and Post-<span class="hlt">Rift</span> Reactivation of The Eastern Sardinian Margin (Western Tyrrhenian Back-Arc Basin) Evidenced by the Messinian Salinity Crisis Markers and Salt Tectonics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gaullier, V.; Chanier, F.; Vendeville, B.; Lymer, G.; Lofi, J.; Sage, F.; Maillard, A.; Thinon, I.</p> <p>2014-12-01</p> <p>The Eastern Sardinian margin formed during the opening of the Tyrrhenian Sea, a back-arc basin created by continental <span class="hlt">rifting</span> and oceanic spreading related to the eastward migrating Apennine subduction <span class="hlt">system</span> from middle Miocene to Pliocene times. We carried out the "METYSS" project aiming at better understanding the Miocene-Pliocene relationships between crustal tectonics and salt tectonics in this key-area, where <span class="hlt">rifting</span> is pro parte coeval with the Messinian Salinity Crisis (MSC, 5.96-5.33 Ma) and Messinian salt décollement creates thin-skinned tectonics. Thereby, we use the MSC seismic markers and the deformation of viscous salt and its brittle overburden as proxies to better delineate the timing of <span class="hlt">rifting</span> and post-<span class="hlt">rift</span> reactivation, and especially to quantifying vertical and horizontal movements. Our mapping of the Messinian Erosion Surface and of Messinian Upper and Mobile Units shows that a <span class="hlt">rifted</span> basin already existed by the Messinian times, revealing a major pre-MSC <span class="hlt">rifting</span> episode across the entire domain. Because salt tectonics can create fan-shaped geometries in sediments, syn-<span class="hlt">rift</span> deposits have to be carefully re-examined in order to decipher the effects of crustal tectonics (<span class="hlt">rifting</span>) and salt tectonics. Our data surprisingly showed that there are no clues for Messinian syn-<span class="hlt">rift</span> sediments along the East-Sardinia Basin and Cornaglia Terrace, hence no evidence for <span class="hlt">rifting</span> after Late Tortonian times. Nevertheless, widespread deformation occurred during the Pliocene and is attributed to post-<span class="hlt">rift</span> reactivation. Some Pliocene vertical movements have been evidenced by discovering localized gravity gliding of the salt and its Late Messinian (UU) and Early Pliocene overburden. To the South, crustal-scale southward tilting triggered along-strike gravity gliding of salt and cover recorded by upslope extension and downslope shortening. To the North, East of the Baronie Ridge, there was some post-salt crustal activity along a narrow N-S basement trough, bounded</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70034615','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70034615"><span>East Antarctic <span class="hlt">rifting</span> triggers uplift of the Gamburtsev Mountains</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ferraccioli, F.; Finn, Carol A.; Jordan, Tom A.; Bell, Robin E.; Anderson, Lester M.; Damaske, Detlef</p> <p>2011-01-01</p> <p>The Gamburtsev Subglacial Mountains are the least understood tectonic feature on Earth, because they are completely hidden beneath the East Antarctic Ice Sheet. Their high elevation and youthful Alpine topography, combined with their location on the East Antarctic craton, creates a paradox that has puzzled researchers since the mountains were discovered in 1958. The preservation of Alpine topography in the Gamburtsevs may reflect extremely low long-term erosion rates beneath the ice sheet, but the mountains’ origin remains problematic. Here we present the first comprehensive view of the crustal architecture and uplift mechanisms for the Gamburtsevs, derived from radar, gravity and magnetic data. The geophysical data define a 2,500-km-long <span class="hlt">rift</span> <span class="hlt">system</span> in East Antarctica surrounding the Gamburtsevs, and a thick crustal root beneath the range. We propose that the root formed during the Proterozoic assembly of interior East Antarctica (possibly about 1 Gyr ago), was preserved as in some old orogens and was rejuvenated during much later Permian (roughly 250 Myr ago) and Cretaceous (roughly 100 Myr ago) <span class="hlt">rifting</span>. Much like East Africa, the interior of East Antarctica is a mosaic of Precambrian provinces affected by <span class="hlt">rifting</span> processes. Our models show that the combination of <span class="hlt">rift</span>-flank uplift, root buoyancy and the isostatic response to fluvial and glacial erosion explains the high elevation and relief of the Gamburtsevs. The evolution of the Gamburtsevs demonstrates that <span class="hlt">rifting</span> and preserved orogenic roots can produce broad regions of high topography in continental interiors without significantly modifying the underlying Precambrian lithosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986JGR....91.3395M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986JGR....91.3395M"><span>Three-dimensional magnetic modeling of a propagating <span class="hlt">rift</span>, Galapagos 95°30‧W</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miller, Stephen P.; Hey, R. N.</p> <p>1986-03-01</p> <p>A combined Deep Tow and Seabeam investigation at 95°30'W on the Cocos-Nazca spreading center has revealed the crustal contact between the propagating <span class="hlt">rift</span> and the dying <span class="hlt">rift</span> <span class="hlt">systems</span>. The observed 27-km offset between the axes creates an ideal situation for the application of magnetic methods. The normally magnetized crust of the propagating <span class="hlt">rift</span> tip penetrates into older crust, which was created when the earth's main field was reversed. As the V-shaped structure of the <span class="hlt">rift</span> clearly violates the conventional two-dimensional assumptions, a full three-dimensional analysis is required. In addition, the distorting influence of over 1000 m bathymetric relief must be removed from the observed field. Inversions have been performed on the gridded representations of the observed magnetic field and bathymetry, working in the Fourier domain. The result is a gridded rock magnetization distribution. The inversion of the surface data covers a large area, 6000 km2, and demonstrates close agreement with magnetization amplitudes of rock samples at existing dredge sites. In general, the propagating <span class="hlt">rift</span> process appears to be much more orderly than the dying <span class="hlt">rift</span> process. The magnetic polarity transition widths are narrower, and the boundaries have fewer undulations than the dying <span class="hlt">rift</span>, which appears to be quite episodic in behavior. The average propagation rate is 52 mm/yr, compared to the average spreading half-rate of 29 mm/yr. The locations of the boundaries suggest that the acceleration to the normal spreading rate on the propagating <span class="hlt">rift</span> requires about 250,000 years. The inversion of the Deep Tow data, near the seafloor, provides a high-resolution definition of the location of the tip of the propagating <span class="hlt">rift</span>, at 2°38.1'N, 95°30.0'W.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T43H..07K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T43H..07K"><span>Consequences of <span class="hlt">Rift</span> Propagation for Spreading in Thick Oceanic Crust in Iceland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karson, J. A.</p> <p>2015-12-01</p> <p>Iceland has long been considered a natural laboratory for processes related to seafloor spreading, including propagating <span class="hlt">rifts</span>, migrating transforms and rotating microplates. The thick, hot, weak crust and subaerial processes of Iceland result in variations on the themes developed along more typical parts of the global MOR <span class="hlt">system</span>. Compared to most other parts of the MOR, Icelandic <span class="hlt">rift</span> zones and transform faults are wider and more complex. <span class="hlt">Rift</span> zones are defined by overlapping arrays of volcanic/tectonic spreading segments as much as 50 km wide. The most active <span class="hlt">rift</span> zones propagate N and S away from the Iceland hot spot causing migration of transform faults. A trail of crust deformed by bookshelf faulting forms in their wakes. Dead or dying transform strands are truncated along pseudofaults that define propagation rates close to the full spreading rate of ~20 mm/yr. Pseudofaults are blurred by spreading across wide <span class="hlt">rift</span> zones and laterally extensive subaerial lava flows. Propagation, with decreasing spreading toward the propagator tips causes rotation of crustal blocks on both sides of the active <span class="hlt">rift</span> zones. The blocks deform internally by the widespread reactivation of spreading-related faults and zones of weakness along dike margins. The sense of slip on these <span class="hlt">rift</span>-parallel strike-slip faults is inconsistent with transform-fault deformation. These various deformation features as well as subaxial subsidence that accommodate the thickening of the volcanic upper crustal units are probably confined to the brittle, seismogenic, upper 10 km of the crust. At least beneath the active <span class="hlt">rift</span> zones, the upper crust is probably decoupled from hot, mechanically weak middle and lower gabbroic crust resulting in a broad plate boundary zone between the diverging lithosphere plates. Similar processes may occur at other types of propagating spreading centers and magmatic <span class="hlt">rifts</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MsT..........2N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MsT..........2N"><span>Crustal and sub-continental lithospheric mantle decoupling beneath the Malawi <span class="hlt">Rift</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Njinju, Emmanuel Atem</p> <p></p> <p>We analyzed satellite gravity and aeromagnetic data using the two-dimensional (2D) power-density spectrum technique to investigate the lithospheric and thermal structure beneath the magma-starved Malawi <span class="hlt">Rift</span>, which forms the southern extension of the Western Branch of the East African <span class="hlt">Rift</span> <span class="hlt">System</span>. We observed: (1) lack of consistent pattern of crustal thinning and elevated heat flow along the surface expression of the <span class="hlt">rift</span>. Beneath the Rungwe Volcanic Province (RVP) in the north, the crustal thickness ranges between 40 and 45 km and varies between 35 and 40 km along the entire length of the <span class="hlt">rift</span>. (2) shallow lithosphere-asthenosphere boundary (LAB) elevated to ˜64 km beneath the entire length of the <span class="hlt">rift</span> and deeper than 100 km beneath the surrounding Precambrian terranes reaching in places ˜124 km. (3) localized zones of high heat flow (70-75 mWm-2) beneath the RVP, and the central and southern parts of the <span class="hlt">rift</span>. The central and southern thermal anomalies are due to the presence of uranium deposits in the Karoo sedimentary rocks. We interpret the crustal thickness heterogeneity to have been inherited from pre-existing lithospheric stretching, while strain during the extension of the Malawi <span class="hlt">Rift</span> is preferentially localized in the sub-continental lithospheric mantle (SCLM). Our interpretation is supported by 2D forward modeling of the gravity data showing uniform stretching of the SCLM by a factor of 1.5 to 1.8 beneath the entire length of the <span class="hlt">rift</span>. Our results indicate decoupling of the crust from the SCLM during the early stages of the development of the Malawi <span class="hlt">Rift</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986JGeo....5....1M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986JGeo....5....1M"><span>A magnetic investigation of a tectonic problem: The propagating <span class="hlt">rift</span>, Galapagos 95°30'W</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miller, Stephen P.; Hey, R. N.</p> <p>1986-02-01</p> <p>The propagation of an oceanic <span class="hlt">rift</span> is an important tectonic problem, with a bearing on the reorganization of plate motion and on the early opening of oceanic basins. At the propagating <span class="hlt">rift</span> at 95°30'W near the Galapagos Islands, we can use magnetic methods to determine the tectonic origin of a set of important sea floor features. The observed 27 km offset between the axes of the propagating <span class="hlt">rift</span> and the dying <span class="hlt">rift</span> presents us with an ideal situation, in which the oceanic crust created by the opposing <span class="hlt">systems</span> has been magnetized in opposite directions. The normally magnetized crust of the propagating <span class="hlt">rift</span> tip penetrates into older crust, which created when the earth's main field was reversed. A combined Deep Tow and Sea Beam investigation at 95°30'W on the Cocos-Nazca spreading center has revealed the crustal contact between the propagating <span class="hlt">rift</span> and the dying <span class="hlt">rift</span> <span class="hlt">systems</span>. The inherent magnetic labelling of the crust has been recovered by performing inversions on the gridded representations of the observed magnetic field and bathymetry, working in the Fourier domain. The result is a gridded rock magnetization distribution. The inversion of the surface data covers a large area, 6000 km 2, and demonstrates close agreement with magnetization amplitudes of rock samples at existing dredge sites. In general, the propagating <span class="hlt">rift</span> process appears to be much more orderly than the dying <span class="hlt">rift</span> process. The magnetic polarity transition widths are narrower, and the boundaries have fewer undulations than the dying <span class="hlt">rift</span>, which appears to be quite episodic in behavior. The average propagation rate is 52 mm/yr, compared to the average spreading half-rate of 29 mm/yr. The locations of the boundaries suggest that the acceleration to the normal spreading rate on the propagation <span class="hlt">rift</span> requires about 250, 00 years. The inversion of the Deep Tow data, near the sea floor, provides a high resolution definition of the tip of the propagation <span class="hlt">rift</span>, at 2°38.1t'N, 95°30.0'W.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/658132','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/658132"><span>Acoustic Resonance Spectroscopy (ARS) Munition Classification <span class="hlt">System</span> enhancements. <span class="hlt">Final</span> report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Vela, O.A.; Huggard, J.C.</p> <p>1997-09-18</p> <p>Acoustic Resonance Spectroscopy (ARS) is a non-destructive evaluation technology developed at the Los Alamos National Laboratory (LANL). This technology has resulted in three generations of instrumentation, funded by the Defense Special Weapons Agency (DSWA), specifically designed for field identification of chemical weapon (CW) munitions. Each generation of ARS instrumentation was developed with a specific user in mind. The ARS1OO was built for use by the U.N. Inspection Teams going into Iraq immediately after the Persian Gulf War. The ARS200 was built for use in the US-Russia Bilateral Chemical Weapons Treaty (the primary users for this <span class="hlt">system</span> are the US Onsite Inspection Agency (OSIA) and their Russian counterparts). The ARS300 was built with the requirements of the Organization for the Prohibition of Chemical Weapons (OPCW) in mind. Each successive <span class="hlt">system</span> is an improved version of the previous <span class="hlt">system</span> based on learning the weaknesses of each and, coincidentally, on the fact that more time was available to do a requirements analysis and the necessary engineering development. The ARS300 is at a level of development that warrants transferring the technology to a commercial vendor. Since LANL will supply the computer software to the selected vendor, it is possible for LANL to continue to improve the decision algorithms, add features where necessary, and adjust the user interface before the <span class="hlt">final</span> transfer occurs. This paper describes the current <span class="hlt">system</span>, ARS <span class="hlt">system</span> enhancements, and software enhancements. Appendices contain the Operations Manual (software Version 3.01), and two earlier reports on enhancements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JSG....94..136S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JSG....94..136S"><span><span class="hlt">Rift</span> brittle deformation of SE-Brazilian continental margin: Kinematic analysis of onshore structures relative to the transfer and accommodation zones of southern Campos Basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Savastano, Vítor Lamy Mesiano; Schmitt, Renata da Silva; Araújo, Mário Neto Cavalcanti de; Inocêncio, Leonardo Campos</p> <p>2017-01-01</p> <p>High-resolution drone-supported mapping and traditional field work were used to refine the hierarchy and kinematics of <span class="hlt">rift</span>-related faults in the basement rocks and Early Cretaceous mafic dikes onshore of the Campos Basin, SE-Brazil. Two sets of structures were identified. The most significant fault set is NE-SW oriented with predominantly normal displacement. At mesoscale, this fault set is arranged in a rhombic pattern, interpreted here as a breached relay ramp <span class="hlt">system</span>. The rhombic pattern is a penetrative fabric from the thin-section to regional scale. The second-order set of structures is an E-W/ESE-WNW <span class="hlt">system</span> of normal faults with sinistral component. These E-W structures are oriented parallel with regional intrabasinal transfer zones associated with the earliest stages of Campos Basin's <span class="hlt">rift</span> <span class="hlt">system</span>. The crosscutting relationship between the two fault sets and tholeiitic dikes implies that the NE-SW fault set is the older feature, but remained active until the <span class="hlt">final</span> stages of <span class="hlt">rifting</span> in this region as the second-order fault set is older than the tholeiitic dikes. Paleostresses estimated from fault slip inversion method indicated that extension was originally NW-SE, with formation of the E-W transfer, followed by ESE-WNW oblique opening associated with a relay ramp <span class="hlt">system</span> and related accommodation zones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010IJEaS..99.1663B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010IJEaS..99.1663B"><span>Stable isotope variation in tooth enamel from Neogene hippopotamids: monitor of meso and global climate and <span class="hlt">rift</span> dynamics on the Albertine <span class="hlt">Rift</span>, Uganda</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brachert, Thomas Christian; Brügmann, Gerhard B.; Mertz, Dieter F.; Kullmer, Ottmar; Schrenk, Friedemann; Jacob, Dorrit E.; Ssemmanda, Immaculate; Taubald, Heinrich</p> <p>2010-10-01</p> <p>The Neogene was a period of long-term global cooling and increasing climatic variability. Variations in African-Asian monsoon intensity over the last 7 Ma have been deduced from patterns of eolian dust export into the Indian Ocean and Mediterranean Sea as well as from lake level records in the East African <span class="hlt">Rift</span> <span class="hlt">System</span> (EARS). However, lake <span class="hlt">systems</span> not only depend on rainfall patterns, but also on the size and physiography of river catchment areas. This study is based on stable isotope proxy data (18O/16O, 13C/12C) from tooth enamel of hippopotamids (Mammalia) and aims in unravelling long-term climate and watershed dynamics that control the evolution of palaeolake <span class="hlt">systems</span> in the western branch of the EARS (Lake Albert, Uganda) during the Late Neogene (7.5 Ma to recent). Having no dietary preferences with respect to wooded (C3) versus grassland (C4) vegetation, these territorial, water-dependant mammals are particularly useful for palaeoclimate analyses. As inhabitants of lakes and rivers, hippopotamid tooth enamel isotope data document mesoclimates of topographic depressions, such as the <span class="hlt">rift</span> valleys and, therefore, changes in relative valley depth instead of exclusively global climate changes. Consequently, we ascribe a synchronous maximum in 18O/16O and 13C/12C composition of hippopotamid enamel centred around 1.5-2.5 Ma to maximum aridity and/or maximum hydrological isolation of the <span class="hlt">rift</span> floor from <span class="hlt">rift</span>-external river catchment areas in response to the combined effects of <span class="hlt">rift</span> shoulder uplift and subsidence of the <span class="hlt">rift</span> valley floor. Structural rearrangements by ~2.5 Ma within the northern segment of the Albertine <span class="hlt">Rift</span> are well constrained by reversals in river flow, cannibalisation of catchments, biogeographic turnover and uplift of the Rwenzori horst. However, a growing rain shadow is not obvious in 18O/16O signatures of the hippopotamid teeth of the Albertine <span class="hlt">Rift</span>. According to our interpretation, this is the result of the overriding effect of evaporation on 18</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/840677','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/840677"><span>FY 93 Thermal Loading <span class="hlt">Systems</span> Study <span class="hlt">Final</span> Report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>S.F. Saterlie</p> <p>1994-08-29</p> <p>The objective of the Mined Geologic Disposal <span class="hlt">System</span> (MGDS) Thermal Loading <span class="hlt">Systems</span> Study being conducted by the is to identify a thermal strategy that will meet the performance requirements for waste isolation and will be safe and licensable. Specifically, both postclosure and preclosure performance standards must be met by the thermal loading strategy ultimately selected. In addition cost and schedule constraints must be considered. The <span class="hlt">Systems</span> Engineering approach requires structured, detailed analyses that will ultimately provide the technical basis for the development, integration, and evaluation of the overall <span class="hlt">system</span>, not just a subelement of that <span class="hlt">system</span>. It is also necessary that the <span class="hlt">systems</span> study construct options from within the range that are allowed within the current legislative and programmatic framework. For example the total amount of fuel that can legally be emplaced is no more than 70,000 metric tons of uranium (MTU) which is composed of 63,000 MTU spent fuel and 7,000 MTU of defense high level waste. It is the intent of this study to begin the structured development of the basis for a thermal loading decision. However, it is recognized that to be able to make a <span class="hlt">final</span> decision on thermal loading will require underground data on the effects of heating as well as a suite of ''validated'' models. It will be some time before these data and models are available to the program. Developing a <span class="hlt">final</span>, thermal loading decision will, therefore, be an iterative process. In the interim, the objective of the thermal loading <span class="hlt">systems</span> study has been to utilize the information available to assess the impact of thermal loading. Where technical justification exists, recommendations to narrow the range of thermal loading options can be made. Additionally, recommendations as to the type of testing and accuracy of the testing needed to establish the requisite information will be made. A constraint on the ability of the study to select an option stems from the lack of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/753091','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/753091"><span>Commercial thermal distribution <span class="hlt">systems</span>, <span class="hlt">Final</span> report for CIEE/CEC</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Xu, Tengfang; Bechu, Olivier; Carrie, Remi; Dickerhoff, Darryl; Fisk, William; Franconi, Ellen; Kristiansen, Oyvind; Levinson, Ronnen; McWilliams, Jennifer; Wang, Duo; Modera, Mark; Webster, Tom; Ring, Erik; Zhang, Qiang; Huizenga, Charlie; Bauman, Fred; Arens, Ed</p> <p>1999-12-01</p> <p>According to the California Energy Commission (CEC 1998a), California commercial buildings account for 35% of statewide electricity consumption, and 16% of statewide gas consumption. Space conditioning accounts for roughly 16,000 GWh of electricity and 800 million therms of natural gas annually, and the vast majority of this space conditioning energy passes through thermal distribution <span class="hlt">systems</span> in these buildings. In addition, 8600 GWh per year is consumed by fans and pumps in commercial buildings, most of which is used to move the thermal energy through these <span class="hlt">systems</span>. Research work at Lawrence Berkeley National Laboratory (LBNL) has been ongoing over the past five years to investigate the energy efficiency of these thermal distribution <span class="hlt">systems</span>, and to explore possibilities for improving that energy efficiency. Based upon that work, annual savings estimates of 1 kWh/ft{sup 2} for light commercial buildings, and 1-2 kWh/ft{sup 2} in large commercial buildings have been developed for the particular aspects of thermal distribution <span class="hlt">system</span> performance being addressed by this project. Those savings estimates, combined with a distribution of the building stock based upon an extensive stock characterization study (Modera et al. 1999a), and technical penetration estimates, translate into statewide saving potentials of 2000 GWh/year and 75 million thermal/year, as well as an electricity peak reduction potential of 0.7 GW. The overall goal of this research program is to provide new technology and application knowledge that will allow the design, construction, and energy services industries to reduce the energy waste associated with thermal distribution <span class="hlt">systems</span> in California commercial buildings. The specific goals of the LBNL efforts over the past year were: (1) to advance the state of knowledge about <span class="hlt">system</span> performance and energy losses in commercial-building thermal distribution <span class="hlt">systems</span>; (2) to evaluate the potential of reducing thermal losses through duct sealing, duct</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.T51D..02R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.T51D..02R"><span>Middle Jurassic - Early Cretaceous <span class="hlt">rifting</span> on the Chortis Block in Honduras: Implications for proto-Caribbean opening (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rogers, R. D.; Emmet, P. A.</p> <p>2009-12-01</p> <p>Regional mapping integrated with facies analysis, age constraints and airborne geophysical data reveal WNW and NE trends of Middle Jurassic to Early Cretaceous basins which intersect in southeast Honduras that we interpret as the result of <span class="hlt">rifting</span> associated with the breakup of the Americas and opening of the proto-Caribbean seaway. The WNW-trending <span class="hlt">rift</span> is 250 km long by 90 km wide and defined by a basal 200 to 800 m thick sequence of Middle to Late Jurassic fluvial channel and overbank deposits overlain by transgressive clastic shelf strata. At least three sub-basins are apparent. Flanking the WNW trending <span class="hlt">rift</span> basins are fault bounded exposures of the pre-Jurassic continental basement of the Chortis block which is the source of the conglomeratic channel facies that delineate the axes of the <span class="hlt">rifts</span>. Cretaceous terrigenous strata mantle the exposed basement-cored <span class="hlt">rift</span> flanks. Lower Cretaceous clastic strata and shallow marine limestone strata are dominant along this trend indicating that post-<span class="hlt">rift</span> related subsidence continued through the Early Cretaceous. The <span class="hlt">rifts</span> coincide with a regional high in the total magnetic intensity data. We interpret these trends to reflect NNE-WSW extension active from the Middle Jurassic through Early Cretaceous. These <span class="hlt">rifts</span> were inverted during Late Cretaceous shortening oriented normal to the <span class="hlt">rift</span> axes. To the east and at a 120 degree angle to the WNW trending <span class="hlt">rift</span> is the 300 km long NE trending Guayape fault <span class="hlt">system</span> that forms the western shoulder of the Late Jurassic Agua Fria <span class="hlt">rift</span> basin filled by > 2 km thickness of clastic marine shelf and slope strata. This NE trending basin coincides with the eastern extent of the surface exposure of continental basement rocks and a northeast-trending fabric of the Jurassic (?) metasedimentary basement rocks. We have previously interpreted the eastern basin to be the Jurassic <span class="hlt">rifted</span> margin of the Chortis block with the Guayape originating as a normal fault <span class="hlt">system</span>. These two <span class="hlt">rifts</span> basin intersect</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15011571','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15011571"><span>Foundations for Improvements to Passive Detection <span class="hlt">Systems</span> - <span class="hlt">Final</span> Report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Labov, S E; Pleasance, L; Sokkappa, P; Craig, W; Chapline, G; Frank, M; Gronberg, J; Jernigan, J G; Johnson, S; Kammeraad, J; Lange, D; Meyer, A; Nelson, K; Pohl, B; Wright, D; Wurtz, R</p> <p>2004-10-07</p> <p>This project explores the scientific foundation and approach for improving passive detection <span class="hlt">systems</span> for plutonium and highly enriched uranium in real applications. Sources of gamma-ray radiation of interest were chosen to represent a range of national security threats, naturally occurring radioactive materials, industrial and medical radiation sources, and natural background radiation. The gamma-ray flux emerging from these sources, which include unclassified criticality experiment configurations as surrogates for nuclear weapons, were modeled in detail. The performance of several types of gamma-ray imaging <span class="hlt">systems</span> using Compton scattering were modeled and compared. A mechanism was created to model the combine sources and background emissions and have the simulated radiation ''scene'' impinge on a model of a detector. These modeling tools are now being used in various projects to optimize detector performance and model detector sensitivity in complex measuring environments. This study also developed several automated algorithms for isotope identification from gamma-ray spectra and compared these to each other and to algorithms already in use. Verification testing indicates that these alternative isotope identification algorithms produced less false positive and false negative results than the ''GADRAS'' algorithms currently in use. In addition to these algorithms that used binned spectra, a new approach to isotope identification using ''event mode'' analysis was developed. <span class="hlt">Finally</span>, a technique using muons to detect nuclear material was explored.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NIMPA.830..532K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NIMPA.830..532K"><span>Electron beam <span class="hlt">final</span> focus <span class="hlt">system</span> for Thomson scattering at ELBE</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Krämer, J. M.; Budde, M.; Bødker, F.; Irman, A.; Jochmann, A.; Kristensen, J. P.; Lehnert, U.; Michel, P.; Schramm, U.</p> <p>2016-09-01</p> <p>The design of an electron beam <span class="hlt">final</span> focus <span class="hlt">system</span> (FFS) aiming for high-flux laser-Thomson backscattering X-ray sources at ELBE is presented. A telescope <span class="hlt">system</span> consisting of four permanent magnet based quadrupoles was found to have significantly less chromatic aberrations than a quadrupole doublet or triplet as commonly used. Focusing properties like the position of the focal plane and the spot size are retained for electron beam energies between 20 and 30 MeV by adjusting the position of the quadrupoles individually on a motorized stage. The desired ultra-short electron bunches require an increased relative energy spread up to a few percent and, thus, second order chromatic effects must be taken into account. We also present the design and test results of the permanent magnet quadrupoles. Adjustable shunts allow for correction of the field strength and compensation of deviations in the permanent magnet material. For a beam emittance of 13 mm mrad, we predict focal spot sizes of about 40 μm (rms) and divergences of about 10 mrad using the FFS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.8935G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.8935G"><span>Interaction between an incipient <span class="hlt">rift</span> and a cratonic lithosphere : The North Tanzania <span class="hlt">Rift</span> seen from some seismic tools</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gautier, Stéphanie; Plasman, Matthieu; Tiberi, Christel; Lopez, Marie; Peyrat, Sophie; Perrot, Julie; Albaric, Julie; Déverchère, Jacques; Deschamps, Anne; Ebinger, Cindy; Roecker, Steven; Mulibo, Gabriel; Wambura, Richard Ferdinand; Muzuka, Alfred; Msabi, Michael; Gama, Remigius</p> <p>2016-04-01</p> <p>The North Tanzania part of the East African <span class="hlt">Rift</span> is the place of an incipient break up of the lithosphere. This continental <span class="hlt">rifting</span> happens on the edge of the Tanzanian craton, and their interaction leads to major changes in the surface deformation. The evolution of the <span class="hlt">rift</span> and its morphology is strongly linked to the inherited structures, particularly the Proterozoic belts and the craton itself. It is thus of prime interest to image the structure of the craton edges to fully understand its impact on the localisation of the current deformation at the surface. Since 2007 different multidisciplinary projects have taken place in this area to address this question. We present here a work based on a collaborative work between French, American and Tanzanian institutes that started in 2013. About 35 seismological stations were installed for 2 years in the Natron lake region, and 10 short period instruments were added for 9 months in the Manyara area to record local and telesismic events. We have analysed more than a hundred teleseismic events to compute the receiver function, and we <span class="hlt">finally</span> obtain a Moho map of the region as well as azimuthal distribution of converted phases. The stations located on the edge of the <span class="hlt">rift</span> and near the craton present a continuous evolution of their crustal pattern in the RF signal. Especially, we identify a clear phase at about 7s for those stations that corresponds to an interface separating a normal upper mantle from a very slow mantle at about 70 km depth. We first model those receiver functions to perfectly fit the signal, and more precisely the transverse component, which shows a strong and coherent pattern. Second, the local seismic network we have installed for 9 months in Manyara region advantageously completed the 2007 SEISMOTANZ network. In this part of the <span class="hlt">rift</span> the seismicity is deep (20-30 km) and clustered without any magmatism record at the surface, opposite to Natron area. We could then relocalize the deep seismicity observed</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770028469&hterms=Trachyte&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DTrachyte','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770028469&hterms=Trachyte&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DTrachyte"><span>The Sagatu Ridge dike swarm, Ethiopian <span class="hlt">rift</span> margin. [tectonic evolution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mohr, P. A.; Potter, E. C.</p> <p>1976-01-01</p> <p>A swarm of dikes forms the core of the Sagatu Ridge, a 70-km-long topographic feature elevated to more than 4000 m above sea level and 1500 m above the level of the Eastern (Somalian) plateau. The ridge trends NNE and lies about 50 km east of the northeasterly trending <span class="hlt">rift</span>-valley margin. Intrusion of the dikes and buildup of the flood-lava pile, largely hawaiitic but with trachyte preponderant in the <span class="hlt">final</span> stages, occurred during the late Pliocene-early Pleistocene and may have been contemporaneous with downwarping of the protorift trough to the west. The ensuing faulting that formed the present <span class="hlt">rift</span> margin, however, bypassed the ridge. The peculiar situation and orientation of the Sagatu Ridge, and its temporary existence as a line of crustal extension and voluminous magmatism, are considered related to a powerful structural control by a major line of Precambrian crustal weakness, well exposed further south. Transverse <span class="hlt">rift</span> structures of unknown type appear to have limited the development of the ridge to the north and south.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/211661','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/211661"><span>Expanded studies of linear collider <span class="hlt">final</span> focus <span class="hlt">systems</span> at the <span class="hlt">Final</span> Focus Test Beam</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tenenbaum, Peter Gregory</p> <p>1995-12-01</p> <p>In order to meet their luminosity goals, linear colliders operating in the center-of-mass energy range from 3,50 to 1,500 GeV will need to deliver beams which are as small as a few Manometers tall, with x:y aspect ratios as large as 100. The <span class="hlt">Final</span> Focus Test Beam (FFTB) is a prototype for the <span class="hlt">final</span> focus demanded by these colliders: its purpose is to provide demagnification equivalent to those in the future linear collider, which corresponds to a focused spot size in the FFTB of 1.7 microns (horizontal) by 60 manometers (vertical). In order to achieve the desired spot sizes, the FFTB beam optics must be tuned to eliminate aberrations and other errors, and to ensure that the optics conform to the desired <span class="hlt">final</span> conditions and the measured initial conditions of the beam. Using a combination of incoming-beam diagnostics. beam-based local diagnostics, and global tuning algorithms, the FFTB beam size has been reduced to a stable <span class="hlt">final</span> size of 1.7 microns by 70 manometers. In addition, the chromatic properties of the FFTB have been studied using two techniques and found to be acceptable. Descriptions of the hardware and techniques used in these studies are presented, along with results and suggestions for future research.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED216855.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED216855.pdf"><span>Dissemination of Continuing Education Materials Via Television Delivery <span class="hlt">Systems</span>. <span class="hlt">Final</span> Technical Report and <span class="hlt">Final</span> Report.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Munushian, Jack</p> <p></p> <p>In 1972, the University of Southern California School of Engineering established a 4-channel interactive instructional television network. It was designed to allow employees of participating industries to take regular university science and engineering courses and special continuing education courses at or near their work locations. <span class="hlt">Final</span> progress…</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row